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position.go
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// Copyright 2022-present The ZTDBP Authors.
// 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 mysql
import (
"fmt"
"strconv"
"strings"
)
// For binlog filename + position based replication
type Position struct {
Name string
Pos uint32
}
func (p Position) Compare(o Position) int {
// First compare binlog name
nameCmp := CompareBinlogFileName(p.Name, o.Name)
if nameCmp != 0 {
return nameCmp
}
// Same binlog file, compare position
if p.Pos > o.Pos {
return 1
} else if p.Pos < o.Pos {
return -1
} else {
return 0
}
}
func (p Position) String() string {
return fmt.Sprintf("(%s, %d)", p.Name, p.Pos)
}
func CompareBinlogFileName(a, b string) int {
// sometimes it's convenient to construct a `Position` literal with no `Name`
if a == "" && b == "" {
return 0
} else if a == "" {
return -1
} else if b == "" {
return 1
}
splitBinlogName := func(n string) (string, int) {
// mysqld appends a numeric extension to the binary log base name to generate binary log file names
// ...
// If you supply an extension in the log name (for example, --log-bin=base_name.extension),
// the extension is silently removed and ignored.
// ref: https://dev.mysql.com/doc/refman/8.0/en/binary-log.html
i := strings.LastIndexByte(n, '.')
if i == -1 {
// try keeping backward compatibility
return n, 0
}
seq, err := strconv.Atoi(n[i+1:])
if err != nil {
panic(fmt.Sprintf("binlog file %s doesn't contain numeric extension", err))
}
return n[:i], seq
}
aBase, aSeq := splitBinlogName(a)
bBase, bSeq := splitBinlogName(b)
if aBase > bBase {
return 1
} else if aBase < bBase {
return -1
}
if aSeq > bSeq {
return 1
} else if aSeq < bSeq {
return -1
} else {
return 0
}
}