src/tint/utils/text/string_stream.h - dawn - Git at Google

 // Copyright 2023 The Tint 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
 //
 //     http://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 SRC_TINT_UTILS_TEXT_STRING_STREAM_H_
 #define SRC_TINT_UTILS_TEXT_STRING_STREAM_H_

 #include <functional>
 #include <iomanip>
 #include <iterator>
 #include <limits>
 #include <sstream>
 #include <string>
 #include <utility>

 #include "src/tint/utils/text/unicode.h"

 namespace tint {

 /// Stringstream wrapper which automatically resets the locale and sets floating point emission
 /// settings needed for Tint.
 class StringStream {
     using SetWRetTy = decltype(std::setw(std::declval<int>()));
     using SetPrecisionRetTy = decltype(std::setprecision(std::declval<int>()));
     using SetFillRetTy = decltype(std::setfill(std::declval<char>()));

     /// Evaluates to true if `T` is the return type of std::setw, std:setprecision or std::setfill.
     template <typename T>
     static constexpr bool IsSetType = std::is_same_v<SetWRetTy, std::decay_t<T>> ||
                                       std::is_same_v<SetPrecisionRetTy, std::decay_t<T>> ||
                                       std::is_same_v<SetFillRetTy, std::decay_t<T>>;

   public:
     /// @see tint::traits::IsOStream
     static constexpr bool IsStreamWriter = true;

     /// Constructor
     StringStream();
     /// Destructor
     ~StringStream();

     /// @returns the format flags for the stream
     std::ios_base::fmtflags flags() const { return sstream_.flags(); }

     /// @param flags the flags to set
     /// @returns the original format flags
     std::ios_base::fmtflags flags(std::ios_base::fmtflags flags) { return sstream_.flags(flags); }

     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     template <typename T,
               typename std::enable_if_t<std::is_integral_v<std::decay_t<T>>, bool> = true>
     StringStream& operator<<(T&& value) {
         return EmitValue(std::forward<T>(value));
     }

     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     StringStream& operator<<(const char* value) { return EmitValue(value); }
     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     StringStream& operator<<(const std::string& value) { return EmitValue(value); }
     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     StringStream& operator<<(std::string_view value) { return EmitValue(value); }

     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     StringStream& operator<<(const void* value) { return EmitValue(value); }

     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     template <typename T,
               typename std::enable_if_t<std::is_floating_point_v<std::decay_t<T>>, bool> = true>
     StringStream& operator<<(T&& value) {
         return EmitFloat(std::forward<T>(value));
     }

     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     template <typename T>
     StringStream& EmitValue(T&& value) {
         sstream_ << std::forward<T>(value);
         return *this;
     }

     /// Emit `value` to the stream
     /// @param value the value to emit
     /// @returns a reference to this
     template <typename T>
     StringStream& EmitFloat(const T& value) {
         // Try printing the float in fixed point, with a smallish limit on the precision
         std::stringstream fixed;
         fixed.flags(fixed.flags() | std::ios_base::showpoint | std::ios_base::fixed);
         fixed.imbue(std::locale::classic());
         fixed.precision(20);
         fixed << value;

         std::string str = fixed.str();

         // If this string can be parsed without loss of information, use it.
         // (Use double here to dodge a bug in older libc++ versions which would incorrectly read
         // back FLT_MAX as INF.)
         double roundtripped;
         fixed >> roundtripped;

         // Strip trailing zeros from the number.
         auto float_equal_no_warning = std::equal_to<T>();
         if (float_equal_no_warning(value, static_cast<T>(roundtripped))) {
             while (str.length() >= 2 && str[str.size() - 1] == '0' && str[str.size() - 2] != '.') {
                 str.pop_back();
             }

             sstream_ << str;
             return *this;
         }

         // Resort to scientific, with the minimum precision needed to preserve the whole float
         std::stringstream sci;
         sci.imbue(std::locale::classic());
         sci.precision(std::numeric_limits<T>::max_digits10);
         sci << value;
         sstream_ << sci.str();

         return *this;
     }

     /// Swaps streams
     /// @param other stream to swap too
     void swap(StringStream& other) { sstream_.swap(other.sstream_); }

