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1.1 deraadt 1: /*
2: * Copyright (c) 1988 Mark Nudleman
3: * Copyright (c) 1988 Regents of the University of California.
4: * All rights reserved.
5: *
6: * Redistribution and use in source and binary forms, with or without
7: * modification, are permitted provided that the following conditions
8: * are met:
9: * 1. Redistributions of source code must retain the above copyright
10: * notice, this list of conditions and the following disclaimer.
11: * 2. Redistributions in binary form must reproduce the above copyright
12: * notice, this list of conditions and the following disclaimer in the
13: * documentation and/or other materials provided with the distribution.
14: * 3. All advertising materials mentioning features or use of this software
15: * must display the following acknowledgement:
16: * This product includes software developed by the University of
17: * California, Berkeley and its contributors.
18: * 4. Neither the name of the University nor the names of its contributors
19: * may be used to endorse or promote products derived from this software
20: * without specific prior written permission.
21: *
22: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32: * SUCH DAMAGE.
33: */
34:
35: #ifndef lint
36: /* from: static char sccsid[] = "@(#)ch.c 5.11 (Berkeley) 6/21/92"; */
37: static char *rcsid = "$Id: ch.c,v 1.3 1994/04/06 17:50:39 cgd Exp $";
38: #endif /* not lint */
39:
40: /*
41: * Low level character input from the input file.
42: * We use these special purpose routines which optimize moving
43: * both forward and backward from the current read pointer.
44: */
45:
46: #include <sys/types.h>
47: #include <sys/file.h>
48: #include <unistd.h>
49: #include <stdio.h>
50: #include <less.h>
51:
52: int file = -1; /* File descriptor of the input file */
53:
54: /*
55: * Pool of buffers holding the most recently used blocks of the input file.
56: */
57: struct buf {
58: struct buf *next, *prev;
59: long block;
60: int datasize;
61: char data[BUFSIZ];
62: };
63: int nbufs;
64:
65: /*
66: * The buffer pool is kept as a doubly-linked circular list, in order from
67: * most- to least-recently used. The circular list is anchored by buf_anchor.
68: */
69: #define END_OF_CHAIN ((struct buf *)&buf_anchor)
70: #define buf_head buf_anchor.next
71: #define buf_tail buf_anchor.prev
72:
73: static struct {
74: struct buf *next, *prev;
75: } buf_anchor = { END_OF_CHAIN, END_OF_CHAIN };
76:
77: extern int ispipe, cbufs, sigs;
78:
79: /*
80: * Current position in file.
81: * Stored as a block number and an offset into the block.
82: */
83: static long ch_block;
84: static int ch_offset;
85:
86: /* Length of file, needed if input is a pipe. */
87: static off_t ch_fsize;
88:
89: /* Number of bytes read, if input is standard input (a pipe). */
90: static off_t last_piped_pos;
91:
92: /*
93: * Get the character pointed to by the read pointer. ch_get() is a macro
94: * which is more efficient to call than fch_get (the function), in the usual
95: * case that the block desired is at the head of the chain.
96: */
97: #define ch_get() \
98: ((buf_head->block == ch_block && \
99: ch_offset < buf_head->datasize) ? \
100: buf_head->data[ch_offset] : fch_get())
101:
102: static
103: fch_get()
104: {
105: extern int bs_mode;
106: register struct buf *bp;
107: register int n, ch;
108: register char *p, *t;
109: off_t pos;
110:
111: /* look for a buffer holding the desired block. */
112: for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
113: if (bp->block == ch_block) {
114: if (ch_offset >= bp->datasize)
115: /*
116: * Need more data in this buffer.
117: */
118: goto read_more;
119: /*
120: * On a pipe, we don't sort the buffers LRU
121: * because this can cause gaps in the buffers.
122: * For example, suppose we've got 12 1K buffers,
123: * and a 15K input stream. If we read the first 12K
124: * sequentially, then jump to line 1, then jump to
125: * the end, the buffers have blocks 0,4,5,6,..,14.
126: * If we then jump to line 1 again and try to
127: * read sequentially, we're out of luck when we
128: * get to block 1 (we'd get the "pipe error" below).
129: * To avoid this, we only sort buffers on a pipe
130: * when we actually READ the data, not when we
131: * find it already buffered.
