Have iter_from/iter_dup_from return a Result

It previously called unwrap() which panics if a key isn't found

Author: tarcieri

src/cursor.rs

@@ -61,9 +61,9 @@ pub trait Cursor<'txn> {
     /// For databases with duplicate data items (`DatabaseFlags::DUP_SORT`), the
     /// duplicate data items of each key will be returned before moving on to
     /// the next key.
-    fn iter_from<K>(&mut self, key: K) -> Iter<'txn> where K: AsRef<[u8]> {
-        self.get(Some(key.as_ref()), None, ffi::MDB_SET_RANGE).unwrap();
-        Iter::new(self.cursor(), ffi::MDB_GET_CURRENT, ffi::MDB_NEXT)
+    fn iter_from<K>(&mut self, key: K) -> Result<Iter<'txn>> where K: AsRef<[u8]> {
+        try!(self.get(Some(key.as_ref()), None, ffi::MDB_SET_RANGE));
+        Ok(Iter::new(self.cursor(), ffi::MDB_GET_CURRENT, ffi::MDB_NEXT))
     }
 
     /// Iterate over duplicate database items. The iterator will begin with the
@@ -83,8 +83,8 @@ pub trait Cursor<'txn> {
     /// Iterate over duplicate items in the database starting from the given
     /// key. Each item will be returned as an iterator of its duplicates.
     fn iter_dup_from<K>(&mut self, key: &K) -> IterDup<'txn> where K: AsRef<[u8]> {
-        self.get(Some(key.as_ref()), None, ffi::MDB_SET_RANGE).unwrap();
-        IterDup::new(self.cursor(), ffi::MDB_GET_CURRENT)
+        try!(self.get(Some(key.as_ref()), None, ffi::MDB_SET_RANGE));
+        Ok(IterDup::new(self.cursor(), ffi::MDB_GET_CURRENT))
     }
 
     /// Iterate over the duplicates of the item in the database with the given
@@ -419,7 +419,7 @@ mod test {
         assert_eq!(items, cursor.iter_start().collect::<Vec<_>>());
 
         assert_eq!(items.clone().into_iter().skip(1).collect::<Vec<_>>(),
-                   cursor.iter_from(b"key2").collect::<Vec<_>>());
+                   cursor.iter_from(b"key2").unwrap().collect::<Vec<_>>());
     }
 
     #[test]
@@ -458,7 +458,7 @@ mod test {
                    cursor.iter_dup_start().flat_map(|x| x).collect::<Vec<(&[u8], &[u8])>>());
 
         assert_eq!(items.clone().into_iter().skip(3).collect::<Vec<(&[u8], &[u8])>>(),
-                   cursor.iter_dup_from(b"b").flat_map(|x| x).collect::<Vec<_>>());
+                   cursor.iter_dup_from(b"b").unwrap().flat_map(|x| x).collect::<Vec<_>>());
 
         assert_eq!(items.clone().into_iter().skip(3).collect::<Vec<(&[u8], &[u8])>>(),
                    cursor.iter_dup_from(b"ab").flat_map(|x| x).collect::<Vec<_>>());