Implement random() and friends

tests/stdlib/random.c

@@ -0,0 +1,100 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "test_helpers.h"
+
+/* The output of these tests are checked against that from musl. Other
+ * algorithms may yield different results and still comply with the
+ * POSIX requirements. */
+
+int main(void) {
+    /* Should be enough to exercise the rollover branching in random()
+     * for all possible state array sizes (up to 256 bytes, i.e. 64
+     * 32-bit values). */
+    size_t test_seq_len = 70;
+
+    long random_result;
+
+    // Should give same result as with seed 1
+    puts("Uninitialized:");
+    for (size_t i = 0; i < test_seq_len; i++) {
+        random_result = random();
+        printf("%ld\n", random_result);
+    }
+
+    puts("\nSeed 1:");
+    srandom(1);
+    for (size_t i = 0; i < test_seq_len; i++) {
+        random_result = random();
+        printf("%ld\n", random_result);
+    }
+
+    puts("\nSeed 1337:");
+    srandom(1337);
+    for (size_t i = 0; i < test_seq_len; i++) {
+        random_result = random();
+        printf("%ld\n", random_result);
+    }
+
+    /* 256 bytes (as below) is the largest possible amount of state
+     * data. Created as a uint32_t to avoid possible alignment issues
+     * with char. */
+    uint32_t new_state[64] = {
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+    };
+
+    unsigned int seed = 42;
+
+    // Should exercise the different branches in initstate()
+    size_t sizes[] = {8, 31, 32, 63, 64, 127, 128, 255, 256};
+
+    for (size_t j = 0; j < sizeof(sizes)/sizeof(size_t); j++) {
+        size_t size = sizes[j];
+        printf("\nSeed %d, size %ld:\n", seed, size);
+        initstate(seed, (char *)new_state, size);
+
+        for (size_t i = 0; i < test_seq_len; i++) {
+            random_result = random();
+            printf("%ld\n", random_result);
+        }
+    }
+
+    /* Test that setstate() allows the use of a different state array,
+     * and that it correctly returns the old value. */
+    uint32_t other_new_state[64] = {
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+    };
+
+    initstate(seed, (char *)other_new_state, 32);
+    printf("\nSeed %d, other state array:\n", seed);
+    for (size_t i = 0; i < test_seq_len; i++) {
+        random_result = random();
+        printf("%ld\n", random_result);
+    }
+
+    char *should_be_other_new_state_ptr = setstate((char *)new_state);
+    if (should_be_other_new_state_ptr == (char *)other_new_state) {
+        puts("\nState data pointer restored correctly by setstate().");
+    }
+    else {
+        puts("\nState data pointer NOT restored correctly by setstate().");
+    }
+    printf("\nSeed %d, back to first state array:\n", seed);
+    for (size_t i = 0; i < test_seq_len; i++) {
+        random_result = random();
+        printf("%ld\n", random_result);
+    }
+
+    // Should yield NULL
+    char *state_with_size_less_than_8 = initstate(seed, (char *)new_state, 7);
+    printf("\nPointer returned by initstate with size < 8: %p\n",
+        state_with_size_less_than_8);
+
+    return 0;
+}