/*
- * Copyright (C) 2012, 2013
+ * Copyright (C) 2012, 2013, 2014, 2015
* Dale Weiler
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
-#include "gmqcc.h"
-#include <limits.h>
-
-/*
- * This is a version of the Murmur3 hashing function optimized for various
- * compilers/architectures. It uses the traditional Murmur2 mix stagin
- * 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.
- */
-
-/*
- * Some rotation tricks:
- * MSVC one shaves off six instructions, where GCC optimized one for
- * x86 and amd64 shaves off four instructions. Native methods are often
- * optimized rather well at -O3, but not at -O2.
- */
-#if defined(_MSC_VER)
-# define HASH_ROTL32(X, Y) _rotl((X), (Y))
-#else
-static GMQCC_FORCEINLINE uint32_t hash_rotl32(volatile uint32_t x, int8_t r) {
-#if defined (__GNUC__) && (defined(__i386__) || defined(__amd64__))
- __asm__ __volatile__ ("roll %1,%0" : "+r"(x) : "c"(r));
- return x;
-#else /* ! (defined(__GNUC__) && (defined(__i386__) || defined(__amd64__))) */
- return (x << r) | (x >> (32 - r));
-#endif
-}
-# define HASH_ROTL32(X, Y) hash_rotl32((volatile uint32_t)(X), (Y))
-#endif /* !(_MSC_VER) */
-
-static GMQCC_FORCEINLINE uint32_t hash_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_MASK1 0xCC9E2D51
-#define HASH_MASK2 0x1B873593
-#define HASH_SEED 0x9747B28C
-
-#if PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_LITTLE
-# define HASH_NATIVE_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_NATIVE_SAFEREAD(PTR) (__builtin_bswap32(*((uint32_t*)(PTR))))
-# endif
-#endif
-/* Process individual bytes at this point since the endianess isn't known. */
-#ifndef HASH_NATIVE_SAFEREAD
-# define HASH_NATIVE_SAFEREAD(PTR) ((PTR)[0] | (PTR)[1] << 8 | (PTR)[2] << 16 | (PTR)[3] << 24)
-#endif
-
-#define HASH_NATIVE_BLOCK(H, K) \
- do { \
- K *= HASH_MASK1; \
- K = HASH_ROTL32(K, 15); \
- K *= HASH_MASK2; \
- H ^= K; \
- H = HASH_ROTL32(H, 13); \
- H = H * 5 + 0xE6546B64; \
- } while (0)
-
-#define HASH_NATIVE_BYTES(COUNT, H, C, N, PTR, LENGTH) \
- do { \
- int i = COUNT; \
- while (i--) { \
- C = C >> 8 | *PTR++ << 24; \
- N++; \
- LENGTH--; \
- if (N == 4) { \
- HASH_NATIVE_BLOCK(H, C); \
- N = 0; \
- } \
- } \
- } while (0)
-
-/*
- * Highly unrolled at per-carry bit granularity instead of per-block granularity. This will achieve the
- * highest possible instruction level parallelism.
- */
-static GMQCC_FORCEINLINE void hash_native_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;
-
- /* carry count from low 2 bits of carry value */
- int n = c & 3;
-
- /*
- * Unaligned word accesses are safe in LE. Thus we can obtain a little
- * more speed.
- */
-# if PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_LITTLE
- /* Consume carry bits */
- int it = (4 - n) & 3;
- if (it && it <= length)
- HASH_NATIVE_BYTES(it, h1, c, n, ptr, length);
-
- /* word size chunk consumption */
- end = ptr + length/4*4;
- for (; ptr < end; ptr += 4) {
- uint32_t k1 = HASH_NATIVE_SAFEREAD(ptr);
- HASH_NATIVE_BLOCK(h1, k1);
- }
-# else
- /*
- * Unsafe to assume unaligned word accesses. Thus we'll need to consume
- * to alignment then process in aligned block chunks.
- */
- uint32_t k1;
- int it = -(long)ptr & 3;
- if (it && it <= length)
- HASH_NATIVE_BYTES(it, h1, c, n, ptr, length);
-
- /*
- * Alignment has been reached, deal with aligned blocks, specializing for
- * all possible carry counts.
