github.com/whtcorpsinc/MilevaDB-Prod@v0.0.0-20211104133533-f57f4be3b597/soliton/codec/decimal.go (about)

     1  // Copyright 2020 WHTCORPS INC, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package codec
    15  
    16  import (
    17  	"github.com/whtcorpsinc/errors"
    18  	"github.com/whtcorpsinc/failpoint"
    19  	"github.com/whtcorpsinc/milevadb/types"
    20  )
    21  
    22  // EncodeDecimal encodes a decimal into a byte slice which can be sorted lexicographically later.
    23  func EncodeDecimal(b []byte, dec *types.MyDecimal, precision, frac int) ([]byte, error) {
    24  	if precision == 0 {
    25  		precision, frac = dec.PrecisionAndFrac()
    26  	}
    27  	b = append(b, byte(precision), byte(frac))
    28  	b, err := dec.WriteBin(precision, frac, b)
    29  	return b, errors.Trace(err)
    30  }
    31  
    32  func valueSizeOfDecimal(dec *types.MyDecimal, precision, frac int) int {
    33  	if precision == 0 {
    34  		precision, frac = dec.PrecisionAndFrac()
    35  	}
    36  	return types.DecimalBinSize(precision, frac) + 2
    37  }
    38  
    39  // DecodeDecimal decodes bytes to decimal.
    40  func DecodeDecimal(b []byte) ([]byte, *types.MyDecimal, int, int, error) {
    41  	failpoint.Inject("errorInDecodeDecimal", func(val failpoint.Value) {
    42  		if val.(bool) {
    43  			failpoint.Return(b, nil, 0, 0, errors.New("gofail error"))
    44  		}
    45  	})
    46  
    47  	if len(b) < 3 {
    48  		return b, nil, 0, 0, errors.New("insufficient bytes to decode value")
    49  	}
    50  	precision := int(b[0])
    51  	frac := int(b[1])
    52  	b = b[2:]
    53  	dec := new(types.MyDecimal)
    54  	binSize, err := dec.FromBin(b, precision, frac)
    55  	b = b[binSize:]
    56  	if err != nil {
    57  		return b, nil, precision, frac, errors.Trace(err)
    58  	}
    59  	return b, dec, precision, frac, nil
    60  }