twitchapon-anim

Basic Twitchapon Receiver/Visuals
git clone git://bsandro.tech/twitchapon-anim
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huffman.go (7605B)


      1 // Copyright 2014 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 package vp8l
      6 
      7 import (
      8 	"io"
      9 )
     10 
     11 // reverseBits reverses the bits in a byte.
     12 var reverseBits = [256]uint8{
     13 	0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
     14 	0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
     15 	0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
     16 	0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
     17 	0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
     18 	0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
     19 	0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
     20 	0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
     21 	0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
     22 	0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
     23 	0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
     24 	0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
     25 	0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
     26 	0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
     27 	0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
     28 	0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
     29 }
     30 
     31 // hNode is a node in a Huffman tree.
     32 type hNode struct {
     33 	// symbol is the symbol held by this node.
     34 	symbol uint32
     35 	// children, if positive, is the hTree.nodes index of the first of
     36 	// this node's two children. Zero means an uninitialized node,
     37 	// and -1 means a leaf node.
     38 	children int32
     39 }
     40 
     41 const leafNode = -1
     42 
     43 // lutSize is the log-2 size of an hTree's look-up table.
     44 const lutSize, lutMask = 7, 1<<7 - 1
     45 
     46 // hTree is a Huffman tree.
     47 type hTree struct {
     48 	// nodes are the nodes of the Huffman tree. During construction,
     49 	// len(nodes) grows from 1 up to cap(nodes) by steps of two.
     50 	// After construction, len(nodes) == cap(nodes), and both equal
     51 	// 2*theNumberOfSymbols - 1.
     52 	nodes []hNode
     53 	// lut is a look-up table for walking the nodes. The x in lut[x] is
     54 	// the next lutSize bits in the bit-stream. The low 8 bits of lut[x]
     55 	// equals 1 plus the number of bits in the next code, or 0 if the
     56 	// next code requires more than lutSize bits. The high 24 bits are:
     57 	//   - the symbol, if the code requires lutSize or fewer bits, or
     58 	//   - the hTree.nodes index to start the tree traversal from, if
     59 	//     the next code requires more than lutSize bits.
     60 	lut [1 << lutSize]uint32
     61 }
     62 
     63 // insert inserts into the hTree a symbol whose encoding is the least
     64 // significant codeLength bits of code.
     65 func (h *hTree) insert(symbol uint32, code uint32, codeLength uint32) error {
     66 	if symbol > 0xffff || codeLength > 0xfe {
     67 		return errInvalidHuffmanTree
     68 	}
     69 	baseCode := uint32(0)
     70 	if codeLength > lutSize {
     71 		baseCode = uint32(reverseBits[(code>>(codeLength-lutSize))&0xff]) >> (8 - lutSize)
     72 	} else {
     73 		baseCode = uint32(reverseBits[code&0xff]) >> (8 - codeLength)
     74 		for i := 0; i < 1<<(lutSize-codeLength); i++ {
     75 			h.lut[baseCode|uint32(i)<<codeLength] = symbol<<8 | (codeLength + 1)
     76 		}
     77 	}
     78 
     79 	n := uint32(0)
     80 	for jump := lutSize; codeLength > 0; {
     81 		codeLength--
     82 		if int(n) > len(h.nodes) {
     83 			return errInvalidHuffmanTree
     84 		}
     85 		switch h.nodes[n].children {
     86 		case leafNode:
     87 			return errInvalidHuffmanTree
     88 		case 0:
     89 			if len(h.nodes) == cap(h.nodes) {
     90 				return errInvalidHuffmanTree
     91 			}
     92 			// Create two empty child nodes.
     93 			h.nodes[n].children = int32(len(h.nodes))
     94 			h.nodes = h.nodes[:len(h.nodes)+2]
     95 		}
     96 		n = uint32(h.nodes[n].children) + 1&(code>>codeLength)
     97 		jump--
     98 		if jump == 0 && h.lut[baseCode] == 0 {
     99 			h.lut[baseCode] = n << 8
    100 		}
    101 	}
    102 
    103 	switch h.nodes[n].children {
    104 	case leafNode:
    105 		// No-op.
    106 	case 0:
    107 		// Turn the uninitialized node into a leaf.
    108 		h.nodes[n].children = leafNode
    109 	default:
    110 		return errInvalidHuffmanTree
    111 	}
    112 	h.nodes[n].symbol = symbol
    113 	return nil
    114 }
    115 
    116 // codeLengthsToCodes returns the canonical Huffman codes implied by the
    117 // sequence of code lengths.
