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.write = mwrite;
121	f->f.seek = mseek;
122	f->f.close = mclose;
123
124	if (!libc.threaded) f->f.lock = -1;
125
126	return __ofl_add(&f->f);
127}