Merge branch 'allmp4' of https://github.com/xhenner/tag into xhenner-allmp4

mp4.go

@@ -6,6 +6,7 @@ package tag
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -69,9 +70,62 @@ func ReadAtoms(r io.ReadSeeker) (Metadata, error) {
 	return m, err
 }
 
+func readCustomAtom(r io.ReadSeeker, size uint32) (string, uint32, error) {
+	var datasize uint32
+	var datapos int64
+	var name string
+	var mean string
+
+	for size > 8 {
+		var subsize uint32
+		err := binary.Read(r, binary.BigEndian, &subsize)
+		if err != nil {
+			return "----", size - 4, err
+		}
+		subname, err := readString(r, 4)
+		if err != nil {
+			return "----", size - 8, err
+		}
+		b, err := readBytes(r, int(subsize-8))
+		if err != nil {
+			return "----", size - subsize, err
+		}
+		// Remove the size of the atom from the size counter
+		size -= subsize
+
+		switch string(subname) {
+		case "mean":
+			mean = string(b[4:])
+		case "name":
+			name = string(b[4:])
+		case "data":
+			datapos, err = r.Seek(0, os.SEEK_CUR)
+			if err != nil {
+				return "----", size, err
+			}
+			datasize = subsize
+			datapos -= int64(subsize)
+		}
+	}
+	// there should remain only the header size
+	if size != 8 {
+		return "----", size, errors.New("---- atom out of bound")
+	}
+	if mean == "com.apple.iTunes" && datasize != 0 && name != "" {
+		// we jump just before the data subatom
+		_, err := r.Seek(datapos, os.SEEK_SET)
+		if err != nil {
+			return "----", size, err
+		}
+		return name, datasize + 8, nil
+	}
+	return "----", size, nil
+}
+
 func (m metadataMP4) readAtoms(r io.ReadSeeker) error {
 	for {
 		var size uint32
+		ok := false
 		err := binary.Read(r, binary.BigEndian, &size)
 		if err != nil {
 			if err == io.EOF {
@@ -101,8 +155,25 @@ func (m metadataMP4) readAtoms(r io.ReadSeeker) error {
 				return err
 			}
 			continue
-		case "mdat": // stop when we get to the data
-			return nil
+		case "mdat": // skip the data, the metadata can be at the end
+			_, err := r.Seek(int64(size-8), os.SEEK_CUR)
+			if err != nil {
+				return err
+			}
+			continue
+		case "----":
+			// Generic atom.
+			// Should have 3 sub atoms : mean, name and data.
+			// We check that mean=="com.apple.iTunes" and we use the subname as
+			// the name, and move to the data atom.
+			// If anything goes wrong, we jump at the end of the "----" atom.
+			name, size, err = readCustomAtom(r, size)
+			if err != nil {
+				return err
+			}
+			ok = (name != "----")
+		default:
+			_, ok = atoms[name]
 		}
 
 		b, err := readBytes(r, int(size-8))
@@ -110,7 +181,7 @@ func (m metadataMP4) readAtoms(r io.ReadSeeker) error {
 			return err
 		}
 
-		_, ok := atoms[name]
+		// At this point, we allow all known atoms and the valid "----" atoms
 		if !ok {
 			continue
 		}