third_party/WebKit/Source/platform/wtf/text/AtomicStringTable.cpp

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "platform/wtf/text/AtomicStringTable.h"

#include "platform/wtf/text/StringHash.h"
#include "platform/wtf/text/UTF8.h"

namespace WTF {

using namespace Unicode;

AtomicStringTable::AtomicStringTable() {
  for (StringImpl* string : StringImpl::AllStaticStrings().Values())
    Add(string);
}

AtomicStringTable::~AtomicStringTable() {
  for (StringImpl* string : table_) {
    if (!string->IsStatic()) {
      DCHECK(string->IsAtomic());
      string->SetIsAtomic(false);
    }
  }
}

void AtomicStringTable::ReserveCapacity(unsigned size) {
  table_.ReserveCapacityForSize(size);
}

template <typename T, typename HashTranslator>
scoped_refptr<StringImpl> AtomicStringTable::AddToStringTable(const T& value) {
  HashSet<StringImpl*>::AddResult add_result =
      table_.AddWithTranslator<HashTranslator>(value);

  // If the string is newly-translated, then we need to adopt it.
  // The boolean in the pair tells us if that is so.
  return add_result.is_new_entry ? base::AdoptRef(*add_result.stored_value)
                                 : *add_result.stored_value;
}

template <typename CharacterType>
struct HashTranslatorCharBuffer {
  const CharacterType* s;
  unsigned length;
};

typedef HashTranslatorCharBuffer<UChar> UCharBuffer;
struct UCharBufferTranslator {
  static unsigned GetHash(const UCharBuffer& buf) {
    return StringHasher::ComputeHashAndMaskTop8Bits(buf.s, buf.length);
  }

  static bool Equal(StringImpl* const& str, const UCharBuffer& buf) {
    return WTF::Equal(str, buf.s, buf.length);
  }

  static void Translate(StringImpl*& location,
                        const UCharBuffer& buf,
                        unsigned hash) {
    auto string = StringImpl::Create8BitIfPossible(buf.s, buf.length);
    if (string)
      string->AddRef();
    location = string.get();
    location->SetHash(hash);
    location->SetIsAtomic(true);
  }
};

struct HashAndUTF8Characters {
  unsigned hash;
  const char* characters;
  unsigned length;
  unsigned utf16_length;
};

struct HashAndUTF8CharactersTranslator {
  static unsigned GetHash(const HashAndUTF8Characters& buffer) {
    return buffer.hash;
  }

  static bool Equal(StringImpl* const& string,
                    const HashAndUTF8Characters& buffer) {
    if (buffer.utf16_length != string->length())
      return false;

    // If buffer contains only ASCII characters UTF-8 and UTF16 length are the
    // same.
    if (buffer.utf16_length != buffer.length) {
      if (string->Is8Bit()) {
        const LChar* characters8 = string->Characters8();
        return EqualLatin1WithUTF8(characters8, characters8 + string->length(),
                                   buffer.characters,
                                   buffer.characters + buffer.length);
      }
      const UChar* characters16 = string->Characters16();
      return EqualUTF16WithUTF8(characters16, characters16 + string->length(),
                                buffer.characters,
                                buffer.characters + buffer.length);
    }

    if (string->Is8Bit()) {
      const LChar* string_characters = string->Characters8();

      for (unsigned i = 0; i < buffer.length; ++i) {
        DCHECK(IsASCII(buffer.characters[i]));
        if (string_characters[i] != buffer.characters[i])
          return false;
      }

      return true;
    }

    const UChar* string_characters = string->Characters16();

    for (unsigned i = 0; i < buffer.length; ++i) {
      DCHECK(IsASCII(buffer.characters[i]));
      if (string_characters[i] != buffer.characters[i])
        return false;
    }

    return true;
  }

  static void Translate(StringImpl*& location,
                        const HashAndUTF8Characters& buffer,
                        unsigned hash) {
    UChar* target;
    scoped_refptr<StringImpl> new_string =
        StringImpl::CreateUninitialized(buffer.utf16_length, target);

    bool is_all_ascii;
    const char* source = buffer.characters;
    if (ConvertUTF8ToUTF16(&source, source + buffer.length, &target,
                           target + buffer.utf16_length,
                           &is_all_ascii) != kConversionOK)
      NOTREACHED();

    if (is_all_ascii)
      new_string = StringImpl::Create(buffer.characters, buffer.length);

    new_string->AddRef();
    location = new_string.get();
    location->SetHash(hash);
    location->SetIsAtomic(true);
  }
};

scoped_refptr<StringImpl> AtomicStringTable::Add(const UChar* s,
                                                 unsigned length) {
  if (!s)
    return nullptr;

  if (!length)
    return StringImpl::empty_;

  UCharBuffer buffer = {s, length};
  return AddToStringTable<UCharBuffer, UCharBufferTranslator>(buffer);
}

typedef HashTranslatorCharBuffer<LChar> LCharBuffer;
struct LCharBufferTranslator {
  static unsigned GetHash(const LCharBuffer& buf) {
    return StringHasher::ComputeHashAndMaskTop8Bits(buf.s, buf.length);
  }

  static bool Equal(StringImpl* const& str, const LCharBuffer& buf) {
    return WTF::Equal(str, buf.s, buf.length);
  }

  static void Translate(StringImpl*& location,
                        const LCharBuffer& buf,
                        unsigned hash) {
    auto string = StringImpl::Create(buf.s, buf.length);
    string->AddRef();
    location = string.get();
    location->SetHash(hash);
    location->SetIsAtomic(true);
  }
};

scoped_refptr<StringImpl> AtomicStringTable::Add(const LChar* s,
                                                 unsigned length) {
  if (!s)
    return nullptr;

  if (!length)
    return StringImpl::empty_;

  LCharBuffer buffer = {s, length};
  return AddToStringTable<LCharBuffer, LCharBufferTranslator>(buffer);
}

StringImpl* AtomicStringTable::Add(StringImpl* string) {
  if (!string->length())
    return StringImpl::empty_;

  StringImpl* result = *table_.insert(string).stored_value;

  if (!result->IsAtomic())
    result->SetIsAtomic(true);

  DCHECK(!string->IsStatic() || result->IsStatic());
  return result;
}

scoped_refptr<StringImpl> AtomicStringTable::AddUTF8(
    const char* characters_start,
    const char* characters_end) {
  HashAndUTF8Characters buffer;
  buffer.characters = characters_start;
  buffer.hash = CalculateStringHashAndLengthFromUTF8MaskingTop8Bits(
      characters_start, characters_end, buffer.length, buffer.utf16_length);

  if (!buffer.hash)
    return nullptr;

  return AddToStringTable<HashAndUTF8Characters,
                          HashAndUTF8CharactersTranslator>(buffer);
}

void AtomicStringTable::Remove(StringImpl* string) {
  DCHECK(string->IsAtomic());
  auto iterator = table_.find(string);
  CHECK_NE(iterator, table_.end());
  table_.erase(iterator);
}

}  // namespace WTF