string-case.cc | Explore in Territory

// Copyright 2016 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.

#include "src/strings/string-case.h"

#include "src/base/logging.h"
#include "src/common/assert-scope.h"
#include "src/common/globals.h"
#include "src/utils/utils.h"

namespace v8 {
namespace internal {

// FastAsciiConvert tries to do character processing on a word_t basis if
// source and destination strings are properly aligned. Natural alignment of
// string data depends on kTaggedSize so we define word_t via Tagged_t.
using word_t = std::make_unsigned<Tagged_t>::type;

const word_t kWordTAllBitsSet = std::numeric_limits<word_t>::max();
const word_t kOneInEveryByte = kWordTAllBitsSet / 0xFF;
const word_t kAsciiMask = kOneInEveryByte << 7;

#ifdef DEBUG
bool CheckFastAsciiConvert(char* dst, const char* src, int length, bool changed,
                           bool is_to_lower) { … }
#endif

// Given a word and two range boundaries returns a word with high bit
// set in every byte iff the corresponding input byte was strictly in
// the range (m, n). All the other bits in the result are cleared.
// This function is only useful when it can be inlined and the
// boundaries are statically known.
// Requires: all bytes in the input word and the boundaries must be
// ASCII (less than 0x7F).
static inline word_t AsciiRangeMask(word_t w, char m, char n) { … }

template <bool is_lower>
int FastAsciiConvert(char* dst, const char* src, int length,
                     bool* changed_out) { … }

template int FastAsciiConvert<false>(char* dst, const char* src, int length,
                                     bool* changed_out);
template int FastAsciiConvert<true>(char* dst, const char* src, int length,
                                    bool* changed_out);

}  // namespace internal
}  // namespace v8
chromium/v8/src/strings/string-case.cc
