text_cmds/tail/reverse.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Edward Sze-Tyan Wang.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if 0
  38 #ifndef lint
  39 static char sccsid[] = "@(#)reverse.c   8.1 (Berkeley) 6/6/93";
  40 #endif /* not lint */
  41 #endif
  42
  43 #include <sys/cdefs.h>
  44 __FBSDID("$FreeBSD$");
  45
  46 #include <sys/param.h>
  47 #include <sys/stat.h>
  48 #include <sys/mman.h>
  49
  50 #include <err.h>
  51 #include <errno.h>
  52 #include <limits.h>
  53 #include <stdint.h>
  54 #include <stdio.h>
  55 #include <stdlib.h>
  56 #include <string.h>
  57 #include <unistd.h>
  58
  59 #include "extern.h"
  60
  61 static void r_buf(FILE *);
  62 static void r_reg(FILE *, enum STYLE, off_t, struct stat *);
  63
  64 /*
  65  * reverse -- display input in reverse order by line.
  66  *
  67  * There are six separate cases for this -- regular and non-regular
  68  * files by bytes, lines or the whole file.
  69  *
  70  * BYTES        display N bytes
  71  *      REG     mmap the file and display the lines
  72  *      NOREG   cyclically read characters into a wrap-around buffer
  73  *
  74  * LINES        display N lines
  75  *      REG     mmap the file and display the lines
  76  *      NOREG   cyclically read lines into a wrap-around array of buffers
  77  *
  78  * FILE         display the entire file
  79  *      REG     mmap the file and display the lines
  80  *      NOREG   cyclically read input into a linked list of buffers
  81  */
  82 void
  83 reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
  84 {
  85         if (style != REVERSE && off == 0)
  86                 return;
  87
  88         if (S_ISREG(sbp->st_mode))
  89                 r_reg(fp, style, off, sbp);
  90         else
  91                 switch(style) {
  92                 case FBYTES:
  93                 case RBYTES:
  94                         bytes(fp, off);
  95                         break;
  96                 case FLINES:
  97                 case RLINES:
  98                         lines(fp, off);
  99                         break;
 100                 case REVERSE:
 101                         r_buf(fp);
 102                         break;
 103                 default:
 104                         break;
 105                 }
 106 }
 107
 108 /*
 109  * r_reg -- display a regular file in reverse order by line.
 110  */
 111 static void
 112 r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 113 {
 114         struct mapinfo map;
 115         off_t curoff, size, lineend;
 116         int i;
 117
 118         if (!(size = sbp->st_size))
 119                 return;
 120
 121         map.start = NULL;
 122         map.mapoff = map.maxoff = size;
 123         map.fd = fileno(fp);
 124
 125         /*
 126          * Last char is special, ignore whether newline or not. Note that
 127          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 128          */
 129         curoff = size - 2;
 130         lineend = size;
 131         while (curoff >= 0) {
 132                 if (curoff < map.mapoff ||
 133                     curoff >= map.mapoff + (off_t)map.maplen) {
 134                         if (maparound(&map, curoff) != 0) {
 135                                 ierr();
 136                                 return;
 137                         }
 138                 }
 139                 for (i = curoff - map.mapoff; i >= 0; i--) {
 140                         if (style == RBYTES && --off == 0)
 141                                 break;
 142                         if (map.start[i] == '\n')
 143                                 break;
 144                 }
 145                 /* `i' is either the map offset of a '\n', or -1. */
 146                 curoff = map.mapoff + i;
 147                 if (i < 0)
 148                         continue;
 149
 150                 /* Print the line and update offsets. */
 151                 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
 152                         ierr();
 153                         return;
 154                 }
 155                 lineend = curoff + 1;
 156                 curoff--;
 157
 158                 if (style == RLINES)
 159                         off--;
 160
 161                 if (off == 0 && style != REVERSE) {
 162                         /* Avoid printing anything below. */
 163                         curoff = 0;
 164                         break;
 165                 }
 166         }
 167         if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
 168                 ierr();
 169                 return;
 170         }
 171         if (map.start != NULL && munmap(map.start, map.maplen))
 172                 ierr();
 173 }
 174
 175 typedef struct bf {
 176         struct bf *next;
 177         struct bf *prev;
 178         int len;
 179         char *l;
 180 } BF;
 181
 182 /*
 183  * r_buf -- display a non-regular file in reverse order by line.
