tustvold commented on code in PR #5318: URL: https://github.com/apache/arrow-rs/pull/5318#discussion_r1465582264
########## arrow-json/src/writer/encoder.rs: ########## @@ -0,0 +1,435 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use arrow_array::cast::AsArray; +use arrow_array::types::*; +use arrow_array::*; +use arrow_buffer::{ArrowNativeType, NullBuffer, OffsetBuffer, ScalarBuffer}; +use arrow_cast::display::{ArrayFormatter, FormatOptions}; +use arrow_schema::{ArrowError, DataType, FieldRef}; +use half::f16; +use lexical_core::FormattedSize; +use serde::Serializer; +use std::io::Write; + +#[derive(Debug, Clone, Default)] +pub struct EncoderOptions { + pub explicit_nulls: bool, +} + +pub trait Encoder { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>); +} + +pub fn make_encoder<'a>( + array: &'a dyn Array, + options: &EncoderOptions, +) -> Result<Box<dyn Encoder + 'a>, ArrowError> { + let (encoder, nulls) = make_encoder_impl(array, options)?; + assert!(nulls.is_none(), "root cannot be nullable"); + Ok(encoder) +} + +fn make_encoder_impl<'a>( + array: &'a dyn Array, + options: &EncoderOptions, +) -> Result<(Box<dyn Encoder + 'a>, Option<NullBuffer>), ArrowError> { + macro_rules! primitive_helper { + ($t:ty) => {{ + let array = array.as_primitive::<$t>(); + let nulls = array.nulls().cloned(); + (Box::new(PrimitiveEncoder::new(array)) as _, nulls) + }}; + } + + Ok(downcast_integer! { + array.data_type() => (primitive_helper), + DataType::Float16 => primitive_helper!(Float16Type), + DataType::Float32 => primitive_helper!(Float32Type), + DataType::Float64 => primitive_helper!(Float64Type), + DataType::Boolean => { + let array = array.as_boolean(); + (Box::new(BooleanEncoder(array.clone())), array.nulls().cloned()) + } + DataType::Null => (Box::new(NullEncoder), array.logical_nulls()), + DataType::Utf8 => { + let array = array.as_string::<i32>(); + (Box::new(StringEncoder(array.clone())) as _, array.nulls().cloned()) + } + DataType::LargeUtf8 => { + let array = array.as_string::<i64>(); + (Box::new(StringEncoder(array.clone())) as _, array.nulls().cloned()) + } + DataType::List(_) => { + let array = array.as_list::<i32>(); + (Box::new(ListEncoder::try_new(array, options)?) as _, array.nulls().cloned()) + } + DataType::LargeList(_) => { + let array = array.as_list::<i64>(); + (Box::new(ListEncoder::try_new(array, options)?) as _, array.nulls().cloned()) + } + + DataType::Dictionary(_, _) => downcast_dictionary_array! { + array => (Box::new(DictionaryEncoder::try_new(array, options)?) as _, array.logical_nulls()), + _ => unreachable!() + } + + DataType::Map(_, _) => { + let array = array.as_map(); + (Box::new(MapEncoder::try_new(array, options)?) as _, array.nulls().cloned()) + } + + DataType::Struct(fields) => { + let array = array.as_struct(); + let encoders = fields.iter().zip(array.columns()).map(|(field, array)| { + let (encoder, nulls) = make_encoder_impl(array, options)?; + Ok(FieldEncoder{ + field: field.clone(), + encoder, nulls + }) + }).collect::<Result<Vec<_>, ArrowError>>()?; + + let encoder = StructArrayEncoder{ + encoders, + explicit_nulls: options.explicit_nulls, + }; + (Box::new(encoder) as _, array.nulls().cloned()) + } + d => match d.is_temporal() { + true => { + // Note: the implementation assumes that escaping is not necessary + // If this is extended to support user-provided format specifications + // this assumption may need to be revisited + let options = FormatOptions::new().with_display_error(true); + let formatter = ArrayFormatter::try_new(array, &options)?; + (Box::new(formatter) as _, array.nulls().cloned()) + } + false => return Err(ArrowError::InvalidArgumentError(format!("JSON Writer does not support data type: {d}"))), + } + }) +} + +fn encode_string(s: &str, out: &mut Vec<u8>) { + let mut serializer = serde_json::Serializer::new(out); + serializer.serialize_str(s).unwrap(); +} + +struct FieldEncoder<'a> { + field: FieldRef, + encoder: Box<dyn Encoder + 'a>, + nulls: Option<NullBuffer>, +} + +struct StructArrayEncoder<'a> { + encoders: Vec<FieldEncoder<'a>>, + explicit_nulls: bool, +} + +impl<'a> Encoder for StructArrayEncoder<'a> { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>) { + out.push(b'{'); + let mut is_first = true; + for field_encoder in &mut self.encoders { + let is_null = field_encoder.nulls.as_ref().is_some_and(|n| n.is_null(idx)); + if is_null && !self.explicit_nulls { + continue; + } + + if !is_first { + out.push(b','); + } + is_first = false; + + encode_string(field_encoder.field.name(), out); + out.push(b':'); + + match is_null { + true => out.extend_from_slice(b"null"), + false => field_encoder.encoder.encode(idx, out), + } + } + out.push(b'}'); + } +} + +trait PrimitiveEncode: ArrowNativeType { + type Buffer; + + // Workaround https://github.com/rust-lang/rust/issues/61415 + fn init_buffer() -> Self::Buffer; + + fn encode(self, buf: &mut Self::Buffer) -> &[u8]; +} + +macro_rules! integer_encode { + ($($t:ty),*) => { + $( + impl PrimitiveEncode for $t { + type Buffer = [u8; Self::FORMATTED_SIZE]; + + fn init_buffer() -> Self::Buffer { + [0; Self::FORMATTED_SIZE] + } + + fn encode(self, buf: &mut Self::Buffer) -> &[u8] { + lexical_core::write(self, buf) + } + } + )* + }; +} +integer_encode!