mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-09-20 05:12:18 +02:00
130 lines
2.9 KiB
Go
130 lines
2.9 KiB
Go
// Copyright 2017 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build js
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package mp3
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import (
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"github.com/gopherjs/gopherjs/js"
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"github.com/hajimehoshi/ebiten/audio"
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)
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// TODO: This just uses decodeAudioData can treat audio files other than MP3.
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type Stream struct {
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leftData []float32
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rightData []float32
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posInBytes int
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}
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func (s *Stream) Read(b []byte) (int, error) {
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l := len(s.leftData)*4 - s.posInBytes
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if l > len(b) {
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l = len(b)
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}
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l = l / 4 * 4
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const max = 1<<15 - 1
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for i := 0; i < l/4; i++ {
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il := int32(s.leftData[s.posInBytes/4+i] * max)
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if il > max {
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il = max
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}
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if il < -max {
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il = -max
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}
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ir := int32(s.rightData[s.posInBytes/4+i] * max)
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if ir > max {
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ir = max
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}
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if ir < -max {
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ir = -max
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}
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b[4*i] = uint8(il)
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b[4*i+1] = uint8(il >> 8)
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b[4*i+2] = uint8(ir)
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b[4*i+3] = uint8(ir >> 8)
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}
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s.posInBytes += l
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if s.posInBytes == len(s.leftData)*4 {
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return l, io.EOF
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}
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return l, nil
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}
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func (s *Stream) Seek(offset int64, whence int) (int64, error) {
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next := int64(0)
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switch whence {
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case 0:
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next = offset
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case 1:
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next = int64(s.posInBytes) + offset
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case 2:
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next = s.Size() + offset
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}
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s.posInBytes = int(next)
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return next, nil
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}
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func (s *Stream) Close() error {
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return nil
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}
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func (s *Stream) Size() int64 {
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return int64(len(s.leftData) * 4)
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}
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func Decode(context *audio.Context, src audio.ReadSeekCloser) (*Stream, error) {
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b, err := ioutil.ReadAll(src)
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if err != nil {
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return nil, err
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}
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if err := src.Close(); err != nil {
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return nil, err
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}
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s := &Stream{}
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ch := make(chan error)
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klass := js.Global.Get("OfflineAudioContext")
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if klass == js.Undefined {
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klass = js.Global.Get("webkitOfflineAudioContext")
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}
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if klass == js.Undefined {
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return nil, errors.New("audio/mp3: OfflineAudioContext is not available")
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}
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// TODO: 1 is a correct second argument?
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oc := klass.New(2, 1, context.SampleRate())
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oc.Call("decodeAudioData", js.NewArrayBuffer(b), func(buf *js.Object) {
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s.leftData = buf.Call("getChannelData", 0).Interface().([]float32)
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switch n := buf.Get("numberOfChannels").Int(); n {
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case 1:
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s.rightData = s.leftData
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case 2:
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s.rightData = buf.Call("getChannelData", 1).Interface().([]float32)
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default:
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ch <- fmt.Errorf("audio/mp3: Number of channels must be 1 or 2 but %d", n)
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}
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close(ch)
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})
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if err := <-ch; err != nil {
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return nil, err
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}
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return s, nil
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}
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