Streamer from bytes reader has a length of 0 #123

abhobe · 2021-06-01T22:27:07Z

I'm trying to read an audio file through a reader from a []byte array, but when I do this, the length of the output stream is 0. However, using the traditional method of os.Open(), the length is 9589248. Both methods can play the audio, but I can't use .Seek() when using the byte array. I'm not sure what's wrong, any help would be appreciated.

package main

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"os"

	"github.com/faiface/beep/mp3"
)

func main() {
	file, err := ioutil.ReadFile("audio.mp3")
	if err != nil {
		panic(err)
	}

	file2, err := os.Open("audio.mp3")
	if err != nil {
		panic(err)
	}

	fileString, _, _ := mp3.Decode(ioutil.NopCloser(bytes.NewReader(file))) // Outputs 0
	fileString2, _, _ := mp3.Decode(file2) // Outputs 9589248

	fmt.Println(fileString.Len())
	fmt.Println(fileString2.Len())
}

The text was updated successfully, but these errors were encountered:

Deng-Xian-Sheng · 2022-06-04T18:00:42Z

I think something is accidentally lost in the process of converting []byte to io.ReadCloser, or os.File is the most appropriate for mp3.Decode, so I recommend converting []byte to os.File; And I succeeded, solved the problem, and got the music length.
I try to use os.NewFile(0, "").Write() but the console output is garbled, and the sound cannot be played.
So I wrote this myself:

// Package byteToFile
// []byte to fs.file, reference embed
package byteToFile

import (
	"io"
	"io/fs"
	"reflect"
	"time"
)

// A file is a single file in the FS.
// It implements fs.FileInfo and fs.DirEntry.
type file struct {
	name string
	data string
	hash [16]byte // truncated SHA256 hash
}

func (f *file) Name() string               { return f.name }
func (f *file) Size() int64                { return int64(len(f.data)) }
func (f *file) ModTime() time.Time         { return time.Time{} }
func (f *file) IsDir() bool                { return false }
func (f *file) Sys() any                   { return nil }
func (f *file) Type() fs.FileMode          { return f.Mode().Type() }
func (f *file) Info() (fs.FileInfo, error) { return f, nil }

func (f *file) Mode() fs.FileMode {
	if f.IsDir() {
		return fs.ModeDir | 0555
	}
	return 0444
}

// An openFile is a regular file open for reading.
type openFile struct {
	f      *file // the file itself
	offset int64 // current read offset
}

func (f *openFile) Close() error               { return nil }
func (f *openFile) Stat() (fs.FileInfo, error) { return f.f, nil }

// Read reads up to len(b) bytes from the File and stores them in b.
// It returns the number of bytes read and any error encountered.
// At end of file, Read returns 0, io.EOF.
func (f *openFile) Read(b []byte) (int, error) {
	if f.offset >= int64(len(f.f.data)) {
		return 0, io.EOF
	}
	if f.offset < 0 {
		return 0, &fs.PathError{Op: "read", Path: f.f.name, Err: fs.ErrInvalid}
	}
	n := copy(b, f.f.data[f.offset:])
	f.offset += int64(n)
	return n, nil
}

var (
	_ io.Seeker   = (*openFile)(nil)
	_ fs.FileInfo = (*file)(nil)
)

func (f *openFile) Seek(offset int64, whence int) (int64, error) {
	switch whence {
	case 0:
		// offset += 0
	case 1:
		offset += f.offset
	case 2:
		offset += int64(len(f.f.data))
	}
	if offset < 0 || offset > int64(len(f.f.data)) {
		return 0, &fs.PathError{Op: "seek", Path: f.f.name, Err: fs.ErrInvalid}
	}
	f.offset = offset
	return offset, nil
}

func (f *openFile) Write(b []byte) (int, error) {
	if reflect.ValueOf(f).IsNil() {
		return 0, &fs.PathError{Op: "write", Path: f.f.name, Err: fs.ErrInvalid}
	}
	f.f.data += string(b)
	return len(b), nil
}

func New() *openFile {
	return &openFile{
		f:      &file{},
		offset: 0,
	}
}

It works like this:

package main

import (
	"fmt"
	"demo/byteToFile"
)

func main(){
	data := []byte("I like 邓文怡")
	object := byteToFile.New()
	_,err := object.Write(data)
	if err != nil{
		panic(err)
	}
	read := make([]byte,len(data))
	_,err = object.Read(read)
	if err != nil{
		panic(err)
	}
	fmt.Println(string(read))
}

Hope it can help you!
I like beep it's good!

ivcz · 2023-06-06T06:01:15Z

In order for Len and Seek methods to work you need to implement io.Seeker on the struct you pass into mp3.Decode, which NopCloser does not

ivcz · 2023-06-06T23:03:24Z

Tested it, and implementing io.Seeker wont actually help, because beep uses go-mp3 package, and it sets the length when you call mp3.Decode, which means it will only be the size of the buffer at that time.

