Initial commit

Makefile

@@ -0,0 +1,23 @@
+CC=gcc
+CFLAGS=-Wall
+LDFLAGS=-lm
+
+all: sadrand
+
+sadrand: sadrand.o
+	$(CC) -o $@ $< $(LDFLAGS)
+
+sadrand.o: sadrand.c
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+sadrand-dbg: sadrand-dbg.o
+	$(CC) -g -o $@ $< $(LDFLAGS)
+
+sadrand-dbg.o: sadrand.c
+	$(CC) -g $(CFLAGS) -c -o $@ $<
+
+
+.PHONY: clean
+
+clean:
+	-rm *.o

sadrand.c

@@ -0,0 +1,204 @@
+#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;
+};
+
+void usage(const char name[])
+{
+	dprintf(2, "Usage %s [resolution [iterations]]\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");
+	}
+}
+
+int main(int argc, char *argv[]) {
+	
+	char *foo;
+	unsigned char resolution = argc < 2 ? 100 : atoi(argv[1]);
+	unsigned long iterations = argc < 3 ? 0x100000 : strtoll(argv[2], NULL, 0);
+
+	if(!resolution || !iterations)
+	{
+		usage(argv[0]);
+		exit(0);
+	}
+
+	unsigned int *results[NTEST];
+
+	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]);
+
+	print_results(resolution, results);
+
+	for(int i=0; i<NTEST; i++)
+	{
+		free(results[i]);
+	}
+
+	return 0;
+}
+