github.com/XiaoMi/Gaea@v1.2.5/parser/tidb-types/fsp.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 types
    15  
    16  import (
    17  	"math"
    18  	"strconv"
    19  	"strings"
    20  
    21  	"github.com/pingcap/errors"
    22  )
    23  
    24  const (
    25  	// UnspecifiedFsp is the unspecified fractional seconds part.
    26  	UnspecifiedFsp = -1
    27  	// MaxFsp is the maximum digit of fractional seconds part.
    28  	MaxFsp = 6
    29  	// MinFsp is the minimum digit of fractional seconds part.
    30  	MinFsp = 0
    31  	// DefaultFsp is the default digit of fractional seconds part.
    32  	// MySQL use 0 as the default Fsp.
    33  	DefaultFsp = 0
    34  )
    35  
    36  // CheckFsp checks whether fsp is in valid range.
    37  func CheckFsp(fsp int) (int, error) {
    38  	if fsp == UnspecifiedFsp {
    39  		return DefaultFsp, nil
    40  	}
    41  	if fsp < MinFsp || fsp > MaxFsp {
    42  		return DefaultFsp, errors.Errorf("Invalid fsp %d", fsp)
    43  	}
    44  	return fsp, nil
    45  }
    46  
    47  // ParseFrac parses the input string according to fsp, returns the microsecond,
    48  // and also a bool value to indice overflow. eg:
    49  // "999" fsp=2 will overflow.
    50  func ParseFrac(s string, fsp int) (v int, overflow bool, err error) {
    51  	if len(s) == 0 {
    52  		return 0, false, nil
    53  	}
    54  
    55  	fsp, err = CheckFsp(fsp)
    56  	if err != nil {
    57  		return 0, false, errors.Trace(err)
    58  	}
    59  
    60  	if fsp >= len(s) {
    61  		tmp, e := strconv.ParseInt(s, 10, 64)
    62  		if e != nil {
    63  			return 0, false, errors.Trace(e)
    64  		}
    65  		v = int(float64(tmp) * math.Pow10(MaxFsp-len(s)))
    66  		return
    67  	}
    68  
    69  	// Round when fsp < string length.
    70  	tmp, e := strconv.ParseInt(s[:fsp+1], 10, 64)
    71  	if e != nil {
    72  		return 0, false, errors.Trace(e)
    73  	}
    74  	tmp = (tmp + 5) / 10
    75  
    76  	if float64(tmp) >= math.Pow10(fsp) {
    77  		// overflow
    78  		return 0, true, nil
    79  	}
    80  
    81  	// Get the final frac, with 6 digit number
    82  	//  1236 round 3 -> 124 -> 124000
    83  	//  0312 round 2 -> 3 -> 30000
    84  	//  999 round 2 -> 100 -> overflow
    85  	v = int(float64(tmp) * math.Pow10(MaxFsp-fsp))
    86  	return
    87  }
    88  
    89  // alignFrac is used to generate alignment frac, like `100` -> `100000`
    90  func alignFrac(s string, fsp int) string {
    91  	sl := len(s)
    92  	if sl < fsp {
    93  		return s + strings.Repeat("0", fsp-sl)
    94  	}
    95  
    96  	return s
    97  }