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       1             : /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
       2             :  * This Source Code Form is subject to the terms of the Mozilla Public
       3             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       4             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       5             : 
       6             : #ifndef nsASCIIMask_h_
       7             : #define nsASCIIMask_h_
       8             : 
       9             : #include <array>
      10             : #include "mozilla/IndexSequence.h"
      11             : 
      12             : typedef std::array<bool, 128> ASCIIMaskArray;
      13             : 
      14             : namespace mozilla {
      15             : 
      16             : // Boolean arrays, fixed size and filled in at compile time, meant to
      17             : // record something about each of the (standard) ASCII characters.
      18             : // No extended ASCII for now, there has been no use case.
      19             : // If you have loops that go through a string character by character
      20             : // and test for equality to a certain set of characters before deciding
      21             : // on a course of action, chances are building up one of these arrays
      22             : // and using it is going to be faster, especially if the set of
      23             : // characters is more than one long, and known at compile time.
      24             : class ASCIIMask
      25             : {
      26             : public:
      27             :   // Preset masks for some common character groups
      28             :   // When testing, you must check if the index is < 128 or use IsMasked()
      29             :   //
      30             :   // if (someChar < 128 && MaskCRLF()[someChar]) this is \r or \n
      31             : 
      32             :   static const ASCIIMaskArray& MaskCRLF();
      33             :   static const ASCIIMaskArray& Mask0to9();
      34             :   static const ASCIIMaskArray& MaskCRLFTab();
      35             :   static const ASCIIMaskArray& MaskWhitespace();
      36             : 
      37      439336 :   static MOZ_ALWAYS_INLINE bool IsMasked(const ASCIIMaskArray& aMask, uint32_t aChar)
      38             :   {
      39      439336 :     return aChar < 128 && aMask[aChar];
      40             :   }
      41             : };
      42             : 
      43             : // Outside of the preset ones, use these templates to create more masks.
      44             : //
      45             : // The example creation will look like this:
      46             : //
      47             : // constexpr bool TestABC(char c) { return c == 'A' || c == 'B' || c == 'C'; }
      48             : // constexpr std::array<bool, 128> sABCMask = CreateASCIIMask(TestABC);
      49             : // ...
      50             : // if (someChar < 128 && sABCMask[someChar]) this is A or B or C
      51             : 
      52             : 
      53             : namespace details
      54             : {
      55             : template<typename F, size_t... Indices>
      56             : constexpr std::array<bool, 128> CreateASCIIMask(F fun, mozilla::IndexSequence<Indices...>)
      57             : {
      58             :   return {{ fun(Indices)... }};
      59             : }
      60             : } // namespace details
      61             : 
      62             : template<typename F>
      63             : constexpr std::array<bool, 128> CreateASCIIMask(F fun)
      64             : {
      65             :   return details::CreateASCIIMask(fun, mozilla::MakeIndexSequence<128>::Type{});
      66             : }
      67             : 
      68             : } // namespace mozilla
      69             : 
      70             : #endif // nsASCIIMask_h_