1  // Copyright 2010 The Go Authors. All rights reserved.
       2  // Use of this source code is governed by a BSD-style
       3  // license that can be found in the LICENSE file.
       4  
       5  #include <assert.h>
       6  #include "life.h"
       7  #include "_cgo_export.h"
       8  
       9  const int MYCONST = 0;
      10  
      11  // Do the actual manipulation of the life board in C.  This could be
      12  // done easily in Go, we are just using C for demonstration
      13  // purposes.
      14  void
      15  Step(int x, int y, int *a, int *n)
      16  {
      17  	struct GoStart_return r;
      18  
      19  	// Use Go to start 4 goroutines each of which handles 1/4 of the
      20  	// board.
      21  	r = GoStart(0, x, y, 0, x / 2, 0, y / 2, a, n);
      22  	assert(r.r0 == 0 && r.r1 == 100);	// test multiple returns
      23  	r = GoStart(1, x, y, x / 2, x, 0, y / 2, a, n);
      24  	assert(r.r0 == 1 && r.r1 == 101);	// test multiple returns
      25  	GoStart(2, x, y, 0, x / 2, y / 2, y, a, n);
      26  	GoStart(3, x, y, x / 2, x, y / 2, y, a, n);
      27  	GoWait(0);
      28  	GoWait(1);
      29  	GoWait(2);
      30  	GoWait(3);
      31  }
      32  
      33  // The actual computation.  This is called in parallel.
      34  void
      35  DoStep(int xdim, int ydim, int xstart, int xend, int ystart, int yend, int *a, int *n)
      36  {
      37  	int x, y, c, i, j;
      38  
      39  	for(x = xstart; x < xend; x++) {
      40  		for(y = ystart; y < yend; y++) {
      41  			c = 0;
      42  			for(i = -1; i <= 1; i++) {
      43  				for(j = -1; j <= 1; j++) {
      44  				  if(x+i >= 0 && x+i < xdim &&
      45  					y+j >= 0 && y+j < ydim &&
      46  					(i != 0 || j != 0))
      47  				    c += a[(x+i)*xdim + (y+j)] != 0;
      48  				}
      49  			}
      50  			if(c == 3 || (c == 2 && a[x*xdim + y] != 0))
      51  				n[x*xdim + y] = 1;
      52  			else
      53  				n[x*xdim + y] = 0;
      54  		}
      55  	}
      56  }