fixed_len_byte_array_decoder.go

Documentation: github.com/apache/arrow/go/v15/parquet/internal/encoding

     1  // Licensed to the Apache Software Foundation (ASF) under one
     2  // or more contributor license agreements.  See the NOTICE file
     3  // distributed with this work for additional information
     4  // regarding copyright ownership.  The ASF licenses this file
     5  // to you under the Apache License, Version 2.0 (the
     6  // "License"); you may not use this file except in compliance
     7  // with the License.  You may obtain a copy of the License at
     8  //
     9  // http://www.apache.org/licenses/LICENSE-2.0
    10  //
    11  // Unless required by applicable law or agreed to in writing, software
    12  // distributed under the License is distributed on an "AS IS" BASIS,
    13  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14  // See the License for the specific language governing permissions and
    15  // limitations under the License.
    16  
    17  package encoding
    18  
    19  import (
    20  	"math"
    21  
    22  	"github.com/apache/arrow/go/v15/internal/utils"
    23  	"github.com/apache/arrow/go/v15/parquet"
    24  	"golang.org/x/xerrors"
    25  )
    26  
    27  // PlainFixedLenByteArrayDecoder is a plain encoding decoder for Fixed Length Byte Arrays
    28  type PlainFixedLenByteArrayDecoder struct {
    29  	decoder
    30  }
    31  
    32  // Type returns the physical type this decoder operates on, FixedLength Byte Arrays
    33  func (PlainFixedLenByteArrayDecoder) Type() parquet.Type {
    34  	return parquet.Types.FixedLenByteArray
    35  }
    36  
    37  // Decode populates out with fixed length byte array values until either there are no more
    38  // values to decode or the length of out has been filled. Then returns the total number of values
    39  // that were decoded.
    40  func (pflba *PlainFixedLenByteArrayDecoder) Decode(out []parquet.FixedLenByteArray) (int, error) {
    41  	max := utils.Min(len(out), pflba.nvals)
    42  	numBytesNeeded := max * pflba.typeLen
    43  	if numBytesNeeded > len(pflba.data) || numBytesNeeded > math.MaxInt32 {
    44  		return 0, xerrors.New("parquet: eof exception")
    45  	}
    46  
    47  	for idx := range out[:max] {
    48  		out[idx] = pflba.data[:pflba.typeLen]
    49  		pflba.data = pflba.data[pflba.typeLen:]
    50  	}
    51  	return max, nil
    52  }
    53  
    54  // DecodeSpaced does the same as Decode but spaces out the resulting slice according to the bitmap leaving space for null values
    55  func (pflba *PlainFixedLenByteArrayDecoder) DecodeSpaced(out []parquet.FixedLenByteArray, nullCount int, validBits []byte, validBitsOffset int64) (int, error) {
    56  	toRead := len(out) - nullCount
    57  	valuesRead, err := pflba.Decode(out[:toRead])
    58  	if err != nil {
    59  		return valuesRead, err
    60  	}
    61  	if valuesRead != toRead {
    62  		return valuesRead, xerrors.New("parquet: number of values / definitions levels read did not match")
    63  	}
    64  
    65  	return spacedExpand(out, nullCount, validBits, validBitsOffset), nil
    66  }
    67
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