source: code/trunk/vendor/github.com/andybalholm/brotli/brotli_bit_stream.go@ 145

package brotli

import (
        "math"
        "sync"
)

const maxHuffmanTreeSize = (2*numCommandSymbols + 1)

/* The maximum size of Huffman dictionary for distances assuming that
   NPOSTFIX = 0 and NDIRECT = 0. */
const maxSimpleDistanceAlphabetSize = 140

/* Represents the range of values belonging to a prefix code:
   [offset, offset + 2^nbits) */
type prefixCodeRange struct {
        offset uint32
        nbits  uint32
}

var kBlockLengthPrefixCode = [numBlockLenSymbols]prefixCodeRange{
        prefixCodeRange{1, 2},
        prefixCodeRange{5, 2},
        prefixCodeRange{9, 2},
        prefixCodeRange{13, 2},
        prefixCodeRange{17, 3},
        prefixCodeRange{25, 3},
        prefixCodeRange{33, 3},
        prefixCodeRange{41, 3},
        prefixCodeRange{49, 4},
        prefixCodeRange{65, 4},
        prefixCodeRange{81, 4},
        prefixCodeRange{97, 4},
        prefixCodeRange{113, 5},
        prefixCodeRange{145, 5},
        prefixCodeRange{177, 5},
        prefixCodeRange{209, 5},
        prefixCodeRange{241, 6},
        prefixCodeRange{305, 6},
        prefixCodeRange{369, 7},
        prefixCodeRange{497, 8},
        prefixCodeRange{753, 9},
        prefixCodeRange{1265, 10},
        prefixCodeRange{2289, 11},
        prefixCodeRange{4337, 12},
        prefixCodeRange{8433, 13},
        prefixCodeRange{16625, 24},
}

func blockLengthPrefixCode(len uint32) uint32 {
        var code uint32
        if len >= 177 {
                if len >= 753 {
                        code = 20
                } else {
                        code = 14
                }
        } else if len >= 41 {
                code = 7
        } else {
                code = 0
        }
        for code < (numBlockLenSymbols-1) && len >= kBlockLengthPrefixCode[code+1].offset {
                code++
        }
        return code
}

func getBlockLengthPrefixCode(len uint32, code *uint, n_extra *uint32, extra *uint32) {
        *code = uint(blockLengthPrefixCode(uint32(len)))
        *n_extra = kBlockLengthPrefixCode[*code].nbits
        *extra = len - kBlockLengthPrefixCode[*code].offset
}

type blockTypeCodeCalculator struct {
        last_type        uint
        second_last_type uint
}

func initBlockTypeCodeCalculator(self *blockTypeCodeCalculator) {
        self.last_type = 1
        self.second_last_type = 0
}

func nextBlockTypeCode(calculator *blockTypeCodeCalculator, type_ byte) uint {
        var type_code uint
        if uint(type_) == calculator.last_type+1 {
                type_code = 1
        } else if uint(type_) == calculator.second_last_type {
                type_code = 0
        } else {
                type_code = uint(type_) + 2
        }
        calculator.second_last_type = calculator.last_type
        calculator.last_type = uint(type_)
        return type_code
}

/* |nibblesbits| represents the 2 bits to encode MNIBBLES (0-3)
   REQUIRES: length > 0
   REQUIRES: length <= (1 << 24) */
func encodeMlen(length uint, bits *uint64, numbits *uint, nibblesbits *uint64) {
        var lg uint
        if length == 1 {
                lg = 1
        } else {
                lg = uint(log2FloorNonZero(uint(uint32(length-1)))) + 1
        }
        var tmp uint
        if lg < 16 {
                tmp = 16
        } else {
                tmp = (lg + 3)
        }
        var mnibbles uint = tmp / 4
        assert(length > 0)
        assert(length <= 1<<24)
        assert(lg <= 24)
        *nibblesbits = uint64(mnibbles) - 4
        *numbits = mnibbles * 4
        *bits = uint64(length) - 1
}

func storeCommandExtra(cmd *command, storage_ix *uint, storage []byte) {
        var copylen_code uint32 = commandCopyLenCode(cmd)
        var inscode uint16 = getInsertLengthCode(uint(cmd.insert_len_))
        var copycode uint16 = getCopyLengthCode(uint(copylen_code))
        var insnumextra uint32 = getInsertExtra(inscode)
        var insextraval uint64 = uint64(cmd.insert_len_) - uint64(getInsertBase(inscode))
        var copyextraval uint64 = uint64(copylen_code) - uint64(getCopyBase(copycode))
        var bits uint64 = copyextraval<<insnumextra | insextraval
        writeBits(uint(insnumextra+getCopyExtra(copycode)), bits, storage_ix, storage)
}

/* Data structure that stores almost everything that is needed to encode each
   block switch command. */
type blockSplitCode struct {
        type_code_calculator blockTypeCodeCalculator
        type_depths          [maxBlockTypeSymbols]byte
        type_bits            [maxBlockTypeSymbols]uint16
        length_depths        [numBlockLenSymbols]byte
        length_bits          [numBlockLenSymbols]uint16
}

/* Stores a number between 0 and 255. */
func storeVarLenUint8(n uint, storage_ix *uint, storage []byte) {
        if n == 0 {
                writeBits(1, 0, storage_ix, storage)
        } else {
                var nbits uint = uint(log2FloorNonZero(n))
                writeBits(1, 1, storage_ix, storage)
                writeBits(3, uint64(nbits), storage_ix, storage)
                writeBits(nbits, uint64(n)-(uint64(uint(1))<<nbits), storage_ix, storage)
        }
}

/* Stores the compressed meta-block header.
   REQUIRES: length > 0
   REQUIRES: length <= (1 << 24) */
func storeCompressedMetaBlockHeader(is_final_block bool, length uint, storage_ix *uint, storage []byte) {
        var lenbits uint64
        var nlenbits uint
        var nibblesbits uint64
        var is_final uint64
        if is_final_block {
                is_final = 1
        } else {
                is_final = 0
        }

        /* Write ISLAST bit. */
        writeBits(1, is_final, storage_ix, storage)

        /* Write ISEMPTY bit. */
        if is_final_block {
                writeBits(1, 0, storage_ix, storage)
        }

        encodeMlen(length, &lenbits, &nlenbits, &nibblesbits)
        writeBits(2, nibblesbits, storage_ix, storage)
        writeBits(nlenbits, lenbits, storage_ix, storage)

        if !is_final_block {
                /* Write ISUNCOMPRESSED bit. */
                writeBits(1, 0, storage_ix, storage)
        }
}