132: */
133: if (ispipe)
134: return(bp->data[ch_offset]);
135: goto found;
136: }
137: /*
138: * Block is not in a buffer. Take the least recently used buffer
139: * and read the desired block into it. If the LRU buffer has data
140: * in it, and input is a pipe, then try to allocate a new buffer first.
141: */
142: if (ispipe && buf_tail->block != (long)(-1))
143: (void)ch_addbuf(1);
144: bp = buf_tail;
145: bp->block = ch_block;
146: bp->datasize = 0;
147:
148: read_more:
149: pos = (ch_block * BUFSIZ) + bp->datasize;
150: if (ispipe) {
151: /*
152: * The data requested should be immediately after
153: * the last data read from the pipe.
154: */
155: if (pos != last_piped_pos) {
156: error("pipe error");
157: quit();
158: }
159: } else
160: (void)lseek(file, pos, L_SET);
161:
162: /*
163: * Read the block.
164: * If we read less than a full block, we just return the
165: * partial block and pick up the rest next time.
166: */
167: n = iread(file, &bp->data[bp->datasize], BUFSIZ - bp->datasize);
168: if (n == READ_INTR)
169: return (EOI);
170: if (n < 0) {
171: error("read error");
172: quit();
173: }
174: if (ispipe)
175: last_piped_pos += n;
176:
177: p = &bp->data[bp->datasize];
178: bp->datasize += n;
179:
180: /*
181: * Set an EOI marker in the buffered data itself. Then ensure the
182: * data is "clean": there are no extra EOI chars in the data and
183: * that the "meta" bit (the 0200 bit) is reset in each char;
184: * also translate \r\n sequences to \n if -u flag not set.
185: */
186: if (n == 0) {
187: ch_fsize = pos;
188: bp->data[bp->datasize++] = EOI;
189: }
190:
191: if (bs_mode) {
192: for (p = &bp->data[bp->datasize]; --n >= 0;) {
193: *--p &= 0177;
194: if (*p == EOI)
195: *p = 0200;
196: }
197: }
198: else {
199: for (t = p; --n >= 0; ++p) {
200: ch = *p & 0177;
201: if (ch == '\r' && n && (p[1] & 0177) == '\n') {
202: ++p;
203: *t++ = '\n';
204: }
205: else
206: *t++ = (ch == EOI) ? 0200 : ch;
207: }
208: if (p != t) {
209: bp->datasize -= p - t;
210: if (ispipe)
211: last_piped_pos -= p - t;
212: }
213: }
214:
215: found:
216: if (buf_head != bp) {
217: /*
218: * Move the buffer to the head of the buffer chain.
219: * This orders the buffer chain, most- to least-recently used.
220: */
221: bp->next->prev = bp->prev;
222: bp->prev->next = bp->next;
223:
224: bp->next = buf_head;
225: bp->prev = END_OF_CHAIN;
226: buf_head->prev = bp;
227: buf_head = bp;
228: }
229:
230: if (ch_offset >= bp->datasize)
231: /*
232: * After all that, we still don't have enough data.
233: * Go back and try again.
234: */
235: goto read_more;
236:
237: return(bp->data[ch_offset]);
238: }
239:
240: /*
241: * Determine if a specific block is currently in one of the buffers.
242: */
243: static
244: buffered(block)
245: long block;
246: {
247: register struct buf *bp;
248:
249: for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
250: if (bp->block == block)
251: return(1);
252: return(0);
253: }
254:
255: /*
256: * Seek to a specified position in the file.
257: * Return 0 if successful, non-zero if can't seek there.
258: */
259: ch_seek(pos)
260: register off_t pos;
261: {
262: long new_block;
263:
264: new_block = pos / BUFSIZ;
265: if (!ispipe || pos == last_piped_pos || buffered(new_block)) {
266: /*
267: * Set read pointer.
268: */
269: ch_block = new_block;
270: ch_offset = pos % BUFSIZ;
271: return(0);
272: }
273: return(1);
274: }
275:
276: /*
277: * Seek to the end of the file.
278: */
279: ch_end_seek()
280: {
281: off_t ch_length();
282:
283: if (!ispipe)
284: return(ch_seek(ch_length()));
285:
286: /*
287: * Do it the slow way: read till end of data.
288: */
289: while (ch_forw_get() != EOI)
290: if (sigs)
291: return(1);
292: return(0);
293: }
294:
295: /*
296: * Seek to the beginning of the file, or as close to it as we can get.
