| 1 | # File : Zlib.pm |
| 2 | # Author : Paul Marquess |
| 3 | # Created : 14 January 2004 |
| 4 | # Version : 1.33 |
| 5 | # |
| 6 | # Copyright (c) 1995-2004 Paul Marquess. All rights reserved. |
| 7 | # This program is free software; you can redistribute it and/or |
| 8 | # modify it under the same terms as Perl itself. |
| 9 | # |
| 10 | |
| 11 | package Compress::Zlib; |
| 12 | |
| 13 | require 5.004 ; |
| 14 | require Exporter; |
| 15 | require DynaLoader; |
| 16 | use AutoLoader; |
| 17 | use Carp ; |
| 18 | use IO::Handle ; |
| 19 | |
| 20 | use strict ; |
| 21 | use warnings ; |
| 22 | our ($VERSION, @ISA, @EXPORT, $AUTOLOAD); |
| 23 | our ($deflateDefault, $deflateParamsDefault, $inflateDefault); |
| 24 | |
| 25 | $VERSION = "1.33" ; |
| 26 | |
| 27 | @ISA = qw(Exporter DynaLoader); |
| 28 | # Items to export into callers namespace by default. Note: do not export |
| 29 | # names by default without a very good reason. Use EXPORT_OK instead. |
| 30 | # Do not simply export all your public functions/methods/constants. |
| 31 | @EXPORT = qw( |
| 32 | deflateInit |
| 33 | inflateInit |
| 34 | |
| 35 | compress |
| 36 | uncompress |
| 37 | |
| 38 | gzip gunzip |
| 39 | |
| 40 | gzopen |
| 41 | $gzerrno |
| 42 | |
| 43 | adler32 |
| 44 | crc32 |
| 45 | |
| 46 | ZLIB_VERSION |
| 47 | |
| 48 | DEF_WBITS |
| 49 | OS_CODE |
| 50 | |
| 51 | MAX_MEM_LEVEL |
| 52 | MAX_WBITS |
| 53 | |
| 54 | Z_ASCII |
| 55 | Z_BEST_COMPRESSION |
| 56 | Z_BEST_SPEED |
| 57 | Z_BINARY |
| 58 | Z_BUF_ERROR |
| 59 | Z_DATA_ERROR |
| 60 | Z_DEFAULT_COMPRESSION |
| 61 | Z_DEFAULT_STRATEGY |
| 62 | Z_DEFLATED |
| 63 | Z_ERRNO |
| 64 | Z_FILTERED |
| 65 | Z_FINISH |
| 66 | Z_FULL_FLUSH |
| 67 | Z_HUFFMAN_ONLY |
| 68 | Z_MEM_ERROR |
| 69 | Z_NEED_DICT |
| 70 | Z_NO_COMPRESSION |
| 71 | Z_NO_FLUSH |
| 72 | Z_NULL |
| 73 | Z_OK |
| 74 | Z_PARTIAL_FLUSH |
| 75 | Z_STREAM_END |
| 76 | Z_STREAM_ERROR |
| 77 | Z_SYNC_FLUSH |
| 78 | Z_UNKNOWN |
| 79 | Z_VERSION_ERROR |
| 80 | ); |
| 81 | |
| 82 | |
| 83 | |
| 84 | sub AUTOLOAD { |
| 85 | my($constname); |
| 86 | ($constname = $AUTOLOAD) =~ s/.*:://; |
| 87 | my ($error, $val) = constant($constname); |
| 88 | Carp::croak $error if $error; |
| 89 | no strict 'refs'; |
| 90 | *{$AUTOLOAD} = sub { $val }; |
| 91 | goto &{$AUTOLOAD}; |
| 92 | } |
| 93 | |
| 94 | bootstrap Compress::Zlib $VERSION ; |
| 95 | |
| 96 | # Preloaded methods go here. |
| 97 | |
| 98 | sub isaFilehandle($) |
| 99 | { |
| 100 | my $fh = shift ; |
| 101 | |
| 102 | return ((UNIVERSAL::isa($fh,'GLOB') or UNIVERSAL::isa(\$fh,'GLOB')) |
| 103 | and defined fileno($fh) ) |
| 104 | |
| 105 | } |
| 106 | |
| 107 | sub isaFilename($) |
| 108 | { |
| 109 | my $name = shift ; |
| 110 | |
| 111 | return (! ref $name and UNIVERSAL::isa(\$name, 'SCALAR')) ; |
| 112 | } |
| 113 | |
| 114 | sub gzopen($$) |
| 115 | { |
| 116 | my ($file, $mode) = @_ ; |
| 117 | |
| 118 | if (isaFilehandle $file) { |
| 119 | IO::Handle::flush($file) ; |
| 120 | my $offset = -f $file ? tell($file) : -1 ; |
| 121 | gzdopen_(fileno($file), $mode, $offset) ; |
| 122 | } |
| 123 | elsif (isaFilename $file) { |
| 124 | gzopen_($file, $mode) |
| 125 | } |
| 126 | else { |
| 127 | croak "gzopen: file parameter is not a filehandle or filename" |
| 128 | } |
| 129 | } |
| 130 | |
| 131 | sub ParseParameters($@) |
| 132 | { |
| 133 | my ($default, @rest) = @_ ; |
| 134 | my (%got) = %$default ; |
| 135 | my (@Bad) ; |
| 136 | my ($key, $value) ; |
| 137 | my $sub = (caller(1))[3] ; |
| 138 | my %options = () ; |
| 139 | |
| 140 | # allow the options to be passed as a hash reference or |
| 141 | # as the complete hash. |
| 142 | if (@rest == 1) { |
| 143 | |
| 144 | croak "$sub: parameter is not a reference to a hash" |
| 145 | if ref $rest[0] ne "HASH" ; |
| 146 | |
| 147 | %options = %{ $rest[0] } ; |
| 148 | } |
| 149 | elsif (@rest >= 2) { |
| 150 | my $count = @rest; |
| 151 | croak "$sub: Expected even number of parameters, got $count" |
| 152 | if @rest % 2 != 0 ; |
| 153 | %options = @rest ; |
| 154 | } |
| 155 | |
| 156 | while (($key, $value) = each %options) |
| 157 | { |
| 158 | $key =~ s/^-// ; |
| 159 | |
| 160 | if (exists $default->{$key}) |
| 161 | { $got{$key} = $value } |
| 162 | else |
| 163 | { push (@Bad, $key) } |
| 164 | } |
| 165 | |
| 166 | if (@Bad) { |
| 167 | my ($bad) = join(", ", @Bad) ; |
| 168 | croak "unknown key value(s) @Bad" ; |
| 169 | } |
| 170 | |
| 171 | return \%got ; |
| 172 | } |
| 173 | |
| 174 | $deflateDefault = { |
| 175 | 'Level' => Z_DEFAULT_COMPRESSION(), |
| 176 | 'Method' => Z_DEFLATED(), |
| 177 | 'WindowBits' => MAX_WBITS(), |
| 178 | 'MemLevel' => MAX_MEM_LEVEL(), |
| 179 | 'Strategy' => Z_DEFAULT_STRATEGY(), |
| 180 | 'Bufsize' => 4096, |
| 181 | 'Dictionary' => "", |
| 182 | } ; |
| 183 | |
| 184 | $deflateParamsDefault = { |
| 185 | 'Level' => undef, |
| 186 | 'Strategy' => undef, |
| 187 | 'Bufsize' => undef, |
| 188 | } ; |
| 189 | |
| 190 | $inflateDefault = { |
| 191 | 'WindowBits' => MAX_WBITS(), |
| 192 | 'Bufsize' => 4096, |
| 193 | 'Dictionary' => "", |
