1 /*- 2 * Copyright (c) 1991 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Edward Sze-Tyan Wang. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11 #ifndef lint 12 static char sccsid[] = "@(#)reverse.c 5.5 (Berkeley) 03/04/92"; 13 #endif /* not lint */ 14 15 #include <sys/param.h> 16 #include <sys/stat.h> 17 #include <sys/mman.h> 18 #include <errno.h> 19 #include <unistd.h> 20 #include <stdio.h> 21 #include <stdlib.h> 22 #include <string.h> 23 #include "extern.h" 24 25 static void r_buf __P((FILE *)); 26 static void r_reg __P((FILE *, enum STYLE, long, struct stat *)); 27 28 /* 29 * reverse -- display input in reverse order by line. 30 * 31 * There are six separate cases for this -- regular and non-regular 32 * files by bytes, lines or the whole file. 33 * 34 * BYTES display N bytes 35 * REG mmap the file and display the lines 36 * NOREG cyclically read characters into a wrap-around buffer 37 * 38 * LINES display N lines 39 * REG mmap the file and display the lines 40 * NOREG cyclically read lines into a wrap-around array of buffers 41 * 42 * FILE display the entire file 43 * REG mmap the file and display the lines 44 * NOREG cyclically read input into a linked list of buffers 45 */ 46 void 47 reverse(fp, style, off, sbp) 48 FILE *fp; 49 enum STYLE style; 50 long off; 51 struct stat *sbp; 52 { 53 if (style != REVERSE && off == 0) 54 return; 55 56 if (S_ISREG(sbp->st_mode)) 57 r_reg(fp, style, off, sbp); 58 else 59 switch(style) { 60 case FBYTES: 61 case RBYTES: 62 bytes(fp, off); 63 break; 64 case FLINES: 65 case RLINES: 66 lines(fp, off); 67 break; 68 case REVERSE: 69 r_buf(fp); 70 break; 71 } 72 } 73 74 /* 75 * r_reg -- display a regular file in reverse order by line. 76 */ 77 static void 78 r_reg(fp, style, off, sbp) 79 FILE *fp; 80 register enum STYLE style; 81 long off; 82 struct stat *sbp; 83 { 84 register off_t size; 85 register int llen; 86 register char *p; 87 88 if (!(size = sbp->st_size)) 89 return; 90 91 if ((p = mmap(NULL, 92 size, PROT_READ, MAP_FILE, fileno(fp), (off_t)0)) == (caddr_t)-1) { 93 err(0, "%s", strerror(errno)); 94 return; 95 } 96 p += size - 1; 97 98 if (style == RBYTES && off < size) 99 size = off; 100 101 /* Last char is special, ignore whether newline or not. */ 102 for (llen = 1; --size; ++llen) 103 if (*--p == '\n') { 104 WR(p + 1, llen); 105 llen = 0; 106 if (style == RLINES && !--off) { 107 ++p; 108 break; 109 } 110 } 111 if (llen) 112 WR(p, llen); 113 } 114 115 typedef struct bf { 116 struct bf *next; 117 struct bf *prev; 118 int len; 119 char *l; 120 } BF; 121 122 /* 123 * r_buf -- display a non-regular file in reverse order by line. 124 * 125 * This is the function that saves the entire input, storing the data in a 126 * doubly linked list of buffers and then displays them in reverse order. 127 * It has the usual nastiness of trying to find the newlines, as there's no 128 * guarantee that a newline occurs anywhere in the file, let alone in any 129 * particular buffer. If we run out of memory, input is discarded (and the 130 * user warned). 131 */ 132 static void 133 r_buf(fp) 134 FILE *fp; 135 { 136 register BF *mark, *tl, *tr; 137 register int ch, len, llen; 138 register char *p; 139 off_t enomem; 140 141 #define BSZ (128 * 1024) 142 for (mark = NULL, enomem = 0;;) { 143 /* 144 * Allocate a new block and link it into place in a doubly 145 * linked list. If out of memory, toss the LRU block and 146 * keep going. 147 */ 148 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 149 (tl->l = malloc(BSZ)) == NULL) { 150 if (!mark) 151 err(1, "%s", strerror(errno)); 152 tl = enomem ? tl->next : mark; 153 enomem += tl->len; 154 } else if (mark) { 155 tl->next = mark; 156 tl->prev = mark->prev; 157 mark->prev->next = tl; 158 mark->prev = tl; 159 } else 160 mark->next = mark->prev = (mark = tl); 161 162 /* Fill the block with input data. */ 163 for (p = tl->l, len = 0; 164 len < BSZ && (ch = getc(fp)) != EOF; ++len) 165 *p++ = ch; 166 167 /* 168 * If no input data for this block and we tossed some data, 169 * recover it. 170 */ 171 if (!len) { 172 if (enomem) 173 enomem -= tl->len; 174 tl = tl->prev; 175 break; 176 } 177 178 tl->len = len; 179 if (ch == EOF) 180 break; 181 } 182 183 if (enomem) { 184 (void)fprintf(stderr, 185 "tail: warning: %ld bytes discarded\n", enomem); 186 rval = 1; 187 } 188 189 /* 190 * Step through the blocks in the reverse order read. The last char 191 * is special, ignore whether newline or not. 192 */ 193 for (mark = tl;;) { 194 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 195 --p, ++llen) 196 if (*p == '\n') { 197 if (llen) { 198 WR(p + 1, llen); 199 llen = 0; 200 } 201 if (tl == mark) 202 continue; 203 for (tr = tl->next; tr->len; tr = tr->next) { 204 WR(tr->l, tr->len); 205 tr->len = 0; 206 if (tr == mark) 207 break; 208 } 209 } 210 tl->len = llen; 211 if ((tl = tl->prev) == mark) 212 break; 213 } 214 tl = tl->next; 215 if (tl->len) { 216 WR(tl->l, tl->len); 217 tl->len = 0; 218 } 219 while ((tl = tl->next)->len) { 220 WR(tl->l, tl->len); 221 tl->len = 0; 222 } 223 } 224