113 lines
2.9 KiB
Go
113 lines
2.9 KiB
Go
// Implementation of RFC 6143 §7.4 Pixel Format Data Structure.
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package vnc
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"io"
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"math"
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)
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var (
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PixelFormat8bit *PixelFormat = NewPixelFormat(8)
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PixelFormat16bit *PixelFormat = NewPixelFormat(16)
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PixelFormat32bit *PixelFormat = NewPixelFormat(32)
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)
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// PixelFormat describes the way a pixel is formatted for a VNC connection.
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type PixelFormat struct {
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BPP uint8 // bits-per-pixel
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Depth uint8 // depth
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BigEndian uint8 // big-endian-flag
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TrueColor uint8 // true-color-flag
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RedMax, GreenMax, BlueMax uint16 // red-, green-, blue-max (2^BPP-1)
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RedShift, GreenShift, BlueShift uint8 // red-, green-, blue-shift
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_ [3]byte // padding
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}
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const pixelFormatLen = 16
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// NewPixelFormat returns a populated PixelFormat structure.
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func NewPixelFormat(bpp uint8) *PixelFormat {
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bigEndian := uint8(1)
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rgbMax := uint16(math.Exp2(float64(bpp))) - 1
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var (
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tc = uint8(1)
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rs, gs, bs uint8
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)
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switch bpp {
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case 8:
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tc = 0
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rs, gs, bs = 0, 0, 0
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case 16:
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rs, gs, bs = 0, 4, 8
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case 32:
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rs, gs, bs = 0, 8, 16
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}
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return &PixelFormat{bpp, bpp, bigEndian, tc, rgbMax, rgbMax, rgbMax, rs, gs, bs, [3]byte{}}
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}
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// Marshal implements the Marshaler interface.
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func (pf *PixelFormat) Marshal() ([]byte, error) {
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// Validation checks.
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switch pf.BPP {
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case 8, 16, 32:
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default:
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return nil, fmt.Errorf("Invalid BPP value %v; must be 8, 16, or 32.", pf.BPP)
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}
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if pf.Depth < pf.BPP {
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return nil, fmt.Errorf("Invalid Depth value %v; cannot be < BPP", pf.Depth)
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}
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switch pf.Depth {
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case 8, 16, 32:
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default:
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return nil, fmt.Errorf("Invalid Depth value %v; must be 8, 16, or 32.", pf.Depth)
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}
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// Create the slice of bytes
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buf := bytes.NewBuffer(nil)
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if err := binary.Write(buf, binary.BigEndian, &pf); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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// Read reads from an io.Reader, and populates the PixelFormat.
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func (pf *PixelFormat) Read(r io.Reader) error {
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buf := make([]byte, pixelFormatLen)
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if _, err := io.ReadAtLeast(r, buf, pixelFormatLen); err != nil {
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return err
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}
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return pf.Unmarshal(buf)
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}
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// Unmarshal implements the Unmarshaler interface.
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func (pf *PixelFormat) Unmarshal(data []byte) error {
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buf := bytes.NewBuffer(data)
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var msg PixelFormat
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if err := binary.Read(buf, binary.BigEndian, &msg); err != nil {
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return err
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}
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*pf = msg
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return nil
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}
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// String implements the fmt.Stringer interface.
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func (pf *PixelFormat) String() string {
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return fmt.Sprintf("{ bpp: %d depth: %d big-endian: %s true-color: %s red-max: %d green-max: %d blue-max: %d red-shift: %d green-shift: %d blue-shift: %d }",
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pf.BPP, pf.Depth, pf.BigEndian, pf.TrueColor, pf.RedMax, pf.GreenMax, pf.BlueMax, pf.RedShift, pf.GreenShift, pf.BlueShift)
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}
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func (pf *PixelFormat) order() binary.ByteOrder {
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if pf.BigEndian == 1 {
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return binary.BigEndian
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}
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return binary.LittleEndian
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}
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