/*
 * count.xbm
 *
 * Originally written by Chris Stephens 
 * However, his code was so badly mangled that the result barely looks like
 * his anymore.  Nevertheless, give credit where credit is due.
 *
 * Done by Dave Ratner:
 *	code style and multiple bugs fixed
 *	file locking added
 *	added support for multiple counts on different pages 
 *
 * This script is Shareware.  
 * Copyright Dave Ratner 1995.  All rights reserved.
 *
 * This script reads a number from a datafile, increments the number and
 * then writes the new number back to the datafile.  The script then creates
 * an X-bitmap image of the number, similar to the odometer on your car, and
 * returns that to an <img src>.  Therefore, you don't have to have
 * server-side includes enabled or make modifications to the server
 * configuration files in order to use this script.
 * You only need to be able to run CGIs.
 *
 * TO USE:
 *
 * Step 1: 
 * 	Change the definition of COUNT_FILE and ERROR_LOG if required,
 *	though this is not strictly necessary, just whatever you like best.
 *
 * Step 2:
 * 	Create the file COUNT_FILE and add all entries and counts 
 * 	in the form:
 *		name1 count1
 *		name2 count2
 *		<etc>
 *	The names must all be unique, single-string character strings.
 *	The file should be writable by whatever user the web server runs as.
 *
 *      IMPORTANT: in order to do in-line replacements of the count field,
 *		   the numbers must have leading 0's.  Use enough leading
 *		   0's to make the number of size MAXNUMSIZE.
 *
 * Step 3:
 *	Compile this file with your favorite C compiler.
 *	(or your least favorite; I really don't care).
 *	The executable cgi script should have the extension ".xbm"
 *	for x-bitmap.
 *
 * Step 4:
 * 	In the html page that you want the counter to appear, place the
 *	following html command:
 * 		<img src=script_pathname?optional-directory+counter-name>.
 *
 *	For example, if the database file looked like:
 *	    ratner-homepage 00001234
 *	    john-homepage   00000008
 *	    ratner-cheerspage 00086511
 *	and the script lives in /cgi-bin,
 *      and the database lives in /cgi-bin, then the directory argument
 *	is not necessary, and the html command for ratner's homepage would be:
 *	    <img src=/cgi-bin/count.xbm?ratner-homepage>
 *
 *	If the database lived in /home/ratner/counter, then the html command is
 *	    <img src=/cgi-bin/count.xbm?/home/ratner/counter+ratner-homepage>
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/file.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

char *digits[] = 
      {"0xff","0xff","0xff","0xc3","0x99","0x99","0x99","0x99",
	   "0x99","0x99","0x99","0x99","0xc3","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0xcf","0xc7","0xcf","0xcf","0xcf",
	   "0xcf","0xcf","0xcf","0xcf","0xcf","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0xc3","0x99","0x9f","0x9f","0xcf",
	   "0xe7","0xf3","0xf9","0xf9","0x81","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0xc3","0x99","0x9f","0x9f","0xc7",
	   "0x9f","0x9f","0x9f","0x99","0xc3","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0xcf","0xcf","0xc7","0xc7","0xcb",
	   "0xcb","0xcd","0x81","0xcf","0x87","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0x81","0xf9","0xf9","0xf9","0xc1",
	   "0x9f","0x9f","0x9f","0x99","0xc3","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0xc7","0xf3","0xf9","0xf9","0xc1",
	   "0x99","0x99","0x99","0x99","0xc3","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0x81","0x99","0x9f","0x9f","0xcf",
	   "0xcf","0xe7","0xe7","0xf3","0xf3","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0xc3","0x99","0x99","0x99","0xc3",
	   "0x99","0x99","0x99","0x99","0xc3","0xff","0xff","0xff",
	   "0xff","0xff","0xff","0xc3","0x99","0x99","0x99","0x99",
	   "0x83","0x9f","0x9f","0xcf","0xe3","0xff","0xff","0xff"
	   };

/*
 * COUNT_FILE = name of the database file with counts
 * LOCK_FILE = global lock file used to enforce exclusive access to the
 *	       database count file
 * ERROR_LOG = where to write errors to
 * MAXNUMSIZE = number of digits
 * MAXLINESIZE = maximum line length in the database file
 * MAXWAITTIME = maximum # of times we loop waiting for the database file
 *		 to unlock.  This must be greater than 0.
 */

