Proper handling of MP4 atoms with zero length.

If the size of an atom is 0, it designates the last atom which extends to the end of the file.

1 files changed, 8 insertions, 2 deletions

diff --git a/taglib/mp4/mp4atom.cpp b/taglib/mp4/mp4atom.cpp
index 5758173b..20709212 100644
--- a/taglib/mp4/mp4atom.cpp
+++ b/taglib/mp4/mp4atom.cpp
@@ -54,10 +54,15 @@ MP4::Atom::Atom(File *file)
 
   length = header.toUInt();
 
-  if(length == 1) {
+  if(length == 0) {
+    // The last atom which extends to the end of the file.
+    length = file->length() - offset;
+  }
+  else if(length == 1) {
+    // The atom has a 64-bit length.
     const long long longLength = file->readBlock(8).toLongLong();
     if(longLength <= LONG_MAX) {
-      // The atom has a 64-bit length, but it's actually a 31-bit value or long is 64-bit.
+      // The actual length fits in long. That's always the case if long is 64-bit.
       length = static_cast<long>(longLength);
     }
     else {
@@ -67,6 +72,7 @@ MP4::Atom::Atom(File *file)
       return;
     }
   }
+
   if(length < 8) {
     debug("MP4: Invalid atom size");
     length = 0;