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forgejo/vendor/github.com/pingcap/tidb/mysql/fsp.go

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// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package mysql
import (
"math"
"strconv"
"strings"
"github.com/juju/errors"
)
const (
// UnspecifiedFsp is the unspecified fractional seconds part.
UnspecifiedFsp int = -1
// MaxFsp is the maximum digit of fractional seconds part.
MaxFsp int = 6
// MinFsp is the minimum digit of fractional seconds part.
MinFsp int = 0
// DefaultFsp is the default digit of fractional seconds part.
// MySQL use 0 as the default Fsp.
DefaultFsp int = 0
)
func checkFsp(fsp int) (int, error) {
if fsp == UnspecifiedFsp {
return DefaultFsp, nil
}
if fsp < MinFsp || fsp > MaxFsp {
return DefaultFsp, errors.Errorf("Invalid fsp %d", fsp)
}
return fsp, nil
}
func parseFrac(s string, fsp int) (int, error) {
if len(s) == 0 {
return 0, nil
}
var err error
fsp, err = checkFsp(fsp)
if err != nil {
return 0, errors.Trace(err)
}
// Use float to calculate frac, e.g, "123" -> "0.123"
if !strings.HasPrefix(s, ".") && !strings.HasPrefix(s, "0.") {
s = "0." + s
}
frac, err := strconv.ParseFloat(s, 64)
if err != nil {
return 0, errors.Trace(err)
}
// round frac to the nearest value with FSP
var round float64
pow := math.Pow(10, float64(fsp))
digit := pow * frac
_, div := math.Modf(digit)
if div >= 0.5 {
round = math.Ceil(digit)
} else {
round = math.Floor(digit)
}
// Get the final frac, with 6 digit number
// 0.1236 round 3 -> 124 -> 123000
// 0.0312 round 2 -> 3 -> 30000
return int(round * math.Pow10(MaxFsp-fsp)), nil
}
// alignFrac is used to generate alignment frac, like `100` -> `100000`
func alignFrac(s string, fsp int) string {
sl := len(s)
if sl < fsp {
return s + strings.Repeat("0", fsp-sl)
}
return s
}