297: * We may not be able to seek there if input is a pipe and the
298: * beginning of the pipe is no longer buffered.
299: */
300: ch_beg_seek()
301: {
302: register struct buf *bp, *firstbp;
303:
304: /*
305: * Try a plain ch_seek first.
306: */
307: if (ch_seek((off_t)0) == 0)
308: return(0);
309:
310: /*
311: * Can't get to position 0.
312: * Look thru the buffers for the one closest to position 0.
313: */
314: firstbp = bp = buf_head;
315: if (bp == END_OF_CHAIN)
316: return(1);
317: while ((bp = bp->next) != END_OF_CHAIN)
318: if (bp->block < firstbp->block)
319: firstbp = bp;
320: ch_block = firstbp->block;
321: ch_offset = 0;
322: return(0);
323: }
324:
325: /*
326: * Return the length of the file, if known.
327: */
328: off_t
329: ch_length()
330: {
331: if (ispipe)
332: return(ch_fsize);
333: return((off_t)(lseek(file, (off_t)0, L_XTND)));
334: }
335:
336: /*
337: * Return the current position in the file.
338: */
339: off_t
340: ch_tell()
341: {
342: return(ch_block * BUFSIZ + ch_offset);
343: }
344:
345: /*
346: * Get the current char and post-increment the read pointer.
347: */
348: ch_forw_get()
349: {
350: register int c;
351:
352: c = ch_get();
353: if (c != EOI && ++ch_offset >= BUFSIZ) {
354: ch_offset = 0;
355: ++ch_block;
356: }
357: return(c);
358: }
359:
360: /*
361: * Pre-decrement the read pointer and get the new current char.
362: */
363: ch_back_get()
364: {
365: if (--ch_offset < 0) {
366: if (ch_block <= 0 || (ispipe && !buffered(ch_block-1))) {
367: ch_offset = 0;
368: return(EOI);
369: }
370: ch_offset = BUFSIZ - 1;
371: ch_block--;
372: }
373: return(ch_get());
374: }
375:
376: /*
377: * Allocate buffers.
378: * Caller wants us to have a total of at least want_nbufs buffers.
379: * keep==1 means keep the data in the current buffers;
380: * otherwise discard the old data.
381: */
382: ch_init(want_nbufs, keep)
383: int want_nbufs;
384: int keep;
385: {
386: register struct buf *bp;
387: char message[80];
388:
389: cbufs = nbufs;
390: if (nbufs < want_nbufs && ch_addbuf(want_nbufs - nbufs)) {
391: /*
392: * Cannot allocate enough buffers.
393: * If we don't have ANY, then quit.
394: * Otherwise, just report the error and return.
395: */
396: (void)sprintf(message, "cannot allocate %d buffers",
397: want_nbufs - nbufs);
398: error(message);
399: if (nbufs == 0)
400: quit();
401: return;
402: }
403:
404: if (keep)
405: return;
406:
407: /*
408: * We don't want to keep the old data,
409: * so initialize all the buffers now.
410: */
411: for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
412: bp->block = (long)(-1);
413: last_piped_pos = (off_t)0;
414: ch_fsize = NULL_POSITION;
415: (void)ch_seek((off_t)0);
416: }
417:
418: /*
419: * Allocate some new buffers.
420: * The buffers are added to the tail of the buffer chain.
421: */
422: ch_addbuf(nnew)
423: int nnew;
424: {
425: register struct buf *bp;
426: register struct buf *newbufs;
427: char *calloc();
428:
429: /*
430: * We don't have enough buffers.
431: * Allocate some new ones.
432: */
433: newbufs = (struct buf *)calloc((u_int)nnew, sizeof(struct buf));
434: if (newbufs == NULL)
435: return(1);
436:
437: /*
438: * Initialize the new buffers and link them together.
439: * Link them all onto the tail of the buffer list.
440: */
441: nbufs += nnew;
442: cbufs = nbufs;
443: for (bp = &newbufs[0]; bp < &newbufs[nnew]; bp++) {
444: bp->next = bp + 1;
445: bp->prev = bp - 1;
446: bp->block = (long)(-1);
447: }
448: newbufs[nnew-1].next = END_OF_CHAIN;
449: newbufs[0].prev = buf_tail;
450: buf_tail->next = &newbufs[0];
451: buf_tail = &newbufs[nnew-1];
452: return(0);
453: }