Merge pull request #3418 from vrothberg/go-modules

update dependencies

1 files changed, 1288 insertions, 0 deletions

diff --git a/vendor/k8s.io/klog/klog.go b/vendor/k8s.io/klog/klog.go
new file mode 100644
index 000000000..10330d7ef
--- /dev/null
+++ b/vendor/k8s.io/klog/klog.go
@@ -0,0 +1,1288 @@
+// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
+//
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// 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 klog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup.
+// It provides functions Info, Warning, Error, Fatal, plus formatting variants such as
+// Infof. It also provides V-style logging controlled by the -v and -vmodule=file=2 flags.
+//
+// Basic examples:
+//
+//	glog.Info("Prepare to repel boarders")
+//
+//	glog.Fatalf("Initialization failed: %s", err)
+//
+// See the documentation for the V function for an explanation of these examples:
+//
+//	if glog.V(2) {
+//		glog.Info("Starting transaction...")
+//	}
+//
+//	glog.V(2).Infoln("Processed", nItems, "elements")
+//
+// Log output is buffered and written periodically using Flush. Programs
+// should call Flush before exiting to guarantee all log output is written.
+//
+// By default, all log statements write to standard error.
+// This package provides several flags that modify this behavior.
+// As a result, flag.Parse must be called before any logging is done.
+//
+//	-logtostderr=true
+//		Logs are written to standard error instead of to files.
+//	-alsologtostderr=false
+//		Logs are written to standard error as well as to files.
+//	-stderrthreshold=ERROR
+//		Log events at or above this severity are logged to standard
+//		error as well as to files.
+//	-log_dir=""
+//		Log files will be written to this directory instead of the
+//		default temporary directory.
+//
+//	Other flags provide aids to debugging.
+//
+//	-log_backtrace_at=""
+//		When set to a file and line number holding a logging statement,
+//		such as
+//			-log_backtrace_at=gopherflakes.go:234
+//		a stack trace will be written to the Info log whenever execution
+//		hits that statement. (Unlike with -vmodule, the ".go" must be
+//		present.)
+//	-v=0
+//		Enable V-leveled logging at the specified level.
+//	-vmodule=""
+//		The syntax of the argument is a comma-separated list of pattern=N,
+//		where pattern is a literal file name (minus the ".go" suffix) or
+//		"glob" pattern and N is a V level. For instance,
+//			-vmodule=gopher*=3
+//		sets the V level to 3 in all Go files whose names begin "gopher".
+//
+package klog
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	stdLog "log"
+	"math"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// severity identifies the sort of log: info, warning etc. It also implements
+// the flag.Value interface. The -stderrthreshold flag is of type severity and
+// should be modified only through the flag.Value interface. The values match
+// the corresponding constants in C++.
+type severity int32 // sync/atomic int32
+
+// These constants identify the log levels in order of increasing severity.
+// A message written to a high-severity log file is also written to each
+// lower-severity log file.
+const (
+	infoLog severity = iota
+	warningLog
+	errorLog
+	fatalLog
+	numSeverity = 4
+)
+
+const severityChar = "IWEF"
+
+var severityName = []string{
+	infoLog:    "INFO",
+	warningLog: "WARNING",
+	errorLog:   "ERROR",
+	fatalLog:   "FATAL",
+}
+
+// get returns the value of the severity.
+func (s *severity) get() severity {
+	return severity(atomic.LoadInt32((*int32)(s)))
+}
+
+// set sets the value of the severity.
+func (s *severity) set(val severity) {
+	atomic.StoreInt32((*int32)(s), int32(val))
+}
+
+// String is part of the flag.Value interface.
+func (s *severity) String() string {
+	return strconv.FormatInt(int64(*s), 10)
+}
+
+// Get is part of the flag.Value interface.
+func (s *severity) Get() interface{} {
+	return *s
+}
+
+// Set is part of the flag.Value interface.
+func (s *severity) Set(value string) error {
+	var threshold severity
+	// Is it a known name?
