tidb fsp 源码
tidb fsp 代码
文件路径：/types/fsp.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 types
import (
"math"
"strconv"
"strings"
"github.com/pingcap/errors"
)
const (
// UnspecifiedFsp is the unspecified fractional seconds part.
UnspecifiedFsp = -1
// MaxFsp is the maximum digit of fractional seconds part.
MaxFsp = 6
// MinFsp is the minimum digit of fractional seconds part.
MinFsp = 0
// DefaultFsp is the default digit of fractional seconds part.
// MySQL use 0 as the default Fsp.
DefaultFsp = 0
)
// CheckFsp checks whether fsp is in valid range.
func CheckFsp(fsp int) (int, error) {
if fsp == UnspecifiedFsp {
return DefaultFsp, nil
}
if fsp < MinFsp {
return DefaultFsp, errors.Errorf("Invalid fsp %d", fsp)
} else if fsp > MaxFsp {
return MaxFsp, nil
}
return fsp, nil
}
// ParseFrac parses the input string according to fsp, returns the microsecond,
// and also a bool value to indice overflow. eg:
// "999" fsp=2 will overflow.
func ParseFrac(s string, fsp int) (v int, overflow bool, err error) {
if len(s) == 0 {
return 0, false, nil
}
fsp, err = CheckFsp(fsp)
if err != nil {
return 0, false, errors.Trace(err)
}
if fsp >= len(s) {
tmp, e := strconv.ParseInt(s, 10, 64)
if e != nil {
return 0, false, errors.Trace(e)
}
v = int(float64(tmp) * math.Pow10(MaxFsp-len(s)))
return
}
// Round when fsp < string length.
tmp, e := strconv.ParseInt(s[:fsp+1], 10, 64)
if e != nil {
return 0, false, errors.Trace(e)
}
tmp = (tmp + 5) / 10
if float64(tmp) >= math.Pow10(fsp) {
// overflow
return 0, true, nil
}
// Get the final frac, with 6 digit number
// 1236 round 3 -> 124 -> 124000
// 0312 round 2 -> 3 -> 30000
// 999 round 2 -> 100 -> overflow
v = int(float64(tmp) * math.Pow10(MaxFsp-fsp))
return
}
// alignFrac is used to generate alignment frac, like `100` -> `100000` ,`-100` -> `-100000`
func alignFrac(s string, fsp int) string {
sl := len(s)
if sl > 0 && s[0] == '-' {
sl = sl - 1
}
if sl < fsp {
return s + strings.Repeat("0", fsp-sl)
}
return s
}
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