1/*
2 * Copyright (c) Christos Zoulas 2017.
3 * All Rights Reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice immediately at the beginning of the file, without modification,
10 *    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 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
19 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27#include "file.h"
28
29#ifndef	lint
30FILE_RCSID("@(#)$File: buffer.c,v 1.7 2019/06/10 21:35:26 christos Exp $")
31#endif	/* lint */
32
33#include "magic.h"
34#include <unistd.h>
35#include <string.h>
36#include <stdlib.h>
37#include <sys/stat.h>
38
39void
40buffer_init(struct buffer *b, int fd, const struct stat *st, const void *data,
41    size_t len)
42{
43	b->fd = fd;
44	if (st)
45		memcpy(&b->st, st, sizeof(b->st));
46	else if (b->fd == -1 || fstat(b->fd, &b->st) == -1)
47		memset(&b->st, 0, sizeof(b->st));
48	b->fbuf = data;
49	b->flen = len;
50	b->eoff = 0;
51	b->ebuf = NULL;
52	b->elen = 0;
53}
54
55void
56buffer_fini(struct buffer *b)
57{
58	free(b->ebuf);
59}
60
61int
62buffer_fill(const struct buffer *bb)
63{
64	struct buffer *b = CCAST(struct buffer *, bb);
65
66	if (b->elen != 0)
67		return b->elen == CAST(size_t, ~0) ? -1 : 0;
68
69	if (!S_ISREG(b->st.st_mode))
70		goto out;
71
72	b->elen =  CAST(size_t, b->st.st_size) < b->flen ?
73	    CAST(size_t, b->st.st_size) : b->flen;
74	if ((b->ebuf = malloc(b->elen)) == NULL)
75		goto out;
76
77	b->eoff = b->st.st_size - b->elen;
78	if (pread(b->fd, b->ebuf, b->elen, b->eoff) == -1) {
79		free(b->ebuf);
80		b->ebuf = NULL;
81		goto out;
82	}
83
84	return 0;
85out:
86	b->elen = CAST(size_t, ~0);
87	return -1;
88}
89