Deng-Xian-Sheng · 2023-06-09T09:10:31Z

我认为在将[]字节转换为io.ReadCloser或os.File最适合mp3的过程中，意外丢失了一些东西。解码，所以我建议将[]字节转换为os.File；我成功了，解决了问题，并得到了音乐长度。我尝试使用os.NewFile(0, "").Write()，但控制台输出混乱，无法播放声音。所以我自己写了这个：

// Package byteToFile
// []byte to fs.file, reference embed
package byteToFile

import (
	"io"
	"io/fs"
	"reflect"
	"time"
)

// A file is a single file in the FS.
// It implements fs.FileInfo and fs.DirEntry.
type file struct {
	name string
	data string
	hash [16]byte // truncated SHA256 hash
}

func (f *file) Name() string               { return f.name }
func (f *file) Size() int64                { return int64(len(f.data)) }
func (f *file) ModTime() time.Time         { return time.Time{} }
func (f *file) IsDir() bool                { return false }
func (f *file) Sys() any                   { return nil }
func (f *file) Type() fs.FileMode          { return f.Mode().Type() }
func (f *file) Info() (fs.FileInfo, error) { return f, nil }

func (f *file) Mode() fs.FileMode {
	if f.IsDir() {
		return fs.ModeDir | 0555
	}
	return 0444
}

// An openFile is a regular file open for reading.
type openFile struct {
	f      *file // the file itself
	offset int64 // current read offset
}

func (f *openFile) Close() error               { return nil }
func (f *openFile) Stat() (fs.FileInfo, error) { return f.f, nil }

// Read reads up to len(b) bytes from the File and stores them in b.
// It returns the number of bytes read and any error encountered.
// At end of file, Read returns 0, io.EOF.
func (f *openFile) Read(b []byte) (int, error) {
	if f.offset >= int64(len(f.f.data)) {
		return 0, io.EOF
	}
	if f.offset < 0 {
		return 0, &fs.PathError{Op: "read", Path: f.f.name, Err: fs.ErrInvalid}
	}
	n := copy(b, f.f.data[f.offset:])
	f.offset += int64(n)
	return n, nil
}

var (
	_ io.Seeker   = (*openFile)(nil)
	_ fs.FileInfo = (*file)(nil)
)

func (f *openFile) Seek(offset int64, whence int) (int64, error) {
	switch whence {
	case 0:
		// offset += 0
	case 1:
		offset += f.offset
	case 2:
		offset += int64(len(f.f.data))
	}
	if offset < 0 || offset > int64(len(f.f.data)) {
		return 0, &fs.PathError{Op: "seek", Path: f.f.name, Err: fs.ErrInvalid}
	}
	f.offset = offset
	return offset, nil
}

func (f *openFile) Write(b []byte) (int, error) {
	if reflect.ValueOf(f).IsNil() {
		return 0, &fs.PathError{Op: "write", Path: f.f.name, Err: fs.ErrInvalid}
	}
	f.f.data += string(b)
	return len(b), nil
}

func New() *openFile {
	return &openFile{
		f:      &file{},
		offset: 0,
	}
}

它的工作原理是这样的：

package main

import (
	"fmt"
	"demo/byteToFile"
)

func main(){
	data := []byte("I like 邓文怡")
	object := byteToFile.New()
	_,err := object.Write(data)
	if err != nil{
		panic(err)
	}
	read := make([]byte,len(data))
	_,err = object.Read(read)
	if err != nil{
		panic(err)
	}
	fmt.Println(string(read))
}

希望它能帮到你！我喜欢哔哔声，很好！

I think something is accidentally lost in the process of converting []byte to io.ReadCloser, or os.File is the most appropriate for mp3.Decode, so I recommend converting []byte to os.File; And I succeeded, solved the problem, and got the music length. I try to use os.NewFile(0, "").Write() but the console output is garbled, and the sound cannot be played. So I wrote this myself:

// Package byteToFile
// []byte to fs.file, reference embed
package byteToFile

import (
	"io"
	"io/fs"
	"reflect"
	"time"
)

