/* $OpenBSD: reverse.c,v 1.21 2015/11/19 17:50:04 tedu Exp $ */ /* $NetBSD: reverse.c,v 1.6 1994/11/23 07:42:10 jtc Exp $ */ /*- * 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. 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. */ #include <sys/stat.h> #include <err.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include "extern.h" static void r_buf(FILE *); static int r_reg(struct tailfile *, enum STYLE, off_t); #define COPYCHAR(tf, ch) \ do { \ if ((ch = getc(tf->fp)) == EOF) { \ ierr(tf->fname); \ return (0); \ } \ if (putchar(ch) == EOF) { \ oerr(); \ return (0); \ } \ } while (0) /* * 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 reverse scan and display the lines * NOREG cyclically read characters into a wrap-around buffer * * LINES display N lines * REG reverse scan and display the lines * NOREG cyclically read lines into a wrap-around array of buffers * * FILE display the entire file * REG reverse scan and display the lines * NOREG cyclically read input into a linked list of buffers */ void reverse(struct tailfile *tf, int nfiles, enum STYLE style, off_t off) { int i; if (style != REVERSE && off == 0) return; for (i = 0; i < nfiles; i++) { if (nfiles > 1) printfname(tf[i].fname); if (!S_ISREG(tf[i].sb.st_mode) || r_reg(&(tf[i]), style, off) != 0) { switch(style) { case FBYTES: case RBYTES: (void)bytes(&(tf[i]), off); break; case FLINES: case RLINES: (void)lines(&(tf[i]), off); break; case REVERSE: r_buf(tf[i].fp); break; default: err(1, "Unsupported style"); } } } } /* * r_reg -- display a regular file in reverse order by line. */ static int r_reg(struct tailfile *tf, enum STYLE style, off_t off) { off_t start, pos, end; int ch; end = tf->sb.st_size; if (end == 0) return (0); /* Position before char, ignore last char whether newline or not */ pos = end-2; ch = EOF; start = 0; if (style == RBYTES && off < end) start = end - off; for (; pos >= start; pos--) { /* A seek per char isn't a problem with a smart stdio */ if (fseeko(tf->fp, pos, SEEK_SET) != 0) { ierr(tf->fname); return (0); } if ((ch = getc(tf->fp)) == '\n') { while (--end > pos) COPYCHAR(tf, ch); end++; if (style == RLINES && --off == 0) break; } else if (ch == EOF) { ierr(tf->fname); return (0); } } if (pos < start) { if (ch != EOF && ungetc(ch, tf->fp) == EOF) { ierr(tf->fname); return (0); } while (--end >= start) COPYCHAR(tf, ch); } return (0); } #define BSZ (128 * 1024) struct bf { struct bf *next; struct bf *prev; size_t len; char l[BSZ]; }; /* * 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(FILE *fp) { struct bf *mark, *tr, *tl = NULL; int ch; size_t len, llen; char *p; off_t enomem; 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(*tl))) == NULL) { if (!mark) err(1, NULL); 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 = tl; mark->next = mark->prev = mark; } if (!enomem) tl->len = 0; /* 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: %lld bytes discarded\n", (long long)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; } tl->prev->next = NULL; while (tl != NULL) { tr = tl->next; free(tl); tl = tr; } }
