Update

Dockerfile

@@ -0,0 +1,36 @@
+# Fase 1: Build
+FROM golang:1.21-alpine AS builder
+
+WORKDIR /app
+
+# Copia i file necessari per la compilazione
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+# Compila l'applicazione
+RUN CGO_ENABLED=0 GOOS=linux go build -o u-pod
+
+# Fase 2: Container leggero
+FROM alpine:latest
+
+WORKDIR /app
+
+# Copia solo l'eseguibile dalla fase di build
+COPY --from=builder /app/u-pod .
+COPY --from=builder /app/cover.jpg .
+RUN mkdir -p audio covers
+
+# Variabili d'ambiente obbligatorie (da sovrascrivere al runtime)
+ENV PODCAST_PORT=":8080" \
+    PODCAST_BASE_URL="http://localhost:8080" \
+    PODCAST_AUDIO_DIR="/app/audio" \
+    PODCAST_COVERS_DIR="/app/covers" \
+    PODCAST_TITLE="Yo mom Podcast"
+
+# Esponi la porta e avvia l'applicazione
+EXPOSE 8080
+VOLUME ["/app/audio", "/app/covers"]
+CMD ["./u-pod"]
+

README.md

@@ -1,16 +1,26 @@
+# U-Pod
+
+## Overview
+
 This is U-Pod, the torpedo-style podcast system with minimal footprint and maximum utility.
 
 No databases needed to function, no cloud required, no datacenter necessary - just the filesystem and your content. Even your mom on her knees could help set it up, though that's not a functional requirement.
 
+## Setup
+
 First, you need to build the image. I've included a handy Dockerfile in the folder. Use it.
 
 Once you've created your image, use Docker to run it after setting these environment variables:
 
+<pre>
    PODCAST_PORT=:8080
    PODCAST_BASE_URL=http://your-domain.com
    PODCAST_AUDIO_DIR=/app/data/audio
    PODCAST_COVERS_DIR=/app/data/covers
    PODCAST_TITLE="My Podcast - and your mom"
+</pre>
+
+## File Linking
 
 What links files in /audio to files in /covers?
 
@@ -28,7 +38,7 @@ U-Pod will then create the torpedo, with the image properly linked to the audio.
 
 Once you have the Docker image, simply create the /data folder and put your files in it.
 
-FAQ:
+## FAQ
 
 - My "SisterGermanaGangbang 3.0" software can't use it.
   - It uses the standard podcast format http://www.itunes.com/dtds/podcast-1.0.dtd. If your shitty software can't read it, take it up with Sister Germana.
@@ -42,5 +52,5 @@ FAQ:
 - I need you to change this, this and that.
   - No, No, and No
 
-
+- How can I get support for this software?
-
+- You cannot. Code is simple, and you are alone in the night, like any operation engineer during the night. Man up!!!!

go.mod

@@ -0,0 +1,5 @@
+module u-pod
+
+go 1.21.0
+
+require github.com/dhowden/tag v0.0.0-20240417053706-3d75831295e8

go.sum

@@ -0,0 +1,2 @@
+github.com/dhowden/tag v0.0.0-20240417053706-3d75831295e8 h1:OtSeLS5y0Uy01jaKK4mA/WVIYtpzVm63vLVAPzJXigg=
+github.com/dhowden/tag v0.0.0-20240417053706-3d75831295e8/go.mod h1:apkPC/CR3s48O2D7Y++n1XWEpgPNNCjXYga3PPbJe2E=

main.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+var (
+	port      = os.Getenv("PODCAST_PORT")       // Es: ":8080"
+	baseURL   = os.Getenv("PODCAST_BASE_URL")   // Es: "http://mioserver.com"
+	audioDir  = os.Getenv("PODCAST_AUDIO_DIR")  // Es: "/data/podcast/audio"
+	coversDir = os.Getenv("PODCAST_COVERS_DIR") // Es: "/data/podcast/covers"
+	podTitle  = os.Getenv("PODCAST_TITLE")      // Es: "Il Mio Podcast"
+)
+
+func init() {
+	// Verifica variabili d'ambiente
+	for _, v := range []struct {
+		name  string
+		value string
+	}{
+		{"PODCAST_PORT", port},
+		{"PODCAST_BASE_URL", baseURL},
+		{"PODCAST_AUDIO_DIR", audioDir},
+		{"PODCAST_COVERS_DIR", coversDir},
+		{"PODCAST_TITLE", podTitle},
+	} {
+		if v.value == "" {
+			log.Fatalf("Variabile d'ambiente mancante: %s", v.name)
+		}
+	}
+}
+
+func main() {
+	// Handler principale
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		// Verifica se la richiesta è per un file audio o cover
+		requestedFile := filepath.Clean(r.URL.Path)
+		isAudio := strings.HasPrefix(requestedFile, "/audio/")
+		isCover := strings.HasPrefix(requestedFile, "/covers/")
+
+		if isAudio || isCover {
+			// Servi il file richiesto
+			http.ServeFile(w, r, filepath.Join(".", requestedFile))
+			return
+		}
+
+		// Altrimenti servi sempre l'RSS
+		if err := generateRSS(); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		http.ServeFile(w, r, "feed.xml")
+	})
+
+	// Aggiornamento periodico
+	go func() {
+		for {
+			time.Sleep(5 * time.Minute)
+			if err := generateRSS(); err != nil {
+				log.Printf("Aggiornamento RSS fallito: %v", err)
+			}
+		}
+	}()
+
+	log.Printf("Server in ascolto su %s%s", baseURL, port)
+	log.Fatal(http.ListenAndServe(port, nil))
+}

pod.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/dhowden/tag"
+)
+
+type Episode struct {
+	Title   string
+	File    string
+	Cover   string
+	PubDate string
+	Size    int64
+}
+
+var (
+	lastMod time.Time
+	rssLock sync.Mutex
+)
+
+func generateRSS() error {
+	rssLock.Lock()
+	defer rssLock.Unlock()
+
+	episodes, err := scanEpisodes()
+	if err != nil {
+		return err
+	}
+
+	rss := fmt.Sprintf(`<?xml version="1.0"?>
+<rss version="2.0" xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd">
+<channel>
+	<title>%s</title>
+	<link>%s</link>`, podTitle, baseURL)
+
+	for _, ep := range episodes {
+		rss += fmt.Sprintf(`
+	<item>
+		<title>%s</title>
+		<enclosure url="%s/%s" type="audio/mpeg" length="%d"/>
+		<pubDate>%s</pubDate>`,
+			ep.Title, baseURL, ep.File, ep.Size, ep.PubDate)
+
+		if ep.Cover != "" {
+			rss += fmt.Sprintf(`
+		<itunes:image href="%s/%s"/>`, baseURL, ep.Cover)
+		}
+
+		rss += "\n	</item>"
+	}
+
+	rss += "\n</channel>\n</rss>"
+
+	return os.WriteFile("feed.xml", []byte(rss), 0644)
+}
+
+func scanEpisodes() ([]Episode, error) {
+	var episodes []Episode
+
+	err := filepath.Walk(audioDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil || info.IsDir() || !strings.HasSuffix(strings.ToLower(path), ".mp3") {
+			return nil
+		}
+
+		file, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		defer file.Close()
+
+		meta, err := tag.ReadFrom(file)
+		if err != nil {
+			log.Printf("File %s senza metadati ID3: %v", path, err)
+			return nil
+		}
+
+		relPath, _ := filepath.Rel(".", path)
+		baseName := strings.TrimSuffix(filepath.Base(path), filepath.Ext(path))
+		coverPath := filepath.Join(coversDir, baseName+".jpg")
+
+		ep := Episode{
+			Title:   meta.Title(),
+			File:    relPath,
+			PubDate: info.ModTime().Format(time.RFC1123),
+			Size:    info.Size(),
+		}
+
+		if _, err := os.Stat(coverPath); err == nil {
+			ep.Cover, _ = filepath.Rel(".", coverPath)
+		}
+
+		episodes = append(episodes, ep)
+		return nil
+	})
+
+	return episodes, err
+}

vendor/github.com/dhowden/tag/.editorconfig

@@ -0,0 +1,19 @@
+# EditorConfig helps developers define and maintain consistent
+# coding styles between different editors and IDEs
+# editorconfig.org
+
+root = true
+
+[*.go]
+indent_style = tab
+indent_size = 3
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*]
+# We recommend you to keep these unchanged
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true

vendor/github.com/dhowden/tag/.travis.yml

@@ -0,0 +1,5 @@
+language: go
+
+go:
+  - 1.7
+  - tip

vendor/github.com/dhowden/tag/LICENSE

@@ -0,0 +1,23 @@
+Copyright 2015, David Howden
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+  Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+  Redistributions in binary form must reproduce the above copyright notice, this
+  list of conditions and the following disclaimer in the documentation and/or
+  other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/github.com/dhowden/tag/README.md

@@ -0,0 +1,71 @@
+# MP3/MP4/OGG/FLAC metadata parsing library
+[![GoDoc](https://pkg.go.dev/badge/github.com/dhowden/tag)](https://pkg.go.dev/github.com/dhowden/tag)
+
+This package provides MP3 (ID3v1,2.{2,3,4}) and MP4 (ACC, M4A, ALAC), OGG and FLAC metadata detection, parsing and artwork extraction.
+
+Detect and parse tag metadata from an `io.ReadSeeker` (i.e. an `*os.File`):
+
+```go
+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).
+```
+
+Parsed metadata is exported via a single interface (giving a consistent API for all supported metadata formats).
+
+```go
+// Metadata is an interface which is used to describe metadata retrieved by this package.
+type Metadata interface {
+	Format() Format
+	FileType() FileType
+
+	Title() string
+	Album() string
+	Artist() string
+	AlbumArtist() string
+	Composer() string
+	Genre() string
+	Year() int
+
+	Track() (int, int) // Number, Total
+	Disc() (int, int) // Number, Total
+
+	Picture() *Picture // Artwork
+	Lyrics() string
+	Comment() string
+
+	Raw() map[string]interface{} // NB: raw tag names are not consistent across formats.
+}
+```
+
+## Audio Data Checksum (SHA1)
+
+This package also provides a metadata-invariant checksum for audio files: only the audio data is used to
+construct the checksum.
+
+[https://pkg.go.dev/github.com/dhowden/tag#Sum](https://pkg.go.dev/github.com/dhowden/tag#Sum)
+
+## Tools
+
+There are simple command-line tools which demonstrate basic tag extraction and summing:
+
+```console
+$ go install github.com/dhowden/tag/cmd/tag@latest
+$ cd $GOPATH/bin
+$ ./tag 11\ High\ Hopes.m4a
+Metadata Format: MP4
+Title: High Hopes
+Album: The Division Bell
+Artist: Pink Floyd
+Composer: Abbey Road Recording Studios/David Gilmour/Polly Samson
+Year: 1994
+Track: 11 of 11
+Disc: 1 of 1
+Picture: Picture{Ext: jpeg, MIMEType: image/jpeg, Type: , Description: , Data.Size: 606109}
+
+$ ./sum 11\ High\ Hopes.m4a
+2ae208c5f00a1f21f5fac9b7f6e0b8e52c06da29
+```

vendor/github.com/dhowden/tag/dsf.go

@@ -0,0 +1,109 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"errors"
+	"io"
+)
+
+// ReadDSFTags reads DSF metadata from the io.ReadSeeker, returning the resulting
+// metadata in a Metadata implementation, or non-nil error if there was a problem.
+// samples: http://www.2l.no/hires/index.html
+func ReadDSFTags(r io.ReadSeeker) (Metadata, error) {
+	dsd, err := readString(r, 4)
+	if err != nil {
+		return nil, err
+	}
+	if dsd != "DSD " {
+		return nil, errors.New("expected 'DSD '")
+	}
+
+	_, err = r.Seek(int64(16), io.SeekCurrent)
+	if err != nil {
+		return nil, err
+	}
+
+	id3Pointer, err := readUint64LittleEndian(r)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = r.Seek(int64(id3Pointer), io.SeekStart)
+	if err != nil {
+		return nil, err
+	}
+
+	id3, err := ReadID3v2Tags(r)
+	if err != nil {
+		return nil, err
+	}
+
+	return metadataDSF{id3}, nil
+}
+
+type metadataDSF struct {
+	id3 Metadata
+}
+
+func (m metadataDSF) Format() Format {
+	return m.id3.Format()
+}
+
+func (m metadataDSF) FileType() FileType {
+	return DSF
+}
+
+func (m metadataDSF) Title() string {
+	return m.id3.Title()
+}
+
+func (m metadataDSF) Album() string {
+	return m.id3.Album()
+}
+
+func (m metadataDSF) Artist() string {
+	return m.id3.Artist()
+}
+
+func (m metadataDSF) AlbumArtist() string {
+	return m.id3.AlbumArtist()
+}
+
+func (m metadataDSF) Composer() string {
+	return m.id3.Composer()
+}
+
+func (m metadataDSF) Year() int {
+	return m.id3.Year()
+}
+
+func (m metadataDSF) Genre() string {
+	return m.id3.Genre()
+}
+
+func (m metadataDSF) Track() (int, int) {
+	return m.id3.Track()
+}
+
+func (m metadataDSF) Disc() (int, int) {
+	return m.id3.Disc()
+}
+
+func (m metadataDSF) Picture() *Picture {
+	return m.id3.Picture()
+}
+
+func (m metadataDSF) Lyrics() string {
+	return m.id3.Lyrics()
+}
+
+func (m metadataDSF) Comment() string {
+	return m.id3.Comment()
+}
+
+func (m metadataDSF) Raw() map[string]interface{} {
+	return m.id3.Raw()
+}

