Merge pull request andygrundman#3 from jtbr/mp4_atom_size

Smoothly handle small and ignore empty mpeg-4 atoms.
Remove small bit of redundant code

include/mp4.h

@@ -74,9 +74,9 @@ typedef struct mp4info {
   char *file;
   Buffer *buf;
   uint64_t file_size; // total file size
-  uint64_t size;      // total size
-  uint8_t  hsize;     // header size
-  uint64_t rsize;     // remaining size
+  uint64_t size;      // total size of box; 0 => remainder of file
+  uint8_t  hsize;     // header size in box
+  uint64_t rsize;     // remaining size in box outside header
   uint64_t audio_offset;
   uint64_t audio_size;
   HV *info;

src/mp4.c

@@ -669,7 +669,7 @@ _mp4_read_box(mp4info *mp4)
 
   mp4->rsize = 0; // remaining size in box
 
-  if ( !_check_buf(mp4->infile, mp4->buf, 16, MP4_BLOCK_SIZE) ) {
+  if ( !_check_buf(mp4->infile, mp4->buf, 8, MP4_BLOCK_SIZE) ) {
     return 0;
   }
 
@@ -678,27 +678,38 @@ _mp4_read_box(mp4info *mp4)
   type[4] = '\0';
   buffer_consume(mp4->buf, 4);
 
+  mp4->hsize = 8;
   // Check for 64-bit size
   if (size == 1) {
+    if ( !_check_buf(mp4->infile, mp4->buf, 8, MP4_BLOCK_SIZE) ) {
+      return 0;
+    }
     size = buffer_get_int64(mp4->buf);
     mp4->hsize = 16;
   }
-  else if (size == 0) {
-    // XXX: size extends to end of file
-    mp4->hsize = 8;
+
+  if (size == 0) { 
+    // XXX: box extends to end of file
+    /*nothing to do*/ ; // rsize=size=0
+  } 
+  else if (size < mp4->hsize) {
+    PerlIO_printf(PerlIO_stderr(), "Invalid box size in: %s\n", mp4->file);
+    return 0;
   }
   else {
-    mp4->hsize = 8;
-  }
-
-  if (size) {
+    // set size of the remainder of the box
     mp4->rsize = size - mp4->hsize;
-  }
+  } 
 
   mp4->size = size;
 
   DEBUG_TRACE("%s size %llu\n", type, size);
 
+  if (size == mp4->hsize) {
+    PerlIO_printf(PerlIO_stderr(), "Ignoring empty box of type %s in: %s\n", type, mp4->file);
+    return size;
+  }
+
   if (mp4->seekhdr) {
     // Copy and adjust header if seeking
     char tmp_size[4];
@@ -791,20 +802,17 @@ _mp4_read_box(mp4info *mp4)
     || FOURCC_EQ(type, "dinf")
     || FOURCC_EQ(type, "stbl")
     || FOURCC_EQ(type, "udta")
+    || FOURCC_EQ(type, "trak")
   ) {
     // These boxes are containers for nested boxes, return only the fact that
-    // we read the header size of the container
+    // we read the header size of the container. Read the nested box the next call to this fn.
     size = mp4->hsize;
 
     if ( FOURCC_EQ(type, "trak") ) {
+      // Also a container, but we need to increment track_count too
       mp4->track_count++;
     }
   }
-  else if ( FOURCC_EQ(type, "trak") ) {
-    // Also a container, but we need to increment track_count too
-    size = mp4->hsize;
-    mp4->track_count++;
-  }
   else if ( FOURCC_EQ(type, "mvhd") ) {
     mp4->seen_moov = 1;