1#include "stdio_impl.h"
2#include <errno.h>
3#include <string.h>
4#include <stdlib.h>
5#include <stddef.h>
6#include <inttypes.h>
7#include "libc.h"
8
9struct cookie {
10	size_t pos, len, size;
11	unsigned char *buf;
12	int mode;
13};
14
15struct mem_FILE {
16	FILE f;
17	struct cookie c;
18	unsigned char buf[UNGET+BUFSIZ], buf2[];
19};
20
21static off_t mseek(FILE *f, off_t off, int whence)
22{
23	ssize_t base;
24	struct cookie *c = f->cookie;
25	if (whence>2U) {
26fail:
27		errno = EINVAL;
28		return -1;
29	}
30	base = (size_t [3]){0, c->pos, c->len}[whence];
31	if (off < -base || off > (ssize_t)c->size-base) goto fail;
32	return c->pos = base+off;
33}
34
35static size_t mread(FILE *f, unsigned char *buf, size_t len)
36{
37	struct cookie *c = f->cookie;
38	size_t rem = c->len - c->pos;
39	if (c->pos > c->len) rem = 0;
40	if (len > rem) {
41		len = rem;
42		f->flags |= F_EOF;
43	}
44	memcpy(buf, c->buf+c->pos, len);
45	c->pos += len;
46	rem -= len;
47	if (rem > f->buf_size) rem = f->buf_size;
48	f->rpos = f->buf;
49	f->rend = f->buf + rem;
50	memcpy(f->rpos, c->buf+c->pos, rem);
51	c->pos += rem;
52	return len;
53}
54
55static size_t mwrite(FILE *f, const unsigned char *buf, size_t len)
56{
57	struct cookie *c = f->cookie;
58	size_t rem;
59	size_t len2 = f->wpos - f->wbase;
60	if (len2) {
61		f->wpos = f->wbase;
62		if (mwrite(f, f->wpos, len2) < len2) return 0;
63	}
64	if (c->mode == 'a') c->pos = c->len;
65	rem = c->size - c->pos;
66	if (len > rem) len = rem;
67	memcpy(c->buf+c->pos, buf, len);
68	c->pos += len;
69	if (c->pos > c->len) {
70		c->len = c->pos;
71		if (c->len < c->size) c->buf[c->len] = 0;
72		else if ((f->flags&F_NORD) && c->size) c->buf[c->size-1] = 0;
73	}
74	return len;
75}
76
77static int mclose(FILE *m)
78{
79	return 0;
80}
81
82FILE *fmemopen(void *restrict buf, size_t size, const char *restrict mode)
83{
84	struct mem_FILE *f;
85	int plus = !!strchr(mode, '+');
86
87	if (!strchr("rwa", *mode)) {
88		errno = EINVAL;
89		return 0;
90	}
91
92	if (!buf && size > PTRDIFF_MAX) {
93		errno = ENOMEM;
94		return 0;
95	}
96
97	f = malloc(sizeof *f + (buf?0:size));
98	if (!f) return 0;
99	memset(f, 0, offsetof(struct mem_FILE, buf));
100	f->f.cookie = &f->c;
101	f->f.fd = -1;
102	f->f.lbf = EOF;
103	f->f.buf = f->buf + UNGET;
104	f->f.buf_size = sizeof f->buf - UNGET;
105	if (!buf) {
106		buf = f->buf2;
107		memset(buf, 0, size);
108	}
109
110	f->c.buf = buf;
111	f->c.size = size;
112	f->c.mode = *mode;
113
114	if (!plus) f->f.flags = (*mode == 'r') ? F_NOWR : F_NORD;
115	if (*mode == 'r') f->c.len = size;
116	else if (*mode == 'a') f->c.len = f->c.pos = strnlen(buf, size);
117	else if (plus) *f->c.buf = 0;
118
119	f->f.read = mread;
120	f->f.readx = mread;
121	f->f.write = mwrite;
122	f->f.seek = mseek;
123	f->f.close = mclose;
124
125	if (!libc.threaded) f->f.lock = -1;
126
127	return __ofl_add(&f->f);
128}
129