perf: implement slice access to individual data

BREAKING CHANGE: changes return value of
IndividualTable::parents and ::location

Author: molpopgen

src/_macros.rs

@@ -70,7 +70,7 @@ macro_rules! unsafe_tsk_ragged_column_access {
         }
     }};
 
-    ($i: expr, $lo: expr, $hi: expr, $array: expr, $offset_array: expr, $offset_array_len: expr, $output_id_type: expr) => {{
+    ($i: expr, $lo: expr, $hi: expr, $array: expr, $offset_array: expr, $offset_array_len: expr, $output_id_type: ty) => {{
         let i = $crate::SizeType::try_from($i)?;
         if $i < $lo || i >= $hi {
             Err(TskitError::IndexError {})
@@ -86,11 +86,12 @@ macro_rules! unsafe_tsk_ragged_column_access {
             if start == stop {
                 Ok(None)
             } else {
-                let mut buffer = vec![];
-                for i in start..stop {
-                    buffer.push($output_id_type(unsafe { *$array.offset(i as isize) }));
-                }
-                Ok(Some(buffer))
+                Ok(Some(unsafe {
+                    std::slice::from_raw_parts(
+                        $array.offset(start as isize) as *const $output_id_type,
+                        stop as usize,
+                    )
+                }))
             }
         }
     }};

src/individual_table.rs

@@ -61,8 +61,8 @@ fn make_individual_table_row(table: &IndividualTable, pos: tsk_id_t) -> Option<I
         let rv = IndividualTableRow {
             id: pos.into(),
             flags: table.flags(pos).unwrap(),
-            location: table.location(pos).unwrap(),
-            parents: table.parents(pos).unwrap(),
+            location: table.location(pos).unwrap().map(|s| s.to_vec()),
+            parents: table.parents(pos).unwrap().map(|s| s.to_vec()),
             metadata: table_row_decode_metadata!(table_ref, pos),
         };
         Some(rv)
@@ -131,7 +131,7 @@ impl<'a> IndividualTable<'a> {
     pub fn location<I: Into<IndividualId> + Copy>(
         &self,
         row: I,
-    ) -> Result<Option<Vec<Location>>, TskitError> {
+    ) -> Result<Option<&[Location]>, TskitError> {
         unsafe_tsk_ragged_column_access!(
             row.into().0,
             0,
@@ -151,7 +151,7 @@ impl<'a> IndividualTable<'a> {
     pub fn parents<I: Into<IndividualId> + Copy>(
         &self,
         row: I,
-    ) -> Result<Option<Vec<IndividualId>>, TskitError> {
+    ) -> Result<Option<&[IndividualId]>, TskitError> {
         unsafe_tsk_ragged_column_access!(
             row.into().0,
             0,