61 lines
1.3 KiB
Go
61 lines
1.3 KiB
Go
// Package rle implements the run-length encoding scheme discovered in Chaos
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// Gate .obj files. It may be used for other data too - to be determined.
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package rle
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import (
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"bufio"
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"io"
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"io/ioutil"
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)
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// Expand converts the compressed input data into uncompressed output data. The
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// output buffer should be of at least the expected size. We will read until
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// io.EOF is encountered.
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func Expand(in io.Reader, out []byte) error {
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buf := bufio.NewReader(in)
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idx := 0
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for {
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b, err := buf.ReadByte()
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if err != nil {
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if err == io.EOF {
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return nil
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}
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return err
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}
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if b == 0x00 { // NOP
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continue
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} else if b < 0x80 { // repeat the next byte this many times
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repeat := b
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value, err := buf.ReadByte()
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if err != nil {
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return err
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}
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for x := 0; x < int(repeat); x++ {
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out[idx+x] = value
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}
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idx = idx + int(repeat)
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} else if b == 0x80 { // skip forward in the output by the next byte's value
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skip, err := buf.ReadByte()
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if err != nil {
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return err
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}
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idx = idx + int(skip)
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} else { // Take the next b-0x80 bytes literally
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lr := io.LimitReader(buf, int64(b-0x80))
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literals, err := ioutil.ReadAll(lr)
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if err != nil {
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return err
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}
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copy(out[idx:], literals)
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idx = idx + len(literals)
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}
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}
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return nil
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}
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