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package brotli
import "encoding/binary"
/* Copyright 2010 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Write bits into a byte array. */
/* This function writes bits into bytes in increasing addresses, and within
a byte least-significant-bit first.
The function can write up to 56 bits in one go with WriteBits
Example: let's assume that 3 bits (Rs below) have been written already:
BYTE-0 BYTE+1 BYTE+2
0000 0RRR 0000 0000 0000 0000
Now, we could write 5 or less bits in MSB by just sifting by 3
and OR'ing to BYTE-0.
For n bits, we take the last 5 bits, OR that with high bits in BYTE-0,
and locate the rest in BYTE+1, BYTE+2, etc. */
func writeBits(n_bits uint, bits uint64, pos *uint, array []byte) {
/* This branch of the code can write up to 56 bits at a time,
7 bits are lost by being perhaps already in *p and at least
1 bit is needed to initialize the bit-stream ahead (i.e. if 7
bits are in *p and we write 57 bits, then the next write will
access a byte that was never initialized). */
p := array[*pos>>3:]
v := uint64(p[0])
v |= bits << (*pos & 7)
binary.LittleEndian.PutUint64(p, v)
*pos += n_bits
}
func writeSingleBit(bit bool, pos *uint, array []byte) {
if bit {
writeBits(1, 1, pos, array)
} else {
writeBits(1, 0, pos, array)
}
}
func writeBitsPrepareStorage(pos uint, array []byte) {
assert(pos&7 == 0)
array[pos>>3] = 0
}
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