Put timespec convert into common fn

src/header/pthread/mutex.rs

@@ -2,7 +2,10 @@ use super::*;
 
 use crate::{
     error::Errno,
-    header::errno::{EINVAL, ENOMEM, ETIMEDOUT},
+    header::{
+        errno::{EINVAL, ENOMEM, ETIMEDOUT},
+        time::{CLOCK_MONOTONIC, CLOCK_REALTIME, timespec_realtime_to_monotonic},
+    },
 };
 
 // PTHREAD_MUTEX_INITIALIZER is defined in bits_pthread/cbindgen.toml
@@ -77,24 +80,14 @@ pub unsafe extern "C" fn pthread_mutex_timedlock(
     mutex: *mut pthread_mutex_t,
     abstime: *const timespec,
 ) -> c_int {
-    // convert REALTIME_CLOCK to MONOTONIC_CLOCK
-
-    let relative = {
-        let mut realtime = timespec::default();
-        unsafe { clock_gettime(CLOCK_REALTIME, &mut realtime) };
-        let mut monotonic = timespec::default();
-        unsafe { clock_gettime(CLOCK_MONOTONIC, &mut monotonic) };
-        let Some(delta) = timespec::subtract(*abstime.clone(), realtime) else {
-            return e(Err(Errno(ETIMEDOUT)));
-        };
-        let Some(relative) = timespec::add(monotonic, delta) else {
-            return e(Err(Errno(ENOMEM)));
-        };
-        relative
+    let relative = match timespec_realtime_to_monotonic(*abstime) {
+        Ok(relative) => relative,
+        Err(err) => return e(Err(err)),
     };
 
     e((&*mutex.cast::<RlctMutex>()).lock_with_timeout(&relative))
 }
+
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn pthread_mutex_trylock(mutex: *mut pthread_mutex_t) -> c_int {
     e((&*mutex.cast::<RlctMutex>()).try_lock())