vendor/github.com/dhowden/tag/flac.go

@@ -0,0 +1,89 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"errors"
+	"io"
+)
+
+// blockType is a type which represents an enumeration of valid FLAC blocks
+type blockType byte
+
+// FLAC block types.
+const (
+	// Stream Info Block           0
+	// Padding Block               1
+	// Application Block           2
+	// Seektable Block             3
+	// Cue Sheet Block             5
+	vorbisCommentBlock blockType = 4
+	pictureBlock       blockType = 6
+)
+
+// ReadFLACTags reads FLAC metadata from the io.ReadSeeker, returning the resulting
+// metadata in a Metadata implementation, or non-nil error if there was a problem.
+func ReadFLACTags(r io.ReadSeeker) (Metadata, error) {
+	flac, err := readString(r, 4)
+	if err != nil {
+		return nil, err
+	}
+	if flac != "fLaC" {
+		return nil, errors.New("expected 'fLaC'")
+	}
+
+	m := &metadataFLAC{
+		newMetadataVorbis(),
+	}
+
+	for {
+		last, err := m.readFLACMetadataBlock(r)
+		if err != nil {
+			return nil, err
+		}
+
+		if last {
+			break
+		}
+	}
+	return m, nil
+}
+
+type metadataFLAC struct {
+	*metadataVorbis
+}
+
+func (m *metadataFLAC) readFLACMetadataBlock(r io.ReadSeeker) (last bool, err error) {
+	blockHeader, err := readBytes(r, 1)
+	if err != nil {
+		return
+	}
+
+	if getBit(blockHeader[0], 7) {
+		blockHeader[0] ^= (1 << 7)
+		last = true
+	}
+
+	blockLen, err := readInt(r, 3)
+	if err != nil {
+		return
+	}
+
+	switch blockType(blockHeader[0]) {
+	case vorbisCommentBlock:
+		err = m.readVorbisComment(r)
+
+	case pictureBlock:
+		err = m.readPictureBlock(r)
+
+	default:
+		_, err = r.Seek(int64(blockLen), io.SeekCurrent)
+	}
+	return
+}
+
+func (m *metadataFLAC) FileType() FileType {
+	return FLAC
+}

vendor/github.com/dhowden/tag/id.go

@@ -0,0 +1,81 @@
+package tag
+
+import (
+	"fmt"
+	"io"
+)
+
+// 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)
+	if err != nil {
+		return
+	}
+
+	_, err = r.Seek(-11, io.SeekCurrent)
+	if err != nil {
+		err = fmt.Errorf("could not seek back to original position: %v", err)
+		return
+	}
+
+	switch {
+	case string(b[0:4]) == "fLaC":
+		return VORBIS, FLAC, nil
+
+	case string(b[0:4]) == "OggS":
+		return VORBIS, OGG, nil
+
+	case string(b[4:8]) == "ftyp":
+		b = b[8:11]
+		fileType = UnknownFileType
+		switch string(b) {
+		case "M4A":
+			fileType = M4A
+
+		case "M4B":
+			fileType = M4B
+
+		case "M4P":
+			fileType = M4P
+		}
+		return MP4, fileType, nil
+
+	case string(b[0:3]) == "ID3":
+		b := b[3:]
+		switch uint(b[0]) {
+		case 2:
+			format = ID3v2_2
+		case 3:
+			format = ID3v2_3
+		case 4:
+			format = ID3v2_4
+		case 0, 1:
+			fallthrough
+		default:
+			err = fmt.Errorf("ID3 version: %v, expected: 2, 3 or 4", uint(b[0]))
+			return
+		}
+		return format, MP3, nil
+	}
+
+	n, err := r.Seek(-128, io.SeekEnd)
+	if err != nil {
+		return
+	}
+
+	tag, err := readString(r, 3)
+	if err != nil {
+		return
+	}
+
+	_, err = r.Seek(-n, io.SeekCurrent)
+	if err != nil {
+		return
+	}
+
+	if tag != "TAG" {
+		err = ErrNoTagsFound
+		return
+	}
+	return ID3v1, MP3, nil
+}

vendor/github.com/dhowden/tag/id3v1.go

@@ -0,0 +1,144 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"errors"
+	"io"
+	"strconv"
+	"strings"
+)
+
+// id3v1Genres is a list of genres as given in the ID3v1 specification.
+var id3v1Genres = [...]string{
+	"Blues", "Classic Rock", "Country", "Dance", "Disco", "Funk", "Grunge",
+	"Hip-Hop", "Jazz", "Metal", "New Age", "Oldies", "Other", "Pop", "R&B",
+	"Rap", "Reggae", "Rock", "Techno", "Industrial", "Alternative", "Ska",
+	"Death Metal", "Pranks", "Soundtrack", "Euro-Techno", "Ambient",
+	"Trip-Hop", "Vocal", "Jazz+Funk", "Fusion", "Trance", "Classical",
+	"Instrumental", "Acid", "House", "Game", "Sound Clip", "Gospel",
+	"Noise", "AlternRock", "Bass", "Soul", "Punk", "Space", "Meditative",
+	"Instrumental Pop", "Instrumental Rock", "Ethnic", "Gothic",
+	"Darkwave", "Techno-Industrial", "Electronic", "Pop-Folk",
+	"Eurodance", "Dream", "Southern Rock", "Comedy", "Cult", "Gangsta",
+	"Top 40", "Christian Rap", "Pop/Funk", "Jungle", "Native American",
+	"Cabaret", "New Wave", "Psychadelic", "Rave", "Showtunes", "Trailer",
+	"Lo-Fi", "Tribal", "Acid Punk", "Acid Jazz", "Polka", "Retro",
+	"Musical", "Rock & Roll", "Hard Rock", "Folk", "Folk-Rock",
+	"National Folk", "Swing", "Fast Fusion", "Bebob", "Latin", "Revival",
+	"Celtic", "Bluegrass", "Avantgarde", "Gothic Rock", "Progressive Rock",
+	"Psychedelic Rock", "Symphonic Rock", "Slow Rock", "Big Band",
+	"Chorus", "Easy Listening", "Acoustic", "Humour", "Speech", "Chanson",
+	"Opera", "Chamber Music", "Sonata", "Symphony", "Booty Bass", "Primus",
+	"Porn Groove", "Satire", "Slow Jam", "Club", "Tango", "Samba",
+	"Folklore", "Ballad", "Power Ballad", "Rhythmic Soul", "Freestyle",
+	"Duet", "Punk Rock", "Drum Solo", "Acapella", "Euro-House", "Dance Hall",
+}
+
+// ErrNotID3v1 is an error which is returned when no ID3v1 header is found.
+var ErrNotID3v1 = errors.New("invalid ID3v1 header")
+
+// ReadID3v1Tags reads ID3v1 tags from the io.ReadSeeker.  Returns ErrNotID3v1
+// if there are no ID3v1 tags, otherwise non-nil error if there was a problem.
+func ReadID3v1Tags(r io.ReadSeeker) (Metadata, error) {
+	_, err := r.Seek(-128, io.SeekEnd)
+	if err != nil {
+		return nil, err
+	}
+
+	if tag, err := readString(r, 3); err != nil {
+		return nil, err
+	} else if tag != "TAG" {
+		return nil, ErrNotID3v1
+	}
+
+	title, err := readString(r, 30)
+	if err != nil {
+		return nil, err
+	}
+
+	artist, err := readString(r, 30)
+	if err != nil {
+		return nil, err
+	}
+
+	album, err := readString(r, 30)
+	if err != nil {
+		return nil, err
+	}
+
+	year, err := readString(r, 4)
+	if err != nil {
+		return nil, err
+	}
+
+	commentBytes, err := readBytes(r, 30)
+	if err != nil {
+		return nil, err
+	}
+
+	var comment string
+	var track int
+	if commentBytes[28] == 0 {
+		comment = trimString(string(commentBytes[:28]))
+		track = int(commentBytes[29])
+	} else {
+		comment = trimString(string(commentBytes))
+	}
+
+	var genre string
+	genreID, err := readBytes(r, 1)
+	if err != nil {
+		return nil, err
+	}
+	if int(genreID[0]) < len(id3v1Genres) {
+		genre = id3v1Genres[int(genreID[0])]
+	}
+
+	m := make(map[string]interface{})
+	m["title"] = trimString(title)
+	m["artist"] = trimString(artist)
+	m["album"] = trimString(album)
+	m["year"] = trimString(year)
+	m["comment"] = trimString(comment)
+	m["track"] = track
+	m["genre"] = genre
+
+	return metadataID3v1(m), nil
+}
+
+func trimString(x string) string {
+	return strings.TrimSpace(strings.Trim(x, "\x00"))
+}
+
+// metadataID3v1 is the implementation of Metadata used for ID3v1 tags.
+type metadataID3v1 map[string]interface{}
+
+func (metadataID3v1) Format() Format                { return ID3v1 }
+func (metadataID3v1) FileType() FileType            { return MP3 }
+func (m metadataID3v1) Raw() map[string]interface{} { return m }
+
+func (m metadataID3v1) Title() string  { return m["title"].(string) }
+func (m metadataID3v1) Album() string  { return m["album"].(string) }
+func (m metadataID3v1) Artist() string { return m["artist"].(string) }
+func (m metadataID3v1) Genre() string  { return m["genre"].(string) }
+
+func (m metadataID3v1) Year() int {
+	y := m["year"].(string)
+	n, err := strconv.Atoi(y)
+	if err != nil {
+		return 0
+	}
+	return n
+}
+
+func (m metadataID3v1) Track() (int, int) { return m["track"].(int), 0 }
+
+func (m metadataID3v1) AlbumArtist() string { return "" }
+func (m metadataID3v1) Composer() string    { return "" }
+func (metadataID3v1) Disc() (int, int)      { return 0, 0 }
+func (m metadataID3v1) Picture() *Picture   { return nil }
+func (m metadataID3v1) Lyrics() string      { return "" }
+func (m metadataID3v1) Comment() string     { return m["comment"].(string) }

