Refactored Hash -> Sum and fixed infinite loop issue with SumAtoms

2015-04-03 15:13:39 +11:00
parent 208a9e993c
commit e9deeea0e1
2 changed files with 28 additions and 24 deletions
@@ -0,0 +1,162 @@
+package tag
+
+import (
+	"crypto/sha1"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+)
+
+// Sum creates a checksum of the audio file data provided by the io.ReadSeeker which is metadata
+// (ID3, MP4) invariant.
+func Sum(r io.ReadSeeker) (string, error) {
+	b, err := readBytes(r, 11)
+	if err != nil {
+		return "", err
+	}
+
+	if string(b[4:11]) == "ftypM4A" {
+		return SumAtoms(r)
+	}
+
+	if string(b[0:3]) == "ID3" {
+		return SumID3v2(r)
+	}
+
+	h, err := SumID3v1(r)
+	if err != nil {
+		if err == ErrNotID3v1 {
+			return SumAll(r)
+		}
+		return "", err
+	}
+	return h, nil
+}
+
+// SumAll returns a checksum of the entire content.
+func SumAll(r io.ReadSeeker) (string, error) {
+	_, err := r.Seek(0, os.SEEK_SET)
+	if err != nil {
+		return "", fmt.Errorf("error seeking to 0: %v", err)
+	}
+
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return "", nil
+	}
+	return sum(b), nil
+}
+
+// SumAtoms constructs a checksum of MP4 audio file data provided by the io.ReadSeeker which is
+// metadata invariant.
+func SumAtoms(r io.ReadSeeker) (string, error) {
+	_, err := r.Seek(0, os.SEEK_SET)
+	if err != nil {
+		return "", fmt.Errorf("error seeking to 0: %v", err)
+	}
+	return sumAtoms(r)
+}
+
+func sumAtoms(r io.ReadSeeker) (string, error) {
+	for {
+		var size uint32
+		err := binary.Read(r, binary.BigEndian, &size)
+		if err != nil {
+			if err == io.EOF {
+				return "", fmt.Errorf("reached EOF before audio data")
+			}
+			return "", err
+		}
+
+		name, err := readString(r, 4)
+		if err != nil {
+			return "", err
+		}
+
+		switch name {
+		case "meta":
+			// next_item_id (int32)
+			_, err := readBytes(r, 4)
+			if err != nil {
+				return "", err
+			}
+			fallthrough
+
+		case "moov", "udta", "ilst":
+			return sumAtoms(r)
+
+		case "free":
+			_, err = r.Seek(int64(size-8), os.SEEK_CUR)
+			if err != nil {
+				return "", fmt.Errorf("error reading 'free' space: %v", err)
+			}
+			continue
+
+		case "mdat": // stop when we get to the data
+			b, err := readBytes(r, int(size-8))
+			if err != nil {
+				return "", fmt.Errorf("error reading audio data: %v", err)
+			}
+			return sum(b), nil
+		}
+
+		_, err = r.Seek(int64(size-8), os.SEEK_CUR)
+		if err != nil {
+			return "", fmt.Errorf("error reading '%v' tag: %v", name, err)
+		}
+	}
+}
+
+// SumID3v1 constructs a checksum of MP3 audio file data (assumed to have ID3v1 tags) provided
+// by the io.ReadSeeker which is metadata invariant.
+func SumID3v1(r io.ReadSeeker) (string, error) {
+	_, err := r.Seek(0, os.SEEK_SET)
+	if err != nil {
+		return "", fmt.Errorf("error seeking to 0: %v", err)
+	}
+
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return "", err
+	}
+
+	if len(b) < 128 {
+		return "", fmt.Errorf("file size must be greater than 128 bytes for ID3v1 metadata (size: %v)", len(b))
+	}
+	return sum(b[:len(b)-128]), nil
+}
+
+// SumID3v2 constructs a hash of MP3 audio file data (assumed to have ID3v2 tags) provided by the
+// io.ReadSeeker which is metadata invariant.
+func SumID3v2(r io.ReadSeeker) (string, error) {
+	_, err := r.Seek(0, os.SEEK_SET)
+	if err != nil {
+		return "", fmt.Errorf("error seeking to 0: %v", err)
+	}
+
+	h, err := readID3v2Header(r)
+	if err != nil {
+		return "", fmt.Errorf("error reading ID3v2 header: %v", err)
+	}
+
+	_, err = r.Seek(int64(h.Size), os.SEEK_SET)
+	if err != nil {
+		return "", fmt.Errorf("error seeking to end of ID3V2 header: %v", err)
+	}
+
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return "", fmt.Errorf("error reading audio data: %v", err)
+	}
+
+	if len(b) < 128 {
+		return "", fmt.Errorf("file size must be greater than 128 bytes for MP3 (ID3v2 header size: %d, remaining: %d)", h.Size, len(b))
+	}
+	return sum(b[:len(b)-128]), nil
+}
+
+func sum(b []byte) string {
+	return fmt.Sprintf("%x", sha1.Sum(b))
+}