precompute_ecmult_gen.c

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/*********************************************************************************
 * Copyright (c) 2013, 2014, 2015, 2021 Thomas Daede, Cory Fields, Pieter Wuille *
 * Distributed under the MIT software license, see the accompanying              *
 * file COPYING or https://www.opensource.org/licenses/mit-license.php.          *
 *********************************************************************************/

#include <inttypes.h>
#include <stdio.h>

#include "../include/secp256k1.h"

#include "assumptions.h"
#include "util.h"

#include "group.h"
#include "int128_impl.h"
#include "ecmult_gen.h"
#include "ecmult_gen_compute_table_impl.h"

static const int CONFIGS[][2] = {
    {2, 5},
    {11, 6},
    {43, 6}
};

static void print_table(FILE* fp, int blocks, int teeth) {
    int spacing = CEIL_DIV(256, blocks * teeth);
    size_t points = ((size_t)1) << (teeth - 1);
    int outer;
    size_t inner;

    secp256k1_ge_storage* table = checked_malloc(&default_error_callback, blocks * points * sizeof(secp256k1_ge_storage));
    secp256k1_ecmult_gen_compute_table(table, &secp256k1_ge_const_g, blocks, teeth, spacing);

    fprintf(fp, "#elif (COMB_BLOCKS == %d) && (COMB_TEETH == %d) && (COMB_SPACING == %d)\n", blocks, teeth, spacing);
    for (outer = 0; outer != blocks; outer++) {
        fprintf(fp,"{");
        for (inner = 0; inner != points; inner++) {
            fprintf(fp, "S(%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32
                        ",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32",%"PRIx32")",
                    SECP256K1_GE_STORAGE_CONST_GET(table[outer * points + inner]));
            if (inner != points - 1) {
                fprintf(fp,",\n");
            }
        }
        if (outer != blocks - 1) {
            fprintf(fp,"},\n");
        } else {
            fprintf(fp,"}\n");
        }
    }
    free(table);
}

int main(int argc, char **argv) {
    const char outfile[] = "src/precomputed_ecmult_gen.c";
    FILE* fp;
    size_t config;
    int did_current_config = 0;

    (void)argc;
    (void)argv;

    fp = fopen(outfile, "w");
    if (fp == NULL) {
        fprintf(stderr, "Could not open %s for writing!\n", outfile);
        return -1;
    }

    fprintf(fp, "/* This file was automatically generated by precompute_ecmult_gen. */\n");
    fprintf(fp, "/* See ecmult_gen_impl.h for details about the contents of this file. */\n");
    fprintf(fp, "#include \"group.h\"\n");
    fprintf(fp, "#include \"ecmult_gen.h\"\n");
    fprintf(fp, "#include \"precomputed_ecmult_gen.h\"\n");
    fprintf(fp, "#ifdef EXHAUSTIVE_TEST_ORDER\n");
    fprintf(fp, "#    error Cannot compile precomputed_ecmult_gen.c in exhaustive test mode\n");
    fprintf(fp, "#endif /* EXHAUSTIVE_TEST_ORDER */\n");
    fprintf(fp, "#define S(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p) SECP256K1_GE_STORAGE_CONST(0x##a##u,0x##b##u,0x##c##u,0x##d##u,0x##e##u,0x##f##u,0x##g##u,0x##h##u,0x##i##u,0x##j##u,0x##k##u,0x##l##u,0x##m##u,0x##n##u,0x##o##u,0x##p##u)\n");

    fprintf(fp, "const secp256k1_ge_storage secp256k1_ecmult_gen_prec_table[COMB_BLOCKS][COMB_POINTS] = {\n");
    fprintf(fp, "#if 0\n");
    for (config = 0; config < sizeof(CONFIGS) / sizeof(*CONFIGS); ++config) {
        print_table(fp, CONFIGS[config][0], CONFIGS[config][1]);
        if (CONFIGS[config][0] == COMB_BLOCKS && CONFIGS[config][1] == COMB_TEETH) {
            did_current_config = 1;
        }
    }
    if (!did_current_config) {
        print_table(fp, COMB_BLOCKS, COMB_TEETH);
    }
    fprintf(fp, "#else\n");
    fprintf(fp, "#    error Configuration mismatch, invalid COMB_* parameters. Try deleting precomputed_ecmult_gen.c before the build.\n");
    fprintf(fp, "#endif\n");

    fprintf(fp, "};\n");
    fprintf(fp, "#undef S\n");
    fclose(fp);

    return 0;
}