treat libc::time_t as a PassByValue

lib/src/annotation.rs

@@ -1,14 +1,13 @@
 use crate::traits::*;
 use crate::types::*;
-use chrono::prelude::*;
 use taskchampion::Annotation;
 
 /// TCAnnotation contains the details of an annotation.
 #[repr(C)]
 pub struct TCAnnotation {
-    /// Time the annotation was made, as a UNIX epoch timestamp
+    /// Time the annotation was made.  Must be nonzero.
-    pub entry: i64,
+    pub entry: libc::time_t,
-    /// Content of the annotation
+    /// Content of the annotation.  Must not be NULL.
     pub description: *mut TCString<'static>,
 }
 
@@ -16,13 +15,16 @@ impl PassByValue for TCAnnotation {
     type RustType = Annotation;
 
     unsafe fn from_ctype(self) -> Annotation {
-        let entry = Utc.timestamp(self.entry, 0);
+        // SAFETY:
+        //  - any time_t value is valid
+        //  - time_t is not zero, so unwrap is safe (see type docstring)
+        let entry = unsafe { self.entry.from_ctype() }.unwrap();
         // SAFETY:
         //  - self is owned, so we can take ownership of this TCString
-        //  - self.description was created from a String so has valid UTF-8
+        //  - self.description is a valid, non-null TCString (see type docstring)
-        //  - caller did not change it (promised by caller)
         let description = unsafe { TCString::take_from_arg(self.description) }
             .into_string()
+            // TODO: might not be valid utf-8
             .unwrap();
         Annotation { entry, description }
     }
@@ -30,7 +32,7 @@ impl PassByValue for TCAnnotation {
     fn as_ctype(arg: Annotation) -> Self {
         let description: TCString = arg.description.into();
         TCAnnotation {
-            entry: arg.entry.timestamp(),
+            entry: libc::time_t::as_ctype(Some(arg.entry)),
             // SAFETY: caller will later free this value via tc_annotation_free
             description: unsafe { description.return_val() },
         }
@@ -40,7 +42,7 @@ impl PassByValue for TCAnnotation {
 impl Default for TCAnnotation {
     fn default() -> Self {
         TCAnnotation {
-            entry: 0,
+            entry: 0 as libc::time_t,
             description: std::ptr::null_mut(),
         }
     }

lib/src/atomic.rs

@@ -1,6 +1,7 @@
 //! Trait implementations for a few atomic types
 
 use crate::traits::*;
+use chrono::prelude::*;
 
 impl PassByValue for usize {
     type RustType = usize;
@@ -13,3 +14,21 @@ impl PassByValue for usize {
         arg
     }
 }
+
+/// Convert an Option<DateTime<Utc>> to a libc::time_t, or zero if not set.
+impl PassByValue for libc::time_t {
+    type RustType = Option<DateTime<Utc>>;
+
+    unsafe fn from_ctype(self) -> Option<DateTime<Utc>> {
+        if self == 0 {
+            None
+        } else {
+            Some(Utc.timestamp(self as i64, 0))
+        }
+    }
+
+    fn as_ctype(arg: Option<DateTime<Utc>>) -> libc::time_t {
+        arg.map(|ts| ts.timestamp() as libc::time_t)
+            .unwrap_or(0 as libc::time_t)
+    }
+}

lib/src/task.rs

@@ -1,7 +1,7 @@
 use crate::traits::*;
 use crate::types::*;
 use crate::util::err_to_tcstring;
-use chrono::{DateTime, TimeZone, Utc};
+use chrono::{TimeZone, Utc};
 use std::convert::TryFrom;
 use std::ops::Deref;
 use std::ptr::NonNull;
@@ -155,22 +155,6 @@ impl TryFrom<TCString<'_>> for Tag {
     }
 }
 
-/// Convert a DateTime<Utc> to a libc::time_t, or zero if not set.
-fn to_time_t(timestamp: Option<DateTime<Utc>>) -> libc::time_t {
-    timestamp
-        .map(|ts| ts.timestamp() as libc::time_t)
-        .unwrap_or(0 as libc::time_t)
-}
-
-/// Convert a libc::time_t to Option<DateTime<Utc>>, treating time zero as None
-fn to_datetime(time: libc::time_t) -> Option<DateTime<Utc>> {
-    if time == 0 {
-        None
-    } else {
-        Some(Utc.timestamp(time as i64, 0))
-    }
-}
-
 /// TCTaskList represents a list of tasks.
 ///
 /// The content of this struct must be treated as read-only.
@@ -275,19 +259,19 @@ pub unsafe extern "C" fn tc_task_get_description<'a>(task: *mut TCTask) -> *mut
 /// Get the entry timestamp for a task (when it was created), or 0 if not set.
 #[no_mangle]
 pub unsafe extern "C" fn tc_task_get_entry<'a>(task: *mut TCTask) -> libc::time_t {
-    wrap(task, |task| to_time_t(task.get_entry()))
+    wrap(task, |task| libc::time_t::as_ctype(task.get_entry()))
 }
 
 /// Get the wait timestamp for a task, or 0 if not set.
 #[no_mangle]
 pub unsafe extern "C" fn tc_task_get_wait<'a>(task: *mut TCTask) -> libc::time_t {
-    wrap(task, |task| to_time_t(task.get_wait()))
+    wrap(task, |task| libc::time_t::as_ctype(task.get_wait()))
 }
 
 /// Get the modified timestamp for a task, or 0 if not set.
 #[no_mangle]
 pub unsafe extern "C" fn tc_task_get_modified<'a>(task: *mut TCTask) -> libc::time_t {
-    wrap(task, |task| to_time_t(task.get_modified()))
+    wrap(task, |task| libc::time_t::as_ctype(task.get_modified()))
 }
 
 /// Check if a task is waiting.
@@ -396,7 +380,8 @@ pub unsafe extern "C" fn tc_task_set_entry(task: *mut TCTask, entry: libc::time_
     wrap_mut(
         task,
         |task| {
-            task.set_entry(to_datetime(entry))?;
+            // SAFETY: any time_t value is a valid timestamp
+            task.set_entry(unsafe { entry.from_ctype() })?;
             Ok(TCResult::Ok)
         },
         TCResult::Error,
@@ -409,7 +394,8 @@ pub unsafe extern "C" fn tc_task_set_wait(task: *mut TCTask, wait: libc::time_t)
     wrap_mut(
         task,
         |task| {
-            task.set_wait(to_datetime(wait))?;
+            // SAFETY: any time_t value is a valid timestamp
+            task.set_wait(unsafe { wait.from_ctype() })?;
             Ok(TCResult::Ok)
         },
         TCResult::Error,
@@ -426,7 +412,9 @@ pub unsafe extern "C" fn tc_task_set_modified(
         task,
         |task| {
             task.set_modified(
-                to_datetime(modified).ok_or_else(|| anyhow::anyhow!("modified cannot be zero"))?,
+                // SAFETY: any time_t value is a valid timestamp
+                unsafe { modified.from_ctype() }
+                    .ok_or_else(|| anyhow::anyhow!("modified cannot be zero"))?,
             )?;
             Ok(TCResult::Ok)
         },

lib/taskchampion.h

@@ -122,11 +122,11 @@ typedef struct TCTask TCTask;
  */
 typedef struct TCAnnotation {
   /**
-   * Time the annotation was made, as a UNIX epoch timestamp
+   * Time the annotation was made.  Must be nonzero.
    */
-  int64_t entry;
+  time_t entry;
   /**
-   * Content of the annotation
+   * Content of the annotation.  Must not be NULL.
    */
   struct TCString *description;
 } TCAnnotation;