Rename rng.cc to hash.cc

As that's all that's left.

1 files changed, 61 insertions, 0 deletions

diff --git a/crawl-ref/source/hash.cc b/crawl-ref/source/hash.cc
new file mode 100644
index 0000000000..5f38a3416f
--- /dev/null
+++ b/crawl-ref/source/hash.cc
@@ -0,0 +1,61 @@
+/**
+ * @file
+ * @brief Hashes.
+**/
+
+#include "AppHdr.h"
+#include "hash.h"
+
+//-----------------------------------------------------------------------------
+// MurmurHash2, by Austin Appleby
+uint32_t hash32(const void *data, int len)
+{
+    // 'm' and 'r' are mixing constants generated offline.
+    // They're not really 'magic', they just happen to work well.
+    const uint32_t m = 0x5bd1e995;
+
+    // Initialize the hash to a 'random' value
+    uint32_t h = len;
+
+    const uint8_t *d = (const uint8_t*)data;
+    // Mix 4 bytes at a time into the hash
+    while (len >= 4)
+    {
+        uint32_t k = htole32(*(uint32_t *)d);
+
+        k *= m;
+        k ^= k >> 24;
+        k *= m;
+
+        h *= m;
+        h ^= k;
+
+        d += 4;
+        len -= 4;
+    }
+
+    // Handle the last few bytes of the input array
+    switch (len)
+    {
+    case 3: h ^= (uint32_t)d[2] << 16;
+    case 2: h ^= (uint32_t)d[1] << 8;
+    case 1: h ^= (uint32_t)d[0];
+            h *= m;
+    };
+
+    // Do a few final mixes of the hash to ensure the last few
+    // bytes are well-incorporated.
+    h ^= h >> 13;
+    h *= m;
+    h ^= h >> 15;
+
+    return h;
+}
+
+unsigned int hash_rand(int x, uint32_t seed, uint32_t id)
+{
+    if (x < 2)
+        return 0;
+    uint32_t data[2] = {seed, id};
+    return hash32(data, 2 * sizeof(int32_t)) % x;
+}