// A file is a single file in the FS.
// It implements fs.FileInfo and fs.DirEntry.
type file struct {
	name string
	data string
	hash [16]byte // truncated SHA256 hash
}

func (f *file) Name() string               { return f.name }
func (f *file) Size() int64                { return int64(len(f.data)) }
func (f *file) ModTime() time.Time         { return time.Time{} }
func (f *file) IsDir() bool                { return false }
func (f *file) Sys() any                   { return nil }
func (f *file) Type() fs.FileMode          { return f.Mode().Type() }
func (f *file) Info() (fs.FileInfo, error) { return f, nil }

func (f *file) Mode() fs.FileMode {
	if f.IsDir() {
		return fs.ModeDir | 0555
	}
	return 0444
}

// An openFile is a regular file open for reading.
type openFile struct {
	f      *file // the file itself
	offset int64 // current read offset
}

func (f *openFile) Close() error               { return nil }
func (f *openFile) Stat() (fs.FileInfo, error) { return f.f, nil }

// Read reads up to len(b) bytes from the File and stores them in b.
// It returns the number of bytes read and any error encountered.
// At end of file, Read returns 0, io.EOF.
func (f *openFile) Read(b []byte) (int, error) {
	if f.offset >= int64(len(f.f.data)) {
		return 0, io.EOF
	}
	if f.offset < 0 {
		return 0, &fs.PathError{Op: "read", Path: f.f.name, Err: fs.ErrInvalid}
	}
	n := copy(b, f.f.data[f.offset:])
	f.offset += int64(n)
	return n, nil
}

var (
	_ io.Seeker   = (*openFile)(nil)
	_ fs.FileInfo = (*file)(nil)
)

func (f *openFile) Seek(offset int64, whence int) (int64, error) {
	switch whence {
	case 0:
		// offset += 0
	case 1:
		offset += f.offset
	case 2:
		offset += int64(len(f.f.data))
	}
	if offset < 0 || offset > int64(len(f.f.data)) {
		return 0, &fs.PathError{Op: "seek", Path: f.f.name, Err: fs.ErrInvalid}
	}
	f.offset = offset
	return offset, nil
}

func (f *openFile) Write(b []byte) (int, error) {
	if reflect.ValueOf(f).IsNil() {
		return 0, &fs.PathError{Op: "write", Path: f.f.name, Err: fs.ErrInvalid}
	}
	f.f.data += string(b)
	return len(b), nil
}

func New() *openFile {
	return &openFile{
		f:      &file{},
		offset: 0,
	}
}

It works like this:

package main

import (
	"fmt"
	"demo/byteToFile"
)

func main(){
	data := []byte("I like 邓文怡")
	object := byteToFile.New()
	_,err := object.Write(data)
	if err != nil{
		panic(err)
	}
	read := make([]byte,len(data))
	_,err = object.Read(read)
	if err != nil{
		panic(err)
	}
	fmt.Println(string(read))
}

Hope it can help you! I like beep it's good!

I think the problem has been solved. This is my blog article, which contains more information: https://blog.csdn.net/Deng_Xian_Sheng/article/details/125128054?ops_request_misc=&request_id=e233f01259634c8a88aba26c32e9cd7c&biz_id=&utm_medium=distribute.pc_search_result.none -Task blog-2~~blog~~koosearch~default-1-125128054 null null. 268 ^ v1 ^ control&utm_ Term=beep&spm=1018.2226.3001.4450

…name-to-readme-links Apply the master -> main branch rename to links and images in the README

duysqubix mentioned this issue Oct 10, 2023

Fix mp3.decoder.Len() when file size is unknown gopxl/beep#37

Open

MarkKremer pushed a commit to MarkKremer/beep that referenced this issue Apr 6, 2024

Merge pull request faiface#123 from gopxl/apply-master-main-branch-re…

a11e999

…name-to-readme-links Apply the master -> main branch rename to links and images in the README

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Streamer from bytes reader has a length of 0 #123

Streamer from bytes reader has a length of 0 #123

abhobe commented Jun 1, 2021

Deng-Xian-Sheng commented Jun 4, 2022 •

edited

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ivcz commented Jun 6, 2023

ivcz commented Jun 6, 2023

Deng-Xian-Sheng commented Jun 9, 2023

Streamer from bytes reader has a length of 0 #123

Streamer from bytes reader has a length of 0 #123

Comments

abhobe commented Jun 1, 2021

Deng-Xian-Sheng commented Jun 4, 2022 • edited Loading

ivcz commented Jun 6, 2023

ivcz commented Jun 6, 2023

Deng-Xian-Sheng commented Jun 9, 2023

Deng-Xian-Sheng commented Jun 4, 2022 •

edited

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