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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 makeCommand(dist *distanceParams, insertlen uint, copylen uint, copylen_code_delta int, distance_code uint) (cmd command) {
/* Don't rely on signed int representation, use honest casts. */
var delta uint32 = uint32(byte(int8(copylen_code_delta)))
cmd.insert_len_ = uint32(insertlen)
cmd.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), &cmd.dist_prefix_, &cmd.dist_extra_)
getLengthCode(insertlen, uint(int(copylen)+copylen_code_delta), (cmd.dist_prefix_&0x3FF == 0), &cmd.cmd_prefix_)
return cmd
}
func makeInsertCommand(insertlen uint) (cmd command) {
cmd.insert_len_ = uint32(insertlen)
cmd.copy_len_ = 4 << 25
cmd.dist_extra_ = 0
cmd.dist_prefix_ = numDistanceShortCodes
getLengthCode(insertlen, 4, false, &cmd.cmd_prefix_)
return cmd
}
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)
}
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