Write straight to hash function instead of buffering.

This commit is contained in:
David Howden 2015-06-30 08:58:55 +10:00
parent 6021704ba3
commit 0b455fc176

68
sum.go
View File

@ -4,8 +4,8 @@ import (
"crypto/sha1"
"encoding/binary"
"fmt"
"hash"
"io"
"io/ioutil"
"os"
)
@ -42,11 +42,12 @@ func Sum(r io.ReadSeeker) (string, error) {
// SumAll returns a checksum of the content from the reader (until EOF).
func SumAll(r io.ReadSeeker) (string, error) {
b, err := ioutil.ReadAll(r)
h := sha1.New()
_, err := io.Copy(h, r)
if err != nil {
return "", nil
}
return sum(b), nil
return hashSum(h), nil
}
// SumAtoms constructs a checksum of MP4 audio file data provided by the io.ReadSeeker which is
@ -80,11 +81,12 @@ func SumAtoms(r io.ReadSeeker) (string, error) {
return SumAtoms(r)
case "mdat": // stop when we get to the data
b, err := readBytes(r, int(size-8))
h := sha1.New()
_, err := io.CopyN(h, r, int64(size-8))
if err != nil {
return "", fmt.Errorf("error reading audio data: %v", err)
}
return sum(b), nil
return hashSum(h), nil
}
_, err = r.Seek(int64(size-8), os.SEEK_CUR)
@ -97,41 +99,69 @@ func SumAtoms(r io.ReadSeeker) (string, error) {
// 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) {
b, err := ioutil.ReadAll(r)
// Need to stop before we hit potential ID3v1 data.
n, err := r.Seek(-128, os.SEEK_END)
if err != nil {
return "", err
return "", fmt.Errorf("error seeking to the end of the file (minus ID3v1 header): %v", err)
}
if len(b) < 128 {
return "", fmt.Errorf("file size must be greater than 128 bytes for ID3v1 metadata (size: %v)", len(b))
// TODO: improve this check???
if n <= 0 {
return "", fmt.Errorf("file size must be greater than 128 bytes (ID3v1 header size) for MP3")
}
return sum(b[:len(b)-128]), nil
// Seek back to the original position now!
_, err = r.Seek(-1*n, os.SEEK_SET)
if err != nil {
return "", fmt.Errorf("error seeking back to the start of the data: %v", err)
}
h := sha1.New()
_, err = io.CopyN(h, r, n)
if err != nil {
return "", fmt.Errorf("error reading %v bytes: %v", n, err)
}
return hashSum(h), nil
}
// SumID3v2 constructs a checksum 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) {
h, err := readID3v2Header(r)
header, err := readID3v2Header(r)
if err != nil {
return "", fmt.Errorf("error reading ID3v2 header: %v", err)
}
_, err = r.Seek(int64(h.Size)+10, os.SEEK_SET)
_, err = r.Seek(int64(header.Size)+10, os.SEEK_SET)
if err != nil {
return "", fmt.Errorf("error seeking to end of ID3V2 header: %v", err)
}
b, err := ioutil.ReadAll(r)
// Need to stop before we hit potential ID3v1 data.
n, err := r.Seek(-128, os.SEEK_END)
if err != nil {
return "", fmt.Errorf("error reading audio data: %v", err)
return "", fmt.Errorf("error seeking to the end of the file (minus ID3v1 header): %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))
// TODO: remove this check?????
if n < 0 {
return "", fmt.Errorf("file size must be greater than 128 bytes for MP3: %v bytes", n)
}
return sum(b[:len(b)-128]), nil
// Seek back to the original position now!
_, err = r.Seek(-1*n, os.SEEK_SET)
if err != nil {
return "", fmt.Errorf("error seeking back to the start of the data: %v", err)
}
h := sha1.New()
_, err = io.CopyN(h, r, n)
if err != nil {
return "", fmt.Errorf("error reading %v bytes: %v", n, err)
}
return hashSum(h), nil
}
func sum(b []byte) string {
return fmt.Sprintf("%x", sha1.Sum(b))
func hashSum(h hash.Hash) string {
return fmt.Sprintf("%x", h.Sum([]byte{}))
}