isa-l/igzip/huffman.h

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#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include "igzip_lib.h"

#ifdef _MSC_VER
# include <intrin.h>
# define inline __inline
#else
# include <x86intrin.h>
#endif

static inline uint32_t bsr(uint32_t val)
{
	uint32_t msb;
#ifdef __LZCNT__
	msb = 16 - __lzcnt16(val);
#else
	for(msb = 0; val > 0; val >>= 1)
		msb++;
#endif
	return msb;
}

static inline uint32_t tzcnt(uint64_t val)
{
	uint32_t cnt;

#ifdef __x86_64__

	cnt = __builtin_ctzll(val) / 8;//__tzcnt_u64(val);

#else
	for(cnt = 8; val > 0; val <<= 8)
		cnt -= 1;
#endif
	return cnt;
}

static void compute_dist_code(struct isal_hufftables *hufftables, uint16_t dist, uint64_t *p_code, uint64_t *p_len)
{
	assert(dist > IGZIP_DIST_TABLE_SIZE);

	dist -= 1;
	uint32_t msb;
	uint32_t num_extra_bits;
	uint32_t extra_bits;
	uint32_t sym;
	uint32_t len;
	uint32_t code;

	msb = bsr(dist);
	assert(msb >= 1);
	num_extra_bits = msb - 2;
	extra_bits = dist & ((1 << num_extra_bits) - 1);
	dist >>= num_extra_bits;
	sym = dist + 2 * num_extra_bits;
	assert(sym < 30);
	code = hufftables->dcodes[sym - IGZIP_DECODE_OFFSET];
	len = hufftables->dcodes_sizes[sym - IGZIP_DECODE_OFFSET];
	*p_code = code | (extra_bits << len);
	*p_len = len + num_extra_bits;
}

static inline void get_dist_code(struct isal_hufftables *hufftables, uint32_t dist, uint64_t *code, uint64_t *len)
{
	if (dist < 1)
		dist = 0;
	assert(dist >= 1);
	assert(dist <= 32768);
	if (dist <= IGZIP_DIST_TABLE_SIZE) {
		uint64_t code_len;
		code_len = hufftables->dist_table[dist - 1];
		*code = code_len >> 5;
		*len = code_len & 0x1F;
	} else {
		compute_dist_code(hufftables, dist, code, len);
	}
}

static inline void get_len_code(struct isal_hufftables *hufftables, uint32_t length, uint64_t *code, uint64_t *len)
{
	assert(length >= 3);
	assert(length <= 258);

	uint64_t code_len;
	code_len = hufftables->len_table[length - 3];
	*code = code_len >> 5;
	*len = code_len & 0x1F;
}

static inline void get_lit_code(struct isal_hufftables *hufftables, uint32_t lit, uint64_t *code, uint64_t *len)
{
	assert(lit <= 256);

	*code = hufftables->lit_table[lit];
	*len = hufftables->lit_table_sizes[lit];
}

/**
 * @brief Returns a hash of the first 3 bytes of input data.
 */
static inline uint32_t compute_hash(uint32_t data)
{
#ifdef __SSE4_2__

	return _mm_crc32_u32(0, data);

#else
	/* Use multiplication to create a hash, 0xBDD06057 is a prime number */
	return ((uint64_t)data * 0xB2D06057) >> 16;

#endif /* __SSE4_2__ */
}


/**
 * @brief Returns how long str1 and str2 have the same symbols.
 * @param str1: First input string.
 * @param str2: Second input string.
 * @param max_length: length of the smaller string.
 */
static inline int compare258(uint8_t * str1, uint8_t * str2, uint32_t max_length)
{
	uint32_t count;
	uint64_t test;
	uint64_t loop_length;

	if(max_length > 258)
		max_length = 258;

	loop_length = max_length & ~0x7;

	for(count = 0; count < loop_length; count += 8){
		test = *(uint64_t *) str1;
		test ^= *(uint64_t *) str2;
		if(test != 0)
			return count + tzcnt(test);
		str1 += 8;
		str2 += 8;
	}

	switch(max_length % 8){

	case 7:
		if(*str1++ != *str2++)
			return count;
		count++;
	case 6:
		if(*str1++ != *str2++)
			return count;
		count++;
	case 5:
		if(*str1++ != *str2++)
			return count;
		count++;
	case 4:
		if(*str1++ != *str2++)
			return count;
		count++;
	case 3:
		if(*str1++ != *str2++)
			return count;
		count++;
	case 2:
		if(*str1++ != *str2++)
			return count;
		count++;
	case 1:
		if(*str1 != *str2)
			return count;
		count++;
	}

	return count;
}