Merge pull request #102 from sajattack/rand

implement rand and srand using the rand crate

src/stdlib/Cargo.toml

@@ -12,3 +12,4 @@ platform = { path = "../platform" }
 ralloc = { path = "../../ralloc", default-features = false }
 ctype = { path = "../ctype" }
 errno = { path = "../errno" }
+rand = { git = "https://github.com/rust-lang-nursery/rand/", default-features = false }

src/stdlib/src/lib.rs

@@ -8,8 +8,10 @@ extern crate ctype;
 extern crate errno;
 extern crate platform;
 extern crate ralloc;
+extern crate rand;
 
 use core::{ptr, str};
+use rand::{Rng, SeedableRng, XorShiftRng};
 
 use errno::*;
 use platform::types::*;
@@ -19,8 +21,10 @@ static ALLOCATOR: ralloc::Allocator = ralloc::Allocator;
 
 pub const EXIT_FAILURE: c_int = 1;
 pub const EXIT_SUCCESS: c_int = 0;
+pub const RAND_MAX: c_int = 2147483647;
 
 static mut ATEXIT_FUNCS: [Option<extern "C" fn()>; 32] = [None; 32];
+static mut RNG: Option<XorShiftRng> = None;
 
 #[no_mangle]
 pub unsafe extern "C" fn a64l(s: *const c_char) -> c_long {
@@ -375,8 +379,16 @@ pub extern "C" fn qsort(
 }
 
 #[no_mangle]
-pub extern "C" fn rand() -> c_int {
-    unimplemented!();
+pub unsafe extern "C" fn rand() -> c_int {
+    match RNG {
+        Some(ref mut rng) => rng.gen_range::<c_int>(0, RAND_MAX),
+        None => {
+            let mut rng = XorShiftRng::from_seed([1; 16]);
+            let ret = rng.gen_range::<c_int>(0, RAND_MAX);
+            RNG = Some(rng);
+            ret
+        }
+    }
 }
 
 #[no_mangle]
@@ -425,8 +437,8 @@ pub extern "C" fn setstate(state: *const c_char) -> *mut c_char {
 }
 
 #[no_mangle]
-pub extern "C" fn srand(seed: c_uint) {
-    unimplemented!();
+pub unsafe extern "C" fn srand(seed: c_uint) {
+    RNG = Some(XorShiftRng::from_seed([seed as u8; 16]));
 }
 
 #[no_mangle]

tests/.gitignore

@@ -27,6 +27,7 @@
 /sprintf
 /stdlib/a64l
 /stdlib/bsearch
+/stdlib/rand
 /stdlib/strtol
 /string/strchr
 /string/strcspn

tests/Makefile

@@ -23,6 +23,7 @@ EXPECT_BINS=\
 	stdlib/bsearch \
 	stdlib/strtol \
 	stdlib/a64l \
+	stdlib/rand \
 	string/strncmp \
 	string/strcspn \
 	string/strchr \

tests/stdlib/rand.c

@@ -0,0 +1,8 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(int argc, char** argv) {
+    printf("%d\n", rand());
+    srand(259);
+    printf("%d\n", rand());
+}