#include <stdio.h>
#include <string.h>
int fsize(FILE *sizefile)
{
	int curpos,length;
	curpos=ftell(sizefile);
	fseek(sizefile,0L,SEEK_END);
	length=ftell(sizefile);
	fseek(sizefile, curpos, SEEK_SET);
	return length;
}
void main(int argc, char* argv[])
{
	char* newfilename;
	char* filecontenceptr=strdup("\x00");
	char* ext;
	FILE *readfile,*writefile;
	int filesize;
	if((argc!=2)&&(argc!=3)) printf("Usage: CaltoTxt source (destination)");
	else
	{
		if (argc==2)
		{
			newfilename=strdup("");
			ext=strrchr(argv[1],'.');
			strncat(newfilename,argv[1],ext-argv[1]);
			strcat(newfilename,".txt");
		}
		if (argc==3)
		{
			newfilename=strdup(argv[2]);
		}
		if(strcmp(argv[1],newfilename)==0)
		{
			printf("Destination and source are the same!");
		}
		else
		{
			readfile=fopen(argv[1],"rb");
			if(!readfile) printf("\"%s\" is not found!",argv[1]);
			else
			{
				if(fsize(readfile)<86)
				{
					printf("Invalid file format!");
				}
				else
				{
					char header[9];
					fread(header,8,1,readfile);
					header[8]='\0';
					if(((strcmp(header,"**TI83F*")!=0)&&(strcmp(header,"**TI83**")!=0))||((strcmp(header,"**TI83F*")==0)&&(fsize(readfile)<76)))
					{
						printf("Invalid file format!");
					}
					else
					{
						if(strcmp(header,"**TI83F*")==0)
						{
							filesize=fsize(readfile)-88;
							fseek(readfile, 86, SEEK_SET);
						}
						else
						{
							filesize=fsize(readfile)-86;
							fseek(readfile, 84, SEEK_SET);
						}
						writefile=fopen(newfilename,"wb");
						if(!writefile) printf("Error writing to \"%s\"!",newfilename);
						else
						{
							for(int i=1;i<=filesize;i++)
							{
									fread(filecontenceptr,1,1,readfile);
									fwrite(filecontenceptr,1,1,writefile);
							}
							fclose(writefile);
						}
						fclose(readfile);
					}
				}
			}
		}
	}
}