| 194 | } ; |
| 195 | |
| 196 | |
| 197 | sub deflateInit(@) |
| 198 | { |
| 199 | my ($got) = ParseParameters($deflateDefault, @_) ; |
| 200 | no warnings; |
| 201 | croak "deflateInit: Bufsize must be >= 1, you specified $got->{Bufsize}" |
| 202 | unless $got->{Bufsize} >= 1; |
| 203 | _deflateInit($got->{Level}, $got->{Method}, $got->{WindowBits}, |
| 204 | $got->{MemLevel}, $got->{Strategy}, $got->{Bufsize}, |
| 205 | $got->{Dictionary}) ; |
| 206 | |
| 207 | } |
| 208 | |
| 209 | sub inflateInit(@) |
| 210 | { |
| 211 | my ($got) = ParseParameters($inflateDefault, @_) ; |
| 212 | no warnings; |
| 213 | croak "inflateInit: Bufsize must be >= 1, you specified $got->{Bufsize}" |
| 214 | unless $got->{Bufsize} >= 1; |
| 215 | _inflateInit($got->{WindowBits}, $got->{Bufsize}, $got->{Dictionary}); |
| 216 | |
| 217 | } |
| 218 | |
| 219 | sub Compress::Zlib::deflateStream::deflateParams |
| 220 | { |
| 221 | my $self = shift ; |
| 222 | my ($got) = ParseParameters($deflateParamsDefault, @_) ; |
| 223 | croak "deflateParams needs Level and/or Strategy" |
| 224 | unless defined $got->{Level} || defined $got->{Strategy}; |
| 225 | no warnings; |
| 226 | croak "deflateParams: Bufsize must be >= 1, you specified $got->{Bufsize}" |
| 227 | unless !defined $got->{Bufsize} || $got->{Bufsize} >= 1; |
| 228 | |
| 229 | my $flags = 0; |
| 230 | if (defined $got->{Level}) |
| 231 | { $flags |= 1 } |
| 232 | else |
| 233 | { $got->{Level} = 0 } |
| 234 | |
| 235 | if (defined $got->{Strategy}) |
| 236 | { $flags |= 2 } |
| 237 | else |
| 238 | { $got->{Strategy} = 0 } |
| 239 | |
| 240 | $got->{Bufsize} = 0 |
| 241 | if !defined $got->{Bufsize}; |
| 242 | |
| 243 | $self->_deflateParams($flags, $got->{Level}, $got->{Strategy}, |
| 244 | $got->{Bufsize}); |
| 245 | |
| 246 | } |
| 247 | |
| 248 | sub compress($;$) |
| 249 | { |
| 250 | my ($x, $output, $out, $err, $in) ; |
| 251 | |
| 252 | if (ref $_[0] ) { |
| 253 | $in = $_[0] ; |
| 254 | croak "not a scalar reference" unless ref $in eq 'SCALAR' ; |
| 255 | } |
| 256 | else { |
| 257 | $in = \$_[0] ; |
| 258 | } |
| 259 | |
| 260 | my $level = (@_ == 2 ? $_[1] : Z_DEFAULT_COMPRESSION() ); |
| 261 | |
| 262 | |
| 263 | if ( (($x, $err) = deflateInit(Level => $level))[1] == Z_OK()) { |
| 264 | |
| 265 | ($output, $err) = $x->deflate($in) ; |
| 266 | return undef unless $err == Z_OK() ; |
| 267 | |
| 268 | ($out, $err) = $x->flush() ; |
| 269 | return undef unless $err == Z_OK() ; |
| 270 | |
| 271 | return ($output . $out) ; |
| 272 | |
| 273 | } |
| 274 | |
| 275 | return undef ; |
| 276 | } |
| 277 | |
| 278 | |
| 279 | sub uncompress($) |
| 280 | { |
| 281 | my ($x, $output, $err, $in) ; |
| 282 | |
| 283 | if (ref $_[0] ) { |
| 284 | $in = $_[0] ; |
| 285 | croak "not a scalar reference" unless ref $in eq 'SCALAR' ; |
| 286 | } |
| 287 | else { |
| 288 | $in = \$_[0] ; |
| 289 | } |
| 290 | |
| 291 | if ( (($x, $err) = inflateInit())[1] == Z_OK()) { |
| 292 | |
| 293 | ($output, $err) = $x->__unc_inflate($in) ; |
| 294 | return undef unless $err == Z_STREAM_END() ; |
| 295 | |
| 296 | return $output ; |
| 297 | } |
| 298 | |
| 299 | return undef ; |
| 300 | } |
| 301 | |
| 302 | |
| 303 | # Constants |
| 304 | use constant MAGIC1 => 0x1f ; |
| 305 | use constant MAGIC2 => 0x8b ; |
| 306 | use constant OSCODE => 3 ; |
| 307 | |
| 308 | use constant FTEXT => 1 ; |
| 309 | use constant FHCRC => 2 ; |
| 310 | use constant FEXTRA => 4 ; |
| 311 | use constant FNAME => 8 ; |
| 312 | use constant FCOMMENT => 16 ; |
| 313 | use constant NULL => pack("C", 0) ; |
| 314 | use constant RESERVED => 0xE0 ; |
| 315 | |
| 316 | use constant MIN_HDR_SIZE => 10 ; # minimum gzip header size |
| 317 | |
| 318 | sub memGzip($) |
| 319 | { |
| 320 | my $x = deflateInit( |
| 321 | -Level => Z_BEST_COMPRESSION(), |
| 322 | -WindowBits => - MAX_WBITS(), |
| 323 | ) |
| 324 | or return undef ; |
| 325 | |
| 326 | # write a minimal gzip header |
| 327 | my(@m); |
| 328 | push @m, pack("C" . MIN_HDR_SIZE, |
| 329 | MAGIC1, MAGIC2, Z_DEFLATED(), 0,0,0,0,0,0, OSCODE) ; |
| 330 | |
| 331 | # if the deflation buffer isn't a reference, make it one |
| 332 | my $string = (ref $_[0] ? $_[0] : \$_[0]) ; |
| 333 | |
| 334 | my ($output, $status) = $x->deflate($string) ; |
| 335 | push @m, $output ; |
| 336 | $status == Z_OK() |
| 337 | or return undef ; |
| 338 | |
| 339 | ($output, $status) = $x->flush() ; |
| 340 | push @m, $output ; |
| 341 | $status == Z_OK() |
| 342 | or return undef ; |
| 343 | |
| 344 | push @m, pack("V V", crc32($string), $x->total_in()); |
| 345 | |
| 346 | return join "", @m; |
| 347 | } |
| 348 | |
| 349 | sub _removeGzipHeader($) |
| 350 | { |
| 351 | my $string = shift ; |
| 352 | |
| 353 | return Z_DATA_ERROR() |
| 354 | if length($$string) < MIN_HDR_SIZE ; |
| 355 | |
| 356 | my ($magic1, $magic2, $method, $flags, $time, $xflags, $oscode) = |
| 357 | unpack ('CCCCVCC', $$string); |
| 358 | |
| 359 | return Z_DATA_ERROR() |
| 360 | unless $magic1 == MAGIC1 and $magic2 == MAGIC2 and |
