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Appendix D

The ncSA imagemap.c Program


An imagemap is usually made up of regions, or hotspots, defined by polygons, circles, rectangles, and points. The imagemap program is responsible for matching the x,y coordinates of the mouse-click sent to it by the client, with the URI intended for those x,y coordinates. The imagemap.c program shown in Listing D.1 normally is distributed as part of the ncSA httpd Web server distribution. It is also available at

http://hoohoo.ncsa.uiuc.edu/docs/tutorials/imagemap.txt

Listing D.1. The imagemap.c program.

/*
** mapper 1.2
** 7/26/93 Kevin Hughes, kevinh@pulua.hcc.hawaii.edu
** "macmartinized" polygon code copyright 1992 by Eric Haines, erich@eye.com
** All suggestions, help, etc. gratefully accepted!
**
** 1.1: Better formatting, added better polygon code.
** 1.2: Changed isname(), added config file specification.
**
** 11/13/93: Rob McCool, robm@ncsa.uiuc.edu
**
** 1.3: Rewrote configuration stuff for ncSA /htbin script
**
** 12/05/93: Rob McCool, robm@ncsa.uiuc.edu
**
** 1.4: Made CGI/1.0 compliant.
**
** 06/27/94: Chris Hyams, cgh@rice.edu
**          Based on an idea by Rick Troth (troth@rice.edu)
**
** 1.5: Imagemap configuration file in PATH_INFO.  Backwards compatible.
**
**  Old-style lookup in imagemap table:
**    <a href="http://foo.edu/cgi-bin/imagemap/oldmap">
**
**  New-style specification of mapfile relative to DocumentRoot:
**    <a href="http://foo.edu/cgi-bin/imagemap/path/for/new.map">
**
**  New-style specification of mapfile in user's public HTML directory:
**    <a href="http://foo.edu/cgi-bin/imagemap/~username/path/for/new.map">
**
** 07/11/94: Craig Milo Rogers, Rogers@ISI.Edu
**
** 1.6: Added "point" datatype: the nearest point wins.  Overrides "default".
**
** 08/28/94: Carlos Varela, cvarela@ncsa.uiuc.edu
**
** 1.7: Fixed bug:  virtual URLs are now understood.
**       Better error reporting when not able to open configuration file.
**
** 03/07/95: Carlos Varela, cvarela@ncsa.uiuc.edu
**
** 1.8: Fixed bug (strcat->sprintf) when reporting error.
**       Included getline() function from util.c in ncSA httpd distribution.
**
*/

#include <stdio.h>
#include <string.h>
#if !defined(pyr) && !defined(NO_STDLIB_H)
#include <stdlib.h>
#else
#include <sys/types.h>
#include <ctype.h>
char *getenv();
#endif
#include <sys/types.h>
#include <sys/stat.h>

#define CONF_FILE "/usr/local/etc/httpd/conf/imagemap.conf"

#define MAXLINE 500
#define MAXVERTS 100
#define X 0
#define Y 1
#define LF 10
#define CR 13

int isname(char);

int main(int argc, char **argv)
{
    char input[MAXLINE], *mapname, def[MAXLINE], conf[MAXLINE], errstr[MAXLINE];
    double testpoint[2], pointarray[MAXVERTS][2];
    int i, j, k;
    FILE *fp;
    char *t;
    double dist, mindist;
    int sawpoint = 0;
    
    if (argc != 2)
        servererr("Wrong number of arguments, client may not support ISMAP.");
    mapname=getenv("PATH_INFO");

