diff options
Diffstat (limited to 'vendor/github.com/andybalholm/brotli/command.go')
| -rw-r--r-- | vendor/github.com/andybalholm/brotli/command.go | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/vendor/github.com/andybalholm/brotli/command.go b/vendor/github.com/andybalholm/brotli/command.go new file mode 100644 index 0000000000..e93ccdfa1e --- /dev/null +++ b/vendor/github.com/andybalholm/brotli/command.go @@ -0,0 +1,252 @@ +package brotli + +var kInsBase = []uint32{ + 0, + 1, + 2, + 3, + 4, + 5, + 6, + 8, + 10, + 14, + 18, + 26, + 34, + 50, + 66, + 98, + 130, + 194, + 322, + 578, + 1090, + 2114, + 6210, + 22594, +} + +var kInsExtra = []uint32{ + 0, + 0, + 0, + 0, + 0, + 0, + 1, + 1, + 2, + 2, + 3, + 3, + 4, + 4, + 5, + 5, + 6, + 7, + 8, + 9, + 10, + 12, + 14, + 24, +} + +var kCopyBase = []uint32{ + 2, + 3, + 4, + 5, + 6, + 7, + 8, + 9, + 10, + 12, + 14, + 18, + 22, + 30, + 38, + 54, + 70, + 102, + 134, + 198, + 326, + 582, + 1094, + 2118, +} + +var kCopyExtra = []uint32{ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 1, + 1, + 2, + 2, + 3, + 3, + 4, + 4, + 5, + 5, + 6, + 7, + 8, + 9, + 10, + 24, +} + +func getInsertLengthCode(insertlen uint) uint16 { + if insertlen < 6 { + return uint16(insertlen) + } else if insertlen < 130 { + var nbits uint32 = log2FloorNonZero(insertlen-2) - 1 + return uint16((nbits << 1) + uint32((insertlen-2)>>nbits) + 2) + } else if insertlen < 2114 { + return uint16(log2FloorNonZero(insertlen-66) + 10) + } else if insertlen < 6210 { + return 21 + } else if insertlen < 22594 { + return 22 + } else { + return 23 + } +} + +func getCopyLengthCode(copylen uint) uint16 { + if copylen < 10 { + return uint16(copylen - 2) + } else if copylen < 134 { + var nbits uint32 = log2FloorNonZero(copylen-6) - 1 + return uint16((nbits << 1) + uint32((copylen-6)>>nbits) + 4) + } else if copylen < 2118 { + return uint16(log2FloorNonZero(copylen-70) + 12) + } else { + return 23 + } +} + +func combineLengthCodes(inscode uint16, copycode uint16, use_last_distance bool) uint16 { + var bits64 uint16 = uint16(copycode&0x7 | (inscode&0x7)<<3) + if use_last_distance && inscode < 8 && copycode < 16 { + if copycode < 8 { + return bits64 + } else { + return bits64 | 64 + } + } else { + /* Specification: 5 Encoding of ... (last table) */ + /* offset = 2 * index, where index is in range [0..8] */ + var offset uint32 = 2 * ((uint32(copycode) >> 3) + 3*(uint32(inscode)>>3)) + + /* All values in specification are K * 64, + where K = [2, 3, 6, 4, 5, 8, 7, 9, 10], + i + 1 = [1, 2, 3, 4, 5, 6, 7, 8, 9], + K - i - 1 = [1, 1, 3, 0, 0, 2, 0, 1, 2] = D. + All values in D require only 2 bits to encode. + Magic constant is shifted 6 bits left, to avoid final multiplication. */ + offset = (offset << 5) + 0x40 + ((0x520D40 >> offset) & 0xC0) + + return uint16(offset | uint32(bits64)) + } +} + +func getLengthCode(insertlen uint, copylen uint, use_last_distance bool, code *uint16) { + var inscode uint16 = getInsertLengthCode(insertlen) + var copycode uint16 = getCopyLengthCode(copylen) + *code = combineLengthCodes(inscode, copycode, use_last_distance) +} + +func getInsertBase(inscode uint16) uint32 { + return kInsBase[inscode] +} + +func getInsertExtra(inscode uint16) uint32 { + return kInsExtra[inscode] +} + +func getCopyBase(copycode uint16) uint32 { + return kCopyBase[copycode] +} + +func getCopyExtra(copycode uint16) uint32 { + return kCopyExtra[copycode] +} + +type command struct { + insert_len_ uint32 + copy_len_ uint32 + dist_extra_ uint32 + cmd_prefix_ uint16 + dist_prefix_ uint16 +} + +/* distance_code is e.g. 0 for same-as-last short code, or 16 for offset 1. */ +func initCommand(self *command, dist *distanceParams, insertlen uint, copylen uint, copylen_code_delta int, distance_code uint) { + /* Don't rely on signed int representation, use honest casts. */ + var delta uint32 = uint32(byte(int8(copylen_code_delta))) + self.insert_len_ = uint32(insertlen) + self.copy_len_ = uint32(uint32(copylen) | delta<<25) + + /* The distance prefix and extra bits are stored in this Command as if + npostfix and ndirect were 0, they are only recomputed later after the + clustering if needed. */ + prefixEncodeCopyDistance(distance_code, uint(dist.num_direct_distance_codes), uint(dist.distance_postfix_bits), &self.dist_prefix_, &self.dist_extra_) + + getLengthCode(insertlen, uint(int(copylen)+copylen_code_delta), (self.dist_prefix_&0x3FF == 0), &self.cmd_prefix_) +} + +func initInsertCommand(self *command, insertlen uint) { + self.insert_len_ = uint32(insertlen) + self.copy_len_ = 4 << 25 + self.dist_extra_ = 0 + self.dist_prefix_ = numDistanceShortCodes + getLengthCode(insertlen, 4, false, &self.cmd_prefix_) +} + +func commandRestoreDistanceCode(self *command, dist *distanceParams) uint32 { + if uint32(self.dist_prefix_&0x3FF) < numDistanceShortCodes+dist.num_direct_distance_codes { + return uint32(self.dist_prefix_) & 0x3FF + } else { + var dcode uint32 = uint32(self.dist_prefix_) & 0x3FF + var nbits uint32 = uint32(self.dist_prefix_) >> 10 + var extra uint32 = self.dist_extra_ + var postfix_mask uint32 = (1 << dist.distance_postfix_bits) - 1 + var hcode uint32 = (dcode - dist.num_direct_distance_codes - numDistanceShortCodes) >> dist.distance_postfix_bits + var lcode uint32 = (dcode - dist.num_direct_distance_codes - numDistanceShortCodes) & postfix_mask + var offset uint32 = ((2 + (hcode & 1)) << nbits) - 4 + return ((offset + extra) << dist.distance_postfix_bits) + lcode + dist.num_direct_distance_codes + numDistanceShortCodes + } +} + +func commandDistanceContext(self *command) uint32 { + var r uint32 = uint32(self.cmd_prefix_) >> 6 + var c uint32 = uint32(self.cmd_prefix_) & 7 + if (r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2) { + return c + } + + return 3 +} + +func commandCopyLen(self *command) uint32 { + return self.copy_len_ & 0x1FFFFFF +} + +func commandCopyLenCode(self *command) uint32 { + var modifier uint32 = self.copy_len_ >> 25 + var delta int32 = int32(int8(byte(modifier | (modifier&0x40)<<1))) + return uint32(int32(self.copy_len_&0x1FFFFFF) + delta) +} |