     /// repeat queues the character c to be written to the printer n times.
     /// @param c the character to print `n` times
     /// @param n the number of times to print character `c`
     void repeat(char c, size_t n) { std::fill_n(std::ostream_iterator<char>(sstream_), n, c); }

     /// The callback to emit a `endl` to the stream
     using StdEndl = std::ostream& (*)(std::ostream&);

     /// @param manipulator the callback to emit too
     /// @returns a reference to this
     StringStream& operator<<(StdEndl manipulator) {
         // call the function, and return it's value
         manipulator(sstream_);
         return *this;
     }

     /// @param manipulator the callback to emit too
     /// @returns a reference to this
     StringStream& operator<<(decltype(std::hex) manipulator) {
         // call the function, and return it's value
         manipulator(sstream_);
         return *this;
     }

     /// @param value the value to emit
     /// @returns a reference to this
     template <typename T, typename std::enable_if_t<IsSetType<T>, int> = 0>
     StringStream& operator<<(T&& value) {
         // call the function, and return it's value
         sstream_ << std::forward<T>(value);
         return *this;
     }

     /// @returns the current location in the output stream
     uint32_t tellp() { return static_cast<uint32_t>(sstream_.tellp()); }

     /// @returns the string contents of the stream
     std::string str() const { return sstream_.str(); }

   private:
     std::stringstream sstream_;
 };

 /// Writes the CodePoint to the stream.
 /// @param out the stream to write to
 /// @param codepoint the CodePoint to write
 /// @returns out so calls can be chained
 StringStream& operator<<(StringStream& out, CodePoint codepoint);

 }  // namespace tint

 #endif  // SRC_TINT_UTILS_TEXT_STRING_STREAM_H_
	// Copyright 2023 The Tint 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
	//
	// http://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 SRC_TINT_UTILS_TEXT_STRING_STREAM_H_
	#define SRC_TINT_UTILS_TEXT_STRING_STREAM_H_

	#include <functional>
	#include <iomanip>
	#include <iterator>
	#include <limits>
	#include <sstream>
	#include <string>
	#include <utility>

	#include "src/tint/utils/text/unicode.h"

	namespace tint {

	/// Stringstream wrapper which automatically resets the locale and sets floating point emission
	/// settings needed for Tint.
	class StringStream {
	using SetWRetTy = decltype(std::setw(std::declval<int>()));
	using SetPrecisionRetTy = decltype(std::setprecision(std::declval<int>()));
	using SetFillRetTy = decltype(std::setfill(std::declval<char>()));

	/// Evaluates to true if `T` is the return type of std::setw, std:setprecision or std::setfill.
	template <typename T>
	static constexpr bool IsSetType = std::is_same_v<SetWRetTy, std::decay_t<T>> \|\|
	std::is_same_v<SetPrecisionRetTy, std::decay_t<T>> \|\|
	std::is_same_v<SetFillRetTy, std::decay_t<T>>;

	public:
	/// @see tint::traits::IsOStream
	static constexpr bool IsStreamWriter = true;

	/// Constructor
	StringStream();
	/// Destructor
	~StringStream();

	/// @returns the format flags for the stream
	std::ios_base::fmtflags flags() const { return sstream_.flags(); }

	/// @param flags the flags to set
	/// @returns the original format flags
	std::ios_base::fmtflags flags(std::ios_base::fmtflags flags) { return sstream_.flags(flags); }

	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	template <typename T,
	typename std::enable_if_t<std::is_integral_v<std::decay_t<T>>, bool> = true>
	StringStream& operator<<(T&& value) {
	return EmitValue(std::forward<T>(value));
	}

