mirror of
https://github.com/hajimehoshi/ebiten.git
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124 lines
3.2 KiB
Go
124 lines
3.2 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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package audio
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import (
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"fmt"
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"io"
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)
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// InfiniteLoop represents a looped stream which never ends.
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type InfiniteLoop struct {
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src io.ReadSeeker
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lstart int64
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llength int64
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pos int64
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}
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// NewInfiniteLoop creates a new infinite loop stream with a source stream and length in bytes.
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func NewInfiniteLoop(src io.ReadSeeker, length int64) *InfiniteLoop {
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return NewInfiniteLoopWithIntro(src, 0, length)
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}
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// NewInfiniteLoopWithIntro creates a new infinite loop stream with an intro part.
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// NewInfiniteLoopWithIntro accepts a source stream src, introLength in bytes and loopLength in bytes.
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func NewInfiniteLoopWithIntro(src io.ReadSeeker, introLength int64, loopLength int64) *InfiniteLoop {
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return &InfiniteLoop{
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src: src,
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lstart: introLength / bytesPerSample * bytesPerSample,
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llength: loopLength / bytesPerSample * bytesPerSample,
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pos: -1,
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}
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}
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func (i *InfiniteLoop) length() int64 {
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return i.lstart + i.llength
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}
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func (i *InfiniteLoop) ensurePos() error {
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if i.pos >= 0 {
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return nil
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}
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pos, err := i.src.Seek(0, io.SeekCurrent)
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if err != nil {
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return err
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}
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if pos >= i.length() {
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return fmt.Errorf("audio: stream position must be less than the specified length")
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}
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i.pos = pos
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return nil
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}
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// Read is implementation of ReadSeeker's Read.
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func (i *InfiniteLoop) Read(b []byte) (int, error) {
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if err := i.ensurePos(); err != nil {
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return 0, err
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}
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if i.pos+int64(len(b)) > i.length() {
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b = b[:i.length()-i.pos]
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}
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n, err := i.src.Read(b)
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i.pos += int64(n)
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if i.pos > i.length() {
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panic(fmt.Sprintf("audio: position must be <= length but not at (*InfiniteLoop).Read: pos: %d, length: %d", i.pos, i.length()))
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}
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if err != nil && err != io.EOF {
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return 0, err
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}
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if err == io.EOF || i.pos == i.length() {
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pos, err := i.Seek(i.lstart, io.SeekStart)
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if err != nil {
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return 0, err
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}
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i.pos = pos
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}
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return n, nil
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}
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// Seek is implementation of ReadSeeker's Seek.
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func (i *InfiniteLoop) Seek(offset int64, whence int) (int64, error) {
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if err := i.ensurePos(); err != nil {
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return 0, err
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}
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next := int64(0)
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switch whence {
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case io.SeekStart:
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next = offset
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case io.SeekCurrent:
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next = i.pos + offset
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case io.SeekEnd:
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return 0, fmt.Errorf("audio: whence must be io.SeekStart or io.SeekCurrent for InfiniteLoop")
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}
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if next < 0 {
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return 0, fmt.Errorf("audio: position must >= 0")
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}
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if next >= i.lstart {
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next = ((next - i.lstart) % i.llength) + i.lstart
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}
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// Ignore the new position returned by Seek since the source position might not be match with the position
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// managed by this.
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if _, err := i.src.Seek(next, io.SeekStart); err != nil {
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return 0, err
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}
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i.pos = next
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return i.pos, nil
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}
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