[unix-history] / usr / src / usr.bin / more / ch.c

/*
 * Copyright (c) 1988 Mark Nudleman
 * Copyright (c) 1988 Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Mark Nudleman.
 * 
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char sccsid[] = "@(#)ch.c	5.4 (Berkeley) %G%";
#endif /* not lint */

/*
 * Low level character input from the input file.
 * We use these special purpose routines which optimize moving
 * both forward and backward from the current read pointer.
 */

#include "less.h"

public int file = -1;		/* File descriptor of the input file */

/*
 * Pool of buffers holding the most recently used blocks of the input file.
 */
#define BUFSIZ	1024
struct buf {
	struct buf *next, *prev;
	long block;
	int datasize;
	char data[BUFSIZ];
};
public int nbufs;

/*
 * The buffer pool is kept as a doubly-linked circular list,
 * in order from most- to least-recently used.
 * The circular list is anchored by buf_anchor.
 */
#define	END_OF_CHAIN	((struct buf *)&buf_anchor)
#define	buf_head	buf_anchor.next
#define	buf_tail	buf_anchor.prev

static struct {
	struct buf *next, *prev;
} buf_anchor = { END_OF_CHAIN, END_OF_CHAIN };

extern int clean_data;
extern int ispipe;
extern int autobuf;
extern int cbufs;
extern int sigs;

/*
 * Current position in file.
 * Stored as a block number and an offset into the block.
 */
static long ch_block;
static int ch_offset;

/* 
 * Length of file, needed if input is a pipe.
 */
static POSITION ch_fsize;

/*
 * Number of bytes read, if input is standard input (a pipe).
 */
static POSITION last_piped_pos;

/*
 * Get the character pointed to by the read pointer.
 * ch_get() is a macro which is more efficient to call
 * than fch_get (the function), in the usual case 
 * that the block desired is at the head of the chain.
 */
#define	ch_get()   ((buf_head->block == ch_block && \
		     ch_offset < buf_head->datasize) ? \
			buf_head->data[ch_offset] : fch_get())
	static int
fch_get()
{
	register struct buf *bp;
	register int n;
	register char *p;
	POSITION pos;

	/*
	 * Look for a buffer holding the desired block.
	 */
	for (bp = buf_head;  bp != END_OF_CHAIN;  bp = bp->next)
		if (bp->block == ch_block)
		{
			if (ch_offset >= bp->datasize)
				/*
				 * Need more data in this buffer.
				 */
				goto read_more;
			/*
			 * On a pipe, we don't sort the buffers LRU
			 * because this can cause gaps in the buffers.
			 * For example, suppose we've got 12 1K buffers,
			 * and a 15K input stream.  If we read the first 12K
			 * sequentially, then jump to line 1, then jump to
			 * the end, the buffers have blocks 0,4,5,6,..,14.
			 * If we then jump to line 1 again and try to
			 * read sequentially, we're out of luck when we
			 * get to block 1 (we'd get the "pipe error" below).
			 * To avoid this, we only sort buffers on a pipe
			 * when we actually READ the data, not when we
			 * find it already buffered.
			 */
			if (ispipe)
				return (bp->data[ch_offset]);
			goto found;
		}
	/*
	 * Block is not in a buffer.  
	 * Take the least recently used buffer 
	 * and read the desired block into it.
	 * If the LRU buffer has data in it, 
	 * and autobuf is true, and input is a pipe, 
	 * then try to allocate a new buffer first.
	 */
	if (autobuf && ispipe && buf_tail->block != (long)(-1))
		(void) ch_addbuf(1);
	bp = buf_tail;
	bp->block = ch_block;
	bp->datasize = 0;

    read_more:
	pos = (ch_block * BUFSIZ) + bp->datasize;
	if (ispipe)
	{
		/*
		 * The data requested should be immediately after
		 * the last data read from the pipe.
		 */
		if (pos != last_piped_pos)
		{
			error("pipe error");
			quit();
		}
	} else
		(void)lseek(file, pos, L_SET);