vendor/github.com/dhowden/tag/id3v2.go

@@ -0,0 +1,469 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// Genre definitions 0-79 follow the ID3 tag specification of 1999.
+// More genres have been successively introduced in later Winamp versions.
+// https://en.wikipedia.org/wiki/List_of_ID3v1_genres#Extension_by_Winamp
+var id3v2Genres = [...]string{
+	"Blues", "Classic Rock", "Country", "Dance", "Disco", "Funk", "Grunge",
+	"Hip-Hop", "Jazz", "Metal", "New Age", "Oldies", "Other", "Pop", "R&B",
+	"Rap", "Reggae", "Rock", "Techno", "Industrial", "Alternative", "Ska",
+	"Death Metal", "Pranks", "Soundtrack", "Euro-Techno", "Ambient",
+	"Trip-Hop", "Vocal", "Jazz+Funk", "Fusion", "Trance", "Classical",
+	"Instrumental", "Acid", "House", "Game", "Sound Clip", "Gospel",
+	"Noise", "AlternRock", "Bass", "Soul", "Punk", "Space", "Meditative",
+	"Instrumental Pop", "Instrumental Rock", "Ethnic", "Gothic",
+	"Darkwave", "Techno-Industrial", "Electronic", "Pop-Folk",
+	"Eurodance", "Dream", "Southern Rock", "Comedy", "Cult", "Gangsta",
+	"Top 40", "Christian Rap", "Pop/Funk", "Jungle", "Native American",
+	"Cabaret", "New Wave", "Psychedelic", "Rave", "Showtunes", "Trailer",
+	"Lo-Fi", "Tribal", "Acid Punk", "Acid Jazz", "Polka", "Retro",
+	"Musical", "Rock & Roll", "Hard Rock", "Folk", "Folk-Rock",
+	"National Folk", "Swing", "Fast Fusion", "Bebob", "Latin", "Revival",
+	"Celtic", "Bluegrass", "Avantgarde", "Gothic Rock", "Progressive Rock",
+	"Psychedelic Rock", "Symphonic Rock", "Slow Rock", "Big Band",
+	"Chorus", "Easy Listening", "Acoustic", "Humour", "Speech", "Chanson",
+	"Opera", "Chamber Music", "Sonata", "Symphony", "Booty Bass", "Primus",
+	"Porn Groove", "Satire", "Slow Jam", "Club", "Tango", "Samba",
+	"Folklore", "Ballad", "Power Ballad", "Rhythmic Soul", "Freestyle",
+	"Duet", "Punk Rock", "Drum Solo", "A capella", "Euro-House", "Dance Hall",
+	"Goa", "Drum & Bass", "Club-House", "Hardcore", "Terror", "Indie",
+	"Britpop", "Negerpunk", "Polsk Punk", "Beat", "Christian Gangsta Rap",
+	"Heavy Metal", "Black Metal", "Crossover", "Contemporary Christian",
+	"Christian Rock ", "Merengue", "Salsa", "Thrash Metal", "Anime", "JPop",
+	"Synthpop",
+	"Christmas", "Art Rock", "Baroque", "Bhangra", "Big Beat", "Breakbeat",
+	"Chillout", "Downtempo", "Dub", "EBM", "Eclectic", "Electro",
+	"Electroclash", "Emo", "Experimental", "Garage", "Global", "IDM",
+	"Illbient", "Industro-Goth", "Jam Band", "Krautrock", "Leftfield", "Lounge",
+	"Math Rock", "New Romantic", "Nu-Breakz", "Post-Punk", "Post-Rock", "Psytrance",
+	"Shoegaze", "Space Rock", "Trop Rock", "World Music", "Neoclassical", "Audiobook",
+	"Audio Theatre", "Neue Deutsche Welle", "Podcast", "Indie Rock", "G-Funk", "Dubstep",
+	"Garage Rock", "Psybient",
+}
+
+// id3v2Header is a type which represents an ID3v2 tag header.
+type id3v2Header struct {
+	Version           Format
+	Unsynchronisation bool
+	ExtendedHeader    bool
+	Experimental      bool
+	Size              uint
+}
+
+// readID3v2Header reads the ID3v2 header from the given io.Reader.
+// offset it number of bytes of header that was read
+func readID3v2Header(r io.Reader) (h *id3v2Header, offset uint, err error) {
+	offset = 10
+	b, err := readBytes(r, offset)
+	if err != nil {
+		return nil, 0, fmt.Errorf("expected to read 10 bytes (ID3v2Header): %v", err)
+	}
+
+	if string(b[0:3]) != "ID3" {
+		return nil, 0, fmt.Errorf("expected to read \"ID3\"")
+	}
+
+	b = b[3:]
+	var vers Format
+	switch uint(b[0]) {
+	case 2:
+		vers = ID3v2_2
+	case 3:
+		vers = ID3v2_3
+	case 4:
+		vers = ID3v2_4
+	case 0, 1:
+		fallthrough
+	default:
+		return nil, 0, fmt.Errorf("ID3 version: %v, expected: 2, 3 or 4", uint(b[0]))
+	}
+
+	// NB: We ignore b[1] (the revision) as we don't currently rely on it.
+	h = &id3v2Header{
+		Version:           vers,
+		Unsynchronisation: getBit(b[2], 7),
+		ExtendedHeader:    getBit(b[2], 6),
+		Experimental:      getBit(b[2], 5),
+		Size:              uint(get7BitChunkedInt(b[3:7])),
+	}
+
+	if h.ExtendedHeader {
+		switch vers {
+		case ID3v2_3:
+			b, err := readBytes(r, 4)
+			if err != nil {
+				return nil, 0, fmt.Errorf("expected to read 4 bytes (ID3v23 extended header len): %v", err)
+			}
+			// skip header, size is excluding len bytes
+			extendedHeaderSize := uint(getInt(b))
+			_, err = readBytes(r, extendedHeaderSize)
+			if err != nil {
+				return nil, 0, fmt.Errorf("expected to read %d bytes (ID3v23 skip extended header): %v", extendedHeaderSize, err)
+			}
+			offset += extendedHeaderSize
+		case ID3v2_4:
+			b, err := readBytes(r, 4)
+			if err != nil {
+				return nil, 0, fmt.Errorf("expected to read 4 bytes (ID3v24 extended header len): %v", err)
+			}
+			// skip header, size is synchsafe int including len bytes
+			extendedHeaderSize := uint(get7BitChunkedInt(b)) - 4
+			_, err = readBytes(r, extendedHeaderSize)
+			if err != nil {
+				return nil, 0, fmt.Errorf("expected to read %d bytes (ID3v24 skip extended header): %v", extendedHeaderSize, err)
+			}
+			offset += extendedHeaderSize
+		default:
+			// nop, only 2.3 and 2.4 should have extended header
+		}
+	}
+
+	return h, offset, nil
+}
+
+// id3v2FrameFlags is a type which represents the flags which can be set on an ID3v2 frame.
+type id3v2FrameFlags struct {
+	// Message (ID3 2.3.0 and 2.4.0)
+	TagAlterPreservation  bool
+	FileAlterPreservation bool
+	ReadOnly              bool
+
+	// Format (ID3 2.3.0 and 2.4.0)
+	Compression   bool
+	Encryption    bool
+	GroupIdentity bool
+	// ID3 2.4.0 only (see http://id3.org/id3v2.4.0-structure sec 4.1)
+	Unsynchronisation   bool
+	DataLengthIndicator bool
+}
+
+func readID3v23FrameFlags(r io.Reader) (*id3v2FrameFlags, error) {
+	b, err := readBytes(r, 2)
+	if err != nil {
+		return nil, err
+	}
+
+	msg := b[0]
+	fmt := b[1]
+
+	return &id3v2FrameFlags{
+		TagAlterPreservation:  getBit(msg, 7),
+		FileAlterPreservation: getBit(msg, 6),
+		ReadOnly:              getBit(msg, 5),
+		Compression:           getBit(fmt, 7),
+		Encryption:            getBit(fmt, 6),
+		GroupIdentity:         getBit(fmt, 5),
+	}, nil
+}
+
+func readID3v24FrameFlags(r io.Reader) (*id3v2FrameFlags, error) {
+	b, err := readBytes(r, 2)
+	if err != nil {
+		return nil, err
+	}
+
+	msg := b[0]
+	fmt := b[1]
+
+	return &id3v2FrameFlags{
+		TagAlterPreservation:  getBit(msg, 6),
+		FileAlterPreservation: getBit(msg, 5),
+		ReadOnly:              getBit(msg, 4),
+		GroupIdentity:         getBit(fmt, 6),
+		Compression:           getBit(fmt, 3),
+		Encryption:            getBit(fmt, 2),
+		Unsynchronisation:     getBit(fmt, 1),
+		DataLengthIndicator:   getBit(fmt, 0),
+	}, nil
+
+}
+
+func readID3v2_2FrameHeader(r io.Reader) (name string, size uint, headerSize uint, err error) {
+	name, err = readString(r, 3)
+	if err != nil {
+		return
+	}
+	size, err = readUint(r, 3)
+	if err != nil {
+		return
+	}
+	headerSize = 6
+	return
+}
+
+func readID3v2_3FrameHeader(r io.Reader) (name string, size uint, headerSize uint, err error) {
+	name, err = readString(r, 4)
+	if err != nil {
+		return
+	}
+	size, err = readUint(r, 4)
+	if err != nil {
+		return
+	}
+	headerSize = 8
+	return
+}
+
+func readID3v2_4FrameHeader(r io.Reader) (name string, size uint, headerSize uint, err error) {
+	name, err = readString(r, 4)
+	if err != nil {
+		return
+	}
+	size, err = read7BitChunkedUint(r, 4)
+	if err != nil {
+		return
+	}
+	headerSize = 8
+	return
+}
+
+// readID3v2Frames reads ID3v2 frames from the given reader using the ID3v2Header.
+func readID3v2Frames(r io.Reader, offset uint, h *id3v2Header) (map[string]interface{}, error) {
+	result := make(map[string]interface{})
+
+	for offset < h.Size {
+		var err error
+		var name string
+		var size, headerSize uint
+		var flags *id3v2FrameFlags
+
+		switch h.Version {
+		case ID3v2_2:
+			name, size, headerSize, err = readID3v2_2FrameHeader(r)
+
+		case ID3v2_3:
+			name, size, headerSize, err = readID3v2_3FrameHeader(r)
+			if err != nil {
+				return nil, err
+			}
+			flags, err = readID3v23FrameFlags(r)
+			headerSize += 2
+
+		case ID3v2_4:
+			name, size, headerSize, err = readID3v2_4FrameHeader(r)
+			if err != nil {
+				return nil, err
+			}
+			flags, err = readID3v24FrameFlags(r)
+			headerSize += 2
+		}
+
+		if err != nil {
+			return nil, err
+		}
+
+		// FIXME: Do we still need this?
+		// if size=0, we certainly are in a padding zone. ignore the rest of
+		// the tags
+		if size == 0 {
+			break
+		}
+
+		offset += headerSize + size
+
+		// Avoid corrupted padding (see http://id3.org/Compliance%20Issues).
+		if !validID3Frame(h.Version, name) && offset > h.Size {
+			break
+		}
+
+		if flags != nil {
+			if flags.Compression {
+				switch h.Version {
+				case ID3v2_3:
+					// No data length indicator defined.
+					if _, err := read7BitChunkedUint(r, 4); err != nil { // read 4
+						return nil, err
+					}
+					size -= 4
+
+				case ID3v2_4:
+					// Must have a data length indicator (to give the size) if compression is enabled.
+					if !flags.DataLengthIndicator {
+						return nil, errors.New("compression without data length indicator")
+					}
+
+				default:
+					return nil, fmt.Errorf("unsupported compression flag used in %v", h.Version)
+				}
+			}
+
+			if flags.DataLengthIndicator {
+				if h.Version == ID3v2_3 {
+					return nil, fmt.Errorf("data length indicator set but not defined for %v", ID3v2_3)
+				}
+
+				size, err = read7BitChunkedUint(r, 4)
+				if err != nil { // read 4
+					return nil, err
+				}
+			}
+
+			if flags.Encryption {
+				_, err = readBytes(r, 1) // read 1 byte of encryption method
+				if err != nil {
+					return nil, err
+				}
+				size--
+			}
+		}
+
+		b, err := readBytes(r, size)
+		if err != nil {
+			return nil, err
+		}
+
+		// There can be multiple tag with the same name. Append a number to the
+		// name if there is more than one.
+		rawName := name
+		if _, ok := result[rawName]; ok {
+			for i := 0; ok; i++ {
+				rawName = name + "_" + strconv.Itoa(i)
+				_, ok = result[rawName]
+			}
+		}
+
+		switch {
+		case name == "TXXX" || name == "TXX":
+			t, err := readTextWithDescrFrame(b, false, true) // no lang, but enc
+			if err != nil {
+				return nil, err
+			}
+			result[rawName] = t
+
+		case name[0] == 'T':
+			txt, err := readTFrame(b)
+			if err != nil {
+				return nil, err
+			}
+			result[rawName] = txt
+
+		case name == "UFID" || name == "UFI":
+			t, err := readUFID(b)
+			if err != nil {
+				return nil, err
+			}
+			result[rawName] = t
+
+		case name == "WXXX" || name == "WXX":
+			t, err := readTextWithDescrFrame(b, false, false) // no lang, no enc
+			if err != nil {
+				return nil, err
+			}
+			result[rawName] = t
+
+		case name[0] == 'W':
+			txt, err := readWFrame(b)
+			if err != nil {
+				return nil, err
+			}
+			result[rawName] = txt
+
+		case name == "COMM" || name == "COM" || name == "USLT" || name == "ULT":
+			t, err := readTextWithDescrFrame(b, true, true) // both lang and enc
+			if err != nil {
+				return nil, fmt.Errorf("could not read %q (%q): %v", name, rawName, err)
+			}
+			result[rawName] = t
+
+		case name == "APIC":
+			p, err := readAPICFrame(b)
+			if err != nil {
+				return nil, err
+			}
+			result[rawName] = p
+
+		case name == "PIC":
+			p, err := readPICFrame(b)
+			if err != nil {
+				return nil, err
+			}
+			result[rawName] = p
+
+		default:
+			result[rawName] = b
+		}
+	}
+	return result, nil
+}
+
+type unsynchroniser struct {
+	io.Reader
+	ff bool
+}
+
+// filter io.Reader which skip the Unsynchronisation bytes
+func (r *unsynchroniser) Read(p []byte) (int, error) {
+	b := make([]byte, 1)
+	i := 0
+	for i < len(p) {
+		if n, err := r.Reader.Read(b); err != nil || n == 0 {
+			return i, err
+		}
+		if r.ff && b[0] == 0x00 {
+			r.ff = false
+			continue
+		}
+		p[i] = b[0]
+		i++
+		r.ff = (b[0] == 0xFF)
+	}
+	return i, nil
+}
+
+// ReadID3v2Tags parses ID3v2.{2,3,4} tags from the io.ReadSeeker into a Metadata, returning
+// non-nil error on failure.
+func ReadID3v2Tags(r io.ReadSeeker) (Metadata, error) {
+	h, offset, err := readID3v2Header(r)
+	if err != nil {
+		return nil, err
+	}
+
+	var ur io.Reader = r
+	if h.Unsynchronisation {
+		ur = &unsynchroniser{Reader: r}
+	}
+
+	f, err := readID3v2Frames(ur, offset, h)
+	if err != nil {
+		return nil, err
+	}
+	return metadataID3v2{header: h, frames: f}, nil
+}
+
+var id3v2genreRe = regexp.MustCompile(`(.*[^(]|.* |^)\(([0-9]+)\) *(.*)$`)
+
+//  id3v2genre parse a id3v2 genre tag and expand the numeric genres
+func id3v2genre(genre string) string {
+	c := true
+	for c {
+		orig := genre
+		if match := id3v2genreRe.FindStringSubmatch(genre); len(match) > 0 {
+			if genreID, err := strconv.Atoi(match[2]); err == nil {
+				if genreID < len(id3v2Genres) {
+					genre = id3v2Genres[genreID]
+					if match[1] != "" {
+						genre = strings.TrimSpace(match[1]) + " " + genre
+					}
+					if match[3] != "" {
+						genre = genre + " " + match[3]
+					}
+				}
+			}
+		}
+		c = (orig != genre)
+	}
+	return strings.Replace(genre, "((", "(", -1)
+}

