Implement clock() and add CLOCK_* constants

src/time/src/constants.rs

@@ -42,3 +42,8 @@ pub(crate) const DAY_NAMES: [&str; 7] = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri
 pub(crate) const MON_NAMES: [&str; 12] = [
     "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
 ];
+
+pub(crate) const CLOCK_REALTIME: clockid_t = 0;
+pub(crate) const CLOCK_MONOTONIC: clockid_t = 1;
+pub(crate) const CLOCK_PROCESS_CPUTIME_ID: clockid_t = 2;
+pub(crate) const CLOCK_THREAD_CPUTIME_ID: clockid_t = 3;

src/time/src/lib.rs

@@ -12,7 +12,6 @@ mod helpers;
 use platform::types::*;
 use constants::*;
 use helpers::*;
-use core::fmt::write;
 use core::mem::transmute;
 use errno::EIO;
 
@@ -99,7 +98,23 @@ pub extern "C" fn asctime_r(tm: *const tm, buf: *mut c_char) -> *mut c_char {
 
 #[no_mangle]
 pub extern "C" fn clock() -> clock_t {
-    unimplemented!();
+    let mut ts: timespec;
+
+    unsafe {
+        ts = core::mem::uninitialized();
+    }
+
+    if clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &mut ts) != 0 {
+        return -1;
+    }
+
+    if ts.tv_sec > time_t::max_value() / 1000000
+        || ts.tv_nsec / 1000 > time_t::max_value() - 1000000 * ts.tv_sec
+    {
+        return -1;
+    }
+
+    return ts.tv_sec * 1_000_000 + ts.tv_nsec / 1000;
 }
 
 #[no_mangle]

tests/time.c

@@ -7,5 +7,7 @@ int main(int argc, char** argv) {
     perror("clock_gettime");
     time(NULL);
     perror("time");
+    clock_t c = clock();
+    perror("clock");
     return 0;
 }