ml
68 lines
1.6 KiB
Go
68 lines
1.6 KiB
Go
package rle
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import (
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"io"
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"github.com/inkyblackness/hacked/ss1"
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)
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const (
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errUndefinedCase ss1.StringError = "undefined case 80 nn C0"
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)
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// Decompress decompresses from the given reader and writes into the provided output buffer.
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// The output buffer must be pre-allocated.
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// If it contains non-zero data, this data may be preserved if the compressed data specifies to.
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func Decompress(reader io.Reader, output []byte) (err error) {
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outIndex := 0
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done := false
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nextByte := func() byte {
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zz := []byte{0x00}
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_, err = reader.Read(zz)
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return zz[0]
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}
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for !done && (err == nil) {
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first := nextByte()
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switch {
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case first == 0x00:
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nn := nextByte()
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zz := nextByte()
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outIndex += writeBytesOfValue(output[outIndex:outIndex+int(nn)], func() byte { return zz })
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case first < 0x80:
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outIndex += writeBytesOfValue(output[outIndex:outIndex+int(first)], nextByte)
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case first == 0x80:
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control := uint16(nextByte())
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control += uint16(nextByte()) << 8
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switch {
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case control == 0x0000:
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done = true
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case control < 0x8000:
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outIndex += int(control)
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case control < 0xC000:
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outIndex += writeBytesOfValue(output[outIndex:outIndex+int(control&0x3FFF)], nextByte)
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case (control & 0xFF00) == 0xC000:
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err = errUndefinedCase
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default:
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zz := nextByte()
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outIndex += writeBytesOfValue(output[outIndex:outIndex+int(control&0x3FFF)], func() byte { return zz })
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}
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default:
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outIndex += int(first & 0x7F)
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}
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}
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return
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}
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func writeBytesOfValue(buffer []byte, producer func() byte) int {
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count := len(buffer)
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for i := 0; i < count; i++ {
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buffer[i] = producer()
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}
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return count
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}
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