| 361 | $method == Z_DEFLATED() and !($flags & RESERVED()) ; |
| 362 | substr($$string, 0, MIN_HDR_SIZE) = '' ; |
| 363 | |
| 364 | # skip extra field |
| 365 | if ($flags & FEXTRA) |
| 366 | { |
| 367 | return Z_DATA_ERROR() |
| 368 | if length($$string) < 2 ; |
| 369 | |
| 370 | my ($extra_len) = unpack ('v', $$string); |
| 371 | $extra_len += 2; |
| 372 | return Z_DATA_ERROR() |
| 373 | if length($$string) < $extra_len ; |
| 374 | |
| 375 | substr($$string, 0, $extra_len) = ''; |
| 376 | } |
| 377 | |
| 378 | # skip orig name |
| 379 | if ($flags & FNAME) |
| 380 | { |
| 381 | my $name_end = index ($$string, NULL); |
| 382 | return Z_DATA_ERROR() |
| 383 | if $name_end == -1 ; |
| 384 | substr($$string, 0, $name_end + 1) = ''; |
| 385 | } |
| 386 | |
| 387 | # skip comment |
| 388 | if ($flags & FCOMMENT) |
| 389 | { |
| 390 | my $comment_end = index ($$string, NULL); |
| 391 | return Z_DATA_ERROR() |
| 392 | if $comment_end == -1 ; |
| 393 | substr($$string, 0, $comment_end + 1) = ''; |
| 394 | } |
| 395 | |
| 396 | # skip header crc |
| 397 | if ($flags & FHCRC) |
| 398 | { |
| 399 | return Z_DATA_ERROR() |
| 400 | if length ($$string) < 2 ; |
| 401 | substr($$string, 0, 2) = ''; |
| 402 | } |
| 403 | |
| 404 | return Z_OK(); |
| 405 | } |
| 406 | |
| 407 | |
| 408 | sub memGunzip($) |
| 409 | { |
| 410 | # if the buffer isn't a reference, make it one |
| 411 | my $string = (ref $_[0] ? $_[0] : \$_[0]); |
| 412 | |
| 413 | _removeGzipHeader($string) == Z_OK() |
| 414 | or return undef; |
| 415 | |
| 416 | my $bufsize = length $$string > 4096 ? length $$string : 4096 ; |
| 417 | my $x = inflateInit( -WindowBits => - MAX_WBITS(), |
| 418 | -Bufsize => $bufsize) |
| 419 | or return undef; |
| 420 | my ($output, $status) = $x->inflate($string); |
| 421 | return undef |
| 422 | unless $status == Z_STREAM_END(); |
| 423 | |
| 424 | if (length $$string >= 8) |
| 425 | { |
| 426 | my ($crc, $len) = unpack ("VV", substr($$string, 0, 8)); |
| 427 | substr($$string, 0, 8) = ''; |
| 428 | return undef |
| 429 | unless $len == length($output) and |
| 430 | $crc == crc32($output); |
| 431 | } |
| 432 | else |
| 433 | { |
| 434 | $$string = ''; |
| 435 | } |
| 436 | |
| 437 | return $output; |
| 438 | } |
| 439 | |
| 440 | # Autoload methods go after __END__, and are processed by the autosplit program. |
| 441 | |
| 442 | 1; |
| 443 | __END__ |
| 444 | |
| 445 | =cut |
| 446 | |
| 447 | =head1 NAME |
| 448 | |
| 449 | Compress::Zlib - Interface to zlib compression library |
| 450 | |
| 451 | =head1 SYNOPSIS |
| 452 | |
| 453 | use Compress::Zlib ; |
| 454 | |
| 455 | ($d, $status) = deflateInit( [OPT] ) ; |
| 456 | ($out, $status) = $d->deflate($buffer) ; |
| 457 | $status = $d->deflateParams([OPT]) ; |
| 458 | ($out, $status) = $d->flush() ; |
| 459 | $d->dict_adler() ; |
| 460 | $d->total_in() ; |
| 461 | $d->total_out() ; |
| 462 | $d->msg() ; |
| 463 | |
| 464 | ($i, $status) = inflateInit( [OPT] ) ; |
| 465 | ($out, $status) = $i->inflate($buffer) ; |
| 466 | $status = $i->inflateSync($buffer) ; |
| 467 | $i->dict_adler() ; |
| 468 | $i->total_in() ; |
| 469 | $i->total_out() ; |
| 470 | $i->msg() ; |
| 471 | |
| 472 | $dest = compress($source, [$level]) ; |
| 473 | $dest = uncompress($source) ; |
| 474 | |
| 475 | $gz = gzopen($filename or filehandle, $mode) ; |
| 476 | $bytesread = $gz->gzread($buffer [,$size]) ; |
| 477 | $bytesread = $gz->gzreadline($line) ; |
| 478 | $byteswritten = $gz->gzwrite($buffer) ; |
| 479 | $status = $gz->gzflush($flush) ; |
| 480 | $status = $gz->gzclose() ; |
| 481 | $status = $gz->gzeof() ; |
| 482 | $status = $gz->gzsetparams($level, $strategy) ; |
| 483 | $errstring = $gz->gzerror() ; |
| 484 | $gzerrno |
| 485 | |
| 486 | $dest = Compress::Zlib::memGzip($buffer) ; |
| 487 | $dest = Compress::Zlib::memGunzip($buffer) ; |
| 488 | |
| 489 | $crc = adler32($buffer [,$crc]) ; |
| 490 | $crc = crc32($buffer [,$crc]) ; |
| 491 | |
| 492 | ZLIB_VERSION |
| 493 | |
| 494 | =head1 DESCRIPTION |
| 495 | |
| 496 | The I<Compress::Zlib> module provides a Perl interface to the I<zlib> |
| 497 | compression library (see L</AUTHOR> for details about where to get |
| 498 | I<zlib>). Most of the functionality provided by I<zlib> is available |
| 499 | in I<Compress::Zlib>. |
| 500 | |
| 501 | The module can be split into two general areas of functionality, namely |
| 502 | in-memory compression/decompression and read/write access to I<gzip> |
| 503 | files. Each of these areas will be discussed separately below. |
| 504 | |
| 505 | =head1 DEFLATE |
| 506 | |
| 507 | The interface I<Compress::Zlib> provides to the in-memory I<deflate> |
| 508 | (and I<inflate>) functions has been modified to fit into a Perl model. |
| 509 | |
| 510 | The main difference is that for both inflation and deflation, the Perl |
| 511 | interface will I<always> consume the complete input buffer before |
| 512 | returning. Also the output buffer returned will be automatically grown |
| 513 | to fit the amount of output available. |
| 514 | |
| 515 | Here is a definition of the interface available: |
