emkornfield commented on a change in pull request #10379: URL: https://github.com/apache/arrow/pull/10379#discussion_r645674860
########## File path: go/parquet/internal/encoding/byte_array_decoder.go ########## @@ -0,0 +1,88 @@ +// 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. + +package encoding + +import ( + "encoding/binary" + + "github.com/apache/arrow/go/parquet" + "github.com/apache/arrow/go/parquet/internal/utils" + "golang.org/x/xerrors" +) + +// PlainByteArrayDecoder decodes a data chunk for bytearrays according to +// the plain encoding. The byte arrays will use slices to reference the +// data rather than copying it. +// +// The parquet spec defines Plain encoding for ByteArrays as a 4 byte little +// endian integer containing the length of the bytearray followed by that many +// bytes being the raw data of the byte array. +type PlainByteArrayDecoder struct { + decoder +} + +// Type returns parquet.Types.ByteArray for this decoder +func (PlainByteArrayDecoder) Type() parquet.Type { + return parquet.Types.ByteArray +} + +// Decode will populate the slice of bytearrays in full or until the number +// of values is consumed. +// +// Returns the number of values that were decoded. +func (pbad *PlainByteArrayDecoder) Decode(out []parquet.ByteArray) (int, error) { + max := utils.MinInt(len(out), pbad.nvals) + + for i := 0; i < max; i++ { + // there should always be at least four bytes which is the length of the + // next value in the data. + if len(pbad.data) < 4 { + return i, xerrors.New("parquet: eof reading bytearray") + } + + // the first 4 bytes are a little endian int32 length + byteLen := int32(binary.LittleEndian.Uint32(pbad.data[:4])) + if byteLen < 0 { + return i, xerrors.New("parquet: invalid BYTE_ARRAY value") + } + + if int64(len(pbad.data)) < int64(byteLen)+4 { + return i, xerrors.New("parquet: eof reading bytearray") + } + + out[i] = pbad.data[4 : byteLen+4 : byteLen+4] + pbad.data = pbad.data[byteLen+4:] + } + + pbad.nvals -= max + return max, nil +} + +// DecodeSpaced is like Decode, but expands the slice out to leave empty values +// where the validBits bitmap has 0s +func (pbad *PlainByteArrayDecoder) DecodeSpaced(out []parquet.ByteArray, nullCount int, validBits []byte, validBitsOffset int64) (int, error) { Review comment: one more thought, I'm not sure how you've organized the remaining code, but spacing values might more naturally fit with Arrow (not critical, and might not make sense) -- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
