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/*
* Copyright © 2018 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#ifndef UTIL_BIGMATH_H
#define UTIL_BIGMATH_H
#include "macros.h"
#include <assert.h>
#include <stdint.h>
#include <string.h>
static inline bool
_ubm_add_u32arr(uint32_t *dst, unsigned dst_len,
uint32_t *a, unsigned a_len,
uint32_t *b, unsigned b_len)
{
uint32_t carry = 0;
for (unsigned i = 0; i < dst_len; i++) {
uint64_t sum = carry;
if (i < a_len)
sum += a[i];
if (i < b_len)
sum += b[i];
dst[i] = sum;
carry = sum >> 32;
}
/* Now compute overflow */
for (unsigned i = dst_len; i < a_len; i++) {
if (a[i])
return true;
}
for (unsigned i = dst_len; i < b_len; i++) {
if (b[i])
return true;
}
return carry;
}
#define ubm_add_u32arr(dst, a, b) \
_ubm_add_u32arr(dst, ARRAY_SIZE(dst), a, ARRAY_SIZE(a), b, ARRAY_SIZE(b))
static inline bool
_ubm_mul_u32arr(uint32_t *dst, unsigned dst_len,
uint32_t *a, unsigned a_len,
uint32_t *b, unsigned b_len)
{
memset(dst, 0, dst_len * sizeof(*dst));
bool overflow = false;
for (unsigned i = 0; i < a_len; i++) {
uint32_t carry = 0;
for (unsigned j = 0; j < b_len; j++) {
/* The maximum values of a[i] and b[i] are UINT32_MAX so the maximum
* value of tmp is UINT32_MAX * UINT32_MAX. The maximum value that
* will fit in tmp is
*
* UINT64_MAX = UINT32_MAX << 32 + UINT32_MAX
* = UINT32_MAX * (UINT32_MAX + 1) + UINT32_MAX
* = UINT32_MAX * UINT32_MAX + 2 * UINT32_MAX
*
* so we're guaranteed that we can add in two more 32-bit values
* without overflowing tmp.
*/
uint64_t tmp = (uint64_t)a[i] * (uint64_t)b[j];
tmp += carry;
if (i + j < dst_len) {
tmp += dst[i + j];
dst[i + j] = tmp;
carry = tmp >> 32;
} else {
/* We're trying to write a value that doesn't fit */
overflow = overflow || tmp > 0;
break;
}
}
if (i + b_len < dst_len)
dst[i + b_len] = carry;
else
overflow = overflow || carry > 0;
}
return overflow;
}
#define ubm_mul_u32arr(dst, a, b) \
_ubm_mul_u32arr(dst, ARRAY_SIZE(dst), a, ARRAY_SIZE(a), b, ARRAY_SIZE(b))
#endif /* UTIL_BIGMATH_H */
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