fmemopen: fix eof handling, hopefully right this time

src/stdio/fmemopen.c

@@ -24,8 +24,10 @@ 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;
+	if (len > rem) {
+		len = rem;
+		f->flags |= F_EOF;
+	}
 	memcpy(buf, c->buf+c->pos, len);
 	c->pos += len;
 	rem -= len;
@@ -34,7 +36,6 @@ static size_t mread(FILE *f, unsigned char *buf, size_t len)
 	f->rend = f->buf + rem;
 	memcpy(f->rpos, c->buf+c->pos, rem);
 	c->pos += rem;
-	if (!len) f->flags |= F_EOF;
 	return len;
 }