mirror of
https://github.com/hajimehoshi/ebiten.git
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124 lines
2.9 KiB
Go
124 lines
2.9 KiB
Go
// Copyright 2016 Hajime Hoshi
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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 example jsgo
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package main
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import (
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"errors"
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"fmt"
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"io"
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"log"
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"math"
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"github.com/hajimehoshi/ebiten"
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"github.com/hajimehoshi/ebiten/audio"
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"github.com/hajimehoshi/ebiten/ebitenutil"
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)
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const (
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screenWidth = 320
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screenHeight = 240
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sampleRate = 44100
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frequency = 440
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)
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var audioContext *audio.Context
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func init() {
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var err error
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audioContext, err = audio.NewContext(sampleRate)
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if err != nil {
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log.Fatal(err)
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}
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}
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// stream is an infinite stream of 440 Hz sine wave.
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type stream struct {
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position int64
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}
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// Read is io.Reader's Read.
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//
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// Read fills the data with sine wave samples.
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func (s *stream) Read(data []byte) (int, error) {
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if len(data)%4 != 0 {
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return 0, errors.New("len(data) % 4 must be 0")
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}
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const length = sampleRate / frequency // TODO: This should be integer?
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p := s.position / 4
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for i := 0; i < len(data)/4; i++ {
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const max = (1<<15 - 1) / 2
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b := int16(math.Sin(2*math.Pi*float64(p)/length) * max)
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data[4*i] = byte(b)
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data[4*i+1] = byte(b >> 8)
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data[4*i+2] = byte(b)
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data[4*i+3] = byte(b >> 8)
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p++
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}
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s.position += int64(len(data))
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s.position %= length * 4
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return len(data), nil
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}
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// Seek is io.Seeker's Seek.
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//
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// whence must be io.SeekStart or io.SeekCurrent.
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func (s *stream) Seek(offset int64, whence int) (int64, error) {
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const length = sampleRate / frequency
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switch whence {
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case io.SeekStart:
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s.position = offset
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case io.SeekCurrent:
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s.position += offset
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default:
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return 0, errors.New("whence must be io.SeekStart or io.SeekCurrent")
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}
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s.position %= length * 4
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return s.position, nil
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}
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// Close is io.Closer's Close.
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func (s *stream) Close() error {
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return nil
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}
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var player *audio.Player
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func update(screen *ebiten.Image) error {
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if player == nil {
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// Pass the (infinite) stream to audio.NewPlayer.
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// After calling Play, the stream never ends as long as the player object lives.
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var err error
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player, err = audio.NewPlayer(audioContext, &stream{})
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if err != nil {
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return err
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}
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player.Play()
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}
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if ebiten.IsRunningSlowly() {
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return nil
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}
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msg := fmt.Sprintf("FPS: %0.2f\nThis is an example using infinite audio stream.", ebiten.CurrentFPS())
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ebitenutil.DebugPrint(screen, msg)
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return nil
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}
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func main() {
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if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Sine Wave (Ebiten Demo)"); err != nil {
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log.Fatal(err)
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}
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}
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