Merge pull request #608 from TsudaKageyu/mp4-has-tags

Add a method to check if an MP4 file on disk actually has a tag.

taglib/mp4/mp4file.cpp

@@ -34,7 +34,7 @@ using namespace TagLib;
 
 namespace
 {
-  bool checkValid(const MP4::AtomList &list)
+  inline bool checkValid(const MP4::AtomList &list)
   {
     for(MP4::AtomList::ConstIterator it = list.begin(); it != list.end(); ++it) {
 
@@ -55,7 +55,8 @@ public:
   FilePrivate() :
     tag(0),
     atoms(0),
-    properties(0) {}
+    properties(0),
+    hasMP4Tag(false) {}
 
   ~FilePrivate()
   {
@@ -67,6 +68,8 @@ public:
   MP4::Tag        *tag;
   MP4::Atoms      *atoms;
   MP4::Properties *properties;
+
+  bool hasMP4Tag;
 };
 
 MP4::File::File(FileName file, bool readProperties, AudioProperties::ReadStyle) :
@@ -130,12 +133,15 @@ MP4::File::read(bool readProperties)
   }
 
   // must have a moov atom, otherwise consider it invalid
-  MP4::Atom *moov = d->atoms->find("moov");
-  if(!moov) {
+  if(!d->atoms->find("moov")) {
     setValid(false);
     return;
   }
 
+  if(d->atoms->find("moov", "udta", "meta", "ilst")) {
+    d->hasMP4Tag = true;
+  }
+
   d->tag = new Tag(this, d->atoms);
   if(readProperties) {
     d->properties = new Properties(this, d->atoms);
@@ -155,6 +161,16 @@ MP4::File::save()
     return false;
   }
 
-  return d->tag->save();
+  const bool success = d->tag->save();
+  if(success) {
+    d->hasMP4Tag = true;
+  }
+
+  return success;
 }
 
+bool
+MP4::File::hasMP4Tag() const
+{
+  return d->hasMP4Tag;
+}

taglib/mp4/mp4file.h

@@ -117,6 +117,12 @@ namespace TagLib {
        */
       bool save();
 
+      /*!
+       * Returns whether or not the file on disk actually has an MP4 tag, or the
+       * file has a Metadata Item List (ilst) atom.
+       */
+      bool hasMP4Tag() const;
+
     private:
       void read(bool readProperties);
 

tests/test_mp4.cpp

@@ -19,6 +19,7 @@ class TestMP4 : public CppUnit::TestFixture
   CPPUNIT_TEST(testPropertiesALAC);
   CPPUNIT_TEST(testFreeForm);
   CPPUNIT_TEST(testCheckValid);
+  CPPUNIT_TEST(testHasTag);
   CPPUNIT_TEST(testIsEmpty);
   CPPUNIT_TEST(testUpdateStco);
   CPPUNIT_TEST(testSaveExisingWhenIlstIsLast);
@@ -67,8 +68,30 @@ public:
   {
     MP4::File f(TEST_FILE_PATH_C("empty.aiff"));
     CPPUNIT_ASSERT(!f.isValid());
-    MP4::File f2(TEST_FILE_PATH_C("has-tags.m4a"));
-    CPPUNIT_ASSERT(f2.isValid());
+  }
+
+  void testHasTag()
+  {
+    {
+      MP4::File f(TEST_FILE_PATH_C("has-tags.m4a"));
+      CPPUNIT_ASSERT(f.isValid());
+      CPPUNIT_ASSERT(f.hasMP4Tag());
+    }
+
+    ScopedFileCopy copy("no-tags", ".m4a");
+
+    {
+      MP4::File f(copy.fileName().c_str());
+      CPPUNIT_ASSERT(f.isValid());
+      CPPUNIT_ASSERT(!f.hasMP4Tag());
+      f.tag()->setTitle("TITLE");
+      f.save();
+    }
+    {
+      MP4::File f(copy.fileName().c_str());
+      CPPUNIT_ASSERT(f.isValid());
+      CPPUNIT_ASSERT(f.hasMP4Tag());
+    }
   }
 
   void testIsEmpty()