109 lines
1.8 KiB
C++
109 lines
1.8 KiB
C++
#include "BitReader.h"
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static uint32_t mask[8]=
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{
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0x1,
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0x3,
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0x7,
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0xF,
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0x1F,
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0x3F,
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0x7F,
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0xFF
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};
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static uint32_t msk[33] =
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{
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0x00000000,0x00000001,0x00000003,0x00000007,
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0x0000000f,0x0000001f,0x0000003f,0x0000007f,
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0x000000ff,0x000001ff,0x000003ff,0x000007ff,
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0x00000fff,0x00001fff,0x00003fff,0x00007fff,
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0x0000ffff,0x0001ffff,0x0003ffff,0x0007ffff,
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0x000fffff,0x001fffff,0x003fffff,0x007fffff,
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0x00ffffff,0x01ffffff,0x03ffffff,0x07ffffff,
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0x0fffffff,0x1fffffff,0x3fffffff,0x7fffffff,
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0xffffffff
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};
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void BitReader::alignbyte()
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{
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flushbits(numBits&7);
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}
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void BitReader::getbytes(void *data, uint32_t n)
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{
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memcpy(data, this->data, n);
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flushbits(n*8);
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}
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uint8_t BitReader::getbits1()
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{
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uint8_t byte = data[0];
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uint32_t count = (numBits-1) & 7;
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byte &= mask[count];
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byte >>= count;
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numBits--;
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if ((numBits % 8) == 0)
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data++;
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return byte;
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}
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uint32_t BitReader::getbits(uint32_t n)
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{
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uint32_t val = showbits(n);
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flushbits(n);
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return val;
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}
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uint8_t BitReader::showbits1() const
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{
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uint8_t byte = data[0];
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uint32_t count = (numBits-1) & 7;
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byte &= mask[count];
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byte >>= count;
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return byte;
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}
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uint32_t BitReader::showbits(uint32_t n) const
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{
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uint32_t val;
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switch((numBits+7) >> 3)
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{
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case 0:
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return 0;
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case 1:
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val=(data[0]<<24);
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break;
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case 2:
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val=(data[0]<<24) | (data[1]<<16);
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break;
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case 3:
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val=(data[0]<<24) | (data[1]<<16) | (data[2]<<8);
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break;
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default:
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val=(data[0]<<24) | (data[1]<<16) | (data[2]<<8) | data[3];
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break;
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}
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uint32_t c = ((numBits-1) & 7) + 25;
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return (val>>(c-n)) & msk[n];
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}
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void BitReader::flushbits(uint32_t n)
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{
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uint32_t oldpos = (numBits+7)>>3;
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numBits-=n;
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uint32_t newpos = (numBits+7)>>3;
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data += (oldpos - newpos);
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}
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bool BitReader::empty()
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{
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return numBits==0;
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}
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uint32_t BitReader::size() const
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{
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return numBits;
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}
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