[Glacier] Move hashmap to a real hash implementation.

lib/glacier/util/hash.cpp

@@ -0,0 +1,30 @@
+#include "util/hash.h"
+
+#include "string/string.h"
+
+namespace glcr {
+namespace {
+
+const uint64_t kFnvOffset = 0xcbf29ce484222325;
+const uint64_t kFnvPrime = 0x100000001b3;
+
+}  // namespace
+
+uint64_t Hash<uint64_t>::operator()(const uint64_t& value) {
+  uint64_t hash = kFnvOffset;
+  for (uint8_t i = 0; i < 8; i++) {
+    hash *= kFnvPrime;
+    hash ^= (value >> (8 * i)) & 0xFF;
+  }
+  return hash;
+}
+uint64_t Hash<String>::operator()(const String& value) {
+  uint64_t hash = kFnvOffset;
+  for (uint8_t i = 0; i < value.length(); i++) {
+    hash *= kFnvPrime;
+    hash ^= value[i];
+  }
+  return hash;
+}
+
+}  // namespace glcr

lib/glacier/util/hash.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <stdint.h>
+
+namespace glcr {
+
+// General purpose templated hash function.
+// Currently the template speciializations
+// implement FNV hashing:
+// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
+template <typename T>
+struct Hash {
+  uint64_t operator()(const T&);
+};
+
+template <>
+struct Hash<uint64_t> {
+  uint64_t operator()(const uint64_t&);
+};
+
+class String;
+template <>
+struct Hash<String> {
+  uint64_t operator()(const String&);
+};
+
+}  // namespace glcr