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// Copyright 2016 The Draco Authors.
//
// 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.
//
#include "draco/core/hash_utils.h"
#include <cstddef>
#include <functional>
#include <limits>
namespace draco {
// Will never return 1 or 0.
uint64_t FingerprintString(const char *s, size_t len) {
const uint64_t seed = 0x87654321;
const int hash_loop_count = static_cast<int>(len / 8) + 1;
uint64_t hash = seed;
for (int i = 0; i < hash_loop_count; ++i) {
const int off = i * 8;
const int num_chars_left = static_cast<int>(len) - off;
uint64_t new_hash = seed;
if (num_chars_left > 7) {
const int off2 = i * 8;
new_hash = static_cast<uint64_t>(s[off2]) << 56 |
static_cast<uint64_t>(s[off2 + 1]) << 48 |
static_cast<uint64_t>(s[off2 + 2]) << 40 |
static_cast<uint64_t>(s[off2 + 3]) << 32 |
static_cast<uint64_t>(s[off2 + 4]) << 24 |
static_cast<uint64_t>(s[off2 + 5]) << 16 |
static_cast<uint64_t>(s[off2 + 6]) << 8 | s[off2 + 7];
} else {
for (int j = 0; j < num_chars_left; ++j) {
new_hash |= static_cast<uint64_t>(s[off + j])
<< (64 - ((num_chars_left - j) * 8));
}
}
hash = HashCombine(new_hash, hash);
}
if (hash < std::numeric_limits<uint64_t>::max() - 1) {
hash += 2;
}
return hash;
}
} // namespace draco
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