src/format.cc

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

static void draw_pos (const string& fmt, int pos)
{
	string rep (fmt);
	rep.replace ("\n", "↵");
	rep.replace ("\t", "⇥");

	fprintf (stderr, "%s\n", rep.chars());

	for (int x = 0; x < pos; ++x)
		fprintf (stderr, "-");

	fprintf (stderr, "^\n");
}

string format_args (const list<format_arg>& args)
{
	const string& fmtstr = args[0].as_string();
	assert (args.size() >= 1);

	if (args.size() == 1)
		return args[0].as_string();

	string fmt = fmtstr;
	string out;
	int pos = 0;

	while ((pos = fmt.first ("%", 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' || fmt[ pos + ofs ] == 'x')
		{
			mod = fmt[ pos + ofs ];
			ofs++;
		}

		if (!isdigit (fmt[ pos + ofs ]))
		{
			fprintf (stderr, "bad format string, expected digit with optional "
					 "modifier after '%%':\n");
			draw_pos (fmt, pos);
			return fmt;
		}

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

		if (i >= args.size())
		{
			fprintf (stderr, "format arg #%d used but not defined: %s\n", i, fmtstr.chars());
			return fmt;
		}

		string repl = args[i].as_string();

		if (mod == 's')
		{
			repl = (repl == "1") ? "" : "s";
		}

		elif (mod == 'd')
		{
			repl.sprintf ("%d", repl[0]);
		}
		elif (mod == 'x')
		{
			// modifier x: reinterpret the argument as hex
			repl.sprintf ("0x%X", strtol (repl.chars(), null, 10));
		}

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

	return fmt;
}

void print_args (FILE* fp, const list<format_arg>& args)
{
	string out = format_args (args);
	fprintf (fp, "%s", out.chars());
}