src/lib/test-bits.c

	test-bits.c revision 02c335c23bf5fa225a467c19f2c063fb0dc7b8c3
/* Copyright (c) 2001-2016 Dovecot authors, see the included COPYING file */

/* Unit tests for bit twiddles library */

#include "test-lib.h"

#include <stdio.h>

/* nearest_power(0) = error      bits_requiredXX(0) = 0
   nearest_power(1) = 1 = 1<<0   bits_requiredXX(1) = 1
   nearest_power(2) = 2 = 1<<1   bits_requiredXX(2) = 2
   nearest_power(3) = 4 = 1<<2   bits_requiredXX(3) = 2
   nearest_power(4) = 4 = 1<<2   bits_requiredXX(4) = 3
   nearest_power(5) = 8 = 1<<3   bits_requiredXX(5) = 3
   nearest_power(7) = 8 = 1<<3   bits_requiredXX(7) = 3
   nearest_power(8) = 8 = 1<<3   bits_requiredXX(8) = 4
*/

/* nearest_power(num) == 1ULL << bits_required64(num-1) */
static void test_nearest_power(void)
{
    unsigned int b;
    size_t num;
    test_begin("nearest_power()");
    test_assert(nearest_power(1)==1);
    test_assert(nearest_power(2)==2);
    for (b = 2; b < CHAR_BIT*sizeof(size_t) - 1; ++b) {
        /* b=2 tests 3,4,5; b=3 tests 7,8,9; ... b=30 tests ~1G */
        num = (size_t)1 << b;
        test_assert_idx(nearest_power(num-1) == num,    b);
        test_assert_idx(nearest_power(num  ) == num,    b);
        test_assert_idx(nearest_power(num+1) == num<<1, b);
    }
    /* With 32-bit size_t, now: b=31 tests 2G-1, 2G, not 2G+1. */
    num = (size_t)1 << b;
    test_assert_idx(nearest_power(num-1) == num,    b);
    test_assert_idx(nearest_power(num  ) == num,    b);
    /* i_assert()s: test_assert_idx(nearest_power(num+1) == num<<1, b); */
    test_end();
}

static void test_bits_requiredXX(void)
{
    /* As ..64 depends on ..32 and tests it twice,
     * and ..32 depends on ..16 and tests it twice,
     * etc., we only test ..64
     */
    unsigned int b;
    test_begin("bits_requiredXX()");
    test_assert(bits_required64(0) == 0);
    test_assert(bits_required64(1) == 1);
    test_assert(bits_required64(2) == 2);
    for (b = 2; b < 64; ++b) {
        /* b=2 tests 3,4,5; b=3 tests 7,8,9; ... */
        uint64_t num = 1ULL << b;
        test_assert_idx(bits_required64(num-1) == b,   b);
        test_assert_idx(bits_required64(num  ) == b+1, b);
        test_assert_idx(bits_required64(num+1) == b+1, b);
    }
    test_end();
}

static void test_sum_overflows(void)
{
#define MAX64 (uint64_t)-1
    static const struct {
        uint64_t a, b;
        bool overflows;
    } tests[] = {
        { MAX64-1, 1, FALSE },
        { MAX64, 1, TRUE },
        { MAX64-1, 1, FALSE },
        { MAX64-1, 2, TRUE },
        { MAX64-1, MAX64-1, TRUE },
        { MAX64-1, MAX64, TRUE },
        { MAX64, MAX64, TRUE }
    };
    unsigned int i;

    test_begin("UINT64_SUM_OVERFLOWS");
    for (i = 0; i < N_ELEMENTS(tests); i++)
        test_assert(UINT64_SUM_OVERFLOWS(tests[i].a, tests[i].b) == tests[i].overflows);
    test_end();
}

void test_bits()
{
    test_nearest_power();
    test_bits_requiredXX();
    test_sum_overflows();
}