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// Copyright 2011 Google Inc. All Rights Reserved.
//
// 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 NINJA_MAP_H_
#define NINJA_MAP_H_
#include <algorithm>
#include <string.h>
#include "string_piece.h"
#include "util.h"
// MurmurHash2, by Austin Appleby
static inline
unsigned int MurmurHash2(const void* key, size_t len) {
static const unsigned int seed = 0xDECAFBAD;
const unsigned int m = 0x5bd1e995;
const int r = 24;
unsigned int h = seed ^ len;
const unsigned char* data = (const unsigned char*)key;
while (len >= 4) {
unsigned int k;
memcpy(&k, data, sizeof k);
k *= m;
k ^= k >> r;
k *= m;
h *= m;
h ^= k;
data += 4;
len -= 4;
}
switch (len) {
case 3: h ^= data[2] << 16;
NINJA_FALLTHROUGH;
case 2: h ^= data[1] << 8;
NINJA_FALLTHROUGH;
case 1: h ^= data[0];
h *= m;
};
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
#include <unordered_map>
namespace std {
template<>
struct hash<StringPiece> {
typedef StringPiece argument_type;
typedef size_t result_type;
size_t operator()(StringPiece key) const {
return MurmurHash2(key.str_, key.len_);
}
};
}
/// A template for hash_maps keyed by a StringPiece whose string is
/// owned externally (typically by the values). Use like:
/// ExternalStringHash<Foo*>::Type foos; to make foos into a hash
/// mapping StringPiece => Foo*.
template<typename V>
struct ExternalStringHashMap {
typedef std::unordered_map<StringPiece, V> Type;
};
#endif // NINJA_MAP_H_
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