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bitstream.hh
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bitstream.hh
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/*
Bitwise stream container
Copyright 2018 Ahmet Inan <[email protected]>
*/
#pragma once
namespace CODE {
template <int SIZE>
class Bitstream
{
public:
static const int BITS = SIZE;
static const int BYTES = (SIZE + 7) / 8;
private:
uint8_t buf_[BYTES];
int pos_ = 0;
public:
void seek(int pos)
{
pos_ = pos;
}
int tell()
{
return pos_;
}
uint8_t *data()
{
return buf_;
}
void reset()
{
pos_ = 0;
for (int i = 0; i < BYTES; ++i)
buf_[i] = 0;
}
void putbit(bool b)
{
int bit = pos_ % 8;
int byte = pos_ / 8;
++pos_;
uint8_t mask = 1 << bit;
uint8_t tmp = ~mask & buf_[byte];
buf_[byte] = tmp | b << bit;
}
bool getbit()
{
int bit = pos_ % 8;
int byte = pos_ / 8;
++pos_;
return (buf_[byte] >> bit) & 1;
}
void putbyte(const uint8_t b)
{
int bit = pos_ % 8;
int byte = pos_ / 8;
pos_ += 8;
if (bit) {
uint8_t mask = (1 << bit) - 1;
uint8_t lsb = mask & buf_[byte];
buf_[byte++] = lsb | b << bit;
uint8_t msb = ~mask & buf_[byte];
buf_[byte] = msb | b >> (8 - bit);
} else {
buf_[byte] = b;
}
}
uint8_t getbyte()
{
int bit = pos_ % 8;
int byte = pos_ / 8;
pos_ += 8;
if (bit) {
uint8_t lsb = buf_[byte++] >> bit;
uint8_t msb = buf_[byte] << (8 - bit);
return msb | lsb;
}
return buf_[byte];
}
void writebytes(const uint8_t *buf, int len)
{
int bit = pos_ % 8;
int byte = pos_ / 8;
pos_ += 8 * len;
if (bit) {
uint8_t mask = (1 << bit) - 1;
for (int i = 0; i < len; ++i) {
uint8_t lsb = mask & buf_[byte];
buf_[byte++] = lsb | buf[i] << bit;
uint8_t msb = ~mask & buf_[byte];
buf_[byte] = msb | buf[i] >> (8 - bit);
}
} else {
for (int i = 0; i < len; ++i)
buf_[byte++] = buf[i];
}
}
void readbytes(uint8_t *buf, int len)
{
int bit = pos_ % 8;
int byte = pos_ / 8;
pos_ += 8 * len;
if (bit) {
for (int i = 0; i < len; ++i) {
uint8_t lsb = buf_[byte++] >> bit;
uint8_t msb = buf_[byte] << (8 - bit);
buf[i] = msb | lsb;
}
} else {
for (int i = 0; i < len; ++i)
buf[i] = buf_[byte++];
}
}
template <typename TYPE>
void writebits(TYPE b, int num)
{
for (int sum = 0; num;) {
int bit = pos_ % 8;
int byte = pos_ / 8;
int copy = std::min(8 - bit, num);
uint8_t mask = (1 << copy) - 1;
uint8_t src = (mask & (b >> sum)) << bit;
uint8_t dst = ~(mask << bit) & buf_[byte];
buf_[byte++] = dst | src;
pos_ += copy;
num -= copy;
sum += copy;
}
}
template <typename TYPE>
void readbits(TYPE *b, int num)
{
TYPE a = 0;
for (int sum = 0; num;) {
int bit = pos_ % 8;
int byte = pos_ / 8;
int copy = std::min(8 - bit, num);
uint8_t mask = (1 << copy) - 1;
TYPE tmp = mask & (buf_[byte++] >> bit);
a |= tmp << sum;
pos_ += copy;
num -= copy;
sum += copy;
}
*b = a;
}
};
}