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WIP: Simulated int128 type.
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3 files changed

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‎src/int128.h

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#ifndef SECP256K1_INT128_H
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#define SECP256K1_INT128_H
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#include <stdint.h>
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#include "util.h"
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/*
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#ifdef UINT128_MAX
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#undef UINT128_MAX
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*/
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#if defined(UINT128_MAX)
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typedef uint128_t secp256k1_uint128;
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typedef int128_t secp256k1_int128;
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#else
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typedef struct {
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uint64_t lo;
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uint64_t hi;
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} secp256k1_uint128;
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typedef secp256k1_uint128 secp256k1_int128;
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#endif
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#if defined(_M_X64) | defined(_M_ARM64) | defined(_WIN64) /* MSVC */
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#include <intrin.h>
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#define secp256k1_umulh __umulh
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#define secp256k1_mulh __mulh
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#else
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static SECP256K1_INLINE uint64_t secp256k1_umulh(uint64_t a, uint64_t b) {
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#if defined(UINT128_MAX)
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return (uint64_t)(((uint128_t)a * b) >> 64);
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#else
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uint64_t t1 = (uint64_t)(uint32_t)a * (uint32_t)b;
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uint64_t t2 = (a >> 32) * (uint32_t)b;
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uint64_t t3 = (uint32_t)a*(b >> 32) + (t1 >> 32) + (uint32_t)t2;
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return (a >> 32)*(b >> 32) + (t2 >> 32) + (t3 >> 32);
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#endif
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}
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static SECP256K1_INLINE int64_t secp256k1_mulh(int64_t a, int64_t b) {
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#if defined(UINT128_MAX)
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return (int64_t)(((int128_t)a * b) >> 64);
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#else
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uint64_t t1 = (uint64_t)(uint32_t)a * (uint32_t)b;
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int64_t t2 = (a >> 32) * (uint32_t)b;
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int64_t t3 = (uint32_t)a * (b >> 32);
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uint64_t t4 = (t1 >> 32) + (uint32_t)t2 + (uint32_t)t3;
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return (a >> 32) * (b >> 32) + (t2 >> 32) + (t3 >> 32) + (int64_t)(t4 >> 32);
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#endif
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}
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#endif
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static SECP256K1_INLINE void secp256k1_u128_mul(secp256k1_uint128 *r, uint64_t a, uint64_t b) {
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#if defined(UINT128_MAX)
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*r = (uint128_t)a * b;
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#else
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r->hi = secp256k1_umulh(a, b);
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r->lo += a * b;
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#endif
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}
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static SECP256K1_INLINE void secp256k1_u128_accum_mul(secp256k1_uint128 *r, uint64_t a, uint64_t b) {
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#if defined(UINT128_MAX)
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*r += (uint128_t)a * b;
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#else
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uint64_t lo = a * b;
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r->hi += secp256k1_umulh(a, b) + (r->lo > ~lo);
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r->lo += lo;
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#endif
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}
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static SECP256K1_INLINE void secp256k1_u128_accum_u64(secp256k1_uint128 *r, uint64_t a) {
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#if defined(UINT128_MAX)
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*r += a;
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#else
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r->hi += (r->lo > ~a);
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r->lo += a;
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#endif
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}
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/* Unsigned (logical) right shift.
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* Non-constant time in b.
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*/
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static SECP256K1_INLINE void secp256k1_u128_rshift(secp256k1_uint128 *r, unsigned int b) {
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#if defined(UINT128_MAX)
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*r >>= b;
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#else
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if (b >= 64) {
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r->lo = (r->hi) >> (b-64);
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r->hi = 0;
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} else if (b > 0) {
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r->lo = ((r->hi & (((uint64_t)1<<b)-1)) << (64-b)) | r->lo >> b;
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r->hi >>= b;
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}
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#endif
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}
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static SECP256K1_INLINE uint64_t secp256k1_u128_to_u64(const secp256k1_uint128 *a) {
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#if defined(UINT128_MAX)
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return (uint64_t)(*a);
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#else
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return a->lo;
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#endif
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}
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static SECP256K1_INLINE void secp256k1_u128_from_u64(secp256k1_uint128 *r, uint64_t a) {
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#if defined(UINT128_MAX)
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*r = a;
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#else
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r->hi = 0;
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r->lo = a;
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#endif
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}
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static SECP256K1_INLINE void secp256k1_i128_mul(secp256k1_int128 *r, int64_t a, int64_t b) {
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#if defined(UINT128_MAX)
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*r = (int128_t)a * b;
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#else
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r->hi = (uint64_t)secp256k1_mulh(a, b);
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r->lo = (uint64_t)a * (uint64_t)b;
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#endif
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}
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static SECP256K1_INLINE void secp256k1_i128_accum_mul(secp256k1_int128 *r, int64_t a, int64_t b) {
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#if defined(UINT128_MAX)
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*r += (int128_t)a * b;
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#else
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uint64_t lo = (uint64_t)a * (uint64_t)b;
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r->hi += (uint64_t)secp256k1_mulh(a, b) + (r->lo > ~lo);
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r->lo += lo;
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#endif
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}
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/* Signed (arithmetic) right shift.
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* Non-constant time in b.
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*/
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static SECP256K1_INLINE void secp256k1_i128_rshift(secp256k1_int128 *r, unsigned int b) {
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#if defined(UINT128_MAX)
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*r >>= b;
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#else
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if (b >= 64) {
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r->lo = (uint64_t)((int64_t)(r->hi) >> (b-64));
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r->hi = (uint64_t)((int64_t)(r->hi) >> 63);
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} else if (b > 0) {
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r->lo = ((r->hi & (((uint64_t)1<<b)-1)) << (64-b)) | r->lo >> b;
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r->hi = (uint64_t)((int64_t)(r->hi) >> b);
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}
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#endif
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}
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static SECP256K1_INLINE int64_t secp256k1_i128_to_i64(const secp256k1_int128 *a) {
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#if defined(UINT128_MAX)
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return (int64_t)(uint64_t)(*a);
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#else
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return (int64_t)a->lo;
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#endif
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}
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static SECP256K1_INLINE void secp256k1_i128_from_i64(secp256k1_int128 *r, int64_t a) {
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#if defined(UINT128_MAX)
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*r = a;
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#else
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r->hi = (uint64_t)(a >> 63);
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r->lo = (uint64_t)a;
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#endif
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}
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static SECP256K1_INLINE int secp256k1_i128_eq(const secp256k1_int128 *a, const secp256k1_int128 *b) {
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#if defined(UINT128_MAX)
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return *a == *b;
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#else
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return a->hi == b->hi && a->lo == b->lo;
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#endif
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}
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/*
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#endif
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#define UINT128_MAX ((uint128_t)(int128_t)(-1))
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*/
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#endif

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