+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->len - c->pos;
+ if (c->pos > c->len) rem = 0;
+ if (len > rem) {
+ len = rem;
+ f->flags |= F_EOF;
+ }
+ 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;
+ 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->len;
+ 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;
+ if (c->len < c->size) c->buf[c->len] = 0;
+ else if ((f->flags&F_NORD) && c->size) c->buf[c->size-1] = 0;
+ }
+ return len;
+}
+
+static int mclose(FILE *m)