es_util.c

操作系统SunOS 4.1.3版本的源码

#ifndef lint
#ifdef sccs
static  char sccsid[] = "@(#)es_util.c 1.1 92/07/30";
#endif
#endif

/*
 * Copyright (c) 1986, 1987 by Sun Microsystems, Inc.
 */

/*
 * Utilities for use with entity streams.
 */

#include <suntool/primal.h>
#include <suntool/entity_stream.h>

extern Es_index
es_bounds_of_gap(esh, around, last_plus_one, flags)
	register Es_handle	 esh;
	Es_index		 around;
	Es_index		*last_plus_one;
	int			 flags;
/* If there is no gap, then around == return value == *last_plus_one.
 * Else, if not looking for the start of the gap (flags & 0x1 == 0),
 *   around < return value == *last_plus_one.
 * Else, if looking for the start of the gap,
 *   return value <= around <= *last_plus_one
 *   (return value will be ES_CANNOT_SET if gap extends from 0 on).
 */
{
#define BUFSIZE 32
	char			buf[BUFSIZE+4];
	int			count_read;
	register Es_index	new_pos, low, high, probe;

	low = es_set_position(esh, around);
	new_pos = es_read(esh, 1, buf, &count_read);
	if (count_read == 0) {
	    low = new_pos;
	}
	if (last_plus_one)
	    *last_plus_one = low;
	if ((low != around) && (flags & 0x1) &&
	    !READ_AT_EOF(around, new_pos, count_read)) {
	    /* Try binary search to locate the start of the gap.
	     * Invariants for loop:
	     *   0 <= low <= start of gap <= high <= around
	     *   low < probe = (high + low) / 2 < high
	     * Essentially, choose a probe point and try to read. 3 cases:
	     *   1) new_pos < around: null, partial or full read
	     *      => low = new_pos;
	     *         if low >=high, gap starts at probe+count_read
	     *   2) new_pos > around: null read
	     *      => high = probe
	     *   3) new_pos > around: partial read
	     *      => gap starts at probe+count_read
	     *   "new_pos == around || (new_pos > around: full read)"
	     *      impossible as there is gap
	     */
	    low = 0;
	    high = around;
	    while (low+1 < high) {
		probe = es_set_position(esh, (high+low)/2);
		new_pos = es_read(esh, BUFSIZE, buf, &count_read);
		if (new_pos < around) {
		    if (new_pos >= high) {
			low = probe+count_read;
			break;
		    } else {
			low = new_pos;
		    }
		} else if (count_read == 0) {
		    high = probe;
		} else {
		    low = probe+count_read;
		    break;
		}
	    }
	    if (low == 0) {
		probe = es_set_position(esh, 0);
		new_pos = es_read(esh, BUFSIZE, buf, &count_read);
		if (count_read == 0)
		    low == ES_CANNOT_SET;
	    }
	}
	return(low);
#undef BUFSIZE
}

/* Caller must make sure that esbuf->last_plus_one is the current position
 *   in the entity stream.
 */
extern int
es_advance_buf(esbuf)
	Es_buf_handle	esbuf;
{
	int			read = 0;
	register Es_index	next = esbuf->last_plus_one;
	while (read == 0) {
	    esbuf->first = next;
	    next = es_read(esbuf->esh, esbuf->sizeof_buf, esbuf->buf, &read);
	    esbuf->last_plus_one = esbuf->first + read;
	    if READ_AT_EOF(esbuf->first, next, read) {
		return(1);
	    }
	}
	return(0);
}

extern Es_index
es_backup_buf(esbuf)
	Es_buf_handle	esbuf;
{
/* Move buffer back in stream (i.e., change so that esbuf->first is smaller).
 * Backing the buffer up is complicated by possible gap before the current
 *   beginning of the buffer.
 * This routine moves over such a gap.
 */
	register Es_index	prev;
	register Es_index	esi = esbuf->first-1;

Retry:
	switch (es_make_buf_include_index(esbuf, esi, esbuf->sizeof_buf-1)) {
	  case 0:
	    break;
	  case 2:
	    prev = esi;
	    esi = es_bounds_of_gap(esbuf->esh, prev, 0, 0x1);
	    if (esi != ES_CANNOT_SET && esi < prev) {
		goto Retry;
	    }
	    /* else gap extends back to 0 OR unexpected error
	     *  => fall through.
	     */
	  case 1:
	  default:		    /* Conservative in face of new cases */
	    esi = ES_CANNOT_SET;
	    break;
	}
	return(esi);
}

/* esbuf->first and ->last_plus_one are only adjusted when entities are
 *   actually read.  This makes it easier for callers to figure out how to
 *   correct after failure to re-position a buffer.
 * Returns:
 *  0	iff it managed to align the buffer as requested,
 *  1	if read at end of stream while trying to align,
 *  2	if desired entity is in a "hole" in the stream.
 */
extern int
es_make_buf_include_index(esbuf, index, desired_prior_count)
	register Es_buf_handle	esbuf;
	Es_index		index;
	int			desired_prior_count;
{
	register Es_index	last_plus_one, next;
	int			read;

	last_plus_one = (desired_prior_count > index) ? 0
			: index - desired_prior_count;
	es_set_position(esbuf->esh, last_plus_one);
	FOREVER {
	    next = es_read(esbuf->esh, esbuf->sizeof_buf, esbuf->buf, &read);
	    if READ_AT_EOF(last_plus_one, next, read)
		return(1);
	    esbuf->first = last_plus_one;
	    esbuf->last_plus_one = last_plus_one+read;
	    if (next > index) {
		if (esbuf->last_plus_one < index) {
		    return(2);
		} else
		    return(0);
	    }
	    last_plus_one = next;
	}
}

extern Es_status
es_copy(from, to, newline_must_terminate)
	register Es_handle	from, to;
	int			newline_must_terminate;
{
#define BUFSIZE 2096
	char			buf[BUFSIZE+4];
	register Es_status	result;
	int			read, write;
	Es_index		new_pos, pos, to_pos;

	/* Find start of "from" (it need not actually be 0, e.g. secondary
	 * pieces that compose a selection)
	 */
	pos = es_set_position(from, 0);
	write = 0;
	/* Cannot just "es_replace(to, ES_INFINITY, ...)" in case not copying
	 * at the end of "to", so get (and maintain) current position in "to".
	 */
	to_pos = es_get_position(to);
	FOREVER {
	    new_pos = es_read(from, BUFSIZE, buf, &read);
	    if (read > 0) {
		to_pos = es_replace(to, to_pos, read, buf, &write);
		if (write < read) {
		    result = ES_SHORT_WRITE;
		    return(result);
		}
	    } else if (pos == new_pos)
		break;
	    pos = new_pos;
	}
	if (newline_must_terminate && (
	    (write <= 0) || (write > sizeof(buf)) ||
	    (buf[write-1] != '\n') )) {
	    buf[0] = '\n';
	    (void) es_replace(to, ES_INFINITY, 1, buf, &write);
	    if (write < 1) {
		result = ES_SHORT_WRITE;
		return(result);
	    }
	}
	result = es_commit(to);
	return(result);
#undef BUFSIZE
}