stream: redo memory streams

Make memory streams actual streams. This causes fewer weird corner cases
and actually allows using demuxers with them.

stream/stream_memory.c

@@ -0,0 +1,84 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libavutil/common.h>
+
+#include "stream.h"
+
+struct priv {
+    bstr data;
+};
+
+static int fill_buffer(stream_t *s, char* buffer, int len)
+{
+    struct priv *p = s->priv;
+    bstr data = p->data;
+    if (s->pos < 0 || s->pos > data.len)
+        return 0;
+    len = FFMIN(len, data.len - s->pos);
+    memcpy(buffer, data.start + s->pos, len);
+    return len;
+}
+
+static int seek(stream_t *s, int64_t newpos)
+{
+    s->pos = newpos;
+    return 1;
+}
+
+static int control(stream_t *s, int cmd, void *arg)
+{
+    struct priv *p = s->priv;
+    switch(cmd) {
+    case STREAM_CTRL_SET_CONTENTS: ;
+        bstr *data = (bstr *)arg;
+        talloc_free(p->data.start);
+        p->data = bstrdup(s, *data);
+        s->end_pos = p->data.len;
+        return 1;
+    }
+    return STREAM_UNSUPPORTED;
+}
+
+static int open_f(stream_t *stream, int mode, void* opts, int* file_format)
+{
+    stream->type = STREAMTYPE_MEMORY;
+
+    stream->fill_buffer = fill_buffer;
+    stream->seek = seek;
+    stream->control = control;
+    stream->read_chunk = 1024 * 1024;
+
+    struct priv *p = talloc_zero(stream, struct priv);
+    stream->priv = p;
+
+    // Initial data
+    bstr data = bstr0(stream->url);
+    bstr_eatstart0(&data, "memory://");
+    stream_control(stream, STREAM_CTRL_SET_CONTENTS, &data);
+
+    return STREAM_OK;
+}
+
+const stream_info_t stream_info_memory = {
+    "Memory",
+    "memory",
+    "",
+    "",
+    open_f,
+    { "memory", NULL },
+};