//      fvkernel.c
//
//      2009 Wil van Lierop <support@sa-maastricht.net>
//
//      This program is free software; you can redistribute it and/or modify
//      it under the terms of the GNU General Public License as published by
//      the Free Software Foundation; either version 2 of the License, or
//      (at your option) any later version.
//
//      This program is distributed in the hope that it will be useful,
//      but WITHOUT ANY WARRANTY; without even the implied warranty of
//      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//      GNU General Public License for more details.
//
//      You should have received a copy of the GNU General Public License
//      along with this program; if not, write to the Free Software
//      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
//      MA 02110-1301, USA.

//	fvkernel extracts kernel version string from the vmlinuz kernel file.

//	At the moment it assumes that this string can be found directly
//	after the video mode magic 0x25780A00, i have no debian nor ubuntu
//	kernels found or selfcompiled kernels on 2.6 systems that have otherwise.
//	Please report if you do find those exceptions.

#include <stdio.h>

#define	MAGIC 0x25780A00

int extract_ks(int file_handle, FILE * ptr )
{
	// this function extract kernel version string
	// even if there are preceding or trailing 0x00.
	int c= file_handle;
	int s_stat= 0;
	int d_stat= 0;

	while (s_stat == 0)
	{
		c = fgetc(ptr);
		if (c != 0x00)
		{
			printf("%c",c);
			d_stat= 1;
		}
		else
		{
		if (d_stat == 1)
		{
			s_stat = 1;
		}
		}
	}
	return 0;
}

int get_kernelstring(char * prog_name, char * filename)
{
	int c=' ';
	FILE * ptr;

	// lets make a file handle to our kernel we have choosen
	// but only readonly, and gracefully exit when not found
	ptr = fopen (filename, "r");
	if(ptr==NULL)
	{
		printf("\n\t%s: Unable to open %s\n\n", prog_name, filename);
		return 0;
	}
	// lets find our magic number in the fastest way.
	// This code could be improved; i found this
	// the fastest way to do it. It also gracefully
	// will be quiet, if not run on a kernel file.
	// It will then return nothing to the standaard
	// output.
	while (c != EOF)
	{
		c = fgetc(ptr);
		if( c==0x25 )
		{
			c = fgetc(ptr);
			if( c==0x78 )
			{
				c = fgetc(ptr);
				if( c==0x0A )
				{
					c = fgetc(ptr);
					if( c==0x00 )
					{
						extract_ks(c, ptr);
						// we are done, but lets nice it up with just an end of line
						// and close our file handle before we return
						// because we dont want to walk the rest of the file
						// anymore, we are done.
						printf("\n");
						fclose(ptr);
						return 0;
					}
				}
			}
		}
	}
    fclose(ptr);
    return 0;
}


int main(int argc, char** argv)
{
	// inform user if no /path/kernel are given,
	// and blurb a syntax message
	if (argc != 2)
	{
		printf("\n\t%s syntax:", argv[0]);
		printf("\t%s [/path/kernel]\n\n", argv[0]);
		return 0;
	}
	// invoke get_kernelstring but at least warn
	// user when something unforseen has happened
	// like not being a kernel file, but with a magic number.
    if (get_kernelstring( argv[0], argv[1]) != 0)
    {
		printf("unkown error happened, are you sure you pointed me to a kernel file?\n");
    }

	return 0;
}