/* Stores the uncompressed meta-block header.
   REQUIRES: length > 0
   REQUIRES: length <= (1 << 24) */
func storeUncompressedMetaBlockHeader(length uint, storage_ix *uint, storage []byte) {
        var lenbits uint64
        var nlenbits uint
        var nibblesbits uint64

        /* Write ISLAST bit.
           Uncompressed block cannot be the last one, so set to 0. */
        writeBits(1, 0, storage_ix, storage)

        encodeMlen(length, &lenbits, &nlenbits, &nibblesbits)
        writeBits(2, nibblesbits, storage_ix, storage)
        writeBits(nlenbits, lenbits, storage_ix, storage)

        /* Write ISUNCOMPRESSED bit. */
        writeBits(1, 1, storage_ix, storage)
}

var storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder = [codeLengthCodes]byte{1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15}

var storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeSymbols = [6]byte{0, 7, 3, 2, 1, 15}
var storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeBitLengths = [6]byte{2, 4, 3, 2, 2, 4}

func storeHuffmanTreeOfHuffmanTreeToBitMask(num_codes int, code_length_bitdepth []byte, storage_ix *uint, storage []byte) {
        var skip_some uint = 0
        var codes_to_store uint = codeLengthCodes
        /* The bit lengths of the Huffman code over the code length alphabet
           are compressed with the following static Huffman code:
             Symbol   Code
             ------   ----
             0          00
             1        1110
             2         110
             3          01
             4          10
             5        1111 */

        /* Throw away trailing zeros: */
        if num_codes > 1 {
                for ; codes_to_store > 0; codes_to_store-- {
                        if code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[codes_to_store-1]] != 0 {
                                break
                        }
                }
        }

        if code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[0]] == 0 && code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[1]] == 0 {
                skip_some = 2 /* skips two. */
                if code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[2]] == 0 {
                        skip_some = 3 /* skips three. */
                }
        }

        writeBits(2, uint64(skip_some), storage_ix, storage)
        {
                var i uint
                for i = skip_some; i < codes_to_store; i++ {
                        var l uint = uint(code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[i]])
                        writeBits(uint(storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeBitLengths[l]), uint64(storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeSymbols[l]), storage_ix, storage)
                }
        }
}

func storeHuffmanTreeToBitMask(huffman_tree_size uint, huffman_tree []byte, huffman_tree_extra_bits []byte, code_length_bitdepth []byte, code_length_bitdepth_symbols []uint16, storage_ix *uint, storage []byte) {
        var i uint
        for i = 0; i < huffman_tree_size; i++ {
                var ix uint = uint(huffman_tree[i])
                writeBits(uint(code_length_bitdepth[ix]), uint64(code_length_bitdepth_symbols[ix]), storage_ix, storage)

                /* Extra bits */
                switch ix {
                case repeatPreviousCodeLength:
                        writeBits(2, uint64(huffman_tree_extra_bits[i]), storage_ix, storage)

                case repeatZeroCodeLength:
                        writeBits(3, uint64(huffman_tree_extra_bits[i]), storage_ix, storage)
                }
        }
}

func storeSimpleHuffmanTree(depths []byte, symbols []uint, num_symbols uint, max_bits uint, storage_ix *uint, storage []byte) {
        /* value of 1 indicates a simple Huffman code */
        writeBits(2, 1, storage_ix, storage)

        writeBits(2, uint64(num_symbols)-1, storage_ix, storage) /* NSYM - 1 */
        {
                /* Sort */
                var i uint
                for i = 0; i < num_symbols; i++ {
                        var j uint
                        for j = i + 1; j < num_symbols; j++ {
                                if depths[symbols[j]] < depths[symbols[i]] {
                                        var tmp uint = symbols[j]
                                        symbols[j] = symbols[i]
                                        symbols[i] = tmp
                                }
                        }
                }
        }

        if num_symbols == 2 {
                writeBits(max_bits, uint64(symbols[0]), storage_ix, storage)
                writeBits(max_bits, uint64(symbols[1]), storage_ix, storage)
        } else if num_symbols == 3 {
                writeBits(max_bits, uint64(symbols[0]), storage_ix, storage)
                writeBits(max_bits, uint64(symbols[1]), storage_ix, storage)
                writeBits(max_bits, uint64(symbols[2]), storage_ix, storage)
        } else {
                writeBits(max_bits, uint64(symbols[0]), storage_ix, storage)
                writeBits(max_bits, uint64(symbols[1]), storage_ix, storage)
                writeBits(max_bits, uint64(symbols[2]), storage_ix, storage)
                writeBits(max_bits, uint64(symbols[3]), storage_ix, storage)

                /* tree-select */
                var tmp int
                if depths[symbols[0]] == 1 {
                        tmp = 1
                } else {
                        tmp = 0
                }
                writeBits(1, uint64(tmp), storage_ix, storage)
        }
}

/* num = alphabet size
   depths = symbol depths */
func storeHuffmanTree(depths []byte, num uint, tree []huffmanTree, storage_ix *uint, storage []byte) {
        var huffman_tree [numCommandSymbols]byte
        var huffman_tree_extra_bits [numCommandSymbols]byte
        var huffman_tree_size uint = 0
        var code_length_bitdepth = [codeLengthCodes]byte{0}
        var code_length_bitdepth_symbols [codeLengthCodes]uint16
        var huffman_tree_histogram = [codeLengthCodes]uint32{0}
        var i uint
        var num_codes int = 0
        /* Write the Huffman tree into the brotli-representation.
           The command alphabet is the largest, so this allocation will fit all
           alphabets. */

        var code uint = 0

        assert(num <= numCommandSymbols)

        writeHuffmanTree(depths, num, &huffman_tree_size, huffman_tree[:], huffman_tree_extra_bits[:])

        /* Calculate the statistics of the Huffman tree in brotli-representation. */
        for i = 0; i < huffman_tree_size; i++ {
                huffman_tree_histogram[huffman_tree[i]]++
        }

        for i = 0; i < codeLengthCodes; i++ {
                if huffman_tree_histogram[i] != 0 {
                        if num_codes == 0 {
                                code = i
                                num_codes = 1
                        } else if num_codes == 1 {
                                num_codes = 2
                                break
                        }
                }
        }

        /* Calculate another Huffman tree to use for compressing both the
           earlier Huffman tree with. */
        createHuffmanTree(huffman_tree_histogram[:], codeLengthCodes, 5, tree, code_length_bitdepth[:])

        convertBitDepthsToSymbols(code_length_bitdepth[:], codeLengthCodes, code_length_bitdepth_symbols[:])

