| 1 | |
| 2 | package Tie::File; |
| 3 | require 5.005; |
| 4 | use Carp ':DEFAULT', 'confess'; |
| 5 | use POSIX 'SEEK_SET'; |
| 6 | use Fcntl 'O_CREAT', 'O_RDWR', 'LOCK_EX', 'LOCK_SH', 'O_WRONLY', 'O_RDONLY'; |
| 7 | sub O_ACCMODE () { O_RDONLY | O_RDWR | O_WRONLY } |
| 8 | |
| 9 | |
| 10 | $VERSION = "0.97"; |
| 11 | my $DEFAULT_MEMORY_SIZE = 1<<21; # 2 megabytes |
| 12 | my $DEFAULT_AUTODEFER_THRESHHOLD = 3; # 3 records |
| 13 | my $DEFAULT_AUTODEFER_FILELEN_THRESHHOLD = 65536; # 16 disk blocksful |
| 14 | |
| 15 | my %good_opt = map {$_ => 1, "-$_" => 1} |
| 16 | qw(memory dw_size mode recsep discipline |
| 17 | autodefer autochomp autodefer_threshhold concurrent); |
| 18 | |
| 19 | sub TIEARRAY { |
| 20 | if (@_ % 2 != 0) { |
| 21 | croak "usage: tie \@array, $_[0], filename, [option => value]..."; |
| 22 | } |
| 23 | my ($pack, $file, %opts) = @_; |
| 24 | |
| 25 | # transform '-foo' keys into 'foo' keys |
| 26 | for my $key (keys %opts) { |
| 27 | unless ($good_opt{$key}) { |
| 28 | croak("$pack: Unrecognized option '$key'\n"); |
| 29 | } |
| 30 | my $okey = $key; |
| 31 | if ($key =~ s/^-+//) { |
| 32 | $opts{$key} = delete $opts{$okey}; |
| 33 | } |
| 34 | } |
| 35 | |
| 36 | if ($opts{concurrent}) { |
| 37 | croak("$pack: concurrent access not supported yet\n"); |
| 38 | } |
| 39 | |
| 40 | unless (defined $opts{memory}) { |
| 41 | # default is the larger of the default cache size and the |
| 42 | # deferred-write buffer size (if specified) |
| 43 | $opts{memory} = $DEFAULT_MEMORY_SIZE; |
| 44 | $opts{memory} = $opts{dw_size} |
| 45 | if defined $opts{dw_size} && $opts{dw_size} > $DEFAULT_MEMORY_SIZE; |
| 46 | # Dora Winifred Read |
| 47 | } |
| 48 | $opts{dw_size} = $opts{memory} unless defined $opts{dw_size}; |
| 49 | if ($opts{dw_size} > $opts{memory}) { |
| 50 | croak("$pack: dw_size may not be larger than total memory allocation\n"); |
| 51 | } |
| 52 | # are we in deferred-write mode? |
| 53 | $opts{defer} = 0 unless defined $opts{defer}; |
| 54 | $opts{deferred} = {}; # no records are presently deferred |
| 55 | $opts{deferred_s} = 0; # count of total bytes in ->{deferred} |
| 56 | $opts{deferred_max} = -1; # empty |
| 57 | |
| 58 | # What's a good way to arrange that this class can be overridden? |
| 59 | $opts{cache} = Tie::File::Cache->new($opts{memory}); |
| 60 | |
| 61 | # autodeferment is enabled by default |
| 62 | $opts{autodefer} = 1 unless defined $opts{autodefer}; |
| 63 | $opts{autodeferring} = 0; # but is not initially active |
| 64 | $opts{ad_history} = []; |
| 65 | $opts{autodefer_threshhold} = $DEFAULT_AUTODEFER_THRESHHOLD |
| 66 | unless defined $opts{autodefer_threshhold}; |
| 67 | $opts{autodefer_filelen_threshhold} = $DEFAULT_AUTODEFER_FILELEN_THRESHHOLD |
| 68 | unless defined $opts{autodefer_filelen_threshhold}; |
| 69 | |
| 70 | $opts{offsets} = [0]; |
| 71 | $opts{filename} = $file; |
| 72 | unless (defined $opts{recsep}) { |
| 73 | $opts{recsep} = _default_recsep(); |
| 74 | } |
| 75 | $opts{recseplen} = length($opts{recsep}); |
| 76 | if ($opts{recseplen} == 0) { |
| 77 | croak "Empty record separator not supported by $pack"; |
| 78 | } |
| 79 | |
| 80 | $opts{autochomp} = 1 unless defined $opts{autochomp}; |
| 81 | |
| 82 | $opts{mode} = O_CREAT|O_RDWR unless defined $opts{mode}; |
| 83 | $opts{rdonly} = (($opts{mode} & O_ACCMODE) == O_RDONLY); |
| 84 | $opts{sawlastrec} = undef; |
| 85 | |
| 86 | my $fh; |
| 87 | |
| 88 | if (UNIVERSAL::isa($file, 'GLOB')) { |
| 89 | # We use 1 here on the theory that some systems |
| 90 | # may not indicate failure if we use 0. |
| 91 | # MSWin32 does not indicate failure with 0, but I don't know if |
| 92 | # it will indicate failure with 1 or not. |
| 93 | unless (seek $file, 1, SEEK_SET) { |
| 94 | croak "$pack: your filehandle does not appear to be seekable"; |
| 95 | } |
| 96 | seek $file, 0, SEEK_SET # put it back |
| 97 | $fh = $file; # setting binmode is the user's problem |
| 98 | } elsif (ref $file) { |
| 99 | croak "usage: tie \@array, $pack, filename, [option => value]..."; |
| 100 | } else { |
| 101 | # $fh = \do { local *FH }; # XXX this is buggy |
| 102 | if ($] < 5.006) { |
| 103 | # perl 5.005 and earlier don't autovivify filehandles |
| 104 | require Symbol; |
| 105 | $fh = Symbol::gensym(); |
| 106 | } |
| 107 | sysopen $fh, $file, $opts{mode}, 0666 or return; |
| 108 | binmode $fh; |
| 109 | ++$opts{ourfh}; |
| 110 | } |
| 111 | { my $ofh = select $fh; $| = 1; select $ofh } # autoflush on write |
| 112 | if (defined $opts{discipline} && $] >= 5.006) { |
| 113 | # This avoids a compile-time warning under 5.005 |
| 114 | eval 'binmode($fh, $opts{discipline})'; |
| 115 | croak $@ if $@ =~ /unknown discipline/i; |
| 116 | die if $@; |
| 117 | } |
| 118 | $opts{fh} = $fh; |
| 119 | |
| 120 | bless \%opts => $pack; |
| 121 | } |
| 122 | |
| 123 | sub FETCH { |
| 124 | my ($self, $n) = @_; |
| 125 | my $rec; |
| 126 | |
| 127 | # check the defer buffer |
| 128 | $rec = $self->{deferred}{$n} if exists $self->{deferred}{$n}; |
| 129 | $rec = $self->_fetch($n) unless defined $rec; |
| 130 | |
| 131 | # inlined _chomp1 |
| 132 | substr($rec, - $self->{recseplen}) = "" |
| 133 | if defined $rec && $self->{autochomp}; |
| 134 | $rec; |
| 135 | } |
| 136 | |
| 137 | # Chomp many records in-place; return nothing useful |
| 138 | sub _chomp { |
| 139 | my $self = shift; |
| 140 | return unless $self->{autochomp}; |
| 141 | if ($self->{autochomp}) { |
| 142 | for (@_) { |
| 143 | next unless defined; |
| 144 | substr($_, - $self->{recseplen}) = ""; |
| 145 | } |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | # Chomp one record in-place; return modified record |
| 150 | sub _chomp1 { |
| 151 | my ($self, $rec) = @_; |
| 152 | return $rec unless $self->{autochomp}; |
| 153 | return unless defined $rec; |
| 154 | substr($rec, - $self->{recseplen}) = ""; |
| 155 | $rec; |
| 156 | } |
| 157 | |
| 158 | sub _fetch { |
| 159 | my ($self, $n) = @_; |
| 160 | |
| 161 | # check the record cache |
| 162 | { my $cached = $self->{cache}->lookup($n); |
| 163 | return $cached if defined $cached; |
| 164 | } |
| 165 | |
| 166 | if ($#{$self->{offsets}} < $n) { |
| 167 | return if $self->{eof}; # request for record beyond end of file |
| 168 | my $o = $self->_fill_offsets_to($n); |
| 169 | # If it's still undefined, there is no such record, so return 'undef' |
| 170 | return unless defined $o; |
| 171 | } |
| 172 | |
| 173 | my $fh = $self->{FH}; |
| 174 | $self->_seek($n); # we can do this now that offsets is populated |
| 175 | my $rec = $self->_read_record; |
| 176 | |
| 177 | # If we happen to have just read the first record, check to see if |
| 178 | # the length of the record matches what 'tell' says. If not, Tie::File |
| 179 | # won't work, and should drop dead. |
| 180 | # |
| 181 | # if ($n == 0 && defined($rec) && tell($self->{fh}) != length($rec)) { |
| 182 | # if (defined $self->{discipline}) { |
| 183 | # croak "I/O discipline $self->{discipline} not supported"; |
| 184 | # } else { |
| 185 | # croak "File encoding not supported"; |
| 186 | # } |
| 187 | # } |
| 188 | |
| 189 | $self->{cache}->insert($n, $rec) if defined $rec && not $self->{flushing}; |
| 190 | $rec; |
| 191 | } |
| 192 | |
| 193 | sub STORE { |
| 194 | my ($self, $n, $rec) = @_; |
| 195 | die "STORE called from _check_integrity!" if $DIAGNOSTIC; |
| 196 | |
| 197 | $self->_fixrecs($rec); |
| 198 | |
| 199 | if ($self->{autodefer}) { |
| 200 | $self->_annotate_ad_history($n); |
| 201 | } |
| 202 | |
| 203 | return $self->_store_deferred($n, $rec) if $self->_is_deferring; |
| 204 | |
| 205 | |
| 206 | # We need this to decide whether the new record will fit |
| 207 | # It incidentally populates the offsets table |
| 208 | # Note we have to do this before we alter the cache |
| 209 | # 20020324 Wait, but this DOES alter the cache. TODO BUG? |
| 210 | my $oldrec = $self->_fetch($n); |
| 211 | |
| 212 | if (not defined $oldrec) { |
| 213 | # We're storing a record beyond the end of the file |
| 214 | $self->_extend_file_to($n+1); |
| 215 | $oldrec = $self->{recsep}; |
| 216 | } |
| 217 | # return if $oldrec eq $rec; # don't bother |
| 218 | my $len_diff = length($rec) - length($oldrec); |
| 219 | |
| 220 | # length($oldrec) here is not consistent with text mode TODO XXX BUG |
| 221 | $self->_mtwrite($rec, $self->{offsets}[$n], length($oldrec)); |
| 222 | $self->_oadjust([$n, 1, $rec]); |
| 223 | $self->{cache}->update($n, $rec); |
| 224 | } |
| 225 | |
| 226 | sub _store_deferred { |
| 227 | my ($self, $n, $rec) = @_; |
| 228 | $self->{cache}->remove($n); |
| 229 | my $old_deferred = $self->{deferred}{$n}; |
| 230 | |
| 231 | if (defined $self->{deferred_max} && $n > $self->{deferred_max}) { |
| 232 | $self->{deferred_max} = $n; |
| 233 | } |
| 234 | $self->{deferred}{$n} = $rec; |
| 235 | |
| 236 | my $len_diff = length($rec); |
| 237 | $len_diff -= length($old_deferred) if defined $old_deferred; |
| 238 | $self->{deferred_s} += $len_diff; |
| 239 | $self->{cache}->adj_limit(-$len_diff); |
| 240 | if ($self->{deferred_s} > $self->{dw_size}) { |
| 241 | $self->_flush; |
| 242 | } elsif ($self->_cache_too_full) { |
| 243 | $self->_cache_flush; |
| 244 | } |
| 245 | } |
| 246 | |
| 247 | # Remove a single record from the deferred-write buffer without writing it |
| 248 | # The record need not be present |
| 249 | sub _delete_deferred { |
| 250 | my ($self, $n) = @_; |
| 251 | my $rec = delete $self->{deferred}{$n}; |
| 252 | return unless defined $rec; |
| 253 | |
| 254 | if (defined $self->{deferred_max} |
| 255 | && $n == $self->{deferred_max}) { |
| 256 | undef $self->{deferred_max}; |
| 257 | } |
| 258 | |
| 259 | $self->{deferred_s} -= length $rec; |
| 260 | $self->{cache}->adj_limit(length $rec); |
| 261 | } |
| 262 | |
| 263 | sub FETCHSIZE { |
| 264 | my $self = shift; |
| 265 | my $n = $self->{eof} ? $#{$self->{offsets}} : $self->_fill_offsets; |
| 266 | |
| 267 | my $top_deferred = $self->_defer_max; |
| 268 | $n = $top_deferred+1 if defined $top_deferred && $n < $top_deferred+1; |
| 269 | $n; |
| 270 | } |
| 271 | |
| 272 | sub STORESIZE { |
| 273 | my ($self, $len) = @_; |
| 274 | |
| 275 | if ($self->{autodefer}) { |
| 276 | $self->_annotate_ad_history('STORESIZE'); |
| 277 | } |
| 278 | |
| 279 | my $olen = $self->FETCHSIZE; |
| 280 | return if $len == $olen; # Woo-hoo! |
| 281 | |
| 282 | # file gets longer |
| 283 | if ($len > $olen) { |
| 284 | if ($self->_is_deferring) { |
| 285 | for ($olen .. $len-1) { |
| 286 | $self->_store_deferred($_, $self->{recsep}); |
| 287 | } |
| 288 | } else { |
| 289 | $self->_extend_file_to($len); |
| 290 | } |
| 291 | return; |
| 292 | } |
| 293 | |
| 294 | # file gets shorter |
| 295 | if ($self->_is_deferring) { |
| 296 | # TODO maybe replace this with map-plus-assignment? |
| 297 | for (grep $_ >= $len, keys %{$self->{deferred}}) { |
| 298 | $self->_delete_deferred($_); |
| 299 | } |
| 300 | $self->{deferred_max} = $len-1; |
| 301 | } |
| 302 | |
| 303 | $self->_seek($len); |
| 304 | $self->_chop_file; |
| 305 | $#{$self->{offsets}} = $len; |
| 306 | # $self->{offsets}[0] = 0; # in case we just chopped this |
| 307 | |
| 308 | $self->{cache}->remove(grep $_ >= $len, $self->{cache}->ckeys); |
| 309 | } |
| 310 | |
| 311 | ### OPTIMIZE ME |
| 312 | ### It should not be necessary to do FETCHSIZE |
| 313 | ### Just seek to the end of the file. |
| 314 | sub PUSH { |
| 315 | my $self = shift; |
| 316 | $self->SPLICE($self->FETCHSIZE, scalar(@_), @_); |
| 317 | |
| 318 | # No need to return: |
| 319 | # $self->FETCHSIZE; # because av.c takes care of this for me |
| 320 | } |
| 321 | |
| 322 | sub POP { |
| 323 | my $self = shift; |
| 324 | my $size = $self->FETCHSIZE; |
| 325 | return if $size == 0; |
| 326 | # print STDERR "# POPPITY POP POP POP\n"; |
| 327 | scalar $self->SPLICE($size-1, 1); |
| 328 | } |
| 329 | |
| 330 | sub SHIFT { |
| 331 | my $self = shift; |
| 332 | scalar $self->SPLICE(0, 1); |
| 333 | } |
| 334 | |
| 335 | sub UNSHIFT { |
| 336 | my $self = shift; |
| 337 | $self->SPLICE(0, 0, @_); |
| 338 | # $self->FETCHSIZE; # av.c takes care of this for me |
| 339 | } |
| 340 | |
| 341 | sub CLEAR { |
| 342 | my $self = shift; |
| 343 | |
| 344 | if ($self->{autodefer}) { |
| 345 | $self->_annotate_ad_history('CLEAR'); |
| 346 | } |
| 347 | |
| 348 | $self->_seekb(0); |
| 349 | $self->_chop_file; |
| 350 | $self->{cache}->set_limit($self->{memory}); |
| 351 | $self->{cache}->empty; |
