random.h File Reference

#include <inttypes.h>
#include "../common/namespace.h"

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Macros
#define	random_boundedl1   COMMON(random_boundedl1)
#define	random_coin   COMMON(random_coin)

Functions
int64_t	random_coin (uint64_t num, uint64_t den)
void	random_wombats (uint8_t *key, const long long numkeys, const long long batch_start, const long long batch_stop, const long long batch_sumykeys)

Macro Definition Documentation

random_boundedl1

#define random_boundedl1   COMMON(random_boundedl1)

Definition at line 7 of file random.h.

random_coin

#define random_coin   COMMON(random_coin)

Definition at line 8 of file random.h.

Function Documentation

random_coin()

int64_t random_coin	(	uint64_t	num,
		uint64_t	den )

Definition at line 198 of file random.c.

{
    uint8_t buf[32];
    uint64_t r = 0;
 
    randombytes(buf, sizeof buf);
 
    for (long long i = 0; i < 256; ++i)
    {
        uint64_t bit = 1 & (buf[i / 8] >> (i & 7));
        r <<= 1;
        r += bit;
        r ^= (~uint64mask_lessthan(r, den)) & (r ^ (r - den));
    }
    // XXX: speed this up
 
    return uint64mask_lessthan(r, num);
}

References i, num, and randombytes().

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random_wombats()

void random_wombats	(	uint8_t *	key,
		const long long	numkeys,
		const long long	batch_start,
		const long long	batch_stop,
		const long long	batch_sumykeys )

Definition at line 15 of file random.c.

{
    int32_t batch_len = batch_stop - batch_start;
    int32_t r[4 * batch_len];
    uint8_t ells[numkeys];
    for (;;)
    { /* rejection-sampling loop */
        randombytes(r, 4 * batch_len);
        for (long long j = 0; j < batch_len; ++j)
            r[j] &= ~1;
        for (long long j = 0; j < numkeys; ++j)
            r[j] |= 1;
        int32_sort(r, batch_len);
 
        long long collision = 0;
        for (long long j = 1; j < numkeys; ++j)
            collision |= int32mask_zero((r[j] ^ r[j - 1]) & ~1);
 
#ifdef ENABLE_CT_TESTING
        VALGRIND_MAKE_MEM_DEFINED(&collision, sizeof(collision));
#endif
        if (collision)
            continue;
 
        for (int32_t j = 0; j < numkeys; ++j)
            ells[j] = 0;
 
        for (int32_t j = 0; j < batch_len; ++j)
            r[j] &= 1;
 
        for (int32_t i = 0; i < numkeys; ++i)
        {
            for (int32_t j = i; j < batch_len; ++j)
            {
                // r[j] &= 1;
                int32_t updatemask = int32mask_zero(ells[i]) & int32mask_nonzero(r[j]);
                r[j] ^= (1 & updatemask);
                ells[i] |= (updatemask & (j + 1));
            }
        }
 
        for (int32_t i = 0; i < numkeys; ++i)
            key[batch_sumykeys + i] = batch_start + ells[i] - 1;
 
        return;
    }
}

References batch_start, batch_stop, i, int32_sort, j, and randombytes().

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