initialize with /dev/urandom, not /dev/random; test randomness by trying to compress output

.gitlab-ci.yml

@@ -12,6 +12,7 @@ build:
   #   - apt update && apt -y install make
   script:
     - make
+    - make test
   artifacts:
     paths:
       - rand

Makefile

 CFLAGS=-O3
 LDFLAGS=-O3
 
+TESTFILES=test.bin test.gz test.bz test.xz
+
 all: rand
 rand: isaac64.o
 	$(CC) $(LDLAGS) -o $@ $<
 isaac64.o: isaac64.c
 clean:
-	rm -f *.o *~
+	rm -f *.o *~ $(TESTFILES)
 fclean: clean
 	rm -f rand
+
+test: rand
+	./rand | dd of=/dev/null bs=1M count=1000
+	./rand | dd of=test.bin bs=1M count=10
+	@gzip -9 < test.bin > test.gz
+	./checksize test.bin test.gz
+	@bzip2 -9 < test.bin > test.bz
+	./checksize test.bin test.bz
+	@xz -9 < test.bin > test.xz
+	./checksize test.bin test.xz
+	rm -f $(TESTFILES)

isaac64.c

@@ -76,9 +76,9 @@ word flag;
    aa=bb=cc=(ub8)0;
    a=b=c=d=e=f=g=h=0x9e3779b97f4a7c13LL;  /* the golden ratio */
 
-   _rand = fopen("/dev/random", "r");
+   _rand = fopen("/dev/urandom", "r");
    if (_rand == NULL) {
-     perror("Cannot open /dev/random: ");
+     perror("Cannot open /dev/urandom: ");
      exit(1);
    }
    fread(&a, sizeof(ub8), 1, _rand);