+	if v, ok := severityByName(value); ok {
+		threshold = v
+	} else {
+		v, err := strconv.Atoi(value)
+		if err != nil {
+			return err
+		}
+		threshold = severity(v)
+	}
+	logging.stderrThreshold.set(threshold)
+	return nil
+}
+
+func severityByName(s string) (severity, bool) {
+	s = strings.ToUpper(s)
+	for i, name := range severityName {
+		if name == s {
+			return severity(i), true
+		}
+	}
+	return 0, false
+}
+
+// OutputStats tracks the number of output lines and bytes written.
+type OutputStats struct {
+	lines int64
+	bytes int64
+}
+
+// Lines returns the number of lines written.
+func (s *OutputStats) Lines() int64 {
+	return atomic.LoadInt64(&s.lines)
+}
+
+// Bytes returns the number of bytes written.
+func (s *OutputStats) Bytes() int64 {
+	return atomic.LoadInt64(&s.bytes)
+}
+
+// Stats tracks the number of lines of output and number of bytes
+// per severity level. Values must be read with atomic.LoadInt64.
+var Stats struct {
+	Info, Warning, Error OutputStats
+}
+
+var severityStats = [numSeverity]*OutputStats{
+	infoLog:    &Stats.Info,
+	warningLog: &Stats.Warning,
+	errorLog:   &Stats.Error,
+}
+
+// Level is exported because it appears in the arguments to V and is
+// the type of the v flag, which can be set programmatically.
+// It's a distinct type because we want to discriminate it from logType.
+// Variables of type level are only changed under logging.mu.
+// The -v flag is read only with atomic ops, so the state of the logging
+// module is consistent.
+
+// Level is treated as a sync/atomic int32.
+
+// Level specifies a level of verbosity for V logs. *Level implements
+// flag.Value; the -v flag is of type Level and should be modified
+// only through the flag.Value interface.
+type Level int32
+
+// get returns the value of the Level.
+func (l *Level) get() Level {
+	return Level(atomic.LoadInt32((*int32)(l)))
+}
+
+// set sets the value of the Level.
+func (l *Level) set(val Level) {
+	atomic.StoreInt32((*int32)(l), int32(val))
+}
+
+// String is part of the flag.Value interface.
+func (l *Level) String() string {
+	return strconv.FormatInt(int64(*l), 10)
+}
+
+// Get is part of the flag.Value interface.
+func (l *Level) Get() interface{} {
+	return *l
+}
+
+// Set is part of the flag.Value interface.
+func (l *Level) Set(value string) error {
+	v, err := strconv.Atoi(value)
+	if err != nil {
+		return err
+	}
+	logging.mu.Lock()
+	defer logging.mu.Unlock()
+	logging.setVState(Level(v), logging.vmodule.filter, false)
+	return nil
+}
+
+// moduleSpec represents the setting of the -vmodule flag.
+type moduleSpec struct {
+	filter []modulePat
+}
+
+// modulePat contains a filter for the -vmodule flag.
+// It holds a verbosity level and a file pattern to match.
+type modulePat struct {
+	pattern string
+	literal bool // The pattern is a literal string
+	level   Level
+}
+
+// match reports whether the file matches the pattern. It uses a string
+// comparison if the pattern contains no metacharacters.
+func (m *modulePat) match(file string) bool {
+	if m.literal {
+		return file == m.pattern
+	}
+	match, _ := filepath.Match(m.pattern, file)
+	return match
+}
+
+func (m *moduleSpec) String() string {
+	// Lock because the type is not atomic. TODO: clean this up.
+	logging.mu.Lock()
+	defer logging.mu.Unlock()
+	var b bytes.Buffer
+	for i, f := range m.filter {
+		if i > 0 {
+			b.WriteRune(',')
+		}
+		fmt.Fprintf(&b, "%s=%d", f.pattern, f.level)
+	}
+	return b.String()
+}
+
+// Get is part of the (Go 1.2)  flag.Getter interface. It always returns nil for this flag type since the
+// struct is not exported.
