--- /dev/null
+// 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 {
+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 = Uint128High64(val);
+ uint64_t l = 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
+} // namespace absl
+
+#endif // ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_
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