    if((!mapname) || (!mapname[0]))
        servererr("No map name given. Please read the <A HREF=\"http://
 hoohoo.ncsa.uiuc.edu/docs/setup/admin/Imagemap.html\">instructions</ A>.<P>"); mapname++; if(!(t = strchr(argv[1],','))) servererr("Your client doesn't support image mapping properly."); *t++ = '\0'; testpoint[X] = (double) atoi(argv[1]); testpoint[Y] = (double) atoi(t); /* * if the mapname contains a '/', it represents a unix path - * we get the translated path, and skip reading the configuration file. */ if (strchr(mapname,'/')) { strcpy(conf,getenv("PATH_TRANSLATED")); goto openconf; } if ((fp = fopen(CONF_FILE, "r")) == NULL){ sprintf(errstr, "Couldn't open configuration file: %s", CONF_FILE); servererr(errstr); } while(!(getline(input,MAXLINE,fp))) { char confname[MAXLINE]; if((input[0] == '#') || (!input[0])) continue; for(i=0;isname(input[i]) && (input[i] != ':');i++) confname[i] = input[i]; confname[i] = '\0'; if(!strcmp(confname,mapname)) goto found; } /* * if mapname was not found in the configuration file, it still * might represent a file in the server root directory - * we get the translated path, and check to see if a file of that * name exists, jumping to the opening of the map file if it does. */ if(feof(fp)) { struct stat sbuf; strcpy(conf,getenv("PATH_TRANSLATED")); if (!stat(conf,&sbuf) && ((sbuf.st_mode & S_IFMT) == S_IFREG)) goto openconf; else servererr("Map not found in configuration file."); } found: fclose(fp); while(isspace(input[i]) || input[i] == ':') ++i; for(j=0;input[i] && isname(input[i]);++i,++j) conf[j] = input[i]; conf[j] = '\0'; openconf: if(!(fp=fopen(conf,"r"))){ sprintf(errstr, "Couldn't open configuration file: %s", conf); servererr(errstr); } while(!(getline(input,MAXLINE,fp))) { char type[MAXLINE]; char url[MAXLINE]; char num[10]; if((input[0] == '#') || (!input[0])) continue; type[0] = '\0';url[0] = '\0'; for(i=0;isname(input[i]) && (input[i]);i++) type[i] = input[i]; type[i] = '\0'; while(isspace(input[i])) ++i; for(j=0;input[i] && isname(input[i]);++i,++j) url[j] = input[i]; url[j] = '\0'; if(!strcmp(type,"default") && !sawpoint) { strcpy(def,url); continue; } k=0; while (input[i]) { while (isspace(input[i]) || input[i] == ',') i++; j = 0; while (isdigit(input[i])) num[j++] = input[i++]; num[j] = '\0'; if (num[0] != '\0') pointarray[k][X] = (double) atoi(num); else break; while (isspace(input[i]) || input[i] == ',') i++; j = 0; while (isdigit(input[i])) num[j++] = input[i++]; num[j] = '\0'; if (num[0] != '\0') pointarray[k++][Y] = (double) atoi(num); else { fclose(fp); servererr("Missing y value."); } } pointarray[k][X] = -1; if(!strcmp(type,"poly")) if(pointinpoly(testpoint,pointarray)) sendmesg(url); if(!strcmp(type,"circle")) if(pointincircle(testpoint,pointarray)) sendmesg(url); if(!strcmp(type,"rect")) if(pointinrect(testpoint,pointarray)) sendmesg(url); if(!strcmp(type,"point")) { /* Don't need to take square root. */ dist = ((testpoint[X] - pointarray[0][X]) * (testpoint[X] - pointarray[0][X])) + ((testpoint[Y] - pointarray[0][Y]) * (testpoint[Y] - pointarray[0][Y])); /* If this is the first point, or the nearest, set the default. */ if ((! sawpoint) || (dist < mindist)) { mindist = dist; strcpy(def,url); } sawpoint++; } } if(def[0]) sendmesg(def); servererr("No default specified."); } sendmesg(char *url) { if (strchr(url, ':')) /*** It is a full URL ***/ printf("Location: "); else /*** It is a virtual URL ***/ printf("Location: http://%s:%s", getenv("SERVER_NAME"), getenv("SERVER_PORT")); printf("%s%c%c",url,10,10); printf("This document has moved <A HREF=\"%s\">here</A>%c",url,10); exit(1); } int pointinrect(double point[2], double coords[MAXVERTS][2]) { return ((point[X] >= coords[0][X] && point[X] <= coords[1][X]) && (point[Y] >= coords[0][Y] && point[Y] <= coords[1][Y])); } int pointincircle(double point[2], double coords[MAXVERTS][2]) { int radius1, radius2; radius1 = ((coords[0][Y] - coords[1][Y]) * (coords[0][Y] - coords[1][Y])) + ((coords[0][X] - coords[1][X]) * (coords[0][X] - coords[1][X])); radius2 = ((coords[0][Y] - point[Y]) * (coords[0][Y] - point[Y])) + ((coords[0][X] - point[X]) * (coords[0][X] - point[X])); return (radius2 <= radius1); } int pointinpoly(double point[2], double pgon[MAXVERTS][2]) { int i, numverts, inside_flag, xflag0; int crossings; double *p, *stop; double tx, ty, y; for (i = 0; pgon[i][X] != -1 && i < MAXVERTS; i++) ; numverts = i; crossings = 0; tx = point[X]; ty = point[Y]; y = pgon[numverts - 1][Y]; p = (double *) pgon + 1; if ((y >= ty) != (*p >= ty)) { if ((xflag0 = (pgon[numverts - 1][X] >= tx)) == (*(double *) pgon >= tx)) { if (xflag0) crossings++; } else { crossings += (pgon[numverts - 1][X] - (y - ty) * (*(double *) pgon - pgon[numverts - 1][X]) / (*p - y)) >= tx; } } stop = pgon[numverts]; for (y = *p, p += 2; p < stop; y = *p, p += 2) { if (y >= ty) { while ((p < stop) && (*p >= ty)) p += 2; if (p >= stop) break; if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx)) { if (xflag0) crossings++; } else { crossings += (*(p - 3) - (*(p - 2) - ty) * (*(p - 1) - *(p - 3)) / (*p - *(p - 2))) >= tx; } } else { while ((p < stop) && (*p < ty)) p += 2; if (p >= stop) break; if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx)) { if (xflag0) crossings++; } else { crossings += (*(p - 3) - (*(p - 2) - ty) * (*(p - 1) - *(p - 3)) / (*p - *(p - 2))) >= tx; } } } inside_flag = crossings & 0x01; return (inside_flag); } servererr(char *msg) { printf("Content-type: text/html%c%c",10,10); printf("<title>Mapping Server Error</title>"); printf("<h1>Mapping Server Error</h1>"); printf("This server encountered an error:<p>"); printf("%s", msg); exit(-1); } int isname(char c) { return (!isspace(c)); } int getline(char *s, int n, FILE *f) { register int i=0; while(1) { s[i] = (char)fgetc(f); if(s[i] == CR) s[i] = fgetc(f); if((s[i] == 0x4) || (s[i] == LF) || (i == (n-1))) { s[i] = '\0'; return (feof(f) ? 1: 0); } ++i; } }