| 352 | @{$self->{offsets}} = (0); |
| 353 | %{$self->{deferred}}= (); |
| 354 | $self->{deferred_s} = 0; |
| 355 | $self->{deferred_max} = -1; |
| 356 | } |
| 357 | |
| 358 | sub EXTEND { |
| 359 | my ($self, $n) = @_; |
| 360 | |
| 361 | # No need to pre-extend anything in this case |
| 362 | return if $self->_is_deferring; |
| 363 | |
| 364 | $self->_fill_offsets_to($n); |
| 365 | $self->_extend_file_to($n); |
| 366 | } |
| 367 | |
| 368 | sub DELETE { |
| 369 | my ($self, $n) = @_; |
| 370 | |
| 371 | if ($self->{autodefer}) { |
| 372 | $self->_annotate_ad_history('DELETE'); |
| 373 | } |
| 374 | |
| 375 | my $lastrec = $self->FETCHSIZE-1; |
| 376 | my $rec = $self->FETCH($n); |
| 377 | $self->_delete_deferred($n) if $self->_is_deferring; |
| 378 | if ($n == $lastrec) { |
| 379 | $self->_seek($n); |
| 380 | $self->_chop_file; |
| 381 | $#{$self->{offsets}}--; |
| 382 | $self->{cache}->remove($n); |
| 383 | # perhaps in this case I should also remove trailing null records? |
| 384 | # 20020316 |
| 385 | # Note that delete @a[-3..-1] deletes the records in the wrong order, |
| 386 | # so we only chop the very last one out of the file. We could repair this |
| 387 | # by tracking deleted records inside the object. |
| 388 | } elsif ($n < $lastrec) { |
| 389 | $self->STORE($n, ""); |
| 390 | } |
| 391 | $rec; |
| 392 | } |
| 393 | |
| 394 | sub EXISTS { |
| 395 | my ($self, $n) = @_; |
| 396 | return 1 if exists $self->{deferred}{$n}; |
| 397 | $n < $self->FETCHSIZE; |
| 398 | } |
| 399 | |
| 400 | sub SPLICE { |
| 401 | my $self = shift; |
| 402 | |
| 403 | if ($self->{autodefer}) { |
| 404 | $self->_annotate_ad_history('SPLICE'); |
| 405 | } |
| 406 | |
| 407 | $self->_flush if $self->_is_deferring; # move this up? |
| 408 | if (wantarray) { |
| 409 | $self->_chomp(my @a = $self->_splice(@_)); |
| 410 | @a; |
| 411 | } else { |
| 412 | $self->_chomp1(scalar $self->_splice(@_)); |
| 413 | } |
| 414 | } |
| 415 | |
| 416 | sub DESTROY { |
| 417 | my $self = shift; |
| 418 | $self->flush if $self->_is_deferring; |
| 419 | $self->{cache}->delink if defined $self->{cache}; # break circular link |
| 420 | if ($self->{fh} and $self->{ourfh}) { |
| 421 | delete $self->{ourfh}; |
| 422 | close delete $self->{fh}; |
| 423 | } |
| 424 | } |
| 425 | |
| 426 | sub _splice { |
| 427 | my ($self, $pos, $nrecs, @data) = @_; |
| 428 | my @result; |
| 429 | |
| 430 | $pos = 0 unless defined $pos; |
| 431 | |
| 432 | # Deal with negative and other out-of-range positions |
| 433 | # Also set default for $nrecs |
| 434 | { |
| 435 | my $oldsize = $self->FETCHSIZE; |
| 436 | $nrecs = $oldsize unless defined $nrecs; |
| 437 | my $oldpos = $pos; |
| 438 | |
| 439 | if ($pos < 0) { |
| 440 | $pos += $oldsize; |
| 441 | if ($pos < 0) { |
| 442 | croak "Modification of non-creatable array value attempted, subscript $oldpos"; |
| 443 | } |
| 444 | } |
| 445 | |
| 446 | if ($pos > $oldsize) { |
| 447 | return unless @data; |
| 448 | $pos = $oldsize; # This is what perl does for normal arrays |
| 449 | } |
| 450 | |
| 451 | # The manual is very unclear here |
| 452 | if ($nrecs < 0) { |
| 453 | $nrecs = $oldsize - $pos + $nrecs; |
| 454 | $nrecs = 0 if $nrecs < 0; |
| 455 | } |
| 456 | |
| 457 | # nrecs is too big---it really means "until the end" |
| 458 | # 20030507 |
| 459 | if ($nrecs + $pos > $oldsize) { |
| 460 | $nrecs = $oldsize - $pos; |
| 461 | } |
| 462 | } |
| 463 | |
| 464 | $self->_fixrecs(@data); |
| 465 | my $data = join '', @data; |
| 466 | my $datalen = length $data; |
| 467 | my $oldlen = 0; |
| 468 | |
| 469 | # compute length of data being removed |
| 470 | for ($pos .. $pos+$nrecs-1) { |
| 471 | last unless defined $self->_fill_offsets_to($_); |
| 472 | my $rec = $self->_fetch($_); |
| 473 | last unless defined $rec; |
| 474 | push @result, $rec; |
| 475 | |
| 476 | # Why don't we just use length($rec) here? |
| 477 | # Because that record might have come from the cache. _splice |
| 478 | # might have been called to flush out the deferred-write records, |
| 479 | # and in this case length($rec) is the length of the record to be |
| 480 | # *written*, not the length of the actual record in the file. But |
| 481 | # the offsets are still true. 20020322 |
| 482 | $oldlen += $self->{offsets}[$_+1] - $self->{offsets}[$_] |
| 483 | if defined $self->{offsets}[$_+1]; |
| 484 | } |
| 485 | $self->_fill_offsets_to($pos+$nrecs); |
| 486 | |
| 487 | # Modify the file |
| 488 | $self->_mtwrite($data, $self->{offsets}[$pos], $oldlen); |
| 489 | # Adjust the offsets table |
| 490 | $self->_oadjust([$pos, $nrecs, @data]); |
| 491 | |
| 492 | { # Take this read cache stuff out into a separate function |
| 493 | # You made a half-attempt to put it into _oadjust. |
| 494 | # Finish something like that up eventually. |
| 495 | # STORE also needs to do something similarish |
| 496 | |
| 497 | # update the read cache, part 1 |
| 498 | # modified records |
| 499 | for ($pos .. $pos+$nrecs-1) { |
| 500 | my $new = $data[$_-$pos]; |
| 501 | if (defined $new) { |
| 502 | $self->{cache}->update($_, $new); |
| 503 | } else { |
| 504 | $self->{cache}->remove($_); |
| 505 | } |
| 506 | } |
| 507 | |
| 508 | # update the read cache, part 2 |
| 509 | # moved records - records past the site of the change |
| 510 | # need to be renumbered |
| 511 | # Maybe merge this with the previous block? |
| 512 | { |
| 513 | my @oldkeys = grep $_ >= $pos + $nrecs, $self->{cache}->ckeys; |
| 514 | my @newkeys = map $_-$nrecs+@data, @oldkeys; |
| 515 | $self->{cache}->rekey(\@oldkeys, \@newkeys); |
| 516 | } |
| 517 | |
| 518 | # Now there might be too much data in the cache, if we spliced out |
| 519 | # some short records and spliced in some long ones. If so, flush |
| 520 | # the cache. |
| 521 | $self->_cache_flush; |
| 522 | } |
| 523 | |
| 524 | # Yes, the return value of 'splice' *is* actually this complicated |
| 525 | wantarray ? @result : @result ? $result[-1] : undef; |
| 526 | } |
| 527 | |
| 528 | |
| 529 | # write data into the file |
| 530 | # $data is the data to be written. |
| 531 | # it should be written at position $pos, and should overwrite |
| 532 | # exactly $len of the following bytes. |
| 533 | # Note that if length($data) > $len, the subsequent bytes will have to |
| 534 | # be moved up, and if length($data) < $len, they will have to |
| 535 | # be moved down |
| 536 | sub _twrite { |
| 537 | my ($self, $data, $pos, $len) = @_; |
| 538 | |
| 539 | unless (defined $pos) { |
| 540 | die "\$pos was undefined in _twrite"; |
| 541 | } |
| 542 | |
| 543 | my $len_diff = length($data) - $len; |
| 544 | |
| 545 | if ($len_diff == 0) { # Woo-hoo! |
| 546 | my $fh = $self->{fh}; |
| 547 | $self->_seekb($pos); |
| 548 | $self->_write_record($data); |
| 549 | return; # well, that was easy. |
| 550 | } |
| 551 | |
| 552 | # the two records are of different lengths |
| 553 | # our strategy here: rewrite the tail of the file, |
| 554 | # reading ahead one buffer at a time |
| 555 | # $bufsize is required to be at least as large as the data we're overwriting |
| 556 | my $bufsize = _bufsize($len_diff); |
| 557 | my ($writepos, $readpos) = ($pos, $pos+$len); |
| 558 | my $next_block; |
| 559 | my $more_data; |
| 560 | |
| 561 | # Seems like there ought to be a way to avoid the repeated code |
| 562 | # and the special case here. The read(1) is also a little weird. |
| 563 | # Think about this. |
| 564 | do { |
| 565 | $self->_seekb($readpos); |
| 566 | my $br = read $self->{fh}, $next_block, $bufsize; |
| 567 | $more_data = read $self->{fh}, my($dummy), 1; |
| 568 | $self->_seekb($writepos); |
| 569 | $self->_write_record($data); |
| 570 | $readpos += $br; |
| 571 | $writepos += length $data; |
| 572 | $data = $next_block; |
| 573 | } while $more_data; |
| 574 | $self->_seekb($writepos); |
| 575 | $self->_write_record($next_block); |
| 576 | |
| 577 | # There might be leftover data at the end of the file |
| 578 | $self->_chop_file if $len_diff < 0; |
| 579 | } |
| 580 | |
| 581 | # _iwrite(D, S, E) |
| 582 | # Insert text D at position S. |
| 583 | # Let C = E-S-|D|. If C < 0; die. |
| 584 | # Data in [S,S+C) is copied to [S+D,S+D+C) = [S+D,E). |
| 585 | # Data in [S+C = E-D, E) is returned. Data in [E, oo) is untouched. |
| 586 | # |
| 587 | # In a later version, don't read the entire intervening area into |
| 588 | # memory at once; do the copying block by block. |
| 589 | sub _iwrite { |
| 590 | my $self = shift; |
| 591 | my ($D, $s, $e) = @_; |
| 592 | my $d = length $D; |
| 593 | my $c = $e-$s-$d; |
| 594 | local *FH = $self->{fh}; |
| 595 | confess "Not enough space to insert $d bytes between $s and $e" |
| 596 | if $c < 0; |
| 597 | confess "[$s,$e) is an invalid insertion range" if $e < $s; |
| 598 | |
| 599 | $self->_seekb($s); |
| 600 | read FH, my $buf, $e-$s; |
| 601 | |
| 602 | $D .= substr($buf, 0, $c, ""); |
| 603 | |
| 604 | $self->_seekb($s); |
| 605 | $self->_write_record($D); |
| 606 | |
| 607 | return $buf; |
| 608 | } |
| 609 | |
| 610 | # Like _twrite, but the data-pos-len triple may be repeated; you may |
| 611 | # write several chunks. All the writing will be done in |
| 612 | # one pass. Chunks SHALL be in ascending order and SHALL NOT overlap. |
| 613 | sub _mtwrite { |
| 614 | my $self = shift; |
| 615 | my $unwritten = ""; |
| 616 | my $delta = 0; |
| 617 | |
| 618 | @_ % 3 == 0 |
| 619 | or die "Arguments to _mtwrite did not come in groups of three"; |
| 620 | |
| 621 | while (@_) { |
| 622 | my ($data, $pos, $len) = splice @_, 0, 3; |
| 623 | my $end = $pos + $len; # The OLD end of the segment to be replaced |
| 624 | $data = $unwritten . $data; |
| 625 | $delta -= length($unwritten); |
| 626 | $unwritten = ""; |
| 627 | $pos += $delta; # This is where the data goes now |
| 628 | my $dlen = length $data; |
| 629 | $self->_seekb($pos); |
| 630 | if ($len >= $dlen) { # the data will fit |
| 631 | $self->_write_record($data); |
| 632 | $delta += ($dlen - $len); # everything following moves down by this much |
| 633 | $data = ""; # All the data in the buffer has been written |
| 634 | } else { # won't fit |
| 635 | my $writable = substr($data, 0, $len - $delta, ""); |
| 636 | $self->_write_record($writable); |
| 637 | $delta += ($dlen - $len); # everything following moves down by this much |
| 638 | } |
| 639 | |
| 640 | # At this point we've written some but maybe not all of the data. |
| 641 | # There might be a gap to close up, or $data might still contain a |
| 642 | # bunch of unwritten data that didn't fit. |
| 643 | my $ndlen = length $data; |
| 644 | if ($delta == 0) { |
| 645 | $self->_write_record($data); |
| 646 | } elsif ($delta < 0) { |
| 647 | # upcopy (close up gap) |
| 648 | if (@_) { |
| 649 | $self->_upcopy($end, $end + $delta, $_[1] - $end); |
| 650 | } else { |
| 651 | $self->_upcopy($end, $end + $delta); |
| 652 | } |
| 653 | } else { |
| 654 | # downcopy (insert data that didn't fit; replace this data in memory |
| 655 | # with _later_ data that doesn't fit) |
| 656 | if (@_) { |
| 657 | $unwritten = $self->_downcopy($data, $end, $_[1] - $end); |
| 658 | } else { |
| 659 | # Make the file longer to accomodate the last segment that doesn' |
| 660 | $unwritten = $self->_downcopy($data, $end); |
| 661 | } |
| 662 | } |
| 663 | } |
| 664 | } |
| 665 | |
| 666 | # Copy block of data of length $len from position $spos to position $dpos |
| 667 | # $dpos must be <= $spos |
| 668 | # |
| 669 | # If $len is undefined, go all the way to the end of the file |
| 670 | # and then truncate it ($spos - $dpos bytes will be removed) |
| 671 | sub _upcopy { |
| 672 | my $blocksize = 8192; |
| 673 | my ($self, $spos, $dpos, $len) = @_; |
| 674 | if ($dpos > $spos) { |
| 675 | die "source ($spos) was upstream of destination ($dpos) in _upcopy"; |
| 676 | } elsif ($dpos == $spos) { |
| 677 | return; |
| 678 | } |
| 679 | |
| 680 | while (! defined ($len) || $len > 0) { |
| 681 | my $readsize = ! defined($len) ? $blocksize |
| 682 | : $len > $blocksize ? $blocksize |
| 683 | : $len; |
| 684 | |
| 685 | my $fh = $self->{fh}; |
| 686 | $self->_seekb($spos); |
| 687 | my $bytes_read = read $fh, my($data), $readsize; |
| 688 | $self->_seekb($dpos); |
| 689 | if ($data eq "") { |
| 690 | $self->_chop_file; |
| 691 | last; |
| 692 | } |
| 693 | $self->_write_record($data); |
| 694 | $spos += $bytes_read; |
| 695 | $dpos += $bytes_read; |
| 696 | $len -= $bytes_read if defined $len; |
| 697 | } |
| 698 | } |
| 699 | |