| 516 | |
| 517 | |
| 518 | =head2 B<($d, $status) = deflateInit( [OPT] )> |
| 519 | |
| 520 | Initialises a deflation stream. |
| 521 | |
| 522 | It combines the features of the I<zlib> functions B<deflateInit>, |
| 523 | B<deflateInit2> and B<deflateSetDictionary>. |
| 524 | |
| 525 | If successful, it will return the initialised deflation stream, B<$d> |
| 526 | and B<$status> of C<Z_OK> in a list context. In scalar context it |
| 527 | returns the deflation stream, B<$d>, only. |
| 528 | |
| 529 | If not successful, the returned deflation stream (B<$d>) will be |
| 530 | I<undef> and B<$status> will hold the exact I<zlib> error code. |
| 531 | |
| 532 | The function optionally takes a number of named options specified as |
| 533 | C<-Name=E<gt>value> pairs. This allows individual options to be |
| 534 | tailored without having to specify them all in the parameter list. |
| 535 | |
| 536 | For backward compatibility, it is also possible to pass the parameters |
| 537 | as a reference to a hash containing the name=>value pairs. |
| 538 | |
| 539 | The function takes one optional parameter, a reference to a hash. The |
| 540 | contents of the hash allow the deflation interface to be tailored. |
| 541 | |
| 542 | Here is a list of the valid options: |
| 543 | |
| 544 | =over 5 |
| 545 | |
| 546 | =item B<-Level> |
| 547 | |
| 548 | Defines the compression level. Valid values are 0 through 9, |
| 549 | C<Z_NO_COMPRESSION>, C<Z_BEST_SPEED>, C<Z_BEST_COMPRESSION>, and |
| 550 | C<Z_DEFAULT_COMPRESSION>. |
| 551 | |
| 552 | The default is C<-Level =E<gt>Z_DEFAULT_COMPRESSION>. |
| 553 | |
| 554 | =item B<-Method> |
| 555 | |
| 556 | Defines the compression method. The only valid value at present (and |
| 557 | the default) is C<-Method =E<gt>Z_DEFLATED>. |
| 558 | |
| 559 | =item B<-WindowBits> |
| 560 | |
| 561 | For a definition of the meaning and valid values for B<WindowBits> |
| 562 | refer to the I<zlib> documentation for I<deflateInit2>. |
| 563 | |
| 564 | Defaults to C<-WindowBits =E<gt>MAX_WBITS>. |
| 565 | |
| 566 | =item B<-MemLevel> |
| 567 | |
| 568 | For a definition of the meaning and valid values for B<MemLevel> |
| 569 | refer to the I<zlib> documentation for I<deflateInit2>. |
| 570 | |
| 571 | Defaults to C<-MemLevel =E<gt>MAX_MEM_LEVEL>. |
| 572 | |
| 573 | =item B<-Strategy> |
| 574 | |
| 575 | Defines the strategy used to tune the compression. The valid values are |
| 576 | C<Z_DEFAULT_STRATEGY>, C<Z_FILTERED> and C<Z_HUFFMAN_ONLY>. |
| 577 | |
| 578 | The default is C<-Strategy =E<gt>Z_DEFAULT_STRATEGY>. |
| 579 | |
| 580 | =item B<-Dictionary> |
| 581 | |
| 582 | When a dictionary is specified I<Compress::Zlib> will automatically |
| 583 | call B<deflateSetDictionary> directly after calling B<deflateInit>. The |
| 584 | Adler32 value for the dictionary can be obtained by calling the method |
| 585 | C<$d->dict_adler()>. |
| 586 | |
| 587 | The default is no dictionary. |
| 588 | |
| 589 | =item B<-Bufsize> |
| 590 | |
| 591 | Sets the initial size for the deflation buffer. If the buffer has to be |
| 592 | reallocated to increase the size, it will grow in increments of |
| 593 | B<Bufsize>. |
| 594 | |
| 595 | The default is 4096. |
| 596 | |
| 597 | =back |
| 598 | |
| 599 | Here is an example of using the B<deflateInit> optional parameter list |
| 600 | to override the default buffer size and compression level. All other |
| 601 | options will take their default values. |
| 602 | |
| 603 | deflateInit( -Bufsize => 300, |
| 604 | -Level => Z_BEST_SPEED ) ; |
| 605 | |
| 606 | |
| 607 | =head2 B<($out, $status) = $d-E<gt>deflate($buffer)> |
| 608 | |
| 609 | |
| 610 | Deflates the contents of B<$buffer>. The buffer can either be a scalar |
| 611 | or a scalar reference. When finished, B<$buffer> will be |
| 612 | completely processed (assuming there were no errors). If the deflation |
| 613 | was successful it returns the deflated output, B<$out>, and a status |
| 614 | value, B<$status>, of C<Z_OK>. |
| 615 | |
| 616 | On error, B<$out> will be I<undef> and B<$status> will contain the |
| 617 | I<zlib> error code. |
| 618 | |
| 619 | In a scalar context B<deflate> will return B<$out> only. |
| 620 | |
| 621 | As with the I<deflate> function in I<zlib>, it is not necessarily the |
| 622 | case that any output will be produced by this method. So don't rely on |
| 623 | the fact that B<$out> is empty for an error test. |
| 624 | |
| 625 | |
| 626 | =head2 B<($out, $status) = $d-E<gt>flush([flush_type])> |
| 627 | |
| 628 | Typically used to finish the deflation. Any pending output will be |
| 629 | returned via B<$out>. |
| 630 | B<$status> will have a value C<Z_OK> if successful. |
| 631 | |
| 632 | In a scalar context B<flush> will return B<$out> only. |
| 633 | |
| 634 | Note that flushing can seriously degrade the compression ratio, so it |
| 635 | should only be used to terminate a decompression (using C<Z_FINISH>) or |
| 636 | when you want to create a I<full flush point> (using C<Z_FULL_FLUSH>). |
| 637 | |
