ebiten/audio/internal/convert/stereoi16.go

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// 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.
package convert
import (
"io"
)
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type StereoI16 struct {
source io.ReadSeeker
mono bool
eight bool
buf []byte
}
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func NewStereoI16(source io.ReadSeeker, mono, eight bool) *StereoI16 {
return &StereoI16{
source: source,
mono: mono,
eight: eight,
}
}
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func (s *StereoI16) Read(b []byte) (int, error) {
l := len(b) / 4 * 4
if s.mono {
l /= 2
}
if s.eight {
l /= 2
}
if cap(s.buf) < l {
s.buf = make([]byte, l)
}
n, err := s.source.Read(s.buf[:l])
if err != nil && err != io.EOF {
return 0, err
}
switch {
case s.mono && s.eight:
for i := 0; i < n; i++ {
v := int16(int(s.buf[i])*0x101 - (1 << 15))
b[4*i] = byte(v)
b[4*i+1] = byte(v >> 8)
b[4*i+2] = byte(v)
b[4*i+3] = byte(v >> 8)
}
case s.mono && !s.eight:
for i := 0; i < n/2; i++ {
b[4*i] = s.buf[2*i]
b[4*i+1] = s.buf[2*i+1]
b[4*i+2] = s.buf[2*i]
b[4*i+3] = s.buf[2*i+1]
}
case !s.mono && s.eight:
for i := 0; i < n/2; i++ {
v0 := int16(int(s.buf[2*i])*0x101 - (1 << 15))
v1 := int16(int(s.buf[2*i+1])*0x101 - (1 << 15))
b[4*i] = byte(v0)
b[4*i+1] = byte(v0 >> 8)
b[4*i+2] = byte(v1)
b[4*i+3] = byte(v1 >> 8)
}
default:
copy(b[:n], s.buf[:n])
}
if s.mono {
n *= 2
}
if s.eight {
n *= 2
}
return n, err
}
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func (s *StereoI16) Seek(offset int64, whence int) (int64, error) {
offset = offset / 4 * 4
if s.mono {
offset /= 2
}
if s.eight {
offset /= 2
}
return s.source.Seek(offset, whence)
}