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Diffstat (limited to 'usr.bin/tail/reverse.c')
| -rw-r--r-- | usr.bin/tail/reverse.c | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/usr.bin/tail/reverse.c b/usr.bin/tail/reverse.c new file mode 100644 index 0000000..34cd980 --- /dev/null +++ b/usr.bin/tail/reverse.c @@ -0,0 +1,259 @@ +/*- + * Copyright (c) 1991, 1993 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Edward Sze-Tyan Wang. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef lint +static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93"; +#endif /* not lint */ + +#include <sys/param.h> +#include <sys/stat.h> +#include <sys/mman.h> + +#include <limits.h> +#include <errno.h> +#include <unistd.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include "extern.h" + +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. + * + * BYTES display N bytes + * REG mmap the file and display the lines + * NOREG cyclically read characters into a wrap-around buffer + * + * LINES display N lines + * 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 + */ +void +reverse(fp, style, off, sbp) + FILE *fp; + enum STYLE style; + long off; + struct stat *sbp; +{ + if (style != REVERSE && off == 0) + return; + + if (S_ISREG(sbp->st_mode)) + r_reg(fp, style, off, sbp); + else + switch(style) { + case FBYTES: + case RBYTES: + bytes(fp, off); + break; + case FLINES: + case RLINES: + lines(fp, off); + break; + case REVERSE: + r_buf(fp); + break; + } +} + +/* + * r_reg -- display a regular file in reverse order by line. + */ +static void +r_reg(fp, style, off, sbp) + FILE *fp; + register enum STYLE style; + long off; + struct stat *sbp; +{ + register off_t size; + register int llen; + register char *p; + char *start; + + if (!(size = sbp->st_size)) + return; + + if (size > SIZE_T_MAX) { + err(0, "%s: %s", fname, strerror(EFBIG)); + return; + } + + 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)); + return; + } + p = start + size - 1; + + if (style == RBYTES && off < size) + size = off; + + /* Last char is special, ignore whether newline or not. */ + for (llen = 1; --size; ++llen) + if (*--p == '\n') { + WR(p + 1, llen); + llen = 0; + if (style == RLINES && !--off) { + ++p; + break; + } + } + if (llen) + WR(p, llen); + if (munmap(start, (size_t)sbp->st_size)) + err(0, "%s: %s", fname, strerror(errno)); +} + +typedef struct bf { + struct bf *next; + struct bf *prev; + int len; + char *l; +} BF; + +/* + * 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 + * user warned). + */ +static void +r_buf(fp) + FILE *fp; +{ + register BF *mark, *tl, *tr; + register int ch, len, llen; + register char *p; + off_t enomem; + +#define BSZ (128 * 1024) + 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 + * keep going. + */ + if (enomem || (tl = malloc(sizeof(BF))) == NULL || + (tl->l = malloc(BSZ)) == NULL) { + if (!mark) + err(1, "%s", strerror(errno)); + tl = enomem ? tl->next : mark; + enomem += tl->len; + } else if (mark) { + tl->next = mark; + tl->prev = mark->prev; + mark->prev->next = tl; + mark->prev = tl; + } else + mark->next = mark->prev = (mark = tl); + + /* Fill the block with input data. */ + for (p = tl->l, len = 0; + len < BSZ && (ch = getc(fp)) != EOF; ++len) + *p++ = ch; + + /* + * If no input data for this block and we tossed some data, + * recover it. + */ + if (!len) { + if (enomem) + enomem -= tl->len; + tl = tl->prev; + break; + } + + tl->len = len; + if (ch == EOF) + break; + } + + if (enomem) { + (void)fprintf(stderr, + "tail: warning: %ld bytes discarded\n", enomem); + rval = 1; + } + + /* + * Step through the blocks in the reverse order read. The last char + * is special, ignore whether newline or not. + */ + for (mark = tl;;) { + for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; + --p, ++llen) + if (*p == '\n') { + if (llen) { + WR(p + 1, llen); + llen = 0; + } + if (tl == mark) + continue; + for (tr = tl->next; tr->len; tr = tr->next) { + WR(tr->l, tr->len); + tr->len = 0; + if (tr == mark) + break; + } + } + tl->len = llen; + if ((tl = tl->prev) == mark) + break; + } + tl = tl->next; + if (tl->len) { + WR(tl->l, tl->len); + tl->len = 0; + } + while ((tl = tl->next)->len) { + WR(tl->l, tl->len); + tl->len = 0; + } +} |
