Платформа ЦРНП "Мирокод" для разработки проектов
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94 lines
2.0 KiB
94 lines
2.0 KiB
package brotli |
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/* Copyright 2010 Google Inc. All Rights Reserved. |
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Distributed under MIT license. |
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
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*/ |
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/* Write bits into a byte array. */ |
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type bitWriter struct { |
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dst []byte |
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// Data waiting to be written is the low nbits of bits. |
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bits uint64 |
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nbits uint |
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} |
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func (w *bitWriter) writeBits(nb uint, b uint64) { |
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w.bits |= b << w.nbits |
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w.nbits += nb |
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if w.nbits >= 32 { |
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bits := w.bits |
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w.bits >>= 32 |
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w.nbits -= 32 |
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w.dst = append(w.dst, |
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byte(bits), |
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byte(bits>>8), |
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byte(bits>>16), |
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byte(bits>>24), |
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) |
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} |
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} |
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func (w *bitWriter) writeSingleBit(bit bool) { |
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if bit { |
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w.writeBits(1, 1) |
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} else { |
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w.writeBits(1, 0) |
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} |
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} |
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func (w *bitWriter) jumpToByteBoundary() { |
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dst := w.dst |
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for w.nbits != 0 { |
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dst = append(dst, byte(w.bits)) |
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w.bits >>= 8 |
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if w.nbits > 8 { // Avoid underflow |
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w.nbits -= 8 |
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} else { |
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w.nbits = 0 |
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} |
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} |
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w.bits = 0 |
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w.dst = dst |
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} |
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func (w *bitWriter) writeBytes(b []byte) { |
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if w.nbits&7 != 0 { |
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panic("writeBytes with unfinished bits") |
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} |
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for w.nbits != 0 { |
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w.dst = append(w.dst, byte(w.bits)) |
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w.bits >>= 8 |
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w.nbits -= 8 |
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} |
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w.dst = append(w.dst, b...) |
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} |
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func (w *bitWriter) getPos() uint { |
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return uint(len(w.dst)<<3) + w.nbits |
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} |
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func (w *bitWriter) rewind(p uint) { |
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w.bits = uint64(w.dst[p>>3] & byte((1<<(p&7))-1)) |
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w.nbits = p & 7 |
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w.dst = w.dst[:p>>3] |
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} |
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func (w *bitWriter) updateBits(n_bits uint, bits uint32, pos uint) { |
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for n_bits > 0 { |
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var byte_pos uint = pos >> 3 |
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var n_unchanged_bits uint = pos & 7 |
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var n_changed_bits uint = brotli_min_size_t(n_bits, 8-n_unchanged_bits) |
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var total_bits uint = n_unchanged_bits + n_changed_bits |
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var mask uint32 = (^((1 << total_bits) - 1)) | ((1 << n_unchanged_bits) - 1) |
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var unchanged_bits uint32 = uint32(w.dst[byte_pos]) & mask |
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var changed_bits uint32 = bits & ((1 << n_changed_bits) - 1) |
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w.dst[byte_pos] = byte(changed_bits<<n_unchanged_bits | unchanged_bits) |
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n_bits -= n_changed_bits |
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bits >>= n_changed_bits |
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pos += n_changed_bits |
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} |
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}
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