[JSON] Add encoding for binary view

arrow-json/src/writer/encoder.rs

@@ -346,6 +346,10 @@ pub fn make_encoder<'a>(
             let array = array.as_string_view();
             NullableEncoder::new(Box::new(StringViewEncoder(array)), array.nulls().cloned())
         }
+        DataType::BinaryView => {
+            let array = array.as_binary_view();
+            NullableEncoder::new(Box::new(BinaryViewEncoder(array)), array.nulls().cloned())
+        }
         DataType::List(_) => {
             let array = array.as_list::<i32>();
             NullableEncoder::new(Box::new(ListEncoder::try_new(field, array, options)?), array.nulls().cloned())
@@ -440,6 +444,14 @@ fn encode_string(s: &str, out: &mut Vec<u8>) {
     serializer.serialize_str(s).unwrap();
 }
 
+fn encode_binary(bytes: &[u8], out: &mut Vec<u8>) {
+    out.push(b'"');
+    for byte in bytes {
+        write!(out, "{byte:02x}").unwrap();
+    }
+    out.push(b'"');
+}
+
 struct FieldEncoder<'a> {
     field: FieldRef,
     encoder: NullableEncoder<'a>,
@@ -609,6 +621,14 @@ impl Encoder for StringViewEncoder<'_> {
     }
 }
 
+struct BinaryViewEncoder<'a>(&'a BinaryViewArray);
+
+impl Encoder for BinaryViewEncoder<'_> {
+    fn encode(&mut self, idx: usize, out: &mut Vec<u8>) {
+        encode_binary(self.0.value(idx), out);
+    }
+}
+
 struct ListEncoder<'a, O: OffsetSizeTrait> {
     offsets: OffsetBuffer<O>,
     encoder: NullableEncoder<'a>,

arrow-json/src/writer/mod.rs

@@ -1751,34 +1751,49 @@ mod tests {
         Ok(())
     }
 
-    fn binary_encoding_test<O: OffsetSizeTrait>() {
-        // set up schema
+    fn build_array_binary<O: OffsetSizeTrait>(values: &[Option<&[u8]>]) -> RecordBatch {
         let schema = SchemaRef::new(Schema::new(vec![Field::new(
             "bytes",
             GenericBinaryType::<O>::DATA_TYPE,
             true,
         )]));
-
-        // build record batch:
         let mut builder = GenericByteBuilder::<GenericBinaryType<O>>::new();
-        let values = [Some(b"Ned Flanders"), None, Some(b"Troy McClure")];
         for value in values {
             match value {
                 Some(v) => builder.append_value(v),
                 None => builder.append_null(),
             }
         }
         let array = Arc::new(builder.finish()) as ArrayRef;
-        let batch = RecordBatch::try_new(schema, vec![array]).unwrap();
+        RecordBatch::try_new(schema, vec![array]).unwrap()
+    }
+
+    fn build_array_binary_view(values: &[Option<&[u8]>]) -> RecordBatch {
+        let schema = SchemaRef::new(Schema::new(vec![Field::new(
+            "bytes",
+            DataType::BinaryView,
+            true,
+        )]));
+        let mut builder = BinaryViewBuilder::new();
+        for value in values {
+            match value {
+                Some(v) => builder.append_value(v),
+                None => builder.append_null(),
+            }
+        }
+        let array = Arc::new(builder.finish()) as ArrayRef;
+        RecordBatch::try_new(schema, vec![array]).unwrap()
+    }
 
+    fn assert_binary_json(batch: &RecordBatch) {
         // encode and check JSON with explicit nulls:
         {
             let mut buf = Vec::new();
             let json_value: Value = {
                 let mut writer = WriterBuilder::new()
                     .with_explicit_nulls(true)
                     .build::<_, JsonArray>(&mut buf);
-                writer.write(&batch).unwrap();
+                writer.write(batch).unwrap();
                 writer.close().unwrap();
                 serde_json::from_slice(&buf).unwrap()
             };
@@ -1806,20 +1821,16 @@ mod tests {
                 // explicit nulls are off by default, so we don't need
                 // to set that when creating the writer:
                 let mut writer = ArrayWriter::new(&mut buf);
-                writer.write(&batch).unwrap();
+                writer.write(batch).unwrap();
                 writer.close().unwrap();
                 serde_json::from_slice(&buf).unwrap()
             };
 
             assert_eq!(
                 json!([
-                    {
-                        "bytes": "4e656420466c616e64657273"
-                    },
-                    {}, // empty because nulls are omitted
-                    {
-                        "bytes": "54726f79204d63436c757265"
-                    }
+                    { "bytes": "4e656420466c616e64657273" },
+                    {},
+                    { "bytes": "54726f79204d63436c757265" }
                 ]),
                 json_value
             );
@@ -1828,10 +1839,25 @@ mod tests {
 
     #[test]
     fn test_writer_binary() {
+        let values: [Option<&[u8]>; 3] = [
+            Some(b"Ned Flanders" as &[u8]),
+            None,
+            Some(b"Troy McClure" as &[u8]),
+        ];
         // Binary:
-        binary_encoding_test::<i32>();
+        {
+            let batch = build_array_binary::<i32>(&values);
+            assert_binary_json(&batch);
+        }
         // LargeBinary:
-        binary_encoding_test::<i64>();
+        {
+            let batch = build_array_binary::<i64>(&values);
+            assert_binary_json(&batch);
+        }
+        {
+            let batch = build_array_binary_view(&values);
+            assert_binary_json(&batch);
+        }
     }
 
     #[test]