Annotation of src/usr.bin/tail/reverse.c, Revision 1.19
1.19 ! deraadt 1: /* $OpenBSD: reverse.c,v 1.18 2007/09/29 12:31:28 otto Exp $ */
1.1 deraadt 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.
1.13 millert 19: * 3. Neither the name of the University nor the names of its contributors
1.1 deraadt 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:
1.3 millert 38: #include <err.h>
1.1 deraadt 39: #include <stdio.h>
40: #include <stdlib.h>
1.3 millert 41: #include <unistd.h>
42:
1.1 deraadt 43: #include "extern.h"
44:
1.12 millert 45: static void r_buf(FILE *);
1.15 otto 46: static int r_reg(FILE *, enum STYLE, off_t, struct stat *);
1.1 deraadt 47:
1.14 henning 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:
1.1 deraadt 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
1.14 henning 67: * REG reverse scan and display the lines
1.1 deraadt 68: * NOREG cyclically read characters into a wrap-around buffer
69: *
70: * LINES display N lines
1.14 henning 71: * REG reverse scan and display the lines
1.1 deraadt 72: * NOREG cyclically read lines into a wrap-around array of buffers
73: *
74: * FILE display the entire file
1.14 henning 75: * REG reverse scan and display the lines
1.1 deraadt 76: * NOREG cyclically read input into a linked list of buffers
77: */
78: void
1.17 kjell 79: reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
1.1 deraadt 80: {
81: if (style != REVERSE && off == 0)
82: return;
83:
1.4 millert 84: if (!S_ISREG(sbp->st_mode) || r_reg(fp, style, off, sbp) != 0)
1.1 deraadt 85: switch(style) {
86: case FBYTES:
87: case RBYTES:
1.7 ericj 88: (void)bytes(fp, off);
1.1 deraadt 89: break;
90: case FLINES:
91: case RLINES:
1.7 ericj 92: (void)lines(fp, off);
1.1 deraadt 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: */
1.4 millert 103: static int
1.15 otto 104: r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
1.1 deraadt 105: {
1.14 henning 106: off_t start, pos, end;
107: int ch;
1.1 deraadt 108:
1.14 henning 109: end = sbp->st_size;
110: if (end == 0)
1.4 millert 111: return (0);
1.1 deraadt 112:
1.14 henning 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)
1.1 deraadt 132: break;
133: }
1.14 henning 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: }
1.4 millert 147: return (0);
1.1 deraadt 148: }
149:
150: typedef struct bf {
151: struct bf *next;
152: struct bf *prev;
1.16 kjell 153: size_t len;
1.1 deraadt 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
1.17 kjell 168: r_buf(FILE *fp)
1.1 deraadt 169: {
1.11 mpech 170: BF *mark, *tr, *tl = NULL;
1.16 kjell 171: int ch;
172: size_t len, llen;
1.11 mpech 173: char *p;
1.1 deraadt 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)
1.3 millert 186: err(1, NULL);
1.1 deraadt 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;
1.9 pjanzen 194: } else {
195: mark = tl;
196: mark->next = mark->prev = mark;
197: }
1.5 mickey 198:
199: if (!enomem)
200: tl->len = 0;
1.1 deraadt 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,
1.10 pvalchev 225: "tail: warning: %lld bytes discarded\n", (long long)enomem);
1.1 deraadt 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: }
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