| 700 | # Write $data into a block of length $len at position $pos, |
| 701 | # moving everything in the block forwards to make room. |
| 702 | # Instead of writing the last length($data) bytes from the block |
| 703 | # (because there isn't room for them any longer) return them. |
| 704 | # |
| 705 | # Undefined $len means 'until the end of the file' |
| 706 | sub _downcopy { |
| 707 | my $blocksize = 8192; |
| 708 | my ($self, $data, $pos, $len) = @_; |
| 709 | my $fh = $self->{fh}; |
| 710 | |
| 711 | while (! defined $len || $len > 0) { |
| 712 | my $readsize = ! defined($len) ? $blocksize |
| 713 | : $len > $blocksize? $blocksize : $len; |
| 714 | $self->_seekb($pos); |
| 715 | read $fh, my($old), $readsize; |
| 716 | my $last_read_was_short = length($old) < $readsize; |
| 717 | $data .= $old; |
| 718 | my $writable; |
| 719 | if ($last_read_was_short) { |
| 720 | # If last read was short, then $data now contains the entire rest |
| 721 | # of the file, so there's no need to write only one block of it |
| 722 | $writable = $data; |
| 723 | $data = ""; |
| 724 | } else { |
| 725 | $writable = substr($data, 0, $readsize, ""); |
| 726 | } |
| 727 | last if $writable eq ""; |
| 728 | $self->_seekb($pos); |
| 729 | $self->_write_record($writable); |
| 730 | last if $last_read_was_short && $data eq ""; |
| 731 | $len -= $readsize if defined $len; |
| 732 | $pos += $readsize; |
| 733 | } |
| 734 | return $data; |
| 735 | } |
| 736 | |
| 737 | # Adjust the object data structures following an '_mtwrite' |
| 738 | # Arguments are |
| 739 | # [$pos, $nrecs, @length] items |
| 740 | # indicating that $nrecs records were removed at $recpos (a record offset) |
| 741 | # and replaced with records of length @length... |
| 742 | # Arguments guarantee that $recpos is strictly increasing. |
| 743 | # No return value |
| 744 | sub _oadjust { |
| 745 | my $self = shift; |
| 746 | my $delta = 0; |
| 747 | my $delta_recs = 0; |
| 748 | my $prev_end = -1; |
| 749 | my %newkeys; |
| 750 | |
| 751 | for (@_) { |
| 752 | my ($pos, $nrecs, @data) = @$_; |
| 753 | $pos += $delta_recs; |
| 754 | |
| 755 | # Adjust the offsets of the records after the previous batch up |
| 756 | # to the first new one of this batch |
| 757 | for my $i ($prev_end+2 .. $pos - 1) { |
| 758 | $self->{offsets}[$i] += $delta; |
| 759 | $newkey{$i} = $i + $delta_recs; |
| 760 | } |
| 761 | |
| 762 | $prev_end = $pos + @data - 1; # last record moved on this pass |
| 763 | |
| 764 | # Remove the offsets for the removed records; |
| 765 | # replace with the offsets for the inserted records |
| 766 | my @newoff = ($self->{offsets}[$pos] + $delta); |
| 767 | for my $i (0 .. $#data) { |
| 768 | my $newlen = length $data[$i]; |
| 769 | push @newoff, $newoff[$i] + $newlen; |
| 770 | $delta += $newlen; |
| 771 | } |
| 772 | |
| 773 | for my $i ($pos .. $pos+$nrecs-1) { |
| 774 | last if $i+1 > $#{$self->{offsets}}; |
| 775 | my $oldlen = $self->{offsets}[$i+1] - $self->{offsets}[$i]; |
| 776 | $delta -= $oldlen; |
| 777 | } |
| 778 | |
| 779 | # # also this data has changed, so update it in the cache |
| 780 | # for (0 .. $#data) { |
| 781 | # $self->{cache}->update($pos + $_, $data[$_]); |
| 782 | # } |
| 783 | # if ($delta_recs) { |
| 784 | # my @oldkeys = grep $_ >= $pos + @data, $self->{cache}->ckeys; |
| 785 | # my @newkeys = map $_ + $delta_recs, @oldkeys; |
| 786 | # $self->{cache}->rekey(\@oldkeys, \@newkeys); |
| 787 | # } |
| 788 | |
| 789 | # replace old offsets with new |
| 790 | splice @{$self->{offsets}}, $pos, $nrecs+1, @newoff; |
| 791 | # What if we just spliced out the end of the offsets table? |
| 792 | # shouldn't we clear $self->{eof}? Test for this XXX BUG TODO |
| 793 | |
| 794 | $delta_recs += @data - $nrecs; # net change in total number of records |
| 795 | } |
| 796 | |
| 797 | # The trailing records at the very end of the file |
| 798 | if ($delta) { |
| 799 | for my $i ($prev_end+2 .. $#{$self->{offsets}}) { |
| 800 | $self->{offsets}[$i] += $delta; |
| 801 | } |
| 802 | } |
| 803 | |
| 804 | # If we scrubbed out all known offsets, regenerate the trivial table |
| 805 | # that knows that the file does indeed start at 0. |
| 806 | $self->{offsets}[0] = 0 unless @{$self->{offsets}}; |
| 807 | # If the file got longer, the offsets table is no longer complete |
| 808 | # $self->{eof} = 0 if $delta_recs > 0; |
| 809 | |
| 810 | # Now there might be too much data in the cache, if we spliced out |
| 811 | # some short records and spliced in some long ones. If so, flush |
| 812 | # the cache. |
| 813 | $self->_cache_flush; |
| 814 | } |
| 815 | |
| 816 | # If a record does not already end with the appropriate terminator |
| 817 | # string, append one. |
| 818 | sub _fixrecs { |
| 819 | my $self = shift; |
| 820 | for (@_) { |
| 821 | $_ = "" unless defined $_; |
| 822 | $_ .= $self->{recsep} |
| 823 | unless substr($_, - $self->{recseplen}) eq $self->{recsep}; |
| 824 | } |
| 825 | } |
| 826 | |
| 827 | |
| 828 | ################################################################ |
| 829 | # |
| 830 | # Basic read, write, and seek |
| 831 | # |
| 832 | |
| 833 | # seek to the beginning of record #$n |
| 834 | # Assumes that the offsets table is already correctly populated |
| 835 | # |
| 836 | # Note that $n=-1 has a special meaning here: It means the start of |
| 837 | # the last known record; this may or may not be the very last record |
| 838 | # in the file, depending on whether the offsets table is fully populated. |
| 839 | # |
| 840 | sub _seek { |
| 841 | my ($self, $n) = @_; |
| 842 | my $o = $self->{offsets}[$n]; |
| 843 | defined($o) |
| 844 | or confess("logic error: undefined offset for record $n"); |
| 845 | seek $self->{fh}, $o, SEEK_SET |
| 846 | or confess "Couldn't seek filehandle: $!"; # "Should never happen." |
| 847 | } |
| 848 | |
| 849 | # seek to byte $b in the file |
| 850 | sub _seekb { |
| 851 | my ($self, $b) = @_; |
| 852 | seek $self->{fh}, $b, SEEK_SET |
| 853 | or die "Couldn't seek filehandle: $!"; # "Should never happen." |
| 854 | } |
| 855 | |
| 856 | # populate the offsets table up to the beginning of record $n |
| 857 | # return the offset of record $n |
| 858 | sub _fill_offsets_to { |
| 859 | my ($self, $n) = @_; |
| 860 | |
| 861 | return $self->{offsets}[$n] if $self->{eof}; |
| 862 | |
| 863 | my $fh = $self->{fh}; |
| 864 | local *OFF = $self->{offsets}; |
| 865 | my $rec; |
| 866 | |
| 867 | until ($#OFF >= $n) { |
| 868 | $self->_seek(-1); # tricky -- see comment at _seek |
| 869 | $rec = $self->_read_record; |
| 870 | if (defined $rec) { |
| 871 | push @OFF, int(tell $fh); # Tels says that int() saves memory here |
| 872 | } else { |
| 873 | $self->{eof} = 1; |
| 874 | return; # It turns out there is no such record |
| 875 | } |
| 876 | } |
| 877 | |
| 878 | # we have now read all the records up to record n-1, |
| 879 | # so we can return the offset of record n |
| 880 | $OFF[$n]; |
| 881 | } |
| 882 | |
| 883 | sub _fill_offsets { |
| 884 | my ($self) = @_; |
| 885 | |
| 886 | my $fh = $self->{fh}; |
| 887 | local *OFF = $self->{offsets}; |
| 888 | |
| 889 | $self->_seek(-1); # tricky -- see comment at _seek |
| 890 | |
| 891 | # Tels says that inlining read_record() would make this loop |
| 892 | # five times faster. 20030508 |
| 893 | while ( defined $self->_read_record()) { |
| 894 | # int() saves us memory here |
| 895 | push @OFF, int(tell $fh); |
| 896 | } |
| 897 | |
| 898 | $self->{eof} = 1; |
| 899 | $#OFF; |
| 900 | } |
| 901 | |
| 902 | # assumes that $rec is already suitably terminated |
| 903 | sub _write_record { |
| 904 | my ($self, $rec) = @_; |
| 905 | my $fh = $self->{fh}; |
| 906 | local $\ = ""; |
| 907 | print $fh $rec |
| 908 | or die "Couldn't write record: $!"; # "Should never happen." |
| 909 | # $self->{_written} += length($rec); |
| 910 | } |
| 911 | |
| 912 | sub _read_record { |
| 913 | my $self = shift; |
| 914 | my $rec; |
| 915 | { local $/ = $self->{recsep}; |
| 916 | my $fh = $self->{fh}; |
| 917 | $rec = <$fh>; |
| 918 | } |
| 919 | return unless defined $rec; |
| 920 | if (substr($rec, -$self->{recseplen}) ne $self->{recsep}) { |
| 921 | # improperly terminated final record --- quietly fix it. |
| 922 | # my $ac = substr($rec, -$self->{recseplen}); |
| 923 | # $ac =~ s/\n/\\n/g; |
| 924 | $self->{sawlastrec} = 1; |
| 925 | unless ($self->{rdonly}) { |
| 926 | local $\ = ""; |
| 927 | my $fh = $self->{fh}; |
| 928 | print $fh $self->{recsep}; |
| 929 | } |
| 930 | $rec .= $self->{recsep}; |
| 931 | } |
| 932 | # $self->{_read} += length($rec) if defined $rec; |
| 933 | $rec; |
| 934 | } |
| 935 | |
| 936 | sub _rw_stats { |
| 937 | my $self = shift; |
| 938 | @{$self}{'_read', '_written'}; |
| 939 | } |
| 940 | |
| 941 | ################################################################ |
| 942 | # |
| 943 | # Read cache management |
| 944 | |
| 945 | sub _cache_flush { |
| 946 | my ($self) = @_; |
| 947 | $self->{cache}->reduce_size_to($self->{memory} - $self->{deferred_s}); |
| 948 | } |
| 949 | |
| 950 | sub _cache_too_full { |
| 951 | my $self = shift; |
| 952 | $self->{cache}->bytes + $self->{deferred_s} >= $self->{memory}; |
| 953 | } |
| 954 | |
| 955 | ################################################################ |
| 956 | # |
| 957 | # File custodial services |
| 958 | # |
| 959 | |
| 960 | |
| 961 | # We have read to the end of the file and have the offsets table |
| 962 | # entirely populated. Now we need to write a new record beyond |
| 963 | # the end of the file. We prepare for this by writing |
| 964 | # empty records into the file up to the position we want |
| 965 | # |
| 966 | # assumes that the offsets table already contains the offset of record $n, |
| 967 | # if it exists, and extends to the end of the file if not. |
| 968 | sub _extend_file_to { |
| 969 | my ($self, $n) = @_; |
| 970 | $self->_seek(-1); # position after the end of the last record |
| 971 | my $pos = $self->{offsets}[-1]; |
| 972 | |
| 973 | # the offsets table has one entry more than the total number of records |
| 974 | my $extras = $n - $#{$self->{offsets}}; |
| 975 | |
| 976 | # Todo : just use $self->{recsep} x $extras here? |
| 977 | while ($extras-- > 0) { |
| 978 | $self->_write_record($self->{recsep}); |
| 979 | push @{$self->{offsets}}, int(tell $self->{fh}); |
| 980 | } |
| 981 | } |
| 982 | |
| 983 | # Truncate the file at the current position |
| 984 | sub _chop_file { |
| 985 | my $self = shift; |
| 986 | truncate $self->{fh}, tell($self->{fh}); |
| 987 | } |
| 988 | |
| 989 | |
| 990 | # compute the size of a buffer suitable for moving |
| 991 | # all the data in a file forward $n bytes |
| 992 | # ($n may be negative) |
| 993 | # The result should be at least $n. |
| 994 | sub _bufsize { |
| 995 | my $n = shift; |
| 996 | return 8192 if $n <= 0; |
| 997 | my $b = $n & ~8191; |
| 998 | $b += 8192 if $n & 8191; |
| 999 | $b; |
| 1000 | } |
| 1001 | |
| 1002 | ################################################################ |
| 1003 | # |
| 1004 | # Miscellaneous public methods |
| 1005 | # |
| 1006 | |
| 1007 | # Lock the file |
| 1008 | sub flock { |
| 1009 | my ($self, $op) = @_; |
| 1010 | unless (@_ <= 3) { |
| 1011 | my $pack = ref $self; |
| 1012 | croak "Usage: $pack\->flock([OPERATION])"; |
| 1013 | } |
| 1014 | my $fh = $self->{fh}; |
| 1015 | $op = LOCK_EX unless defined $op; |
| 1016 | my $locked = flock $fh, $op; |
| 1017 | |
| 1018 | if ($locked && ($op & (LOCK_EX | LOCK_SH))) { |
| 1019 | # If you're locking the file, then presumably it's because |
| 1020 | # there might have been a write access by another process. |
| 1021 | # In that case, the read cache contents and the offsets table |
| 1022 | # might be invalid, so discard them. 20030508 |
| 1023 | $self->{offsets} = [0]; |
| 1024 | $self->{cache}->empty; |
| 1025 | } |
| 1026 | |
| 1027 | $locked; |
| 1028 | } |
| 1029 | |
| 1030 | # Get/set autochomp option |
| 1031 | sub autochomp { |
| 1032 | my $self = shift; |
| 1033 | if (@_) { |
| 1034 | my $old = $self->{autochomp}; |
| 1035 | $self->{autochomp} = shift; |
| 1036 | $old; |
| 1037 | } else { |
| 1038 | $self->{autochomp}; |
| 1039 | } |
| 1040 | } |
| 1041 | |
| 1042 | # Get offset table entries; returns offset of nth record |
| 1043 | sub offset { |
| 1044 | my ($self, $n) = @_; |
| 1045 | |
| 1046 | if ($#{$self->{offsets}} < $n) { |
| 1047 | return if $self->{eof}; # request for record beyond the end of file |
