poco/Foundation/include/Poco/Format.h

//
// Format.h
//
// Library: Foundation
// Package: Core
// Module:  Format
//
// Definition of the format freestanding function.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_Format_INCLUDED
#define Foundation_Format_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Any.h"
#include <vector>
#include <type_traits>


namespace Poco {


std::string Foundation_API format(const std::string& fmt, const Any& value);
	/// This function implements sprintf-style formatting in a typesafe way.
	/// Various variants of the function are available, supporting a
	/// different number of arguments (up to six).
	///
	/// The formatting is controlled by the format string in fmt.
	/// Format strings are quite similar to those of the std::printf() function, but
	/// there are some minor differences.
	///
	/// The format string can consist of any sequence of characters; certain
	/// characters have a special meaning. Characters without a special meaning
	/// are copied verbatim to the result. A percent sign (%) marks the beginning
	/// of a format specification. Format specifications have the following syntax:
	///
	///   %[<index>][<flags>][<width>][.<precision>][<modifier>]<type>
	///
	/// Index, flags, width, precision and prefix are optional. The only required part of
	/// the format specification, apart from the percent sign, is the type.
	///
	/// The optional index argument has the format "[<n>]" and allows to
	/// address an argument by its zero-based position (see the example below).
	///
	/// Following are valid type specifications and their meaning:
	///
	///   * b boolean (true = 1, false = 0)
	///   * c character
	///   * d signed decimal integer
	///   * i signed decimal integer
	///   * o unsigned octal integer
	///   * u unsigned decimal integer
	///   * x unsigned hexadecimal integer (lower case)
	///   * X unsigned hexadecimal integer (upper case)
	///   * e signed floating-point value in the form [-]d.dddde[<sign>]dd[d]
	///   * E signed floating-point value in the form [-]d.ddddE[<sign>]dd[d]
	///   * f signed floating-point value in the form [-]dddd.dddd
	///   * s std::string
	///   * z std::size_t
	///
	/// The following flags are supported:
	///
	///   * - left align the result within the given field width
	///   * + prefix the output value with a sign (+ or -) if the output value is of a signed type
	///   * 0 if width is prefixed with 0, zeros are added until the minimum width is reached
	///   * # For o, x, X, the # flag prefixes any nonzero output value with 0, 0x, or 0X, respectively;
	///     for e, E, f, the # flag forces the output value to contain a decimal point in all cases.
	///
	/// The following modifiers are supported:
	///
	///   * (none) argument is char (c), int (d, i), unsigned (o, u, x, X) double (e, E, f, g, G) or string (s)
	///   * l      argument is long (d, i), unsigned long (o, u, x, X) or long double (e, E, f, g, G)
	///   * L      argument is long long (d, i), unsigned long long (o, u, x, X)
	///   * h      argument is short (d, i), unsigned short (o, u, x, X) or float (e, E, f, g, G)
	///   * ?      argument is any signed or unsigned int, short, long, or 64-bit integer (d, i, o, x, X)
	///
	/// The width argument is a nonnegative decimal integer or '*' with an additional nonnegative integer value
	/// preceding the value to be formated, controlling the minimum number of characters printed.
	/// If the number of characters in the output value is less than the specified width, blanks or
	/// leading zeros are added, according to the specified flags (-, +, 0).
	///
	/// Precision is a nonnegative decimal integer or '*' with an additional nonnegative integer value preceding
	/// the value to be formated, preceded by a period (.), which specifies the number of characters
	/// to be printed, the number of decimal places, or the number of significant digits.
	///
	/// Throws an InvalidArgumentException if an argument index is out of range.
	///
	/// Starting with release 1.4.3, an argument that does not match the format
	/// specifier no longer results in a BadCastException. The string [ERRFMT] is
	/// written to the result string instead.
	///
	/// If there are more format specifiers than values, the format specifiers without a corresponding value
	/// are copied verbatim to output.
	///
	/// If there are more values than format specifiers, the superfluous values are ignored.
	///
	/// Usage Examples:
	///     std::string s1 = format("The answer to life, the universe, and everything is %d", 42);
	///     std::string s2 = format("second: %[1]d, first: %[0]d", 1, 2);

void Foundation_API format(std::string& result, const char *fmt, const std::vector<Any>& values);
	/// Supports a variable number of arguments.

void Foundation_API format(std::string& result, const std::string& fmt, const std::vector<Any>& values);
	/// Supports a variable number of arguments.

inline void formatAny(std::string& result, const std::string& fmt, const std::vector<Any>& values)
	/// Supports a variable number of arguments and is used by
	/// all other variants of format().
{
	format(result, fmt, values);
}

inline void formatAny(std::string& result, const char *fmt, const std::vector<Any>& values)
	/// Supports a variable number of arguments and is used by
	/// all other variants of format().
{
	format(result, fmt, values);
}

template <typename T, typename... Args>
void format(std::string& result, const std::string& fmt, T arg1, Args... args)
	/// Appends the formatted string to result.
{
	std::vector<Any> values;
	values.reserve(sizeof...(Args) + 1);
	values.emplace_back(arg1);
	values.insert(values.end(), { args... });
	formatAny(result, fmt, values);
}


template <typename T, typename... Args>
void format(std::string& result, const char* fmt, T arg1, Args... args)
	/// Appends the formatted string to result.
{
	std::vector<Any> values;
	values.reserve(sizeof...(Args) + 1);
	values.emplace_back(arg1);
	values.insert(values.end(), { args... });
	formatAny(result, fmt, values);
}


template <typename T, typename... Args>
std::string format(const std::string& fmt, T arg1, Args... args)
	/// Returns the formatted string.
{
	std::vector<Any> values;
	values.reserve(sizeof...(Args) + 1);
	values.emplace_back(arg1);
	values.insert(values.end(), { args... });
	std::string result;
	formatAny(result, fmt, values);
	return result;
}


template <typename T, typename... Args>
std::string format(const char* fmt, T arg1, Args... args)
	/// Returns the formatted string.
{
	std::vector<Any> values;
	values.reserve(sizeof...(Args) + 1);
	values.emplace_back(arg1);
	values.insert(values.end(), { args... });
	std::string result;
	formatAny(result, fmt, values);
	return result;
}


} // namespace Poco


#endif // Foundation_Format_INCLUDED