tidb decimal 源码
tidb decimal 代码
文件路径：/util/codec/decimal.go
// Copyright 2015 PingCAP, Inc.
//
// Licensed 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 codec
import (
"github.com/pingcap/errors"
"github.com/pingcap/failpoint"
"github.com/pingcap/tidb/parser/mysql"
"github.com/pingcap/tidb/types"
)
// EncodeDecimal encodes a decimal into a byte slice which can be sorted lexicographically later.
func EncodeDecimal(b []byte, dec *types.MyDecimal, precision, frac int) ([]byte, error) {
if precision == 0 {
precision, frac = dec.PrecisionAndFrac()
}
if frac > mysql.MaxDecimalScale {
frac = mysql.MaxDecimalScale
}
b = append(b, byte(precision), byte(frac))
b, err := dec.WriteBin(precision, frac, b)
return b, errors.Trace(err)
}
func valueSizeOfDecimal(dec *types.MyDecimal, precision, frac int) (int, error) {
if precision == 0 {
precision, frac = dec.PrecisionAndFrac()
}
binSize, err := types.DecimalBinSize(precision, frac)
if err != nil {
return 0, err
}
return binSize + 2, nil
}
// DecodeDecimal decodes bytes to decimal.
func DecodeDecimal(b []byte) ([]byte, *types.MyDecimal, int, int, error) {
failpoint.Inject("errorInDecodeDecimal", func(val failpoint.Value) {
if val.(bool) {
failpoint.Return(b, nil, 0, 0, errors.New("gofail error"))
}
})
if len(b) < 3 {
return b, nil, 0, 0, errors.New("insufficient bytes to decode value")
}
precision := int(b[0])
frac := int(b[1])
b = b[2:]
dec := new(types.MyDecimal)
binSize, err := dec.FromBin(b, precision, frac)
b = b[binSize:]
if err != nil {
return b, nil, precision, frac, errors.Trace(err)
}
return b, dec, precision, frac, nil
}
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