        /* Now, we have all the data, let's start storing it */
        storeHuffmanTreeOfHuffmanTreeToBitMask(num_codes, code_length_bitdepth[:], storage_ix, storage)

        if num_codes == 1 {
                code_length_bitdepth[code] = 0
        }

        /* Store the real Huffman tree now. */
        storeHuffmanTreeToBitMask(huffman_tree_size, huffman_tree[:], huffman_tree_extra_bits[:], code_length_bitdepth[:], code_length_bitdepth_symbols[:], storage_ix, storage)
}

/* Builds a Huffman tree from histogram[0:length] into depth[0:length] and
   bits[0:length] and stores the encoded tree to the bit stream. */
func buildAndStoreHuffmanTree(histogram []uint32, histogram_length uint, alphabet_size uint, tree []huffmanTree, depth []byte, bits []uint16, storage_ix *uint, storage []byte) {
        var count uint = 0
        var s4 = [4]uint{0}
        var i uint
        var max_bits uint = 0
        for i = 0; i < histogram_length; i++ {
                if histogram[i] != 0 {
                        if count < 4 {
                                s4[count] = i
                        } else if count > 4 {
                                break
                        }

                        count++
                }
        }
        {
                var max_bits_counter uint = alphabet_size - 1
                for max_bits_counter != 0 {
                        max_bits_counter >>= 1
                        max_bits++
                }
        }

        if count <= 1 {
                writeBits(4, 1, storage_ix, storage)
                writeBits(max_bits, uint64(s4[0]), storage_ix, storage)
                depth[s4[0]] = 0
                bits[s4[0]] = 0
                return
        }

        for i := 0; i < int(histogram_length); i++ {
                depth[i] = 0
        }
        createHuffmanTree(histogram, histogram_length, 15, tree, depth)
        convertBitDepthsToSymbols(depth, histogram_length, bits)

        if count <= 4 {
                storeSimpleHuffmanTree(depth, s4[:], count, max_bits, storage_ix, storage)
        } else {
                storeHuffmanTree(depth, histogram_length, tree, storage_ix, storage)
        }
}

func sortHuffmanTree1(v0 huffmanTree, v1 huffmanTree) bool {
        return v0.total_count_ < v1.total_count_
}

var huffmanTreePool sync.Pool

func buildAndStoreHuffmanTreeFast(histogram []uint32, histogram_total uint, max_bits uint, depth []byte, bits []uint16, storage_ix *uint, storage []byte) {
        var count uint = 0
        var symbols = [4]uint{0}
        var length uint = 0
        var total uint = histogram_total
        for total != 0 {
                if histogram[length] != 0 {
                        if count < 4 {
                                symbols[count] = length
                        }

                        count++
                        total -= uint(histogram[length])
                }

                length++
        }

        if count <= 1 {
                writeBits(4, 1, storage_ix, storage)
                writeBits(max_bits, uint64(symbols[0]), storage_ix, storage)
                depth[symbols[0]] = 0
                bits[symbols[0]] = 0
                return
        }

        for i := 0; i < int(length); i++ {
                depth[i] = 0
        }
        {
                var max_tree_size uint = 2*length + 1
                tree, _ := huffmanTreePool.Get().(*[]huffmanTree)
                if tree == nil || cap(*tree) < int(max_tree_size) {
                        tmp := make([]huffmanTree, max_tree_size)
                        tree = &tmp
                } else {
                        *tree = (*tree)[:max_tree_size]
                }
                var count_limit uint32
                for count_limit = 1; ; count_limit *= 2 {
                        var node int = 0
                        var l uint
                        for l = length; l != 0; {
                                l--
                                if histogram[l] != 0 {
                                        if histogram[l] >= count_limit {
                                                initHuffmanTree(&(*tree)[node:][0], histogram[l], -1, int16(l))
                                        } else {
                                                initHuffmanTree(&(*tree)[node:][0], count_limit, -1, int16(l))
                                        }

                                        node++
                                }
                        }
                        {
                                var n int = node
                                /* Points to the next leaf node. */ /* Points to the next non-leaf node. */
                                var sentinel huffmanTree
                                var i int = 0
                                var j int = n + 1
                                var k int

                                sortHuffmanTreeItems(*tree, uint(n), huffmanTreeComparator(sortHuffmanTree1))

                                /* The nodes are:
                                   [0, n): the sorted leaf nodes that we start with.
                                   [n]: we add a sentinel here.
                                   [n + 1, 2n): new parent nodes are added here, starting from
                                                (n+1). These are naturally in ascending order.
                                   [2n]: we add a sentinel at the end as well.
                                   There will be (2n+1) elements at the end. */
                                initHuffmanTree(&sentinel, math.MaxUint32, -1, -1)

                                (*tree)[node] = sentinel
                                node++
                                (*tree)[node] = sentinel
                                node++

                                for k = n - 1; k > 0; k-- {
                                        var left int
                                        var right int
                                        if (*tree)[i].total_count_ <= (*tree)[j].total_count_ {
                                                left = i
                                                i++
                                        } else {
                                                left = j
                                                j++
                                        }

                                        if (*tree)[i].total_count_ <= (*tree)[j].total_count_ {
                                                right = i
                                                i++
                                        } else {
                                                right = j
                                                j++
                                        }

                                        /* The sentinel node becomes the parent node. */
                                        (*tree)[node-1].total_count_ = (*tree)[left].total_count_ + (*tree)[right].total_count_

                                        (*tree)[node-1].index_left_ = int16(left)
                                        (*tree)[node-1].index_right_or_value_ = int16(right)

                                        /* Add back the last sentinel node. */
                                        (*tree)[node] = sentinel
                                        node++
                                }

                                if setDepth(2*n-1, *tree, depth, 14) {
                                        /* We need to pack the Huffman tree in 14 bits. If this was not
                                           successful, add fake entities to the lowest values and retry. */
                                        break
                                }
                        }
                }

                huffmanTreePool.Put(tree)
        }

        convertBitDepthsToSymbols(depth, length, bits)
        if count <= 4 {
                var i uint

                /* value of 1 indicates a simple Huffman code */
                writeBits(2, 1, storage_ix, storage)

                writeBits(2, uint64(count)-1, storage_ix, storage) /* NSYM - 1 */

                /* Sort */
                for i = 0; i < count; i++ {
                        var j uint
                        for j = i + 1; j < count; j++ {
                                if depth[symbols[j]] < depth[symbols[i]] {
                                        var tmp uint = symbols[j]
                                        symbols[j] = symbols[i]
                                        symbols[i] = tmp
                                }
                        }
                }

                if count == 2 {
                        writeBits(max_bits, uint64(symbols[0]), storage_ix, storage)
                        writeBits(max_bits, uint64(symbols[1]), storage_ix, storage)
                } else if count == 3 {
                        writeBits(max_bits, uint64(symbols[0]), storage_ix, storage)
                        writeBits(max_bits, uint64(symbols[1]), storage_ix, storage)
                        writeBits(max_bits, uint64(symbols[2]), storage_ix, storage)
                } else {
                        writeBits(max_bits, uint64(symbols[0]), storage_ix, storage)
                        writeBits(max_bits, uint64(symbols[1]), storage_ix, storage)
                        writeBits(max_bits, uint64(symbols[2]), storage_ix, storage)
                        writeBits(max_bits, uint64(symbols[3]), storage_ix, storage)

