audio/mp3: Remove the GopherJS part

Updates #1129

audio/mp3/decode.go

@@ -12,8 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build !js wasm
-
 // Package mp3 provides MP3 decoder.
 //
 // On desktops and mobiles, a pure Go decoder is used.

audio/mp3/decode_gopherjs.go

@@ -1,245 +0,0 @@
-// Copyright 2017 The Ebiten Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// +build js
-// +build !wasm
-
-package mp3
-
-import (
-	"errors"
-	"fmt"
-	"io"
-	"io/ioutil"
-	"math"
-	"syscall/js"
-	"time"
-
-	"github.com/hajimehoshi/ebiten/v2/audio"
-)
-
-// TODO: This just uses decodeAudioData, that can treat audio files other than MP3.
-
-type Stream struct {
-	leftData   []float32
-	rightData  []float32
-	posInBytes int
-}
-
-var (
-	errTryAgain = errors.New("mp3: try again")
-	errTimeout  = errors.New("mp3: timeout")
-)
-
-func (s *Stream) Read(b []byte) (int, error) {
-	l := len(s.leftData)*4 - s.posInBytes
-	if l > len(b) {
-		l = len(b)
-	}
-	l = l / 4 * 4
-	const max = 1<<15 - 1
-	for i := 0; i < l/4; i++ {
-		il := int32(s.leftData[s.posInBytes/4+i] * max)
-		if il > max {
-			il = max
-		}
-		if il < -max {
-			il = -max
-		}
-		ir := int32(s.rightData[s.posInBytes/4+i] * max)
-		if ir > max {
-			ir = max
-		}
-		if ir < -max {
-			ir = -max
-		}
-		b[4*i] = byte(il)
-		b[4*i+1] = byte(il >> 8)
-		b[4*i+2] = byte(ir)
-		b[4*i+3] = byte(ir >> 8)
-	}
-	s.posInBytes += l
-	if s.posInBytes == len(s.leftData)*4 {
-		return l, io.EOF
-	}
-	return l, nil
-}
-
-func (s *Stream) Seek(offset int64, whence int) (int64, error) {
-	next := int64(0)
-	switch whence {
-	case io.SeekStart:
-		next = offset
-	case io.SeekCurrent:
-		next = int64(s.posInBytes) + offset
-	case io.SeekEnd:
-		next = s.Length() + offset
-	}
-	s.posInBytes = int(next)
-	return next, nil
-}
-
-func (s *Stream) Close() error {
-	return nil
-}
-
-func (s *Stream) Length() int64 {
-	return int64(len(s.leftData) * 4)
-}
-
-// seekNextFrame seeks the next frame and returns the new buffer with the new position.
-// seekNextFrame also returns true when seeking is successful, or false otherwise.
-//
-// Seeking is necessary when decoding fails. Safari's MP3 decoder can't treat IDs well (#438).
-func seekNextFrame(buf []byte) ([]byte, bool) {
-	// TODO: Need to skip tags explicitly? (hajimehoshi/go-mp3#9)
-
-	if len(buf) < 1 {
-		return nil, false
-	}
-	buf = buf[1:]
-
-	for {
-		if buf[0] == 0xff && buf[1]&0xfe == 0xfe {
-			break
-		}
-		buf = buf[1:]
-		if len(buf) < 2 {
-			return nil, false
-		}
-	}
-	return buf, true
-}
-
-func Decode(context *audio.Context, src audio.ReadSeekCloser) (*Stream, error) {
-	b, err := ioutil.ReadAll(src)
-	if err != nil {
-		return nil, err
-	}
-	if err := src.Close(); err != nil {
-		return nil, err
-	}
-	var s *Stream
-	try := 0
-	for {
-		s, err = decode(context, b, try)
-		switch err {
-		case errTryAgain:
-			buf, ok := seekNextFrame(b)
-			if !ok {
-				return nil, fmt.Errorf("mp3: Decode failed: invalid format?")
-			}
-			b = buf
-			continue
-		case errTimeout:
-			try++
-			continue
-		default:
-			if err != nil {
-				return nil, err
-			}
-		}
-		break
-	}
-	return s, nil
-}
-
-var offlineAudioContextClass = js.Null()
-
-func init() {
-	if klass := js.Global().Get("OfflineAudioContext"); klass != js.Undefined() {
-		offlineAudioContextClass = klass
-		return
-	}
-	if klass := js.Global().Get("webkitOfflineAudioContext"); klass != js.Undefined() {
-		offlineAudioContextClass = klass
-		return
-	}
-}
-
-func float32ArrayToSlice(arr js.Value) []float32 {
-	f := make([]float32, arr.Length())
-	a := js.TypedArrayOf(f)
-	a.Call("set", arr)
-	a.Release()
-	return f
-}
-
-func decode(context *audio.Context, buf []byte, try int) (*Stream, error) {
-	if offlineAudioContextClass == js.Null() {
-		return nil, errors.New("mp3: OfflineAudioContext is not available")
-	}
-
-	s := &Stream{}
-	ch := make(chan error)
-
-	// TODO: webkitOfflineAudioContext's constructor might causes 'Syntax' error
-	// when the sample rate is not so usual like 22050 on Safari.
-	// Should this be handled before calling this?
-
-	// TODO: 1 is a correct second argument?
-	oc := offlineAudioContextClass.New(2, 1, context.SampleRate())
-
-	u8 := js.TypedArrayOf(buf)
-	defer u8.Release()
-	a := u8.Get("buffer").Call("slice", u8.Get("byteOffset"), u8.Get("byteOffset").Int()+u8.Get("byteLength").Int())
-
-	succeeded := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
-		buf := args[0]
-		s.leftData = float32ArrayToSlice(buf.Call("getChannelData", 0))
-		switch n := buf.Get("numberOfChannels").Int(); n {
-		case 1:
-			s.rightData = s.leftData
-			close(ch)
-		case 2:
-			s.rightData = float32ArrayToSlice(buf.Call("getChannelData", 1))
-			close(ch)
-		default:
-			ch <- fmt.Errorf("mp3: number of channels must be 1 or 2 but %d", n)
-		}
-		return nil
-	})
-	defer succeeded.Release()
-
-	failed := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
-		err := args[0]
-		if err != js.Null() || err != js.Undefined() {
-			ch <- fmt.Errorf("mp3: decodeAudioData failed: %v", err)
-		} else {
-			// On Safari, error value might be null and it is needed to retry decoding
-			// from the next frame (#438).
-			ch <- errTryAgain
-		}
-		return nil
-	})
-	defer failed.Release()
-
-	oc.Call("decodeAudioData", a, succeeded, failed)
-
-	timeout := time.Duration(math.Pow(2, float64(try))) * time.Second
-	t := time.NewTimer(timeout)
-	defer t.Stop()
-
-	select {
-	case err := <-ch:
-		if err != nil {
-			return nil, err
-		}
-	case <-t.C:
-		// Sometimes decode fails without calling the callbacks (#464).
-		// Let's just try again in this case.
-		return nil, errTimeout
-	}
-	return s, nil
-}