tustvold commented on a change in pull request #1082: URL: https://github.com/apache/arrow-rs/pull/1082#discussion_r786194424
########## File path: parquet/src/arrow/array_reader/offset_buffer.rs ########## @@ -0,0 +1,337 @@ +// 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 crate::arrow::record_reader::buffer::{ + BufferQueue, ScalarBuffer, ScalarValue, ValuesBuffer, +}; +use crate::column::reader::decoder::ValuesBufferSlice; +use crate::errors::{ParquetError, Result}; +use arrow::array::{make_array, ArrayDataBuilder, ArrayRef, OffsetSizeTrait}; +use arrow::buffer::Buffer; +use arrow::datatypes::{ArrowNativeType, DataType as ArrowType}; + +/// A buffer of variable-sized byte arrays that can be converted into +/// a corresponding [`ArrayRef`] +pub struct OffsetBuffer<I: ScalarValue> { + pub offsets: ScalarBuffer<I>, + pub values: ScalarBuffer<u8>, +} + +impl<I: ScalarValue> Default for OffsetBuffer<I> { + fn default() -> Self { + let mut offsets = ScalarBuffer::new(); + offsets.resize(1); + Self { + offsets, + values: ScalarBuffer::new(), + } + } +} + +impl<I: OffsetSizeTrait + ScalarValue> OffsetBuffer<I> { + /// Returns the number of byte arrays in this buffer + pub fn len(&self) -> usize { + self.offsets.len() - 1 + } + + /// If `validate_utf8` this verifies that the first character of `data` is + /// the start of a UTF-8 codepoint + /// + /// Note: This does not verify that the entirety of `data` is valid + /// UTF-8. This should be done by calling [`Self::values_as_str`] after + /// all data has been written + pub fn try_push(&mut self, data: &[u8], validate_utf8: bool) -> Result<()> { + if validate_utf8 { + if let Some(&b) = data.first() { + // A valid code-point iff it does not start with 0b10xxxxxx + // Bit-magic taken from `std::str::is_char_boundary` + if (b as i8) < -0x40 { + return Err(ParquetError::General( + "encountered non UTF-8 data".to_string(), + )); + } + } + } + + self.values.extend_from_slice(data); + + let index_offset = I::from_usize(self.values.len()) + .ok_or_else(|| general_err!("index overflow decoding byte array"))?; + + self.offsets.push(index_offset); + Ok(()) + } + + /// Extends this buffer with a list of keys + /// + /// For each value `key` in `keys` this will insert + /// `&dict_values[dict_offsets[key]..dict_offsets[key+1]]` + pub fn extend_from_dictionary<K: ArrowNativeType, V: ArrowNativeType>( + &mut self, + keys: &[K], + dict_offsets: &[V], + dict_values: &[u8], + ) -> Result<()> { + for key in keys { + let index = key.to_usize().unwrap(); + if index + 1 >= dict_offsets.len() { + return Err(general_err!("invalid offset in byte array: {}", index)); + } + let start_offset = dict_offsets[index].to_usize().unwrap(); + let end_offset = dict_offsets[index + 1].to_usize().unwrap(); + + // Dictionary values are verified when decoding dictionary page + self.try_push(&dict_values[start_offset..end_offset], false)?; + } + Ok(()) + } + + /// Validates that `&self.values[start_offset..]` is a valid UTF-8 sequence + /// + /// This MUST be combined with validating that the offsets start on a character + /// boundary, otherwise it would be possible for the values array to be a valid UTF-8 + /// sequence, but not the individual string slices it contains + /// + /// [`Self::try_push`] can perform this validation check on insertion + pub fn check_valid_utf8(&self, start_offset: usize) -> Result<()> { + match std::str::from_utf8(&self.values.as_slice()[start_offset..]) { + Ok(_) => Ok(()), + Err(e) => Err(general_err!("encountered non UTF-8 data: {}", e)), + } + } + + /// Converts this into an [`ArrayRef`] with the provided `data_type` and `null_buffer` + pub fn into_array( + self, + null_buffer: Option<Buffer>, + data_type: ArrowType, + ) -> ArrayRef { + let mut array_data_builder = ArrayDataBuilder::new(data_type) + .len(self.len()) + .add_buffer(self.offsets.into()) + .add_buffer(self.values.into()); + + if let Some(buffer) = null_buffer { + array_data_builder = array_data_builder.null_bit_buffer(buffer); + } + + let data = match cfg!(debug_assertions) { + true => array_data_builder.build().unwrap(), + false => unsafe { array_data_builder.build_unchecked() }, + }; + + make_array(data) + } +} + +impl<I: OffsetSizeTrait + ScalarValue> BufferQueue for OffsetBuffer<I> { + type Output = Self; + type Slice = Self; + + fn split_off(&mut self, len: usize) -> Self::Output { + let remaining_offsets = self.offsets.len() - len - 1; + let offsets = self.offsets.as_slice(); + + let end_offset = offsets[len]; + + let mut new_offsets = ScalarBuffer::new(); + new_offsets.reserve(remaining_offsets + 1); + for v in &offsets[len..] { + new_offsets.push(*v - end_offset) + } + + self.offsets.resize(len + 1); + + Self { + offsets: std::mem::replace(&mut self.offsets, new_offsets), + values: self.values.take(end_offset.to_usize().unwrap()), Review comment: This is a backwards compatibility thing, `ScalarBuffer::Output` must be Buffer to avoid changing the API of `ColumnReaderImpl`. Perhaps this could be included in a future breaking change cleanup PR :thinking: -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