- */
- end = ptr + length / 4 * 4;
- switch (n) {
- case 0:
- for (; ptr < end; ptr += 4) {
- k1 = HASH_NATIVE_SAFEREAD(ptr);
- HASH_NATIVE_BLOCK(h1, k1);
- }
- break;
-
- case 1:
- for (; ptr < end; ptr += 4) {
- k1 = c >> 24;
- c = HASH_NATIVE_SAFEREAD(ptr);
- k1 |= c << 8;
- HASH_NATIVE_BLOCK(h1, k1);
- }
- break;
-
- case 2:
- for (; ptr < end; ptr += 4) {
- k1 = c >> 16;
- c = HASH_NATIVE_SAFEREAD(ptr);
- k1 |= c << 16;
- HASH_NATIVE_BLOCK(h1, k1);
- }
- break;
-
- case 3:
- for (; ptr < end; ptr += 4) {
- k1 = c >> 8;
- c = HASH_NATIVE_SAFEREAD(ptr);
- k1 |= c << 24;
- HASH_NATIVE_BLOCK(h1, k1);
- }
- break;
+#include <stddef.h>
+size_t hash(const char *string) {
+ size_t hash = 0;
+ for(; *string; ++string) {
+ hash += *string;
+ hash += (hash << 10);
+ hash ^= (hash >> 6);
}
-#endif /* misaligned reads */
-
- /*
- * Advanced over 32-bit chunks, this can possibly leave 1..3 bytes of
- * additional trailing content to process.
- */
- length -= length/4*4;
-
- HASH_NATIVE_BYTES(length, h1, c, n, ptr, length);
-
- *ph1 = h1;
- *carry = (c & ~0xFF) | n;
-}
-
-static GMQCC_FORCEINLINE uint32_t hash_native_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_MASK1;
- k1 = HASH_ROTL32(k1, 15);
- k1 *= HASH_MASK2;
- hash ^= k1;
- }
- hash ^= length;
- hash = hash_mix32(hash);
-
+ hash += hash << 3;
+ hash ^= hash >> 11;
+ hash += hash << 15;
return hash;
}
-
-static GMQCC_FORCEINLINE GMQCC_USED uint32_t hash_native(const void *GMQCC_RESTRICT key, size_t length) {
- uint32_t hash = HASH_SEED;
- uint32_t carry = 0;
-
- /* Seperate calls for inliner to deal with */
- hash_native_process(&hash, &carry, key, length);
- return hash_native_result(hash, carry, length);
-}
-
-static uint32_t hash_entry(const void *GMQCC_RESTRICT key, size_t length) {
- return hash_native(key, length);
-}
-
-#define HASH_LEN_ALIGN (sizeof(size_t))
-#define HASH_LEN_ONES ((size_t)-1/UCHAR_MAX)
-#define HASH_LEN_HIGHS (HASH_LEN_ONES * (UCHAR_MAX / 2 + 1))
-#define HASH_LEN_HASZERO(X) (((X)-HASH_LEN_ONES) & ~(X) & HASH_LEN_HIGHS)
-
-size_t hash(const char *key) {
- const char *s = key;
- const char *a = s;
- const size_t *w;
-
- /* Align for fast staging */
- for (; (uintptr_t)s % HASH_LEN_ALIGN; s++) {
- /* Quick stage if terminated before alignment */
- if (!*s)
- return hash_entry(key, s-a);
- }
-
- /*
- * Efficent staging of words for string length calculation, this is
- * faster than ifunc resolver of strlen call.
- *
- * On a x64 this becomes literally two masks, and a quick skip through
- * bytes along the string with the following masks:
- * movabs $0xFEFEFEFEFEFEFEFE,%r8
- * movabs $0x8080808080808080,%rsi
- */
- for (w = (const void *)s; !HASH_LEN_HASZERO(*w); w++);
- for (s = (const void *)w; *s; s++);
-
- return hash_entry(key, s-a);
-}
-
-#undef HASH_LEN_HASZERO
-#undef HASH_LEN_HIGHS
-#undef HASH_LEN_ONES
-#undef HASH_LEN_ALIGN
-#undef HASH_SEED
-#undef HASH_MASK2
-#undef HASH_MASK1
-#undef HASH_ROTL32
-#undef HASH_NATIVE_BLOCK
-#undef HASH_NATIVE_BYTES
-#undef HASH_NATIVE_SAFEREAD
projects / xonotic / gmqcc.git / blobdiff