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+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LIBTEXTCLASSIFIER_UTILS_HASH_FARMHASH_H_
+#define LIBTEXTCLASSIFIER_UTILS_HASH_FARMHASH_H_
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>   // for memcpy and memset
+#include <utility>
+
+#ifndef NAMESPACE_FOR_HASH_FUNCTIONS
+#define NAMESPACE_FOR_HASH_FUNCTIONS tc3farmhash
+#endif
+
+namespace NAMESPACE_FOR_HASH_FUNCTIONS {
+
+#if defined(FARMHASH_UINT128_T_DEFINED)
+inline uint64_t Uint128Low64(const uint128_t x) {
+  return static_cast<uint64_t>(x);
+}
+inline uint64_t Uint128High64(const uint128_t x) {
+  return static_cast<uint64_t>(x >> 64);
+}
+inline uint128_t Uint128(uint64_t lo, uint64_t hi) {
+  return lo + (((uint128_t)hi) << 64);
+}
+#else
+typedef std::pair<uint64_t, uint64_t> uint128_t;
+inline uint64_t Uint128Low64(const uint128_t x) { return x.first; }
+inline uint64_t Uint128High64(const uint128_t x) { return x.second; }
+inline uint128_t Uint128(uint64_t lo, uint64_t hi) { return uint128_t(lo, hi); }
+#endif
+
+
+// BASIC STRING HASHING
+
+// Hash function for a byte array.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+size_t Hash(const char* s, size_t len);
+
+// Hash function for a byte array.  Most useful in 32-bit binaries.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+uint32_t Hash32(const char* s, size_t len);
+
+// Hash function for a byte array.  For convenience, a 32-bit seed is also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+uint32_t Hash32WithSeed(const char* s, size_t len, uint32_t seed);
+
+// Hash 128 input bits down to 64 bits of output.
+// Hash function for a byte array.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+uint64_t Hash64(const char* s, size_t len);
+
+// Hash function for a byte array.  For convenience, a 64-bit seed is also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+uint64_t Hash64WithSeed(const char* s, size_t len, uint64_t seed);
+
+// Hash function for a byte array.  For convenience, two seeds are also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+uint64_t Hash64WithSeeds(const char* s, size_t len,
+                       uint64_t seed0, uint64_t seed1);
+
+// Hash function for a byte array.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+uint128_t Hash128(const char* s, size_t len);
+
+// Hash function for a byte array.  For convenience, a 128-bit seed is also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+uint128_t Hash128WithSeed(const char* s, size_t len, uint128_t seed);
+
+// BASIC NON-STRING HASHING
+
+// This is intended to be a reasonably good hash function.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+inline uint64_t Hash128to64(uint128_t x) {
+  // Murmur-inspired hashing.
+  const uint64_t kMul = 0x9ddfea08eb382d69ULL;
+  uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
+  a ^= (a >> 47);
+  uint64_t b = (Uint128High64(x) ^ a) * kMul;
+  b ^= (b >> 47);
+  b *= kMul;
+  return b;
+}
+
+// FINGERPRINTING (i.e., good, portable, forever-fixed hash functions)
+
+// Fingerprint function for a byte array.  Most useful in 32-bit binaries.
+uint32_t Fingerprint32(const char* s, size_t len);
+
+// Fingerprint function for a byte array.
+uint64_t Fingerprint64(const char* s, size_t len);
+
+// Fingerprint function for a byte array.
+uint128_t Fingerprint128(const char* s, size_t len);
+
+// This is intended to be a good fingerprinting primitive.
+// See below for more overloads.
+inline uint64_t Fingerprint(uint128_t x) {
+  // Murmur-inspired hashing.
+  const uint64_t kMul = 0x9ddfea08eb382d69ULL;
+  uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
+  a ^= (a >> 47);
+  uint64_t b = (Uint128High64(x) ^ a) * kMul;
+  b ^= (b >> 44);
+  b *= kMul;
+  b ^= (b >> 41);
+  b *= kMul;
+  return b;
+}
+
+// This is intended to be a good fingerprinting primitive.
