// Implementation of RFC 6143 ยง7.4 Pixel Format Data Structure.
package vnc
import (
"bytes"
"encoding/binary"
"fmt"
"io"
)
var (
PixelFormat8bit *PixelFormat = NewPixelFormat(8)
PixelFormat16bit *PixelFormat = NewPixelFormat(16)
PixelFormat32bit *PixelFormat = NewPixelFormat(32)
)
// PixelFormat describes the way a pixel is formatted for a VNC connection.
type PixelFormat struct {
BPP uint8 // bits-per-pixel
Depth uint8 // depth
BigEndian uint8 // big-endian-flag
TrueColor uint8 // true-color-flag
RedMax, GreenMax, BlueMax uint16 // red-, green-, blue-max (2^BPP-1)
RedShift, GreenShift, BlueShift uint8 // red-, green-, blue-shift
_ [3]byte // padding
}
/*
qemu:
*/
/*
*/
const pixelFormatLen = 16
// NewPixelFormat returns a populated PixelFormat structure.
func NewPixelFormat(bpp uint8) *PixelFormat {
bigEndian := uint8(0)
// rgbMax := uint16(math.Exp2(float64(bpp))) - 1
rMax := uint16(255)
gMax := uint16(255)
bMax := uint16(255)
var (
tc = uint8(1)
rs, gs, bs uint8
depth uint8
)
switch bpp {
case 8:
tc = 0
depth = 8
rs, gs, bs = 0, 0, 0
case 16:
depth = 16
rs, gs, bs = 0, 4, 8
case 32:
depth = 24
// rs, gs, bs = 0, 8, 16
rs, gs, bs = 16, 8, 0
}
return &PixelFormat{bpp, depth, bigEndian, tc, rMax, gMax, bMax, rs, gs, bs, [3]byte{}}
}
// Marshal implements the Marshaler interface.
func (pf *PixelFormat) Marshal() ([]byte, error) {
// Validation checks.
switch pf.BPP {
case 8, 16, 32:
default:
return nil, fmt.Errorf("Invalid BPP value %v; must be 8, 16, or 32.", pf.BPP)
}
if pf.Depth < pf.BPP {
return nil, fmt.Errorf("Invalid Depth value %v; cannot be < BPP", pf.Depth)
}
switch pf.Depth {
case 8, 16, 32:
default:
return nil, fmt.Errorf("Invalid Depth value %v; must be 8, 16, or 32.", pf.Depth)
}
// Create the slice of bytes
buf := bPool.Get().(*bytes.Buffer)
buf.Reset()
defer bPool.Put(buf)
if err := binary.Write(buf, binary.BigEndian, &pf); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// Read reads from an io.Reader, and populates the PixelFormat.
func (pf *PixelFormat) Read(r io.Reader) error {
buf := make([]byte, pixelFormatLen)
if _, err := io.ReadAtLeast(r, buf, pixelFormatLen); err != nil {
return err
}
return pf.Unmarshal(buf)
}
// Unmarshal implements the Unmarshaler interface.
func (pf *PixelFormat) Unmarshal(data []byte) error {
buf := bPool.Get().(*bytes.Buffer)
buf.Reset()
defer bPool.Put(buf)
if _, err := buf.Write(data); err != nil {
return err
}
var msg PixelFormat
if err := binary.Read(buf, binary.BigEndian, &msg); err != nil {
return err
}
*pf = msg
return nil
}
// String implements the fmt.Stringer interface.
func (pf *PixelFormat) String() string {
return fmt.Sprintf("{ bpp: %d depth: %d big-endian: %d true-color: %d red-max: %d green-max: %d blue-max: %d red-shift: %d green-shift: %d blue-shift: %d }",
pf.BPP, pf.Depth, pf.BigEndian, pf.TrueColor, pf.RedMax, pf.GreenMax, pf.BlueMax, pf.RedShift, pf.GreenShift, pf.BlueShift)
}
func (pf *PixelFormat) order() binary.ByteOrder {
if pf.BigEndian == 1 {
return binary.BigEndian
}
return binary.LittleEndian
}