src/lib/bits.h

	bits.h revision cbc01fc844fa307e565cc81fd78536d7afca05a9
#ifndef BITS_H
#define BITS_H

/* default lib includes */
#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "macros.h"

#include <limits.h>
#include <stddef.h>
#include <stdint.h>

#define UINT64_SUM_OVERFLOWS(a, b) \
    (a > (uint64_t)-1 - b)

size_t nearest_power(size_t num) ATTR_CONST;

unsigned int bits_required8(uint8_t num) ATTR_CONST;

static inline
unsigned int bits_required16(uint16_t num)
{
    return (num <= 0xff) ? bits_required8(num)
        : 8 + bits_required16(num >> 8);
}
static inline
unsigned int bits_required32(uint32_t num)
{
    return (num <= 0xffff) ? bits_required16(num)
        : 16 + bits_required16(num >> 16);
}
static inline
unsigned int bits_required64(uint64_t num)
{
    return (num <= 0xffffffff) ? bits_required32(num)
        : 32 + bits_required32(num >> 32);
}

#endif