71 lines
2.2 KiB
C++
71 lines
2.2 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsASCIIMask_h_
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#define nsASCIIMask_h_
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#include <array>
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#include "mozilla/IndexSequence.h"
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typedef std::array<bool, 128> ASCIIMaskArray;
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namespace mozilla {
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// Boolean arrays, fixed size and filled in at compile time, meant to
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// record something about each of the (standard) ASCII characters.
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// No extended ASCII for now, there has been no use case.
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// If you have loops that go through a string character by character
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// and test for equality to a certain set of characters before deciding
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// on a course of action, chances are building up one of these arrays
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// and using it is going to be faster, especially if the set of
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// characters is more than one long, and known at compile time.
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class ASCIIMask
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{
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public:
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// Preset masks for some common character groups
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// When testing, you must check if the index is < 128 or use IsMasked()
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//
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// if (someChar < 128 && MaskCRLF()[someChar]) this is \r or \n
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static const ASCIIMaskArray& MaskCRLF();
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static const ASCIIMaskArray& Mask0to9();
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static const ASCIIMaskArray& MaskCRLFTab();
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static const ASCIIMaskArray& MaskWhitespace();
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static MOZ_ALWAYS_INLINE bool IsMasked(const ASCIIMaskArray& aMask, uint32_t aChar)
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{
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return aChar < 128 && aMask[aChar];
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}
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};
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// Outside of the preset ones, use these templates to create more masks.
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//
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// The example creation will look like this:
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//
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// constexpr bool TestABC(char c) { return c == 'A' || c == 'B' || c == 'C'; }
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// constexpr std::array<bool, 128> sABCMask = CreateASCIIMask(TestABC);
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// ...
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// if (someChar < 128 && sABCMask[someChar]) this is A or B or C
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namespace details
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{
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template<typename F, size_t... Indices>
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constexpr std::array<bool, 128> CreateASCIIMask(F fun, mozilla::IndexSequence<Indices...>)
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{
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return {{ fun(Indices)... }};
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}
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} // namespace details
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template<typename F>
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constexpr std::array<bool, 128> CreateASCIIMask(F fun)
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{
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return details::CreateASCIIMask(fun, mozilla::MakeIndexSequence<128>::Type{});
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}
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} // namespace mozilla
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#endif // nsASCIIMask_h_
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