vendor/github.com/dhowden/tag/id3v2frames.go

@@ -0,0 +1,655 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"strings"
+	"unicode/utf16"
+)
+
+// DefaultUTF16WithBOMByteOrder is the byte order used when the "UTF16 with BOM" encoding
+// is specified without a corresponding BOM in the data.
+var DefaultUTF16WithBOMByteOrder binary.ByteOrder = binary.LittleEndian
+
+// ID3v2.2.0 frames (see http://id3.org/id3v2-00, sec 4).
+var id3v22Frames = map[string]string{
+	"BUF": "Recommended buffer size",
+
+	"CNT": "Play counter",
+	"COM": "Comments",
+	"CRA": "Audio encryption",
+	"CRM": "Encrypted meta frame",
+
+	"ETC": "Event timing codes",
+	"EQU": "Equalization",
+
+	"GEO": "General encapsulated object",
+
+	"IPL": "Involved people list",
+
+	"LNK": "Linked information",
+
+	"MCI": "Music CD Identifier",
+	"MLL": "MPEG location lookup table",
+
+	"PIC": "Attached picture",
+	"POP": "Popularimeter",
+
+	"REV": "Reverb",
+	"RVA": "Relative volume adjustment",
+
+	"SLT": "Synchronized lyric/text",
+	"STC": "Synced tempo codes",
+
+	"TAL": "Album/Movie/Show title",
+	"TBP": "BPM (Beats Per Minute)",
+	"TCM": "Composer",
+	"TCO": "Content type",
+	"TCR": "Copyright message",
+	"TDA": "Date",
+	"TDY": "Playlist delay",
+	"TEN": "Encoded by",
+	"TFT": "File type",
+	"TIM": "Time",
+	"TKE": "Initial key",
+	"TLA": "Language(s)",
+	"TLE": "Length",
+	"TMT": "Media type",
+	"TOA": "Original artist(s)/performer(s)",
+	"TOF": "Original filename",
+	"TOL": "Original Lyricist(s)/text writer(s)",
+	"TOR": "Original release year",
+	"TOT": "Original album/Movie/Show title",
+	"TP1": "Lead artist(s)/Lead performer(s)/Soloist(s)/Performing group",
+	"TP2": "Band/Orchestra/Accompaniment",
+	"TP3": "Conductor/Performer refinement",
+	"TP4": "Interpreted, remixed, or otherwise modified by",
+	"TPA": "Part of a set",
+	"TPB": "Publisher",
+	"TRC": "ISRC (International Standard Recording Code)",
+	"TRD": "Recording dates",
+	"TRK": "Track number/Position in set",
+	"TSI": "Size",
+	"TSS": "Software/hardware and settings used for encoding",
+	"TT1": "Content group description",
+	"TT2": "Title/Songname/Content description",
+	"TT3": "Subtitle/Description refinement",
+	"TXT": "Lyricist/text writer",
+	"TXX": "User defined text information frame",
+	"TYE": "Year",
+
+	"UFI": "Unique file identifier",
+	"ULT": "Unsychronized lyric/text transcription",
+
+	"WAF": "Official audio file webpage",
+	"WAR": "Official artist/performer webpage",
+	"WAS": "Official audio source webpage",
+	"WCM": "Commercial information",
+	"WCP": "Copyright/Legal information",
+	"WPB": "Publishers official webpage",
+	"WXX": "User defined URL link frame",
+}
+
+// ID3v2.3.0 frames (see http://id3.org/id3v2.3.0#Declared_ID3v2_frames).
+var id3v23Frames = map[string]string{
+	"AENC": "Audio encryption]",
+	"APIC": "Attached picture",
+	"COMM": "Comments",
+	"COMR": "Commercial frame",
+	"ENCR": "Encryption method registration",
+	"EQUA": "Equalization",
+	"ETCO": "Event timing codes",
+	"GEOB": "General encapsulated object",
+	"GRID": "Group identification registration",
+	"IPLS": "Involved people list",
+	"LINK": "Linked information",
+	"MCDI": "Music CD identifier",
+	"MLLT": "MPEG location lookup table",
+	"OWNE": "Ownership frame",
+	"PRIV": "Private frame",
+	"PCNT": "Play counter",
+	"POPM": "Popularimeter",
+	"POSS": "Position synchronisation frame",
+	"RBUF": "Recommended buffer size",
+	"RVAD": "Relative volume adjustment",
+	"RVRB": "Reverb",
+	"SYLT": "Synchronized lyric/text",
+	"SYTC": "Synchronized tempo codes",
+	"TALB": "Album/Movie/Show title",
+	"TBPM": "BPM (beats per minute)",
+	"TCMP": "iTunes Compilation Flag",
+	"TCOM": "Composer",
+	"TCON": "Content type",
+	"TCOP": "Copyright message",
+	"TDAT": "Date",
+	"TDLY": "Playlist delay",
+	"TENC": "Encoded by",
+	"TEXT": "Lyricist/Text writer",
+	"TFLT": "File type",
+	"TIME": "Time",
+	"TIT1": "Content group description",
+	"TIT2": "Title/songname/content description",
+	"TIT3": "Subtitle/Description refinement",
+	"TKEY": "Initial key",
+	"TLAN": "Language(s)",
+	"TLEN": "Length",
+	"TMED": "Media type",
+	"TOAL": "Original album/movie/show title",
+	"TOFN": "Original filename",
+	"TOLY": "Original lyricist(s)/text writer(s)",
+	"TOPE": "Original artist(s)/performer(s)",
+	"TORY": "Original release year",
+	"TOWN": "File owner/licensee",
+	"TPE1": "Lead performer(s)/Soloist(s)",
+	"TPE2": "Band/orchestra/accompaniment",
+	"TPE3": "Conductor/performer refinement",
+	"TPE4": "Interpreted, remixed, or otherwise modified by",
+	"TPOS": "Part of a set",
+	"TPUB": "Publisher",
+	"TRCK": "Track number/Position in set",
+	"TRDA": "Recording dates",
+	"TRSN": "Internet radio station name",
+	"TRSO": "Internet radio station owner",
+	"TSIZ": "Size",
+	"TSO2": "iTunes uses this for Album Artist sort order",
+	"TSOC": "iTunes uses this for Composer sort order",
+	"TSRC": "ISRC (international standard recording code)",
+	"TSSE": "Software/Hardware and settings used for encoding",
+	"TYER": "Year",
+	"TXXX": "User defined text information frame",
+	"UFID": "Unique file identifier",
+	"USER": "Terms of use",
+	"USLT": "Unsychronized lyric/text transcription",
+	"WCOM": "Commercial information",
+	"WCOP": "Copyright/Legal information",
+	"WOAF": "Official audio file webpage",
+	"WOAR": "Official artist/performer webpage",
+	"WOAS": "Official audio source webpage",
+	"WORS": "Official internet radio station homepage",
+	"WPAY": "Payment",
+	"WPUB": "Publishers official webpage",
+	"WXXX": "User defined URL link frame",
+}
+
+// ID3v2.4.0 frames (see http://id3.org/id3v2.4.0-frames, sec 4).
+var id3v24Frames = map[string]string{
+	"AENC": "Audio encryption",
+	"APIC": "Attached picture",
+	"ASPI": "Audio seek point index",
+
+	"COMM": "Comments",
+	"COMR": "Commercial frame",
+
+	"ENCR": "Encryption method registration",
+	"EQU2": "Equalisation (2)",
+	"ETCO": "Event timing codes",
+
+	"GEOB": "General encapsulated object",
+	"GRID": "Group identification registration",
+
+	"LINK": "Linked information",
+
+	"MCDI": "Music CD identifier",
+	"MLLT": "MPEG location lookup table",
+
+	"OWNE": "Ownership frame",
+
+	"PRIV": "Private frame",
+	"PCNT": "Play counter",
+	"POPM": "Popularimeter",
+	"POSS": "Position synchronisation frame",
+
+	"RBUF": "Recommended buffer size",
+	"RVA2": "Relative volume adjustment (2)",
+	"RVRB": "Reverb",
+
+	"SEEK": "Seek frame",
+	"SIGN": "Signature frame",
+	"SYLT": "Synchronised lyric/text",
+	"SYTC": "Synchronised tempo codes",
+
+	"TALB": "Album/Movie/Show title",
+	"TBPM": "BPM (beats per minute)",
+	"TCMP": "iTunes Compilation Flag",
+	"TCOM": "Composer",
+	"TCON": "Content type",
+	"TCOP": "Copyright message",
+	"TDEN": "Encoding time",
+	"TDLY": "Playlist delay",
+	"TDOR": "Original release time",
+	"TDRC": "Recording time",
+	"TDRL": "Release time",
+	"TDTG": "Tagging time",
+	"TENC": "Encoded by",
+	"TEXT": "Lyricist/Text writer",
+	"TFLT": "File type",
+	"TIPL": "Involved people list",
+	"TIT1": "Content group description",
+	"TIT2": "Title/songname/content description",
+	"TIT3": "Subtitle/Description refinement",
+	"TKEY": "Initial key",
+	"TLAN": "Language(s)",
+	"TLEN": "Length",
+	"TMCL": "Musician credits list",
+	"TMED": "Media type",
+	"TMOO": "Mood",
+	"TOAL": "Original album/movie/show title",
+	"TOFN": "Original filename",
+	"TOLY": "Original lyricist(s)/text writer(s)",
+	"TOPE": "Original artist(s)/performer(s)",
+	"TOWN": "File owner/licensee",
+	"TPE1": "Lead performer(s)/Soloist(s)",
+	"TPE2": "Band/orchestra/accompaniment",
+	"TPE3": "Conductor/performer refinement",
+	"TPE4": "Interpreted, remixed, or otherwise modified by",
+	"TPOS": "Part of a set",
+	"TPRO": "Produced notice",
+	"TPUB": "Publisher",
+	"TRCK": "Track number/Position in set",
+	"TRSN": "Internet radio station name",
+	"TRSO": "Internet radio station owner",
+	"TSO2": "iTunes uses this for Album Artist sort order",
+	"TSOA": "Album sort order",
+	"TSOC": "iTunes uses this for Composer sort order",
+	"TSOP": "Performer sort order",
+	"TSOT": "Title sort order",
+	"TSRC": "ISRC (international standard recording code)",
+	"TSSE": "Software/Hardware and settings used for encoding",
+	"TSST": "Set subtitle",
+	"TXXX": "User defined text information frame",
+
+	"UFID": "Unique file identifier",
+	"USER": "Terms of use",
+	"USLT": "Unsynchronised lyric/text transcription",
+
+	"WCOM": "Commercial information",
+	"WCOP": "Copyright/Legal information",
+	"WOAF": "Official audio file webpage",
+	"WOAR": "Official artist/performer webpage",
+	"WOAS": "Official audio source webpage",
+	"WORS": "Official Internet radio station homepage",
+	"WPAY": "Payment",
+	"WPUB": "Publishers official webpage",
+	"WXXX": "User defined URL link frame",
+}
+
+// ID3 frames that are defined in the specs.
+var id3Frames = map[Format]map[string]string{
+	ID3v2_2: id3v22Frames,
+	ID3v2_3: id3v23Frames,
+	ID3v2_4: id3v24Frames,
+}
+
+func validID3Frame(version Format, name string) bool {
+	names, ok := id3Frames[version]
+	if !ok {
+		return false
+	}
+	_, ok = names[name]
+	return ok
+}
+
+func readWFrame(b []byte) (string, error) {
+	// Frame text is always encoded in ISO-8859-1
+	b = append([]byte{0}, b...)
+	return readTFrame(b)
