ebiten/exp/audio/audio_windows.go

// Copyright 2015 Hajime Hoshi
//
// 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.

package audio

// #cgo LDFLAGS: -lwinmm
//
// #include <windows.h>
// #include <mmsystem.h>
//
// #define sizeOfWavehdr (sizeof(WAVEHDR))
//
// MMRESULT waveOutOpen2(HWAVEOUT* waveOut, WAVEFORMATEX* format);
import "C"

import (
	"fmt"
	"io"
	"time"
	"unsafe"
)

type header struct {
	buffer     unsafe.Pointer
	bufferSize int
	waveHdr    C.WAVEHDR
}

// TODO: Reduce panics and use errors instead

func newHeader(waveOut C.HWAVEOUT, bufferSize int) header {
	// NOTE: This is never freed so far.
	buf := C.malloc(C.size_t(bufferSize))
	h := header{
		buffer:     buf,
		bufferSize: bufferSize,
		waveHdr: C.WAVEHDR{
			lpData:         C.LPSTR(buf),
			dwBufferLength: C.DWORD(bufferSize),
		},
	}
	// TODO: Need to unprepare to avoid memory leak?
	if err := C.waveOutPrepareHeader(waveOut, &h.waveHdr, C.sizeOfWavehdr); err != C.MMSYSERR_NOERROR {
		panic(fmt.Sprintf("audio: waveOutPrepareHeader error %d", err))
	}
	return h
}

func (h *header) Write(waveOut C.HWAVEOUT, data []byte) {
	if len(data) != h.bufferSize {
		panic("audio: len(data) must equal to h.bufferSize")
	}
	C.memcpy(h.buffer, unsafe.Pointer(&data[0]), C.size_t(h.bufferSize))
	if err := C.waveOutWrite(waveOut, &h.waveHdr, C.sizeOfWavehdr); err != C.MMSYSERR_NOERROR {
		panic(fmt.Sprintf("audio: waveOutWriter error %d", err))
	}
}

const numHeader = 8

var sem = make(chan struct{}, numHeader)

//export releaseSemaphore
func releaseSemaphore() {
	<-sem
}

type player struct {
	src     io.Reader
	out     C.HWAVEOUT
	i       int
	buffer  []byte
	headers []header
}

const bufferSize = 1024

func startPlaying(src io.Reader, sampleRate int) error {
	const numBlockAlign = channelNum * bitsPerSample / 8
	f := C.WAVEFORMATEX{
		wFormatTag:      C.WAVE_FORMAT_PCM,
		nChannels:       channelNum,
		nSamplesPerSec:  C.DWORD(sampleRate),
		nAvgBytesPerSec: C.DWORD(sampleRate) * numBlockAlign,
		wBitsPerSample:  bitsPerSample,
		nBlockAlign:     numBlockAlign,
	}
	var w C.HWAVEOUT
	if err := C.waveOutOpen2(&w, &f); err != C.MMSYSERR_NOERROR {
		return fmt.Errorf("audio: waveOutOpen error: %d", err)
	}
	p := &player{
		src:     src,
		out:     w,
		buffer:  []byte{},
		headers: make([]header, numHeader),
	}
	for i := 0; i < numHeader; i++ {
		p.headers[i] = newHeader(w, bufferSize)
	}
	go func() {
		defer p.close()
		for {
			err := p.proceed()
			if err == io.EOF {
				break
			}
			if err != nil {
				// TODO: Propagate this error?
				panic(err)
			}
			time.Sleep(1 * time.Millisecond)
		}
	}()
	return nil
}

func (p *player) proceed() error {
	b := make([]byte, bufferSize)
	n, err := p.src.Read(b)
	if 0 < n {
		p.buffer = append(p.buffer, b[:n]...)
		for bufferSize <= len(p.buffer) {
			sem <- struct{}{}
			p.headers[p.i].Write(p.out, p.buffer[:bufferSize])
			p.buffer = p.buffer[bufferSize:]
			p.i++
			p.i %= len(p.headers)
		}
	}
	return err
}

func (p *player) close() {
	// TODO: Implement this
}