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// SPDX-FileCopyrightText: 2022 UnionTech Software Technology Co., Ltd.
//
// SPDX-License-Identifier: GPL-3.0-or-later
package cursor
import (
"bufio"
"encoding/binary"
"errors"
"io"
"os"
)
const (
typeImage = 0xfffd0002
)
type decoder struct {
f *os.File
br *bufio.Reader
version uint32
tocs []tocEntry
tmp [36]byte
}
func newDecoder(f *os.File) (*decoder, error) {
var d decoder
d.f = f
d.br = bufio.NewReader(f)
err := d.readHeader()
if err != nil {
return nil, err
}
return &d, nil
}
func (d *decoder) close() error {
return d.f.Close()
}
// table of contents entry
type tocEntry struct {
Type uint32 // entry type
Subtype uint32 //
Position uint32 // absolute byte position of table in file
}
func readFull(r io.Reader, b []byte) error {
_, err := io.ReadFull(r, b)
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
func (d *decoder) readHeader() error {
err := readFull(d.br, d.tmp[:16])
if err != nil {
return err
}
magic := string(d.tmp[:4])
if magic != "Xcur" {
return errors.New("magic not match")
}
d.version = binary.LittleEndian.Uint32(d.tmp[8:12])
nToc := binary.LittleEndian.Uint32(d.tmp[12:16])
d.tocs = make([]tocEntry, nToc)
for i := range d.tocs {
d.tocs[i], err = d.readTocEntry()
if err != nil {
return err
}
}
return nil
}
func (d *decoder) readTocEntry() (tocEntry, error) {
err := readFull(d.br, d.tmp[:12])
if err != nil {
return tocEntry{}, err
}
var e tocEntry
e.Type = binary.LittleEndian.Uint32(d.tmp[:4])
e.Subtype = binary.LittleEndian.Uint32(d.tmp[4:8])
e.Position = binary.LittleEndian.Uint32(d.tmp[8:12])
return e, nil
}
func (d *decoder) setPos(pos uint32) error {
_, err := d.f.Seek(int64(pos), io.SeekStart)
if err != nil {
return err
}
d.br.Reset(d.f)
return nil
}
func (d *decoder) readImage(toc tocEntry) (*Image, error) {
err := d.setPos(toc.Position)
if err != nil {
return nil, err
}
err = readFull(d.br, d.tmp[:36])
if err != nil {
return nil, err
}
// chuck header
headerLen := binary.LittleEndian.Uint32(d.tmp[:4])
if headerLen != 36 {
return nil, errors.New("image type chunk head len is not 36")
}
type0 := binary.LittleEndian.Uint32(d.tmp[4:8])
if type0 != typeImage {
return nil, errors.New("chunk type not match")
}
subtype := binary.LittleEndian.Uint32(d.tmp[8:12])
version := binary.LittleEndian.Uint32(d.tmp[12:16])
if version != 1 {
return nil, errors.New("version not supported")
}
var img Image
img.Size = subtype
img.Width = binary.LittleEndian.Uint32(d.tmp[16:20])
img.Height = binary.LittleEndian.Uint32(d.tmp[20:24])
img.XHot = binary.LittleEndian.Uint32(d.tmp[24:28])
if img.XHot > img.Width {
img.XHot = img.Width
}
img.YHot = binary.LittleEndian.Uint32(d.tmp[28:32])
if img.YHot > img.Height {
img.YHot = img.Height
}
img.Delay = binary.LittleEndian.Uint32(d.tmp[32:36])
// read pixels
img.Pixels = make([]byte, 4*int(img.Width)*int(img.Height))
err = readFull(d.br, img.Pixels)
if err != nil {
return nil, err
}
return &img, nil
}
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