v1/__algorithm/fill_n.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___ALGORITHM_FILL_N_H
0010 #define _LIBCPP___ALGORITHM_FILL_N_H
0011
0012 #include <__algorithm/min.h>
0013 #include <__config>
0014 #include <__fwd/bit_reference.h>
0015 #include <__memory/pointer_traits.h>
0016 #include <__utility/convert_to_integral.h>
0017
0018 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0019 #  pragma GCC system_header
0020 #endif
0021
0022 _LIBCPP_PUSH_MACROS
0023 #include <__undef_macros>
0024
0025 _LIBCPP_BEGIN_NAMESPACE_STD
0026
0027 // fill_n isn't specialized for std::memset, because the compiler already optimizes the loop to a call to std::memset.
0028
0029 template <class _OutputIterator, class _Size, class _Tp>
0030 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
0031 __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value);
0032
0033 template <bool _FillVal, class _Cp>
0034 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void
0035 __fill_n_bool(__bit_iterator<_Cp, false> __first, typename __size_difference_type_traits<_Cp>::size_type __n) {
0036   using _It            = __bit_iterator<_Cp, false>;
0037   using __storage_type = typename _It::__storage_type;
0038
0039   const int __bits_per_word = _It::__bits_per_word;
0040   // do first partial word
0041   if (__first.__ctz_ != 0) {
0042     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
0043     __storage_type __dn    = std::min(__clz_f, __n);
0044     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
0045     if (_FillVal)
0046       *__first.__seg_ |= __m;
0047     else
0048       *__first.__seg_ &= ~__m;
0049     __n -= __dn;
0050     ++__first.__seg_;
0051   }
0052   // do middle whole words
0053   __storage_type __nw = __n / __bits_per_word;
0054   std::__fill_n(std::__to_address(__first.__seg_), __nw, _FillVal ? static_cast<__storage_type>(-1) : 0);
0055   __n -= __nw * __bits_per_word;
0056   // do last partial word
0057   if (__n > 0) {
0058     __first.__seg_ += __nw;
0059     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
0060     if (_FillVal)
0061       *__first.__seg_ |= __m;
0062     else
0063       *__first.__seg_ &= ~__m;
0064   }
0065 }
0066
0067 template <class _Cp, class _Size>
0068 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bit_iterator<_Cp, false>
0069 __fill_n(__bit_iterator<_Cp, false> __first, _Size __n, const bool& __value) {
0070   if (__n > 0) {
0071     if (__value)
0072       std::__fill_n_bool<true>(__first, __n);
0073     else
0074       std::__fill_n_bool<false>(__first, __n);
0075   }
0076   return __first + __n;
0077 }
0078
0079 template <class _OutputIterator, class _Size, class _Tp>
0080 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
0081 __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value) {
0082   for (; __n > 0; ++__first, (void)--__n)
0083     *__first = __value;
0084   return __first;
0085 }
0086
0087 template <class _OutputIterator, class _Size, class _Tp>
0088 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
0089 fill_n(_OutputIterator __first, _Size __n, const _Tp& __value) {
0090   return std::__fill_n(__first, std::__convert_to_integral(__n), __value);
0091 }
0092
0093 _LIBCPP_END_NAMESPACE_STD
0094
0095 _LIBCPP_POP_MACROS
0096
0097 #endif // _LIBCPP___ALGORITHM_FILL_N_H