                        /* tree-select */
                        var tmp int
                        if depth[symbols[0]] == 1 {
                                tmp = 1
                        } else {
                                tmp = 0
                        }
                        writeBits(1, uint64(tmp), storage_ix, storage)
                }
        } else {
                var previous_value byte = 8
                var i uint

                /* Complex Huffman Tree */
                storeStaticCodeLengthCode(storage_ix, storage)

                /* Actual RLE coding. */
                for i = 0; i < length; {
                        var value byte = depth[i]
                        var reps uint = 1
                        var k uint
                        for k = i + 1; k < length && depth[k] == value; k++ {
                                reps++
                        }

                        i += reps
                        if value == 0 {
                                writeBits(uint(kZeroRepsDepth[reps]), kZeroRepsBits[reps], storage_ix, storage)
                        } else {
                                if previous_value != value {
                                        writeBits(uint(kCodeLengthDepth[value]), uint64(kCodeLengthBits[value]), storage_ix, storage)
                                        reps--
                                }

                                if reps < 3 {
                                        for reps != 0 {
                                                reps--
                                                writeBits(uint(kCodeLengthDepth[value]), uint64(kCodeLengthBits[value]), storage_ix, storage)
                                        }
                                } else {
                                        reps -= 3
                                        writeBits(uint(kNonZeroRepsDepth[reps]), kNonZeroRepsBits[reps], storage_ix, storage)
                                }

                                previous_value = value
                        }
                }
        }
}

func indexOf(v []byte, v_size uint, value byte) uint {
        var i uint = 0
        for ; i < v_size; i++ {
                if v[i] == value {
                        return i
                }
        }

        return i
}

func moveToFront(v []byte, index uint) {
        var value byte = v[index]
        var i uint
        for i = index; i != 0; i-- {
                v[i] = v[i-1]
        }

        v[0] = value
}

func moveToFrontTransform(v_in []uint32, v_size uint, v_out []uint32) {
        var i uint
        var mtf [256]byte
        var max_value uint32
        if v_size == 0 {
                return
        }

        max_value = v_in[0]
        for i = 1; i < v_size; i++ {
                if v_in[i] > max_value {
                        max_value = v_in[i]
                }
        }

        assert(max_value < 256)
        for i = 0; uint32(i) <= max_value; i++ {
                mtf[i] = byte(i)
        }
        {
                var mtf_size uint = uint(max_value + 1)
                for i = 0; i < v_size; i++ {
                        var index uint = indexOf(mtf[:], mtf_size, byte(v_in[i]))
                        assert(index < mtf_size)
                        v_out[i] = uint32(index)
                        moveToFront(mtf[:], index)
                }
        }
}

/* Finds runs of zeros in v[0..in_size) and replaces them with a prefix code of
   the run length plus extra bits (lower 9 bits is the prefix code and the rest
   are the extra bits). Non-zero values in v[] are shifted by
   *max_length_prefix. Will not create prefix codes bigger than the initial
   value of *max_run_length_prefix. The prefix code of run length L is simply
   Log2Floor(L) and the number of extra bits is the same as the prefix code. */
func runLengthCodeZeros(in_size uint, v []uint32, out_size *uint, max_run_length_prefix *uint32) {
        var max_reps uint32 = 0
        var i uint
        var max_prefix uint32
        for i = 0; i < in_size; {
                var reps uint32 = 0
                for ; i < in_size && v[i] != 0; i++ {
                }
                for ; i < in_size && v[i] == 0; i++ {
                        reps++
                }

                max_reps = brotli_max_uint32_t(reps, max_reps)
        }

        if max_reps > 0 {
                max_prefix = log2FloorNonZero(uint(max_reps))
        } else {
                max_prefix = 0
        }
        max_prefix = brotli_min_uint32_t(max_prefix, *max_run_length_prefix)
        *max_run_length_prefix = max_prefix
        *out_size = 0
        for i = 0; i < in_size; {
                assert(*out_size <= i)
                if v[i] != 0 {
                        v[*out_size] = v[i] + *max_run_length_prefix
                        i++
                        (*out_size)++
                } else {
                        var reps uint32 = 1
                        var k uint
                        for k = i + 1; k < in_size && v[k] == 0; k++ {
                                reps++
                        }

                        i += uint(reps)
                        for reps != 0 {
                                if reps < 2<<max_prefix {
                                        var run_length_prefix uint32 = log2FloorNonZero(uint(reps))
                                        var extra_bits uint32 = reps - (1 << run_length_prefix)
                                        v[*out_size] = run_length_prefix + (extra_bits << 9)
                                        (*out_size)++
                                        break
                                } else {
                                        var extra_bits uint32 = (1 << max_prefix) - 1
                                        v[*out_size] = max_prefix + (extra_bits << 9)
                                        reps -= (2 << max_prefix) - 1
                                        (*out_size)++
                                }
                        }
                }
        }
}

const symbolBits = 9

var encodeContextMap_kSymbolMask uint32 = (1 << symbolBits) - 1

func encodeContextMap(context_map []uint32, context_map_size uint, num_clusters uint, tree []huffmanTree, storage_ix *uint, storage []byte) {
        var i uint
        var rle_symbols []uint32
        var max_run_length_prefix uint32 = 6
        var num_rle_symbols uint = 0
        var histogram [maxContextMapSymbols]uint32
        var depths [maxContextMapSymbols]byte
        var bits [maxContextMapSymbols]uint16

        storeVarLenUint8(num_clusters-1, storage_ix, storage)

        if num_clusters == 1 {
                return
        }

        rle_symbols = make([]uint32, context_map_size)
        moveToFrontTransform(context_map, context_map_size, rle_symbols)
        runLengthCodeZeros(context_map_size, rle_symbols, &num_rle_symbols, &max_run_length_prefix)
        histogram = [maxContextMapSymbols]uint32{}
        for i = 0; i < num_rle_symbols; i++ {
                histogram[rle_symbols[i]&encodeContextMap_kSymbolMask]++
        }
        {
                var use_rle bool = (max_run_length_prefix > 0)
                writeSingleBit(use_rle, storage_ix, storage)
                if use_rle {
                        writeBits(4, uint64(max_run_length_prefix)-1, storage_ix, storage)
                }
        }

