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basic/util: add macro variants of log2 functions

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The macro variants can be used in static initializers.

The same guard against calling __builtin_clz(0) is added as for
__builtin_clzll(0), since that's undefined behaviour too. Our code
wouldn't call it, but this avoids a potential pitfall with the macro.
All variants map 0→0. Otherwise we'd often have to handle 0 specially
in callers.

__builtin_clz takes unsigned as the argument, so there's no LOG2I macro.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2021-11-29 11:12:52 +01:00
parent 58c34be864
commit f4ada1b42f
2 changed files with 81 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/test/test-util.c
+58 -11
View File
@@ -17,8 +17,42 @@
#include "tests.h"
#include "util.h"
TEST(LOG2ULL) {
assert_se(LOG2ULL(0) == 0);
assert_se(LOG2ULL(1) == 0);
assert_se(LOG2ULL(8) == 3);
assert_se(LOG2ULL(9) == 3);
assert_se(LOG2ULL(15) == 3);
assert_se(LOG2ULL(16) == 4);
assert_se(LOG2ULL(1024*1024) == 20);
assert_se(LOG2ULL(1024*1024+5) == 20);
}
TEST(CONST_LOG2ULL) {
assert_se(CONST_LOG2ULL(0) == 0);
assert_se(CONST_LOG2ULL(1) == 0);
assert_se(CONST_LOG2ULL(8) == 3);
assert_se(CONST_LOG2ULL(9) == 3);
assert_se(CONST_LOG2ULL(15) == 3);
assert_se(CONST_LOG2ULL(16) == 4);
assert_se(CONST_LOG2ULL(1024*1024) == 20);
assert_se(CONST_LOG2ULL(1024*1024+5) == 20);
}
TEST(NONCONST_LOG2ULL) {
assert_se(NONCONST_LOG2ULL(0) == 0);
assert_se(NONCONST_LOG2ULL(1) == 0);
assert_se(NONCONST_LOG2ULL(8) == 3);
assert_se(NONCONST_LOG2ULL(9) == 3);
assert_se(NONCONST_LOG2ULL(15) == 3);
assert_se(NONCONST_LOG2ULL(16) == 4);
assert_se(NONCONST_LOG2ULL(1024*1024) == 20);
assert_se(NONCONST_LOG2ULL(1024*1024+5) == 20);
}
TEST(log2u64) {
assert_se(log2u64(0) == 0);
assert_se(log2u64(1) == 0);
assert_se(log2u64(8) == 3);
assert_se(log2u64(9) == 3);
assert_se(log2u64(15) == 3);
@@ -27,6 +61,30 @@ TEST(log2u64) {
assert_se(log2u64(1024*1024+5) == 20);
}
TEST(log2u) {
assert_se(log2u(0) == 0);
assert_se(log2u(1) == 0);
assert_se(log2u(2) == 1);
assert_se(log2u(3) == 1);
assert_se(log2u(4) == 2);
assert_se(log2u(32) == 5);
assert_se(log2u(33) == 5);
assert_se(log2u(63) == 5);
assert_se(log2u(INT_MAX) == sizeof(int)*8-2);
}
TEST(log2i) {
assert_se(log2i(0) == 0);
assert_se(log2i(1) == 0);
assert_se(log2i(2) == 1);
assert_se(log2i(3) == 1);
assert_se(log2i(4) == 2);
assert_se(log2i(32) == 5);
assert_se(log2i(33) == 5);
assert_se(log2i(63) == 5);
assert_se(log2i(INT_MAX) == sizeof(int)*8-2);
}
TEST(protect_errno) {
errno = 12;
{
@@ -58,17 +116,6 @@ TEST(unprotect_errno) {
assert_se(errno == 4711);
}
TEST(log2i) {
assert_se(log2i(1) == 0);
assert_se(log2i(2) == 1);
assert_se(log2i(3) == 1);
assert_se(log2i(4) == 2);
assert_se(log2i(32) == 5);
assert_se(log2i(33) == 5);
assert_se(log2i(63) == 5);
assert_se(log2i(INT_MAX) == sizeof(int)*8-2);
}
TEST(eqzero) {
const uint32_t zeros[] = {0, 0, 0};
const uint32_t ones[] = {1, 1};