* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
-#include "gmqcc.h"
-#include <limits.h>
-
-#if defined(_MSC_VER)
-# define HASH_ROTL32(X, Y) _rotl((X), (Y))
-#elif defined (__GNUC__) && (defined(__i386__) || defined(__amd64__))
- static GMQCC_FORCEINLINE uint32_t hash_rotl32(volatile uint32_t x, int8_t r) {
- __asm__ __volatile__ ("roll %1,%0" : "+r"(x) : "c"(r));
- return x;
+#include <stddef.h>
+size_t hash(const char *string) {
+ size_t hash = 0;
+ for(; *string; ++string) {
+ hash += *string;
+ hash += (hash << 10);
+ hash ^= (hash >> 6);
}
-# define HASH_ROTL32(X, Y) hash_rotl32((volatile uint32_t)(X), (Y))
-#else
-# define HASH_ROTL32(X, Y) (((X) << (Y)) | ((X) >> (32 - (Y))))
-#endif
-
-/*
- * This is a version of the Murmur3 hashing function optimized for various
- * compilers/architectures. It uses the traditional Murmur2 mix staging
- * but fixes the mix staging inner loops.
- *
- * Murmur 2 contains an inner loop such as:
- * while (l >= 4) {
- * u32 k = *(u32*)d;
- * k *= m;
- * k ^= k >> r;
- * k *= m;
- *
- * h *= m;
- * h ^= k;
- * d += 4;
- * l -= 4;
- * }
- *
- * The two u32s that form the key are the same value for x
- * this premix stage will perform the same results for both values. Unrolled
- * this produces just:
- * x *= m;
- * x ^= x >> r;
- * x *= m;
- *
- * h *= m;
- * h ^= x;
- * h *= m;
- * h ^= x;
- *
- * This appears to be fine, except what happens when m == 1? well x
- * cancels out entierly, leaving just:
- * x ^= x >> r;
- * h ^= x;
- * h ^= x;
- *
- * So all keys hash to the same value, but how often does m == 1?
- * well, it turns out testing x for all possible values yeilds only
- * 172,013,942 unique results instead of 2^32. So nearly ~4.6 bits
- * are cancelled out on average!
- *
- * This means we have a 14.5% higher chance of collision. This is where
- * Murmur3 comes in to save the day.
- */
-static GMQCC_FORCEINLINE uint32_t hash_murmur_mix32(uint32_t hash) {
- hash ^= hash >> 16;
- hash *= 0x85EBCA6B;
- hash ^= hash >> 13;
- hash *= 0xC2B2AE35;
- hash ^= hash >> 16;
- return hash;
-}
-
-/*
- * These constants were calculated with SMHasher to determine the best
- * case senario for Murmur3:
- * http://code.google.com/p/smhasher/
- */
-#define HASH_MURMUR_MASK1 0xCC9E2D51
-#define HASH_MURMUR_MASK2 0x1B873593
-#define HASH_MURMUR_SEED 0x9747B28C
-
-#if PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_LITTLE
-# define HASH_MURMUR_SAFEREAD(PTR) (*((uint32_t*)(PTR)))
-#elif PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_BIG
-# if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR >= 3))
-# define HASH_MURMUR_SAFEREAD(PTR) (__builtin_bswap32(*((uint32_t*)(PTR))))
-# endif
-#endif
-/* Process individual bytes at this point since the endianess isn't known. */
-#ifndef HASH_MURMUR_SAFEREAD
-# define HASH_MURMUR_SAFEREAD(PTR) ((PTR)[0] | (PTR)[1] << 8 | (PTR)[2] << 16 | (PTR)[3] << 24)
-#endif
-
-#define HASH_MURMUR_BLOCK(H, K) \
- do { \
- K *= HASH_MURMUR_MASK1; \
- K = HASH_ROTL32(K, 15); \
- K *= HASH_MURMUR_MASK2; \
- H ^= K; \
- H = HASH_ROTL32(H, 13); \
- H = H * 5 + 0xE6546B64; \