(i8, i16, i32, i64, u8, u16, u32, u64); + +macro_rules! float_encode { + ($($t:ty),*) => { + $( + impl PrimitiveEncode for $t { + type Buffer = [u8; Self::FORMATTED_SIZE]; + + fn init_buffer() -> Self::Buffer { + [0; Self::FORMATTED_SIZE] + } + + fn encode(self, buf: &mut Self::Buffer) -> &[u8] { + if self.is_infinite() || self.is_nan() { + b"null" + } else { + lexical_core::write(self, buf) + } + } + } + )* + }; +} +float_encode!(f32, f64); + +impl PrimitiveEncode for f16 { + type Buffer = <f64 as PrimitiveEncode>::Buffer; + + fn init_buffer() -> Self::Buffer { + f64::init_buffer() + } + + fn encode(self, buf: &mut Self::Buffer) -> &[u8] { + self.to_f64().encode(buf) + } +} + +struct PrimitiveEncoder<N: PrimitiveEncode> { + values: ScalarBuffer<N>, + buffer: N::Buffer, +} + +impl<N: PrimitiveEncode> PrimitiveEncoder<N> { + fn new<P: ArrowPrimitiveType<Native = N>>(array: &PrimitiveArray<P>) -> Self { + Self { + values: array.values().clone(), + buffer: N::init_buffer(), + } + } +} + +impl<N: PrimitiveEncode> Encoder for PrimitiveEncoder<N> { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>) { + out.extend_from_slice(self.values[idx].encode(&mut self.buffer)); + } +} + +struct BooleanEncoder(BooleanArray); + +impl Encoder for BooleanEncoder { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>) { + match self.0.value(idx) { + true => out.extend_from_slice(b"true"), + false => out.extend_from_slice(b"false"), + } + } +} + +struct StringEncoder<O: OffsetSizeTrait>(GenericStringArray<O>); + +impl<O: OffsetSizeTrait> Encoder for StringEncoder<O> { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>) { + encode_string(self.0.value(idx), out); + } +} + +struct ListEncoder<'a, O: OffsetSizeTrait> { + offsets: OffsetBuffer<O>, + nulls: Option<NullBuffer>, + encoder: Box<dyn Encoder + 'a>, +} + +impl<'a, O: OffsetSizeTrait> ListEncoder<'a, O> { + fn try_new( + array: &'a GenericListArray<O>, + options: &EncoderOptions, + ) -> Result<Self, ArrowError> { + let (encoder, nulls) = make_encoder_impl(array.values().as_ref(), options)?; + Ok(Self { + offsets: array.offsets().clone(), + encoder, + nulls, + }) + } +} + +impl<'a, O: OffsetSizeTrait> Encoder for ListEncoder<'a, O> { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>) { + let end = self.offsets[idx + 1].as_usize(); + let start = self.offsets[idx].as_usize(); + out.push(b'['); + match self.nulls.as_ref() { + Some(n) => (start..end).for_each(|idx| { + if idx != start { + out.push(b',') + } + match n.is_null(idx) { + true => out.extend_from_slice(b"null"), + false => self.encoder.encode(idx, out), + } + }), + None => (start..end).for_each(|idx| { + if idx != start { + out.push(b',') + } + self.encoder.encode(idx, out); + }), + } + out.push(b']'); + } +} + +struct DictionaryEncoder<'a, K: ArrowDictionaryKeyType> { + keys: ScalarBuffer<K::Native>, + encoder: Box<dyn Encoder + 'a>, +} + +impl<'a, K: ArrowDictionaryKeyType> DictionaryEncoder<'a, K> { + fn try_new( + array: &'a DictionaryArray<K>, + options: &EncoderOptions, + ) -> Result<Self, ArrowError> { + let encoder = make_encoder(array.values().as_ref(), options)?; + + Ok(Self { + keys: array.keys().values().clone(), + encoder, + }) + } +} + +impl<'a, K: ArrowDictionaryKeyType> Encoder for DictionaryEncoder<'a, K> { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>) { + self.encoder.encode(self.keys[idx].as_usize(), out) + } +} + +impl<'a> Encoder for ArrayFormatter<'a> { + fn encode(&mut self, idx: usize, out: &mut Vec<u8>) { + out.push(b'"'); + // Should be infallible + // Note: We are making an assumption that the formatter does not produce characters that require escaping Review Comment: Yes, it isn't currently possible to hit this, I am just documenting it here for future readers who may not realise this detail -- This is an automated message from the Apache Git Service. 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