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util: add alloca_align()

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The alloca_align() helper is the alloca() equivalent of posix_memalign().
As there is no such function provided by glibc, we simply account for
additional memory and return a pointer offset into the allocated memory to
grant the alignment.

Furthermore, alloca0_align() is added, which simply clears the allocated
memory.
This commit is contained in:
David Herrmann 2014-09-22 12:05:16 +02:00
parent eee846339d
commit 95d78c7e7c
2 changed files with 30 additions and 0 deletions
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16
src/shared/util.h
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@ -852,6 +852,22 @@ int unlink_noerrno(const char *path);
(void *) memset(_new_, 0, _len_); \
})
#define alloca_align(size, align) \
({ \
void *_ptr_; \
size_t _mask_ = (align) - 1; \
_ptr_ = alloca((size) + _mask_); \
(void*)(((uintptr_t)_ptr_ + _mask_) & ~_mask_); \
})
#define alloca0_align(size, align) \
({ \
void *_new_; \
size_t _size_ = (size); \
_new_ = alloca_align(_size_, (align)); \
(void*)memset(_new_, 0, _size_); \
})
#define strappenda(a, ...) \
({ \
int _len = strlen(a); \

14
src/test/test-util.c
View file

@ -131,6 +131,19 @@ static void test_container_of(void) {
v1) == &myval);
}
static void test_alloca(void) {
static const uint8_t zero[997] = { };
char *t;
t = alloca_align(17, 512);
assert_se(!((uintptr_t)t & 0xff));
memzero(t, 17);
t = alloca0_align(997, 1024);
assert_se(!((uintptr_t)t & 0x1ff));
assert_se(!memcmp(t, zero, 997));
}
static void test_first_word(void) {
assert_se(first_word("Hello", ""));
assert_se(first_word("Hello", "Hello"));
@ -1272,6 +1285,7 @@ int main(int argc, char *argv[]) {
test_align_power2();
test_max();
test_container_of();
test_alloca();
test_first_word();
test_close_many();
test_parse_boolean();