diff options
Diffstat (limited to 'libgo/go/compress/bzip2/huffman.go')
| -rw-r--r-- | libgo/go/compress/bzip2/huffman.go | 44 |
1 files changed, 28 insertions, 16 deletions
diff --git a/libgo/go/compress/bzip2/huffman.go b/libgo/go/compress/bzip2/huffman.go index 75a6223d813..9d574b9bdef 100644 --- a/libgo/go/compress/bzip2/huffman.go +++ b/libgo/go/compress/bzip2/huffman.go @@ -38,23 +38,35 @@ func (t *huffmanTree) Decode(br *bitReader) (v uint16) { for { node := &t.nodes[nodeIndex] - bit, ok := br.TryReadBit() - if !ok && br.ReadBit() { - bit = 1 - } - // bzip2 encodes left as a true bit. - if bit != 0 { - // left - if node.left == invalidNodeValue { - return node.leftValue - } - nodeIndex = node.left + + var bit uint16 + if br.bits > 0 { + // Get next bit - fast path. + br.bits-- + bit = 0 - (uint16(br.n>>br.bits) & 1) } else { - // right - if node.right == invalidNodeValue { - return node.rightValue - } - nodeIndex = node.right + // Get next bit - slow path. + // Use ReadBits to retrieve a single bit + // from the underling io.ByteReader. + bit = 0 - uint16(br.ReadBits(1)) + } + // now + // bit = 0xffff if the next bit was 1 + // bit = 0x0000 if the next bit was 0 + + // 1 means left, 0 means right. + // + // if bit == 0xffff { + // nodeIndex = node.left + // } else { + // nodeIndex = node.right + // } + nodeIndex = (bit & node.left) | (^bit & node.right) + + if nodeIndex == invalidNodeValue { + // We found a leaf. Use the value of bit to decide + // whether is a left or a right value. + return (bit & node.leftValue) | (^bit & node.rightValue) } } } |