	/*
	 * Read the block.
	 * If we read less than a full block, we just return the
	 * partial block and pick up the rest next time.
	 */
	n = iread(file, &bp->data[bp->datasize], BUFSIZ - bp->datasize);
	if (n == READ_INTR)
		return (EOI);
	if (n < 0)
	{
		error("read error");
		quit();
	}
	if (ispipe)
		last_piped_pos += n;

	bp->datasize += n;

	/*
	 * Set an EOI marker in the buffered data itself.
	 * Then ensure the data is "clean": there are no 
	 * extra EOI chars in the data and that the "meta"
	 * bit (the 0200 bit) is reset in each char.
	 */
	if (n == 0)
	{
		ch_fsize = pos;
		bp->data[bp->datasize++] = EOI;
	}

	if (!clean_data)
	{
		p = &bp->data[bp->datasize];
		while (--n >= 0)
		{
			*--p &= 0177;
			if (*p == EOI)
				*p = '@';
		}
	}

    found:
	if (buf_head != bp)
	{
		/*
		 * Move the buffer to the head of the buffer chain.
		 * This orders the buffer chain, most- to least-recently used.
		 */
		bp->next->prev = bp->prev;
		bp->prev->next = bp->next;

		bp->next = buf_head;
		bp->prev = END_OF_CHAIN;
		buf_head->prev = bp;
		buf_head = bp;
	}

	if (ch_offset >= bp->datasize)
		/*
		 * After all that, we still don't have enough data.
		 * Go back and try again.
		 */
		goto read_more;

	return (bp->data[ch_offset]);
}

/*
 * Determine if a specific block is currently in one of the buffers.
 */
	static int
buffered(block)
	long block;
{
	register struct buf *bp;

	for (bp = buf_head;  bp != END_OF_CHAIN;  bp = bp->next)
		if (bp->block == block)
			return (1);
	return (0);
}

/*
 * Seek to a specified position in the file.
 * Return 0 if successful, non-zero if can't seek there.
 */
	public int
ch_seek(pos)
	register POSITION pos;
{
	long new_block;

	new_block = pos / BUFSIZ;
	if (!ispipe || pos == last_piped_pos || buffered(new_block))
	{
		/*
		 * Set read pointer.
		 */
		ch_block = new_block;
		ch_offset = pos % BUFSIZ;
		return (0);
	}
	return (1);
}

/*
 * Seek to the end of the file.
 */
	public int
ch_end_seek()
{
	if (!ispipe)
		return (ch_seek(ch_length()));

	/*
	 * Do it the slow way: read till end of data.
	 */
	while (ch_forw_get() != EOI)
		if (sigs)
			return (1);
	return (0);
}

/*
 * Seek to the beginning of the file, or as close to it as we can get.
 * We may not be able to seek there if input is a pipe and the
 * beginning of the pipe is no longer buffered.
 */
	public int
ch_beg_seek()
{
	register struct buf *bp, *firstbp;

	/*
	 * Try a plain ch_seek first.
	 */
	if (ch_seek((POSITION)0) == 0)
		return (0);

	/*
	 * Can't get to position 0.
	 * Look thru the buffers for the one closest to position 0.
	 */
	firstbp = bp = buf_head;
	if (bp == END_OF_CHAIN)
		return (1);
	while ((bp = bp->next) != END_OF_CHAIN)
		if (bp->block < firstbp->block)
			firstbp = bp;
	ch_block = firstbp->block;
	ch_offset = 0;
	return (0);
}

/*
 * Return the length of the file, if known.
 */
	public POSITION
ch_length()
{
	if (ispipe)
		return (ch_fsize);
	return ((POSITION)(lseek(file, (off_t)0, L_XTND)));
}

/*
 * Return the current position in the file.
 */
	public POSITION
ch_tell()
{
	return (ch_block * BUFSIZ + ch_offset);
}

/*
 * Get the current char and post-increment the read pointer.
 */
	public int
ch_forw_get()
{
	register int c;

	c = ch_get();
	if (c != EOI && ++ch_offset >= BUFSIZ)
	{
		ch_offset = 0;
		ch_block ++;
	}
	return (c);
}

