Add array::decode_fill_value_into()

LDeakin · Oct 27, 2024 · 0ba54a4 · 0ba54a4
1 parent cbe67c5
commit 0ba54a4
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Showing 5 changed files with 61 additions and 39 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
  - Add a `makefile` and simplify `BUILD.md`
  - Add chunk-by-chunk update example in `Array` docs
+ - Add `array::decode_fill_value_into()`
 
 ### Changed
 - Bump `unsafe_cell_slice` to 0.2.0

diff --git a/zarrs/src/array.rs b/zarrs/src/array.rs
@@ -46,7 +46,7 @@ use std::sync::Arc;
 
 pub use self::{
     array_builder::ArrayBuilder,
-    array_bytes::{ArrayBytes, ArrayBytesError, RawBytes, RawBytesOffsets},
+    array_bytes::{decode_fill_value_into, ArrayBytes, ArrayBytesError, RawBytes, RawBytesOffsets},
     array_errors::{ArrayCreateError, ArrayError},
     array_metadata_options::ArrayMetadataOptions,
     array_representation::{

diff --git a/zarrs/src/array/array_async_readable.rs b/zarrs/src/array/array_async_readable.rs
@@ -11,10 +11,10 @@ use crate::{
 };
 
 use super::{
-    array_bytes::{merge_chunks_vlen, update_bytes_flen},
+    array_bytes::{decode_fill_value_into, merge_chunks_vlen},
     codec::{
         options::CodecOptions, ArrayToBytesCodecTraits, AsyncArrayPartialDecoderTraits,
-        AsyncStoragePartialDecoder, CodecError,
+        AsyncStoragePartialDecoder,
     },
     concurrency::concurrency_chunks_and_codec,
     element::ElementOwned,
@@ -381,23 +381,14 @@ impl<TStorage: ?Sized + AsyncReadableStorageTraits + 'static> Array<TStorage> {
                 )
                 .map_err(ArrayError::CodecError)
         } else {
-            // Fill with the fill value
-            let array_size = ArraySize::new(self.data_type().size(), output_subset.num_elements());
-            if let ArrayBytes::Fixed(fill_value_bytes) =
-                ArrayBytes::new_fill_value(array_size, self.fill_value())
-            {
-                update_bytes_flen(
-                    output,
-                    output_shape,
-                    &fill_value_bytes,
-                    output_subset,
-                    self.data_type().fixed_size().unwrap(),
-                );
-                Ok(())
-            } else {
-                // TODO: Variable length data type support?
-                Err(ArrayError::CodecError(CodecError::ExpectedFixedLengthBytes))
-            }
+            decode_fill_value_into(
+                self.data_type(),
+                self.fill_value(),
+                output,
+                output_shape,
+                output_subset,
+            )
+            .map_err(ArrayError::CodecError)
         }
     }
 

diff --git a/zarrs/src/array/array_bytes.rs b/zarrs/src/array/array_bytes.rs
@@ -503,6 +503,45 @@ pub fn extract_decoded_regions_vlen<'a>(
     Ok(out)
 }
 
+/// Decode the fill value into a subset of a preallocated output.
+///
+/// This method is intended for internal use by Array.
+/// It currently only works for fixed length data types.
+///
+/// # Errors
+/// Returns [`CodecError::ExpectedFixedLengthBytes`] for variable-sized data.
+///
+/// # Safety
+/// The caller must ensure that:
+///  - `data_type` and `fill_value` are compatible,
+///  - `output` holds enough space for the preallocated bytes of an array with `output_shape` and `data_type`, and
+///  - `output_subset` is within the bounds of `output_shape`.
+pub unsafe fn decode_fill_value_into(
+    data_type: &DataType,
+    fill_value: &FillValue,
+    output: &UnsafeCellSlice<u8>,
+    output_shape: &[u64],
+    output_subset: &ArraySubset,
+) -> Result<(), CodecError> {
+    let array_size = ArraySize::new(data_type.size(), output_subset.num_elements());
+    if let (ArrayBytes::Fixed(fill_value_bytes), Some(data_type_size)) = (
+        ArrayBytes::new_fill_value(array_size, fill_value),
+        data_type.fixed_size(),
+    ) {
+        update_bytes_flen(
+            output,
+            output_shape,
+            &fill_value_bytes,
+            output_subset,
+            data_type_size,
+        );
+        Ok(())
+    } else {
+        // TODO: Variable length data type support?
+        Err(CodecError::ExpectedFixedLengthBytes)
+    }
+}
+
 impl<'a> From<RawBytes<'a>> for ArrayBytes<'a> {
     fn from(bytes: RawBytes<'a>) -> Self {
         Self::new_flen(bytes)

diff --git a/zarrs/src/array/array_sync_readable.rs b/zarrs/src/array/array_sync_readable.rs
@@ -13,9 +13,9 @@ use crate::{
 };
 
 use super::{
-    array_bytes::{merge_chunks_vlen, update_bytes_flen},
+    array_bytes::{decode_fill_value_into, merge_chunks_vlen},
     codec::{
-        options::CodecOptions, ArrayPartialDecoderTraits, ArrayToBytesCodecTraits, CodecError,
+        options::CodecOptions, ArrayPartialDecoderTraits, ArrayToBytesCodecTraits,
         StoragePartialDecoder,
     },
     concurrency::concurrency_chunks_and_codec,
@@ -502,23 +502,14 @@ impl<TStorage: ?Sized + ReadableStorageTraits + 'static> Array<TStorage> {
                 )
                 .map_err(ArrayError::CodecError)
         } else {
-            // Fill with the fill value
-            let array_size = ArraySize::new(self.data_type().size(), output_subset.num_elements());
-            if let ArrayBytes::Fixed(fill_value_bytes) =
-                ArrayBytes::new_fill_value(array_size, self.fill_value())
-            {
-                update_bytes_flen(
-                    output,
-                    output_shape,
-                    &fill_value_bytes,
-                    output_subset,
-                    self.data_type().fixed_size().unwrap(),
-                );
-                Ok(())
-            } else {
-                // TODO: Variable length data type support?
-                Err(ArrayError::CodecError(CodecError::ExpectedFixedLengthBytes))
-            }
+            decode_fill_value_into(
+                self.data_type(),
+                self.fill_value(),
+                output,
+                output_shape,
+                output_subset,
+            )
+            .map_err(ArrayError::CodecError)
         }
     }