        buildAndStoreHuffmanTree(histogram[:], uint(uint32(num_clusters)+max_run_length_prefix), uint(uint32(num_clusters)+max_run_length_prefix), tree, depths[:], bits[:], storage_ix, storage)
        for i = 0; i < num_rle_symbols; i++ {
                var rle_symbol uint32 = rle_symbols[i] & encodeContextMap_kSymbolMask
                var extra_bits_val uint32 = rle_symbols[i] >> symbolBits
                writeBits(uint(depths[rle_symbol]), uint64(bits[rle_symbol]), storage_ix, storage)
                if rle_symbol > 0 && rle_symbol <= max_run_length_prefix {
                        writeBits(uint(rle_symbol), uint64(extra_bits_val), storage_ix, storage)
                }
        }

        writeBits(1, 1, storage_ix, storage) /* use move-to-front */
        rle_symbols = nil
}

/* Stores the block switch command with index block_ix to the bit stream. */
func storeBlockSwitch(code *blockSplitCode, block_len uint32, block_type byte, is_first_block bool, storage_ix *uint, storage []byte) {
        var typecode uint = nextBlockTypeCode(&code.type_code_calculator, block_type)
        var lencode uint
        var len_nextra uint32
        var len_extra uint32
        if !is_first_block {
                writeBits(uint(code.type_depths[typecode]), uint64(code.type_bits[typecode]), storage_ix, storage)
        }

        getBlockLengthPrefixCode(block_len, &lencode, &len_nextra, &len_extra)

        writeBits(uint(code.length_depths[lencode]), uint64(code.length_bits[lencode]), storage_ix, storage)
        writeBits(uint(len_nextra), uint64(len_extra), storage_ix, storage)
}

/* Builds a BlockSplitCode data structure from the block split given by the
   vector of block types and block lengths and stores it to the bit stream. */
func buildAndStoreBlockSplitCode(types []byte, lengths []uint32, num_blocks uint, num_types uint, tree []huffmanTree, code *blockSplitCode, storage_ix *uint, storage []byte) {
        var type_histo [maxBlockTypeSymbols]uint32
        var length_histo [numBlockLenSymbols]uint32
        var i uint
        var type_code_calculator blockTypeCodeCalculator
        for i := 0; i < int(num_types+2); i++ {
                type_histo[i] = 0
        }
        length_histo = [numBlockLenSymbols]uint32{}
        initBlockTypeCodeCalculator(&type_code_calculator)
        for i = 0; i < num_blocks; i++ {
                var type_code uint = nextBlockTypeCode(&type_code_calculator, types[i])
                if i != 0 {
                        type_histo[type_code]++
                }
                length_histo[blockLengthPrefixCode(lengths[i])]++
        }

        storeVarLenUint8(num_types-1, storage_ix, storage)
        if num_types > 1 { /* TODO: else? could StoreBlockSwitch occur? */
                buildAndStoreHuffmanTree(type_histo[0:], num_types+2, num_types+2, tree, code.type_depths[0:], code.type_bits[0:], storage_ix, storage)
                buildAndStoreHuffmanTree(length_histo[0:], numBlockLenSymbols, numBlockLenSymbols, tree, code.length_depths[0:], code.length_bits[0:], storage_ix, storage)
                storeBlockSwitch(code, lengths[0], types[0], true, storage_ix, storage)
        }
}

/* Stores a context map where the histogram type is always the block type. */
func storeTrivialContextMap(num_types uint, context_bits uint, tree []huffmanTree, storage_ix *uint, storage []byte) {
        storeVarLenUint8(num_types-1, storage_ix, storage)
        if num_types > 1 {
                var repeat_code uint = context_bits - 1
                var repeat_bits uint = (1 << repeat_code) - 1
                var alphabet_size uint = num_types + repeat_code
                var histogram [maxContextMapSymbols]uint32
                var depths [maxContextMapSymbols]byte
                var bits [maxContextMapSymbols]uint16
                var i uint
                for i := 0; i < int(alphabet_size); i++ {
                        histogram[i] = 0
                }

                /* Write RLEMAX. */
                writeBits(1, 1, storage_ix, storage)

                writeBits(4, uint64(repeat_code)-1, storage_ix, storage)
                histogram[repeat_code] = uint32(num_types)
                histogram[0] = 1
                for i = context_bits; i < alphabet_size; i++ {
                        histogram[i] = 1
                }

                buildAndStoreHuffmanTree(histogram[:], alphabet_size, alphabet_size, tree, depths[:], bits[:], storage_ix, storage)
                for i = 0; i < num_types; i++ {
                        var tmp uint
                        if i == 0 {
                                tmp = 0
                        } else {
                                tmp = i + context_bits - 1
                        }
                        var code uint = tmp
                        writeBits(uint(depths[code]), uint64(bits[code]), storage_ix, storage)
                        writeBits(uint(depths[repeat_code]), uint64(bits[repeat_code]), storage_ix, storage)
                        writeBits(repeat_code, uint64(repeat_bits), storage_ix, storage)
                }

                /* Write IMTF (inverse-move-to-front) bit. */
                writeBits(1, 1, storage_ix, storage)
        }
}

/* Manages the encoding of one block category (literal, command or distance). */
type blockEncoder struct {
        histogram_length_ uint
        num_block_types_  uint
        block_types_      []byte
        block_lengths_    []uint32
        num_blocks_       uint
        block_split_code_ blockSplitCode
        block_ix_         uint
        block_len_        uint
        entropy_ix_       uint
        depths_           []byte
        bits_             []uint16
}

var blockEncoderPool sync.Pool

func getBlockEncoder(histogram_length uint, num_block_types uint, block_types []byte, block_lengths []uint32, num_blocks uint) *blockEncoder {
        self, _ := blockEncoderPool.Get().(*blockEncoder)

        if self != nil {
                self.block_ix_ = 0
                self.entropy_ix_ = 0
                self.depths_ = self.depths_[:0]
                self.bits_ = self.bits_[:0]
        } else {
                self = &blockEncoder{}
        }

        self.histogram_length_ = histogram_length
        self.num_block_types_ = num_block_types
        self.block_types_ = block_types
        self.block_lengths_ = block_lengths
        self.num_blocks_ = num_blocks
        initBlockTypeCodeCalculator(&self.block_split_code_.type_code_calculator)
        if num_blocks == 0 {
                self.block_len_ = 0
        } else {
                self.block_len_ = uint(block_lengths[0])
        }

        return self
}

func cleanupBlockEncoder(self *blockEncoder) {
        blockEncoderPool.Put(self)
}

