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#include "stdio_impl.h"
struct cookie {
size_t pos, len, size;
unsigned char *buf;
int mode;
};
static off_t mseek(FILE *f, off_t off, int whence)
{
ssize_t base;
struct cookie *c = f->cookie;
if (whence>2U) {
fail:
errno = EINVAL;
return -1;
}
base = (size_t [3]){0, c->pos, c->len}[whence];
if (off < -base || off > (ssize_t)c->size-base) goto fail;
return c->pos = base+off;
}
static size_t mread(FILE *f, unsigned char *buf, size_t len)
{
struct cookie *c = f->cookie;
size_t rem = c->size - c->pos;
if (!len) return 0;
if (len > rem) len = rem;
memcpy(buf, c->buf+c->pos, len);
c->pos += len;
rem -= len;
if (rem > f->buf_size) rem = f->buf_size;
f->rpos = f->buf;
f->rend = f->buf + rem;
memcpy(f->rpos, c->buf+c->pos, rem);
c->pos += rem;
if (!len) f->flags |= F_EOF;
return len;
}
static size_t mwrite(FILE *f, const unsigned char *buf, size_t len)
{
struct cookie *c = f->cookie;
size_t rem;
size_t len2 = f->wpos - f->wbase;
if (len2) {
f->wpos = f->wbase;
if (mwrite(f, f->wpos, len2) < len2) return 0;
}
if (c->mode == 'a') c->pos = c->size;
rem = c->size - c->pos;
if (len > rem) len = rem;
memcpy(c->buf+c->pos, buf, len);
c->pos += len;
if (c->pos >= c->len) c->len = c->pos;
c->buf[c->len==c->size ? c->len-1 : c->len] = 0;
return len;
}
static int mclose(FILE *m)
{
return 0;
}
FILE *fmemopen(void *buf, size_t size, const char *mode)
{
FILE *f;
struct cookie *c;
int plus = !!strchr(mode, '+');
if (!size || !strchr("rwa", *mode)) {
errno = EINVAL;
return 0;
}
if (!buf && size > SIZE_MAX-sizeof(FILE)-BUFSIZ-UNGET) {
errno = ENOMEM;
return 0;
}
f = calloc(sizeof *f + sizeof *c + UNGET + BUFSIZ + (buf?0:size), 1);
if (!f) return 0;
f->cookie = c = (void *)(f+1);
f->fd = -1;
f->lbf = EOF;
f->buf = (unsigned char *)(c+1) + UNGET;
f->buf_size = BUFSIZ;
if (!buf) buf = f->buf + BUFSIZ;
c->buf = buf;
c->size = size;
c->mode = *mode;
if (!plus) f->flags = (*mode == 'r') ? F_NOWR : F_NORD;
if (*mode == 'r') c->len = size;
else if (*mode == 'a') c->len = c->pos = strnlen(buf, size);
f->read = mread;
f->write = mwrite;
f->seek = mseek;
f->close = mclose;
if (!libc.threaded) {
f->lock = -1;
f->next = libc.ofl_head;
if (libc.ofl_head) libc.ofl_head->prev = f;
libc.ofl_head = f;
}
return f;
}
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