/*
 * Pre-decrement the read pointer and get the new current char.
 */
	public int
ch_back_get()
{
	if (--ch_offset < 0)
	{
		if (ch_block <= 0 || (ispipe && !buffered(ch_block-1)))
		{
			ch_offset = 0;
			return (EOI);
		}
		ch_offset = BUFSIZ - 1;
		ch_block--;
	}
	return (ch_get());
}

/*
 * Allocate buffers.
 * Caller wants us to have a total of at least want_nbufs buffers.
 * keep==1 means keep the data in the current buffers;
 * otherwise discard the old data.
 */
	public void
ch_init(want_nbufs, keep)
	int want_nbufs;
	int keep;
{
	register struct buf *bp;
	char message[80];

	cbufs = nbufs;
	if (nbufs < want_nbufs && ch_addbuf(want_nbufs - nbufs))
	{
		/*
		 * Cannot allocate enough buffers.
		 * If we don't have ANY, then quit.
		 * Otherwise, just report the error and return.
		 */
		(void)sprintf(message, "cannot allocate %d buffers",
			want_nbufs - nbufs);
		error(message);
		if (nbufs == 0)
			quit();
		return;
	}

	if (keep)
		return;

	/*
	 * We don't want to keep the old data,
	 * so initialize all the buffers now.
	 */
	for (bp = buf_head;  bp != END_OF_CHAIN;  bp = bp->next)
		bp->block = (long)(-1);
	last_piped_pos = (POSITION)0;
	ch_fsize = NULL_POSITION;
	(void) ch_seek((POSITION)0);
}

/*
 * Allocate some new buffers.
 * The buffers are added to the tail of the buffer chain.
 */
	static int
ch_addbuf(nnew)
	int nnew;
{
	register struct buf *bp;
	register struct buf *newbufs;

	/*
	 * We don't have enough buffers.  
	 * Allocate some new ones.
	 */
	newbufs = (struct buf *) calloc((u_int)nnew, sizeof(struct buf));
	if (newbufs == NULL)
		return (1);

