1/*	$OpenBSD: fmemopen.c,v 1.5 2020/08/17 16:17:39 millert Exp $	*/
2
3/*
4 * Copyright (c) 2011 Martin Pieuchot <mpi@openbsd.org>
5 * Copyright (c) 2009 Ted Unangst
6 *
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18 */
19
20#include <errno.h>
21#include <fcntl.h>
22#include <stdio.h>
23#include <stdlib.h>
24#include <string.h>
25#include "local.h"
26
27struct state {
28	char		*string;	/* actual stream */
29	size_t		 pos;		/* current position */
30	size_t		 size;		/* allocated size */
31	size_t		 len;		/* length of the data */
32	int		 update;	/* open for update */
33	int		 append;	/* open for append */
34};
35
36static int
37fmemopen_read(void *v, char *b, int l)
38{
39	struct state	*st = v;
40	int		 i;
41
42	for (i = 0; i < l && i + st->pos < st->len; i++)
43		b[i] = st->string[st->pos + i];
44	st->pos += i;
45
46	return (i);
47}
48
49static int
50fmemopen_write(void *v, const char *b, int l)
51{
52	struct state	*st = v;
53	int		i;
54
55	if (st->append)
56		st->pos = st->len;
57
58	for (i = 0; i < l && i + st->pos < st->size; i++)
59		st->string[st->pos + i] = b[i];
60	st->pos += i;
61
62	if (st->pos >= st->len) {
63		st->len = st->pos;
64
65		if (st->len < st->size)
66			st->string[st->len] = '\0';
67		else if (!st->update)
68			st->string[st->size - 1] = '\0';
69	}
70
71	return (i);
72}
73
74static fpos_t
75fmemopen_seek(void *v, fpos_t off, int whence)
76{
77	struct state	*st = v;
78	ssize_t		 base = 0;
79
80	switch (whence) {
81	case SEEK_SET:
82		break;
83	case SEEK_CUR:
84		base = st->pos;
85		break;
86	case SEEK_END:
87		base = st->len;
88		break;
89	}
90
91	if (off > st->size - base || off < -base) {
92		errno = EOVERFLOW;
93		return (-1);
94	}
95
96	st->pos = base + off;
97
98	return (st->pos);
99}
100
101static int
102fmemopen_close(void *v)
103{
104	free(v);
105
106	return (0);
107}
108
109static int
110fmemopen_close_free(void *v)
111{
112	struct state	*st = v;
113
114	free(st->string);
115	free(st);
116
117	return (0);
118}
119
120FILE *
121fmemopen(void *buf, size_t size, const char *mode)
122{
123	struct state	*st;
124	FILE		*fp;
125	int		 flags, oflags;
126
127	if (size == 0) {
128		errno = EINVAL;
129		return (NULL);
130	}
131
132	if ((flags = __sflags(mode, &oflags)) == 0) {
133		errno = EINVAL;
134		return (NULL);
135	}
136
137	if (buf == NULL && ((oflags & O_RDWR) == 0)) {
138		errno = EINVAL;
139		return (NULL);
140	}
141
142	if ((st = malloc(sizeof(*st))) == NULL)
143		return (NULL);
144
145	if ((fp = __sfp()) == NULL) {
146		free(st);
147		return (NULL);
148	}
149
150	st->pos = 0;
151	st->len = (oflags & O_TRUNC) ? 0 : size;
152	st->size = size;
153	st->update = oflags & O_RDWR;
154	st->append = oflags & O_APPEND;
155
156	if (buf == NULL) {
157		if ((st->string = malloc(size)) == NULL) {
158			free(st);
159			fp->_flags = 0;
160			return (NULL);
161		}
162		*st->string = '\0';
163	} else {
164		st->string = (char *)buf;
165
166		if (oflags & O_TRUNC)
167			*st->string = '\0';
168
169		if (oflags & O_APPEND) {
170			char	*p;
171
172			if ((p = memchr(st->string, '\0', size)) != NULL)
173				st->pos = st->len = (p - st->string);
174			else
175				st->pos = st->len = size;
176		}
177	}
178
179	fp->_flags = (short)flags;
180	fp->_file = -1;
181	fp->_cookie = st;
182	fp->_read = (flags & __SWR) ? NULL : fmemopen_read;
183	fp->_write = (flags & __SRD) ? NULL : fmemopen_write;
184	fp->_seek = fmemopen_seek;
185	fp->_close = (buf == NULL) ? fmemopen_close_free : fmemopen_close;
186
187	return (fp);
188}
189DEF_WEAK(fmemopen);
190