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AK+LibC+Kernel: Move the implementation of memmem to AK

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AnotherTest 2020-08-21 03:47:15 +04:30 • committed by Andreas Kling
parent 779b643855
commit 67f7f6840d
3 changed files with 91 additions and 98 deletions
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51
Libraries/LibC/string.cpp
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@ -24,6 +24,7 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/MemMem.h>
#include <AK/Platform.h>
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
@ -189,57 +190,9 @@ void* memmove(void* dest, const void* src, size_t n)
return dest;
}
namespace {
const static void* bitap_bitwise(const void* haystack, size_t haystack_length, const void* needle, size_t needle_length)
{
ASSERT(needle_length < 32);
u64 lookup = 0xfffffffe;
constexpr size_t mask_length = (size_t)((u8)-1) + 1;
u64 needle_mask[mask_length];
for (size_t i = 0; i < mask_length; ++i)
needle_mask[i] = 0xffffffff;
for (size_t i = 0; i < needle_length; ++i)
needle_mask[((const u8*)needle)[i]] &= ~(0x00000001 << i);
for (size_t i = 0; i < haystack_length; ++i) {
lookup |= needle_mask[((const u8*)haystack)[i]];
lookup <<= 1;
if (!(lookup & (0x00000001 << needle_length)))
return ((const u8*)haystack) + i - needle_length + 1;
}
return nullptr;
}
}
const void* memmem(const void* haystack, size_t haystack_length, const void* needle, size_t needle_length)
{
if (needle_length == 0)
return haystack;
if (haystack_length < needle_length)
return nullptr;
if (haystack_length == needle_length)
return memcmp(haystack, needle, haystack_length) == 0 ? haystack : nullptr;
if (needle_length < 32)
return bitap_bitwise(haystack, haystack_length, needle, needle_length);
// Fallback to a slower search.
auto length_diff = haystack_length - needle_length;
for (size_t i = 0; i < length_diff; ++i) {
const auto* start = ((const u8*)haystack) + i;
if (memcmp(start, needle, needle_length) == 0)
return start;
}
return nullptr;
return AK::memmem(haystack, haystack_length, needle, needle_length);
}
char* strcpy(char* dest, const char* src)