	/*
	 * Initialize the new buffers and link them together.
	 * Link them all onto the tail of the buffer list.
	 */
	nbufs += nnew;
	cbufs = nbufs;
	for (bp = &newbufs[0];  bp < &newbufs[nnew];  bp++)
	{
		bp->next = bp + 1;
		bp->prev = bp - 1;
		bp->block = (long)(-1);
	}
	newbufs[nnew-1].next = END_OF_CHAIN;
	newbufs[0].prev = buf_tail;
	buf_tail->next = &newbufs[0];
	buf_tail = &newbufs[nnew-1];
	return (0);
}
Commit	Line	Data
bfe13c81 KB	1	/*
	2	* Copyright (c) 1988 Mark Nudleman
	3	* Copyright (c) 1988 Regents of the University of California.
	4	* All rights reserved.
	5	*
	6	* This code is derived from software contributed to Berkeley by
	7	* Mark Nudleman.
	8	*
	9	* Redistribution and use in source and binary forms are permitted
	10	* provided that the above copyright notice and this paragraph are
	11	* duplicated in all such forms and that any documentation,
	12	* advertising materials, and other materials related to such
	13	* distribution and use acknowledge that the software was developed
	14	* by the University of California, Berkeley. The name of the
	15	* University may not be used to endorse or promote products derived
	16	* from this software without specific prior written permission.
	17	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
	18	* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
	19	* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
	20	*/
	21
	22	#ifndef lint
083e784b	23	static char sccsid[] = "@(#)ch.c 5.4 (Berkeley) %G%";
bfe13c81 KB	24	#endif /* not lint */
	25
	26	/*
	27	* Low level character input from the input file.
	28	* We use these special purpose routines which optimize moving
	29	* both forward and backward from the current read pointer.
	30	*/
	31
	32	#include "less.h"
	33
	34	public int file = -1; /* File descriptor of the input file */
	35
	36	/*
	37	* Pool of buffers holding the most recently used blocks of the input file.
	38	*/
	39	#define BUFSIZ 1024
	40	struct buf {
	41	struct buf next, prev;
	42	long block;
	43	int datasize;
	44	char data[BUFSIZ];
	45	};
	46	public int nbufs;
	47
	48	/*
	49	* The buffer pool is kept as a doubly-linked circular list,
	50	* in order from most- to least-recently used.
	51	* The circular list is anchored by buf_anchor.
	52	*/
	53	#define END_OF_CHAIN ((struct buf *)&buf_anchor)
	54	#define buf_head buf_anchor.next
	55	#define buf_tail buf_anchor.prev
	56
	57	static struct {
	58	struct buf next, prev;
	59	} buf_anchor = { END_OF_CHAIN, END_OF_CHAIN };
	60
	61	extern int clean_data;
	62	extern int ispipe;
	63	extern int autobuf;
	64	extern int cbufs;
	65	extern int sigs;
bfe13c81 KB	66
	67	/*
	68	* Current position in file.
	69	* Stored as a block number and an offset into the block.
	70	*/
	71	static long ch_block;
	72	static int ch_offset;
	73
	74	/*
	75	* Length of file, needed if input is a pipe.
	76	*/
	77	static POSITION ch_fsize;
	78
	79	/*
	80	* Number of bytes read, if input is standard input (a pipe).
	81	*/
	82	static POSITION last_piped_pos;
	83
	84	/*
	85	* Get the character pointed to by the read pointer.
	86	* ch_get() is a macro which is more efficient to call
	87	* than fch_get (the function), in the usual case
	88	* that the block desired is at the head of the chain.
	89	*/
	90	#define ch_get() ((buf_head->block == ch_block && \
	91	ch_offset < buf_head->datasize) ? \
	92	buf_head->data[ch_offset] : fch_get())
	93	static int
	94	fch_get()
	95	{
	96	register struct buf *bp;
	97	register int n;
	98	register char *p;
	99	POSITION pos;
	100
	101	/*
	102	* Look for a buffer holding the desired block.
	103	*/
	104	for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
	105	if (bp->block == ch_block)
	106	{
	107	if (ch_offset >= bp->datasize)
	108	/*
	109	* Need more data in this buffer.
	110	*/
	111	goto read_more;
	112	/*
	113	* On a pipe, we don't sort the buffers LRU
	114	* because this can cause gaps in the buffers.
