sadrand-c/sadrand.c

#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/random.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#define NTEST 3

struct rand_ctx
{
	unsigned char buf[4096];
	int cur_read;
};

static struct option long_opts[] = {
	{"iter", required_argument, 0, 'i'},
	{"resolution", required_argument, 0, 'r'},
	{"relative", no_argument, 0, 'R'},
	{"help", no_argument, 0, 'h'},
	{0, 0, 0, 0}
};

void usage(const char name[])
{
	dprintf(2, "Usage %s [-i ITER] [-r RESOLUTION] [-R]\n\
\t-i, --iter       Iteration count\n\
\t-r, --resolution Number of dice faces\n\
\t-R, --relative   Output relative count instead of absolute\n\
\t-h, --help       Display this help and exit\n", name);
}

void rand_ctx_init(struct rand_ctx *ctx)
{
	ctx->cur_read = -1;
}

int randbits(char count, unsigned long *bits, struct rand_ctx *ctx)
{
	int ret;

	*bits = 0;

	if(count < 0 || count > 8*sizeof(unsigned long))
	{
		return -1;
	}

	if(sizeof(ctx->buf) - ctx->cur_read < (count/8)+1)
	{
		ctx->cur_read = -1;
	}
	if(ctx->cur_read < 0)
	{
		while(1)
		{
			ret = getrandom(ctx->buf, sizeof(ctx->buf), 0);
			if(ret < 0) {
				if(errno == EINTR) { continue; }
				perror("Unable to get random bytes");
				return -2;
			}
			break;
		}
		ctx->cur_read = 0;
	}

	do {
		if(count < 8)
		{
			*bits <<= count;
			*bits |= ctx->buf[ctx->cur_read] & ((1<<count)-1);
			count = 0;
		}
		else
		{
			*bits <<= 8;
			*bits |= ctx->buf[ctx->cur_read];
			count -= 8;
		}
		ctx->cur_read++;
	}while(count);

	return 0;
}

int std_rand(unsigned long iterations, unsigned char resolution, unsigned int *result)
{	
	unsigned long bits;
	struct rand_ctx ctx;
	char nbits;

	nbits = (char)ceilf(log2f(resolution));

	rand_ctx_init(&ctx);

	for(unsigned long i = 0; i<iterations; i++)
	{
		do
		{
			if(randbits(nbits, &bits, &ctx) < 0) {
				perror("Unable to get random bits");
				return -1;
			}
		}while(bits > resolution-1);
		result[bits]++;
	}

	return 0;
}

int mod_rand(unsigned long iterations, unsigned char resolution, unsigned int *result)
{
	unsigned long bits;

	struct rand_ctx ctx;

	rand_ctx_init(&ctx);

	for(unsigned long i = 0; i<iterations; i++)
	{
		if(randbits(8, &bits, &ctx) < 0) {
			perror("Unable to get random bits");
			return -1;
		}
		result[bits%resolution]++;
	}
	return 0;
}

int prop_rand(unsigned long iterations, unsigned char resolution, unsigned int *result)
{
	unsigned long bits;

	struct rand_ctx ctx;

	rand_ctx_init(&ctx);

	for(unsigned long i = 0; i<iterations; i++)
	{
		if(randbits(8, &bits, &ctx) < 0)
		{
			perror("Unable to get random bits");
			return -1;
		}
		result[(bits * resolution) / 256]++;
	}
	return 0;
}

void print_result(unsigned char resolution, unsigned int *result)
{
	printf("[");
	for(int i=0; i<resolution; i++)
	{
		printf("%d%s", result[i], i<resolution-1?", ":"");
	}
	printf("]\n");
}

void print_results(unsigned char resolution, unsigned int *results[NTEST])
{
	for(int i=0; i<resolution; i++)
	{
		printf("%d %d ", resolution, i);
		for(int j=0; j<NTEST; j++)
		{
			printf("%d ", results[j][i]);
		}
		printf("\n");
	}
}

void print_results_rel(unsigned char resolution, unsigned long iterations,
	unsigned int *results[NTEST])
{
	long double res;
	for(int i=0; i<resolution; i++)
	{
		printf("%d %f ", resolution, (double)i / resolution);
		for(int j=0; j<NTEST; j++)
		{
			res = (results[j][i] * resolution);
			res /= iterations;
			printf("%Lf ", res);
		}
		printf("\n");
	}
}

int main(int argc, char *argv[]) {
	
	unsigned char resolution;
	unsigned long iterations;
	short relative;
	long long tmp_ll;
	unsigned int *results[NTEST];

	relative = 0;
	iterations = 0x1000;
	resolution = 100;

	while (1)
	{
		int c;
		int option_index = 0;
		char *arg_endp;

		c = getopt_long(argc, argv, "i:r:Rh",
			long_opts, &option_index);
		if(c == -1) { break; }
		switch(c) 
		{
		case 'i':
			tmp_ll = strtoll(optarg, &arg_endp, 0);
			if (*arg_endp != '\0' || optarg == arg_endp)
			{
				dprintf(2, "Unable to parse iteration count '%s' invalid from '%s'\n", optarg, arg_endp);
				usage(argv[0]);
				exit(1);
			}
			if(tmp_ll <= 0)
			{
				dprintf(2, "Invalid iteration count %lld\n",
					tmp_ll);
				usage(argv[0]);
				exit(1);
			}
			iterations = tmp_ll;
			break;
		case 'r':
			tmp_ll = strtoll(optarg, &arg_endp, 0);
			if (*arg_endp != '\0' || optarg == arg_endp)
			{
				dprintf(2, "Unable to parse resolution '%s' invalid from '%s'\n", optarg, arg_endp);
				usage(argv[0]);
				exit(1);
			}
			if(tmp_ll <= 0)
			{
				dprintf(2, "Invalid resolution %lld\n",
					tmp_ll);
				usage(argv[0]);
				exit(1);
			}
			else if(tmp_ll > 255)
			{
				dprintf(2, "Too big resolution %lld (max 255)\n",
					tmp_ll);
				usage(argv[0]);
				exit(1);
			}
			resolution = tmp_ll;
			break;
		case 'R':
			relative = 1;
			break;
		case 'h':
			usage(argv[0]);
			exit(0);
		case '?':
			break;
		}
	}
	if(optind < argc)
	{
		dprintf(2, "Invalid arguments : ");
		for(int i=optind; i<argc; i++)
		{
			dprintf(2, "'%s' ", argv[i]);
		}
		dprintf(2, "\n");
		usage(argv[0]);
		exit(1);
	}

	if(relative)
	{
		iterations = iterations * resolution;
	}

	for(int i=0; i<NTEST; i++)
	{
		if( !(results[i] = malloc(sizeof(unsigned int) * resolution)) )
		{
			perror("Unable to allocate results array");
			return 1;
		}
		bzero(results[i], sizeof(unsigned int)*resolution);
	}

	std_rand(iterations, resolution, results[0]);
	mod_rand(iterations, resolution, results[1]);
	prop_rand(iterations, resolution, results[2]);

	if(relative)
	{
		print_results_rel(resolution, iterations, results);
	}
	else
	{
		print_results(resolution, results);
	}

	for(int i=0; i<NTEST; i++)
	{
		free(results[i]);
	}

	return 0;
}