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#include "bitwriter.h"
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <assert.h>
struct BitWriter
{
FILE *file;
uint8_t byte;
int mod;
};
BitWriter *BitWriter_init(FILE *file)
{
BitWriter *bw = malloc(sizeof(BitWriter));
assert(bw);
bw->file = file;
bw->byte = 0;
bw->mod = 0;
return bw;
}
void BitWriter_free(BitWriter *bw)
{
free(bw);
}
void BitWriter_write_bit(BitWriter *bw, bool bit)
{
bw->byte |= (bit > 0) << (bw->mod++);
if (bw->mod == 8)
{
fwrite(&bw->byte, 1, 1, bw->file);
bw->byte = 0;
bw->mod = 0;
}
}
void BitWriter_flush(BitWriter *bw)
{
while (bw->mod != 0) BitWriter_write_bit(bw, 0);
}
void BitWriter_write_bin(BitWriter *bw, uint32_t bits, int number_to_write)
{
for (int b = number_to_write - 1; b >= 0; b--)
BitWriter_write_bit(bw, bits & (1 << b));
}
void BitWriter_write_bin_reverse(BitWriter *bw, uint32_t bits, int number_to_write)
{
for (int b = 0; b < number_to_write; b++)
BitWriter_write_bit(bw, bits & (1 << b));
}
void BitWriter_write_alpha(BitWriter *bw, uint32_t byte)
{
assert(byte <= 285);
if (byte <= 143) /* 8 bit encoding */
{
uint32_t to_encode = 48 + (uint32_t) byte;
BitWriter_write_bin(bw, to_encode, 8);
}
else if (byte <= 255) /* 9 bit encoding */
{
uint32_t to_encode = 256 + (uint32_t) byte;
BitWriter_write_bin(bw, to_encode, 9);
}
else if (byte <= 279) /* 7 bit encoding */
{
uint32_t to_encode = (uint32_t) byte - 256;
BitWriter_write_bin(bw, to_encode, 7);
}
else if (byte <= 287)
{
uint32_t to_encode = (uint32_t) byte - 88;
BitWriter_write_bin(bw, to_encode, 8);
}
}
void BitWriter_write_length(BitWriter *bw, uint32_t length)
{
assert(3 <= length && length <= 258);
if (length <= 10) /* 3 - 10 */
{
BitWriter_write_alpha(bw, length + 254);
}
else if (length <= 18) /* 11 - 22 */
{
BitWriter_write_alpha(bw, (length + 519) >> 1);
BitWriter_write_bin_reverse(bw, 1 + length, 1);
}
else if (length <= 34) /* 23 - 34 */
{
BitWriter_write_alpha(bw, (length + 1057) >> 2);
BitWriter_write_bin_reverse(bw, 1 + length, 2);
}
else if (length <= 66) /* 35 - 66 */
{
BitWriter_write_alpha(bw, (length + 2149) >> 3);
BitWriter_write_bin_reverse(bw, 5 + length, 3);
}
else if (length <= 130) /* 67 - 130 */
{
BitWriter_write_alpha(bw, (length + 4365) >> 4);
BitWriter_write_bin_reverse(bw, 13 + length, 4);
}
else if (length <= 257) /* 131 - 257 */
{
BitWriter_write_alpha(bw, (length + 8861) >> 5);
BitWriter_write_bin_reverse(bw, 29 + length, 5);
}
else if (length == 258)
{
BitWriter_write_alpha(bw, 285);
}
else
{
assert(0);
}
}
void BitWriter_write_distance(BitWriter *bw, uint32_t dist)
{
assert(1 <= dist && dist <= 32768);
if (dist <= 4) BitWriter_write_bin(bw, dist - 1, 5);
else
{
int bits = 1;
while (true)
{
if (dist <= 1 << (bits + 2))
{
BitWriter_write_bin(bw, (dist + bits * (1 << (bits + 1)) - 1) >> bits, 5);
BitWriter_write_bin_reverse(bw, dist - 1, bits);
return;
}
else bits++;
}
}
}