+}
+
+func readTFrame(b []byte) (string, error) {
+	if len(b) == 0 {
+		return "", nil
+	}
+
+	txt, err := decodeText(b[0], b[1:])
+	if err != nil {
+		return "", err
+	}
+	return strings.Join(strings.Split(txt, string(singleZero)), ""), nil
+}
+
+const (
+	encodingISO8859      byte = 0
+	encodingUTF16WithBOM byte = 1
+	encodingUTF16        byte = 2
+	encodingUTF8         byte = 3
+)
+
+func decodeText(enc byte, b []byte) (string, error) {
+	if len(b) == 0 {
+		return "", nil
+	}
+
+	switch enc {
+	case encodingISO8859: // ISO-8859-1
+		return decodeISO8859(b), nil
+
+	case encodingUTF16WithBOM: // UTF-16 with byte order marker
+		if len(b) == 1 {
+			return "", nil
+		}
+		return decodeUTF16WithBOM(b)
+
+	case encodingUTF16: // UTF-16 without byte order (assuming BigEndian)
+		if len(b) == 1 {
+			return "", nil
+		}
+		return decodeUTF16(b, binary.BigEndian)
+
+	case encodingUTF8: // UTF-8
+		return string(b), nil
+
+	default: // Fallback to ISO-8859-1
+		return decodeISO8859(b), nil
+	}
+}
+
+var (
+	singleZero = []byte{0}
+	doubleZero = []byte{0, 0}
+)
+
+func dataSplit(b []byte, enc byte) [][]byte {
+	delim := singleZero
+	if enc == encodingUTF16 || enc == encodingUTF16WithBOM {
+		delim = doubleZero
+	}
+
+	result := bytes.SplitN(b, delim, 2)
+	if len(result) != 2 {
+		return result
+	}
+
+	if len(result[1]) == 0 {
+		return result
+	}
+
+	if result[1][0] == 0 {
+		// there was a double (or triple) 0 and we cut too early
+		result[0] = append(result[0], result[1][0])
+		result[1] = result[1][1:]
+	}
+	return result
+}
+
+func decodeISO8859(b []byte) string {
+	r := make([]rune, len(b))
+	for i, x := range b {
+		r[i] = rune(x)
+	}
+	return string(r)
+}
+
+func decodeUTF16WithBOM(b []byte) (string, error) {
+	if len(b) < 2 {
+		return "", errors.New("invalid encoding: expected at least 2 bytes for UTF-16 byte order mark")
+	}
+
+	var bo binary.ByteOrder
+	switch {
+	case b[0] == 0xFE && b[1] == 0xFF:
+		bo = binary.BigEndian
+		b = b[2:]
+
+	case b[0] == 0xFF && b[1] == 0xFE:
+		bo = binary.LittleEndian
+		b = b[2:]
+
+	default:
+		bo = DefaultUTF16WithBOMByteOrder
+	}
+	return decodeUTF16(b, bo)
+}
+
+func decodeUTF16(b []byte, bo binary.ByteOrder) (string, error) {
+	if len(b)%2 != 0 {
+		return "", errors.New("invalid encoding: expected even number of bytes for UTF-16 encoded text")
+	}
+	s := make([]uint16, 0, len(b)/2)
+	for i := 0; i < len(b); i += 2 {
+		s = append(s, bo.Uint16(b[i:i+2]))
+	}
+	return string(utf16.Decode(s)), nil
+}
+
+// Comm is a type used in COMM, UFID, TXXX, WXXX and USLT tag.
+// It's a text with a description and a specified language
+// For WXXX, TXXX and UFID, we don't set a Language
+type Comm struct {
+	Language    string
+	Description string
+	Text        string
+}
+
+// String returns a string representation of the underlying Comm instance.
+func (t Comm) String() string {
+	if t.Language != "" {
+		return fmt.Sprintf("Text{Lang: '%v', Description: '%v', %v lines}",
+			t.Language, t.Description, strings.Count(t.Text, "\n"))
+	}
+	return fmt.Sprintf("Text{Description: '%v', %v}", t.Description, t.Text)
+}
+
+// IDv2.{3,4}
+// -- Header
+// <Header for 'Unsynchronised lyrics/text transcription', ID: "USLT">
+// <Header for 'Comment', ID: "COMM">
+// -- readTextWithDescrFrame(data, true, true)
+// Text encoding       $xx
+// Language            $xx xx xx
+// Content descriptor  <text string according to encoding> $00 (00)
+// Lyrics/text         <full text string according to encoding>
+// -- Header
+// <Header for         'User defined text information frame', ID: "TXXX">
+// <Header for         'User defined URL link frame', ID: "WXXX">
+// -- readTextWithDescrFrame(data, false, <isDataEncoded>)
+// Text encoding       $xx
+// Description         <text string according to encoding> $00 (00)
+// Value               <text string according to encoding>
+func readTextWithDescrFrame(b []byte, hasLang bool, encoded bool) (*Comm, error) {
+	if len(b) == 0 {
+		return nil, errors.New("error decoding tag description text: invalid encoding")
+	}
+	enc := b[0]
+	b = b[1:]
+
+	c := &Comm{}
+	if hasLang {
+		if len(b) < 3 {
+			return nil, errors.New("hasLang set but not enough data for language information")
+		}
+		c.Language = string(b[:3])
+		b = b[3:]
+	}
+
+	descTextSplit := dataSplit(b, enc)
+	if len(descTextSplit) == 0 {
+		return nil, errors.New("error decoding tag description text: invalid encoding")
+	}
+
+	desc, err := decodeText(enc, descTextSplit[0])
+	if err != nil {
+		return nil, fmt.Errorf("error decoding tag description text: %v", err)
+	}
+	c.Description = desc
+
+	if len(descTextSplit) == 1 {
+		return c, nil
+	}
+
+	if !encoded {
+		enc = byte(0)
+	}
+	text, err := decodeText(enc, descTextSplit[1])
+	if err != nil {
+		return nil, fmt.Errorf("error decoding tag text: %v", err)
+	}
+	c.Text = text
+
+	return c, nil
+}
+
+// UFID is composed of a provider (frequently a URL and a binary identifier)
+// The identifier can be a text (Musicbrainz use texts, but not necessary)
+type UFID struct {
+	Provider   string
+	Identifier []byte
+}
+
+func (u UFID) String() string {
+	return fmt.Sprintf("%v (%v)", u.Provider, string(u.Identifier))
+}
+
+func readUFID(b []byte) (*UFID, error) {
+	result := bytes.SplitN(b, singleZero, 2)
+	if len(result) != 2 {
+		return nil, errors.New("expected to split UFID data into 2 pieces")
+	}
+
+	return &UFID{
+		Provider:   string(result[0]),
+		Identifier: result[1],
+	}, nil
+}
+
+var pictureTypes = map[byte]string{
+	0x00: "Other",
+	0x01: "32x32 pixels 'file icon' (PNG only)",
+	0x02: "Other file icon",
+	0x03: "Cover (front)",
+	0x04: "Cover (back)",
+	0x05: "Leaflet page",
+	0x06: "Media (e.g. lable side of CD)",
+	0x07: "Lead artist/lead performer/soloist",
+	0x08: "Artist/performer",
+	0x09: "Conductor",
+	0x0A: "Band/Orchestra",
+	0x0B: "Composer",
+	0x0C: "Lyricist/text writer",
+	0x0D: "Recording Location",
+	0x0E: "During recording",
+	0x0F: "During performance",
+	0x10: "Movie/video screen capture",
+	0x11: "A bright coloured fish",
+	0x12: "Illustration",
+	0x13: "Band/artist logotype",
+	0x14: "Publisher/Studio logotype",
+}
+
+// Picture is a type which represents an attached picture extracted from metadata.
+type Picture struct {
+	Ext         string // Extension of the picture file.
+	MIMEType    string // MIMEType of the picture.
+	Type        string // Type of the picture (see pictureTypes).
+	Description string // Description.
+	Data        []byte // Raw picture data.
+}
+
+// String returns a string representation of the underlying Picture instance.
+func (p Picture) String() string {
+	return fmt.Sprintf("Picture{Ext: %v, MIMEType: %v, Type: %v, Description: %v, Data.Size: %v}",
+		p.Ext, p.MIMEType, p.Type, p.Description, len(p.Data))
+}
+
+// IDv2.2
+// -- Header
+// Attached picture   "PIC"
+// Frame size         $xx xx xx
+// -- readPICFrame
+// Text encoding      $xx
+// Image format       $xx xx xx
+// Picture type       $xx
+// Description        <textstring> $00 (00)
+// Picture data       <binary data>
+func readPICFrame(b []byte) (*Picture, error) {
+	if len(b) < 5 {
+		return nil, errors.New("invalid PIC frame")
+	}
+
+	enc := b[0]
+	ext := string(b[1:4])
+	picType := b[4]
+
+	descDataSplit := dataSplit(b[5:], enc)
+	if len(descDataSplit) != 2 {
+		return nil, errors.New("error decoding PIC description text: invalid encoding")
+	}
+	desc, err := decodeText(enc, descDataSplit[0])
+	if err != nil {
+		return nil, fmt.Errorf("error decoding PIC description text: %v", err)
+	}
+
+	var mimeType string
+	switch ext {
+	case "jpeg", "jpg":
+		mimeType = "image/jpeg"
+	case "png":
+		mimeType = "image/png"
+	}
+
+	return &Picture{
+		Ext:         ext,
+		MIMEType:    mimeType,
+		Type:        pictureTypes[picType],
+		Description: desc,
+		Data:        descDataSplit[1],
+	}, nil
+}
+
+// IDv2.{3,4}
+// -- Header
+// <Header for 'Attached picture', ID: "APIC">
+// -- readAPICFrame
+// Text encoding   $xx
+// MIME type       <text string> $00
+// Picture type    $xx
+// Description     <text string according to encoding> $00 (00)
+// Picture data    <binary data>
+func readAPICFrame(b []byte) (*Picture, error) {
+	if len(b) == 0 {
+		return nil, errors.New("error decoding APIC: invalid encoding")
+	}
+	enc := b[0]
+	mimeDataSplit := bytes.SplitN(b[1:], singleZero, 2)
+	if len(mimeDataSplit) != 2 {
+		return nil, errors.New("error decoding APIC: invalid encoding")
+	}
+
+	mimeType := string(mimeDataSplit[0])
+
+	b = mimeDataSplit[1]
+	if len(b) < 1 {
+		return nil, fmt.Errorf("error decoding APIC mimetype")
+	}
+	picType := b[0]
+
+	descDataSplit := dataSplit(b[1:], enc)
+	if len(descDataSplit) != 2 {
+		return nil, errors.New("error decoding APIC description text: invalid encoding")
+	}
+	desc, err := decodeText(enc, descDataSplit[0])
+	if err != nil {
+		return nil, fmt.Errorf("error decoding APIC description text: %v", err)
+	}
+
+	var ext string
+	switch mimeType {
+	case "image/jpeg":
+		ext = "jpg"
+	case "image/png":
+		ext = "png"
+	}
+
+	return &Picture{
+		Ext:         ext,
+		MIMEType:    mimeType,
+		Type:        pictureTypes[picType],
+		Description: desc,
+		Data:        descDataSplit[1],
+	}, nil
+}