| 638 | By default the C<flush_type> used is C<Z_FINISH>. Other valid values |
| 639 | for C<flush_type> are C<Z_NO_FLUSH>, C<Z_PARTIAL_FLUSH>, C<Z_SYNC_FLUSH> |
| 640 | and C<Z_FULL_FLUSH>. It is strongly recommended that you only set the |
| 641 | C<flush_type> parameter if you fully understand the implications of |
| 642 | what it does. See the C<zlib> documentation for details. |
| 643 | |
| 644 | =head2 B<$status = $d-E<gt>deflateParams([OPT])> |
| 645 | |
| 646 | Change settings for the deflate stream C<$d>. |
| 647 | |
| 648 | The list of the valid options is shown below. Options not specified |
| 649 | will remain unchanged. |
| 650 | |
| 651 | =over 5 |
| 652 | |
| 653 | =item B<-Level> |
| 654 | |
| 655 | Defines the compression level. Valid values are 0 through 9, |
| 656 | C<Z_NO_COMPRESSION>, C<Z_BEST_SPEED>, C<Z_BEST_COMPRESSION>, and |
| 657 | C<Z_DEFAULT_COMPRESSION>. |
| 658 | |
| 659 | =item B<-Strategy> |
| 660 | |
| 661 | Defines the strategy used to tune the compression. The valid values are |
| 662 | C<Z_DEFAULT_STRATEGY>, C<Z_FILTERED> and C<Z_HUFFMAN_ONLY>. |
| 663 | |
| 664 | =back |
| 665 | |
| 666 | =head2 B<$d-E<gt>dict_adler()> |
| 667 | |
| 668 | Returns the adler32 value for the dictionary. |
| 669 | |
| 670 | =head2 B<$d-E<gt>msg()> |
| 671 | |
| 672 | Returns the last error message generated by zlib. |
| 673 | |
| 674 | =head2 B<$d-E<gt>total_in()> |
| 675 | |
| 676 | Returns the total number of bytes uncompressed bytes input to deflate. |
| 677 | |
| 678 | =head2 B<$d-E<gt>total_out()> |
| 679 | |
| 680 | Returns the total number of compressed bytes output from deflate. |
| 681 | |
| 682 | =head2 Example |
| 683 | |
| 684 | |
| 685 | Here is a trivial example of using B<deflate>. It simply reads standard |
| 686 | input, deflates it and writes it to standard output. |
| 687 | |
| 688 | use strict ; |
| 689 | use warnings ; |
| 690 | |
| 691 | use Compress::Zlib ; |
| 692 | |
| 693 | binmode STDIN; |
| 694 | binmode STDOUT; |
| 695 | my $x = deflateInit() |
| 696 | or die "Cannot create a deflation stream\n" ; |
| 697 | |
| 698 | my ($output, $status) ; |
| 699 | while (<>) |
| 700 | { |
| 701 | ($output, $status) = $x->deflate($_) ; |
| 702 | |
| 703 | $status == Z_OK |
| 704 | or die "deflation failed\n" ; |
| 705 | |
| 706 | print $output ; |
| 707 | } |
| 708 | |
| 709 | ($output, $status) = $x->flush() ; |
| 710 | |
| 711 | $status == Z_OK |
| 712 | or die "deflation failed\n" ; |
| 713 | |
| 714 | print $output ; |
| 715 | |
| 716 | =head1 INFLATE |
| 717 | |
| 718 | Here is a definition of the interface: |
| 719 | |
| 720 | |
| 721 | =head2 B<($i, $status) = inflateInit()> |
| 722 | |
| 723 | Initialises an inflation stream. |
| 724 | |
| 725 | In a list context it returns the inflation stream, B<$i>, and the |
| 726 | I<zlib> status code (B<$status>). In a scalar context it returns the |
| 727 | inflation stream only. |
| 728 | |
| 729 | If successful, B<$i> will hold the inflation stream and B<$status> will |
| 730 | be C<Z_OK>. |
| 731 | |
| 732 | If not successful, B<$i> will be I<undef> and B<$status> will hold the |
| 733 | I<zlib> error code. |
| 734 | |
| 735 | The function optionally takes a number of named options specified as |
| 736 | C<-Name=E<gt>value> pairs. This allows individual options to be |
| 737 | tailored without having to specify them all in the parameter list. |
| 738 | |
| 739 | For backward compatibility, it is also possible to pass the parameters |
| 740 | as a reference to a hash containing the name=>value pairs. |
| 741 | |
| 742 | The function takes one optional parameter, a reference to a hash. The |
| 743 | contents of the hash allow the deflation interface to be tailored. |
| 744 | |
| 745 | Here is a list of the valid options: |
| 746 | |
| 747 | =over 5 |
| 748 | |
| 749 | =item B<-WindowBits> |
| 750 | |
| 751 | For a definition of the meaning and valid values for B<WindowBits> |
| 752 | refer to the I<zlib> documentation for I<inflateInit2>. |
| 753 | |
| 754 | Defaults to C<-WindowBits =E<gt>MAX_WBITS>. |
| 755 | |
| 756 | =item B<-Bufsize> |
| 757 | |
| 758 | Sets the initial size for the inflation buffer. If the buffer has to be |
| 759 | reallocated to increase the size, it will grow in increments of |
| 760 | B<Bufsize>. |
| 761 | |
| 762 | Default is 4096. |
| 763 | |
| 764 | =item B<-Dictionary> |
| 765 | |
| 766 | The default is no dictionary. |
| 767 | |
| 768 | =back |
| 769 | |
| 770 | Here is an example of using the B<inflateInit> optional parameter to |
| 771 | override the default buffer size. |
| 772 | |
| 773 | inflateInit( -Bufsize => 300 ) ; |
| 774 | |
| 775 | =head2 B<($out, $status) = $i-E<gt>inflate($buffer)> |
| 776 | |
| 777 | Inflates the complete contents of B<$buffer>. The buffer can either be |
| 778 | a scalar or a scalar reference. |
| 779 | |
| 780 | Returns C<Z_OK> if successful and C<Z_STREAM_END> if the end of the |
| 781 | compressed data has been successfully reached. |
| 782 | If not successful, B<$out> will be I<undef> and B<$status> will hold |