	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	StringStream& operator<<(const char* value) { return EmitValue(value); }
	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	StringStream& operator<<(const std::string& value) { return EmitValue(value); }
	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	StringStream& operator<<(std::string_view value) { return EmitValue(value); }

	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	StringStream& operator<<(const void* value) { return EmitValue(value); }

	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	template <typename T,
	typename std::enable_if_t<std::is_floating_point_v<std::decay_t<T>>, bool> = true>
	StringStream& operator<<(T&& value) {
	return EmitFloat(std::forward<T>(value));
	}

	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	template <typename T>
	StringStream& EmitValue(T&& value) {
	sstream_ << std::forward<T>(value);
	return *this;
	}

	/// Emit `value` to the stream
	/// @param value the value to emit
	/// @returns a reference to this
	template <typename T>
	StringStream& EmitFloat(const T& value) {
	// Try printing the float in fixed point, with a smallish limit on the precision
	std::stringstream fixed;
	fixed.flags(fixed.flags() \| std::ios_base::showpoint \| std::ios_base::fixed);
	fixed.imbue(std::locale::classic());
	fixed.precision(20);
	fixed << value;

	std::string str = fixed.str();

	// If this string can be parsed without loss of information, use it.
	// (Use double here to dodge a bug in older libc++ versions which would incorrectly read
	// back FLT_MAX as INF.)
	double roundtripped;
	fixed >> roundtripped;

	// Strip trailing zeros from the number.
	auto float_equal_no_warning = std::equal_to<T>();
	if (float_equal_no_warning(value, static_cast<T>(roundtripped))) {
	while (str.length() >= 2 && str[str.size() - 1] == '0' && str[str.size() - 2] != '.') {
	str.pop_back();
	}

	sstream_ << str;
	return *this;
	}

	// Resort to scientific, with the minimum precision needed to preserve the whole float
	std::stringstream sci;
	sci.imbue(std::locale::classic());
	sci.precision(std::numeric_limits<T>::max_digits10);
	sci << value;
	sstream_ << sci.str();

	return *this;
	}

	/// Swaps streams
	/// @param other stream to swap too
	void swap(StringStream& other) { sstream_.swap(other.sstream_); }

	/// repeat queues the character c to be written to the printer n times.
	/// @param c the character to print `n` times
	/// @param n the number of times to print character `c`
	void repeat(char c, size_t n) { std::fill_n(std::ostream_iterator<char>(sstream_), n, c); }

	/// The callback to emit a `endl` to the stream
	using StdEndl = std::ostream& (*)(std::ostream&);

	/// @param manipulator the callback to emit too
	/// @returns a reference to this
	StringStream& operator<<(StdEndl manipulator) {
	// call the function, and return it's value
	manipulator(sstream_);
	return *this;
	}

	/// @param manipulator the callback to emit too
	/// @returns a reference to this
	StringStream& operator<<(decltype(std::hex) manipulator) {
	// call the function, and return it's value
	manipulator(sstream_);
	return *this;
	}

	/// @param value the value to emit
	/// @returns a reference to this
	template <typename T, typename std::enable_if_t<IsSetType<T>, int> = 0>
	StringStream& operator<<(T&& value) {
	// call the function, and return it's value
	sstream_ << std::forward<T>(value);
	return *this;
	}

	/// @returns the current location in the output stream
	uint32_t tellp() { return static_cast<uint32_t>(sstream_.tellp()); }

	/// @returns the string contents of the stream
	std::string str() const { return sstream_.str(); }

	private:
	std::stringstream sstream_;
	};

	/// Writes the CodePoint to the stream.
	/// @param out the stream to write to
	/// @param codepoint the CodePoint to write
	/// @returns out so calls can be chained
	StringStream& operator<<(StringStream& out, CodePoint codepoint);

	} // namespace tint

	#endif // SRC_TINT_UTILS_TEXT_STRING_STREAM_H_