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Add utilities for log2

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sanket1729 2023-01-30 23:46:03 -08:00
parent 17417d44f3
commit 420353d7da
2 changed files with 33 additions and 0 deletions
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13
src/modules/bulletproofs/bulletproofs_util.h
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@ -39,4 +39,17 @@ static void secp256k1_bulletproofs_le64(unsigned char *output, const uint64_t n)
output[7] = n >> 56; output[7] = n >> 56;
} }
/* Check if n is power of two*/
static int secp256k1_is_power_of_two(size_t n) {
return n > 0 && (n & (n - 1)) == 0;
}
/* Compute the log2 of n. If n is not a power of two, it returns the largest
* `k` such that 2^k <= n. Assumes n < 2^64. In Bulletproofs, this is bounded
* by len of input vectors which can be safely assumed to be less than 2^64.
*/
static size_t secp256k1_bulletproofs_pp_log2(size_t n) {
return 64 - 1 - secp256k1_clz64_var((uint64_t)n);
}
#endif #endif

20
src/modules/bulletproofs/tests_impl.h
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@ -7,6 +7,10 @@
#ifndef _SECP256K1_MODULE_BULLETPROOFS_TEST_ #ifndef _SECP256K1_MODULE_BULLETPROOFS_TEST_
#define _SECP256K1_MODULE_BULLETPROOFS_TEST_ #define _SECP256K1_MODULE_BULLETPROOFS_TEST_
#include <stdint.h>
#include "include/secp256k1_bulletproofs.h"
#include "bulletproofs_util.h"
#include "bulletproofs_pp_transcript_impl.h" #include "bulletproofs_pp_transcript_impl.h"
static void test_bulletproofs_generators_api(void) { static void test_bulletproofs_generators_api(void) {
@ -130,7 +134,23 @@ static void test_bulletproofs_pp_tagged_hash(void) {
CHECK(secp256k1_memcmp_var(output, output_cached, 32) == 0); CHECK(secp256k1_memcmp_var(output, output_cached, 32) == 0);
} }
void test_log_exp(void) {
CHECK(secp256k1_is_power_of_two(0) == 0);
CHECK(secp256k1_is_power_of_two(1) == 1);
CHECK(secp256k1_is_power_of_two(2) == 1);
CHECK(secp256k1_is_power_of_two(64) == 1);
CHECK(secp256k1_is_power_of_two(63) == 0);
CHECK(secp256k1_is_power_of_two(256) == 1);
CHECK(secp256k1_bulletproofs_pp_log2(1) == 0);
CHECK(secp256k1_bulletproofs_pp_log2(2) == 1);
CHECK(secp256k1_bulletproofs_pp_log2(255) == 7);
CHECK(secp256k1_bulletproofs_pp_log2(256) == 8);
CHECK(secp256k1_bulletproofs_pp_log2(257) == 8);
}
void run_bulletproofs_tests(void) { void run_bulletproofs_tests(void) {
test_log_exp();
test_bulletproofs_generators_api(); test_bulletproofs_generators_api();
test_bulletproofs_generators_fixed(); test_bulletproofs_generators_fixed();
test_bulletproofs_pp_tagged_hash(); test_bulletproofs_pp_tagged_hash();