Load files to memory when needed for loading GME files.

It happens when the size information is missing.
It closes #5766.
(cherry picked from commit 5e0e7978ffa0ad34c780c08caf518efcc4082127)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/demux/gme.c

@@ -64,15 +64,15 @@ struct demux_sys_t
 
 static int Demux (demux_t *);
 static int Control (demux_t *, int, va_list);
-static gme_err_t Reader (void *, void *, int);
+static gme_err_t ReaderStream (void *, void *, int);
+static gme_err_t ReaderBlock (void *, void *, int);
 
 static int Open (vlc_object_t *obj)
 {
     demux_t *demux = (demux_t *)obj;
 
     int64_t size = stream_Size (demux->s);
-    if (size < 4 /* GME needs to know the file size */
-     || size > LONG_MAX /* too big for GME */)
+    if (size > LONG_MAX /* too big for GME */)
         return VLC_EGENERIC;
 
     /* Auto detection */
@@ -85,6 +85,14 @@ static int Open (vlc_object_t *obj)
         return VLC_EGENERIC;
     msg_Dbg (obj, "detected file type %s", type);
 
+    block_t *data = NULL;
+    if (size <= 0)
+    {
+        data = stream_BlockRemaining (demux->s, 100000000);
+        if (!data )
+            return VLC_EGENERIC;
+    }
+
     /* Initialization */
     demux_sys_t *sys = malloc (sizeof (*sys));
     if (unlikely(sys == NULL))
@@ -96,7 +104,11 @@ static int Open (vlc_object_t *obj)
         free (sys);
         return VLC_ENOMEM;
     }
-    gme_load_custom (sys->emu, Reader, size, demux->s);
+    if (data)
+        gme_load_custom (sys->emu, ReaderBlock, data->i_buffer, data);
+    else
+        gme_load_custom (sys->emu, ReaderStream, size, demux->s);
+    block_Release(data);
     gme_start_track (sys->emu, sys->track_id = 0);
 
     es_format_t fmt;
@@ -158,7 +170,7 @@ static void Close (vlc_object_t *obj)
 }
 
 
-static gme_err_t Reader (void *data, void *buf, int length)
+static gme_err_t ReaderStream (void *data, void *buf, int length)
 {
     stream_t *s = data;
 
@@ -166,7 +178,18 @@ static gme_err_t Reader (void *data, void *buf, int length)
         return "short read";
     return NULL;
 }
+static gme_err_t ReaderBlock (void *data, void *buf, int length)
+{
+    block_t *block = data;
 
+    int max = __MIN (length, (int)block->i_buffer);
+    memcpy (buf, block->p_buffer, max);
+    block->i_buffer -= max;
+    block->p_buffer += max;
+    if (max != length)
+        return "short read";
+    return NULL;
+}
 
 #define SAMPLES (RATE / 10)