	115	* For example, suppose we've got 12 1K buffers,
	116	* and a 15K input stream. If we read the first 12K
	117	* sequentially, then jump to line 1, then jump to
	118	* the end, the buffers have blocks 0,4,5,6,..,14.
	119	* If we then jump to line 1 again and try to
	120	* read sequentially, we're out of luck when we
	121	* get to block 1 (we'd get the "pipe error" below).
	122	* To avoid this, we only sort buffers on a pipe
	123	* when we actually READ the data, not when we
	124	* find it already buffered.
	125	*/
	126	if (ispipe)
	127	return (bp->data[ch_offset]);
	128	goto found;
	129	}
130	/*
131	* Block is not in a buffer.
132	* Take the least recently used buffer
133	* and read the desired block into it.
134	* If the LRU buffer has data in it,
135	* and autobuf is true, and input is a pipe,
136	* then try to allocate a new buffer first.
137	*/
138	if (autobuf && ispipe && buf_tail->block != (long)(-1))
139	(void) ch_addbuf(1);
140	bp = buf_tail;
141	bp->block = ch_block;
142	bp->datasize = 0;
143
144	read_more:
145	pos = (ch_block * BUFSIZ) + bp->datasize;
146	if (ispipe)
147	{
148	/*
149	* The data requested should be immediately after
150	* the last data read from the pipe.
151	*/
152	if (pos != last_piped_pos)
153	{
154	error("pipe error");
155	quit();
156	}
157	} else
083e784b	158	(void)lseek(file, pos, L_SET);
bfe13c81 KB	159
	160	/*
	161	* Read the block.
	162	* If we read less than a full block, we just return the
	163	* partial block and pick up the rest next time.
	164	*/
	165	n = iread(file, &bp->data[bp->datasize], BUFSIZ - bp->datasize);
	166	if (n == READ_INTR)
	167	return (EOI);
	168	if (n < 0)
	169	{
	170	error("read error");
	171	quit();
	172	}
	173	if (ispipe)
	174	last_piped_pos += n;
	175
bfe13c81 KB	176	bp->datasize += n;
	177
	178	/*
	179	* Set an EOI marker in the buffered data itself.
	180	* Then ensure the data is "clean": there are no
	181	* extra EOI chars in the data and that the "meta"
	182	* bit (the 0200 bit) is reset in each char.
	183	*/
	184	if (n == 0)
	185	{
	186	ch_fsize = pos;
	187	bp->data[bp->datasize++] = EOI;
	188	}
	189
	190	if (!clean_data)
	191	{
	192	p = &bp->data[bp->datasize];
	193	while (--n >= 0)
	194	{
	195	*--p &= 0177;
	196	if (*p == EOI)
	197	*p = '@';
	198	}
	199	}
	200
	201	found:
	202	if (buf_head != bp)
	203	{
	204	/*
	205	* Move the buffer to the head of the buffer chain.
	206	* This orders the buffer chain, most- to least-recently used.
	207	*/
	208	bp->next->prev = bp->prev;
	209	bp->prev->next = bp->next;
	210
	211	bp->next = buf_head;
	212	bp->prev = END_OF_CHAIN;
	213	buf_head->prev = bp;
	214	buf_head = bp;
	215	}
	216
	217	if (ch_offset >= bp->datasize)
	218	/*
	219	* After all that, we still don't have enough data.
	220	* Go back and try again.
	221	*/
	222	goto read_more;
	223
	224	return (bp->data[ch_offset]);
	225	}
	226
bfe13c81 KB	227	/*
	228	* Determine if a specific block is currently in one of the buffers.
	229	*/
	230	static int
	231	buffered(block)
	232	long block;
	233	{
	234	register struct buf *bp;
	235
	236	for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
	237	if (bp->block == block)
	238	return (1);
	239	return (0);
	240	}
	241
	242	/*
	243	* Seek to a specified position in the file.
	244	* Return 0 if successful, non-zero if can't seek there.
	245	*/
	246	public int
	247	ch_seek(pos)
	248	register POSITION pos;
	249	{
	250	long new_block;
	251
	252	new_block = pos / BUFSIZ;
	253	if (!ispipe \|\| pos == last_piped_pos \|\| buffered(new_block))
	254	{
	255	/*
	256	* Set read pointer.
	257	*/
	258	ch_block = new_block;
	259	ch_offset = pos % BUFSIZ;
	260	return (0);
	261	}
	262	return (1);
	263	}
	264
	265	/*
	266	* Seek to the end of the file.
	267	*/
	268	public int
	269	ch_end_seek()
	270	{
	271	if (!ispipe)
	272	return (ch_seek(ch_length()));
	273
	274	/*
	275	* Do it the slow way: read till end of data.
	276	*/
	277	while (ch_forw_get() != EOI)
	278	if (sigs)
