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switch to xmalloc stuff, me and xsa@ agreed on this a long
time ago, but we were being held back by jfb. too bad for him.

next step is to use fatal() through out the code for unrecoverable
errors instead of trying to be all nice and fluffy and reach main() again.

ok niallo@ and xsa@

/*	$OpenBSD: buf.c,v 1.19 2005/12/10 20:27:45 joris Exp $	*/
/*
 * Copyright (c) 2003 Jean-Francois Brousseau <jfb@openbsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. The name of the author 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 ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL  DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/stat.h>

#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "buf.h"
#include "log.h"
#include "xmalloc.h"

#define BUF_INCR	128


struct cvs_buf {
	u_int	cb_flags;

	/* buffer handle and size */
	u_char	*cb_buf;
	size_t	 cb_size;

	/* start and length of valid data in buffer */
	u_char	*cb_cur;
	size_t	 cb_len;
};


#define SIZE_LEFT(b)	(b->cb_size - (size_t)(b->cb_cur - b->cb_buf) \
			    - b->cb_len)


static ssize_t	cvs_buf_grow(BUF *, size_t);



/*
 * cvs_buf_alloc()
 *
 * Create a new buffer structure and return a pointer to it.  This structure
 * uses dynamically-allocated memory and must be freed with cvs_buf_free(),
 * once the buffer is no longer needed.
 */
BUF *
cvs_buf_alloc(size_t len, u_int flags)
{
	BUF *b;

	b = (BUF *)xmalloc(sizeof(*b));
	b->cb_buf = xmalloc(len);
	memset(b->cb_buf, 0, len);

	b->cb_flags = flags;
	b->cb_size = len;
	b->cb_cur = b->cb_buf;
	b->cb_len = 0;

	return (b);
}


/*
 * cvs_buf_load()
 *
 * Open the file specified by <path> and load all of its contents into a
 * buffer.
 * Returns the loaded buffer on success, or NULL on failure.
 */
BUF *
cvs_buf_load(const char *path, u_int flags)
{
	int fd;
	ssize_t ret;
	size_t len;
	u_char *bp;
	struct stat st;
	BUF *buf;

	fd = open(path, O_RDONLY, 0600);
	if (fd == -1) {
		cvs_log(LP_ERRNO, "failed to open buffer source");
		return (NULL);
	}

	if (fstat(fd, &st) == -1) {
		cvs_log(LP_ERRNO, "failed to stat buffer source");
		(void)close(fd);
		return (NULL);
	}

	buf = cvs_buf_alloc((size_t)st.st_size, flags);
	if (buf == NULL) {
		(void)close(fd);
		return (NULL);
	}

	for (bp = buf->cb_cur; ; bp += (size_t)ret) {
		len = SIZE_LEFT(buf);
		ret = read(fd, bp, len);
		if (ret == -1) {
			cvs_log(LP_ERRNO, "read failed from buffer source");
			(void)close(fd);
			cvs_buf_free(buf);
			return (NULL);
		} else if (ret == 0)
			break;

		buf->cb_len += (size_t)ret;
	}

	(void)close(fd);

	return (buf);
}


/*
 * cvs_buf_free()
 *
 * Free the buffer <b> and all associated data.
 */
void
cvs_buf_free(BUF *b)
{
	xfree(b->cb_buf);
	xfree(b);
}


/*
 * cvs_buf_release()
 *
 * Free the buffer <b>'s structural information but do not free the contents
 * of the buffer.  Instead, they are returned and should be freed later using
 * free().
 */
void *
cvs_buf_release(BUF *b)
{
	u_char *tmp;

	tmp = b->cb_buf;
	xfree(b);
	return (tmp);
}


/*
 * cvs_buf_empty()
 *
 * Empty the contents of the buffer <b> and reset pointers.
 */
void
cvs_buf_empty(BUF *b)
{
	memset(b->cb_buf, 0, b->cb_size);
	b->cb_cur = b->cb_buf;
	b->cb_len = 0;
}


/*
 * cvs_buf_copy()
 *
 * Copy the first <len> bytes of data in the buffer <b> starting at offset
 * <off> in the destination buffer <dst>, which can accept up to <len> bytes.
 * Returns the number of bytes successfully copied, or -1 on failure.
 */
ssize_t
cvs_buf_copy(BUF *b, size_t off, void *dst, size_t len)
{
	size_t rc;

	if (off > b->cb_len)
		return (-1);

	rc = MIN(len, (b->cb_len - off));
	memcpy(dst, b->cb_buf + off, rc);

	return (ssize_t)rc;
}


/*
 * cvs_buf_set()
 *
 * Set the contents of the buffer <b> at offset <off> to the first <len>
 * bytes of data found at <src>.  If the buffer was not created with
 * BUF_AUTOEXT, as many bytes as possible will be copied in the buffer.
 */
ssize_t
cvs_buf_set(BUF *b, const void *src, size_t len, size_t off)
{
	size_t rlen;

	if (b->cb_size < (len + off)) {
		if ((b->cb_flags & BUF_AUTOEXT) && (cvs_buf_grow(b,
		    len + off - b->cb_size) < 0))
			return (-1);
		else
			rlen = b->cb_size - off;
	} else
		rlen = len;

	memcpy((b->cb_buf + off), src, rlen);

	if (b->cb_len == 0) {
		b->cb_cur = b->cb_buf + off;
		b->cb_len = rlen;
	}

	return (rlen);
}


/*
 * cvs_buf_putc()
 *
 * Append a single character <c> to the end of the buffer <b>.
 * Returns 0 on success, or -1 on failure.
 */
int
cvs_buf_putc(BUF *b, int c)
{
	u_char *bp;

	bp = b->cb_cur + b->cb_len;
	if (bp == (b->cb_buf + b->cb_size)) {
		/* extend */
		if (!(b->cb_flags & BUF_AUTOEXT) ||
		    (cvs_buf_grow(b, (size_t)BUF_INCR) < 0))
			return (-1);

