add mapping type

Signed-off-by: Connor Tsui <[email protected]>

Author: connortsui20

encodings/fastlanes/src/bitpacking/array/bitpack_decompress.rs

@@ -24,11 +24,16 @@ use crate::unpack_iter::BitPacked;
 
 /// Unpacks a bit-packed array into a primitive vector.
 pub fn unpack_to_primitive_vector(array: &BitPackedArray) -> PrimitiveVectorMut {
-    match_each_integer_ptype!(array.ptype(), |P| { unpack_to_pvector::<P>(array).into() })
+    match_each_integer_ptype!(array.ptype(), |P| {
+        unpack_to_pvector::<P, fn(P) -> P>(array, std::convert::identity).into()
+    })
 }
 
 /// Unpacks a bit-packed array into a generic [`PVectorMut`].
-pub fn unpack_to_pvector<P: BitPacked>(array: &BitPackedArray) -> PVectorMut<P> {
+pub fn unpack_to_pvector<P: BitPacked, F: FnMut(P) -> P>(
+    array: &BitPackedArray,
+    map_fn: F,
+) -> PVectorMut<P> {
     if array.is_empty() {
         return PVectorMut::with_capacity(0);
     }
@@ -71,6 +76,7 @@ pub fn unpack_to_pvector<P: BitPacked>(array: &BitPackedArray) -> PVectorMut<P>
                     patch_offset,
                     patch_values_slice,
                     patches_validity,
+                    map_fn,
                 )
             };
         });
@@ -87,16 +93,18 @@ pub fn unpack_to_pvector<P: BitPacked>(array: &BitPackedArray) -> PVectorMut<P>
 /// - `patch_indices` must be sorted in ascending order.
 /// - `patch_indices` and `patch_values` must have the same length.
 /// - `buffer` and `validity` must have the same length.
-unsafe fn apply_patches_inner<P, I>(
+unsafe fn apply_patches_inner<P, I, F>(
     buffer: &mut [P],
     validity: &mut MaskMut,
     patch_indices: &[I],
     patch_offset: usize,
     patch_values: &[P],
     patches_validity: &Validity,
+    map_fn: F,
 ) where
     P: NativePType,
     I: UnsignedPType,
+    F: FnMut(P) -> P,
 {
     debug_assert!(!patch_indices.is_empty());
     debug_assert_eq!(patch_indices.len(), patch_values.len());
@@ -106,13 +114,15 @@ unsafe fn apply_patches_inner<P, I>(
 
     match patches_validity {
         Validity::NonNullable | Validity::AllValid => {
-            for (&i, &value) in patch_indices.iter().zip_eq(patch_values) {
+            let mapped_values = patch_values.iter().copied().map(map_fn);
+
+            for (&i, mapped_value) in patch_indices.iter().zip_eq(mapped_values) {
                 let index = i.as_() - patch_offset;
 
                 // SAFETY: `index` is valid because caller guarantees all patch indices are within
                 // bounds after offset adjustment.
                 unsafe { validity.set_unchecked(index) };
-                buffer[index] = value;
+                buffer[index] = mapped_value;
             }
         }
         _ => vortex_panic!("BitPackedArray somehow had nullable patch values"),