mirror of
https://github.com/JetSetIlly/Gopher2600.git
synced 2025-04-02 11:02:17 -04:00
9f50f3c77e
- implemented audio
- using Ron Fries' method as the basis
- removed sample playback - performance of Fries' method is good
enough that we'll never need it again
- sdl audio routines using QueueAudio() - maybe better if we use
callbacks?
- sketched wavwriter AudioMixer - not usable yet
108 lines
2.8 KiB
Go
108 lines
2.8 KiB
Go
package screendigest
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import (
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"crypto/sha1"
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"fmt"
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"gopher2600/errors"
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"gopher2600/television"
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)
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// SHA1 is an implementation of the television.Renderer interface with an
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// embedded television for convenience. It generates a sha1 value of the
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// image every frame. it does not display the image anywhere.
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//
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// Note that the use of sha1 is fine for this application because this is not a
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// cryptographic task.
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type SHA1 struct {
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television.Television
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digest [sha1.Size]byte
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pixels []byte
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frameNum int
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}
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const pixelDepth = 3
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// NewSHA1 initialises a new instance of DigestTV. For convenience, the
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// television argument can be nil, in which case an instance of
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// StellaTelevision will be created.
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func NewSHA1(tv television.Television) (*SHA1, error) {
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// set up digest tv
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dig := &SHA1{Television: tv}
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// register ourselves as a television.Renderer
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dig.AddPixelRenderer(dig)
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// set attributes that depend on the television specification
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dig.Resize(-1, -1)
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return dig, nil
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}
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func (dig SHA1) String() string {
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return fmt.Sprintf("%x", dig.digest)
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}
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// ResetDigest resets the current digest value to 0
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func (dig *SHA1) 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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// Resize implements television.Television interface
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func (dig *SHA1) Resize(_, _ int) error {
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// length of pixels array contains enough room for the previous frames
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// digest value
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l := len(dig.digest)
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// alloscate enough pixels for entire frame
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l += ((television.HorizClksScanline + 1) * (dig.GetSpec().ScanlinesTotal + 1) * pixelDepth)
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dig.pixels = make([]byte, l)
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return nil
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}
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// NewFrame implements television.Renderer interface
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func (dig *SHA1) NewFrame(frameNum int) error {
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// chain fingerprints by copying the value of the last fingerprint
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// to the head of the screen data
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n := copy(dig.pixels, dig.digest[:])
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if n != len(dig.digest) {
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return errors.New(errors.ScreenDigest, fmt.Sprintf("digest error during new frame"))
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}
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dig.digest = sha1.Sum(dig.pixels)
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dig.frameNum = frameNum
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return nil
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}
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// NewScanline implements television.Renderer interface
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func (dig *SHA1) NewScanline(scanline int) error {
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return nil
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}
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// SetPixel implements television.Renderer interface
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func (dig *SHA1) SetPixel(x, y int, red, green, blue byte, vblank bool) error {
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// preserve the first few bytes for a chained fingerprint
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i := len(dig.digest)
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i += television.HorizClksScanline * y * pixelDepth
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i += x * pixelDepth
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if i <= len(dig.pixels)-pixelDepth {
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// setting every pixel regardless of vblank value
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dig.pixels[i] = red
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dig.pixels[i+1] = green
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dig.pixels[i+2] = blue
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}
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return nil
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}
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// SetAltPixel implements television.Renderer interface
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func (dig *SHA1) SetAltPixel(x, y int, red, green, blue byte, vblank bool) error {
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return nil
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}
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// EndRendering implements television.Renderer interface
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func (dig *SHA1) EndRendering() error {
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return nil
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}
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