github.com/bingoohuang/gg@v0.0.0-20240325092523-45da7dee9335/pkg/sqlparse/tidbparser/dependency/util/codec/decimal.go (about)

     1  // Copyright 2015 PingCAP, 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  	"fmt"
    18  
    19  	"github.com/bingoohuang/gg/pkg/sqlparse/tidbparser/dependency/types"
    20  	"github.com/juju/errors"
    21  )
    22  
    23  // EncodeDecimal encodes a decimal into a byte slice which can be sorted lexicographically later.
    24  func EncodeDecimal(b []byte, dec *types.MyDecimal, precision, frac int) []byte {
    25  	if precision == 0 {
    26  		precision, frac = dec.PrecisionAndFrac()
    27  	}
    28  	b = append(b, byte(precision), byte(frac))
    29  	bin, err := dec.ToBin(precision, frac)
    30  	if err != nil {
    31  		panic(fmt.Sprintf("should not happen, precision %d, frac %d %v", precision, frac, err))
    32  	}
    33  	b = append(b, bin...)
    34  	return b
    35  }
    36  
    37  // DecodeDecimal decodes bytes to decimal.
    38  func DecodeDecimal(b []byte) ([]byte, *types.MyDecimal, error) {
    39  	if len(b) < 3 {
    40  		return b, nil, errors.New("insufficient bytes to decode value")
    41  	}
    42  	precision := int(b[0])
    43  	frac := int(b[1])
    44  	b = b[2:]
    45  	dec := new(types.MyDecimal)
    46  	binSize, err := dec.FromBin(b, precision, frac)
    47  	b = b[binSize:]
    48  	if err != nil {
    49  		return b, nil, errors.Trace(err)
    50  	}
    51  	return b, dec, nil
    52  }