| 1048 | my $o = $self->_fill_offsets_to($n); |
| 1049 | # If it's still undefined, there is no such record, so return 'undef' |
| 1050 | return unless defined $o; |
| 1051 | } |
| 1052 | |
| 1053 | $self->{offsets}[$n]; |
| 1054 | } |
| 1055 | |
| 1056 | sub discard_offsets { |
| 1057 | my $self = shift; |
| 1058 | $self->{offsets} = [0]; |
| 1059 | } |
| 1060 | |
| 1061 | ################################################################ |
| 1062 | # |
| 1063 | # Matters related to deferred writing |
| 1064 | # |
| 1065 | |
| 1066 | # Defer writes |
| 1067 | sub defer { |
| 1068 | my $self = shift; |
| 1069 | $self->_stop_autodeferring; |
| 1070 | @{$self->{ad_history}} = (); |
| 1071 | $self->{defer} = 1; |
| 1072 | } |
| 1073 | |
| 1074 | # Flush deferred writes |
| 1075 | # |
| 1076 | # This could be better optimized to write the file in one pass, instead |
| 1077 | # of one pass per block of records. But that will require modifications |
| 1078 | # to _twrite, so I should have a good _twrite test suite first. |
| 1079 | sub flush { |
| 1080 | my $self = shift; |
| 1081 | |
| 1082 | $self->_flush; |
| 1083 | $self->{defer} = 0; |
| 1084 | } |
| 1085 | |
| 1086 | sub _old_flush { |
| 1087 | my $self = shift; |
| 1088 | my @writable = sort {$a<=>$b} (keys %{$self->{deferred}}); |
| 1089 | |
| 1090 | while (@writable) { |
| 1091 | # gather all consecutive records from the front of @writable |
| 1092 | my $first_rec = shift @writable; |
| 1093 | my $last_rec = $first_rec+1; |
| 1094 | ++$last_rec, shift @writable while @writable && $last_rec == $writable[0]; |
| 1095 | --$last_rec; |
| 1096 | $self->_fill_offsets_to($last_rec); |
| 1097 | $self->_extend_file_to($last_rec); |
| 1098 | $self->_splice($first_rec, $last_rec-$first_rec+1, |
| 1099 | @{$self->{deferred}}{$first_rec .. $last_rec}); |
| 1100 | } |
| 1101 | |
| 1102 | $self->_discard; # clear out defered-write-cache |
| 1103 | } |
| 1104 | |
| 1105 | sub _flush { |
| 1106 | my $self = shift; |
| 1107 | my @writable = sort {$a<=>$b} (keys %{$self->{deferred}}); |
| 1108 | my @args; |
| 1109 | my @adjust; |
| 1110 | |
| 1111 | while (@writable) { |
| 1112 | # gather all consecutive records from the front of @writable |
| 1113 | my $first_rec = shift @writable; |
| 1114 | my $last_rec = $first_rec+1; |
| 1115 | ++$last_rec, shift @writable while @writable && $last_rec == $writable[0]; |
| 1116 | --$last_rec; |
| 1117 | my $end = $self->_fill_offsets_to($last_rec+1); |
| 1118 | if (not defined $end) { |
| 1119 | $self->_extend_file_to($last_rec); |
| 1120 | $end = $self->{offsets}[$last_rec]; |
| 1121 | } |
| 1122 | my ($start) = $self->{offsets}[$first_rec]; |
| 1123 | push @args, |
| 1124 | join("", @{$self->{deferred}}{$first_rec .. $last_rec}), # data |
| 1125 | $start, # position |
| 1126 | $end-$start; # length |
| 1127 | push @adjust, [$first_rec, # starting at this position... |
| 1128 | $last_rec-$first_rec+1, # this many records... |
| 1129 | # are replaced with these... |
| 1130 | @{$self->{deferred}}{$first_rec .. $last_rec}, |
| 1131 | ]; |
| 1132 | } |
| 1133 | |
| 1134 | $self->_mtwrite(@args); # write multiple record groups |
| 1135 | $self->_discard; # clear out defered-write-cache |
| 1136 | $self->_oadjust(@adjust); |
| 1137 | } |
| 1138 | |
| 1139 | # Discard deferred writes and disable future deferred writes |
| 1140 | sub discard { |
| 1141 | my $self = shift; |
| 1142 | $self->_discard; |
| 1143 | $self->{defer} = 0; |
| 1144 | } |
| 1145 | |
| 1146 | # Discard deferred writes, but retain old deferred writing mode |
| 1147 | sub _discard { |
| 1148 | my $self = shift; |
| 1149 | %{$self->{deferred}} = (); |
| 1150 | $self->{deferred_s} = 0; |
| 1151 | $self->{deferred_max} = -1; |
| 1152 | $self->{cache}->set_limit($self->{memory}); |
| 1153 | } |
| 1154 | |
| 1155 | # Deferred writing is enabled, either explicitly ($self->{defer}) |
| 1156 | # or automatically ($self->{autodeferring}) |
| 1157 | sub _is_deferring { |
| 1158 | my $self = shift; |
| 1159 | $self->{defer} || $self->{autodeferring}; |
| 1160 | } |
| 1161 | |
| 1162 | # The largest record number of any deferred record |
| 1163 | sub _defer_max { |
| 1164 | my $self = shift; |
| 1165 | return $self->{deferred_max} if defined $self->{deferred_max}; |
| 1166 | my $max = -1; |
| 1167 | for my $key (keys %{$self->{deferred}}) { |
| 1168 | $max = $key if $key > $max; |
| 1169 | } |
| 1170 | $self->{deferred_max} = $max; |
| 1171 | $max; |
| 1172 | } |
| 1173 | |
| 1174 | ################################################################ |
| 1175 | # |
| 1176 | # Matters related to autodeferment |
| 1177 | # |
| 1178 | |
| 1179 | # Get/set autodefer option |
| 1180 | sub autodefer { |
| 1181 | my $self = shift; |
| 1182 | if (@_) { |
| 1183 | my $old = $self->{autodefer}; |
| 1184 | $self->{autodefer} = shift; |
| 1185 | if ($old) { |
| 1186 | $self->_stop_autodeferring; |
| 1187 | @{$self->{ad_history}} = (); |
| 1188 | } |
| 1189 | $old; |
| 1190 | } else { |
| 1191 | $self->{autodefer}; |
| 1192 | } |
| 1193 | } |
| 1194 | |
| 1195 | # The user is trying to store record #$n Record that in the history, |
| 1196 | # and then enable (or disable) autodeferment if that seems useful. |
| 1197 | # Note that it's OK for $n to be a non-number, as long as the function |
| 1198 | # is prepared to deal with that. Nobody else looks at the ad_history. |
| 1199 | # |
| 1200 | # Now, what does the ad_history mean, and what is this function doing? |
| 1201 | # Essentially, the idea is to enable autodeferring when we see that the |
| 1202 | # user has made three consecutive STORE calls to three consecutive records. |
| 1203 | # ("Three" is actually ->{autodefer_threshhold}.) |
| 1204 | # A STORE call for record #$n inserts $n into the autodefer history, |
| 1205 | # and if the history contains three consecutive records, we enable |
| 1206 | # autodeferment. An ad_history of [X, Y] means that the most recent |
| 1207 | # STOREs were for records X, X+1, ..., Y, in that order. |
| 1208 | # |
| 1209 | # Inserting a nonconsecutive number erases the history and starts over. |
| 1210 | # |
| 1211 | # Performing a special operation like SPLICE erases the history. |
| 1212 | # |
| 1213 | # There's one special case: CLEAR means that CLEAR was just called. |
| 1214 | # In this case, we prime the history with [-2, -1] so that if the next |
| 1215 | # write is for record 0, autodeferring goes on immediately. This is for |
| 1216 | # the common special case of "@a = (...)". |
| 1217 | # |
| 1218 | sub _annotate_ad_history { |
| 1219 | my ($self, $n) = @_; |
| 1220 | return unless $self->{autodefer}; # feature is disabled |
| 1221 | return if $self->{defer}; # already in explicit defer mode |
| 1222 | return unless $self->{offsets}[-1] >= $self->{autodefer_filelen_threshhold}; |
| 1223 | |
| 1224 | local *H = $self->{ad_history}; |
| 1225 | if ($n eq 'CLEAR') { |
| 1226 | @H = (-2, -1); # prime the history with fake records |
| 1227 | $self->_stop_autodeferring; |
| 1228 | } elsif ($n =~ /^\d+$/) { |
| 1229 | if (@H == 0) { |
| 1230 | @H = ($n, $n); |
| 1231 | } else { # @H == 2 |
| 1232 | if ($H[1] == $n-1) { # another consecutive record |
| 1233 | $H[1]++; |
| 1234 | if ($H[1] - $H[0] + 1 >= $self->{autodefer_threshhold}) { |
| 1235 | $self->{autodeferring} = 1; |
| 1236 | } |
| 1237 | } else { # nonconsecutive- erase and start over |
| 1238 | @H = ($n, $n); |
| 1239 | $self->_stop_autodeferring; |
| 1240 | } |
| 1241 | } |
| 1242 | } else { # SPLICE or STORESIZE or some such |
| 1243 | @H = (); |
| 1244 | $self->_stop_autodeferring; |
| 1245 | } |
| 1246 | } |
| 1247 | |
| 1248 | # If autodeferring was enabled, cut it out and discard the history |
| 1249 | sub _stop_autodeferring { |
| 1250 | my $self = shift; |
| 1251 | if ($self->{autodeferring}) { |
| 1252 | $self->_flush; |
| 1253 | } |
| 1254 | $self->{autodeferring} = 0; |
| 1255 | } |
| 1256 | |
| 1257 | ################################################################ |
| 1258 | |
| 1259 | |
| 1260 | # This is NOT a method. It is here for two reasons: |
| 1261 | # 1. To factor a fairly complicated block out of the constructor |
| 1262 | # 2. To provide access for the test suite, which need to be sure |
| 1263 | # files are being written properly. |
| 1264 | sub _default_recsep { |
| 1265 | my $recsep = $/; |
| 1266 | if ($^O eq 'MSWin32') { # Dos too? |
| 1267 | # Windows users expect files to be terminated with \r\n |
| 1268 | # But $/ is set to \n instead |
| 1269 | # Note that this also transforms \n\n into \r\n\r\n. |
| 1270 | # That is a feature. |
| 1271 | $recsep =~ s/\n/\r\n/g; |
| 1272 | } |
| 1273 | $recsep; |
| 1274 | } |
| 1275 | |
| 1276 | # Utility function for _check_integrity |
| 1277 | sub _ci_warn { |
| 1278 | my $msg = shift; |
| 1279 | $msg =~ s/\n/\\n/g; |
| 1280 | $msg =~ s/\r/\\r/g; |
| 1281 | print "# $msg\n"; |
| 1282 | } |
| 1283 | |
| 1284 | # Given a file, make sure the cache is consistent with the |
| 1285 | # file contents and the internal data structures are consistent with |
| 1286 | # each other. Returns true if everything checks out, false if not |
| 1287 | # |
| 1288 | # The $file argument is no longer used. It is retained for compatibility |
| 1289 | # with the existing test suite. |
| 1290 | sub _check_integrity { |
| 1291 | my ($self, $file, $warn) = @_; |
| 1292 | my $rsl = $self->{recseplen}; |
| 1293 | my $rs = $self->{recsep}; |
| 1294 | my $good = 1; |
| 1295 | local *_; # local $_ does not work here |
| 1296 | local $DIAGNOSTIC = 1; |
| 1297 | |
| 1298 | if (not defined $rs) { |
| 1299 | _ci_warn("recsep is undef!"); |
| 1300 | $good = 0; |
| 1301 | } elsif ($rs eq "") { |
| 1302 | _ci_warn("recsep is empty!"); |
| 1303 | $good = 0; |
| 1304 | } elsif ($rsl != length $rs) { |
| 1305 | my $ln = length $rs; |
| 1306 | _ci_warn("recsep <$rs> has length $ln, should be $rsl"); |
| 1307 | $good = 0; |
| 1308 | } |
| 1309 | |
| 1310 | if (not defined $self->{offsets}[0]) { |
| 1311 | _ci_warn("offset 0 is missing!"); |
| 1312 | $good = 0; |
| 1313 | |
| 1314 | } elsif ($self->{offsets}[0] != 0) { |
| 1315 | _ci_warn("rec 0: offset <$self->{offsets}[0]> s/b 0!"); |
| 1316 | $good = 0; |
| 1317 | } |
| 1318 | |
| 1319 | my $cached = 0; |
| 1320 | { |
| 1321 | local *F = $self->{fh}; |
| 1322 | seek F, 0, SEEK_SET; |
| 1323 | local $. = 0; |
| 1324 | local $/ = $rs; |
| 1325 | |
| 1326 | while (<F>) { |
| 1327 | my $n = $. - 1; |
| 1328 | my $cached = $self->{cache}->_produce($n); |
| 1329 | my $offset = $self->{offsets}[$.]; |
| 1330 | my $ao = tell F; |
| 1331 | if (defined $offset && $offset != $ao) { |
| 1332 | _ci_warn("rec $n: offset <$offset> actual <$ao>"); |
| 1333 | $good = 0; |
| 1334 | } |
| 1335 | if (defined $cached && $_ ne $cached && ! $self->{deferred}{$n}) { |
| 1336 | $good = 0; |
| 1337 | _ci_warn("rec $n: cached <$cached> actual <$_>"); |
| 1338 | } |
| 1339 | if (defined $cached && substr($cached, -$rsl) ne $rs) { |
| 1340 | $good = 0; |
| 1341 | _ci_warn("rec $n in the cache is missing the record separator"); |
| 1342 | } |
| 1343 | if (! defined $offset && $self->{eof}) { |
| 1344 | $good = 0; |
| 1345 | _ci_warn("The offset table was marked complete, but it is missing element $."); |
| 1346 | } |
| 1347 | } |
| 1348 | if (@{$self->{offsets}} > $.+1) { |
| 1349 | $good = 0; |
| 1350 | my $n = @{$self->{offsets}}; |
| 1351 | _ci_warn("The offset table has $n items, but the file has only $."); |
| 1352 | } |
| 1353 | |
| 1354 | my $deferring = $self->_is_deferring; |
| 1355 | for my $n ($self->{cache}->ckeys) { |
| 1356 | my $r = $self->{cache}->_produce($n); |
| 1357 | $cached += length($r); |
| 1358 | next if $n+1 <= $.; # checked this already |
| 1359 | _ci_warn("spurious caching of record $n"); |
| 1360 | $good = 0; |
| 1361 | } |
| 1362 | my $b = $self->{cache}->bytes; |
| 1363 | if ($cached != $b) { |
| 1364 | _ci_warn("cache size is $b, should be $cached"); |
| 1365 | $good = 0; |
| 1366 | } |
| 1367 | } |
| 1368 | |
| 1369 | # That cache has its own set of tests |
| 1370 | $good = 0 unless $self->{cache}->_check_integrity; |
| 1371 | |
| 1372 | # Now let's check the deferbuffer |
| 1373 | # Unless deferred writing is enabled, it should be empty |
| 1374 | if (! $self->_is_deferring && %{$self->{deferred}}) { |
| 1375 | _ci_warn("deferred writing disabled, but deferbuffer nonempty"); |
| 1376 | $good = 0; |
| 1377 | } |
| 1378 | |
| 1379 | # Any record in the deferbuffer should *not* be present in the readcache |
