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https://codeberg.org/forgejo/forgejo.git
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253 lines
5.3 KiB
Go
253 lines
5.3 KiB
Go
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package brotli
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var kInsBase = []uint32{
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0,
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1,
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2,
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3,
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18,
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26,
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34,
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50,
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66,
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98,
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130,
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194,
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322,
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578,
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1090,
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2114,
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6210,
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22594,
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}
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var kInsExtra = []uint32{
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0,
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0,
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0,
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0,
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0,
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0,
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1,
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1,
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12,
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14,
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24,
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}
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var kCopyBase = []uint32{
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2,
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3,
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10,
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12,
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14,
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18,
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22,
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30,
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38,
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54,
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70,
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102,
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134,
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198,
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326,
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582,
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1094,
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2118,
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}
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var kCopyExtra = []uint32{
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0,
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0,
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0,
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0,
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0,
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0,
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0,
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0,
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1,
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1,
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2,
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2,
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3,
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3,
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10,
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24,
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}
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func getInsertLengthCode(insertlen uint) uint16 {
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if insertlen < 6 {
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return uint16(insertlen)
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} else if insertlen < 130 {
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var nbits uint32 = log2FloorNonZero(insertlen-2) - 1
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return uint16((nbits << 1) + uint32((insertlen-2)>>nbits) + 2)
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} else if insertlen < 2114 {
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return uint16(log2FloorNonZero(insertlen-66) + 10)
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} else if insertlen < 6210 {
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return 21
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} else if insertlen < 22594 {
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return 22
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} else {
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return 23
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}
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}
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func getCopyLengthCode(copylen uint) uint16 {
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if copylen < 10 {
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return uint16(copylen - 2)
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} else if copylen < 134 {
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var nbits uint32 = log2FloorNonZero(copylen-6) - 1
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return uint16((nbits << 1) + uint32((copylen-6)>>nbits) + 4)
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} else if copylen < 2118 {
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return uint16(log2FloorNonZero(copylen-70) + 12)
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} else {
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return 23
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}
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}
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func combineLengthCodes(inscode uint16, copycode uint16, use_last_distance bool) uint16 {
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var bits64 uint16 = uint16(copycode&0x7 | (inscode&0x7)<<3)
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if use_last_distance && inscode < 8 && copycode < 16 {
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if copycode < 8 {
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return bits64
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} else {
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return bits64 | 64
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}
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} else {
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/* Specification: 5 Encoding of ... (last table) */
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/* offset = 2 * index, where index is in range [0..8] */
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var offset uint32 = 2 * ((uint32(copycode) >> 3) + 3*(uint32(inscode)>>3))
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/* All values in specification are K * 64,
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where K = [2, 3, 6, 4, 5, 8, 7, 9, 10],
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i + 1 = [1, 2, 3, 4, 5, 6, 7, 8, 9],
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K - i - 1 = [1, 1, 3, 0, 0, 2, 0, 1, 2] = D.
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All values in D require only 2 bits to encode.
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Magic constant is shifted 6 bits left, to avoid final multiplication. */
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offset = (offset << 5) + 0x40 + ((0x520D40 >> offset) & 0xC0)
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return uint16(offset | uint32(bits64))
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}
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}
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func getLengthCode(insertlen uint, copylen uint, use_last_distance bool, code *uint16) {
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var inscode uint16 = getInsertLengthCode(insertlen)
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var copycode uint16 = getCopyLengthCode(copylen)
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*code = combineLengthCodes(inscode, copycode, use_last_distance)
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}
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func getInsertBase(inscode uint16) uint32 {
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return kInsBase[inscode]
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}
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func getInsertExtra(inscode uint16) uint32 {
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return kInsExtra[inscode]
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}
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func getCopyBase(copycode uint16) uint32 {
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return kCopyBase[copycode]
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}
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func getCopyExtra(copycode uint16) uint32 {
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return kCopyExtra[copycode]
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}
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type command struct {
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insert_len_ uint32
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copy_len_ uint32
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dist_extra_ uint32
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cmd_prefix_ uint16
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dist_prefix_ uint16
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}
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/* distance_code is e.g. 0 for same-as-last short code, or 16 for offset 1. */
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func initCommand(self *command, dist *distanceParams, insertlen uint, copylen uint, copylen_code_delta int, distance_code uint) {
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/* Don't rely on signed int representation, use honest casts. */
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var delta uint32 = uint32(byte(int8(copylen_code_delta)))
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self.insert_len_ = uint32(insertlen)
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self.copy_len_ = uint32(uint32(copylen) | delta<<25)
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/* The distance prefix and extra bits are stored in this Command as if
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npostfix and ndirect were 0, they are only recomputed later after the
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clustering if needed. */
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prefixEncodeCopyDistance(distance_code, uint(dist.num_direct_distance_codes), uint(dist.distance_postfix_bits), &self.dist_prefix_, &self.dist_extra_)
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getLengthCode(insertlen, uint(int(copylen)+copylen_code_delta), (self.dist_prefix_&0x3FF == 0), &self.cmd_prefix_)
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}
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func initInsertCommand(self *command, insertlen uint) {
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self.insert_len_ = uint32(insertlen)
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self.copy_len_ = 4 << 25
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self.dist_extra_ = 0
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self.dist_prefix_ = numDistanceShortCodes
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getLengthCode(insertlen, 4, false, &self.cmd_prefix_)
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}
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func commandRestoreDistanceCode(self *command, dist *distanceParams) uint32 {
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if uint32(self.dist_prefix_&0x3FF) < numDistanceShortCodes+dist.num_direct_distance_codes {
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return uint32(self.dist_prefix_) & 0x3FF
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} else {
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var dcode uint32 = uint32(self.dist_prefix_) & 0x3FF
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var nbits uint32 = uint32(self.dist_prefix_) >> 10
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var extra uint32 = self.dist_extra_
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var postfix_mask uint32 = (1 << dist.distance_postfix_bits) - 1
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var hcode uint32 = (dcode - dist.num_direct_distance_codes - numDistanceShortCodes) >> dist.distance_postfix_bits
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var lcode uint32 = (dcode - dist.num_direct_distance_codes - numDistanceShortCodes) & postfix_mask
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var offset uint32 = ((2 + (hcode & 1)) << nbits) - 4
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return ((offset + extra) << dist.distance_postfix_bits) + lcode + dist.num_direct_distance_codes + numDistanceShortCodes
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}
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}
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func commandDistanceContext(self *command) uint32 {
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var r uint32 = uint32(self.cmd_prefix_) >> 6
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var c uint32 = uint32(self.cmd_prefix_) & 7
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if (r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2) {
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return c
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}
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return 3
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}
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func commandCopyLen(self *command) uint32 {
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return self.copy_len_ & 0x1FFFFFF
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}
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func commandCopyLenCode(self *command) uint32 {
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var modifier uint32 = self.copy_len_ >> 25
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var delta int32 = int32(int8(byte(modifier | (modifier&0x40)<<1)))
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return uint32(int32(self.copy_len_&0x1FFFFFF) + delta)
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}
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