63 lines
2.0 KiB
C++
63 lines
2.0 KiB
C++
// Copyright 2020 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_STRINGS_STRING_UTIL_INTERNAL_H_
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#define BASE_STRINGS_STRING_UTIL_INTERNAL_H_
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#include <type_traits>
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#include "base/ranges/algorithm.h"
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#include "base/strings/string_piece.h"
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namespace base::internal {
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// ASCII-specific tolower. The standard library's tolower is locale sensitive,
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// so we don't want to use it here.
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template <typename CharT,
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typename = std::enable_if_t<std::is_integral<CharT>::value>>
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constexpr CharT ToLowerASCII(CharT c) {
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return (c >= 'A' && c <= 'Z') ? (c + ('a' - 'A')) : c;
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}
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template <typename T>
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constexpr int CompareCaseInsensitiveASCIIT(T a, T b) {
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// Find the first characters that aren't equal and compare them. If the end
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// of one of the strings is found before a nonequal character, the lengths
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// of the strings are compared. Compare using the unsigned type so the sort
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// order is independent of the signedness of `char`.
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static_assert(std::is_integral_v<typename T::value_type>);
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using UCharT = std::make_unsigned_t<typename T::value_type>;
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size_t i = 0;
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while (i < a.length() && i < b.length()) {
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UCharT lower_a = static_cast<UCharT>(ToLowerASCII(a[i]));
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UCharT lower_b = static_cast<UCharT>(ToLowerASCII(b[i]));
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if (lower_a < lower_b)
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return -1;
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if (lower_a > lower_b)
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return 1;
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i++;
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}
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// End of one string hit before finding a different character. Expect the
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// common case to be "strings equal" at this point so check that first.
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if (a.length() == b.length())
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return 0;
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if (a.length() < b.length())
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return -1;
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return 1;
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}
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template <typename CharT, typename CharU>
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inline bool EqualsCaseInsensitiveASCIIT(BasicStringPiece<CharT> a,
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BasicStringPiece<CharU> b) {
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return ranges::equal(a, b, [](auto lhs, auto rhs) {
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return ToLowerASCII(lhs) == ToLowerASCII(rhs);
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});
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}
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} // namespace base::internal
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#endif // BASE_STRINGS_STRING_UTIL_INTERNAL_H_
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