Add support for WAV files with appended metadata

id.go

@@ -7,12 +7,12 @@ import (
 
 // Identify identifies the format and file type of the data in the ReadSeeker.
 func Identify(r io.ReadSeeker) (format Format, fileType FileType, err error) {
-	b, err := readBytes(r, 11)
+	b, err := readBytes(r, 12)
 	if err != nil {
 		return
 	}
 
-	_, err = r.Seek(-11, io.SeekCurrent)
+	_, err = r.Seek(-12, io.SeekCurrent)
 	if err != nil {
 		err = fmt.Errorf("could not seek back to original position: %v", err)
 		return
@@ -56,6 +56,16 @@ func Identify(r io.ReadSeeker) (format Format, fileType FileType, err error) {
 			return
 		}
 		return format, MP3, nil
+
+	case string(b[0:4]) == "RIFF" && string(b[8:12]) == "WAVE":
+		format = UnknownFormat
+		err = setWavOffset(r)
+		if err != nil {
+			return format, WAV, err
+		}
+		// call Identify() again, replacing whatever fileType it finds with WAV
+		format, _, err = Identify(r)
+		return format, WAV, err
 	}
 
 	n, err := r.Seek(-128, io.SeekEnd)

tag.go

@@ -6,12 +6,13 @@
 // parsing and artwork extraction.
 //
 // Detect and parse tag metadata from an io.ReadSeeker (i.e. an *os.File):
-// 	m, err := tag.ReadFrom(f)
-// 	if err != nil {
-// 		log.Fatal(err)
-// 	}
-// 	log.Print(m.Format()) // The detected format.
-// 	log.Print(m.Title())  // The title of the track (see Metadata interface for more details).
+//
+//	m, err := tag.ReadFrom(f)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	log.Print(m.Format()) // The detected format.
+//	log.Print(m.Title())  // The title of the track (see Metadata interface for more details).
 package tag
 
 import (
@@ -53,6 +54,14 @@ func ReadFrom(r io.ReadSeeker) (Metadata, error) {
 
 	case string(b[0:4]) == "DSD ":
 		return ReadDSFTags(r)
+
+	case string(b[0:4]) == "RIFF":
+		err := setWavOffset(r)
+		if err != nil {
+			return nil, err
+		}
+		// call ReadFrom() again at the new offset
+		return ReadFrom(r)
 	}
 
 	m, err := ReadID3v1Tags(r)
@@ -95,6 +104,7 @@ const (
 	FLAC            FileType = "FLAC" // FLAC file
 	OGG             FileType = "OGG"  // OGG file
 	DSF             FileType = "DSF"  // DSF file DSD Sony format see https://dsd-guide.com/sites/default/files/white-papers/DSFFileFormatSpec_E.pdf
+	WAV             FileType = "WAV"  // WAVE file
 )
 
 // Metadata is an interface which is used to describe metadata retrieved by this package.

wav.go

@@ -0,0 +1,62 @@
+package tag
+
+import (
+	"fmt"
+	"io"
+)
+
+func setWavOffset(r io.ReadSeeker) error {
+	// verify RIFF chunk
+	str, err := readString(r, 4)
+	if err != nil {
+		return err
+	}
+	if str != "RIFF" {
+		return fmt.Errorf("chunk header %v does not match expected 'RIFF'", str)
+	}
+
+	// verify WAVE filetype
+	_, err = r.Seek(4, io.SeekCurrent)
+	if err != nil {
+		return err
+	}
+	str, err = readString(r, 4)
+	if err != nil {
+		return err
+	}
+	if str != "WAVE" {
+		return fmt.Errorf("filetype %v does not match exptected 'WAVE'", str)
+	}
+
+	// identify chunk length
+	_, err = r.Seek(24, io.SeekCurrent) // 24-byte data format chunk is unneeded
+	if err != nil {
+		return err
+	}
+	str, err = readString(r, 4)
+	if err != nil {
+		return err
+	}
+	if str != "data" {
+		return fmt.Errorf("identifier %v does not match expected 'data'", err)
+	}
+	dataSize, err := readUint32LittleEndian(r)
+	if err != nil {
+		return err
+	}
+
+	_, err = r.Seek(int64(dataSize), io.SeekCurrent)
+	if err != nil {
+		return err
+	}
+
+	// skip unneeded 8-byte RIFF chunk header (4-byte ASCII identifier
+	// and 4-byte little-endian uint32 chunk size), more info:
+	// https://en.wikipedia.org/wiki/Resource_Interchange_File_Format#Explanation
+	_, err = r.Seek(8, io.SeekCurrent)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}