	279	return (1);
	280	return (0);
	281	}
	282
	283	/*
	284	* Seek to the beginning of the file, or as close to it as we can get.
	285	* We may not be able to seek there if input is a pipe and the
	286	* beginning of the pipe is no longer buffered.
	287	*/
	288	public int
	289	ch_beg_seek()
	290	{
291	register struct buf bp, firstbp;
292
293	/*
294	* Try a plain ch_seek first.
295	*/
296	if (ch_seek((POSITION)0) == 0)
297	return (0);
298
299	/*
300	* Can't get to position 0.
301	* Look thru the buffers for the one closest to position 0.
302	*/
303	firstbp = bp = buf_head;
304	if (bp == END_OF_CHAIN)
305	return (1);
306	while ((bp = bp->next) != END_OF_CHAIN)
307	if (bp->block < firstbp->block)
308	firstbp = bp;
309	ch_block = firstbp->block;
310	ch_offset = 0;
311	return (0);
312	}
313
314	/*
315	* Return the length of the file, if known.
316	*/
317	public POSITION
318	ch_length()
319	{
320	if (ispipe)
321	return (ch_fsize);
51eb338d	322	return ((POSITION)(lseek(file, (off_t)0, L_XTND)));
bfe13c81 KB	323	}
	324
	325	/*
	326	* Return the current position in the file.
	327	*/
	328	public POSITION
	329	ch_tell()
	330	{
	331	return (ch_block * BUFSIZ + ch_offset);
	332	}
	333
	334	/*
	335	* Get the current char and post-increment the read pointer.
	336	*/
	337	public int
	338	ch_forw_get()
	339	{
	340	register int c;
	341
	342	c = ch_get();
	343	if (c != EOI && ++ch_offset >= BUFSIZ)
	344	{
	345	ch_offset = 0;
	346	ch_block ++;
	347	}
	348	return (c);
	349	}
	350
	351	/*
	352	* Pre-decrement the read pointer and get the new current char.
	353	*/
	354	public int
	355	ch_back_get()
	356	{
	357	if (--ch_offset < 0)
	358	{
	359	if (ch_block <= 0 \|\| (ispipe && !buffered(ch_block-1)))
	360	{
	361	ch_offset = 0;
	362	return (EOI);
	363	}
	364	ch_offset = BUFSIZ - 1;
	365	ch_block--;
	366	}
	367	return (ch_get());
	368	}
	369
	370	/*
	371	* Allocate buffers.
	372	* Caller wants us to have a total of at least want_nbufs buffers.
	373	* keep==1 means keep the data in the current buffers;
	374	* otherwise discard the old data.
	375	*/
	376	public void
	377	ch_init(want_nbufs, keep)
	378	int want_nbufs;
	379	int keep;
	380	{
	381	register struct buf *bp;
	382	char message[80];
	383
	384	cbufs = nbufs;
	385	if (nbufs < want_nbufs && ch_addbuf(want_nbufs - nbufs))
	386	{
387	/*
388	* Cannot allocate enough buffers.
389	* If we don't have ANY, then quit.
390	* Otherwise, just report the error and return.
391	*/
083e784b	392	(void)sprintf(message, "cannot allocate %d buffers",
bfe13c81 KB	393	want_nbufs - nbufs);
	394	error(message);
	395	if (nbufs == 0)
	396	quit();
	397	return;
	398	}
	399
	400	if (keep)
	401	return;
	402
	403	/*
	404	* We don't want to keep the old data,
	405	* so initialize all the buffers now.
	406	*/
	407	for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
	408	bp->block = (long)(-1);
	409	last_piped_pos = (POSITION)0;
	410	ch_fsize = NULL_POSITION;
	411	(void) ch_seek((POSITION)0);
	412	}
	413
	414	/*
	415	* Allocate some new buffers.
	416	* The buffers are added to the tail of the buffer chain.
	417	*/
	418	static int
	419	ch_addbuf(nnew)
	420	int nnew;
	421	{
	422	register struct buf *bp;
	423	register struct buf *newbufs;
	424
	425	/*
	426	* We don't have enough buffers.
	427	* Allocate some new ones.
	428	*/
083e784b	429	newbufs = (struct buf *) calloc((u_int)nnew, sizeof(struct buf));
bfe13c81 KB	430	if (newbufs == NULL)
	431	return (1);
	432
	433	/*
	434	* Initialize the new buffers and link them together.
	435	* Link them all onto the tail of the buffer list.
	436	*/
	437	nbufs += nnew;
	438	cbufs = nbufs;
	439	for (bp = &newbufs[0]; bp < &newbufs[nnew]; bp++)
	440	{
	441	bp->next = bp + 1;
	442	bp->prev = bp - 1;
	443	bp->block = (long)(-1);
	444	}
	445	newbufs[nnew-1].next = END_OF_CHAIN;
	446	newbufs[0].prev = buf_tail;
	447	buf_tail->next = &newbufs[0];
	448	buf_tail = &newbufs[nnew-1];
	449	return (0);
	450	}