mirror of
https://github.com/JetSetIlly/Gopher2600.git
synced 2025-04-02 11:02:17 -04:00
3aa5885ebe
curated package predated the standard errors package introduced in go1.13 the standard package does a better job of what curated attempted to do the change of package also gave me a opportunity to clean up the error messages a little bit
135 lines
4 KiB
Go
135 lines
4 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/hardware/television"
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"github.com/jetsetilly/gopher2600/hardware/television/signal"
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"github.com/jetsetilly/gopher2600/hardware/television/specification"
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)
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// Video is an implementation of the television.PixelRenderer interface with an
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// embedded television for convenience. It generates a SHA-1 value of the image
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// every frame. it does not display the image anywhere.
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//
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// Note that the use of SHA-1 is fine for this application because this is not
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// a cryptographic task.
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type Video struct {
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*television.Television
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spec specification.Spec
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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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// NewVideo 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 NewVideo(tv *television.Television) (*Video, error) {
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// set up digest tv
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dig := &Video{
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Television: tv,
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spec: specification.SpecNTSC,
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}
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// register ourselves as a television.Renderer
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dig.AddPixelRenderer(dig)
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// length of pixels array contains enough room for the previous frames digest value
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l := len(dig.digest)
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l += specification.AbsoluteMaxClks * pixelDepth
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// allocate enough pixels for entire frame
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dig.pixels = make([]byte, l)
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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 Video) 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 *Video) 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.PixelRenderer interface
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//
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// In this implementation we only handle specification changes. This means the
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// digest is immune from changes to the frame resizing method used by the
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// television implementation. Changes to how the specification is flipped might
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// cause comparison failures however.
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func (dig *Video) Resize(frameInfo television.FrameInfo) error {
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dig.spec = frameInfo.Spec
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return nil
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}
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// NewFrame implements television.PixelRenderer interface.
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func (dig *Video) NewFrame(_ television.FrameInfo) error {
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// chain fingerprints by copying the value of the last fingerprint
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// to the head of the video 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 fmt.Errorf("digest: video: 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++
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return nil
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}
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// NewScanline implements television.PixelRenderer interface.
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func (dig *Video) NewScanline(scanline int) error {
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return nil
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}
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// SetPixels implements television.PixelRenderer interface.
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func (dig *Video) SetPixels(sig []signal.SignalAttributes, _ int) error {
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// offset always starts at after the digest leader
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offset := len(dig.digest)
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for i := range sig {
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// ignore VBLANK and extract the color signal in all situations
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px := signal.ColorSignal((sig[i] & signal.Color) >> signal.ColorShift)
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col := dig.spec.GetColor(px)
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// setting every pixel regardless of vblank value
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s := dig.pixels[offset : offset+3 : offset+3]
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s[0] = col.R
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s[1] = col.G
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s[2] = col.B
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offset += pixelDepth
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}
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return nil
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}
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// Reset implements television.PixelRenderer interface.
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func (dig *Video) Reset() {
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}
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// EndRendering implements television.PixelRenderer interface.
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func (dig *Video) EndRendering() error {
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return nil
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}
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