		/* the buffer might have been moved */
		bp = b->cb_cur + b->cb_len;
	}
	*bp = (u_char)c;
	b->cb_len++;

	return (0);
}


/*
 * cvs_buf_append()
 *
 * Append <len> bytes of data pointed to by <data> to the buffer <b>.  If the
 * buffer is too small to accept all data, it will attempt to append as much
 * data as possible, or if the BUF_AUTOEXT flag is set for the buffer, it
 * will get resized to an appropriate size to accept all data.
 * Returns the number of bytes successfully appended to the buffer, or -1
 * on failure.
 */
ssize_t
cvs_buf_append(BUF *b, const void *data, size_t len)
{
	size_t left, rlen;
	u_char *bp, *bep;

	bp = b->cb_cur + b->cb_len;
	bep = b->cb_buf + b->cb_size;
	left = bep - bp;
	rlen = len;

	if (left < len) {
		if (b->cb_flags & BUF_AUTOEXT) {
			if (cvs_buf_grow(b, len - left) < 0)
				return (-1);
			bp = b->cb_cur + b->cb_len;
		} else
			rlen = bep - bp;
	}

	memcpy(bp, data, rlen);
	b->cb_len += rlen;

	return (rlen);
}


/*
 * cvs_buf_fappend()
 *
 */
int
cvs_buf_fappend(BUF *b, const char *fmt, ...)
{
	int ret;
	char *str;
	va_list vap;

	va_start(vap, fmt);
	ret = vasprintf(&str, fmt, vap);
	va_end(vap);

	if (ret == -1) {
		cvs_log(LP_ERRNO, "failed to format data");
		return (-1);
	}

	ret = cvs_buf_append(b, str, (size_t)ret);
	xfree(str);
	return (ret);
}


/*
 * cvs_buf_len()
 *
 * Returns the size of the buffer that is being used.
 */
size_t
cvs_buf_len(BUF *b)
{
	return (b->cb_len);
}


/*
 * cvs_buf_peek()
 *
 * Peek at the contents of the buffer <b> at offset <off>.
 */
const void *
cvs_buf_peek(BUF *b, size_t off)
{
	if (off >= b->cb_len)
		return (NULL);

	return (b->cb_buf + off);
}


/*
 * cvs_buf_write_fd()
 *
 * Write the contents of the buffer <b> to the specified <fd>
 */
int
cvs_buf_write_fd(BUF *b, int fd)
{
	u_char *bp;
	size_t len;
	ssize_t ret;

	len = b->cb_len;
	bp = b->cb_cur;

	do {
		ret = write(fd, bp, len);
		if (ret == -1) {
			if (errno == EINTR || errno == EAGAIN)
				continue;
			return (-1);
		}

		len -= (size_t)ret;
		bp += (size_t)ret;
	} while (len > 0);

	return (0);
}

/*
 * cvs_buf_write()
 *
 * Write the contents of the buffer <b> to the file whose path is given in
 * <path>.  If the file does not exist, it is created with mode <mode>.
 */

int
cvs_buf_write(BUF *b, const char *path, mode_t mode)
{
	int ret, fd;

	fd = open(path, O_WRONLY|O_CREAT|O_TRUNC, mode);
	if (fd == -1) {
		cvs_log(LP_ERRNO, "failed to open file `%s'", path);
		return (-1);
	}

	ret = cvs_buf_write_fd(b, fd);
	if (ret == -1) {
		cvs_log(LP_ERRNO, "failed to write to file `%s'",  path);
		(void)unlink(path);
	}
	(void)close(fd);

	return (ret);
}

/*
 * cvs_buf_write_stmp()
 *
 * Write the contents of the buffer <b> to a temporary file whose path is
 * specified using <template> (see mkstemp.3). NB. This function will modify
 * <template>, as per mkstemp
 */

int
cvs_buf_write_stmp(BUF *b, char *template, mode_t mode)
{
	int ret, fd;

	fd = mkstemp(template);
	if (fd == -1) {
		cvs_log(LP_ERRNO, "failed to mkstemp file `%s'", template);
		return (-1);
	}

	ret = cvs_buf_write_fd(b, fd);
	if (ret == -1) {
		cvs_log(LP_ERRNO, "failed to write to temp file `%s'",
		    template);
		(void)unlink(template);
	}
	(void)close(fd);

	return (ret);
}

/*
 * cvs_buf_grow()
 *
 * Grow the buffer <b> by <len> bytes.  The contents are unchanged by this
 * operation regardless of the result.
 * Returns the new size on success, or -1 on failure.
 */
static ssize_t
cvs_buf_grow(BUF *b, size_t len)
{
	void *tmp;
	size_t diff;

	diff = b->cb_cur - b->cb_buf;
	tmp = xrealloc(b->cb_buf, b->cb_size + len);
	b->cb_buf = (u_char *)tmp;
	b->cb_size += len;

	/* readjust pointers in case the buffer moved in memory */
	b->cb_cur = b->cb_buf + diff;

	return (ssize_t)b->cb_size;
}