| 783 | the I<zlib> error code. |
| 784 | |
| 785 | The C<$buffer> parameter is modified by C<inflate>. On completion it |
| 786 | will contain what remains of the input buffer after inflation. This |
| 787 | means that C<$buffer> will be an empty string when the return status is |
| 788 | C<Z_OK>. When the return status is C<Z_STREAM_END> the C<$buffer> |
| 789 | parameter will contains what (if anything) was stored in the input |
| 790 | buffer after the deflated data stream. |
| 791 | |
| 792 | This feature is useful when processing a file format that encapsulates |
| 793 | a compressed data stream (e.g. gzip, zip). |
| 794 | |
| 795 | =head2 B<$status = $i-E<gt>inflateSync($buffer)> |
| 796 | |
| 797 | Scans C<$buffer> until it reaches either a I<full flush point> or the |
| 798 | end of the buffer. |
| 799 | |
| 800 | If a I<full flush point> is found, C<Z_OK> is returned and C<$buffer> |
| 801 | will be have all data up to the flush point removed. This can then be |
| 802 | passed to the C<deflate> method. |
| 803 | |
| 804 | Any other return code means that a flush point was not found. If more |
| 805 | data is available, C<inflateSync> can be called repeatedly with more |
| 806 | compressed data until the flush point is found. |
| 807 | |
| 808 | |
| 809 | =head2 B<$i-E<gt>dict_adler()> |
| 810 | |
| 811 | Returns the adler32 value for the dictionary. |
| 812 | |
| 813 | =head2 B<$i-E<gt>msg()> |
| 814 | |
| 815 | Returns the last error message generated by zlib. |
| 816 | |
| 817 | =head2 B<$i-E<gt>total_in()> |
| 818 | |
| 819 | Returns the total number of bytes compressed bytes input to inflate. |
| 820 | |
| 821 | =head2 B<$i-E<gt>total_out()> |
| 822 | |
| 823 | Returns the total number of uncompressed bytes output from inflate. |
| 824 | |
| 825 | =head2 Example |
| 826 | |
| 827 | Here is an example of using B<inflate>. |
| 828 | |
| 829 | use strict ; |
| 830 | use warnings ; |
| 831 | |
| 832 | use Compress::Zlib ; |
| 833 | |
| 834 | my $x = inflateInit() |
| 835 | or die "Cannot create a inflation stream\n" ; |
| 836 | |
| 837 | my $input = '' ; |
| 838 | binmode STDIN; |
| 839 | binmode STDOUT; |
| 840 | |
| 841 | my ($output, $status) ; |
| 842 | while (read(STDIN, $input, 4096)) |
| 843 | { |
| 844 | ($output, $status) = $x->inflate(\$input) ; |
| 845 | |
| 846 | print $output |
| 847 | if $status == Z_OK or $status == Z_STREAM_END ; |
| 848 | |
| 849 | last if $status != Z_OK ; |
| 850 | } |
| 851 | |
| 852 | die "inflation failed\n" |
| 853 | unless $status == Z_STREAM_END ; |
| 854 | |
| 855 | =head1 COMPRESS/UNCOMPRESS |
| 856 | |
| 857 | Two high-level functions are provided by I<zlib> to perform in-memory |
| 858 | compression. They are B<compress> and B<uncompress>. Two Perl subs are |
| 859 | provided which provide similar functionality. |
| 860 | |
| 861 | =over 5 |
| 862 | |
| 863 | =item B<$dest = compress($source [, $level] ) ;> |
| 864 | |
| 865 | Compresses B<$source>. If successful it returns the |
| 866 | compressed data. Otherwise it returns I<undef>. |
| 867 | |
| 868 | The source buffer can either be a scalar or a scalar reference. |
| 869 | |
| 870 | The B<$level> paramter defines the compression level. Valid values are |
| 871 | 0 through 9, C<Z_NO_COMPRESSION>, C<Z_BEST_SPEED>, |
| 872 | C<Z_BEST_COMPRESSION>, and C<Z_DEFAULT_COMPRESSION>. |
| 873 | If B<$level> is not specified C<Z_DEFAULT_COMPRESSION> will be used. |
| 874 | |
| 875 | |
| 876 | =item B<$dest = uncompress($source) ;> |
| 877 | |
| 878 | Uncompresses B<$source>. If successful it returns the uncompressed |
| 879 | data. Otherwise it returns I<undef>. |
| 880 | |
| 881 | The source buffer can either be a scalar or a scalar reference. |
| 882 | |
| 883 | =back |
| 884 | |
| 885 | =head1 GZIP INTERFACE |
| 886 | |
| 887 | A number of functions are supplied in I<zlib> for reading and writing |
| 888 | I<gzip> files. This module provides an interface to most of them. In |
| 889 | general the interface provided by this module operates identically to |
| 890 | the functions provided by I<zlib>. Any differences are explained |
| 891 | below. |
| 892 | |
| 893 | =over 5 |
| 894 | |
| 895 | =item B<$gz = gzopen(filename or filehandle, mode)> |
| 896 | |
| 897 | This function operates identically to the I<zlib> equivalent except |
| 898 | that it returns an object which is used to access the other I<gzip> |
| 899 | methods. |
| 900 | |
| 901 | As with the I<zlib> equivalent, the B<mode> parameter is used to |
| 902 | specify both whether the file is opened for reading or writing and to |
| 903 | optionally specify a a compression level. Refer to the I<zlib> |
| 904 | documentation for the exact format of the B<mode> parameter. |
| 905 | |
| 906 | If a reference to an open filehandle is passed in place of the |
| 907 | filename, gzdopen will be called behind the scenes. The third example |
| 908 | at the end of this section, I<gzstream>, uses this feature. |
| 909 | |
| 910 | =item B<$bytesread = $gz-E<gt>gzread($buffer [, $size]) ;> |
| 911 | |