| 1380 | my $deferred_s = 0; |
| 1381 | while (my ($n, $r) = each %{$self->{deferred}}) { |
| 1382 | $deferred_s += length($r); |
| 1383 | if (defined $self->{cache}->_produce($n)) { |
| 1384 | _ci_warn("record $n is in the deferbuffer *and* the readcache"); |
| 1385 | $good = 0; |
| 1386 | } |
| 1387 | if (substr($r, -$rsl) ne $rs) { |
| 1388 | _ci_warn("rec $n in the deferbuffer is missing the record separator"); |
| 1389 | $good = 0; |
| 1390 | } |
| 1391 | } |
| 1392 | |
| 1393 | # Total size of deferbuffer should match internal total |
| 1394 | if ($deferred_s != $self->{deferred_s}) { |
| 1395 | _ci_warn("buffer size is $self->{deferred_s}, should be $deferred_s"); |
| 1396 | $good = 0; |
| 1397 | } |
| 1398 | |
| 1399 | # Total size of deferbuffer should not exceed the specified limit |
| 1400 | if ($deferred_s > $self->{dw_size}) { |
| 1401 | _ci_warn("buffer size is $self->{deferred_s} which exceeds the limit of $self->{dw_size}"); |
| 1402 | $good = 0; |
| 1403 | } |
| 1404 | |
| 1405 | # Total size of cached data should not exceed the specified limit |
| 1406 | if ($deferred_s + $cached > $self->{memory}) { |
| 1407 | my $total = $deferred_s + $cached; |
| 1408 | _ci_warn("total stored data size is $total which exceeds the limit of $self->{memory}"); |
| 1409 | $good = 0; |
| 1410 | } |
| 1411 | |
| 1412 | # Stuff related to autodeferment |
| 1413 | if (!$self->{autodefer} && @{$self->{ad_history}}) { |
| 1414 | _ci_warn("autodefer is disabled, but ad_history is nonempty"); |
| 1415 | $good = 0; |
| 1416 | } |
| 1417 | if ($self->{autodeferring} && $self->{defer}) { |
| 1418 | _ci_warn("both autodeferring and explicit deferring are active"); |
| 1419 | $good = 0; |
| 1420 | } |
| 1421 | if (@{$self->{ad_history}} == 0) { |
| 1422 | # That's OK, no additional tests required |
| 1423 | } elsif (@{$self->{ad_history}} == 2) { |
| 1424 | my @non_number = grep !/^-?\d+$/, @{$self->{ad_history}}; |
| 1425 | if (@non_number) { |
| 1426 | my $msg; |
| 1427 | { local $" = ')('; |
| 1428 | $msg = "ad_history contains non-numbers (@{$self->{ad_history}})"; |
| 1429 | } |
| 1430 | _ci_warn($msg); |
| 1431 | $good = 0; |
| 1432 | } elsif ($self->{ad_history}[1] < $self->{ad_history}[0]) { |
| 1433 | _ci_warn("ad_history has nonsensical values @{$self->{ad_history}}"); |
| 1434 | $good = 0; |
| 1435 | } |
| 1436 | } else { |
| 1437 | _ci_warn("ad_history has bad length <@{$self->{ad_history}}>"); |
| 1438 | $good = 0; |
| 1439 | } |
| 1440 | |
| 1441 | $good; |
| 1442 | } |
| 1443 | |
| 1444 | ################################################################ |
| 1445 | # |
| 1446 | # Tie::File::Cache |
| 1447 | # |
| 1448 | # Read cache |
| 1449 | |
| 1450 | package Tie::File::Cache; |
| 1451 | $Tie::File::Cache::VERSION = $Tie::File::VERSION; |
| 1452 | use Carp ':DEFAULT', 'confess'; |
| 1453 | |
| 1454 | sub HEAP () { 0 } |
| 1455 | sub HASH () { 1 } |
| 1456 | sub MAX () { 2 } |
| 1457 | sub BYTES() { 3 } |
| 1458 | #sub STAT () { 4 } # Array with request statistics for each record |
| 1459 | #sub MISS () { 5 } # Total number of cache misses |
| 1460 | #sub REQ () { 6 } # Total number of cache requests |
| 1461 | use strict 'vars'; |
| 1462 | |
| 1463 | sub new { |
| 1464 | my ($pack, $max) = @_; |
| 1465 | local *_; |
| 1466 | croak "missing argument to ->new" unless defined $max; |
| 1467 | my $self = []; |
| 1468 | bless $self => $pack; |
| 1469 | @$self = (Tie::File::Heap->new($self), {}, $max, 0); |
| 1470 | $self; |
| 1471 | } |
| 1472 | |
| 1473 | sub adj_limit { |
| 1474 | my ($self, $n) = @_; |
| 1475 | $self->[MAX] += $n; |
| 1476 | } |
| 1477 | |
| 1478 | sub set_limit { |
| 1479 | my ($self, $n) = @_; |
| 1480 | $self->[MAX] = $n; |
| 1481 | } |
| 1482 | |
| 1483 | # For internal use only |
| 1484 | # Will be called by the heap structure to notify us that a certain |
| 1485 | # piece of data has moved from one heap element to another. |
| 1486 | # $k is the hash key of the item |
| 1487 | # $n is the new index into the heap at which it is stored |
| 1488 | # If $n is undefined, the item has been removed from the heap. |
| 1489 | sub _heap_move { |
| 1490 | my ($self, $k, $n) = @_; |
| 1491 | if (defined $n) { |
| 1492 | $self->[HASH]{$k} = $n; |
| 1493 | } else { |
| 1494 | delete $self->[HASH]{$k}; |
| 1495 | } |
| 1496 | } |
| 1497 | |
| 1498 | sub insert { |
| 1499 | my ($self, $key, $val) = @_; |
| 1500 | local *_; |
| 1501 | croak "missing argument to ->insert" unless defined $key; |
| 1502 | unless (defined $self->[MAX]) { |
| 1503 | confess "undefined max" ; |
| 1504 | } |
| 1505 | confess "undefined val" unless defined $val; |
| 1506 | return if length($val) > $self->[MAX]; |
| 1507 | |
| 1508 | # if ($self->[STAT]) { |
| 1509 | # $self->[STAT][$key] = 1; |
| 1510 | # return; |
| 1511 | # } |
| 1512 | |
| 1513 | my $oldnode = $self->[HASH]{$key}; |
| 1514 | if (defined $oldnode) { |
| 1515 | my $oldval = $self->[HEAP]->set_val($oldnode, $val); |
| 1516 | $self->[BYTES] -= length($oldval); |
| 1517 | } else { |
| 1518 | $self->[HEAP]->insert($key, $val); |
| 1519 | } |
| 1520 | $self->[BYTES] += length($val); |
| 1521 | $self->flush if $self->[BYTES] > $self->[MAX]; |
| 1522 | } |
| 1523 | |
| 1524 | sub expire { |
| 1525 | my $self = shift; |
| 1526 | my $old_data = $self->[HEAP]->popheap; |
| 1527 | return unless defined $old_data; |
| 1528 | $self->[BYTES] -= length $old_data; |
| 1529 | $old_data; |
| 1530 | } |
| 1531 | |
| 1532 | sub remove { |
| 1533 | my ($self, @keys) = @_; |
| 1534 | my @result; |
| 1535 | |
| 1536 | # if ($self->[STAT]) { |
| 1537 | # for my $key (@keys) { |
| 1538 | # $self->[STAT][$key] = 0; |
| 1539 | # } |
| 1540 | # return; |
| 1541 | # } |
| 1542 | |
| 1543 | for my $key (@keys) { |
| 1544 | next unless exists $self->[HASH]{$key}; |
| 1545 | my $old_data = $self->[HEAP]->remove($self->[HASH]{$key}); |
| 1546 | $self->[BYTES] -= length $old_data; |
| 1547 | push @result, $old_data; |
| 1548 | } |
| 1549 | @result; |
| 1550 | } |
| 1551 | |
| 1552 | sub lookup { |
| 1553 | my ($self, $key) = @_; |
| 1554 | local *_; |
| 1555 | croak "missing argument to ->lookup" unless defined $key; |
| 1556 | |
| 1557 | # if ($self->[STAT]) { |
| 1558 | # $self->[MISS]++ if $self->[STAT][$key]++ == 0; |
| 1559 | # $self->[REQ]++; |
| 1560 | # my $hit_rate = 1 - $self->[MISS] / $self->[REQ]; |
| 1561 | # # Do some testing to determine this threshhold |
| 1562 | # $#$self = STAT - 1 if $hit_rate > 0.20; |
| 1563 | # } |
| 1564 | |
| 1565 | if (exists $self->[HASH]{$key}) { |
| 1566 | $self->[HEAP]->lookup($self->[HASH]{$key}); |
| 1567 | } else { |
| 1568 | return; |
| 1569 | } |
| 1570 | } |
| 1571 | |
| 1572 | # For internal use only |
| 1573 | sub _produce { |
| 1574 | my ($self, $key) = @_; |
| 1575 | my $loc = $self->[HASH]{$key}; |
| 1576 | return unless defined $loc; |
| 1577 | $self->[HEAP][$loc][2]; |
| 1578 | } |
| 1579 | |
| 1580 | # For internal use only |
| 1581 | sub _promote { |
| 1582 | my ($self, $key) = @_; |
| 1583 | $self->[HEAP]->promote($self->[HASH]{$key}); |
| 1584 | } |
| 1585 | |
| 1586 | sub empty { |
| 1587 | my ($self) = @_; |
| 1588 | %{$self->[HASH]} = (); |
| 1589 | $self->[BYTES] = 0; |
| 1590 | $self->[HEAP]->empty; |
| 1591 | # @{$self->[STAT]} = (); |
| 1592 | # $self->[MISS] = 0; |
| 1593 | # $self->[REQ] = 0; |
| 1594 | } |
| 1595 | |
| 1596 | sub is_empty { |
| 1597 | my ($self) = @_; |
| 1598 | keys %{$self->[HASH]} == 0; |
| 1599 | } |
| 1600 | |
| 1601 | sub update { |
| 1602 | my ($self, $key, $val) = @_; |
| 1603 | local *_; |
| 1604 | croak "missing argument to ->update" unless defined $key; |
| 1605 | if (length($val) > $self->[MAX]) { |
| 1606 | my ($oldval) = $self->remove($key); |
| 1607 | $self->[BYTES] -= length($oldval) if defined $oldval; |
| 1608 | } elsif (exists $self->[HASH]{$key}) { |
| 1609 | my $oldval = $self->[HEAP]->set_val($self->[HASH]{$key}, $val); |
| 1610 | $self->[BYTES] += length($val); |
| 1611 | $self->[BYTES] -= length($oldval) if defined $oldval; |
| 1612 | } else { |
| 1613 | $self->[HEAP]->insert($key, $val); |
| 1614 | $self->[BYTES] += length($val); |
| 1615 | } |
| 1616 | $self->flush; |
| 1617 | } |
| 1618 | |
| 1619 | sub rekey { |
| 1620 | my ($self, $okeys, $nkeys) = @_; |
| 1621 | local *_; |
| 1622 | my %map; |
| 1623 | @map{@$okeys} = @$nkeys; |
| 1624 | croak "missing argument to ->rekey" unless defined $nkeys; |
| 1625 | croak "length mismatch in ->rekey arguments" unless @$nkeys == @$okeys; |
| 1626 | my %adjusted; # map new keys to heap indices |
| 1627 | # You should be able to cut this to one loop TODO XXX |
| 1628 | for (0 .. $#$okeys) { |
| 1629 | $adjusted{$nkeys->[$_]} = delete $self->[HASH]{$okeys->[$_]}; |
| 1630 | } |
| 1631 | while (my ($nk, $ix) = each %adjusted) { |
| 1632 | # @{$self->[HASH]}{keys %adjusted} = values %adjusted; |
| 1633 | $self->[HEAP]->rekey($ix, $nk); |
| 1634 | $self->[HASH]{$nk} = $ix; |
| 1635 | } |
| 1636 | } |
| 1637 | |
| 1638 | sub ckeys { |
| 1639 | my $self = shift; |
| 1640 | my @a = keys %{$self->[HASH]}; |
| 1641 | @a; |
| 1642 | } |
| 1643 | |
| 1644 | # Return total amount of cached data |
| 1645 | sub bytes { |
| 1646 | my $self = shift; |
| 1647 | $self->[BYTES]; |
| 1648 | } |
| 1649 | |
| 1650 | # Expire oldest item from cache until cache size is smaller than $max |
| 1651 | sub reduce_size_to { |
| 1652 | my ($self, $max) = @_; |
| 1653 | until ($self->[BYTES] <= $max) { |
| 1654 | # Note that Tie::File::Cache::expire has been inlined here |
| 1655 | my $old_data = $self->[HEAP]->popheap; |
| 1656 | return unless defined $old_data; |
| 1657 | $self->[BYTES] -= length $old_data; |
| 1658 | } |
| 1659 | } |
| 1660 | |
| 1661 | # Why not just $self->reduce_size_to($self->[MAX])? |
| 1662 | # Try this when things stabilize TODO XXX |
| 1663 | # If the cache is too full, expire the oldest records |
| 1664 | sub flush { |
| 1665 | my $self = shift; |
| 1666 | $self->reduce_size_to($self->[MAX]) if $self->[BYTES] > $self->[MAX]; |
| 1667 | } |
| 1668 | |
| 1669 | # For internal use only |
| 1670 | sub _produce_lru { |
| 1671 | my $self = shift; |
| 1672 | $self->[HEAP]->expire_order; |
| 1673 | } |
| 1674 | |
| 1675 | BEGIN { *_ci_warn = \&Tie::File::_ci_warn } |
| 1676 | |
| 1677 | sub _check_integrity { # For CACHE |
| 1678 | my $self = shift; |
| 1679 | my $good = 1; |
| 1680 | |
| 1681 | # Test HEAP |
| 1682 | $self->[HEAP]->_check_integrity or $good = 0; |
| 1683 | |
| 1684 | # Test HASH |
| 1685 | my $bytes = 0; |
| 1686 | for my $k (keys %{$self->[HASH]}) { |
| 1687 | if ($k ne '0' && $k !~ /^[1-9][0-9]*$/) { |
| 1688 | $good = 0; |
| 1689 | _ci_warn "Cache hash key <$k> is non-numeric"; |
| 1690 | } |
| 1691 | |
| 1692 | my $h = $self->[HASH]{$k}; |
| 1693 | if (! defined $h) { |
| 1694 | $good = 0; |
| 1695 | _ci_warn "Heap index number for key $k is undefined"; |
| 1696 | } elsif ($h == 0) { |
| 1697 | $good = 0; |
| 1698 | _ci_warn "Heap index number for key $k is zero"; |
| 1699 | } else { |
| 1700 | my $j = $self->[HEAP][$h]; |
| 1701 | if (! defined $j) { |
| 1702 | $good = 0; |
| 1703 | _ci_warn "Heap contents key $k (=> $h) are undefined"; |
| 1704 | } else { |
| 1705 | $bytes += length($j->[2]); |
| 1706 | if ($k ne $j->[1]) { |
| 1707 | $good = 0; |
| 1708 | _ci_warn "Heap contents key $k (=> $h) is $j->[1], should be $k"; |
| 1709 | } |
| 1710 | } |
| 1711 | } |
| 1712 | } |
| 1713 | |
| 1714 | # Test BYTES |
| 1715 | if ($bytes != $self->[BYTES]) { |
| 1716 | $good = 0; |
| 1717 | _ci_warn "Total data in cache is $bytes, expected $self->[BYTES]"; |
| 1718 | } |
| 1719 | |
| 1720 | # Test MAX |
| 1721 | if ($bytes > $self->[MAX]) { |
| 1722 | $good = 0; |
| 1723 | _ci_warn "Total data in cache is $bytes, exceeds maximum $self->[MAX]"; |
| 1724 | } |
| 1725 | |
| 1726 | return $good; |
| 1727 | } |
| 1728 | |
| 1729 | sub delink { |
| 1730 | my $self = shift; |
| 1731 | $self->[HEAP] = undef; # Bye bye heap |
| 1732 | } |
| 1733 | |
| 1734 | ################################################################ |
| 1735 | # |
| 1736 | # Tie::File::Heap |
| 1737 | # |
| 1738 | # Heap data structure for use by cache LRU routines |
| 1739 | |
| 1740 | package Tie::File::Heap; |
| 1741 | use Carp ':DEFAULT', 'confess'; |
| 1742 | $Tie::File::Heap::VERSION = $Tie::File::Cache::VERSION; |
| 1743 | sub SEQ () { 0 }; |
| 1744 | sub KEY () { 1 }; |
| 1745 | sub DAT () { 2 }; |
| 1746 | |
| 1747 | sub new { |