    118 func codeLengthsToCodes(codeLengths []uint32) ([]uint32, error) {
    119 	maxCodeLength := uint32(0)
    120 	for _, cl := range codeLengths {
    121 		if maxCodeLength < cl {
    122 			maxCodeLength = cl
    123 		}
    124 	}
    125 	const maxAllowedCodeLength = 15
    126 	if len(codeLengths) == 0 || maxCodeLength > maxAllowedCodeLength {
    127 		return nil, errInvalidHuffmanTree
    128 	}
    129 	histogram := [maxAllowedCodeLength + 1]uint32{}
    130 	for _, cl := range codeLengths {
    131 		histogram[cl]++
    132 	}
    133 	currCode, nextCodes := uint32(0), [maxAllowedCodeLength + 1]uint32{}
    134 	for cl := 1; cl < len(nextCodes); cl++ {
    135 		currCode = (currCode + histogram[cl-1]) << 1
    136 		nextCodes[cl] = currCode
    137 	}
    138 	codes := make([]uint32, len(codeLengths))
    139 	for symbol, cl := range codeLengths {
    140 		if cl > 0 {
    141 			codes[symbol] = nextCodes[cl]
    142 			nextCodes[cl]++
    143 		}
    144 	}
    145 	return codes, nil
    146 }
    147 
    148 // build builds a canonical Huffman tree from the given code lengths.
    149 func (h *hTree) build(codeLengths []uint32) error {
    150 	// Calculate the number of symbols.
    151 	var nSymbols, lastSymbol uint32
    152 	for symbol, cl := range codeLengths {
    153 		if cl != 0 {
    154 			nSymbols++
    155 			lastSymbol = uint32(symbol)
    156 		}
    157 	}
    158 	if nSymbols == 0 {
    159 		return errInvalidHuffmanTree
    160 	}
    161 	h.nodes = make([]hNode, 1, 2*nSymbols-1)
    162 	// Handle the trivial case.
    163 	if nSymbols == 1 {
    164 		if len(codeLengths) <= int(lastSymbol) {
    165 			return errInvalidHuffmanTree
    166 		}
    167 		return h.insert(lastSymbol, 0, 0)
    168 	}
    169 	// Handle the non-trivial case.
    170 	codes, err := codeLengthsToCodes(codeLengths)
    171 	if err != nil {
    172 		return err
    173 	}
    174 	for symbol, cl := range codeLengths {
    175 		if cl > 0 {
    176 			if err := h.insert(uint32(symbol), codes[symbol], cl); err != nil {
    177 				return err
    178 			}
    179 		}
    180 	}
    181 	return nil
    182 }
    183 
    184 // buildSimple builds a Huffman tree with 1 or 2 symbols.
    185 func (h *hTree) buildSimple(nSymbols uint32, symbols [2]uint32, alphabetSize uint32) error {
    186 	h.nodes = make([]hNode, 1, 2*nSymbols-1)
    187 	for i := uint32(0); i < nSymbols; i++ {
    188 		if symbols[i] >= alphabetSize {
    189 			return errInvalidHuffmanTree
    190 		}
    191 		if err := h.insert(symbols[i], i, nSymbols-1); err != nil {
    192 			return err
    193 		}
    194 	}
    195 	return nil
    196 }
    197 
    198 // next returns the next Huffman-encoded symbol from the bit-stream d.
    199 func (h *hTree) next(d *decoder) (uint32, error) {
    200 	var n uint32
    201 	// Read enough bits so that we can use the look-up table.
    202 	if d.nBits < lutSize {
    203 		c, err := d.r.ReadByte()
    204 		if err != nil {
    205 			if err == io.EOF {
    206 				// There are no more bytes of data, but we may still be able
    207 				// to read the next symbol out of the previously read bits.
    208 				goto slowPath
    209 			}
    210 			return 0, err
    211 		}
    212 		d.bits |= uint32(c) << d.nBits
    213 		d.nBits += 8
    214 	}
    215 	// Use the look-up table.
    216 	n = h.lut[d.bits&lutMask]
    217 	if b := n & 0xff; b != 0 {
    218 		b--
    219 		d.bits >>= b
    220 		d.nBits -= b
    221 		return n >> 8, nil
    222 	}
    223 	n >>= 8
    224 	d.bits >>= lutSize
    225 	d.nBits -= lutSize
    226 
    227 slowPath:
    228 	for h.nodes[n].children != leafNode {
    229 		if d.nBits == 0 {
    230 			c, err := d.r.ReadByte()
    231 			if err != nil {
    232 				if err == io.EOF {
    233 					err = io.ErrUnexpectedEOF
    234 				}
    235 				return 0, err
    236 			}
    237 			d.bits = uint32(c)
    238 			d.nBits = 8
    239 		}
    240 		n = uint32(h.nodes[n].children) + 1&d.bits
    241 		d.bits >>= 1
    242 		d.nBits--
    243 	}
    244 	return h.nodes[n].symbol, nil
    245 }