| 912 | Reads B<$size> bytes from the compressed file into B<$buffer>. If |
| 913 | B<$size> is not specified, it will default to 4096. If the scalar |
| 914 | B<$buffer> is not large enough, it will be extended automatically. |
| 915 | |
| 916 | Returns the number of bytes actually read. On EOF it returns 0 and in |
| 917 | the case of an error, -1. |
| 918 | |
| 919 | =item B<$bytesread = $gz-E<gt>gzreadline($line) ;> |
| 920 | |
| 921 | Reads the next line from the compressed file into B<$line>. |
| 922 | |
| 923 | Returns the number of bytes actually read. On EOF it returns 0 and in |
| 924 | the case of an error, -1. |
| 925 | |
| 926 | It is legal to intermix calls to B<gzread> and B<gzreadline>. |
| 927 | |
| 928 | At this time B<gzreadline> ignores the variable C<$/> |
| 929 | (C<$INPUT_RECORD_SEPARATOR> or C<$RS> when C<English> is in use). The |
| 930 | end of a line is denoted by the C character C<'\n'>. |
| 931 | |
| 932 | =item B<$byteswritten = $gz-E<gt>gzwrite($buffer) ;> |
| 933 | |
| 934 | Writes the contents of B<$buffer> to the compressed file. Returns the |
| 935 | number of bytes actually written, or 0 on error. |
| 936 | |
| 937 | =item B<$status = $gz-E<gt>gzflush($flush) ;> |
| 938 | |
| 939 | Flushes all pending output to the compressed file. |
| 940 | Works identically to the I<zlib> function it interfaces to. Note that |
| 941 | the use of B<gzflush> can degrade compression. |
| 942 | |
| 943 | Returns C<Z_OK> if B<$flush> is C<Z_FINISH> and all output could be |
| 944 | flushed. Otherwise the zlib error code is returned. |
| 945 | |
| 946 | Refer to the I<zlib> documentation for the valid values of B<$flush>. |
| 947 | |
| 948 | =item B<$status = $gz-E<gt>gzeof() ;> |
| 949 | |
| 950 | Returns 1 if the end of file has been detected while reading the input |
| 951 | file, otherwise returns 0. |
| 952 | |
| 953 | =item B<$gz-E<gt>gzclose> |
| 954 | |
| 955 | Closes the compressed file. Any pending data is flushed to the file |
| 956 | before it is closed. |
| 957 | |
| 958 | =item B<$gz-E<gt>gzsetparams($level, $strategy> |
| 959 | |
| 960 | Change settings for the deflate stream C<$gz>. |
| 961 | |
| 962 | The list of the valid options is shown below. Options not specified |
| 963 | will remain unchanged. |
| 964 | |
| 965 | Note: This method is only available if you are running zlib 1.0.6 or better. |
| 966 | |
| 967 | =over 5 |
| 968 | |
| 969 | =item B<$level> |
| 970 | |
| 971 | Defines the compression level. Valid values are 0 through 9, |
| 972 | C<Z_NO_COMPRESSION>, C<Z_BEST_SPEED>, C<Z_BEST_COMPRESSION>, and |
| 973 | C<Z_DEFAULT_COMPRESSION>. |
| 974 | |
| 975 | =item B<$strategy> |
| 976 | |
| 977 | Defines the strategy used to tune the compression. The valid values are |
| 978 | C<Z_DEFAULT_STRATEGY>, C<Z_FILTERED> and C<Z_HUFFMAN_ONLY>. |
| 979 | |
| 980 | =back |
| 981 | |
| 982 | =item B<$gz-E<gt>gzerror> |
| 983 | |
| 984 | Returns the I<zlib> error message or number for the last operation |
| 985 | associated with B<$gz>. The return value will be the I<zlib> error |
| 986 | number when used in a numeric context and the I<zlib> error message |
| 987 | when used in a string context. The I<zlib> error number constants, |
| 988 | shown below, are available for use. |
| 989 | |
| 990 | Z_OK |
| 991 | Z_STREAM_END |
| 992 | Z_ERRNO |
| 993 | Z_STREAM_ERROR |
| 994 | Z_DATA_ERROR |
| 995 | Z_MEM_ERROR |
| 996 | Z_BUF_ERROR |
| 997 | |
| 998 | =item B<$gzerrno> |
| 999 | |
| 1000 | The B<$gzerrno> scalar holds the error code associated with the most |
| 1001 | recent I<gzip> routine. Note that unlike B<gzerror()>, the error is |
| 1002 | I<not> associated with a particular file. |
| 1003 | |
| 1004 | As with B<gzerror()> it returns an error number in numeric context and |
| 1005 | an error message in string context. Unlike B<gzerror()> though, the |
| 1006 | error message will correspond to the I<zlib> message when the error is |
| 1007 | associated with I<zlib> itself, or the UNIX error message when it is |
| 1008 | not (i.e. I<zlib> returned C<Z_ERRORNO>). |
| 1009 | |
| 1010 | As there is an overlap between the error numbers used by I<zlib> and |
| 1011 | UNIX, B<$gzerrno> should only be used to check for the presence of |
| 1012 | I<an> error in numeric context. Use B<gzerror()> to check for specific |
| 1013 | I<zlib> errors. The I<gzcat> example below shows how the variable can |
| 1014 | be used safely. |
| 1015 | |
| 1016 | =back |
| 1017 | |
| 1018 | |
| 1019 | =head2 Examples |
| 1020 | |
| 1021 | Here is an example script which uses the interface. It implements a |
| 1022 | I<gzcat> function. |
| 1023 | |
| 1024 | use strict ; |
| 1025 | use warnings ; |
| 1026 | |
| 1027 | use Compress::Zlib ; |
| 1028 | |
| 1029 | die "Usage: gzcat file...\n" |
| 1030 | unless @ARGV ; |
| 1031 | |
| 1032 | my $file ; |
| 1033 | |
| 1034 | foreach $file (@ARGV) { |
| 1035 | my $buffer ; |
| 1036 | |
| 1037 | my $gz = gzopen($file, "rb") |
| 1038 | or die "Cannot open $file: $gzerrno\n" ; |
| 1039 | |
