reverse.c revision 1590
11592Srgrimes/*- 21592Srgrimes * Copyright (c) 1991, 1993 31592Srgrimes * The Regents of the University of California. All rights reserved. 41592Srgrimes * 51592Srgrimes * This code is derived from software contributed to Berkeley by 61592Srgrimes * Edward Sze-Tyan Wang. 71592Srgrimes * 81592Srgrimes * Redistribution and use in source and binary forms, with or without 91592Srgrimes * modification, are permitted provided that the following conditions 101592Srgrimes * are met: 111592Srgrimes * 1. Redistributions of source code must retain the above copyright 121592Srgrimes * notice, this list of conditions and the following disclaimer. 131592Srgrimes * 2. Redistributions in binary form must reproduce the above copyright 141592Srgrimes * notice, this list of conditions and the following disclaimer in the 151592Srgrimes * documentation and/or other materials provided with the distribution. 161592Srgrimes * 3. All advertising materials mentioning features or use of this software 171592Srgrimes * must display the following acknowledgement: 181592Srgrimes * This product includes software developed by the University of 191592Srgrimes * California, Berkeley and its contributors. 201592Srgrimes * 4. Neither the name of the University nor the names of its contributors 211592Srgrimes * may be used to endorse or promote products derived from this software 221592Srgrimes * without specific prior written permission. 231592Srgrimes * 241592Srgrimes * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 251592Srgrimes * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 261592Srgrimes * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 271592Srgrimes * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 281592Srgrimes * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 291592Srgrimes * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 301592Srgrimes * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 311592Srgrimes * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 321592Srgrimes * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 331592Srgrimes * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 341592Srgrimes * SUCH DAMAGE. 3531329Scharnier */ 361592Srgrimes 3731329Scharnier#ifndef lint 3831329Scharnierstatic char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93"; 3950476Speter#endif /* not lint */ 401592Srgrimes 411592Srgrimes#include <sys/param.h> 421592Srgrimes#include <sys/stat.h> 431592Srgrimes#include <sys/mman.h> 4416433Sache 4516433Sache#include <limits.h> 4656668Sshin#include <errno.h> 471592Srgrimes#include <unistd.h> 481592Srgrimes#include <stdio.h> 4916433Sache#include <stdlib.h> 50107030Speter#include <string.h> 5116433Sache#include "extern.h" 521592Srgrimes 531592Srgrimesstatic void r_buf __P((FILE *)); 541592Srgrimesstatic void r_reg __P((FILE *, enum STYLE, long, struct stat *)); 551592Srgrimes 5689920Sume/* 571592Srgrimes * reverse -- display input in reverse order by line. 581592Srgrimes * 591592Srgrimes * There are six separate cases for this -- regular and non-regular 601592Srgrimes * files by bytes, lines or the whole file. 611592Srgrimes * 621592Srgrimes * BYTES display N bytes 631592Srgrimes * REG mmap the file and display the lines 641592Srgrimes * NOREG cyclically read characters into a wrap-around buffer 651592Srgrimes * 661592Srgrimes * LINES display N lines 6789920Sume * REG mmap the file and display the lines 6889920Sume * NOREG cyclically read lines into a wrap-around array of buffers 6989920Sume * 701592Srgrimes * FILE display the entire file 711592Srgrimes * REG mmap the file and display the lines 721592Srgrimes * NOREG cyclically read input into a linked list of buffers 7389920Sume */ 741592Srgrimesvoid 7589920Sumereverse(fp, style, off, sbp) 7689920Sume FILE *fp; 7789920Sume enum STYLE style; 7889920Sume long off; 7916433Sache struct stat *sbp; 801592Srgrimes{ 811592Srgrimes if (style != REVERSE && off == 0) 821592Srgrimes return; 831592Srgrimes 