/* Creates entropy codes of block lengths and block types and stores them
   to the bit stream. */
func buildAndStoreBlockSwitchEntropyCodes(self *blockEncoder, tree []huffmanTree, storage_ix *uint, storage []byte) {
        buildAndStoreBlockSplitCode(self.block_types_, self.block_lengths_, self.num_blocks_, self.num_block_types_, tree, &self.block_split_code_, storage_ix, storage)
}

/* Stores the next symbol with the entropy code of the current block type.
   Updates the block type and block length at block boundaries. */
func storeSymbol(self *blockEncoder, symbol uint, storage_ix *uint, storage []byte) {
        if self.block_len_ == 0 {
                self.block_ix_++
                var block_ix uint = self.block_ix_
                var block_len uint32 = self.block_lengths_[block_ix]
                var block_type byte = self.block_types_[block_ix]
                self.block_len_ = uint(block_len)
                self.entropy_ix_ = uint(block_type) * self.histogram_length_
                storeBlockSwitch(&self.block_split_code_, block_len, block_type, false, storage_ix, storage)
        }

        self.block_len_--
        {
                var ix uint = self.entropy_ix_ + symbol
                writeBits(uint(self.depths_[ix]), uint64(self.bits_[ix]), storage_ix, storage)
        }
}

/* Stores the next symbol with the entropy code of the current block type and
   context value.
   Updates the block type and block length at block boundaries. */
func storeSymbolWithContext(self *blockEncoder, symbol uint, context uint, context_map []uint32, storage_ix *uint, storage []byte, context_bits uint) {
        if self.block_len_ == 0 {
                self.block_ix_++
                var block_ix uint = self.block_ix_
                var block_len uint32 = self.block_lengths_[block_ix]
                var block_type byte = self.block_types_[block_ix]
                self.block_len_ = uint(block_len)
                self.entropy_ix_ = uint(block_type) << context_bits
                storeBlockSwitch(&self.block_split_code_, block_len, block_type, false, storage_ix, storage)
        }

        self.block_len_--
        {
                var histo_ix uint = uint(context_map[self.entropy_ix_+context])
                var ix uint = histo_ix*self.histogram_length_ + symbol
                writeBits(uint(self.depths_[ix]), uint64(self.bits_[ix]), storage_ix, storage)
        }
}

func buildAndStoreEntropyCodesLiteral(self *blockEncoder, histograms []histogramLiteral, histograms_size uint, alphabet_size uint, tree []huffmanTree, storage_ix *uint, storage []byte) {
        var table_size uint = histograms_size * self.histogram_length_
        if cap(self.depths_) < int(table_size) {
                self.depths_ = make([]byte, table_size)
        } else {
                self.depths_ = self.depths_[:table_size]
        }
        if cap(self.bits_) < int(table_size) {
                self.bits_ = make([]uint16, table_size)
        } else {
                self.bits_ = self.bits_[:table_size]
        }
        {
                var i uint
                for i = 0; i < histograms_size; i++ {
                        var ix uint = i * self.histogram_length_
                        buildAndStoreHuffmanTree(histograms[i].data_[0:], self.histogram_length_, alphabet_size, tree, self.depths_[ix:], self.bits_[ix:], storage_ix, storage)
                }
        }
}

func buildAndStoreEntropyCodesCommand(self *blockEncoder, histograms []histogramCommand, histograms_size uint, alphabet_size uint, tree []huffmanTree, storage_ix *uint, storage []byte) {
        var table_size uint = histograms_size * self.histogram_length_
        if cap(self.depths_) < int(table_size) {
                self.depths_ = make([]byte, table_size)
        } else {
                self.depths_ = self.depths_[:table_size]
        }
        if cap(self.bits_) < int(table_size) {
                self.bits_ = make([]uint16, table_size)
        } else {
                self.bits_ = self.bits_[:table_size]
        }
        {
                var i uint
                for i = 0; i < histograms_size; i++ {
                        var ix uint = i * self.histogram_length_
                        buildAndStoreHuffmanTree(histograms[i].data_[0:], self.histogram_length_, alphabet_size, tree, self.depths_[ix:], self.bits_[ix:], storage_ix, storage)
                }
        }
}

func buildAndStoreEntropyCodesDistance(self *blockEncoder, histograms []histogramDistance, histograms_size uint, alphabet_size uint, tree []huffmanTree, storage_ix *uint, storage []byte) {
        var table_size uint = histograms_size * self.histogram_length_
        if cap(self.depths_) < int(table_size) {
                self.depths_ = make([]byte, table_size)
        } else {
                self.depths_ = self.depths_[:table_size]
        }
        if cap(self.bits_) < int(table_size) {
                self.bits_ = make([]uint16, table_size)
        } else {
                self.bits_ = self.bits_[:table_size]
        }
        {
                var i uint
                for i = 0; i < histograms_size; i++ {
                        var ix uint = i * self.histogram_length_
                        buildAndStoreHuffmanTree(histograms[i].data_[0:], self.histogram_length_, alphabet_size, tree, self.depths_[ix:], self.bits_[ix:], storage_ix, storage)
                }
        }
}

func jumpToByteBoundary(storage_ix *uint, storage []byte) {
        *storage_ix = (*storage_ix + 7) &^ 7
        storage[*storage_ix>>3] = 0
}

func storeMetaBlock(input []byte, start_pos uint, length uint, mask uint, prev_byte byte, prev_byte2 byte, is_last bool, params *encoderParams, literal_context_mode int, commands []command, mb *metaBlockSplit, storage_ix *uint, storage []byte) {
        var pos uint = start_pos
        var i uint
        var num_distance_symbols uint32 = params.dist.alphabet_size
        var num_effective_distance_symbols uint32 = num_distance_symbols
        var tree []huffmanTree
        var literal_context_lut contextLUT = getContextLUT(literal_context_mode)
        var dist *distanceParams = &params.dist
        if params.large_window && num_effective_distance_symbols > numHistogramDistanceSymbols {
                num_effective_distance_symbols = numHistogramDistanceSymbols
        }

        storeCompressedMetaBlockHeader(is_last, length, storage_ix, storage)

        tree = make([]huffmanTree, maxHuffmanTreeSize)
        literal_enc := getBlockEncoder(numLiteralSymbols, mb.literal_split.num_types, mb.literal_split.types, mb.literal_split.lengths, mb.literal_split.num_blocks)
        command_enc := getBlockEncoder(numCommandSymbols, mb.command_split.num_types, mb.command_split.types, mb.command_split.lengths, mb.command_split.num_blocks)
        distance_enc := getBlockEncoder(uint(num_effective_distance_symbols), mb.distance_split.num_types, mb.distance_split.types, mb.distance_split.lengths, mb.distance_split.num_blocks)