| 1748 | my ($pack, $cache) = @_; |
| 1749 | die "$pack: Parent cache object $cache does not support _heap_move method" |
| 1750 | unless eval { $cache->can('_heap_move') }; |
| 1751 | my $self = [[0,$cache,0]]; |
| 1752 | bless $self => $pack; |
| 1753 | } |
| 1754 | |
| 1755 | # Allocate a new sequence number, larger than all previously allocated numbers |
| 1756 | sub _nseq { |
| 1757 | my $self = shift; |
| 1758 | $self->[0][0]++; |
| 1759 | } |
| 1760 | |
| 1761 | sub _cache { |
| 1762 | my $self = shift; |
| 1763 | $self->[0][1]; |
| 1764 | } |
| 1765 | |
| 1766 | sub _nelts { |
| 1767 | my $self = shift; |
| 1768 | $self->[0][2]; |
| 1769 | } |
| 1770 | |
| 1771 | sub _nelts_inc { |
| 1772 | my $self = shift; |
| 1773 | ++$self->[0][2]; |
| 1774 | } |
| 1775 | |
| 1776 | sub _nelts_dec { |
| 1777 | my $self = shift; |
| 1778 | --$self->[0][2]; |
| 1779 | } |
| 1780 | |
| 1781 | sub is_empty { |
| 1782 | my $self = shift; |
| 1783 | $self->_nelts == 0; |
| 1784 | } |
| 1785 | |
| 1786 | sub empty { |
| 1787 | my $self = shift; |
| 1788 | $#$self = 0; |
| 1789 | $self->[0][2] = 0; |
| 1790 | $self->[0][0] = 0; # might as well reset the sequence numbers |
| 1791 | } |
| 1792 | |
| 1793 | # notify the parent cache object that we moved something |
| 1794 | sub _heap_move { |
| 1795 | my $self = shift; |
| 1796 | $self->_cache->_heap_move(@_); |
| 1797 | } |
| 1798 | |
| 1799 | # Insert a piece of data into the heap with the indicated sequence number. |
| 1800 | # The item with the smallest sequence number is always at the top. |
| 1801 | # If no sequence number is specified, allocate a new one and insert the |
| 1802 | # item at the bottom. |
| 1803 | sub insert { |
| 1804 | my ($self, $key, $data, $seq) = @_; |
| 1805 | $seq = $self->_nseq unless defined $seq; |
| 1806 | $self->_insert_new([$seq, $key, $data]); |
| 1807 | } |
| 1808 | |
| 1809 | # Insert a new, fresh item at the bottom of the heap |
| 1810 | sub _insert_new { |
| 1811 | my ($self, $item) = @_; |
| 1812 | my $i = @$self; |
| 1813 | $i = int($i/2) until defined $self->[$i/2]; |
| 1814 | $self->[$i] = $item; |
| 1815 | $self->[0][1]->_heap_move($self->[$i][KEY], $i); |
| 1816 | $self->_nelts_inc; |
| 1817 | } |
| 1818 | |
| 1819 | # Insert [$data, $seq] pair at or below item $i in the heap. |
| 1820 | # If $i is omitted, default to 1 (the top element.) |
| 1821 | sub _insert { |
| 1822 | my ($self, $item, $i) = @_; |
| 1823 | # $self->_check_loc($i) if defined $i; |
| 1824 | $i = 1 unless defined $i; |
| 1825 | until (! defined $self->[$i]) { |
| 1826 | if ($self->[$i][SEQ] > $item->[SEQ]) { # inserted item is older |
| 1827 | ($self->[$i], $item) = ($item, $self->[$i]); |
| 1828 | $self->[0][1]->_heap_move($self->[$i][KEY], $i); |
| 1829 | } |
| 1830 | # If either is undefined, go that way. Otherwise, choose at random |
| 1831 | my $dir; |
| 1832 | $dir = 0 if !defined $self->[2*$i]; |
| 1833 | $dir = 1 if !defined $self->[2*$i+1]; |
| 1834 | $dir = int(rand(2)) unless defined $dir; |
| 1835 | $i = 2*$i + $dir; |
| 1836 | } |
| 1837 | $self->[$i] = $item; |
| 1838 | $self->[0][1]->_heap_move($self->[$i][KEY], $i); |
| 1839 | $self->_nelts_inc; |
| 1840 | } |
| 1841 | |
| 1842 | # Remove the item at node $i from the heap, moving child items upwards. |
| 1843 | # The item with the smallest sequence number is always at the top. |
| 1844 | # Moving items upwards maintains this condition. |
| 1845 | # Return the removed item. Return undef if there was no item at node $i. |
| 1846 | sub remove { |
| 1847 | my ($self, $i) = @_; |
| 1848 | $i = 1 unless defined $i; |
| 1849 | my $top = $self->[$i]; |
| 1850 | return unless defined $top; |
| 1851 | while (1) { |
| 1852 | my $ii; |
| 1853 | my ($L, $R) = (2*$i, 2*$i+1); |
| 1854 | |
| 1855 | # If either is undefined, go the other way. |
| 1856 | # Otherwise, go towards the smallest. |
| 1857 | last unless defined $self->[$L] || defined $self->[$R]; |
| 1858 | $ii = $R if not defined $self->[$L]; |
| 1859 | $ii = $L if not defined $self->[$R]; |
| 1860 | unless (defined $ii) { |
| 1861 | $ii = $self->[$L][SEQ] < $self->[$R][SEQ] ? $L : $R; |
| 1862 | } |
| 1863 | |
| 1864 | $self->[$i] = $self->[$ii]; # Promote child to fill vacated spot |
| 1865 | $self->[0][1]->_heap_move($self->[$i][KEY], $i); |
| 1866 | $i = $ii; # Fill new vacated spot |
| 1867 | } |
| 1868 | $self->[0][1]->_heap_move($top->[KEY], undef); |
| 1869 | undef $self->[$i]; |
| 1870 | $self->_nelts_dec; |
| 1871 | return $top->[DAT]; |
| 1872 | } |
| 1873 | |
| 1874 | sub popheap { |
| 1875 | my $self = shift; |
| 1876 | $self->remove(1); |
| 1877 | } |
| 1878 | |
| 1879 | # set the sequence number of the indicated item to a higher number |
| 1880 | # than any other item in the heap, and bubble the item down to the |
| 1881 | # bottom. |
| 1882 | sub promote { |
| 1883 | my ($self, $n) = @_; |
| 1884 | # $self->_check_loc($n); |
| 1885 | $self->[$n][SEQ] = $self->_nseq; |
| 1886 | my $i = $n; |
| 1887 | while (1) { |
| 1888 | my ($L, $R) = (2*$i, 2*$i+1); |
| 1889 | my $dir; |
| 1890 | last unless defined $self->[$L] || defined $self->[$R]; |
| 1891 | $dir = $R unless defined $self->[$L]; |
| 1892 | $dir = $L unless defined $self->[$R]; |
| 1893 | unless (defined $dir) { |
| 1894 | $dir = $self->[$L][SEQ] < $self->[$R][SEQ] ? $L : $R; |
| 1895 | } |
| 1896 | @{$self}[$i, $dir] = @{$self}[$dir, $i]; |
| 1897 | for ($i, $dir) { |
| 1898 | $self->[0][1]->_heap_move($self->[$_][KEY], $_) if defined $self->[$_]; |
| 1899 | } |
| 1900 | $i = $dir; |
| 1901 | } |
| 1902 | } |
| 1903 | |
| 1904 | # Return item $n from the heap, promoting its LRU status |
| 1905 | sub lookup { |
| 1906 | my ($self, $n) = @_; |
| 1907 | # $self->_check_loc($n); |
| 1908 | my $val = $self->[$n]; |
| 1909 | $self->promote($n); |
| 1910 | $val->[DAT]; |
| 1911 | } |
| 1912 | |
| 1913 | |
| 1914 | # Assign a new value for node $n, promoting it to the bottom of the heap |
| 1915 | sub set_val { |
| 1916 | my ($self, $n, $val) = @_; |
| 1917 | # $self->_check_loc($n); |
| 1918 | my $oval = $self->[$n][DAT]; |
| 1919 | $self->[$n][DAT] = $val; |
| 1920 | $self->promote($n); |
| 1921 | return $oval; |
| 1922 | } |
| 1923 | |
| 1924 | # The hask key has changed for an item; |
| 1925 | # alter the heap's record of the hash key |
| 1926 | sub rekey { |
| 1927 | my ($self, $n, $new_key) = @_; |
| 1928 | # $self->_check_loc($n); |
| 1929 | $self->[$n][KEY] = $new_key; |
| 1930 | } |
| 1931 | |
| 1932 | sub _check_loc { |
| 1933 | my ($self, $n) = @_; |
| 1934 | unless (1 || defined $self->[$n]) { |
| 1935 | confess "_check_loc($n) failed"; |
| 1936 | } |
| 1937 | } |
| 1938 | |
| 1939 | BEGIN { *_ci_warn = \&Tie::File::_ci_warn } |
| 1940 | |
| 1941 | sub _check_integrity { |
| 1942 | my $self = shift; |
| 1943 | my $good = 1; |
| 1944 | my %seq; |
| 1945 | |
| 1946 | unless (eval {$self->[0][1]->isa("Tie::File::Cache")}) { |
| 1947 | _ci_warn "Element 0 of heap corrupt"; |
| 1948 | $good = 0; |
| 1949 | } |
| 1950 | $good = 0 unless $self->_satisfies_heap_condition(1); |
| 1951 | for my $i (2 .. $#{$self}) { |
| 1952 | my $p = int($i/2); # index of parent node |
| 1953 | if (defined $self->[$i] && ! defined $self->[$p]) { |
| 1954 | _ci_warn "Element $i of heap defined, but parent $p isn't"; |
| 1955 | $good = 0; |
| 1956 | } |
| 1957 | |
| 1958 | if (defined $self->[$i]) { |
| 1959 | if ($seq{$self->[$i][SEQ]}) { |
| 1960 | my $seq = $self->[$i][SEQ]; |
| 1961 | _ci_warn "Nodes $i and $seq{$seq} both have SEQ=$seq"; |
| 1962 | $good = 0; |
| 1963 | } else { |
| 1964 | $seq{$self->[$i][SEQ]} = $i; |
| 1965 | } |
| 1966 | } |
| 1967 | } |
| 1968 | |
| 1969 | return $good; |
| 1970 | } |
| 1971 | |
| 1972 | sub _satisfies_heap_condition { |
| 1973 | my $self = shift; |
| 1974 | my $n = shift || 1; |
| 1975 | my $good = 1; |
| 1976 | for (0, 1) { |
| 1977 | my $c = $n*2 + $_; |
| 1978 | next unless defined $self->[$c]; |
| 1979 | if ($self->[$n][SEQ] >= $self->[$c]) { |
| 1980 | _ci_warn "Node $n of heap does not predate node $c"; |
| 1981 | $good = 0 ; |
| 1982 | } |
| 1983 | $good = 0 unless $self->_satisfies_heap_condition($c); |
| 1984 | } |
| 1985 | return $good; |
| 1986 | } |
| 1987 | |
| 1988 | # Return a list of all the values, sorted by expiration order |
| 1989 | sub expire_order { |
| 1990 | my $self = shift; |
| 1991 | my @nodes = sort {$a->[SEQ] <=> $b->[SEQ]} $self->_nodes; |
| 1992 | map { $_->[KEY] } @nodes; |
| 1993 | } |
| 1994 | |
| 1995 | sub _nodes { |
| 1996 | my $self = shift; |
| 1997 | my $i = shift || 1; |
| 1998 | return unless defined $self->[$i]; |
| 1999 | ($self->[$i], $self->_nodes($i*2), $self->_nodes($i*2+1)); |
| 2000 | } |
| 2001 | |
| 2002 | "Cogito, ergo sum."; # don't forget to return a true value from the file |
| 2003 | |
| 2004 | __END__ |
| 2005 | |
| 2006 | =head1 NAME |
| 2007 | |
| 2008 | Tie::File - Access the lines of a disk file via a Perl array |
| 2009 | |
| 2010 | =head1 SYNOPSIS |
| 2011 | |
| 2012 | # This file documents Tie::File version 0.97 |
| 2013 | use Tie::File; |
| 2014 | |
| 2015 | tie @array, 'Tie::File', filename or die ...; |
| 2016 | |
| 2017 | $array[13] = 'blah'; # line 13 of the file is now 'blah' |
| 2018 | print $array[42]; # display line 42 of the file |
| 2019 | |
| 2020 | $n_recs = @array; # how many records are in the file? |
| 2021 | $#array -= 2; # chop two records off the end |
| 2022 | |
| 2023 | |
| 2024 | for (@array) { |
| 2025 | s/PERL/Perl/g; # Replace PERL with Perl everywhere in the file |
| 2026 | } |
| 2027 | |
| 2028 | # These are just like regular push, pop, unshift, shift, and splice |
| 2029 | # Except that they modify the file in the way you would expect |
| 2030 | |
| 2031 | push @array, new recs...; |
| 2032 | my $r1 = pop @array; |
| 2033 | unshift @array, new recs...; |
| 2034 | my $r2 = shift @array; |
| 2035 | @old_recs = splice @array, 3, 7, new recs...; |
| 2036 | |
| 2037 | untie @array; # all finished |
| 2038 | |
| 2039 | |
| 2040 | =head1 DESCRIPTION |
| 2041 | |
| 2042 | C<Tie::File> represents a regular text file as a Perl array. Each |
| 2043 | element in the array corresponds to a record in the file. The first |
| 2044 | line of the file is element 0 of the array; the second line is element |
| 2045 | 1, and so on. |
| 2046 | |
| 2047 | The file is I<not> loaded into memory, so this will work even for |
| 2048 | gigantic files. |
| 2049 | |
| 2050 | Changes to the array are reflected in the file immediately. |
| 2051 | |
| 2052 | Lazy people and beginners may now stop reading the manual. |
| 2053 | |
| 2054 | =head2 C<recsep> |
| 2055 | |
| 2056 | What is a 'record'? By default, the meaning is the same as for the |
| 2057 | C<E<lt>...E<gt>> operator: It's a string terminated by C<$/>, which is |
| 2058 | probably C<"\n">. (Minor exception: on DOS and Win32 systems, a |
| 2059 | 'record' is a string terminated by C<"\r\n">.) You may change the |
| 2060 | definition of "record" by supplying the C<recsep> option in the C<tie> |
| 2061 | call: |
| 2062 | |
| 2063 | tie @array, 'Tie::File', $file, recsep => 'es'; |
| 2064 | |
| 2065 | This says that records are delimited by the string C<es>. If the file |
| 2066 | contained the following data: |
| 2067 | |
| 2068 | Curse these pesky flies!\n |
| 2069 | |
| 2070 | then the C<@array> would appear to have four elements: |
| 2071 | |
| 2072 | "Curse th" |
| 2073 | "e p" |
| 2074 | "ky fli" |
| 2075 | "!\n" |
| 2076 | |
| 2077 | An undefined value is not permitted as a record separator. Perl's |
| 2078 | special "paragraph mode" semantics (E<agrave> la C<$/ = "">) are not |
| 2079 | emulated. |
| 2080 | |
| 2081 | Records read from the tied array do not have the record separator |
| 2082 | string on the end; this is to allow |
| 2083 | |
| 2084 | $array[17] .= "extra"; |
| 2085 | |
| 2086 | to work as expected. |
| 2087 | |
| 2088 | (See L<"autochomp">, below.) Records stored into the array will have |
| 2089 | the record separator string appended before they are written to the |
| 2090 | file, if they don't have one already. For example, if the record |
| 2091 | separator string is C<"\n">, then the following two lines do exactly |
| 2092 | the same thing: |
| 2093 | |
| 2094 | $array[17] = "Cherry pie"; |
| 2095 | $array[17] = "Cherry pie\n"; |
| 2096 | |
| 2097 | The result is that the contents of line 17 of the file will be |
| 2098 | replaced with "Cherry pie"; a newline character will separate line 17 |
