sources/format.cpp

/*
	Copyright 2014 Teemu Piippo
	All rights reserved.

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions
	are met:

	1. Redistributions of source code must retain the above copyright
	   notice, this list of conditions and the following disclaimer.
	2. Redistributions in binary form must reproduce the above copyright
	   notice, this list of conditions and the following disclaimer in the
	   documentation and/or other materials provided with the distribution.
	3. Neither the name of the copyright holder nor the names of its
	   contributors may be used to endorse or promote products derived from
	   this software without specific prior written permission.

	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
	TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
	PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER
	OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
	LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
	NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
	SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <cstdio>
#include "format.h"

// -------------------------------------------------------------------------------------------------
// Throws an error while formatting the string
//
static auto format_error (String fmtstr, const String errdescribe, int pos) -> void
{
	fmtstr.replace ("\n", " ");
	fmtstr.replace ("\t", " ");
	String errmsg ("With format string:\n" + fmtstr + "\n");

	for (int x = 0; x < pos; ++x)
		errmsg += "-";

	errmsg += "^\n" + errdescribe;
	throw std::logic_error (errmsg.std_string());
}

// -------------------------------------------------------------------------------------------------
// Main formatter algorithm.
//
auto format_args (const String& fmtstr, const Vector<String>& args) -> String
{
	String fmt = fmtstr;
	int pos = 0;

	while ((pos = fmt.find ("%", pos)) != -1)
	{
		if (fmt[pos + 1] == '%')
		{
			fmt.replace (pos, 2, "%");
			pos++;
			continue;
		}

		int ofs = 1;
		char mod = '\0';

		// handle modifiers
		if (fmt[pos + ofs] == 's' or fmt[pos + ofs] == 'x' or fmt[pos + ofs] == 'd')
		{
			mod = fmt[pos + ofs];
			ofs++;
		}

		if (fmt[pos + ofs] < '1' or fmt[pos + ofs] > '9')
		{
			format_error (fmtstr, "bad format string, expected non-zero digit with "
				"optional modifier after '%%'", pos);
		}

		int i = fmt[pos + ofs] - '0';

		if (i > args.size())
			format_error (fmtstr, String ("Format argument #") + i + " used but not defined.", pos);

		String replacement = args[i - 1];

		switch (mod)
		{
		case 's': replacement = (replacement == "1") ? "" : "s";      break;
		case 'd': replacement.sprintf ("%d", replacement[0]);         break;
		case 'x': replacement.sprintf ("0x%x", replacement.to_int()); break;
		default: break;
		}

		fmt.replace (pos, 1 + ofs, replacement);
		pos += replacement.length();
	}

	return fmt;
}