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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 
9 struct cookie {
10 	size_t pos, len, size;
11 	unsigned char *buf;
12 	int mode;
13 };
14 
15 struct mem_FILE {
16 	FILE f;
17 	struct cookie c;
18 	unsigned char buf[UNGET+BUFSIZ], buf2[];
19 };
20 
mseek(FILE * f,off_t off,int whence)21 static 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) {
26 fail:
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 
mread(FILE * f,unsigned char * buf,size_t len)35 static 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 
mwrite(FILE * f,const unsigned char * buf,size_t len)55 static 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 
mclose(FILE * m)77 static int mclose(FILE *m)
78 {
79 	return 0;
80 }
81 
fmemopen(void * restrict buf,size_t size,const char * restrict mode)82 FILE *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