deb-libisal/igzip/bitbuf2.h

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#ifndef BITBUF2_H
#define BITBUF2_H

#include "igzip_lib.h"

/* bit buffer types
 * BITBUF8: (e) Always write 8 bytes of data
 * BITBUFB: (b) Always write data
 */
#if !(defined(USE_BITBUFB) || defined(USE_BITBUF8) || defined(USE_BITBUF_ELSE))
# define USE_BITBUFB
#endif

#if defined (__unix__) || (__APPLE__)
#define _mm_stream_si64x(dst, src) *((uint64_t*)dst) = src
#else
#include <intrin.h>
#endif

#ifdef _WIN64
#pragma warning(disable: 4996)
#endif

#ifdef _MSC_VER
#define inline __inline
#endif


/* MAX_BITBUF_BIT WRITE is the maximum number of bits than can be safely written
 * by consecutive calls of write_bits. Note this assumes the bitbuf is in a
 * state that is possible at the exit of write_bits */
#ifdef USE_BITBUF8 /*Write bits safe */
# define MAX_BITBUF_BIT_WRITE 63
#elif defined(USE_BITBUFB) /* Write bits always */
# define MAX_BITBUF_BIT_WRITE 56
#else /* USE_BITBUF_ELSE */
# define MAX_BITBUF_BIT_WRITE 56
#endif


static
 inline void construct(struct BitBuf2 *me)
{
	me->m_bits = 0;
	me->m_bit_count = 0;
	me->m_out_buf = me->m_out_start = me->m_out_end = NULL;
}

static inline void init(struct BitBuf2 *me)
{
	me->m_bits = 0;
	me->m_bit_count = 0;
}

static inline void set_buf(struct BitBuf2 *me, unsigned char *buf, unsigned int len)
{
	unsigned int slop = 8;
	me->m_out_buf = me->m_out_start = buf;
	me->m_out_end = buf + len - slop;
}

static inline int is_full(struct BitBuf2 *me)
{
	return (me->m_out_buf > me->m_out_end);
}

static inline uint8_t * buffer_ptr(struct BitBuf2 *me)
{
	return me->m_out_buf;
}

static inline uint32_t buffer_used(struct BitBuf2 *me)
{
	return (uint32_t)(me->m_out_buf - me->m_out_start);
}

static inline void check_space(struct BitBuf2 *me, uint32_t num_bits)
{
	/* Checks if bitbuf has num_bits extra space and flushes the bytes in
	 * the bitbuf if it doesn't. */
	uint32_t bytes;
	if (63 - me->m_bit_count < num_bits) {
		_mm_stream_si64x((int64_t *) me->m_out_buf, me->m_bits);
		bytes = me->m_bit_count / 8;
		me->m_out_buf += bytes;
		bytes *= 8;
		me->m_bit_count -= bytes;
		me->m_bits >>= bytes;
	}
}

static inline void write_bits_unsafe(struct BitBuf2 *me, uint64_t code, uint32_t count)
{
	me->m_bits |= code << me->m_bit_count;
	me->m_bit_count += count;
}

static inline void write_bits(struct BitBuf2 *me, uint64_t code, uint32_t count)
{
#ifdef USE_BITBUF8 /*Write bits safe */
	me->m_bits |= code << me->m_bit_count;
	me->m_bit_count += count;
	if (me->m_bit_count >= 64) {
		_mm_stream_si64x((int64_t *) me->m_out_buf, me->m_bits);
		me->m_out_buf += 8;
		me->m_bit_count -= 64;
		me->m_bits = code >> (count - me->m_bit_count);
	}
#elif defined(USE_BITBUFB) /* Write bits always */
	/* Assumes there is space to fit code into m_bits. */
	uint32_t bits;
	me->m_bits |= code << me->m_bit_count;
	me->m_bit_count += count;
	if (me->m_bit_count >= 8) {
		_mm_stream_si64x((int64_t *) me->m_out_buf, me->m_bits);
		bits = me->m_bit_count & ~7;
		me->m_bit_count -= bits;
		me->m_out_buf += bits/8;
		me->m_bits >>= bits;
	}
#else /* USE_BITBUF_ELSE */
	check_space(me, count);
	write_bits_unsafe(me, code, count);
#endif

}

/* Can write up to 8 bytes to output buffer */
static inline void flush(struct BitBuf2 *me)
{
	uint32_t bytes;
	if (me->m_bit_count) {
		_mm_stream_si64x((int64_t *) me->m_out_buf, me->m_bits);
		bytes = (me->m_bit_count + 7) / 8;
		me->m_out_buf += bytes;
	}
	me->m_bits = 0;
	me->m_bit_count = 0;
}

#endif //BITBUF2_H