1 /* $OpenBSD: reverse.c,v 1.19 2009/10/27 23:59:44 deraadt Exp $ */ 2 /* $NetBSD: reverse.c,v 1.6 1994/11/23 07:42:10 jtc Exp $ */ 3 4 /*- 5 * Copyright (c) 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * Edward Sze-Tyan Wang. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #include <sys/stat.h> 37 38 #include <err.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <unistd.h> 42 43 #include "extern.h" 44 45 static void r_buf(FILE *); 46 static int r_reg(FILE *, enum STYLE, off_t, struct stat *); 47 48 #define COPYCHAR(fp, ch) \ 49 do { \ 50 if ((ch = getc(fp)) == EOF) { \ 51 ierr(); \ 52 return (0); \ 53 } \ 54 if (putchar(ch) == EOF) { \ 55 oerr(); \ 56 return (0); \ 57 } \ 58 } while (0) 59 60 /* 61 * reverse -- display input in reverse order by line. 62 * 63 * There are six separate cases for this -- regular and non-regular 64 * files by bytes, lines or the whole file. 65 * 66 * BYTES display N bytes 67 * REG reverse scan and display the lines 68 * NOREG cyclically read characters into a wrap-around buffer 69 * 70 * LINES display N lines 71 * REG reverse scan and display the lines 72 * NOREG cyclically read lines into a wrap-around array of buffers 73 * 74 * FILE display the entire file 75 * REG reverse scan and display the lines 76 * NOREG cyclically read input into a linked list of buffers 77 */ 78 void 79 reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 80 { 81 if (style != REVERSE && off == 0) 82 return; 83 84 if (!S_ISREG(sbp->st_mode) || r_reg(fp, style, off, sbp) != 0) 85 switch(style) { 86 case FBYTES: 87 case RBYTES: 88 (void)bytes(fp, off); 89 break; 90 case FLINES: 91 case RLINES: 92 (void)lines(fp, off); 93 break; 94 case REVERSE: 95 r_buf(fp); 96 break; 97 } 98 } 99 100 /* 101 * r_reg -- display a regular file in reverse order by line. 102 */ 103 static int 104 r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 105 { 106 off_t start, pos, end; 107 int ch; 108 109 end = sbp->st_size; 110 if (end == 0) 111 return (0); 112 113 /* Position before char, ignore last char whether newline or not */ 114 pos = end-2; 115 ch = EOF; 116 start = 0; 117 118 if (style == RBYTES && off < end) 119 start = end - off; 120 121 for (; pos >= start; pos--) { 122 /* A seek per char isn't a problem with a smart stdio */ 123 if (fseeko(fp, pos, SEEK_SET) != 0) { 124 ierr(); 125 return (0); 126 } 127 if ((ch = getc(fp)) == '\n') { 128 while (--end > pos) 129 COPYCHAR(fp, ch); 130 end++; 131 if (style == RLINES && --off == 0) 132 break; 133 } 134 else if (ch == EOF) { 135 ierr(); 136 return (0); 137 } 138 } 139 if (pos < start) { 140 if (ch != EOF && ungetc(ch, fp) == EOF) { 141 ierr(); 142 return (0); 143 } 144 while (--end >= start) 145 COPYCHAR(fp, ch); 146 } 147 return (0); 148 } 149 150 typedef struct bf { 151 struct bf *next; 152 struct bf *prev; 153 size_t len; 154 char *l; 155 } BF; 156 157 /* 158 * r_buf -- display a non-regular file in reverse order by line. 159 * 160 * This is the function that saves the entire input, storing the data in a 161 * doubly linked list of buffers and then displays them in reverse order. 162 * It has the usual nastiness of trying to find the newlines, as there's no 163 * guarantee that a newline occurs anywhere in the file, let alone in any 164 * particular buffer. If we run out of memory, input is discarded (and the 165 * user warned). 166 */ 167 static void 168 r_buf(FILE *fp) 169 { 170 BF *mark, *tr, *tl = NULL; 171 int ch; 172 size_t len, llen; 173 char *p; 174 off_t enomem; 175 176 #define BSZ (128 * 1024) 177 for (mark = NULL, enomem = 0;;) { 178 /* 179 * Allocate a new block and link it into place in a doubly 180 * linked list. If out of memory, toss the LRU block and 181 * keep going. 182 */ 183 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 184 (tl->l = malloc(BSZ)) == NULL) { 185 if (!mark) 186 err(1, NULL); 187 tl = enomem ? tl->next : mark; 188 enomem += tl->len; 189 } else if (mark) { 190 tl->next = mark; 191 tl->prev = mark->prev; 192 mark->prev->next = tl; 193 mark->prev = tl; 194 } else { 195 mark = tl; 196 mark->next = mark->prev = mark; 197 } 198 199 if (!enomem) 200 tl->len = 0; 201 202 /* Fill the block with input data. */ 203 for (p = tl->l, len = 0; 204 len < BSZ && (ch = getc(fp)) != EOF; ++len) 205 *p++ = ch; 206 207 /* 208 * If no input data for this block and we tossed some data, 209 * recover it. 210 */ 211 if (!len) { 212 if (enomem) 213 enomem -= tl->len; 214 tl = tl->prev; 215 break; 216 } 217 218 tl->len = len; 219 if (ch == EOF) 220 break; 221 } 222 223 if (enomem) { 224 (void)fprintf(stderr, 225 "tail: warning: %lld bytes discarded\n", (long long)enomem); 226 rval = 1; 227 } 228 229 /* 230 * Step through the blocks in the reverse order read. The last char 231 * is special, ignore whether newline or not. 232 */ 233 for (mark = tl;;) { 234 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 235 --p, ++llen) 236 if (*p == '\n') { 237 if (llen) { 238 WR(p + 1, llen); 239 llen = 0; 240 } 241 if (tl == mark) 242 continue; 243 for (tr = tl->next; tr->len; tr = tr->next) { 244 WR(tr->l, tr->len); 245 tr->len = 0; 246 if (tr == mark) 247 break; 248 } 249 } 250 tl->len = llen; 251 if ((tl = tl->prev) == mark) 252 break; 253 } 254 tl = tl->next; 255 if (tl->len) { 256 WR(tl->l, tl->len); 257 tl->len = 0; 258 } 259 while ((tl = tl->next)->len) { 260 WR(tl->l, tl->len); 261 tl->len = 0; 262 } 263 } 264