github.com/ethereum/go-ethereum@v1.16.1/crypto/secp256k1/libsecp256k1/src/field_10x26.h (about)

     1  /***********************************************************************
     2   * Copyright (c) 2013, 2014 Pieter Wuille                              *
     3   * Distributed under the MIT software license, see the accompanying    *
     4   * file COPYING or https://www.opensource.org/licenses/mit-license.php.*
     5   ***********************************************************************/
     6  
     7  #ifndef SECP256K1_FIELD_REPR_H
     8  #define SECP256K1_FIELD_REPR_H
     9  
    10  #include <stdint.h>
    11  
    12  /** This field implementation represents the value as 10 uint32_t limbs in base
    13   *  2^26. */
    14  typedef struct {
    15     /* A field element f represents the sum(i=0..9, f.n[i] << (i*26)) mod p,
    16      * where p is the field modulus, 2^256 - 2^32 - 977.
    17      *
    18      * The individual limbs f.n[i] can exceed 2^26; the field's magnitude roughly
    19      * corresponds to how much excess is allowed. The value
    20      * sum(i=0..9, f.n[i] << (i*26)) may exceed p, unless the field element is
    21      * normalized. */
    22      uint32_t n[10];
    23      /*
    24       * Magnitude m requires:
    25       *     n[i] <= 2 * m * (2^26 - 1) for i=0..8
    26       *     n[9] <= 2 * m * (2^22 - 1)
    27       *
    28       * Normalized requires:
    29       *     n[i] <= (2^26 - 1) for i=0..8
    30       *     sum(i=0..9, n[i] << (i*26)) < p
    31       *     (together these imply n[9] <= 2^22 - 1)
    32       */
    33      SECP256K1_FE_VERIFY_FIELDS
    34  } secp256k1_fe;
    35  
    36  /* Unpacks a constant into a overlapping multi-limbed FE element. */
    37  #define SECP256K1_FE_CONST_INNER(d7, d6, d5, d4, d3, d2, d1, d0) { \
    38      (d0) & 0x3FFFFFFUL, \
    39      (((uint32_t)d0) >> 26) | (((uint32_t)(d1) & 0xFFFFFUL) << 6), \
    40      (((uint32_t)d1) >> 20) | (((uint32_t)(d2) & 0x3FFFUL) << 12), \
    41      (((uint32_t)d2) >> 14) | (((uint32_t)(d3) & 0xFFUL) << 18), \
    42      (((uint32_t)d3) >> 8) | (((uint32_t)(d4) & 0x3UL) << 24), \
    43      (((uint32_t)d4) >> 2) & 0x3FFFFFFUL, \
    44      (((uint32_t)d4) >> 28) | (((uint32_t)(d5) & 0x3FFFFFUL) << 4), \
    45      (((uint32_t)d5) >> 22) | (((uint32_t)(d6) & 0xFFFFUL) << 10), \
    46      (((uint32_t)d6) >> 16) | (((uint32_t)(d7) & 0x3FFUL) << 16), \
    47      (((uint32_t)d7) >> 10) \
    48  }
    49  
    50  typedef struct {
    51      uint32_t n[8];
    52  } secp256k1_fe_storage;
    53  
    54  #define SECP256K1_FE_STORAGE_CONST(d7, d6, d5, d4, d3, d2, d1, d0) {{ (d0), (d1), (d2), (d3), (d4), (d5), (d6), (d7) }}
    55  #define SECP256K1_FE_STORAGE_CONST_GET(d) d.n[7], d.n[6], d.n[5], d.n[4],d.n[3], d.n[2], d.n[1], d.n[0]
    56  
    57  #endif /* SECP256K1_FIELD_REPR_H */