diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/shared/macro.h | 13 | ||||
| -rw-r--r-- | src/test/test-util.c | 31 |
2 files changed, 44 insertions, 0 deletions
diff --git a/src/shared/macro.h b/src/shared/macro.h index d53b07fea5..53bd578d7e 100644 --- a/src/shared/macro.h +++ b/src/shared/macro.h @@ -100,6 +100,19 @@ static inline size_t ALIGN_TO(size_t l, size_t ali) { #define ALIGN_TO_PTR(p, ali) ((void*) ALIGN_TO((unsigned long) p, ali)) +/* align to next higher power-of-2 (except for: 0 => 0, overflow => 0) */ +static inline unsigned long ALIGN_POWER2(unsigned long u) { + /* clz(0) is undefined */ + if (u == 1) + return 1; + + /* left-shift overflow is undefined */ + if (__builtin_clzl(u - 1UL) < 1) + return 0; + + return 1UL << (sizeof(u) * 8 - __builtin_clzl(u - 1UL)); +} + #define ELEMENTSOF(x) (sizeof(x)/sizeof((x)[0])) /* diff --git a/src/test/test-util.c b/src/test/test-util.c index 93929cd9fc..caf8d2b12b 100644 --- a/src/test/test-util.c +++ b/src/test/test-util.c @@ -37,6 +37,36 @@ static void test_streq_ptr(void) { assert_se(!streq_ptr("abc", "cdef")); } +static void test_align_power2(void) { + unsigned long i, p2; + + assert_se(ALIGN_POWER2(0) == 0); + assert_se(ALIGN_POWER2(1) == 1); + assert_se(ALIGN_POWER2(2) == 2); + assert_se(ALIGN_POWER2(3) == 4); + assert_se(ALIGN_POWER2(12) == 16); + + assert_se(ALIGN_POWER2(ULONG_MAX) == 0); + assert_se(ALIGN_POWER2(ULONG_MAX - 1) == 0); + assert_se(ALIGN_POWER2(ULONG_MAX - 1024) == 0); + assert_se(ALIGN_POWER2(ULONG_MAX / 2) == ULONG_MAX / 2 + 1); + assert_se(ALIGN_POWER2(ULONG_MAX + 1) == 0); + + for (i = 1; i < 131071; ++i) { + for (p2 = 1; p2 < i; p2 <<= 1) + /* empty */ ; + + assert_se(ALIGN_POWER2(i) == p2); + } + + for (i = ULONG_MAX - 1024; i < ULONG_MAX; ++i) { + for (p2 = 1; p2 && p2 < i; p2 <<= 1) + /* empty */ ; + + assert_se(ALIGN_POWER2(i) == p2); + } +} + static void test_first_word(void) { assert_se(first_word("Hello", "")); assert_se(first_word("Hello", "Hello")); @@ -680,6 +710,7 @@ int main(int argc, char *argv[]) { log_open(); test_streq_ptr(); + test_align_power2(); test_first_word(); test_close_many(); test_parse_boolean(); |