/* 
 * Title: 	Slowpipe.C
 * 
 * Description: Bandwidth restriction for UNIX pipes
 *
 * This software may be freely redistrubuted providing this comment remains 
 * unchanged.
 *
 * Author: 	Iain W. Bird, http://www.birdsoft.demon.co.uk
 *		wes@birdsoft.demon.co.uk
 */

#include <sys/time.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

main(int argc, char **argv)
{
	FILE *fd;
	char c;
	char *buffer;
	int bufsiz = 16;
	int i;
	int sleep = 0;
	int full = 0;
	struct timeval tval;
	double kps = 2.0,bps,pps;
	unsigned long t_s, t_us;

	if(argc != 2)
	{
		perror("Usage slowpipe <K per second e.g. 6.0>");
		exit(1);
	}

	sscanf(argv[1],"%lg",&kps);

	if ( kps > 10.0 )
	{
		bufsiz = 1024;
	}
	else if ( kps > 5.0 )
	{
		bufsiz = 512;
	}
	else if ( kps > 2.0 )
	{
		bufsiz = 256;
	}
	else if ( kps > 1.0 )
	{
		bufsiz = 128;
	}
	else if ( kps > 0.5 )
	{
		bufsiz = 64;
	}
	bps = 1024.0 * kps;
	pps = bps / bufsiz;

	if(pps > 1.0)
	{
		t_s = 0.0;
		t_us= 1.0e6 / pps;
	}
	else
	{
		t_s = 1.0 / pps;
		t_us = 0;
	}
	fprintf(stderr,"%6.2g K per second, bufsiz = %d\n",kps,bufsiz); 

	buffer = malloc(bufsiz);
	if(!buffer)
	{
		perror("Unable to allocate buffer");
		exit(1);
	}


	i = 0;
	while (1)
	{
		if (!full)
		{
			if(i < bufsiz)
			{
				buffer[i] = fgetc(stdin);
				if(feof(stdin))
				{
					fwrite(buffer,1,i,stdout);
					break;
				}
				if(++i == bufsiz)
				{
					full = !0;
				}
			}
		}
		else
		{
			/* go for a blocking select since the buffer is full */
			tval.tv_sec = t_s;
			tval.tv_usec = t_us;
			select ( 0, 0, 0, 0, &tval );
			fwrite(buffer,1,bufsiz,stdout);
			full = 0;
			i = 0;
		}
	}
	free(buffer);
}