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/**********************************************************************
* 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_FIELD_REPR_IMPL_H_
#define _SECP256K1_FIELD_REPR_IMPL_H_
#include <stdio.h>
#include <string.h>
#include "num.h"
#include "field.h"
static mp_limb_t secp256k1_field_p[FIELD_LIMBS];
static mp_limb_t secp256k1_field_pc[(33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS];
static void secp256k1_fe_inner_start(void) {
for (int i=0; i<(33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS; i++)
secp256k1_field_pc[i] = 0;
secp256k1_field_pc[0] += 0x3D1UL;
secp256k1_field_pc[32/GMP_NUMB_BITS] += (((mp_limb_t)1) << (32 % GMP_NUMB_BITS));
for (int i=0; i<FIELD_LIMBS; i++) {
secp256k1_field_p[i] = 0;
}
mpn_sub(secp256k1_field_p, secp256k1_field_p, FIELD_LIMBS, secp256k1_field_pc, (33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS);
}
static void secp256k1_fe_inner_stop(void) {
}
static void secp256k1_fe_normalize(secp256k1_fe_t *r) {
if (r->n[FIELD_LIMBS] != 0) {
#if (GMP_NUMB_BITS >= 40)
mp_limb_t carry = mpn_add_1(r->n, r->n, FIELD_LIMBS, 0x1000003D1ULL * r->n[FIELD_LIMBS]);
mpn_add_1(r->n, r->n, FIELD_LIMBS, 0x1000003D1ULL * carry);
#else
mp_limb_t carry = mpn_add_1(r->n, r->n, FIELD_LIMBS, 0x3D1UL * r->n[FIELD_LIMBS]) +
mpn_add_1(r->n+(32/GMP_NUMB_BITS), r->n+(32/GMP_NUMB_BITS), FIELD_LIMBS-(32/GMP_NUMB_BITS), r->n[FIELD_LIMBS] << (32 % GMP_NUMB_BITS));
mpn_add_1(r->n, r->n, FIELD_LIMBS, 0x3D1UL * carry);
mpn_add_1(r->n+(32/GMP_NUMB_BITS), r->n+(32/GMP_NUMB_BITS), FIELD_LIMBS-(32/GMP_NUMB_BITS), carry << (32%GMP_NUMB_BITS));
#endif
r->n[FIELD_LIMBS] = 0;
}
if (mpn_cmp(r->n, secp256k1_field_p, FIELD_LIMBS) >= 0)
mpn_sub(r->n, r->n, FIELD_LIMBS, secp256k1_field_p, FIELD_LIMBS);
}
SECP256K1_INLINE static void secp256k1_fe_set_int(secp256k1_fe_t *r, int a) {
r->n[0] = a;
for (int i=1; i<FIELD_LIMBS+1; i++)
r->n[i] = 0;
}
SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe_t *r) {
for (int i=0; i<FIELD_LIMBS+1; i++)
r->n[i] = 0;
}
SECP256K1_INLINE static int secp256k1_fe_is_zero(const secp256k1_fe_t *a) {
int ret = 1;
for (int i=0; i<FIELD_LIMBS+1; i++)
ret &= (a->n[i] == 0);
return ret;
}
SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe_t *a) {
return a->n[0] & 1;
}
SECP256K1_INLINE static int secp256k1_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
int ret = 1;
for (int i=0; i<FIELD_LIMBS+1; i++)
ret &= (a->n[i] == b->n[i]);
return ret;
}
static void secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
for (int i=0; i<FIELD_LIMBS+1; i++)
r->n[i] = 0;
for (int i=0; i<256; i++) {
int limb = i/GMP_NUMB_BITS;
int shift = i%GMP_NUMB_BITS;
r->n[limb] |= (mp_limb_t)((a[31-i/8] >> (i%8)) & 0x1) << shift;
