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shared: add ALIGN_POWER2 macro
Sounds easy, turns out to be horrible to implement: ALIGN_POWER2 returns the next higher power of 2. clz(0) is undefined, same is true for left-shift-overflows, yey, C rocks!
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@ -100,6 +100,19 @@ static inline size_t ALIGN_TO(size_t l, size_t ali) {
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#define ALIGN_TO_PTR(p, ali) ((void*) ALIGN_TO((unsigned long) p, ali))
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/* align to next higher power-of-2 (except for: 0 => 0, overflow => 0) */
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static inline unsigned long ALIGN_POWER2(unsigned long u) {
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/* clz(0) is undefined */
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if (u == 1)
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return 1;
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/* left-shift overflow is undefined */
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if (__builtin_clzl(u - 1UL) < 1)
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return 0;
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return 1UL << (sizeof(u) * 8 - __builtin_clzl(u - 1UL));
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}
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#define ELEMENTSOF(x) (sizeof(x)/sizeof((x)[0]))
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/*
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@ -37,6 +37,36 @@ static void test_streq_ptr(void) {
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assert_se(!streq_ptr("abc", "cdef"));
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}
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static void test_align_power2(void) {
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unsigned long i, p2;
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assert_se(ALIGN_POWER2(0) == 0);
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assert_se(ALIGN_POWER2(1) == 1);
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assert_se(ALIGN_POWER2(2) == 2);
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assert_se(ALIGN_POWER2(3) == 4);
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assert_se(ALIGN_POWER2(12) == 16);
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assert_se(ALIGN_POWER2(ULONG_MAX) == 0);
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assert_se(ALIGN_POWER2(ULONG_MAX - 1) == 0);
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assert_se(ALIGN_POWER2(ULONG_MAX - 1024) == 0);
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assert_se(ALIGN_POWER2(ULONG_MAX / 2) == ULONG_MAX / 2 + 1);
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assert_se(ALIGN_POWER2(ULONG_MAX + 1) == 0);
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for (i = 1; i < 131071; ++i) {
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for (p2 = 1; p2 < i; p2 <<= 1)
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/* empty */ ;
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assert_se(ALIGN_POWER2(i) == p2);
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}
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for (i = ULONG_MAX - 1024; i < ULONG_MAX; ++i) {
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for (p2 = 1; p2 && p2 < i; p2 <<= 1)
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/* empty */ ;
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assert_se(ALIGN_POWER2(i) == p2);
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}
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}
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static void test_first_word(void) {
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assert_se(first_word("Hello", ""));
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assert_se(first_word("Hello", "Hello"));
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@ -680,6 +710,7 @@ int main(int argc, char *argv[]) {
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log_open();
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test_streq_ptr();
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test_align_power2();
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test_first_word();
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test_close_many();
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test_parse_boolean();
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