libcxx/include/__cxx03/__algorithm/fill_n.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___ALGORITHM_FILL_N_H
  10 #define _LIBCPP___ALGORITHM_FILL_N_H
  11
  12 #include <__cxx03/__algorithm/min.h>
  13 #include <__cxx03/__config>
  14 #include <__cxx03/__fwd/bit_reference.h>
  15 #include <__cxx03/__iterator/iterator_traits.h>
  16 #include <__cxx03/__memory/pointer_traits.h>
  17 #include <__cxx03/__utility/convert_to_integral.h>
  18
  19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  20 #  pragma GCC system_header
  21 #endif
  22
  23 _LIBCPP_PUSH_MACROS
  24 #include <__cxx03/__undef_macros>
  25
  26 _LIBCPP_BEGIN_NAMESPACE_STD
  27
  28 // fill_n isn't specialized for std::memset, because the compiler already optimizes the loop to a call to std::memset.
  29
  30 template <class _OutputIterator, class _Size, class _Tp>
  31 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
  32 __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value);
  33
  34 template <bool _FillVal, class _Cp>
  35 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void
  36 __fill_n_bool(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n) {
  37   using _It            = __bit_iterator<_Cp, false>;
  38   using __storage_type = typename _It::__storage_type;
  39
  40   const int __bits_per_word = _It::__bits_per_word;
  41   // do first partial word
  42   if (__first.__ctz_ != 0) {
  43     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
  44     __storage_type __dn    = std::min(__clz_f, __n);
  45     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
  46     if (_FillVal)
  47       *__first.__seg_ |= __m;
  48     else
  49       *__first.__seg_ &= ~__m;
  50     __n -= __dn;
  51     ++__first.__seg_;
  52   }
  53   // do middle whole words
  54   __storage_type __nw = __n / __bits_per_word;
  55   std::__fill_n(std::__to_address(__first.__seg_), __nw, _FillVal ? static_cast<__storage_type>(-1) : 0);
  56   __n -= __nw * __bits_per_word;
  57   // do last partial word
  58   if (__n > 0) {
  59     __first.__seg_ += __nw;
  60     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
  61     if (_FillVal)
  62       *__first.__seg_ |= __m;
  63     else
  64       *__first.__seg_ &= ~__m;
  65   }
  66 }
  67
  68 template <class _Cp, class _Size>
  69 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bit_iterator<_Cp, false>
  70 __fill_n(__bit_iterator<_Cp, false> __first, _Size __n, const bool& __value) {
  71   if (__n > 0) {
  72     if (__value)
  73       std::__fill_n_bool<true>(__first, __n);
  74     else
  75       std::__fill_n_bool<false>(__first, __n);
  76   }
  77   return __first + __n;
  78 }
  79
  80 template <class _OutputIterator, class _Size, class _Tp>
  81 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
  82 __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value) {
  83   for (; __n > 0; ++__first, (void)--__n)
  84     *__first = __value;
  85   return __first;
  86 }
  87
  88 template <class _OutputIterator, class _Size, class _Tp>
  89 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
  90 fill_n(_OutputIterator __first, _Size __n, const _Tp& __value) {
  91   return std::__fill_n(__first, std::__convert_to_integral(__n), __value);
  92 }
  93
  94 _LIBCPP_END_NAMESPACE_STD
  95
  96 _LIBCPP_POP_MACROS
  97
  98 #endif // _LIBCPP___ALGORITHM_FILL_N_H