BUGFIX-66

Bug 9: Uncorrected Prediction/Correction Decompressor

This decompressor takes as input a sequence of control bytes and correction bytes.
Each output byte is predicted by using a hash of the preceding output bytes to index a table.
If the next bit in the control byte is set, the prediction is correct and the predicted byte is emitted.
Otherwise, the prediction is incorrect and a correction byte (from the input) is emitted.

Fix The Tiny Bug In This Go Code:

func decompress(from []byte) []byte { const ( order = 3 mixer = 0xff51afd7ed558ccd nbits = 12 ) var ( at = 0 ct = len(from) ctx = uint64(0) lut [1 << nbits]byte to []byte ) for at < ct { ctrl := int(from[at]) for bit := 128; bit != 0; bit >>= 1 { var next byte hash := ctx * mixer hash >>= 64 - nbits if ctrl&bit == 0 { if at == ct { return to } next = from[at] at++ lut[hash] = next } else { next = lut[hash] } ctx <<= 8 ctx += uint64(next) ctx &= 1<<(order*8) - 1 to = append(to, next) } } return to }

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