 184  *
 185  * This is the function that saves the entire input, storing the data in a
 186  * doubly linked list of buffers and then displays them in reverse order.
 187  * It has the usual nastiness of trying to find the newlines, as there's no
 188  * guarantee that a newline occurs anywhere in the file, let alone in any
 189  * particular buffer.  If we run out of memory, input is discarded (and the
 190  * user warned).
 191  */
 192 static void
 193 r_buf(FILE *fp)
 194 {
 195         BF *mark, *tl, *tr;
 196         int ch, len, llen;
 197         char *p;
 198         off_t enomem;
 199
 200 #define BSZ     (128 * 1024)
 201         for (mark = NULL, enomem = 0;;) {
 202                 /*
 203                  * Allocate a new block and link it into place in a doubly
 204                  * linked list.  If out of memory, toss the LRU block and
 205                  * keep going.
 206                  */
 207                 if (enomem || (tl = malloc(sizeof(BF))) == NULL ||
 208                     (tl->l = malloc(BSZ)) == NULL) {
 209                         if (!mark)
 210                                 err(1, "malloc");
 211                         tl = enomem ? tl->next : mark;
 212                         enomem += tl->len;
 213                 } else if (mark) {
 214                         tl->next = mark;
 215                         tl->prev = mark->prev;
 216                         mark->prev->next = tl;
 217                         mark->prev = tl;
 218                 } else {
 219                         mark = tl;
 220                         mark->next = mark->prev = mark;
 221                 }
 222
 223                 /* Fill the block with input data. */
 224                 for (p = tl->l, len = 0;
 225                     len < BSZ && (ch = getc(fp)) != EOF; ++len)
 226                         *p++ = ch;
 227
 228                 if (ferror(fp)) {
 229                         ierr();
 230                         return;
 231                 }
 232
 233                 /*
 234                  * If no input data for this block and we tossed some data,
 235                  * recover it.
 236                  */
 237                 if (!len && enomem) {
 238                         enomem -= tl->len;
 239                         tl = tl->prev;
 240                         break;
 241                 }
 242
 243                 tl->len = len;
 244                 if (ch == EOF)
 245                         break;
 246         }
 247
 248         if (enomem) {
 249                 warnx("warning: %jd bytes discarded", (intmax_t)enomem);
 250                 rval = 1;
 251         }
 252
 253         /*
 254          * Step through the blocks in the reverse order read.  The last char
 255          * is special, ignore whether newline or not.
 256          */
 257         for (mark = tl;;) {
 258                 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
 259                     --p, ++llen)
 260                         if (*p == '\n') {
 261                                 if (llen) {
 262                                         WR(p + 1, llen);
 263                                         llen = 0;
 264                                 }
 265                                 if (tl == mark)
 266                                         continue;
 267                                 for (tr = tl->next; tr->len; tr = tr->next) {
 268                                         WR(tr->l, tr->len);
 269                                         tr->len = 0;
 270                                         if (tr == mark)
 271                                                 break;
 272                                 }
 273                         }
 274                 tl->len = llen;
 275                 if ((tl = tl->prev) == mark)
 276                         break;
 277         }
 278         tl = tl->next;
 279         if (tl->len) {
 280                 WR(tl->l, tl->len);
 281                 tl->len = 0;
 282         }
 283         while ((tl = tl->next)->len) {
 284                 WR(tl->l, tl->len);
 285                 tl->len = 0;
 286         }
 287 }