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/* HEADER:       (cat #); 
   TITLE:        Tab Insertion Text Filter; 
   DATE:         06/07/1989; 
   DESCRIPTION:  "Reads an existing text file, formatted with only spaces, and 
                 produces a new file, formatted with the optimum combination 
                 of spaces and tabs of a specified width. The original file can 
                 be produced from a file containing tabs (presumably of a 
                 different width) using XTAB.COM."; 
   KEYWORDS:     filter, detab, text formatters, tabs, file.; 
   SYSTEM:       MS-DOS; 
   FILENAME:     ITAB.C; 
   SEE-ALSO:     xtab.c, xitab.txt; 
   AUTHOR:       Eric Horner; 
   COMPILERS:    Turbo C 2.0; 
*/ 
 
#include  
 
	/***** error messages *****/ 
 
char *ers[] = 
{ 
	"\7\nUnable to open input file!\n", 
	"\7\nUnable to open output file!\n", 
	"\7\nUsage is: itab infile outfile tabs\n\n(tabs = new tab width).\n", 
	"\ninfile must contain no tabs, and can be made using xtab.com!\n" 
};	 
 
main(int argc, char *argv[]) 
{ 
    int ch, charcnt, spccnt, tabs; 
    FILE *infile, *outfile; 
 
    if (argc == 4) 
    { 
	if ((infile = fopen(argv[1], "r")) == 0) 
	{ 
	    printf("%s", ers[0]); 
	    fclose(infile); 
	    exit(1); 
	} 
	if ((outfile = fopen(argv[2], "w")) == 0) 
	{ 
	    printf("%s", ers[1]); 
	    fclose(infile); 
	    fclose(outfile); 
	    exit(1); 
	} 
	tabs = atoi(argv[3]);		/* get number of spaces per tab */ 
	charcnt = 0;			/* char count within line       */ 
	spccnt = 0;			/* space count within tab	*/ 
 
	while ((ch = fgetc(infile)) != EOF) 
	{ 
	    switch (ch) 
	    { 
		case '\x20': ++charcnt; 
			     ++spccnt; 
			     if (charcnt%tabs == 0) 
			     { 
				spccnt = 0; 
				fputc('\t', outfile); 
			     } 
			     break; 
		    default: if (spccnt > 0) 
			     { 
				 for(;spccnt > 0; --spccnt) 
				 fputc('\x20', outfile); 
			     } 
			     if ((ch != '\0') && (ch != '\n')) 
				 ++charcnt; 
			     if (ch == '\n') 
				 charcnt = 0; 
			     fputc((char) ch, outfile); 
			     break; 
	    }; 
	} 
    } 
    else 
    { 
	printf("%s", ers[2]); 
	printf("%s", ers[3]); 
	exit(1); 
    } 
    fclose(infile); 
    fclose(outfile); 
}