lightning/secp256k1/src/testrand_impl.h

/**********************************************************************
 * Copyright (c) 2013, 2014 Pieter Wuille                             *
 * Distributed under the MIT software license, see the accompanying   *
 * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
 **********************************************************************/

#ifndef _SECP256K1_TESTRAND_IMPL_H_
#define _SECP256K1_TESTRAND_IMPL_H_

#include <stdint.h>
#include <string.h>

#include "testrand.h"
#include "hash.h"

static secp256k1_rfc6979_hmac_sha256_t secp256k1_test_rng;
static uint32_t secp256k1_test_rng_precomputed[8];
static int secp256k1_test_rng_precomputed_used = 8;

SECP256K1_INLINE static void secp256k1_rand_seed(const unsigned char *seed16) {
    secp256k1_rfc6979_hmac_sha256_initialize(&secp256k1_test_rng, seed16, 16);
}

SECP256K1_INLINE static uint32_t secp256k1_rand32(void) {
    if (secp256k1_test_rng_precomputed_used == 8) {
        secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, (unsigned char*)(&secp256k1_test_rng_precomputed[0]), sizeof(secp256k1_test_rng_precomputed));
        secp256k1_test_rng_precomputed_used = 0;
    }
    return secp256k1_test_rng_precomputed[secp256k1_test_rng_precomputed_used++];
}

static void secp256k1_rand256(unsigned char *b32) {
    secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, b32, 32);
}

static void secp256k1_rand256_test(unsigned char *b32) {
    int bits=0;
    uint64_t ent = 0;
    int entleft = 0;
    memset(b32, 0, 32);
    while (bits < 256) {
        int now;
        uint32_t val;
        if (entleft < 12) {
            ent |= ((uint64_t)secp256k1_rand32()) << entleft;
            entleft += 32;
        }
        now = 1 + ((ent % 64)*((ent >> 6) % 32)+16)/31;
        val = 1 & (ent >> 11);
        ent >>= 12;
        entleft -= 12;
        while (now > 0 && bits < 256) {
            b32[bits / 8] |= val << (bits % 8);
            now--;
            bits++;
        }
    }
}

#endif