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gitea/vendor/github.com/andybalholm/brotli/write_bits.go

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package brotli
/* 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. */
type bitWriter struct {
dst []byte
// Data waiting to be written is the low nbits of bits.
bits uint64
nbits uint
}
func (w *bitWriter) writeBits(nb uint, b uint64) {
w.bits |= b << w.nbits
w.nbits += nb
if w.nbits >= 32 {
bits := w.bits
w.bits >>= 32
w.nbits -= 32
w.dst = append(w.dst,
byte(bits),
byte(bits>>8),
byte(bits>>16),
byte(bits>>24),
)
}
}
func (w *bitWriter) writeSingleBit(bit bool) {
if bit {
w.writeBits(1, 1)
} else {
w.writeBits(1, 0)
}
}
func (w *bitWriter) jumpToByteBoundary() {
dst := w.dst
for w.nbits != 0 {
dst = append(dst, byte(w.bits))
w.bits >>= 8
if w.nbits > 8 { // Avoid underflow
w.nbits -= 8
} else {
w.nbits = 0
}
}
w.bits = 0
w.dst = dst
}
func (w *bitWriter) writeBytes(b []byte) {
if w.nbits&7 != 0 {
panic("writeBytes with unfinished bits")
}
for w.nbits != 0 {
w.dst = append(w.dst, byte(w.bits))
w.bits >>= 8
w.nbits -= 8
}
w.dst = append(w.dst, b...)
}
func (w *bitWriter) getPos() uint {
return uint(len(w.dst)<<3) + w.nbits
}
func (w *bitWriter) rewind(p uint) {
w.bits = uint64(w.dst[p>>3] & byte((1<<(p&7))-1))
w.nbits = p & 7
w.dst = w.dst[:p>>3]
}
func (w *bitWriter) updateBits(n_bits uint, bits uint32, pos uint) {
for n_bits > 0 {
var byte_pos uint = pos >> 3
var n_unchanged_bits uint = pos & 7
var n_changed_bits uint = brotli_min_size_t(n_bits, 8-n_unchanged_bits)
var total_bits uint = n_unchanged_bits + n_changed_bits
var mask uint32 = (^((1 << total_bits) - 1)) | ((1 << n_unchanged_bits) - 1)
var unchanged_bits uint32 = uint32(w.dst[byte_pos]) & mask
var changed_bits uint32 = bits & ((1 << n_changed_bits) - 1)
w.dst[byte_pos] = byte(changed_bits<<n_unchanged_bits | unchanged_bits)
n_bits -= n_changed_bits
bits >>= n_changed_bits
pos += n_changed_bits
}
}