| 1040 | print $buffer while $gz->gzread($buffer) > 0 ; |
| 1041 | |
| 1042 | die "Error reading from $file: $gzerrno" . ($gzerrno+0) . "\n" |
| 1043 | if $gzerrno != Z_STREAM_END ; |
| 1044 | |
| 1045 | $gz->gzclose() ; |
| 1046 | } |
| 1047 | |
| 1048 | Below is a script which makes use of B<gzreadline>. It implements a |
| 1049 | very simple I<grep> like script. |
| 1050 | |
| 1051 | use strict ; |
| 1052 | use warnings ; |
| 1053 | |
| 1054 | use Compress::Zlib ; |
| 1055 | |
| 1056 | die "Usage: gzgrep pattern file...\n" |
| 1057 | unless @ARGV >= 2; |
| 1058 | |
| 1059 | my $pattern = shift ; |
| 1060 | |
| 1061 | my $file ; |
| 1062 | |
| 1063 | foreach $file (@ARGV) { |
| 1064 | my $gz = gzopen($file, "rb") |
| 1065 | or die "Cannot open $file: $gzerrno\n" ; |
| 1066 | |
| 1067 | while ($gz->gzreadline($_) > 0) { |
| 1068 | print if /$pattern/ ; |
| 1069 | } |
| 1070 | |
| 1071 | die "Error reading from $file: $gzerrno\n" |
| 1072 | if $gzerrno != Z_STREAM_END ; |
| 1073 | |
| 1074 | $gz->gzclose() ; |
| 1075 | } |
| 1076 | |
| 1077 | This script, I<gzstream>, does the opposite of the I<gzcat> script |
| 1078 | above. It reads from standard input and writes a gzip file to standard |
| 1079 | output. |
| 1080 | |
| 1081 | use strict ; |
| 1082 | use warnings ; |
| 1083 | |
| 1084 | use Compress::Zlib ; |
| 1085 | |
| 1086 | binmode STDOUT; # gzopen only sets it on the fd |
| 1087 | |
| 1088 | my $gz = gzopen(\*STDOUT, "wb") |
| 1089 | or die "Cannot open stdout: $gzerrno\n" ; |
| 1090 | |
| 1091 | while (<>) { |
| 1092 | $gz->gzwrite($_) |
| 1093 | or die "error writing: $gzerrno\n" ; |
| 1094 | } |
| 1095 | |
| 1096 | $gz->gzclose ; |
| 1097 | |
| 1098 | =head2 Compress::Zlib::memGzip |
| 1099 | |
| 1100 | This function is used to create an in-memory gzip file. |
| 1101 | It creates a minimal gzip header. |
| 1102 | |
| 1103 | $dest = Compress::Zlib::memGzip($buffer) ; |
| 1104 | |
| 1105 | If successful, it returns the in-memory gzip file, otherwise it returns |
| 1106 | undef. |
| 1107 | |
| 1108 | The buffer parameter can either be a scalar or a scalar reference. |
| 1109 | |
| 1110 | =head2 Compress::Zlib::memGunzip |
| 1111 | |
| 1112 | This function is used to uncompress an in-memory gzip file. |
| 1113 | |
| 1114 | $dest = Compress::Zlib::memGunzip($buffer) ; |
| 1115 | |
| 1116 | If successful, it returns the uncompressed gzip file, otherwise it |
| 1117 | returns undef. |
| 1118 | |
| 1119 | The buffer parameter can either be a scalar or a scalar reference. The |
| 1120 | contents of the buffer parameter are destroyed after calling this |
| 1121 | function. |
| 1122 | |
| 1123 | =head1 CHECKSUM FUNCTIONS |
| 1124 | |
| 1125 | Two functions are provided by I<zlib> to calculate a checksum. For the |
| 1126 | Perl interface, the order of the two parameters in both functions has |
| 1127 | been reversed. This allows both running checksums and one off |
| 1128 | calculations to be done. |
| 1129 | |
| 1130 | $crc = adler32($buffer [,$crc]) ; |
| 1131 | $crc = crc32($buffer [,$crc]) ; |
| 1132 | |
| 1133 | The buffer parameters can either be a scalar or a scalar reference. |
| 1134 | |
| 1135 | If the $crc parameters is C<undef>, the crc value will be reset. |
| 1136 | |
| 1137 | =head1 ACCESSING ZIP FILES |
| 1138 | |
| 1139 | Although it is possible to use this module to access .zip files, there |
| 1140 | is a module on CPAN that will do all the hard work for you. Check out |
| 1141 | |
| 1142 | http://www.cpan.org/modules/by-module/Archive/Archive-Zip-*.tar.gz |
| 1143 | |
| 1144 | Assuming you don't want to use this module to access zip files there |
| 1145 | are a number of undocumented features in the zlib library you need to |
| 1146 | be aware of. |
| 1147 | |
| 1148 | =over 5 |
| 1149 | |
| 1150 | =item 1. |
| 1151 | |
| 1152 | When calling B<inflateInit> or B<deflateInit> the B<WindowBits> parameter |
| 1153 | must be set to C<-MAX_WBITS>. This disables the creation of the zlib |
| 1154 | header. |
| 1155 | |
| 1156 | =item 2. |
| 1157 | |
| 1158 | The zlib function B<inflate>, and so the B<inflate> method supplied in |
| 1159 | this module, assume that there is at least one trailing byte after the |
| 1160 | compressed data stream. Normally this isn't a problem because both |
| 1161 | the gzip and zip file formats will guarantee that there is data directly |
| 1162 | after the compressed data stream. |
| 1163 | |
| 1164 | =back |
| 1165 | |
| 1166 | =head1 CONSTANTS |
| 1167 | |
| 1168 | All the I<zlib> constants are automatically imported when you make use |
| 1169 | of I<Compress::Zlib>. |
| 1170 | |
| 1171 | =head1 AUTHOR |
| 1172 | |
| 1173 | The I<Compress::Zlib> module was written by Paul Marquess, |
| 1174 | F<pmqs@cpan.org>. The latest copy of the module can be |
| 1175 | found on CPAN in F<modules/by-module/Compress/Compress-Zlib-x.x.tar.gz>. |
| 1176 | |
| 1177 | The primary site for the I<zlib> compression library is |
| 1178 | F<http://www.zlib.org>. |
| 1179 | |
| 1180 | =head1 MODIFICATION HISTORY |
| 1181 | |
| 1182 | See the Changes file. |