case_folding_hash.h | Explore in Territory

/*
 * Copyright (C) 2006, 2007, 2008, 2012, 2013 Apple Inc. All rights reserved
 * Copyright (C) Research In Motion Limited 2009. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif

#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_TEXT_CASE_FOLDING_HASH_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_TEXT_CASE_FOLDING_HASH_H_

// Case-insensitive hash lookups, using the Unicode case folding algorithm.

#include "third_party/blink/renderer/platform/wtf/text/string_hash.h"
#include "third_party/blink/renderer/platform/wtf/text/unicode.h"

namespace WTF {

// Sends the input data through the Unicode case-folding table.
// Unlike normal PlainHashReader, or the ASCII lower-case lookups,
// we cannot treat 8-bit and 16-bit data separately, as the lookups
// may change strings from one status to the other. For instance,
// µ is in Latin1, but gets case-folded to U+03BC GREEK SMALL LETTER MU,
// and there are examples going the other way as well.
//
// We could perhaps tweak the tables to avoid this, but this is not
// the most performance-sensitive hashing we have around, so we simply
// always treat data as UTF-16, expanding Latin1 as we go. This means
// we also don't bother to try to make tricky SIMD implementations
// for Latin1; we just use the most straightforward code. (Full lookup
// into WTF::unicode::FoldCase is slow enough that it probably dwarfs
// all other performance concerns anyway.)
template <class T>
  requires std::is_same_v<T, LChar> || std::is_same_v<T, UChar>
struct CaseFoldingHashReader { … };

// The GetHash() functions on CaseFoldingHashTraits do not support null strings.
// find(), Contains(), and insert() on
// HashMap<String,..., CaseFoldingHashTraits<String>>
// cause a null-pointer dereference when passed null strings.
class CaseFoldingHash { … };

// T can be String, StringImpl*, scoped_refptr<StringImpl> and AtomicString.
template <typename T>
struct CaseFoldingHashTraits : HashTraits<T>, CaseFoldingHash { … };

}  // namespace WTF

CaseFoldingHash;
CaseFoldingHashTraits;

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_TEXT_CASE_FOLDING_HASH_H_
chromium/third_party/blink/renderer/platform/wtf/text/case_folding_hash.h