+func (m *moduleSpec) Get() interface{} {
+	return nil
+}
+
+var errVmoduleSyntax = errors.New("syntax error: expect comma-separated list of filename=N")
+
+// Syntax: -vmodule=recordio=2,file=1,gfs*=3
+func (m *moduleSpec) Set(value string) error {
+	var filter []modulePat
+	for _, pat := range strings.Split(value, ",") {
+		if len(pat) == 0 {
+			// Empty strings such as from a trailing comma can be ignored.
+			continue
+		}
+		patLev := strings.Split(pat, "=")
+		if len(patLev) != 2 || len(patLev[0]) == 0 || len(patLev[1]) == 0 {
+			return errVmoduleSyntax
+		}
+		pattern := patLev[0]
+		v, err := strconv.Atoi(patLev[1])
+		if err != nil {
+			return errors.New("syntax error: expect comma-separated list of filename=N")
+		}
+		if v < 0 {
+			return errors.New("negative value for vmodule level")
+		}
+		if v == 0 {
+			continue // Ignore. It's harmless but no point in paying the overhead.
+		}
+		// TODO: check syntax of filter?
+		filter = append(filter, modulePat{pattern, isLiteral(pattern), Level(v)})
+	}
+	logging.mu.Lock()
+	defer logging.mu.Unlock()
+	logging.setVState(logging.verbosity, filter, true)
+	return nil
+}
+
+// isLiteral reports whether the pattern is a literal string, that is, has no metacharacters
+// that require filepath.Match to be called to match the pattern.
+func isLiteral(pattern string) bool {
+	return !strings.ContainsAny(pattern, `\*?[]`)
+}
+
+// traceLocation represents the setting of the -log_backtrace_at flag.
+type traceLocation struct {
+	file string
+	line int
+}
+
+// isSet reports whether the trace location has been specified.
+// logging.mu is held.
+func (t *traceLocation) isSet() bool {
+	return t.line > 0
+}
+
+// match reports whether the specified file and line matches the trace location.
+// The argument file name is the full path, not the basename specified in the flag.
+// logging.mu is held.
+func (t *traceLocation) match(file string, line int) bool {
+	if t.line != line {
+		return false
+	}
+	if i := strings.LastIndex(file, "/"); i >= 0 {
+		file = file[i+1:]
+	}
+	return t.file == file
+}
+
+func (t *traceLocation) String() string {
+	// Lock because the type is not atomic. TODO: clean this up.
+	logging.mu.Lock()
+	defer logging.mu.Unlock()
+	return fmt.Sprintf("%s:%d", t.file, t.line)
+}
+
+// Get is part of the (Go 1.2) flag.Getter interface. It always returns nil for this flag type since the
+// struct is not exported
+func (t *traceLocation) Get() interface{} {
+	return nil
+}
+
+var errTraceSyntax = errors.New("syntax error: expect file.go:234")
+
+// Syntax: -log_backtrace_at=gopherflakes.go:234
+// Note that unlike vmodule the file extension is included here.
+func (t *traceLocation) Set(value string) error {
+	if value == "" {
+		// Unset.
+		t.line = 0
+		t.file = ""
+	}
+	fields := strings.Split(value, ":")
+	if len(fields) != 2 {
+		return errTraceSyntax
+	}
+	file, line := fields[0], fields[1]
+	if !strings.Contains(file, ".") {
+		return errTraceSyntax
+	}
+	v, err := strconv.Atoi(line)
+	if err != nil {
+		return errTraceSyntax
+	}
+	if v <= 0 {
+		return errors.New("negative or zero value for level")
+	}
+	logging.mu.Lock()
+	defer logging.mu.Unlock()
+	t.line = v
+	t.file = file
+	return nil
+}
+
+// flushSyncWriter is the interface satisfied by logging destinations.
+type flushSyncWriter interface {
+	Flush() error
+	Sync() error
+	io.Writer
+}
+
+func init() {
+	// Default stderrThreshold is ERROR.
+	logging.stderrThreshold = errorLog
+
+	logging.setVState(0, nil, false)
+	go logging.flushDaemon()
+}
+
+var initDefaultsOnce sync.Once
+
+// InitFlags is for explicitly initializing the flags.