        buildAndStoreBlockSwitchEntropyCodes(literal_enc, tree, storage_ix, storage)
        buildAndStoreBlockSwitchEntropyCodes(command_enc, tree, storage_ix, storage)
        buildAndStoreBlockSwitchEntropyCodes(distance_enc, tree, storage_ix, storage)

        writeBits(2, uint64(dist.distance_postfix_bits), storage_ix, storage)
        writeBits(4, uint64(dist.num_direct_distance_codes)>>dist.distance_postfix_bits, storage_ix, storage)
        for i = 0; i < mb.literal_split.num_types; i++ {
                writeBits(2, uint64(literal_context_mode), storage_ix, storage)
        }

        if mb.literal_context_map_size == 0 {
                storeTrivialContextMap(mb.literal_histograms_size, literalContextBits, tree, storage_ix, storage)
        } else {
                encodeContextMap(mb.literal_context_map, mb.literal_context_map_size, mb.literal_histograms_size, tree, storage_ix, storage)
        }

        if mb.distance_context_map_size == 0 {
                storeTrivialContextMap(mb.distance_histograms_size, distanceContextBits, tree, storage_ix, storage)
        } else {
                encodeContextMap(mb.distance_context_map, mb.distance_context_map_size, mb.distance_histograms_size, tree, storage_ix, storage)
        }

        buildAndStoreEntropyCodesLiteral(literal_enc, mb.literal_histograms, mb.literal_histograms_size, numLiteralSymbols, tree, storage_ix, storage)
        buildAndStoreEntropyCodesCommand(command_enc, mb.command_histograms, mb.command_histograms_size, numCommandSymbols, tree, storage_ix, storage)
        buildAndStoreEntropyCodesDistance(distance_enc, mb.distance_histograms, mb.distance_histograms_size, uint(num_distance_symbols), tree, storage_ix, storage)
        tree = nil

        for _, cmd := range commands {
                var cmd_code uint = uint(cmd.cmd_prefix_)
                storeSymbol(command_enc, cmd_code, storage_ix, storage)
                storeCommandExtra(&cmd, storage_ix, storage)
                if mb.literal_context_map_size == 0 {
                        var j uint
                        for j = uint(cmd.insert_len_); j != 0; j-- {
                                storeSymbol(literal_enc, uint(input[pos&mask]), storage_ix, storage)
                                pos++
                        }
                } else {
                        var j uint
                        for j = uint(cmd.insert_len_); j != 0; j-- {
                                var context uint = uint(getContext(prev_byte, prev_byte2, literal_context_lut))
                                var literal byte = input[pos&mask]
                                storeSymbolWithContext(literal_enc, uint(literal), context, mb.literal_context_map, storage_ix, storage, literalContextBits)
                                prev_byte2 = prev_byte
                                prev_byte = literal
                                pos++
                        }
                }

                pos += uint(commandCopyLen(&cmd))
                if commandCopyLen(&cmd) != 0 {
                        prev_byte2 = input[(pos-2)&mask]
                        prev_byte = input[(pos-1)&mask]
                        if cmd.cmd_prefix_ >= 128 {
                                var dist_code uint = uint(cmd.dist_prefix_) & 0x3FF
                                var distnumextra uint32 = uint32(cmd.dist_prefix_) >> 10
                                var distextra uint64 = uint64(cmd.dist_extra_)
                                if mb.distance_context_map_size == 0 {
                                        storeSymbol(distance_enc, dist_code, storage_ix, storage)
                                } else {
                                        var context uint = uint(commandDistanceContext(&cmd))
                                        storeSymbolWithContext(distance_enc, dist_code, context, mb.distance_context_map, storage_ix, storage, distanceContextBits)
                                }

                                writeBits(uint(distnumextra), distextra, storage_ix, storage)
                        }
                }
        }

        cleanupBlockEncoder(distance_enc)
        cleanupBlockEncoder(command_enc)
        cleanupBlockEncoder(literal_enc)
        if is_last {
                jumpToByteBoundary(storage_ix, storage)
        }
}

func buildHistograms(input []byte, start_pos uint, mask uint, commands []command, lit_histo *histogramLiteral, cmd_histo *histogramCommand, dist_histo *histogramDistance) {
        var pos uint = start_pos
        for _, cmd := range commands {
                var j uint
                histogramAddCommand(cmd_histo, uint(cmd.cmd_prefix_))
                for j = uint(cmd.insert_len_); j != 0; j-- {
                        histogramAddLiteral(lit_histo, uint(input[pos&mask]))
                        pos++
                }

                pos += uint(commandCopyLen(&cmd))
                if commandCopyLen(&cmd) != 0 && cmd.cmd_prefix_ >= 128 {
                        histogramAddDistance(dist_histo, uint(cmd.dist_prefix_)&0x3FF)
                }
        }
}

func storeDataWithHuffmanCodes(input []byte, start_pos uint, mask uint, commands []command, lit_depth []byte, lit_bits []uint16, cmd_depth []byte, cmd_bits []uint16, dist_depth []byte, dist_bits []uint16, storage_ix *uint, storage []byte) {
        var pos uint = start_pos
        for _, cmd := range commands {
                var cmd_code uint = uint(cmd.cmd_prefix_)
                var j uint
                writeBits(uint(cmd_depth[cmd_code]), uint64(cmd_bits[cmd_code]), storage_ix, storage)
                storeCommandExtra(&cmd, storage_ix, storage)
                for j = uint(cmd.insert_len_); j != 0; j-- {
                        var literal byte = input[pos&mask]
                        writeBits(uint(lit_depth[literal]), uint64(lit_bits[literal]), storage_ix, storage)
                        pos++
                }

                pos += uint(commandCopyLen(&cmd))
                if commandCopyLen(&cmd) != 0 && cmd.cmd_prefix_ >= 128 {
                        var dist_code uint = uint(cmd.dist_prefix_) & 0x3FF
                        var distnumextra uint32 = uint32(cmd.dist_prefix_) >> 10
                        var distextra uint32 = cmd.dist_extra_
                        writeBits(uint(dist_depth[dist_code]), uint64(dist_bits[dist_code]), storage_ix, storage)
                        writeBits(uint(distnumextra), uint64(distextra), storage_ix, storage)
                }
        }
}