| 2099 | from line 18. This means that this code will do nothing: |
| 2100 | |
| 2101 | chomp $array[17]; |
| 2102 | |
| 2103 | Because the C<chomp>ed value will have the separator reattached when |
| 2104 | it is written back to the file. There is no way to create a file |
| 2105 | whose trailing record separator string is missing. |
| 2106 | |
| 2107 | Inserting records that I<contain> the record separator string is not |
| 2108 | supported by this module. It will probably produce a reasonable |
| 2109 | result, but what this result will be may change in a future version. |
| 2110 | Use 'splice' to insert records or to replace one record with several. |
| 2111 | |
| 2112 | =head2 C<autochomp> |
| 2113 | |
| 2114 | Normally, array elements have the record separator removed, so that if |
| 2115 | the file contains the text |
| 2116 | |
| 2117 | Gold |
| 2118 | Frankincense |
| 2119 | Myrrh |
| 2120 | |
| 2121 | the tied array will appear to contain C<("Gold", "Frankincense", |
| 2122 | "Myrrh")>. If you set C<autochomp> to a false value, the record |
| 2123 | separator will not be removed. If the file above was tied with |
| 2124 | |
| 2125 | tie @gifts, "Tie::File", $gifts, autochomp => 0; |
| 2126 | |
| 2127 | then the array C<@gifts> would appear to contain C<("Gold\n", |
| 2128 | "Frankincense\n", "Myrrh\n")>, or (on Win32 systems) C<("Gold\r\n", |
| 2129 | "Frankincense\r\n", "Myrrh\r\n")>. |
| 2130 | |
| 2131 | =head2 C<mode> |
| 2132 | |
| 2133 | Normally, the specified file will be opened for read and write access, |
| 2134 | and will be created if it does not exist. (That is, the flags |
| 2135 | C<O_RDWR | O_CREAT> are supplied in the C<open> call.) If you want to |
| 2136 | change this, you may supply alternative flags in the C<mode> option. |
| 2137 | See L<Fcntl> for a listing of available flags. |
| 2138 | For example: |
| 2139 | |
| 2140 | # open the file if it exists, but fail if it does not exist |
| 2141 | use Fcntl 'O_RDWR'; |
| 2142 | tie @array, 'Tie::File', $file, mode => O_RDWR; |
| 2143 | |
| 2144 | # create the file if it does not exist |
| 2145 | use Fcntl 'O_RDWR', 'O_CREAT'; |
| 2146 | tie @array, 'Tie::File', $file, mode => O_RDWR | O_CREAT; |
| 2147 | |
| 2148 | # open an existing file in read-only mode |
| 2149 | use Fcntl 'O_RDONLY'; |
| 2150 | tie @array, 'Tie::File', $file, mode => O_RDONLY; |
| 2151 | |
| 2152 | Opening the data file in write-only or append mode is not supported. |
| 2153 | |
| 2154 | =head2 C<memory> |
| 2155 | |
| 2156 | This is an upper limit on the amount of memory that C<Tie::File> will |
| 2157 | consume at any time while managing the file. This is used for two |
| 2158 | things: managing the I<read cache> and managing the I<deferred write |
| 2159 | buffer>. |
| 2160 | |
| 2161 | Records read in from the file are cached, to avoid having to re-read |
| 2162 | them repeatedly. If you read the same record twice, the first time it |
| 2163 | will be stored in memory, and the second time it will be fetched from |
| 2164 | the I<read cache>. The amount of data in the read cache will not |
| 2165 | exceed the value you specified for C<memory>. If C<Tie::File> wants |
| 2166 | to cache a new record, but the read cache is full, it will make room |
| 2167 | by expiring the least-recently visited records from the read cache. |
| 2168 | |
| 2169 | The default memory limit is 2Mib. You can adjust the maximum read |
| 2170 | cache size by supplying the C<memory> option. The argument is the |
| 2171 | desired cache size, in bytes. |
| 2172 | |
| 2173 | # I have a lot of memory, so use a large cache to speed up access |
| 2174 | tie @array, 'Tie::File', $file, memory => 20_000_000; |
| 2175 | |
| 2176 | Setting the memory limit to 0 will inhibit caching; records will be |
| 2177 | fetched from disk every time you examine them. |
| 2178 | |
| 2179 | The C<memory> value is not an absolute or exact limit on the memory |
| 2180 | used. C<Tie::File> objects contains some structures besides the read |
| 2181 | cache and the deferred write buffer, whose sizes are not charged |
| 2182 | against C<memory>. |
| 2183 | |
| 2184 | The cache itself consumes about 310 bytes per cached record, so if |
| 2185 | your file has many short records, you may want to decrease the cache |
| 2186 | memory limit, or else the cache overhead may exceed the size of the |
| 2187 | cached data. |
| 2188 | |
| 2189 | |
| 2190 | =head2 C<dw_size> |
| 2191 | |
| 2192 | (This is an advanced feature. Skip this section on first reading.) |
| 2193 | |
| 2194 | If you use deferred writing (See L<"Deferred Writing">, below) then |
| 2195 | data you write into the array will not be written directly to the |
| 2196 | file; instead, it will be saved in the I<deferred write buffer> to be |
| 2197 | written out later. Data in the deferred write buffer is also charged |
| 2198 | against the memory limit you set with the C<memory> option. |
| 2199 | |
| 2200 | You may set the C<dw_size> option to limit the amount of data that can |
| 2201 | be saved in the deferred write buffer. This limit may not exceed the |
| 2202 | total memory limit. For example, if you set C<dw_size> to 1000 and |
| 2203 | C<memory> to 2500, that means that no more than 1000 bytes of deferred |
| 2204 | writes will be saved up. The space available for the read cache will |
| 2205 | vary, but it will always be at least 1500 bytes (if the deferred write |
| 2206 | buffer is full) and it could grow as large as 2500 bytes (if the |
| 2207 | deferred write buffer is empty.) |
| 2208 | |
| 2209 | If you don't specify a C<dw_size>, it defaults to the entire memory |
| 2210 | limit. |
| 2211 | |
| 2212 | =head2 Option Format |
| 2213 | |
| 2214 | C<-mode> is a synonym for C<mode>. C<-recsep> is a synonym for |
| 2215 | C<recsep>. C<-memory> is a synonym for C<memory>. You get the |
| 2216 | idea. |
| 2217 | |
| 2218 | =head1 Public Methods |
| 2219 | |
| 2220 | The C<tie> call returns an object, say C<$o>. You may call |
| 2221 | |
| 2222 | $rec = $o->FETCH($n); |
| 2223 | $o->STORE($n, $rec); |
| 2224 | |
| 2225 | to fetch or store the record at line C<$n>, respectively; similarly |
| 2226 | the other tied array methods. (See L<perltie> for details.) You may |
| 2227 | also call the following methods on this object: |
| 2228 | |
| 2229 | =head2 C<flock> |
| 2230 | |
| 2231 | $o->flock(MODE) |
| 2232 | |
| 2233 | will lock the tied file. C<MODE> has the same meaning as the second |
| 2234 | argument to the Perl built-in C<flock> function; for example |
| 2235 | C<LOCK_SH> or C<LOCK_EX | LOCK_NB>. (These constants are provided by |
| 2236 | the C<use Fcntl ':flock'> declaration.) |
| 2237 | |
| 2238 | C<MODE> is optional; the default is C<LOCK_EX>. |
| 2239 | |
| 2240 | C<Tie::File> maintains an internal table of the byte offset of each |
| 2241 | record it has seen in the file. |
| 2242 | |
| 2243 | When you use C<flock> to lock the file, C<Tie::File> assumes that the |
| 2244 | read cache is no longer trustworthy, because another process might |
| 2245 | have modified the file since the last time it was read. Therefore, a |
| 2246 | successful call to C<flock> discards the contents of the read cache |
| 2247 | and the internal record offset table. |
| 2248 | |
| 2249 | C<Tie::File> promises that the following sequence of operations will |
| 2250 | be safe: |
| 2251 | |
| 2252 | my $o = tie @array, "Tie::File", $filename; |
| 2253 | $o->flock; |
| 2254 | |
| 2255 | In particular, C<Tie::File> will I<not> read or write the file during |
| 2256 | the C<tie> call. (Exception: Using C<mode =E<gt> O_TRUNC> will, of |
| 2257 | course, erase the file during the C<tie> call. If you want to do this |
| 2258 | safely, then open the file without C<O_TRUNC>, lock the file, and use |
| 2259 | C<@array = ()>.) |
| 2260 | |
| 2261 | The best way to unlock a file is to discard the object and untie the |
| 2262 | array. It is probably unsafe to unlock the file without also untying |
| 2263 | it, because if you do, changes may remain unwritten inside the object. |
| 2264 | That is why there is no shortcut for unlocking. If you really want to |
| 2265 | unlock the file prematurely, you know what to do; if you don't know |
| 2266 | what to do, then don't do it. |
| 2267 | |
| 2268 | All the usual warnings about file locking apply here. In particular, |
| 2269 | note that file locking in Perl is B<advisory>, which means that |
| 2270 | holding a lock will not prevent anyone else from reading, writing, or |
| 2271 | erasing the file; it only prevents them from getting another lock at |
| 2272 | the same time. Locks are analogous to green traffic lights: If you |
| 2273 | have a green light, that does not prevent the idiot coming the other |
| 2274 | way from plowing into you sideways; it merely guarantees to you that |
| 2275 | the idiot does not also have a green light at the same time. |
| 2276 | |
| 2277 | =head2 C<autochomp> |
| 2278 | |
| 2279 | my $old_value = $o->autochomp(0); # disable autochomp option |
| 2280 | my $old_value = $o->autochomp(1); # enable autochomp option |
| 2281 | |
| 2282 | my $ac = $o->autochomp(); # recover current value |
| 2283 | |
| 2284 | See L<"autochomp">, above. |
| 2285 | |
| 2286 | =head2 C<defer>, C<flush>, C<discard>, and C<autodefer> |
| 2287 | |
| 2288 | See L<"Deferred Writing">, below. |
| 2289 | |
| 2290 | =head2 C<offset> |
| 2291 | |
| 2292 | $off = $o->offset($n); |
| 2293 | |
| 2294 | This method returns the byte offset of the start of the C<$n>th record |
| 2295 | in the file. If there is no such record, it returns an undefined |
| 2296 | value. |
| 2297 | |
| 2298 | =head1 Tying to an already-opened filehandle |
| 2299 | |
| 2300 | If C<$fh> is a filehandle, such as is returned by C<IO::File> or one |
| 2301 | of the other C<IO> modules, you may use: |
| 2302 | |
| 2303 | tie @array, 'Tie::File', $fh, ...; |
| 2304 | |
| 2305 | Similarly if you opened that handle C<FH> with regular C<open> or |
| 2306 | C<sysopen>, you may use: |
| 2307 | |
| 2308 | tie @array, 'Tie::File', \*FH, ...; |
| 2309 | |
| 2310 | Handles that were opened write-only won't work. Handles that were |
| 2311 | opened read-only will work as long as you don't try to modify the |
| 2312 | array. Handles must be attached to seekable sources of data---that |
| 2313 | means no pipes or sockets. If C<Tie::File> can detect that you |
| 2314 | supplied a non-seekable handle, the C<tie> call will throw an |
| 2315 | exception. (On Unix systems, it can detect this.) |
| 2316 | |
| 2317 | Note that Tie::File will only close any filehandles that it opened |
| 2318 | internally. If you passed it a filehandle as above, you "own" the |
| 2319 | filehandle, and are responsible for closing it after you have untied |
| 2320 | the @array. |
| 2321 | |
| 2322 | =head1 Deferred Writing |
| 2323 | |
| 2324 | (This is an advanced feature. Skip this section on first reading.) |
| 2325 | |
| 2326 | Normally, modifying a C<Tie::File> array writes to the underlying file |
| 2327 | immediately. Every assignment like C<$a[3] = ...> rewrites as much of |
| 2328 | the file as is necessary; typically, everything from line 3 through |
| 2329 | the end will need to be rewritten. This is the simplest and most |
| 2330 | transparent behavior. Performance even for large files is reasonably |
| 2331 | good. |
| 2332 | |
| 2333 | However, under some circumstances, this behavior may be excessively |
| 2334 | slow. For example, suppose you have a million-record file, and you |
| 2335 | want to do: |
| 2336 | |
| 2337 | for (@FILE) { |
| 2338 | $_ = "> $_"; |
| 2339 | } |
| 2340 | |
| 2341 | The first time through the loop, you will rewrite the entire file, |
| 2342 | from line 0 through the end. The second time through the loop, you |
| 2343 | will rewrite the entire file from line 1 through the end. The third |
| 2344 | time through the loop, you will rewrite the entire file from line 2 to |
| 2345 | the end. And so on. |
| 2346 | |
| 2347 | If the performance in such cases is unacceptable, you may defer the |
| 2348 | actual writing, and then have it done all at once. The following loop |
| 2349 | will perform much better for large files: |
| 2350 | |
| 2351 | (tied @a)->defer; |
| 2352 | for (@a) { |
| 2353 | $_ = "> $_"; |
| 2354 | } |
| 2355 | (tied @a)->flush; |
| 2356 | |
| 2357 | If C<Tie::File>'s memory limit is large enough, all the writing will |
