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// Copyright 2013 Google Inc. All Rights Reserved.
// Copyright 2022 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 buffer provides a cache for byte.Buffer instances that can be reused
// to avoid frequent allocation and deallocation. It also has utility code
// for log header formatting that use these buffers.
package buffer
import (
"bytes"
"os"
"sync"
"time"
"k8s.io/klog/v2/internal/severity"
)
var (
// Pid is inserted into log headers. Can be overridden for tests.
Pid = os.Getpid()
)
// Buffer holds a single byte.Buffer for reuse. The zero value is ready for
// use. It also provides some helper methods for output formatting.
type Buffer struct {
bytes.Buffer
Tmp [64]byte // temporary byte array for creating headers.
next *Buffer
}
// Buffers manages the reuse of individual buffer instances. It is thread-safe.
type Buffers struct {
// mu protects the free list. It is separate from the main mutex
// so buffers can be grabbed and printed to without holding the main lock,
// for better parallelization.
mu sync.Mutex
// freeList is a list of byte buffers, maintained under mu.
freeList *Buffer
}
// GetBuffer returns a new, ready-to-use buffer.
func (bl *Buffers) GetBuffer() *Buffer {
bl.mu.Lock()
b := bl.freeList
if b != nil {
bl.freeList = b.next
}
bl.mu.Unlock()
if b == nil {
b = new(Buffer)
} else {
b.next = nil
b.Reset()
}
return b
}
// PutBuffer returns a buffer to the free list.
func (bl *Buffers) PutBuffer(b *Buffer) {
if b.Len() >= 256 {
// Let big buffers die a natural death.
return
}
bl.mu.Lock()
b.next = bl.freeList
bl.freeList = b
bl.mu.Unlock()
}
// Some custom tiny helper functions to print the log header efficiently.
const digits = "0123456789"
// twoDigits formats a zero-prefixed two-digit integer at buf.Tmp[i].
func (buf *Buffer) twoDigits(i, d int) {
buf.Tmp[i+1] = digits[d%10]
d /= 10
buf.Tmp[i] = digits[d%10]
}
// nDigits formats an n-digit integer at buf.Tmp[i],
// padding with pad on the left.
// It assumes d >= 0.
func (buf *Buffer) nDigits(n, i, d int, pad byte) {
j := n - 1
for ; j >= 0 && d > 0; j-- {
buf.Tmp[i+j] = digits[d%10]
d /= 10
}
for ; j >= 0; j-- {
buf.Tmp[i+j] = pad
}
}
// someDigits formats a zero-prefixed variable-width integer at buf.Tmp[i].
func (buf *Buffer) someDigits(i, d int) int {
// Print into the top, then copy down. We know there's space for at least
// a 10-digit number.
j := len(buf.Tmp)
for {
j--
buf.Tmp[j] = digits[d%10]
d /= 10
if d == 0 {
break
}
}
return copy(buf.Tmp[i:], buf.Tmp[j:])
}
// FormatHeader formats a log header using the provided file name and line number.
func (buf *Buffer) FormatHeader(s severity.Severity, file string, line int, now time.Time) {
if line < 0 {
line = 0 // not a real line number, but acceptable to someDigits
}
if s > severity.FatalLog {
s = severity.InfoLog // for safety.
}
// Avoid Fprintf, for speed. The format is so simple that we can do it quickly by hand.
// It's worth about 3X. Fprintf is hard.
_, month, day := now.Date()
hour, minute, second := now.Clock()
// Lmmdd hh:mm:ss.uuuuuu threadid file:line]
buf.Tmp[0] = severity.Char[s]
buf.twoDigits(1, int(month))
buf.twoDigits(3, day)
buf.Tmp[5] = ' '
buf.twoDigits(6, hour)
buf.Tmp[8] = ':'
buf.twoDigits(9, minute)
buf.Tmp[11] = ':'
buf.twoDigits(12, second)
buf.Tmp[14] = '.'
buf.nDigits(6, 15, now.Nanosecond()/1000, '0')
buf.Tmp[21] = ' '
buf.nDigits(7, 22, Pid, ' ') // TODO: should be TID
buf.Tmp[29] = ' '
buf.Write(buf.Tmp[:30])
buf.WriteString(file)
buf.Tmp[0] = ':'
n := buf.someDigits(1, line)
buf.Tmp[n+1] = ']'
buf.Tmp[n+2] = ' '
buf.Write(buf.Tmp[:n+3])
}
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