func storeMetaBlockTrivial(input []byte, start_pos uint, length uint, mask uint, is_last bool, params *encoderParams, commands []command, storage_ix *uint, storage []byte) {
        var lit_histo histogramLiteral
        var cmd_histo histogramCommand
        var dist_histo histogramDistance
        var lit_depth [numLiteralSymbols]byte
        var lit_bits [numLiteralSymbols]uint16
        var cmd_depth [numCommandSymbols]byte
        var cmd_bits [numCommandSymbols]uint16
        var dist_depth [maxSimpleDistanceAlphabetSize]byte
        var dist_bits [maxSimpleDistanceAlphabetSize]uint16
        var tree []huffmanTree
        var num_distance_symbols uint32 = params.dist.alphabet_size

        storeCompressedMetaBlockHeader(is_last, length, storage_ix, storage)

        histogramClearLiteral(&lit_histo)
        histogramClearCommand(&cmd_histo)
        histogramClearDistance(&dist_histo)

        buildHistograms(input, start_pos, mask, commands, &lit_histo, &cmd_histo, &dist_histo)

        writeBits(13, 0, storage_ix, storage)

        tree = make([]huffmanTree, maxHuffmanTreeSize)
        buildAndStoreHuffmanTree(lit_histo.data_[:], numLiteralSymbols, numLiteralSymbols, tree, lit_depth[:], lit_bits[:], storage_ix, storage)
        buildAndStoreHuffmanTree(cmd_histo.data_[:], numCommandSymbols, numCommandSymbols, tree, cmd_depth[:], cmd_bits[:], storage_ix, storage)
        buildAndStoreHuffmanTree(dist_histo.data_[:], maxSimpleDistanceAlphabetSize, uint(num_distance_symbols), tree, dist_depth[:], dist_bits[:], storage_ix, storage)
        tree = nil
        storeDataWithHuffmanCodes(input, start_pos, mask, commands, lit_depth[:], lit_bits[:], cmd_depth[:], cmd_bits[:], dist_depth[:], dist_bits[:], storage_ix, storage)
        if is_last {
                jumpToByteBoundary(storage_ix, storage)
        }
}

func storeMetaBlockFast(input []byte, start_pos uint, length uint, mask uint, is_last bool, params *encoderParams, commands []command, storage_ix *uint, storage []byte) {
        var num_distance_symbols uint32 = params.dist.alphabet_size
        var distance_alphabet_bits uint32 = log2FloorNonZero(uint(num_distance_symbols-1)) + 1

        storeCompressedMetaBlockHeader(is_last, length, storage_ix, storage)

        writeBits(13, 0, storage_ix, storage)

        if len(commands) <= 128 {
                var histogram = [numLiteralSymbols]uint32{0}
                var pos uint = start_pos
                var num_literals uint = 0
                var lit_depth [numLiteralSymbols]byte
                var lit_bits [numLiteralSymbols]uint16
                for _, cmd := range commands {
                        var j uint
                        for j = uint(cmd.insert_len_); j != 0; j-- {
                                histogram[input[pos&mask]]++
                                pos++
                        }

                        num_literals += uint(cmd.insert_len_)
                        pos += uint(commandCopyLen(&cmd))
                }

                buildAndStoreHuffmanTreeFast(histogram[:], num_literals, /* max_bits = */
                        8, lit_depth[:], lit_bits[:], storage_ix, storage)

                storeStaticCommandHuffmanTree(storage_ix, storage)
                storeStaticDistanceHuffmanTree(storage_ix, storage)
                storeDataWithHuffmanCodes(input, start_pos, mask, commands, lit_depth[:], lit_bits[:], kStaticCommandCodeDepth[:], kStaticCommandCodeBits[:], kStaticDistanceCodeDepth[:], kStaticDistanceCodeBits[:], storage_ix, storage)
        } else {
                var lit_histo histogramLiteral
                var cmd_histo histogramCommand
                var dist_histo histogramDistance
                var lit_depth [numLiteralSymbols]byte
                var lit_bits [numLiteralSymbols]uint16
                var cmd_depth [numCommandSymbols]byte
                var cmd_bits [numCommandSymbols]uint16
                var dist_depth [maxSimpleDistanceAlphabetSize]byte
                var dist_bits [maxSimpleDistanceAlphabetSize]uint16
                histogramClearLiteral(&lit_histo)
                histogramClearCommand(&cmd_histo)
                histogramClearDistance(&dist_histo)
                buildHistograms(input, start_pos, mask, commands, &lit_histo, &cmd_histo, &dist_histo)
                buildAndStoreHuffmanTreeFast(lit_histo.data_[:], lit_histo.total_count_, /* max_bits = */
                        8, lit_depth[:], lit_bits[:], storage_ix, storage)

                buildAndStoreHuffmanTreeFast(cmd_histo.data_[:], cmd_histo.total_count_, /* max_bits = */
                        10, cmd_depth[:], cmd_bits[:], storage_ix, storage)

                buildAndStoreHuffmanTreeFast(dist_histo.data_[:], dist_histo.total_count_, /* max_bits = */
                        uint(distance_alphabet_bits), dist_depth[:], dist_bits[:], storage_ix, storage)

                storeDataWithHuffmanCodes(input, start_pos, mask, commands, lit_depth[:], lit_bits[:], cmd_depth[:], cmd_bits[:], dist_depth[:], dist_bits[:], storage_ix, storage)
        }

        if is_last {
                jumpToByteBoundary(storage_ix, storage)
        }
}

/* This is for storing uncompressed blocks (simple raw storage of
   bytes-as-bytes). */
func storeUncompressedMetaBlock(is_final_block bool, input []byte, position uint, mask uint, len uint, storage_ix *uint, storage []byte) {
        var masked_pos uint = position & mask
        storeUncompressedMetaBlockHeader(uint(len), storage_ix, storage)
        jumpToByteBoundary(storage_ix, storage)

        if masked_pos+len > mask+1 {
                var len1 uint = mask + 1 - masked_pos
                copy(storage[*storage_ix>>3:], input[masked_pos:][:len1])
                *storage_ix += len1 << 3
                len -= len1
                masked_pos = 0
        }

        copy(storage[*storage_ix>>3:], input[masked_pos:][:len])
        *storage_ix += uint(len << 3)

        /* We need to clear the next 4 bytes to continue to be
           compatible with BrotliWriteBits. */
        writeBitsPrepareStorage(*storage_ix, storage)

        /* Since the uncompressed block itself may not be the final block, add an
           empty one after this. */
        if is_final_block {
                writeBits(1, 1, storage_ix, storage) /* islast */
                writeBits(1, 1, storage_ix, storage) /* isempty */
                jumpToByteBoundary(storage_ix, storage)
        }
}