- } while (0)
-#define HASH_MURMUR_BYTES(COUNT, H, C, N, PTR, LENGTH) \
- do { \
- int i = COUNT; \
- while (i--) { \
- C = C >> 8 | *PTR++ << 24; \
- N++; \
- LENGTH--; \
- if (N == 4) { \
- HASH_MURMUR_BLOCK(H, C); \
- N = 0; \
- } \
- } \
- } while (0)
-#define HASH_MURMUR_TAIL(P, Z, H, C, N, PTR, LEN) \
- do { \
- LEN -= LEN/4*4; \
- HASH_MURMUR_BYTES(LEN, H, C, N, PTR, LEN); \
- *P = H; \
- *Z = ((C) & ~0xFF) | (N); \
- } while (0)
-
-#if PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_LITTLE
-static GMQCC_FORCEINLINE void hash_murmur_process(uint32_t *ph1, uint32_t *carry, const void *key, int length) {
- uint32_t h1 = *ph1;
- uint32_t c = *carry;
-
- const uint8_t *ptr = (uint8_t*)key;
- const uint8_t *end;
-
- int n = c & 3;
- int it = (4 - n) & 3;
- if (it && it <= length)
- HASH_MURMUR_BYTES(it, h1, c, n, ptr, length);
-
- end = ptr + length/4*4;
- for (; ptr < end; ptr += 4) {
- uint32_t k1 = HASH_MURMUR_SAFEREAD(ptr);
- HASH_MURMUR_BLOCK(h1, k1);
- }
- HASH_MURMUR_TAIL(ph1, carry, h1, c, n, ptr, length);
-}
-#else
-static GMQCC_FORCEINLINE void hash_murmur_process(uint32_t *ph1, uint32_t *carry, const void *key, int length) {
- uint32_t k1;
- uint32_t h1 = *ph1;
- uint32_t c = *carry;
-
- const uint8_t *ptr = (uint8_t*)key;
- const uint8_t *end;
-
- int n = c & 3;
- int it = -(long)ptr & 3;
- if (it && it <= length)
- HASH_MURMUR_BYTES(it, h1, c, n, ptr, length);
-
- end = ptr + length / 4 * 4;
- switch (n) {
- case 0:
- for (; ptr < end; ptr += 4) {
- k1 = HASH_MURMUR_SAFEREAD(ptr);
- HASH_MURMUR_BLOCK(h1, k1);
- }
- break;
-
-# define NEXT(N, RIGHT, LEFT) \
- case N: \
- for (; ptr < end; ptr += 4) { \
- k1 = c >> RIGHT; \
- c = HASH_MURMUR_SAFEREAD(ptr); \
- k1 |= c << LEFT; \
- HASH_MURMUR_BLOCK(h1, k1); \
- } \
- break
- NEXT(1, 24, 8);
- NEXT(2, 16, 16);
- NEXT(3, 8, 24);
- #undef NEXT
- }
- HASH_MURMUR_TAIL(ph1, carry, h1, c, n, ptr, length);
-}
-#endif
-
-static GMQCC_FORCEINLINE uint32_t hash_murmur_result(uint32_t hash, uint32_t carry, size_t length) {
- uint32_t k1;
- int n = carry & 3;
- if (GMQCC_LIKELY(n)) {
- k1 = carry >> (4 - n) * 8;
- k1 *= HASH_MURMUR_MASK1;
- k1 = HASH_ROTL32(k1, 15);
- k1 *= HASH_MURMUR_MASK2;
- hash ^= k1;
- }
- hash ^= length;
- hash = hash_murmur_mix32(hash);
-
+ hash += hash << 3;
+ hash ^= hash >> 11;
+ hash += hash << 15;
return hash;
}
-
-static GMQCC_FORCEINLINE uint32_t hash_murmur(const void *GMQCC_RESTRICT key, size_t length) {
- uint32_t hash = HASH_MURMUR_SEED;
- uint32_t carry = 0;
- hash_murmur_process(&hash, &carry, key, length);
- return hash_murmur_result(hash, carry, length);
-}
-
-/*
- * The following hash function implements it's own strlen to avoid using libc's
- * which isn't always slow but isn't always fastest either.
- *
- * Some things to note about this strlen that are otherwise confusing to grasp
- * at first is that it does intentionally depend on undefined behavior.
- *
- * The first step to the strlen is to ensure alignment before checking words,
- * without this step we risk crossing a page boundry with the word check and
- * that would cause a crash.
