new file mode 100644
@@ -0,0 +1,106 @@
+/* CMurmurHash2A, by Austin Appleby with minor changes for gcc.
+ This is a variant of MurmurHash2 modified to use the Merkle-Damgard
+ construction. Bulk speed should be identical to Murmur2, small-key speed
+ will be 10%-20% slower due to the added overhead at the end of the hash.
+ This is a sample implementation of MurmurHash2A designed to work
+ incrementally.
+
+ Only uses 4 bytes, no special 64bit implementation.
+ However gcc is typically more bound by hash misses on collisions than
+ the speed of the hash function itself. */
+
+#define mmix(h,k) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
+
+class cmurmurhash2A
+{
+ public:
+
+ void begin(uint32_t seed = 0)
+ {
+ m_hash = seed;
+ m_tail = 0;
+ m_count = 0;
+ m_size = 0;
+ }
+
+ /* Note the caller must pass in 4 byte aligned values */
+ void add(const unsigned char * data, int len)
+ {
+ m_size += len;
+
+ mix_tail (data,len);
+
+ while(len >= 4)
+ {
+ uint32_t k = *(const uint32_t *)data;
+
+ mmix (m_hash, k);
+
+ data += 4;
+ len -= 4;
+ }
+
+ mix_tail (data,len);
+ }
+
+ void add_int(uint32_t i)
+ {
+ add ((const unsigned char *)&i, 4);
+ }
+
+ void add_ptr(void *p)
+ {
+ add ((const unsigned char *)&p, sizeof (void *));
+ }
+
+ void merge(cmurmurhash2A &s)
+ {
+ // better way?
+ add_int (s.end());
+ }
+
+ /* Does not destroy state. */
+ uint32_t end(void)
+ {
+ uint32_t t_hash = m_hash;
+ uint32_t t_tail = m_tail;
+ uint32_t t_size = m_size;
+
+ mmix (t_hash, t_tail);
+ mmix (t_hash, t_size);
+
+ t_hash ^= t_hash >> 13;
+ t_hash *= m;
+ t_hash ^= t_hash >> 15;
+
+ return t_hash;
+ }
+
+ private:
+
+ static const uint32_t m = 0x5bd1e995;
+ static const int r = 24;
+
+ void mix_tail (const unsigned char * & data, int & len)
+ {
+ while (len && ((len<4) || m_count))
+ {
+ m_tail |= (*data++) << (m_count * 8);
+
+ m_count++;
+ len--;
+
+ if(m_count == 4)
+ {
+ mmix (m_hash, m_tail);
+ m_tail = 0;
+ m_count = 0;
+ }
+ }
+ }
+
+ uint32_t m_hash;
+ uint32_t m_tail;
+ uint32_t m_count;
+ uint32_t m_size;
+};
From: Andi Kleen <ak@linux.intel.com> Used in the next patch. I use Austin Appleby's Public Domain Murmur2A reference code. I don't own that code. Murmur hash is available from http://code.google.com/p/smhasher/wiki/MurmurHash gcc/: 2013-04-18 Andi Kleen <ak@linux.intel.com> * murmurhash.h: New file --- gcc/murmurhash.h | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 106 insertions(+) create mode 100644 gcc/murmurhash.h