vendor/github.com/dhowden/tag/id3v2metadata.go

@@ -0,0 +1,152 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"strconv"
+	"strings"
+	"time"
+)
+
+type frameNames map[string][2]string
+
+func (f frameNames) Name(s string, fm Format) string {
+	l, ok := f[s]
+	if !ok {
+		return ""
+	}
+
+	switch fm {
+	case ID3v2_2:
+		return l[0]
+	case ID3v2_3:
+		return l[1]
+	case ID3v2_4:
+		if s == "year" {
+			return "TDRC"
+		}
+		return l[1]
+	}
+	return ""
+}
+
+var frames = frameNames(map[string][2]string{
+	"title":        [2]string{"TT2", "TIT2"},
+	"artist":       [2]string{"TP1", "TPE1"},
+	"album":        [2]string{"TAL", "TALB"},
+	"album_artist": [2]string{"TP2", "TPE2"},
+	"composer":     [2]string{"TCM", "TCOM"},
+	"year":         [2]string{"TYE", "TYER"},
+	"track":        [2]string{"TRK", "TRCK"},
+	"disc":         [2]string{"TPA", "TPOS"},
+	"genre":        [2]string{"TCO", "TCON"},
+	"picture":      [2]string{"PIC", "APIC"},
+	"lyrics":       [2]string{"", "USLT"},
+	"comment":      [2]string{"COM", "COMM"},
+})
+
+// metadataID3v2 is the implementation of Metadata used for ID3v2 tags.
+type metadataID3v2 struct {
+	header *id3v2Header
+	frames map[string]interface{}
+}
+
+func (m metadataID3v2) getString(k string) string {
+	v, ok := m.frames[k]
+	if !ok {
+		return ""
+	}
+	return v.(string)
+}
+
+func (m metadataID3v2) Format() Format              { return m.header.Version }
+func (m metadataID3v2) FileType() FileType          { return MP3 }
+func (m metadataID3v2) Raw() map[string]interface{} { return m.frames }
+
+func (m metadataID3v2) Title() string {
+	return m.getString(frames.Name("title", m.Format()))
+}
+
+func (m metadataID3v2) Artist() string {
+	return m.getString(frames.Name("artist", m.Format()))
+}
+
+func (m metadataID3v2) Album() string {
+	return m.getString(frames.Name("album", m.Format()))
+}
+
+func (m metadataID3v2) AlbumArtist() string {
+	return m.getString(frames.Name("album_artist", m.Format()))
+}
+
+func (m metadataID3v2) Composer() string {
+	return m.getString(frames.Name("composer", m.Format()))
+}
+
+func (m metadataID3v2) Genre() string {
+	return id3v2genre(m.getString(frames.Name("genre", m.Format())))
+}
+
+func (m metadataID3v2) Year() int {
+	stringYear := m.getString(frames.Name("year", m.Format()))
+
+	if year, err := strconv.Atoi(stringYear); err == nil {
+		return year
+	}
+
+	date, err := time.Parse(time.DateOnly, stringYear)
+	if err != nil {
+		return 0
+	}
+
+	return date.Year()
+}
+
+func parseXofN(s string) (x, n int) {
+	xn := strings.Split(s, "/")
+	if len(xn) != 2 {
+		x, _ = strconv.Atoi(s)
+		return x, 0
+	}
+	x, _ = strconv.Atoi(strings.TrimSpace(xn[0]))
+	n, _ = strconv.Atoi(strings.TrimSpace(xn[1]))
+	return x, n
+}
+
+func (m metadataID3v2) Track() (int, int) {
+	return parseXofN(m.getString(frames.Name("track", m.Format())))
+}
+
+func (m metadataID3v2) Disc() (int, int) {
+	return parseXofN(m.getString(frames.Name("disc", m.Format())))
+}
+
+func (m metadataID3v2) Lyrics() string {
+	t, ok := m.frames[frames.Name("lyrics", m.Format())]
+	if !ok {
+		return ""
+	}
+	return t.(*Comm).Text
+}
+
+func (m metadataID3v2) Comment() string {
+	t, ok := m.frames[frames.Name("comment", m.Format())]
+	if !ok {
+		return ""
+	}
+	// id3v23 has Text, id3v24 has Description
+	if t.(*Comm).Description == "" {
+		return trimString(t.(*Comm).Text)
+	}
+	return trimString(t.(*Comm).Description)
+}
+
+func (m metadataID3v2) Picture() *Picture {
+	v, ok := m.frames[frames.Name("picture", m.Format())]
+	if !ok {
+		return nil
+	}
+	return v.(*Picture)
+}

vendor/github.com/dhowden/tag/mp4.go

@@ -0,0 +1,379 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+var atomTypes = map[int]string{
+	0:  "implicit", // automatic based on atom name
+	1:  "text",
+	13: "jpeg",
+	14: "png",
+	21: "uint8",
+}
+
+// NB: atoms does not include "----", this is handled separately
+var atoms = atomNames(map[string]string{
+	"\xa9alb": "album",
+	"\xa9art": "artist",
+	"\xa9ART": "artist",
+	"aART":    "album_artist",
+	"\xa9day": "year",
+	"\xa9nam": "title",
+	"\xa9gen": "genre",
+	"trkn":    "track",
+	"\xa9wrt": "composer",
+	"\xa9too": "encoder",
+	"cprt":    "copyright",
+	"covr":    "picture",
+	"\xa9grp": "grouping",
+	"keyw":    "keyword",
+	"\xa9lyr": "lyrics",
+	"\xa9cmt": "comment",
+	"tmpo":    "tempo",
+	"cpil":    "compilation",
+	"disk":    "disc",
+})
+
+var means = map[string]bool{
+	"com.apple.iTunes":          true,
+	"com.mixedinkey.mixedinkey": true,
+	"com.serato.dj":             true,
+}
+
+// Detect PNG image if "implicit" class is used
+var pngHeader = []byte{137, 80, 78, 71, 13, 10, 26, 10}
+
+type atomNames map[string]string
+
+func (f atomNames) Name(n string) []string {
+	res := make([]string, 1)
+	for k, v := range f {
+		if v == n {
+			res = append(res, k)
+		}
+	}
+	return res
+}
+
+// metadataMP4 is the implementation of Metadata for MP4 tag (atom) data.
+type metadataMP4 struct {
+	fileType FileType
+	data     map[string]interface{}
+}
+
+// ReadAtoms reads MP4 metadata atoms from the io.ReadSeeker into a Metadata, returning
+// non-nil error if there was a problem.
+func ReadAtoms(r io.ReadSeeker) (Metadata, error) {
+	m := metadataMP4{
+		data:     make(map[string]interface{}),
+		fileType: UnknownFileType,
+	}
+	err := m.readAtoms(r)
+	return m, err
+}
+
+func (m metadataMP4) readAtoms(r io.ReadSeeker) error {
+	for {
+		name, size, err := readAtomHeader(r)
+		if err != nil {
+			if err == io.EOF {
+				return 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 m.readAtoms(r)
+		}
+
+		_, ok := atoms[name]
+		var data []string
+		if name == "----" {
+			name, data, err = readCustomAtom(r, size)
+			if err != nil {
+				return err
+			}
+
+			if name != "----" {
+				ok = true
+				size = 0 // already read data
+			}
+		}
+
+		if !ok {
+			_, err := r.Seek(int64(size-8), io.SeekCurrent)
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		err = m.readAtomData(r, name, size-8, data)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (m metadataMP4) readAtomData(r io.ReadSeeker, name string, size uint32, processedData []string) error {
+	var b []byte
+	var err error
+	var contentType string
+	if len(processedData) > 0 {
+		b = []byte(strings.Join(processedData, ";")) // add delimiter if multiple data fields
+		contentType = "text"
+	} else {
+		// read the data
+		b, err = readBytes(r, uint(size))
+		if err != nil {
+			return err
+		}
+		if len(b) < 8 {
+			return fmt.Errorf("invalid encoding: expected at least %d bytes, got %d", 8, len(b))
+		}
+
+		// "data" + size (4 bytes each)
+		b = b[8:]
+
+		if len(b) < 4 {
+			return fmt.Errorf("invalid encoding: expected at least %d bytes, for class, got %d", 4, len(b))
+		}
+		class := getInt(b[1:4])
+		var ok bool
+		contentType, ok = atomTypes[class]
+		if !ok {
+			return fmt.Errorf("invalid content type: %v (%x) (%x)", class, b[1:4], b)
+		}
+
+		// 4: atom version (1 byte) + atom flags (3 bytes)
+		// 4: NULL (usually locale indicator)
+		if len(b) < 8 {
+			return fmt.Errorf("invalid encoding: expected at least %d bytes, for atom version and flags, got %d", 8, len(b))
+		}
+		b = b[8:]
+	}
+
+	if name == "trkn" || name == "disk" {
+		if len(b) < 6 {
+			return fmt.Errorf("invalid encoding: expected at least %d bytes, for track and disk numbers, got %d", 6, len(b))
+		}
+
+		m.data[name] = int(b[3])
+		m.data[name+"_count"] = int(b[5])
+		return nil
+	}
+
+	if contentType == "implicit" {
+		if name == "covr" {
+			if bytes.HasPrefix(b, pngHeader) {
+				contentType = "png"
+			}
+			// TODO(dhowden): Detect JPEG formats too (harder).
+		}
+	}
+
+	var data interface{}
+	switch contentType {
+	case "implicit":
+		if _, ok := atoms[name]; ok {
+			return fmt.Errorf("unhandled implicit content type for required atom: %q", name)
+		}
+		return nil
+
+	case "text":
+		data = string(b)
+
+	case "uint8":
+		if len(b) < 1 {
+			return fmt.Errorf("invalid encoding: expected at least %d bytes, for integer tag data, got %d", 1, len(b))
+		}
+		data = getInt(b[:1])
+
+	case "jpeg", "png":
+		data = &Picture{
+			Ext:      contentType,
+			MIMEType: "image/" + contentType,
+			Data:     b,
+		}
+	}
+	m.data[name] = data
+
+	return nil
+}
+
+func readAtomHeader(r io.ReadSeeker) (name string, size uint32, err error) {
+	err = binary.Read(r, binary.BigEndian, &size)
+	if err != nil {
+		return
+	}
+	name, err = readString(r, 4)
+	return
+}
+
+// Generic atom.
+// Should have 3 sub atoms : mean, name and data.
+// We check that mean is "com.apple.iTunes" or others and we use the subname as
+// the name, and move to the data atom.
+// Data atom could have multiple data values, each with a header.
+// If anything goes wrong, we jump at the end of the "----" atom.
+func readCustomAtom(r io.ReadSeeker, size uint32) (_ string, data []string, _ error) {
+	subNames := make(map[string]string)
+
+	for size > 8 {
+		subName, subSize, err := readAtomHeader(r)
+		if err != nil {
+			return "", nil, err
+		}
+
+		// Remove the size of the atom from the size counter
+		if size >= subSize {
+			size -= subSize
+		} else {
+			return "", nil, errors.New("--- invalid size")
+		}
+
+		b, err := readBytes(r, uint(subSize-8))
+		if err != nil {
+			return "", nil, err
+		}
+
+		if len(b) < 4 {
+			return "", nil, fmt.Errorf("invalid encoding: expected at least %d bytes, got %d", 4, len(b))
+		}
+		switch subName {
+		case "mean", "name":
+			subNames[subName] = string(b[4:])
+		case "data":
+			data = append(data, string(b[4:]))
+		}
+	}
+
+	// there should remain only the header size
+	if size != 8 {
+		err := errors.New("---- atom out of bounds")
+		return "", nil, err
+	}
+
+	if !means[subNames["mean"]] || subNames["name"] == "" || len(data) == 0 {
+		return "----", nil, nil
+	}
+
+	return subNames["name"], data, nil
+}
+
+func (metadataMP4) Format() Format       { return MP4 }
+func (m metadataMP4) FileType() FileType { return m.fileType }
+
+func (m metadataMP4) Raw() map[string]interface{} { return m.data }
+
+func (m metadataMP4) getString(n []string) string {
+	for _, k := range n {
+		if x, ok := m.data[k]; ok {
+			return x.(string)
+		}
+	}
+	return ""
+}
+
+func (m metadataMP4) getInt(n []string) int {
+	for _, k := range n {
+		if x, ok := m.data[k]; ok {
+			return x.(int)
+		}
+	}
+	return 0
+}
+
+func (m metadataMP4) Title() string {
+	return m.getString(atoms.Name("title"))
+}
+
+func (m metadataMP4) Artist() string {
+	return m.getString(atoms.Name("artist"))
+}
+
+func (m metadataMP4) Album() string {
+	return m.getString(atoms.Name("album"))
+}
+
+func (m metadataMP4) AlbumArtist() string {
+	return m.getString(atoms.Name("album_artist"))
+}
+
+func (m metadataMP4) Composer() string {
+	return m.getString(atoms.Name("composer"))
+}
+
+func (m metadataMP4) Genre() string {
+	return m.getString(atoms.Name("genre"))
+}
+
+func (m metadataMP4) Year() int {
+	date := m.getString(atoms.Name("year"))
+	if len(date) >= 4 {
+		year, _ := strconv.Atoi(date[:4])
+		return year
+	}
+	return 0
+}
+
+func (m metadataMP4) Track() (int, int) {
+	x := m.getInt([]string{"trkn"})
+	if n, ok := m.data["trkn_count"]; ok {
+		return x, n.(int)
+	}
+	return x, 0
+}
+
+func (m metadataMP4) Disc() (int, int) {
+	x := m.getInt([]string{"disk"})
+	if n, ok := m.data["disk_count"]; ok {
+		return x, n.(int)
+	}
+	return x, 0
+}
+
+func (m metadataMP4) Lyrics() string {
+	t, ok := m.data["\xa9lyr"]
+	if !ok {
+		return ""
+	}
+	return t.(string)
+}
+
+func (m metadataMP4) Comment() string {
+	t, ok := m.data["\xa9cmt"]
+	if !ok {
+		return ""
+	}
+	return t.(string)
+}
+
+func (m metadataMP4) Picture() *Picture {
+	v, ok := m.data["covr"]
+	if !ok {
+		return nil
+	}
+	p, _ := v.(*Picture)
+	return p
+}