- *
- * The second step to the strlen contains intentional undefined behavior. When
- * accessing a word of any size, the first byte of that word is accessible if
- * and only if the whole word is accessible because words are aligned. This is
- * indicated by the fact that size / alignment always divides the page size.
- * One could argue that an architecture exists where size_t and alignment are
- * different, if that were the case, the alignment will always assume to be the
- * size of the type (size_t). So it's always safe in that regard.
- *
- * In other words, an aligned 2^n load cannot cross a page boundry unless
- * n > log2(PAGE_SIZE). There are no known architectures which support such
- * a wide load larger than PAGE_SIZE.
- *
- * Valgrind and address sanatizer may choke on this because they're strictly
- * trying to find bugs, it's a false positive to assume this is a bug when it's
- * intentional. To prevent these false positives, both things need to be taught
- * about the intentional behavior; for address sanatizer this can be done with
- * a compiler attribute, effectively preventing the function from being
- * instrumented. Valgrind requires a little more work as there is no way to
- * downright prevent a function from being instrumented, instead we can mark
- * + sizeof(size_t) bytes ahead of each byte we're reading as we calculate
- * the length of the string, then we can make that additional + sizeof(size_t)
- * on the end undefined after the length has been calculated.
- *
- * If the compiler doesn't have the attribute to disable address sanatizer
- * instrumentation we fall back to using libc's strlen instead. This isn't the
- * best solution. On windows we can assume this method always because neither
- * address sanatizer or valgrind exist.
- */
-
-/* Some compilers expose this */
-#if defined(__has_feature)
-# if __has_feature(address_sanitizer)
-# define ASAN_DISABLE __attribute__((no_sanitize_address))
-# define HAS_ASAN_DISABLE
-# endif
-#endif
-
-/* If they don't try to find by version the attriubte was introduces */
-#if defined(__GNUC__) && __GNUC__ >= 4
-# define ASAN_DISABLE __attribute__((no_sanitize_address))
-# define HAS_ASAN_DISABLE
-#elif defined(__clang__) && __clang_major__ >= 3
-# define ASAN_DISABLE __attribute__((no_sanatize_address))
-# define HAS_ASAN_DISABLE
-/* On windows asan doesn't exist */
-#elif defined(_WIN32)
-# define ASAN_DISABLE /* nothing */
-# define HAS_ASAN_DISABLE
-#endif
-
-#ifndef HAS_ASAN_DISABLE
-# include <string.h>
-#endif
-
-#ifndef NVALGRIND
-# include <valgrind/valgrind.h>
-# include <valgrind/memcheck.h>
-#else
-# define VALGRIND_MAKE_MEM_DEFINED(PTR, REDZONE_SIZE)
-# define VALGRIND_MAKE_MEM_NOACCESS(PTR, REDZONE_SIZE)
-#endif
-
-#ifdef HAS_ASAN_DISABLE
-#define STRLEN_ALIGN (sizeof(size_t))
-#define STRLEN_ONES ((size_t)-1/UCHAR_MAX)
-#define STRLEN_HIGHS (STRLEN_ONES * (UCHAR_MAX/2+1))
-#define STRLEN_HASZERO(X) (((X)-STRLEN_ONES) & ~(X) & STRLEN_HIGHS)
-
-static ASAN_DISABLE size_t hash_strlen(const char *key) {
- const char *s = key;
- const char *a = s;
- const size_t *w;
-
- for (; (uintptr_t)s % STRLEN_ALIGN; s++) {
- if (*s)
- continue;
- return s-a;
- }
-
- VALGRIND_MAKE_MEM_DEFINED(s, STRLEN_ALIGN);
- for (w = (const size_t *)s; !STRLEN_HASZERO(*w); w++) {
- /* Make the next word legal to access */
- VALGRIND_MAKE_MEM_DEFINED(w + STRLEN_ALIGN, STRLEN_ALIGN);
- }
-
- for (s = (const char *)w; *s; s++);
-
- /* It's not legal to access this area anymore */
- VALGRIND_MAKE_MEM_NOACCESS(s + 1, STRLEN_ALIGN);
- return s-a;
-}
-#else
-static GMQCC_INLINE size_t hash_strlen(const char *key) {
- return strlen(key);
-}
-#endif
-
-size_t hash(const char *key) {
- return hash_murmur((const void *)key, hash_strlen(key));
-}
projects / xonotic / gmqcc.git / commitdiff