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diff --git a/external/hash/cmetrohash.h b/external/hash/cmetrohash.h
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+// metrohash.h
+//
+// The MIT License (MIT)
+//
+// Copyright (c) 2015 J. Andrew Rogers
+//
+// Updated Nov. 2015 to use safe unaligned reads and platform neutral
+// hash. This WILL change hashes on big endian platfors. / mikkelfj
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+
+#ifndef CMETROHASH_METROHASH_H
+#define CMETROHASH_METROHASH_H
+
+#include "ht_portable.h"
+#include "unaligned.h"
+
+#pragma once
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include <string.h>
+
+// MetroHash 64-bit hash functions
+void cmetrohash64_1(const uint8_t * key, uint64_t len, uint32_t seed, uint8_t * out);
+void cmetrohash64_2(const uint8_t * key, uint64_t len, uint32_t seed, uint8_t * out);
+
+
+/* rotate right idiom recognized by compiler*/
+inline static uint64_t crotate_right(uint64_t v, unsigned k)
+{
+    return (v >> k) | (v << (64 - k));
+}
+
+inline static uint64_t cread_u64(const void * const ptr)
+{
+    return (uint64_t)unaligned_read_le64toh(ptr);
+}
+
+inline static uint64_t cread_u32(const void * const ptr)
+{
+    return (uint64_t)unaligned_read_le32toh(ptr);
+}
+
+inline static uint64_t cread_u16(const void * const ptr)
+{
+    return (uint64_t)unaligned_read_le16toh(ptr);
+}
+
+inline static uint64_t cread_u8 (const void * const ptr)
+{
+    return * (uint8_t *) ptr;
+}
+
+#if defined (__cplusplus)
+}
+#endif
+#endif // #ifndef CMETROHASH_METROHASH_H