}
}
/** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */
static void secp256k1_fe_get_b32(unsigned char *r, const secp256k1_fe_t *a) {
for (int i=0; i<32; i++) {
int c = 0;
for (int j=0; j<8; j++) {
int limb = (8*i+j)/GMP_NUMB_BITS;
int shift = (8*i+j)%GMP_NUMB_BITS;
c |= ((a->n[limb] >> shift) & 0x1) << j;
}
r[31-i] = c;
}
}
SECP256K1_INLINE static void secp256k1_fe_negate(secp256k1_fe_t *r, const secp256k1_fe_t *a, int m) {
(void)m;
*r = *a;
secp256k1_fe_normalize(r);
for (int i=0; i<FIELD_LIMBS; i++)
r->n[i] = ~(r->n[i]);
#if (GMP_NUMB_BITS >= 33)
mpn_sub_1(r->n, r->n, FIELD_LIMBS, 0x1000003D0ULL);
#else
mpn_sub_1(r->n, r->n, FIELD_LIMBS, 0x3D0UL);
mpn_sub_1(r->n+(32/GMP_NUMB_BITS), r->n+(32/GMP_NUMB_BITS), FIELD_LIMBS-(32/GMP_NUMB_BITS), 0x1UL << (32%GMP_NUMB_BITS));
#endif
}
SECP256K1_INLINE static void secp256k1_fe_mul_int(secp256k1_fe_t *r, int a) {
mpn_mul_1(r->n, r->n, FIELD_LIMBS+1, a);
}
SECP256K1_INLINE static void secp256k1_fe_add(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
mpn_add(r->n, r->n, FIELD_LIMBS+1, a->n, FIELD_LIMBS+1);
}
static void secp256k1_fe_reduce(secp256k1_fe_t *r, mp_limb_t *tmp) {
/** <A1 A2 A3 A4> <B1 B2 B3 B4>
* B1 B2 B3 B4
* + C * A1 A2 A3 A4
* + A1 A2 A3 A4
*/
#if (GMP_NUMB_BITS >= 33)
mp_limb_t o = mpn_addmul_1(tmp, tmp+FIELD_LIMBS, FIELD_LIMBS, 0x1000003D1ULL);
#else
mp_limb_t o = mpn_addmul_1(tmp, tmp+FIELD_LIMBS, FIELD_LIMBS, 0x3D1UL) +
mpn_addmul_1(tmp+(32/GMP_NUMB_BITS), tmp+FIELD_LIMBS, FIELD_LIMBS-(32/GMP_NUMB_BITS), 0x1UL << (32%GMP_NUMB_BITS));
#endif
mp_limb_t q[1+(33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS];
q[(33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS] = mpn_mul_1(q, secp256k1_field_pc, (33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS, o);
#if (GMP_NUMB_BITS <= 32)
mp_limb_t o2 = tmp[2*FIELD_LIMBS-(32/GMP_NUMB_BITS)] << (32%GMP_NUMB_BITS);
q[(33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS] += mpn_addmul_1(q, secp256k1_field_pc, (33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS, o2);
#endif
r->n[FIELD_LIMBS] = mpn_add(r->n, tmp, FIELD_LIMBS, q, 1+(33+GMP_NUMB_BITS-1)/GMP_NUMB_BITS);
}
static void secp256k1_fe_mul(secp256k1_fe_t *r, const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
secp256k1_fe_t ac = *a;
secp256k1_fe_t bc = *b;
secp256k1_fe_normalize(&ac);
secp256k1_fe_normalize(&bc);
mp_limb_t tmp[2*FIELD_LIMBS];
mpn_mul_n(tmp, ac.n, bc.n, FIELD_LIMBS);
secp256k1_fe_reduce(r, tmp);
}
static void secp256k1_fe_sqr(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
secp256k1_fe_t ac = *a;
secp256k1_fe_normalize(&ac);
mp_limb_t tmp[2*FIELD_LIMBS];
mpn_sqr(tmp, ac.n, FIELD_LIMBS);
secp256k1_fe_reduce(r, tmp);
}
#endif
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