mirror of
https://github.com/JetSetIlly/Gopher2600.git
synced 2025-04-02 11:02:17 -04:00
106 lines
3 KiB
Go
106 lines
3 KiB
Go
// This file is part of Gopher2600.
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//
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// Gopher2600 is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Gopher2600 is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Gopher2600. If not, see <https://www.gnu.org/licenses/>.
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package digest
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import (
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"crypto/sha1"
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"fmt"
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"github.com/jetsetilly/gopher2600/curated"
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"github.com/jetsetilly/gopher2600/hardware/television"
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)
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// the length of the buffer we're using isn't really important. that said, it
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// needs to be at least sha1.Size bytes in length.
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const audioBufferLength = 1024 + sha1.Size
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// to allow us to create digests on audio streams longer than
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// audioBufferLength, we'll stuff the previous digest value into the first part
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// of the buffer array and make sure we include it when we create the next
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// digest value.
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const audioBufferStart = sha1.Size
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// Audio is an implementation of the television.AudioMixer interface with an
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// embedded television for convenience. It periodically generates a SHA-1 value
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// of the audio stream.
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//
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// Note that the use of SHA-1 is fine for this application because this is not a
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// cryptographic task.
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type Audio struct {
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*television.Television
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digest [sha1.Size]byte
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buffer []uint8
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bufferCt int
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}
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// NewAudio is the preferred method of initialisation for the Audio2Wav type.
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func NewAudio(tv *television.Television) (*Audio, error) {
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dig := &Audio{Television: tv}
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// register ourselves as a protocol.AudioMixer
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dig.AddAudioMixer(dig)
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// create buffer
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dig.buffer = make([]uint8, audioBufferLength)
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dig.bufferCt = audioBufferStart
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return dig, nil
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}
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// Hash implements digest.Digest interface.
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func (dig Audio) Hash() string {
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return fmt.Sprintf("%x", dig.digest)
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}
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// ResetDigest implements digest.Digest interface.
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func (dig *Audio) ResetDigest() {
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for i := range dig.digest {
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dig.digest[i] = 0
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}
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}
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// SetAudio implements the protocol.AudioMixer interface.
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func (dig *Audio) SetAudio(audioData uint8) error {
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dig.buffer[dig.bufferCt] = audioData
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dig.bufferCt++
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if dig.bufferCt >= audioBufferLength {
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return dig.flushAudio()
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}
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return nil
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}
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// Reset implements the protocol.AudioMixer interface.
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func (dig *Audio) Reset() {
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_ = dig.flushAudio()
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}
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func (dig *Audio) flushAudio() error {
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dig.digest = sha1.Sum(dig.buffer)
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n := copy(dig.buffer, dig.digest[:])
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if n != len(dig.digest) {
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return curated.Errorf("digest: audio: digest error while flushing audio stream")
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}
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dig.bufferCt = audioBufferStart
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return nil
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}
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// EndMixing implements the protocol.AudioMixer interface.
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func (dig *Audio) EndMixing() error {
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return nil
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}
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