| // 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_ |