input.c

source code to compute the visibility polygon of a point in a polygon.

/* Brian O'Connor
 * 
 * input.c: file to encapsulate file input routines.
 */

#include <stdio.h>
#include <assert.h>
#include "input.h"
#include "pursuer.h"
#include "cell.h"

static FILE *OpenInputFile(char *filename);
static Obstacle *ReadOneObstacle(FILE *file);
static void ReadObstacles(FILE *file, WorldInfo *wInfo);

void ReadInputFile( char *filename, WorldInfo *wInfo )
{
	int ch, i;
	FILE *file;
	if( (file = OpenInputFile(filename)) == NULL) return;

	wInfo->obs = new (Obstacle *)[MAX_OBS]; 
	assert(wInfo->obs != NULL);
	
	wInfo->border = NULL;
	wInfo->robot = NULL;
	wInfo->nObs = 0;
	ch ='0';
	while( ch != EOF ) {
	   if( (ch = getc(file)) == 'O' ) {
                while( (ch = getc(file)) != '\n');		
		ReadObstacles(file, wInfo);
           } else if( ch == 'B' ) {
                while( (ch = getc(file)) != '\n');		
	        wInfo->border = ReadOneObstacle(file);
	   } else if( ch == 'R' ) {
	     /* read in a robot as if it was an obstacle */
	        while( (ch = getc(file)) != '\n');
		wInfo->robot = ReadOneObstacle(file);
	   }
        }
}


/* for now, this function is making the simplifying assumption that 
 * all obstacles occur sequentially and at the start of the file. */
/* assumed format: #vertexes
 *	           x1 y1
 * 		   x2 y2     etc.... */

static Obstacle *ReadOneObstacle(FILE *file)
{
	int i;
	char buffer[160];
	float x, y;
	Obstacle *ob;

	ob = new Obstacle;

	/* how many points do we have?*/
	fgets(buffer, 80, file);
	sscanf(buffer, "%d", &(ob->nPts));
	ob->pts = new Point[ob->nPts]; 
	assert(ob->pts != NULL);
	
	for( i = 0; i < ob->nPts; i++ ) {
		fgets(buffer, 80, file);
		sscanf(buffer, "%f %f", &x, &y);
		ob->pts[i].x = x; 
		ob->pts[i].y = y;
		ob->pts[i].w = 1;
	/*	printf("point: %f, %f\n", ob->pts[i].x, ob->pts[i].y); */
	}


	return(ob);
}

static FILE *OpenInputFile(char *filename)
{
	FILE *newfile;
	newfile = fopen(filename, "r");
	if( newfile == NULL ) {
		printf("Input file %s does not exist\n", filename);
		exit(0);
	}
	return( newfile );
}

static void ReadObstacles(FILE *file, WorldInfo *wInfo)
{
  int i = 0;
  char ch;

  while( (ch = getc(file)) != EOF && ch != '\n') {
    ungetc(ch, file);
    wInfo->obs[i++] = ReadOneObstacle(file);
    assert( i < MAX_OBS);
  }
  wInfo->nObs = i;

}