841592Srgrimes if (S_ISREG(sbp->st_mode)) 851592Srgrimes r_reg(fp, style, off, sbp); 86107030Speter else 87100612Syar switch(style) { 881592Srgrimes case FBYTES: 891592Srgrimes case RBYTES: 901592Srgrimes bytes(fp, off); 911592Srgrimes break; 92 case FLINES: 93 case RLINES: 94 lines(fp, off); 95 break; 96 case REVERSE: 97 r_buf(fp); 98 break; 99 } 100} 101 102/* 103 * r_reg -- display a regular file in reverse order by line. 104 */ 105static void 106r_reg(fp, style, off, sbp) 107 FILE *fp; 108 register enum STYLE style; 109 long off; 110 struct stat *sbp; 111{ 112 register off_t size; 113 register int llen; 114 register char *p; 115 char *start; 116 117 if (!(size = sbp->st_size)) 118 return; 119 120 if (size > SIZE_T_MAX) { 121 err(0, "%s: %s", fname, strerror(EFBIG)); 122 return; 123 } 124 125 if ((start = mmap(NULL, (size_t)size, 126 PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) { 127 err(0, "%s: %s", fname, strerror(EFBIG)); 128 return; 129 } 130 p = start + size - 1; 131 132 if (style == RBYTES && off < size) 133 size = off; 134 135 /* Last char is special, ignore whether newline or not. */ 136 for (llen = 1; --size; ++llen) 137 if (*--p == '\n') { 138 WR(p + 1, llen); 139 llen = 0; 140 if (style == RLINES && !--off) { 141 ++p; 142 break; 143 } 144 } 145 if (llen) 146 WR(p, llen); 147 if (munmap(start, (size_t)sbp->st_size)) 148 err(0, "%s: %s", fname, strerror(errno)); 149} 150 151typedef struct bf { 152 struct bf *next; 153 struct bf *prev; 154 int len; 155 char *l; 156} BF; 157 158/* 159 * r_buf -- display a non-regular file in reverse order by line. 160 * 161 * This is the function that saves the entire input, storing the data in a 162 * doubly linked list of buffers and then displays them in reverse order. 163 * It has the usual nastiness of trying to find the newlines, as there's no 164 * guarantee that a newline occurs anywhere in the file, let alone in any 165 * particular buffer. If we run out of memory, input is discarded (and the 166 * user warned). 167 */ 168static void 169r_buf(fp) 170 FILE *fp; 171{ 172 register BF *mark, *tl, *tr; 173 register int ch, len, llen; 174 register char *p; 175 off_t enomem; 176 177#define BSZ (128 * 1024) 178 for (mark = NULL, enomem = 0;;) { 179 /* 180 * Allocate a new block and link it into place in a doubly 181 * linked list. If out of memory, toss the LRU block and 182 * keep going. 183 */ 184 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 185 (tl->l = malloc(BSZ)) == NULL) { 186 if (!mark) 187 err(1, "%s", strerror(errno)); 188 tl = enomem ? tl->next : mark; 189 enomem += tl->len; 190 } else if (mark) { 191 tl->next = mark; 192 tl->prev = mark->prev; 193 mark->prev->next = tl; 194 mark->prev = tl; 195 } else 196 mark->next = mark->prev = (mark = tl); 197 198 /* Fill the block with input data. */ 199 for (p = tl->l, len = 0; 200 len < BSZ && (ch = getc(fp)) != EOF; ++len) 201 *p++ = ch; 202 203 /* 204 * If no input data for this block and we tossed some data, 205 * recover it. 206 */ 207 if (!len) { 208 if (enomem) 209 enomem -= tl->len; 210 tl = tl->prev; 211 break; 212 } 213 214 tl->len = len; 215 if (ch == EOF) 216 break; 217 } 218 219 if (enomem) { 220 (void)fprintf(stderr, 221 "tail: warning: %ld bytes discarded\n", enomem); 222 rval = 1; 223 } 224 225 /* 226 * Step through the blocks in the reverse order read. The last char 227 * is special, ignore whether newline or not. 228 */ 229 for (mark = tl;;) { 230 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 231 --p, ++llen) 232 if (*p == '\n') { 233 if (llen) { 234 WR(p + 1, llen); 235 llen = 0; 236 } 237 if (tl == mark) 238 continue; 239 for (tr = tl->next; tr->len; tr = tr->next) { 240 WR(tr->l, tr->len); 241 tr->len = 0; 242 if (tr == mark) 243 break; 244 } 245 } 246 tl->len = llen; 247 if ((tl = tl->prev) == mark) 248 break; 249 } 250 tl = tl->next; 251 if (tl->len) { 252 WR(tl->l, tl->len); 253 tl->len = 0; 254 } 255 while ((tl = tl->next)->len) { 256 WR(tl->l, tl->len); 257 tl->len = 0; 258 } 259} 260