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author | Vincent Ambo <tazjin@google.com> | 2020-05-20T01·32+0100 |
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committer | Vincent Ambo <tazjin@google.com> | 2020-05-20T01·32+0100 |
commit | fc8dc48020ac5b52731d0828a96ea4d2526c77ba (patch) | |
tree | 353204eea3268095a9ad3f5345720f32c2615c69 /third_party/abseil_cpp/absl/random/internal/iostream_state_saver.h | |
parent | ffb2ae54beb5796cd408fbe15d2d2da09ff37adf (diff) | |
parent | 768eb2ca2857342673fcd462792ce04b8bac3fa3 (diff) |
Add 'third_party/abseil_cpp/' from commit '768eb2ca2857342673fcd462792ce04b8bac3fa3' r/781
git-subtree-dir: third_party/abseil_cpp git-subtree-mainline: ffb2ae54beb5796cd408fbe15d2d2da09ff37adf git-subtree-split: 768eb2ca2857342673fcd462792ce04b8bac3fa3
Diffstat (limited to 'third_party/abseil_cpp/absl/random/internal/iostream_state_saver.h')
-rw-r--r-- | third_party/abseil_cpp/absl/random/internal/iostream_state_saver.h | 245 |
1 files changed, 245 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/random/internal/iostream_state_saver.h b/third_party/abseil_cpp/absl/random/internal/iostream_state_saver.h new file mode 100644 index 000000000000..e6e242ee1e66 --- /dev/null +++ b/third_party/abseil_cpp/absl/random/internal/iostream_state_saver.h @@ -0,0 +1,245 @@ +// Copyright 2017 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_ +#define ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_ + +#include <cmath> +#include <iostream> +#include <limits> +#include <type_traits> + +#include "absl/meta/type_traits.h" +#include "absl/numeric/int128.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace random_internal { + +// The null_state_saver does nothing. +template <typename T> +class null_state_saver { + public: + using stream_type = T; + using flags_type = std::ios_base::fmtflags; + + null_state_saver(T&, flags_type) {} + ~null_state_saver() {} +}; + +// ostream_state_saver is a RAII object to save and restore the common +// basic_ostream flags used when implementing `operator <<()` on any of +// the absl random distributions. +template <typename OStream> +class ostream_state_saver { + public: + using ostream_type = OStream; + using flags_type = std::ios_base::fmtflags; + using fill_type = typename ostream_type::char_type; + using precision_type = std::streamsize; + + ostream_state_saver(ostream_type& os, // NOLINT(runtime/references) + flags_type flags, fill_type fill) + : os_(os), + flags_(os.flags(flags)), + fill_(os.fill(fill)), + precision_(os.precision()) { + // Save state in initialized variables. + } + + ~ostream_state_saver() { + // Restore saved state. + os_.precision(precision_); + os_.fill(fill_); + os_.flags(flags_); + } + + private: + ostream_type& os_; + const flags_type flags_; + const fill_type fill_; + const precision_type precision_; +}; + +#if defined(__NDK_MAJOR__) && __NDK_MAJOR__ < 16 +#define ABSL_RANDOM_INTERNAL_IOSTREAM_HEXFLOAT 1 +#else +#define ABSL_RANDOM_INTERNAL_IOSTREAM_HEXFLOAT 0 +#endif + +template <typename CharT, typename Traits> +ostream_state_saver<std::basic_ostream<CharT, Traits>> make_ostream_state_saver( + std::basic_ostream<CharT, Traits>& os, // NOLINT(runtime/references) + std::ios_base::fmtflags flags = std::ios_base::dec | std::ios_base::left | +#if ABSL_RANDOM_INTERNAL_IOSTREAM_HEXFLOAT + std::ios_base::fixed | +#endif + std::ios_base::scientific) { + using result_type = ostream_state_saver<std::basic_ostream<CharT, Traits>>; + return result_type(os, flags, os.widen(' ')); +} + +template <typename T> +typename absl::enable_if_t<!std::is_base_of<std::ios_base, T>::value, + null_state_saver<T>> +make_ostream_state_saver(T& is, // NOLINT(runtime/references) + std::ios_base::fmtflags flags = std::ios_base::dec) { + std::cerr << "null_state_saver"; + using result_type = null_state_saver<T>; + return result_type(is, flags); +} + +// stream_precision_helper<type>::kPrecision returns the base 10 precision +// required to stream and reconstruct a real type exact binary value through +// a binary->decimal->binary transition. +template <typename T> +struct stream_precision_helper { + // max_digits10 may be 0 on MSVC; if so, use digits10 + 3. + static constexpr int kPrecision = + (std::numeric_limits<T>::max_digits10 > std::numeric_limits<T>::digits10) + ? std::numeric_limits<T>::max_digits10 + : (std::numeric_limits<T>::digits10 + 3); +}; + +template <> +struct stream_precision_helper<float> { + static constexpr int kPrecision = 9; +}; +template <> +struct stream_precision_helper<double> { + static constexpr int kPrecision = 17; +}; +template <> +struct stream_precision_helper<long double> { + static constexpr int kPrecision = 36; // assuming fp128 +}; + +// istream_state_saver is a RAII object to save and restore the common +// std::basic_istream<> flags used when implementing `operator >>()` on any of +// the absl random distributions. +template <typename IStream> +class istream_state_saver { + public: + using istream_type = IStream; + using flags_type = std::ios_base::fmtflags; + + istream_state_saver(istream_type& is, // NOLINT(runtime/references) + flags_type flags) + : is_(is), flags_(is.flags(flags)) {} + + ~istream_state_saver() { is_.flags(flags_); } + + private: + istream_type& is_; + flags_type flags_; +}; + +template <typename CharT, typename Traits> +istream_state_saver<std::basic_istream<CharT, Traits>> make_istream_state_saver( + std::basic_istream<CharT, Traits>& is, // NOLINT(runtime/references) + std::ios_base::fmtflags flags = std::ios_base::dec | + std::ios_base::scientific | + std::ios_base::skipws) { + using result_type = istream_state_saver<std::basic_istream<CharT, Traits>>; + return result_type(is, flags); +} + +template <typename T> +typename absl::enable_if_t<!std::is_base_of<std::ios_base, T>::value, + null_state_saver<T>> +make_istream_state_saver(T& is, // NOLINT(runtime/references) + std::ios_base::fmtflags flags = std::ios_base::dec) { + using result_type = null_state_saver<T>; + return result_type(is, flags); +} + +// stream_format_type<T> is a helper struct to convert types which +// basic_iostream cannot output as decimal numbers into types which +// basic_iostream can output as decimal numbers. Specifically: +// * signed/unsigned char-width types are converted to int. +// * TODO(lar): __int128 => uint128, except there is no operator << yet. +// +template <typename T> +struct stream_format_type + : public std::conditional<(sizeof(T) == sizeof(char)), int, T> {}; + +// stream_u128_helper allows us to write out either absl::uint128 or +// __uint128_t types in the same way, which enables their use as internal +// state of PRNG engines. +template <typename T> +struct stream_u128_helper; + +template <> +struct stream_u128_helper<absl::uint128> { + template <typename IStream> + inline absl::uint128 read(IStream& in) { + uint64_t h = 0; + uint64_t l = 0; + in >> h >> l; + return absl::MakeUint128(h, l); + } + + template <typename OStream> + inline void write(absl::uint128 val, OStream& out) { + uint64_t h = absl::Uint128High64(val); + uint64_t l = absl::Uint128Low64(val); + out << h << out.fill() << l; + } +}; + +#ifdef ABSL_HAVE_INTRINSIC_INT128 +template <> +struct stream_u128_helper<__uint128_t> { + template <typename IStream> + inline __uint128_t read(IStream& in) { + uint64_t h = 0; + uint64_t l = 0; + in >> h >> l; + return (static_cast<__uint128_t>(h) << 64) | l; + } + + template <typename OStream> + inline void write(__uint128_t val, OStream& out) { + uint64_t h = static_cast<uint64_t>(val >> 64u); + uint64_t l = static_cast<uint64_t>(val); + out << h << out.fill() << l; + } +}; +#endif + +template <typename FloatType, typename IStream> +inline FloatType read_floating_point(IStream& is) { + static_assert(std::is_floating_point<FloatType>::value, ""); + FloatType dest; + is >> dest; + // Parsing a double value may report a subnormal value as an error + // despite being able to represent it. + // See https://stackoverflow.com/q/52410931/3286653 + // It may also report an underflow when parsing DOUBLE_MIN as an + // ERANGE error, as the parsed value may be smaller than DOUBLE_MIN + // and rounded up. + // See: https://stackoverflow.com/q/42005462 + if (is.fail() && + (std::fabs(dest) == (std::numeric_limits<FloatType>::min)() || + std::fpclassify(dest) == FP_SUBNORMAL)) { + is.clear(is.rdstate() & (~std::ios_base::failbit)); + } + return dest; +} + +} // namespace random_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_ |