move contents of taskchampion repo to tc/

rust/lib/src/kv.rs

@@ -0,0 +1,115 @@
+use crate::traits::*;
+use crate::types::*;
+
+/// TCKV contains a key/value pair that is part of a task.
+///
+/// Neither key nor value are ever NULL.  They remain owned by the TCKV and
+/// will be freed when it is freed with tc_kv_list_free.
+#[repr(C)]
+pub struct TCKV {
+    pub key: TCString,
+    pub value: TCString,
+}
+
+impl PassByValue for TCKV {
+    type RustType = (RustString<'static>, RustString<'static>);
+
+    unsafe fn from_ctype(self) -> Self::RustType {
+        // SAFETY:
+        //  - self.key is not NULL (field docstring)
+        //  - self.key came from return_ptr in as_ctype
+        //  - self is owned, so we can take ownership of this TCString
+        let key = unsafe { TCString::val_from_arg(self.key) };
+        // SAFETY: (same)
+        let value = unsafe { TCString::val_from_arg(self.value) };
+        (key, value)
+    }
+
+    fn as_ctype((key, value): Self::RustType) -> Self {
+        TCKV {
+            // SAFETY:
+            //  - ownership of the TCString tied to ownership of Self
+            key: unsafe { TCString::return_val(key) },
+            // SAFETY:
+            //  - ownership of the TCString tied to ownership of Self
+            value: unsafe { TCString::return_val(value) },
+        }
+    }
+}
+
+/// TCKVList represents a list of key/value pairs.
+///
+/// The content of this struct must be treated as read-only.
+#[repr(C)]
+pub struct TCKVList {
+    /// number of key/value pairs in items
+    len: libc::size_t,
+
+    /// total size of items (internal use only)
+    _capacity: libc::size_t,
+
+    /// array of TCKV's. these remain owned by the TCKVList instance and will be freed by
+    /// tc_kv_list_free.  This pointer is never NULL for a valid TCKVList.
+    items: *mut TCKV,
+}
+
+impl CList for TCKVList {
+    type Element = TCKV;
+
+    unsafe fn from_raw_parts(items: *mut Self::Element, len: usize, cap: usize) -> Self {
+        TCKVList {
+            len,
+            _capacity: cap,
+            items,
+        }
+    }
+
+    fn slice(&mut self) -> &mut [Self::Element] {
+        // SAFETY:
+        //  - because we have &mut self, we have read/write access to items[0..len]
+        //  - all items are properly initialized Element's
+        //  - return value lifetime is equal to &mmut self's, so access is exclusive
+        //  - items and len came from Vec, so total size is < isize::MAX
+        unsafe { std::slice::from_raw_parts_mut(self.items, self.len) }
+    }
+
+    fn into_raw_parts(self) -> (*mut Self::Element, usize, usize) {
+        (self.items, self.len, self._capacity)
+    }
+}
+
+/// Free a TCKVList instance.  The instance, and all TCKVs it contains, must not be used after
+/// this call.
+///
+/// When this call returns, the `items` pointer will be NULL, signalling an invalid TCKVList.
+#[no_mangle]
+pub unsafe extern "C" fn tc_kv_list_free(tckvs: *mut TCKVList) {
+    // SAFETY:
+    //  - tckvs is not NULL and points to a valid TCKVList (caller is not allowed to
+    //    modify the list)
+    //  - caller promises not to use the value after return
+    unsafe { drop_value_list(tckvs) }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn empty_list_has_non_null_pointer() {
+        let tckvs = unsafe { TCKVList::return_val(Vec::new()) };
+        assert!(!tckvs.items.is_null());
+        assert_eq!(tckvs.len, 0);
+        assert_eq!(tckvs._capacity, 0);
+    }
+
+    #[test]
+    fn free_sets_null_pointer() {
+        let mut tckvs = unsafe { TCKVList::return_val(Vec::new()) };
+        // SAFETY: testing expected behavior
+        unsafe { tc_kv_list_free(&mut tckvs) };
+        assert!(tckvs.items.is_null());
+        assert_eq!(tckvs.len, 0);
+        assert_eq!(tckvs._capacity, 0);
+    }
+}