vendor/github.com/dhowden/tag/ogg.go

@@ -0,0 +1,174 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+)
+
+var (
+	vorbisCommentPrefix = []byte("\x03vorbis")
+	opusTagsPrefix      = []byte("OpusTags")
+)
+
+var oggCRC32Poly04c11db7 = oggCRCTable(0x04c11db7)
+
+type crc32Table [256]uint32
+
+func oggCRCTable(poly uint32) *crc32Table {
+	var t crc32Table
+
+	for i := 0; i < 256; i++ {
+		crc := uint32(i) << 24
+		for j := 0; j < 8; j++ {
+			if crc&0x80000000 != 0 {
+				crc = (crc << 1) ^ poly
+			} else {
+				crc <<= 1
+			}
+		}
+		t[i] = crc
+	}
+
+	return &t
+}
+
+func oggCRCUpdate(crc uint32, tab *crc32Table, p []byte) uint32 {
+	for _, v := range p {
+		crc = (crc << 8) ^ tab[byte(crc>>24)^v]
+	}
+	return crc
+}
+
+type oggPageHeader struct {
+	Magic           [4]byte // "OggS"
+	Version         uint8
+	Flags           uint8
+	GranulePosition uint64
+	SerialNumber    uint32
+	SequenceNumber  uint32
+	CRC             uint32
+	Segments        uint8
+}
+
+type oggDemuxer struct {
+	packetBufs map[uint32]*bytes.Buffer
+}
+
+// Read ogg packets, can return empty slice of packets and nil err
+// if more data is needed
+func (o *oggDemuxer) Read(r io.Reader) ([][]byte, error) {
+	headerBuf := &bytes.Buffer{}
+	var oh oggPageHeader
+	if err := binary.Read(io.TeeReader(r, headerBuf), binary.LittleEndian, &oh); err != nil {
+		return nil, err
+	}
+
+	if bytes.Compare(oh.Magic[:], []byte("OggS")) != 0 {
+		// TODO: seek for syncword?
+		return nil, errors.New("expected 'OggS'")
+	}
+
+	segmentTable := make([]byte, oh.Segments)
+	if _, err := io.ReadFull(r, segmentTable); err != nil {
+		return nil, err
+	}
+	var segmentsSize int64
+	for _, s := range segmentTable {
+		segmentsSize += int64(s)
+	}
+	segmentsData := make([]byte, segmentsSize)
+	if _, err := io.ReadFull(r, segmentsData); err != nil {
+		return nil, err
+	}
+
+	headerBytes := headerBuf.Bytes()
+	// reset CRC to zero in header before checksum
+	headerBytes[22] = 0
+	headerBytes[23] = 0
+	headerBytes[24] = 0
+	headerBytes[25] = 0
+	crc := oggCRCUpdate(0, oggCRC32Poly04c11db7, headerBytes)
+	crc = oggCRCUpdate(crc, oggCRC32Poly04c11db7, segmentTable)
+	crc = oggCRCUpdate(crc, oggCRC32Poly04c11db7, segmentsData)
+	if crc != oh.CRC {
+		return nil, fmt.Errorf("expected crc %x != %x", oh.CRC, crc)
+	}
+
+	if o.packetBufs == nil {
+		o.packetBufs = map[uint32]*bytes.Buffer{}
+	}
+
+	var packetBuf *bytes.Buffer
+	continued := oh.Flags&0x1 != 0
+	if continued {
+		if b, ok := o.packetBufs[oh.SerialNumber]; ok {
+			packetBuf = b
+		} else {
+			return nil, fmt.Errorf("could not find continued packet %d", oh.SerialNumber)
+		}
+	} else {
+		packetBuf = &bytes.Buffer{}
+	}
+
+	var packets [][]byte
+	var p int
+	for _, s := range segmentTable {
+		packetBuf.Write(segmentsData[p : p+int(s)])
+		if s < 255 {
+			packets = append(packets, packetBuf.Bytes())
+			packetBuf = &bytes.Buffer{}
+		}
+		p += int(s)
+	}
+
+	o.packetBufs[oh.SerialNumber] = packetBuf
+
+	return packets, nil
+}
+
+// ReadOGGTags reads OGG metadata from the io.ReadSeeker, returning the resulting
+// metadata in a Metadata implementation, or non-nil error if there was a problem.
+// See http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html
+// and http://www.xiph.org/ogg/doc/framing.html for details.
+// For Opus see https://tools.ietf.org/html/rfc7845
+func ReadOGGTags(r io.Reader) (Metadata, error) {
+	od := &oggDemuxer{}
+	for {
+		bs, err := od.Read(r)
+		if err != nil {
+			return nil, err
+		}
+
+		for _, b := range bs {
+			switch {
+			case bytes.HasPrefix(b, vorbisCommentPrefix):
+				m := &metadataOGG{
+					newMetadataVorbis(),
+				}
+				err = m.readVorbisComment(bytes.NewReader(b[len(vorbisCommentPrefix):]))
+				return m, err
+			case bytes.HasPrefix(b, opusTagsPrefix):
+				m := &metadataOGG{
+					newMetadataVorbis(),
+				}
+				err = m.readVorbisComment(bytes.NewReader(b[len(opusTagsPrefix):]))
+				return m, err
+			}
+		}
+	}
+}
+
+type metadataOGG struct {
+	*metadataVorbis
+}
+
+func (m *metadataOGG) FileType() FileType {
+	return OGG
+}

vendor/github.com/dhowden/tag/sum.go

@@ -0,0 +1,219 @@
+package tag
+
+import (
+	"crypto/sha1"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"hash"
+	"io"
+)
+
+// 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
+	}
+
+	_, err = r.Seek(-11, io.SeekCurrent)
+	if err != nil {
+		return "", fmt.Errorf("could not seek back to original position: %v", err)
+	}
+
+	switch {
+	case string(b[0:4]) == "fLaC":
+		return SumFLAC(r)
+
+	case string(b[4:11]) == "ftypM4A":
+		return SumAtoms(r)
+
+	case 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 content from the reader (until EOF).
+func SumAll(r io.ReadSeeker) (string, error) {
+	h := sha1.New()
+	_, err := io.Copy(h, r)
+	if err != nil {
+		return "", nil
+	}
+	return hashSum(h), 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) {
+	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 := r.Seek(4, io.SeekCurrent)
+			if err != nil {
+				return "", err
+			}
+			fallthrough
+
+		case "moov", "udta", "ilst":
+			continue
+
+		case "mdat": // stop when we get to the data
+			h := sha1.New()
+			_, err := io.CopyN(h, r, int64(size-8))
+			if err != nil {
+				return "", fmt.Errorf("error reading audio data: %v", err)
+			}
+			return hashSum(h), nil
+		}
+
+		_, err = r.Seek(int64(size-8), io.SeekCurrent)
+		if err != nil {
+			return "", fmt.Errorf("error reading '%v' tag: %v", name, err)
+		}
+	}
+}
+
+func sizeToEndOffset(r io.ReadSeeker, offset int64) (int64, error) {
+	n, err := r.Seek(-128, io.SeekEnd)
+	if err != nil {
+		return 0, fmt.Errorf("error seeking end offset (%d bytes): %v", offset, err)
+	}
+
+	_, err = r.Seek(-n, io.SeekCurrent)
+	if err != nil {
+		return 0, fmt.Errorf("error seeking back to original position: %v", err)
+	}
+	return n, nil
+}
+
+// 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) {
+	n, err := sizeToEndOffset(r, 128)
+	if err != nil {
+		return "", fmt.Errorf("error determining read size to ID3v1 header: %v", err)
+	}
+
+	// TODO: improve this check???
+	if n <= 0 {
+		return "", fmt.Errorf("file size must be greater than 128 bytes (ID3v1 header size) for MP3")
+	}
+
+	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) {
+	header, _, err := readID3v2Header(r)
+	if err != nil {
+		return "", fmt.Errorf("error reading ID3v2 header: %v", err)
+	}
+
+	_, err = r.Seek(int64(header.Size), io.SeekCurrent)
+	if err != nil {
+		return "", fmt.Errorf("error seeking to end of ID3V2 header: %v", err)
+	}
+
+	n, err := sizeToEndOffset(r, 128)
+	if err != nil {
+		return "", fmt.Errorf("error determining read size to ID3v1 header: %v", err)
+	}
+
+	// TODO: remove this check?????
+	if n < 0 {
+		return "", fmt.Errorf("file size must be greater than 128 bytes for MP3: %v bytes", n)
+	}
+
+	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
+}
+
+// SumFLAC costructs a checksum of the FLAC audio file data provided by the io.ReadSeeker (ignores
+// metadata fields).
+func SumFLAC(r io.ReadSeeker) (string, error) {
+	flac, err := readString(r, 4)
+	if err != nil {
+		return "", err
+	}
+	if flac != "fLaC" {
+		return "", errors.New("expected 'fLaC'")
+	}
+
+	for {
+		last, err := skipFLACMetadataBlock(r)
+		if err != nil {
+			return "", err
+		}
+
+		if last {
+			break
+		}
+	}
+
+	h := sha1.New()
+	_, err = io.Copy(h, r)
+	if err != nil {
+		return "", fmt.Errorf("error reading data bytes from FLAC: %v", err)
+	}
+	return hashSum(h), nil
+}
+
+func skipFLACMetadataBlock(r io.ReadSeeker) (last bool, err error) {
+	blockHeader, err := readBytes(r, 1)
+	if err != nil {
+		return
+	}
+
+	if getBit(blockHeader[0], 7) {
+		blockHeader[0] ^= (1 << 7)
+		last = true
+	}
+
+	blockLen, err := readInt(r, 3)
+	if err != nil {
+		return
+	}
+
+	_, err = r.Seek(int64(blockLen), io.SeekCurrent)
+	return
+}
+
+func hashSum(h hash.Hash) string {
+	return fmt.Sprintf("%x", h.Sum([]byte{}))
+}