| 2358 | done in memory. Then, when you call C<-E<gt>flush>, the entire file |
| 2359 | will be rewritten in a single pass. |
| 2360 | |
| 2361 | (Actually, the preceding discussion is something of a fib. You don't |
| 2362 | need to enable deferred writing to get good performance for this |
| 2363 | common case, because C<Tie::File> will do it for you automatically |
| 2364 | unless you specifically tell it not to. See L<"autodeferring">, |
| 2365 | below.) |
| 2366 | |
| 2367 | Calling C<-E<gt>flush> returns the array to immediate-write mode. If |
| 2368 | you wish to discard the deferred writes, you may call C<-E<gt>discard> |
| 2369 | instead of C<-E<gt>flush>. Note that in some cases, some of the data |
| 2370 | will have been written already, and it will be too late for |
| 2371 | C<-E<gt>discard> to discard all the changes. Support for |
| 2372 | C<-E<gt>discard> may be withdrawn in a future version of C<Tie::File>. |
| 2373 | |
| 2374 | Deferred writes are cached in memory up to the limit specified by the |
| 2375 | C<dw_size> option (see above). If the deferred-write buffer is full |
| 2376 | and you try to write still more deferred data, the buffer will be |
| 2377 | flushed. All buffered data will be written immediately, the buffer |
| 2378 | will be emptied, and the now-empty space will be used for future |
| 2379 | deferred writes. |
| 2380 | |
| 2381 | If the deferred-write buffer isn't yet full, but the total size of the |
| 2382 | buffer and the read cache would exceed the C<memory> limit, the oldest |
| 2383 | records will be expired from the read cache until the total size is |
| 2384 | under the limit. |
| 2385 | |
| 2386 | C<push>, C<pop>, C<shift>, C<unshift>, and C<splice> cannot be |
| 2387 | deferred. When you perform one of these operations, any deferred data |
| 2388 | is written to the file and the operation is performed immediately. |
| 2389 | This may change in a future version. |
| 2390 | |
| 2391 | If you resize the array with deferred writing enabled, the file will |
| 2392 | be resized immediately, but deferred records will not be written. |
| 2393 | This has a surprising consequence: C<@a = (...)> erases the file |
| 2394 | immediately, but the writing of the actual data is deferred. This |
| 2395 | might be a bug. If it is a bug, it will be fixed in a future version. |
| 2396 | |
| 2397 | =head2 Autodeferring |
| 2398 | |
| 2399 | C<Tie::File> tries to guess when deferred writing might be helpful, |
| 2400 | and to turn it on and off automatically. |
| 2401 | |
| 2402 | for (@a) { |
| 2403 | $_ = "> $_"; |
| 2404 | } |
| 2405 | |
| 2406 | In this example, only the first two assignments will be done |
| 2407 | immediately; after this, all the changes to the file will be deferred |
| 2408 | up to the user-specified memory limit. |
| 2409 | |
| 2410 | You should usually be able to ignore this and just use the module |
| 2411 | without thinking about deferring. However, special applications may |
| 2412 | require fine control over which writes are deferred, or may require |
| 2413 | that all writes be immediate. To disable the autodeferment feature, |
| 2414 | use |
| 2415 | |
| 2416 | (tied @o)->autodefer(0); |
| 2417 | |
| 2418 | or |
| 2419 | |
| 2420 | tie @array, 'Tie::File', $file, autodefer => 0; |
| 2421 | |
| 2422 | |
| 2423 | Similarly, C<-E<gt>autodefer(1)> re-enables autodeferment, and |
| 2424 | C<-E<gt>autodefer()> recovers the current value of the autodefer setting. |
| 2425 | |
| 2426 | |
| 2427 | =head1 CONCURRENT ACCESS TO FILES |
| 2428 | |
| 2429 | Caching and deferred writing are inappropriate if you want the same |
| 2430 | file to be accessed simultaneously from more than one process. Other |
| 2431 | optimizations performed internally by this module are also |
| 2432 | incompatible with concurrent access. A future version of this module will |
| 2433 | support a C<concurrent =E<gt> 1> option that enables safe concurrent access. |
| 2434 | |
| 2435 | Previous versions of this documentation suggested using C<memory |
| 2436 | =E<gt> 0> for safe concurrent access. This was mistaken. Tie::File |
| 2437 | will not support safe concurrent access before version 0.98. |
| 2438 | |
| 2439 | =head1 CAVEATS |
| 2440 | |
| 2441 | (That's Latin for 'warnings'.) |
| 2442 | |
| 2443 | =over 4 |
| 2444 | |
| 2445 | =item * |
| 2446 | |
| 2447 | Reasonable effort was made to make this module efficient. Nevertheless, |
| 2448 | changing the size of a record in the middle of a large file will |
| 2449 | always be fairly slow, because everything after the new record must be |
| 2450 | moved. |
| 2451 | |
| 2452 | =item * |
| 2453 | |
| 2454 | The behavior of tied arrays is not precisely the same as for regular |
| 2455 | arrays. For example: |
| 2456 | |
| 2457 | # This DOES print "How unusual!" |
| 2458 | undef $a[10]; print "How unusual!\n" if defined $a[10]; |
| 2459 | |
| 2460 | C<undef>-ing a C<Tie::File> array element just blanks out the |
| 2461 | corresponding record in the file. When you read it back again, you'll |
| 2462 | get the empty string, so the supposedly-C<undef>'ed value will be |
| 2463 | defined. Similarly, if you have C<autochomp> disabled, then |
| 2464 | |
| 2465 | # This DOES print "How unusual!" if 'autochomp' is disabled |
| 2466 | undef $a[10]; |
| 2467 | print "How unusual!\n" if $a[10]; |
| 2468 | |
| 2469 | Because when C<autochomp> is disabled, C<$a[10]> will read back as |
| 2470 | C<"\n"> (or whatever the record separator string is.) |
| 2471 | |
| 2472 | There are other minor differences, particularly regarding C<exists> |
| 2473 | and C<delete>, but in general, the correspondence is extremely close. |
| 2474 | |
| 2475 | =item * |
| 2476 | |
| 2477 | I have supposed that since this module is concerned with file I/O, |
| 2478 | almost all normal use of it will be heavily I/O bound. This means |
| 2479 | that the time to maintain complicated data structures inside the |
| 2480 | module will be dominated by the time to actually perform the I/O. |
| 2481 | When there was an opportunity to spend CPU time to avoid doing I/O, I |
| 2482 | usually tried to take it. |
| 2483 | |
| 2484 | =item * |
| 2485 | |
| 2486 | You might be tempted to think that deferred writing is like |
| 2487 | transactions, with C<flush> as C<commit> and C<discard> as |
| 2488 | C<rollback>, but it isn't, so don't. |
| 2489 | |
| 2490 | =item * |
| 2491 | |
| 2492 | There is a large memory overhead for each record offset and for each |
| 2493 | cache entry: about 310 bytes per cached data record, and about 21 bytes per offset table entry. |
| 2494 | |
| 2495 | The per-record overhead will limit the maximum number of records you |
| 2496 | can access per file. Note that I<accessing> the length of the array |
| 2497 | via C<$x = scalar @tied_file> accesses B<all> records and stores their |
| 2498 | offsets. The same for C<foreach (@tied_file)>, even if you exit the |
| 2499 | loop early. |
| 2500 | |
| 2501 | =back |
| 2502 | |
| 2503 | =head1 SUBCLASSING |
| 2504 | |
| 2505 | This version promises absolutely nothing about the internals, which |
| 2506 | may change without notice. A future version of the module will have a |
| 2507 | well-defined and stable subclassing API. |
| 2508 | |
| 2509 | =head1 WHAT ABOUT C<DB_File>? |
| 2510 | |
| 2511 | People sometimes point out that L<DB_File> will do something similar, |
| 2512 | and ask why C<Tie::File> module is necessary. |
| 2513 | |
| 2514 | There are a number of reasons that you might prefer C<Tie::File>. |
| 2515 | A list is available at C<http://perl.plover.com/TieFile/why-not-DB_File>. |
| 2516 | |
| 2517 | =head1 AUTHOR |
| 2518 | |
| 2519 | Mark Jason Dominus |
| 2520 | |
| 2521 | To contact the author, send email to: C<mjd-perl-tiefile+@plover.com> |
| 2522 | |
| 2523 | To receive an announcement whenever a new version of this module is |
| 2524 | released, send a blank email message to |
| 2525 | C<mjd-perl-tiefile-subscribe@plover.com>. |
| 2526 | |
| 2527 | The most recent version of this module, including documentation and |
| 2528 | any news of importance, will be available at |
| 2529 | |
| 2530 | http://perl.plover.com/TieFile/ |
| 2531 | |
| 2532 | |
| 2533 | =head1 LICENSE |
| 2534 | |
| 2535 | C<Tie::File> version 0.97 is copyright (C) 2003 Mark Jason Dominus. |
| 2536 | |
| 2537 | This library is free software; you may redistribute it and/or modify |
| 2538 | it under the same terms as Perl itself. |
| 2539 | |
| 2540 | These terms are your choice of any of (1) the Perl Artistic Licence, |
| 2541 | or (2) version 2 of the GNU General Public License as published by the |
| 2542 | Free Software Foundation, or (3) any later version of the GNU General |
| 2543 | Public License. |
| 2544 | |
| 2545 | This library is distributed in the hope that it will be useful, |
| 2546 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 2547 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 2548 | GNU General Public License for more details. |
| 2549 | |
| 2550 | You should have received a copy of the GNU General Public License |
| 2551 | along with this library program; it should be in the file C<COPYING>. |
| 2552 | If not, write to the Free Software Foundation, Inc., 59 Temple Place, |
| 2553 | Suite 330, Boston, MA 02111 USA |
| 2554 | |
| 2555 | For licensing inquiries, contact the author at: |
| 2556 | |
| 2557 | Mark Jason Dominus |
| 2558 | 255 S. Warnock St. |
| 2559 | Philadelphia, PA 19107 |
| 2560 | |
| 2561 | =head1 WARRANTY |
| 2562 | |
| 2563 | C<Tie::File> version 0.97 comes with ABSOLUTELY NO WARRANTY. |
| 2564 | For details, see the license. |
| 2565 | |
| 2566 | =head1 THANKS |
| 2567 | |
| 2568 | Gigantic thanks to Jarkko Hietaniemi, for agreeing to put this in the |
| 2569 | core when I hadn't written it yet, and for generally being helpful, |
| 2570 | supportive, and competent. (Usually the rule is "choose any one.") |
| 2571 | Also big thanks to Abhijit Menon-Sen for all of the same things. |
| 2572 | |
| 2573 | Special thanks to Craig Berry and Peter Prymmer (for VMS portability |
| 2574 | help), Randy Kobes (for Win32 portability help), Clinton Pierce and |
| 2575 | Autrijus Tang (for heroic eleventh-hour Win32 testing above and beyond |
| 2576 | the call of duty), Michael G Schwern (for testing advice), and the |
| 2577 | rest of the CPAN testers (for testing generally). |
| 2578 | |
| 2579 | Special thanks to Tels for suggesting several speed and memory |
| 2580 | optimizations. |
| 2581 | |
| 2582 | Additional thanks to: |
| 2583 | Edward Avis / |
| 2584 | Mattia Barbon / |
| 2585 | Tom Christiansen / |
| 2586 | Gerrit Haase / |
| 2587 | Gurusamy Sarathy / |
| 2588 | Jarkko Hietaniemi (again) / |
| 2589 | Nikola Knezevic / |
| 2590 | John Kominetz / |
| 2591 | Nick Ing-Simmons / |
| 2592 | Tassilo von Parseval / |
| 2593 | H. Dieter Pearcey / |
| 2594 | Slaven Rezic / |
| 2595 | Eric Roode / |
| 2596 | Peter Scott / |
| 2597 | Peter Somu / |
| 2598 | Autrijus Tang (again) / |
| 2599 | Tels (again) / |
| 2600 | Juerd Waalboer |
| 2601 | |
| 2602 | =head1 TODO |
| 2603 | |
| 2604 | More tests. (Stuff I didn't think of yet.) |
| 2605 | |
| 2606 | Paragraph mode? |
| 2607 | |
| 2608 | Fixed-length mode. Leave-blanks mode. |
| 2609 | |
| 2610 | Maybe an autolocking mode? |
| 2611 | |
| 2612 | For many common uses of the module, the read cache is a liability. |
| 2613 | For example, a program that inserts a single record, or that scans the |
| 2614 | file once, will have a cache hit rate of zero. This suggests a major |
| 2615 | optimization: The cache should be initially disabled. Here's a hybrid |
| 2616 | approach: Initially, the cache is disabled, but the cache code |
| 2617 | maintains statistics about how high the hit rate would be *if* it were |
| 2618 | enabled. When it sees the hit rate get high enough, it enables |
| 2619 | itself. The STAT comments in this code are the beginning of an |
| 2620 | implementation of this. |
| 2621 | |
| 2622 | Record locking with fcntl()? Then the module might support an undo |
| 2623 | log and get real transactions. What a tour de force that would be. |
| 2624 | |
| 2625 | Keeping track of the highest cached record. This would allow reads-in-a-row |
| 2626 | to skip the cache lookup faster (if reading from 1..N with empty cache at |
| 2627 | start, the last cached value will be always N-1). |
| 2628 | |
| 2629 | More tests. |
| 2630 | |
| 2631 | =cut |
| 2632 | |