Added SDL_PeekIntoDataQueue().

src/SDL_dataqueue.c

@@ -225,6 +225,31 @@ SDL_WriteToDataQueue(SDL_DataQueue *queue, const void *_data, const size_t _len)
     return 0;
 }
 
+size_t
+SDL_PeekIntoDataQueue(SDL_DataQueue *queue, void *_buf, const size_t _len)
+{
+    size_t len = _len;
+    Uint8 *buf = (Uint8 *) _buf;
+    Uint8 *ptr = buf;
+    SDL_DataQueuePacket *packet;
+
+    if (!queue) {
+        return 0;
+    }
+
+    for (packet = queue->head; len && packet; packet = packet->next) {
+        const size_t avail = packet->datalen - packet->startpos;
+        const size_t cpy = SDL_min(len, avail);
+        SDL_assert(queue->queued_bytes >= avail);
+
+        SDL_memcpy(ptr, packet->data + packet->startpos, cpy);
+        ptr += cpy;
+        len -= cpy;
+    }
+
+    return (size_t) (ptr - buf);
+}
+
 size_t
 SDL_ReadFromDataQueue(SDL_DataQueue *queue, void *_buf, const size_t _len)
 {

src/SDL_dataqueue.h

@@ -31,6 +31,7 @@ void SDL_FreeDataQueue(SDL_DataQueue *queue);
 void SDL_ClearDataQueue(SDL_DataQueue *queue, const size_t slack);
 int SDL_WriteToDataQueue(SDL_DataQueue *queue, const void *data, const size_t len);
 size_t SDL_ReadFromDataQueue(SDL_DataQueue *queue, void *buf, const size_t len);
+size_t SDL_PeekIntoDataQueue(SDL_DataQueue *queue, void *buf, const size_t len);
 size_t SDL_CountDataQueue(SDL_DataQueue *queue);
 
 /* this sets a section of the data queue aside (possibly allocating memory for it)