From 13a10ce7af9dd794ca710d63cd071ab94ca940dc Mon Sep 17 00:00:00 2001
From: Alex Lyon <arcterus@mail.com>
Date: Thu, 25 Apr 2019 19:35:32 -0700
Subject: [PATCH] stdlib: implement rand_r() using XorShiftRng
---
src/header/stdlib/mod.rs | 18 +++++++++++++---
tests/expected/stdlib/rand.stdout | 4 ++++
tests/stdlib/rand.c | 36 +++++++++++++++++++++++++++++++
3 files changed, 55 insertions(+), 3 deletions(-)
diff --git a/src/header/stdlib/mod.rs b/src/header/stdlib/mod.rs
index 07125896..c69caa44 100644
--- a/src/header/stdlib/mod.rs
+++ b/src/header/stdlib/mod.rs
@@ -628,9 +628,21 @@ pub unsafe extern "C" fn rand() -> c_int {
}
}
-// #[no_mangle]
-pub extern "C" fn rand_r(seed: *mut c_uint) -> c_int {
- unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn rand_r(seed: *mut c_uint) -> c_int {
+ if seed.is_null() {
+ errno::EINVAL
+ } else {
+ // set the type explicitly so this will fail if the array size for XorShiftRng changes
+ let seed_arr: [u8; 16] = mem::transmute([*seed; 16 / mem::size_of::<c_uint>()]);
+
+ let mut rng = XorShiftRng::from_seed(seed_arr);
+ let ret = rng.gen_range(0, RAND_MAX);
+
+ *seed = ret as _;
+
+ ret
+ }
}
// #[no_mangle]
diff --git a/tests/expected/stdlib/rand.stdout b/tests/expected/stdlib/rand.stdout
index 60210f3e..4e35003b 100644
--- a/tests/expected/stdlib/rand.stdout
+++ b/tests/expected/stdlib/rand.stdout
@@ -2,3 +2,7 @@
201425341
201425341
67141780
+264204
+271585843
+264204
+271585843
diff --git a/tests/stdlib/rand.c b/tests/stdlib/rand.c
index 52908fae..29791888 100644
--- a/tests/stdlib/rand.c
+++ b/tests/stdlib/rand.c
@@ -31,4 +31,40 @@ int main(void) {
puts("srand(1) doesn't work");
exit(EXIT_FAILURE);
}
+
+ // Ensure rand_r() fails with NULL input
+ if (rand_r(NULL) != EINVAL) {
+ puts("rand_r(NULL) doesn't return EINVAL");
+ exit(EXIT_FAILURE);
+ }
+
+ // Ensure rand_r() produces unique values
+ int seed = 259;
+ int rand_r_seed259_1 = rand_r((unsigned *)&seed);
+ printf("%d\n", rand_r_seed259_1);
+
+ int rand_r_seed259_2 = rand_r((unsigned *)&seed);
+ printf("%d\n", rand_r_seed259_2);
+
+ if (rand_r_seed259_1 == rand_r_seed259_2) {
+ puts("rand_r() fails to produce unique values");
+ exit(EXIT_FAILURE);
+ }
+
+ // Ensure rand_r() returns reproducible values
+ seed = 259;
+ int rand_r_seed259_1_2 = rand_r((unsigned *)&seed);
+ printf("%d\n", rand_r_seed259_1_2);
+
+ int rand_r_seed259_2_2 = rand_r((unsigned *)&seed);
+ printf("%d\n", rand_r_seed259_2_2);
+
+ if (rand_r_seed259_1 != rand_r_seed259_1_2
+ || rand_r_seed259_2 != rand_r_seed259_2_2)
+ {
+ puts("rand_r() is not reproducible");
+ exit(EXIT_FAILURE);
+ }
+
+ return 0;
}
--
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