#define COUNT_FILE 	"count.txt" 
#define LOCK_FILE  	".count_lock"
#define ERROR_LOG	"error_log"
#define MAXNUMSIZE	8
#define MAXLINESIZE	256
#define MAXWAITTIME	50

/*
 * Take the number in num and
 * convert it into an 8-digit string with leading zeros.
 * Assumes there is enough space in str.
 */
void
makeIntoString(num, str)
    int num;
    char *str;
{
    int pos;

    /*
     * NEEDSWORK: this depends on MAXNUMSIZE
     */
    strcpy(str, "00000000");

    pos = MAXNUMSIZE-1;
    while (num > 0) {
	str[pos--] = '0' + (num % 10);
	num = num / 10;
    }
}

/*
 * Write an error to the error log
 */
void
writeError(errorStr)
    char *errorStr;
{
    FILE *fp;

    if ((fp = fopen(ERROR_LOG,"a")) != NULL) {
	fprintf(fp, "%s\n", errorStr);
	fclose(fp);
    }
}

/*
 * Read the file that holds the numeric counter value
 * Get the counter, bump it, and write it back.
 */ 
int
readAndWriteVal(name)
    char *name;		/* string we are looking for in the database file */
{
    FILE *fp;
    char line[MAXLINESIZE];
    char field[MAXLINESIZE];
    char numberString[MAXNUMSIZE];
    int num;
    int retval = 0;
    int waitTime = 0;

    /*
     * Open and lock file
     */
    while (waitTime++ < MAXWAITTIME && open(LOCK_FILE, O_CREAT | O_EXCL) == -1)
	;
    if (waitTime >= MAXWAITTIME) {
	writeError("timed out waiting for lock file to disappear");
	return 0;
    }

    if ((fp = fopen(COUNT_FILE,"r+")) == NULL) {
	unlink(LOCK_FILE);
	writeError("could not open count file");
	return 0;
    }

    /*
     * Scan the databse file, looking for a match on "name"
     */
    while (fgets(line, MAXLINESIZE, fp) != NULL) {
	sscanf(line, "%s %d", &field, &num);
	if (!strcmp(field, name)) {
	    /*
	     * We found the right entry
	     * Bump the count and rewrite the database file
	     */
	    retval = num;
	    fseek(fp, -strlen(line), SEEK_CUR);
	    makeIntoString(++num, numberString);
	    fprintf(fp, "%s %s", name, numberString);
	    break;
	}
    }

    /* 
     * Unlock and close file
     */
    fclose(fp);
    unlink(LOCK_FILE);
    return retval;
}


/*
 * Mainline
 *
 * command-line: count [directory] counter-name
 */
int
main(argc, argv)
    int argc;
    char **argv;

{
    int num;
    char numberString[MAXNUMSIZE];
    int row, col;	/* row and column for creating bitmap */

    /*
     * Check usage
     * Usage: script-name [optional directory] <name to look for in database>
     */
    switch (argc) {
    case 3:
	/*
	 * change directory to argv[1]
	 */
	if (chdir(*++argv) != 0) {
	    chdir("/tmp");
	    writeError("couldn't chdir to requested directory");
	}
	/* NOTE: explicit fall-through */
    case 2:
	/*
	 * Get, bump, and write back new value
	 */
	num = readAndWriteVal(*++argv);
	break;
    default:
	num = 0;
	writeError("incorrect number of arguments");
    }

    /*
     * Put the number into an 8 digit string.
     */
    makeIntoString(num, numberString);

    /*
     * Print out the bitmap
     */
    printf ("Content-type: image/x-xbitmap\n\n");
    printf ("#define count_width 64\n");
    printf ("#define count_height 16\n");
    printf ("static char count_bits[] = {\n");

    for (row = 0; row < 16; row++)
    {
	for (col = 0; col < 8; col++)
	{
	    num = (int)(numberString[col] - '0');
	    printf(digits[((num*16) + row)]);
	    if (col < 7) {
		printf(", ");
	    } 
	}
	printf((row == 15 ? "};" : ",\n"));
    }
    printf("\n");
    return 0;
}