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#ifdef __wasilibc_unmodified_upstream // WASI's SEEK_* constants have different values.
 31	base = (size_t [3]){0, c->pos, c->len}[whence];
 32#else
 33	base = (size_t [3]) {
 34            [SEEK_SET] = 0,
 35            [SEEK_CUR] = c->pos,
 36            [SEEK_END] = c->len
 37        }[whence];
 38#endif
 39	if (off < -base || off > (ssize_t)c->size-base) goto fail;
 40	return c->pos = base+off;
 41}
 42
 43static size_t mread(FILE *f, unsigned char *buf, size_t len)
 44{
 45	struct cookie *c = f->cookie;
 46	size_t rem = c->len - c->pos;
 47	if (c->pos > c->len) rem = 0;
 48	if (len > rem) {
 49		len = rem;
 50		f->flags |= F_EOF;
 51	}
 52	memcpy(buf, c->buf+c->pos, len);
 53	c->pos += len;
 54	rem -= len;
 55	if (rem > f->buf_size) rem = f->buf_size;
 56	f->rpos = f->buf;
 57	f->rend = f->buf + rem;
 58	memcpy(f->rpos, c->buf+c->pos, rem);
 59	c->pos += rem;
 60	return len;
 61}
 62
 63static size_t mwrite(FILE *f, const unsigned char *buf, size_t len)
 64{
 65	struct cookie *c = f->cookie;
 66	size_t rem;
 67	size_t len2 = f->wpos - f->wbase;
 68	if (len2) {
 69		f->wpos = f->wbase;
 70		if (mwrite(f, f->wpos, len2) < len2) return 0;
 71	}
 72	if (c->mode == 'a') c->pos = c->len;
 73	rem = c->size - c->pos;
 74	if (len > rem) len = rem;
 75	memcpy(c->buf+c->pos, buf, len);
 76	c->pos += len;
 77	if (c->pos > c->len) {
 78		c->len = c->pos;
 79		if (c->len < c->size) c->buf[c->len] = 0;
 80		else if ((f->flags&F_NORD) && c->size) c->buf[c->size-1] = 0;
 81	}
 82	return len;
 83}
 84
 85static int mclose(FILE *m)
 86{
 87	return 0;
 88}
 89
 90FILE *fmemopen(void *restrict buf, size_t size, const char *restrict mode)
 91{
 92	struct mem_FILE *f;
 93	int plus = !!strchr(mode, '+');
 94	
 95	if (!strchr("rwa", *mode)) {
 96		errno = EINVAL;
 97		return 0;
 98	}
 99
100	if (!buf && size > PTRDIFF_MAX) {
101		errno = ENOMEM;
102		return 0;
103	}
104
105	f = malloc(sizeof *f + (buf?0:size));
106	if (!f) return 0;
107	memset(f, 0, offsetof(struct mem_FILE, buf));
108	f->f.cookie = &f->c;
109	f->f.fd = -1;
110	f->f.lbf = EOF;
111	f->f.buf = f->buf + UNGET;
112	f->f.buf_size = sizeof f->buf - UNGET;
113	if (!buf) {
114		buf = f->buf2;
115		memset(buf, 0, size);
116	}
117
118	f->c.buf = buf;
119	f->c.size = size;
120	f->c.mode = *mode;
121	
122	if (!plus) f->f.flags = (*mode == 'r') ? F_NOWR : F_NORD;
123	if (*mode == 'r') f->c.len = size;
124	else if (*mode == 'a') f->c.len = f->c.pos = strnlen(buf, size);
125	else if (plus) *f->c.buf = 0;
126
127	f->f.read = mread;
128	f->f.write = mwrite;
129	f->f.seek = mseek;
130	f->f.close = mclose;
131
132#if defined(__wasilibc_unmodified_upstream) || defined(_REENTRANT)
133	if (!libc.threaded) f->f.lock = -1;
134#endif
135
136	return __ofl_add(&f->f);
137}