* Copyright (c) 1991 The Regents of the University of California.
* This code is derived from software contributed to Berkeley by
* %sccs.include.redist.c%
static char sccsid
[] = "@(#)reverse.c 5.8 (Berkeley) %G%";
static void r_buf
__P((FILE *));
static void r_reg
__P((FILE *, enum STYLE
, long, struct stat
*));
* reverse -- display input in reverse order by line.
* There are six separate cases for this -- regular and non-regular
* files by bytes, lines or the whole file.
* REG mmap the file and display the lines
* NOREG cyclically read characters into a wrap-around buffer
* REG mmap the file and display the lines
* NOREG cyclically read lines into a wrap-around array of buffers
* FILE display the entire file
* REG mmap the file and display the lines
* NOREG cyclically read input into a linked list of buffers
reverse(fp
, style
, off
, sbp
)
if (style
!= REVERSE
&& off
== 0)
if (S_ISREG(sbp
->st_mode
))
r_reg(fp
, style
, off
, sbp
);
* r_reg -- display a regular file in reverse order by line.
r_reg(fp
, style
, off
, sbp
)
register enum STYLE style
;
if (!(size
= sbp
->st_size
))
err(0, "%s: %s", fname
, strerror(EFBIG
));
if ((start
= mmap(NULL
, (size_t)size
,
PROT_READ
, 0, fileno(fp
), (off_t
)0)) == (caddr_t
)-1) {
err(0, "%s: %s", fname
, strerror(EFBIG
));
if (style
== RBYTES
&& off
< size
)
/* Last char is special, ignore whether newline or not. */
for (llen
= 1; --size
; ++llen
)
if (style
== RLINES
&& !--off
) {
if (munmap(start
, (size_t)sbp
->st_size
))
err(0, "%s: %s", fname
, strerror(errno
));
* r_buf -- display a non-regular file in reverse order by line.
* This is the function that saves the entire input, storing the data in a
* doubly linked list of buffers and then displays them in reverse order.
* It has the usual nastiness of trying to find the newlines, as there's no
* guarantee that a newline occurs anywhere in the file, let alone in any
* particular buffer. If we run out of memory, input is discarded (and the
register BF
*mark
, *tl
, *tr
;
register int ch
, len
, llen
;
for (mark
= NULL
, enomem
= 0;;) {
* Allocate a new block and link it into place in a doubly
* linked list. If out of memory, toss the LRU block and
if (enomem
|| (tl
= malloc(sizeof(BF
))) == NULL
||
(tl
->l
= malloc(BSZ
)) == NULL
) {
err(1, "%s", strerror(errno
));
tl
= enomem
? tl
->next
: mark
;
mark
->next
= mark
->prev
= (mark
= tl
);
/* Fill the block with input data. */
len
< BSZ
&& (ch
= getc(fp
)) != EOF
; ++len
)
* If no input data for this block and we tossed some data,
"tail: warning: %ld bytes discarded\n", enomem
);
* Step through the blocks in the reverse order read. The last char
* is special, ignore whether newline or not.
for (p
= tl
->l
+ (len
= tl
->len
) - 1, llen
= 0; len
--;
for (tr
= tl
->next
; tr
->len
; tr
= tr
->next
) {
if ((tl
= tl
->prev
) == mark
)
while ((tl
= tl
->next
)->len
) {