vendor/github.com/dhowden/tag/tag.go

@@ -0,0 +1,147 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tag provides MP3 (ID3: v1, 2.2, 2.3 and 2.4), MP4, FLAC and OGG metadata detection,
+// 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).
+package tag
+
+import (
+	"errors"
+	"fmt"
+	"io"
+)
+
+// ErrNoTagsFound is the error returned by ReadFrom when the metadata format
+// cannot be identified.
+var ErrNoTagsFound = errors.New("no tags found")
+
+// ReadFrom detects and parses audio file metadata tags (currently supports ID3v1,2.{2,3,4}, MP4, FLAC/OGG).
+// Returns non-nil error if the format of the given data could not be determined, or if there was a problem
+// parsing the data.
+func ReadFrom(r io.ReadSeeker) (Metadata, error) {
+	b, err := readBytes(r, 11)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = r.Seek(-11, io.SeekCurrent)
+	if err != nil {
+		return nil, fmt.Errorf("could not seek back to original position: %v", err)
+	}
+
+	switch {
+	case string(b[0:4]) == "fLaC":
+		return ReadFLACTags(r)
+
+	case string(b[0:4]) == "OggS":
+		return ReadOGGTags(r)
+
+	case string(b[4:8]) == "ftyp":
+		return ReadAtoms(r)
+
+	case string(b[0:3]) == "ID3":
+		return ReadID3v2Tags(r)
+
+	case string(b[0:4]) == "DSD ":
+		return ReadDSFTags(r)
+	}
+
+	m, err := ReadID3v1Tags(r)
+	if err != nil {
+		if err == ErrNotID3v1 {
+			err = ErrNoTagsFound
+		}
+		return nil, err
+	}
+	return m, nil
+}
+
+// Format is an enumeration of metadata types supported by this package.
+type Format string
+
+// Supported tag formats.
+const (
+	UnknownFormat Format = ""        // Unknown Format.
+	ID3v1         Format = "ID3v1"   // ID3v1 tag format.
+	ID3v2_2       Format = "ID3v2.2" // ID3v2.2 tag format.
+	ID3v2_3       Format = "ID3v2.3" // ID3v2.3 tag format (most common).
+	ID3v2_4       Format = "ID3v2.4" // ID3v2.4 tag format.
+	MP4           Format = "MP4"     // MP4 tag (atom) format (see http://www.ftyps.com/ for a full file type list)
+	VORBIS        Format = "VORBIS"  // Vorbis Comment tag format.
+)
+
+// FileType is an enumeration of the audio file types supported by this package, in particular
+// there are audio file types which share metadata formats, and this type is used to distinguish
+// between them.
+type FileType string
+
+// Supported file types.
+const (
+	UnknownFileType FileType = ""     // Unknown FileType.
+	MP3             FileType = "MP3"  // MP3 file
+	M4A             FileType = "M4A"  // M4A file Apple iTunes (ACC) Audio
+	M4B             FileType = "M4B"  // M4A file Apple iTunes (ACC) Audio Book
+	M4P             FileType = "M4P"  // M4A file Apple iTunes (ACC) AES Protected Audio
+	ALAC            FileType = "ALAC" // Apple Lossless file FIXME: actually detect this
+	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
+)
+
+// Metadata is an interface which is used to describe metadata retrieved by this package.
+type Metadata interface {
+	// Format returns the metadata Format used to encode the data.
+	Format() Format
+
+	// FileType returns the file type of the audio file.
+	FileType() FileType
+
+	// Title returns the title of the track.
+	Title() string
+
+	// Album returns the album name of the track.
+	Album() string
+
+	// Artist returns the artist name of the track.
+	Artist() string
+
+	// AlbumArtist returns the album artist name of the track.
+	AlbumArtist() string
+
+	// Composer returns the composer of the track.
+	Composer() string
+
+	// Year returns the year of the track.
+	Year() int
+
+	// Genre returns the genre of the track.
+	Genre() string
+
+	// Track returns the track number and total tracks, or zero values if unavailable.
+	Track() (int, int)
+
+	// Disc returns the disc number and total discs, or zero values if unavailable.
+	Disc() (int, int)
+
+	// Picture returns a picture, or nil if not available.
+	Picture() *Picture
+
+	// Lyrics returns the lyrics, or an empty string if unavailable.
+	Lyrics() string
+
+	// Comment returns the comment, or an empty string if unavailable.
+	Comment() string
+
+	// Raw returns the raw mapping of retrieved tag names and associated values.
+	// NB: tag/atom names are not standardised between formats.
+	Raw() map[string]interface{}
+}

vendor/github.com/dhowden/tag/util.go

@@ -0,0 +1,102 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+)
+
+func getBit(b byte, n uint) bool {
+	x := byte(1 << n)
+	return (b & x) == x
+}
+
+func get7BitChunkedInt(b []byte) int {
+	var n int
+	for _, x := range b {
+		n = n << 7
+		n |= int(x)
+	}
+	return n
+}
+
+func getInt(b []byte) int {
+	var n int
+	for _, x := range b {
+		n = n << 8
+		n |= int(x)
+	}
+	return n
+}
+
+func readUint64LittleEndian(r io.Reader) (uint64, error) {
+	b, err := readBytes(r, 8)
+	if err != nil {
+		return 0, err
+	}
+	return binary.LittleEndian.Uint64(b), nil
+}
+
+// readBytesMaxUpfront is the max up-front allocation allowed
+const readBytesMaxUpfront = 10 << 20 // 10MB
+
+func readBytes(r io.Reader, n uint) ([]byte, error) {
+	if n > readBytesMaxUpfront {
+		b := &bytes.Buffer{}
+		if _, err := io.CopyN(b, r, int64(n)); err != nil {
+			return nil, err
+		}
+		return b.Bytes(), nil
+	}
+
+	b := make([]byte, n)
+	_, err := io.ReadFull(r, b)
+	if err != nil {
+		return nil, err
+	}
+	return b, nil
+}
+
+func readString(r io.Reader, n uint) (string, error) {
+	b, err := readBytes(r, n)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}
+
+func readUint(r io.Reader, n uint) (uint, error) {
+	x, err := readInt(r, n)
+	if err != nil {
+		return 0, err
+	}
+	return uint(x), nil
+}
+
+func readInt(r io.Reader, n uint) (int, error) {
+	b, err := readBytes(r, n)
+	if err != nil {
+		return 0, err
+	}
+	return getInt(b), nil
+}
+
+func read7BitChunkedUint(r io.Reader, n uint) (uint, error) {
+	b, err := readBytes(r, n)
+	if err != nil {
+		return 0, err
+	}
+	return uint(get7BitChunkedInt(b)), nil
+}
+
+func readUint32LittleEndian(r io.Reader) (uint32, error) {
+	b, err := readBytes(r, 4)
+	if err != nil {
+		return 0, err
+	}
+	return binary.LittleEndian.Uint32(b), nil
+}

vendor/github.com/dhowden/tag/vorbis.go

@@ -0,0 +1,266 @@
+// Copyright 2015, David Howden
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tag
+
+import (
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func newMetadataVorbis() *metadataVorbis {
+	return &metadataVorbis{
+		c: make(map[string]string),
+	}
+}
+
+type metadataVorbis struct {
+	c map[string]string // the vorbis comments
+	p *Picture
+}
+
+func (m *metadataVorbis) readVorbisComment(r io.Reader) error {
+	vendorLen, err := readUint32LittleEndian(r)
+	if err != nil {
+		return err
+	}
+
+	vendor, err := readString(r, uint(vendorLen))
+	if err != nil {
+		return err
+	}
+	m.c["vendor"] = vendor
+
+	commentsLen, err := readUint32LittleEndian(r)
+	if err != nil {
+		return err
+	}
+
+	for i := uint32(0); i < commentsLen; i++ {
+		l, err := readUint32LittleEndian(r)
+		if err != nil {
+			return err
+		}
+		s, err := readString(r, uint(l))
+		if err != nil {
+			return err
+		}
+		k, v, err := parseComment(s)
+		if err != nil {
+			return err
+		}
+		m.c[strings.ToLower(k)] = v
+	}
+
+	if b64data, ok := m.c["metadata_block_picture"]; ok {
+		data, err := base64.StdEncoding.DecodeString(b64data)
+		if err != nil {
+			return err
+		}
+		m.readPictureBlock(bytes.NewReader(data))
+	}
+
+	return nil
+}
+
+func (m *metadataVorbis) readPictureBlock(r io.Reader) error {
+	b, err := readInt(r, 4)
+	if err != nil {
+		return err
+	}
+	pictureType, ok := pictureTypes[byte(b)]
+	if !ok {
+		return fmt.Errorf("invalid picture type: %v", b)
+	}
+	mimeLen, err := readUint(r, 4)
+	if err != nil {
+		return err
+	}
+	mime, err := readString(r, mimeLen)
+	if err != nil {
+		return err
+	}
+
+	ext := ""
+	switch mime {
+	case "image/jpeg":
+		ext = "jpg"
+	case "image/png":
+		ext = "png"
+	case "image/gif":
+		ext = "gif"
+	}
+
+	descLen, err := readUint(r, 4)
+	if err != nil {
+		return err
+	}
+	desc, err := readString(r, descLen)
+	if err != nil {
+		return err
+	}
+
+	// We skip width <32>, height <32>, colorDepth <32>, coloresUsed <32>
+	_, err = readInt(r, 4) // width
+	if err != nil {
+		return err
+	}
+	_, err = readInt(r, 4) // height
+	if err != nil {
+		return err
+	}
+	_, err = readInt(r, 4) // color depth
+	if err != nil {
+		return err
+	}
+	_, err = readInt(r, 4) // colors used
+	if err != nil {
+		return err
+	}
+
+	dataLen, err := readInt(r, 4)
+	if err != nil {
+		return err
+	}
+	data := make([]byte, dataLen)
+	_, err = io.ReadFull(r, data)
+	if err != nil {
+		return err
+	}
+
+	m.p = &Picture{
+		Ext:         ext,
+		MIMEType:    mime,
+		Type:        pictureType,
+		Description: desc,
+		Data:        data,
+	}
+	return nil
+}
+
+func parseComment(c string) (k, v string, err error) {
+	kv := strings.SplitN(c, "=", 2)
+	if len(kv) != 2 {
+		err = errors.New("vorbis comment must contain '='")
+		return
+	}
+	k = kv[0]
+	v = kv[1]
+	return
+}
+
+func (m *metadataVorbis) Format() Format {
+	return VORBIS
+}
+
+func (m *metadataVorbis) Raw() map[string]interface{} {
+	raw := make(map[string]interface{}, len(m.c))
+	for k, v := range m.c {
+		raw[k] = v
+	}
+	return raw
+}
+
+func (m *metadataVorbis) Title() string {
+	return m.c["title"]
+}
+
+func (m *metadataVorbis) Artist() string {
+	// ARTIST
+	// The artist generally considered responsible for the work. In popular music
+	// this is usually the performing band or singer. For classical music it would
+	// be the composer. For an audio book it would be the author of the original text.
+	return m.c["artist"]
+}
+
+func (m *metadataVorbis) Album() string {
+	return m.c["album"]
+}
+
+func (m *metadataVorbis) AlbumArtist() string {
+	// This field isn't actually included in the standard, though
+	// it is commonly assigned to albumartist.
+	return m.c["albumartist"]
+}
+
+func (m *metadataVorbis) Composer() string {
+	if m.c["composer"] != "" {
+		return m.c["composer"]
+	}
+	// PERFORMER
+	// The artist(s) who performed the work. In classical music this would be the
+	// conductor, orchestra, soloists. In an audio book it would be the actor who
+	// did the reading. In popular music this is typically the same as the ARTIST
+	// and is omitted.
+	if m.c["performer"] != "" {
+		return m.c["performer"]
+	}
+	return m.c["artist"]
+}
+
+func (m *metadataVorbis) Genre() string {
+	return m.c["genre"]
+}
+
+func (m *metadataVorbis) Year() int {
+	var dateFormat string
+
+	// The date need to follow the international standard https://en.wikipedia.org/wiki/ISO_8601
+	// and obviously the VorbisComment standard https://wiki.xiph.org/VorbisComment#Date_and_time
+	switch len(m.c["date"]) {
+	case 0:
+		// Fallback on year tag as some files use that.
+		if len(m.c["year"]) != 0 {
+			year, err := strconv.Atoi(m.c["year"])
+			if err == nil {
+				return year
+			}
+		}
+		return 0
+	case 4:
+		dateFormat = "2006"
+	case 7:
+		dateFormat = "2006-01"
+	case 10:
+		dateFormat = "2006-01-02"
+	}
+
+	t, _ := time.Parse(dateFormat, m.c["date"])
+	return t.Year()
+}
+
+func (m *metadataVorbis) Track() (int, int) {
+	x, _ := strconv.Atoi(m.c["tracknumber"])
+	// https://wiki.xiph.org/Field_names
+	n, _ := strconv.Atoi(m.c["tracktotal"])
+	return x, n
+}
+
+func (m *metadataVorbis) Disc() (int, int) {
+	// https://wiki.xiph.org/Field_names
+	x, _ := strconv.Atoi(m.c["discnumber"])
+	n, _ := strconv.Atoi(m.c["disctotal"])
+	return x, n
+}
+
+func (m *metadataVorbis) Lyrics() string {
+	return m.c["lyrics"]
+}
+
+func (m *metadataVorbis) Comment() string {
+	if m.c["comment"] != "" {
+		return m.c["comment"]
+	}
+	return m.c["description"]
+}
+
+func (m *metadataVorbis) Picture() *Picture {
+	return m.p
+}

vendor/modules.txt

@@ -0,0 +1,3 @@
+# github.com/dhowden/tag v0.0.0-20240417053706-3d75831295e8
+## explicit; go 1.20
+github.com/dhowden/tag