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Diffstat (limited to 'src/plugins/ioam/lib-pot/math64.h')
| -rw-r--r-- | src/plugins/ioam/lib-pot/math64.h | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/src/plugins/ioam/lib-pot/math64.h b/src/plugins/ioam/lib-pot/math64.h new file mode 100644 index 00000000..4c608a37 --- /dev/null +++ b/src/plugins/ioam/lib-pot/math64.h @@ -0,0 +1,159 @@ +/* + * math64.h provides the 64 bit unsigned integer add, multiply followed by modulo operation + * The linux/math64.h provides divide and multiply 64 bit integers but: + * 1. multiply: mul_u64_u64_shr - only returns 64 bits of the result and has to be called + * twice to get the complete 128 bits of the result. + * 2. Modulo operation of the result of addition and multiplication of u64 that may result + * in integers > 64 bits is not supported + * Hence this header to combine add/multiply followed by modulo of u64 integrers + * always resulting in u64. + * + * Copyright (c) 2016 Cisco and/or its affiliates. + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at: + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +#ifndef include_vnet_math64_h +#define include_vnet_math64_h +#include <stdint.h> + +/* + * multiplies and returns result in hi and lo + */ +static inline void mul64by64(u64 a, u64 b, u64 * hi, u64 * lo) +{ + u64 a_lo = (u64) (uint32_t) a; + u64 a_hi = a >> 32; + u64 b_lo = (u64) (u32) b; + u64 b_hi = b >> 32; + + u64 p0 = a_lo * b_lo; + u64 p1 = a_lo * b_hi; + u64 p2 = a_hi * b_lo; + u64 p3 = a_hi * b_hi; + + u32 cy = (u32) (((p0 >> 32) + (u32) p1 + (u32) p2) >> 32); + + *lo = p0 + (p1 << 32) + (p2 << 32); + *hi = p3 + (p1 >> 32) + (p2 >> 32) + cy; + return; +} + +#define TWO64 18446744073709551616.0 + +static inline u64 mod128by64(u64 x, u64 y, u64 m, double di) +{ + u64 q1, q2, q; + u64 p1, p0; + double dq; + + /* calculate quotient first pass 53 bits */ + dq = (TWO64 * (double)x + (double)y) * di; + + if (dq >= TWO64) + q1 = 0xfffffffffffff800L; + else + q1 = dq; + + /* q1 * m to compare the product to the dividend. */ + mul64by64(q1, m, &p1, &p0); + + /* Adjust quotient. is it > actual result: */ + if (x < p1 || (x == p1 && y < p0)) + { + /* q1 > quotient. calculate abs remainder */ + x = p1 - (x + (p0 < y)); + y = p0 - y; + + /* use the remainder as new dividend to adjust quotient */ + q2 = (u64) ((TWO64 * (double)x + (double)y) * di); + mul64by64(q2, m, &p1, &p0); + + q = q1 - q2; + if (x < p1 || (x == p1 && y <= p0)) + { + y = p0 - y; + } + else + { + y = p0 - y; + y += m; + q--; + } + } + else + { + x = x - (p1 + (y < p0)); + y = y - p0; + + q2 = (u64) ((TWO64 * (double)x + (double)y) * di); + mul64by64(q2, m, &p1, &p0); + + q = q1 + q2; + if (x < p1 || (x == p1 && y < p0)) + { + y = y - p0; + y += m; + q--; + } + else + { + y = y - p0; + if (y >= m) + { + y -= m; + q++; + } + } + } + + return y; +} + +/* + * returns a % p + */ +static inline u64 mod64by64(u64 a, u64 p, u64 primeinv) +{ + return (mod128by64(0, a, p, primeinv)); +} + +static inline void add64(u64 a, u64 b, u64 * whi, u64 * wlo) +{ + *wlo = a + b; + if (*wlo < a) + *whi = 1; + +} + +/* + * returns (a + b)%p + */ +static inline u64 add64_mod(u64 a, u64 b, u64 p, double pi) +{ + u64 shi = 0, slo = 0; + + add64(a, b, &shi, &slo); + return (mod128by64(shi, slo, p, pi)); +} + +/* + * returns (ab) % p + */ +static inline u64 mul64_mod(u64 a, u64 b, u64 p, double pi) +{ + u64 phi = 0, plo = 0; + + mul64by64(a, b, &phi, &plo); + return (mod128by64(phi, plo, p, pi)); +} + +#endif |