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// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include <vespa/vespalib/util/binary_hamming_distance.h>
#include <vespa/vespalib/util/require.h>
#include <vespa/vespalib/gtest/gtest.h>
#include <cstdlib>
#include <cstring>
using namespace vespalib;
constexpr size_t ALIGN = 8;
constexpr size_t SZ = 64;
void flip_one_bit(void *memory, void *other) {
auto buf = (uint8_t *)memory;
auto cmp = (uint8_t *)other;
while (true) {
size_t byte_idx = random() % SZ;
size_t bit_idx = random() % 8;
uint8_t lookaside = cmp[byte_idx];
uint8_t old = buf[byte_idx];
uint8_t bit = 1u << bit_idx;
if ((old & bit) == (lookaside & bit)) {
uint8_t new_val = old ^ bit;
REQUIRE(old != new_val);
buf[byte_idx] = new_val;
return;
}
}
}
void *my_alloc(int unalignment = 0) {
void *mem;
int r = posix_memalign(&mem, ALIGN, SZ*2);
REQUIRE_EQ(0, r);
uintptr_t addr = (uintptr_t) mem;
addr += unalignment;
return (void *)addr;
}
void check_with_flipping(void *mem_a, void *mem_b) {
memset(mem_a, 0, SZ);
memset(mem_b, 0, SZ);
size_t dist = 0;
EXPECT_EQ(binary_hamming_distance(mem_a, mem_b, SZ), dist);
while (dist < 100) {
flip_one_bit(mem_a, mem_b);
++dist;
EXPECT_EQ(binary_hamming_distance(mem_a, mem_b, SZ), dist);
flip_one_bit(mem_b, mem_a);
++dist;
EXPECT_EQ(binary_hamming_distance(mem_a, mem_b, SZ), dist);
}
}
TEST(BinaryHammingTest, aligned_usage) {
void *mem_a = my_alloc(0);
void *mem_b = my_alloc(0);
check_with_flipping(mem_a, mem_b);
}
TEST(BinaryHammingTest, one_unaligned) {
void *mem_a = my_alloc(3);
void *mem_b = my_alloc(0);
check_with_flipping(mem_a, mem_b);
}
TEST(BinaryHammingTest, other_unaligned) {
void *mem_a = my_alloc(0);
void *mem_b = my_alloc(7);
check_with_flipping(mem_a, mem_b);
}
TEST(BinaryHammingTest, both_unaligned) {
void *mem_a = my_alloc(2);
void *mem_b = my_alloc(6);
check_with_flipping(mem_a, mem_b);
}
GTEST_MAIN_RUN_ALL_TESTS()
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