+inline uint64_t Fingerprint(uint64_t x) {
+  // Murmur-inspired hashing.
+  const uint64_t kMul = 0x9ddfea08eb382d69ULL;
+  uint64_t b = x * kMul;
+  b ^= (b >> 44);
+  b *= kMul;
+  b ^= (b >> 41);
+  b *= kMul;
+  return b;
+}
+
+#ifndef FARMHASH_NO_CXX_STRING
+
+// Convenience functions to hash or fingerprint C++ strings.
+// These require that Str::data() return a pointer to the first char
+// (as a const char*) and that Str::length() return the string's length;
+// they work with std::string, for example.
+
+// Hash function for a byte array.  Most useful in 32-bit binaries.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline size_t Hash(const Str& s) {
+  assert(sizeof(s[0]) == 1);
+  return Hash(s.data(), s.length());
+}
+
+// Hash function for a byte array.  Most useful in 32-bit binaries.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline uint32_t Hash32(const Str& s) {
+  assert(sizeof(s[0]) == 1);
+  return Hash32(s.data(), s.length());
+}
+
+// Hash function for a byte array.  For convenience, a 32-bit seed is also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline uint32_t Hash32WithSeed(const Str& s, uint32_t seed) {
+  assert(sizeof(s[0]) == 1);
+  return Hash32WithSeed(s.data(), s.length(), seed);
+}
+
+// Hash 128 input bits down to 64 bits of output.
+// Hash function for a byte array.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline uint64_t Hash64(const Str& s) {
+  assert(sizeof(s[0]) == 1);
+  return Hash64(s.data(), s.length());
+}
+
+// Hash function for a byte array.  For convenience, a 64-bit seed is also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline uint64_t Hash64WithSeed(const Str& s, uint64_t seed) {
+  assert(sizeof(s[0]) == 1);
+  return Hash64WithSeed(s.data(), s.length(), seed);
+}
+
+// Hash function for a byte array.  For convenience, two seeds are also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline uint64_t Hash64WithSeeds(const Str& s, uint64_t seed0, uint64_t seed1) {
+  assert(sizeof(s[0]) == 1);
+  return Hash64WithSeeds(s.data(), s.length(), seed0, seed1);
+}
+
+// Hash function for a byte array.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline uint128_t Hash128(const Str& s) {
+  assert(sizeof(s[0]) == 1);
+  return Hash128(s.data(), s.length());
+}
+
+// Hash function for a byte array.  For convenience, a 128-bit seed is also
+// hashed into the result.
+// May change from time to time, may differ on different platforms, may differ
+// depending on NDEBUG.
+template <typename Str>
+inline uint128_t Hash128WithSeed(const Str& s, uint128_t seed) {
+  assert(sizeof(s[0]) == 1);
+  return Hash128(s.data(), s.length(), seed);
+}
+
+// FINGERPRINTING (i.e., good, portable, forever-fixed hash functions)
+
+// Fingerprint function for a byte array.  Most useful in 32-bit binaries.
+template <typename Str>
+inline uint32_t Fingerprint32(const Str& s) {
+  assert(sizeof(s[0]) == 1);
+  return Fingerprint32(s.data(), s.length());
+}
+
+// Fingerprint 128 input bits down to 64 bits of output.
+// Fingerprint function for a byte array.
+template <typename Str>
+inline uint64_t Fingerprint64(const Str& s) {
+  assert(sizeof(s[0]) == 1);
+  return Fingerprint64(s.data(), s.length());
+}
+
+// Fingerprint function for a byte array.
+template <typename Str>
+inline uint128_t Fingerprint128(const Str& s) {
+  assert(sizeof(s[0]) == 1);
+  return Fingerprint128(s.data(), s.length());
+}
+
+#endif
+
+}  // namespace NAMESPACE_FOR_HASH_FUNCTIONS
+
+#endif  // LIBTEXTCLASSIFIER_UTILS_HASH_FARMHASH_H_