Squashed 'src/leveldb/' content from commit aca1ffc

git-subtree-dir: src/leveldb
git-subtree-split: aca1ffc4b65be5e099b2088c6e6a308d69e1ad73

util/hash.cc

@@ -0,0 +1,45 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <string.h>
+#include "util/coding.h"
+#include "util/hash.h"
+
+namespace leveldb {
+
+uint32_t Hash(const char* data, size_t n, uint32_t seed) {
+  // Similar to murmur hash
+  const uint32_t m = 0xc6a4a793;
+  const uint32_t r = 24;
+  const char* limit = data + n;
+  uint32_t h = seed ^ (n * m);
+
+  // Pick up four bytes at a time
+  while (data + 4 <= limit) {
+    uint32_t w = DecodeFixed32(data);
+    data += 4;
+    h += w;
+    h *= m;
+    h ^= (h >> 16);
+  }
+
+  // Pick up remaining bytes
+  switch (limit - data) {
+    case 3:
+      h += data[2] << 16;
+      // fall through
+    case 2:
+      h += data[1] << 8;
+      // fall through
+    case 1:
+      h += data[0];
+      h *= m;
+      h ^= (h >> r);
+      break;
+  }
+  return h;
+}
+
+
+}  // namespace leveldb