mirror of
https://github.com/k3s-io/kubernetes.git
synced 2025-10-31 13:50:01 +00:00
100 lines
2.3 KiB
Go
100 lines
2.3 KiB
Go
/*
|
|
Copyright 2017 The Kubernetes 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 tail
|
|
|
|
import (
|
|
"bytes"
|
|
"io"
|
|
"io/ioutil"
|
|
"os"
|
|
)
|
|
|
|
const (
|
|
// blockSize is the block size used in tail.
|
|
blockSize = 1024
|
|
)
|
|
|
|
var (
|
|
// eol is the end-of-line sign in the log.
|
|
eol = []byte{'\n'}
|
|
)
|
|
|
|
// ReadAtMost reads at most max bytes from the end of the file identified by path or
|
|
// returns an error. It returns true if the file was longer than max. It will
|
|
// allocate up to max bytes.
|
|
func ReadAtMost(path string, max int64) ([]byte, bool, error) {
|
|
f, err := os.Open(path)
|
|
if err != nil {
|
|
return nil, false, err
|
|
}
|
|
defer f.Close()
|
|
fi, err := f.Stat()
|
|
if err != nil {
|
|
return nil, false, err
|
|
}
|
|
size := fi.Size()
|
|
if size == 0 {
|
|
return nil, false, nil
|
|
}
|
|
if size < max {
|
|
max = size
|
|
}
|
|
offset, err := f.Seek(-max, io.SeekEnd)
|
|
if err != nil {
|
|
return nil, false, err
|
|
}
|
|
data, err := ioutil.ReadAll(f)
|
|
return data, offset > 0, err
|
|
}
|
|
|
|
// FindTailLineStartIndex returns the start of last nth line.
|
|
// * If n < 0, return the beginning of the file.
|
|
// * If n >= 0, return the beginning of last nth line.
|
|
// Notice that if the last line is incomplete (no end-of-line), it will not be counted
|
|
// as one line.
|
|
func FindTailLineStartIndex(f io.ReadSeeker, n int64) (int64, error) {
|
|
if n < 0 {
|
|
return 0, nil
|
|
}
|
|
size, err := f.Seek(0, io.SeekEnd)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
var left, cnt int64
|
|
buf := make([]byte, blockSize)
|
|
for right := size; right > 0 && cnt <= n; right -= blockSize {
|
|
left = right - blockSize
|
|
if left < 0 {
|
|
left = 0
|
|
buf = make([]byte, right)
|
|
}
|
|
if _, err := f.Seek(left, io.SeekStart); err != nil {
|
|
return 0, err
|
|
}
|
|
if _, err := f.Read(buf); err != nil {
|
|
return 0, err
|
|
}
|
|
cnt += int64(bytes.Count(buf, eol))
|
|
}
|
|
for ; cnt > n; cnt-- {
|
|
idx := bytes.Index(buf, eol) + 1
|
|
buf = buf[idx:]
|
|
left += int64(idx)
|
|
}
|
|
return left, nil
|
|
}
|