mirror of
https://github.com/ceph/ceph-csi.git
synced 2025-01-31 17:19:28 +00:00
63 lines
1.6 KiB
Go
63 lines
1.6 KiB
Go
/*
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Copyright 2024 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package logs
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import (
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"bytes"
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"io"
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)
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// blockSize is the block size used in tail.
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const blockSize = 1024
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// findTailLineStartIndex returns the start of last nth line.
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// * If n < 0, return the beginning of the file.
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// * If n >= 0, return the beginning of last nth line.
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// Notice that if the last line is incomplete (no end-of-line), it will not be counted
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// as one line.
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func findTailLineStartIndex(f io.ReadSeeker, n int64) (int64, error) {
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if n < 0 {
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return 0, nil
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}
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size, err := f.Seek(0, io.SeekEnd)
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if err != nil {
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return 0, err
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}
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var left, cnt int64
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buf := make([]byte, blockSize)
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for right := size; right > 0 && cnt <= n; right -= blockSize {
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left = right - blockSize
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if left < 0 {
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left = 0
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buf = make([]byte, right)
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}
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if _, err := f.Seek(left, io.SeekStart); err != nil {
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return 0, err
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}
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if _, err := f.Read(buf); err != nil {
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return 0, err
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}
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cnt += int64(bytes.Count(buf, eol))
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}
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for ; cnt > n; cnt-- {
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idx := bytes.Index(buf, eol) + 1
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buf = buf[idx:]
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left += int64(idx)
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}
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return left, nil
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}
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