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// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_STRINGS_STRING_HASHER_INL_H_
#define V8_STRINGS_STRING_HASHER_INL_H_
#include "src/strings/string-hasher.h"
#include "src/objects/objects.h"
#include "src/objects/string-inl.h"
#include "src/strings/char-predicates-inl.h"
#include "src/utils/utils-inl.h"
namespace v8 {
namespace internal {
uint32_t StringHasher::AddCharacterCore(uint32_t running_hash, uint16_t c) {
running_hash += c;
running_hash += (running_hash << 10);
running_hash ^= (running_hash >> 6);
return running_hash;
}
uint32_t StringHasher::GetHashCore(uint32_t running_hash) {
running_hash += (running_hash << 3);
running_hash ^= (running_hash >> 11);
running_hash += (running_hash << 15);
int32_t hash = static_cast<int32_t>(running_hash & String::kHashBitMask);
int32_t mask = (hash - 1) >> 31;
return running_hash | (kZeroHash & mask);
}
uint32_t StringHasher::GetTrivialHash(int length) {
DCHECK_GT(length, String::kMaxHashCalcLength);
// String hash of a large string is simply the length.
return (length << String::kHashShift) | String::kIsNotArrayIndexMask;
}
template <typename schar>
uint32_t StringHasher::HashSequentialString(const schar* chars, int length,
uint64_t seed) {
// Check whether the string is a valid array index. In that case, compute the
// array index hash. It'll fall through to compute a regular string hash from
// the start if it turns out that the string isn't a valid array index.
if (IsInRange(length, 1, String::kMaxArrayIndexSize)) {
if (IsDecimalDigit(chars[0]) && (length == 1 || chars[0] != '0')) {
uint32_t index = chars[0] - '0';
int i = 1;
do {
if (i == length) {
return MakeArrayIndexHash(index, length);
}
} while (TryAddIndexChar(&index, chars[i++]));
}
} else if (length > String::kMaxHashCalcLength) {
return GetTrivialHash(length);
}
// Non-array-index hash.
DCHECK_LE(0, length);
DCHECK_IMPLIES(0 < length, chars != nullptr);
uint32_t running_hash = static_cast<uint32_t>(seed);
const schar* end = &chars[length];
while (chars != end) {
running_hash = AddCharacterCore(running_hash, *chars++);
}
return (GetHashCore(running_hash) << String::kHashShift) |
String::kIsNotArrayIndexMask;
}
std::size_t SeededStringHasher::operator()(const char* name) const {
return StringHasher::HashSequentialString(
name, static_cast<int>(strlen(name)), hashseed_);
}
} // namespace internal
} // namespace v8
#endif // V8_STRINGS_STRING_HASHER_INL_H_
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