+func InitFlags(flagset *flag.FlagSet) {
+
+	// Initialize defaults.
+	initDefaultsOnce.Do(func() {
+		logging.logDir = ""
+		logging.logFile = ""
+		logging.logFileMaxSizeMB = 1800
+		logging.toStderr = true
+		logging.alsoToStderr = false
+		logging.skipHeaders = false
+		logging.skipLogHeaders = false
+	})
+
+	if flagset == nil {
+		flagset = flag.CommandLine
+	}
+
+	flagset.StringVar(&logging.logDir, "log_dir", logging.logDir, "If non-empty, write log files in this directory")
+	flagset.StringVar(&logging.logFile, "log_file", logging.logFile, "If non-empty, use this log file")
+	flagset.Uint64Var(&logging.logFileMaxSizeMB, "log_file_max_size", logging.logFileMaxSizeMB,
+		"Defines the maximum size a log file can grow to. Unit is megabytes. "+
+			"If the value is 0, the maximum file size is unlimited.")
+	flagset.BoolVar(&logging.toStderr, "logtostderr", logging.toStderr, "log to standard error instead of files")
+	flagset.BoolVar(&logging.alsoToStderr, "alsologtostderr", logging.alsoToStderr, "log to standard error as well as files")
+	flagset.Var(&logging.verbosity, "v", "number for the log level verbosity")
+	flagset.BoolVar(&logging.skipHeaders, "skip_headers", logging.skipHeaders, "If true, avoid header prefixes in the log messages")
+	flagset.BoolVar(&logging.skipLogHeaders, "skip_log_headers", logging.skipLogHeaders, "If true, avoid headers when opening log files")
+	flagset.Var(&logging.stderrThreshold, "stderrthreshold", "logs at or above this threshold go to stderr")
+	flagset.Var(&logging.vmodule, "vmodule", "comma-separated list of pattern=N settings for file-filtered logging")
+	flagset.Var(&logging.traceLocation, "log_backtrace_at", "when logging hits line file:N, emit a stack trace")
+}
+
+// Flush flushes all pending log I/O.
+func Flush() {
+	logging.lockAndFlushAll()
+}
+
+// loggingT collects all the global state of the logging setup.
+type loggingT struct {
+	// Boolean flags. Not handled atomically because the flag.Value interface
+	// does not let us avoid the =true, and that shorthand is necessary for
+	// compatibility. TODO: does this matter enough to fix? Seems unlikely.
+	toStderr     bool // The -logtostderr flag.
+	alsoToStderr bool // The -alsologtostderr flag.
+
+	// Level flag. Handled atomically.
+	stderrThreshold severity // The -stderrthreshold flag.
+
+	// freeList is a list of byte buffers, maintained under freeListMu.
+	freeList *buffer
+	// freeListMu maintains 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.
+	freeListMu sync.Mutex
+
+	// mu protects the remaining elements of this structure and is
+	// used to synchronize logging.
+	mu sync.Mutex
+	// file holds writer for each of the log types.
+	file [numSeverity]flushSyncWriter
+	// pcs is used in V to avoid an allocation when computing the caller's PC.
+	pcs [1]uintptr
+	// vmap is a cache of the V Level for each V() call site, identified by PC.
+	// It is wiped whenever the vmodule flag changes state.
+	vmap map[uintptr]Level
+	// filterLength stores the length of the vmodule filter chain. If greater
+	// than zero, it means vmodule is enabled. It may be read safely
+	// using sync.LoadInt32, but is only modified under mu.
+	filterLength int32
+	// traceLocation is the state of the -log_backtrace_at flag.
+	traceLocation traceLocation
+	// These flags are modified only under lock, although verbosity may be fetched
+	// safely using atomic.LoadInt32.
+	vmodule   moduleSpec // The state of the -vmodule flag.
+	verbosity Level      // V logging level, the value of the -v flag/
+
+	// If non-empty, overrides the choice of directory in which to write logs.
+	// See createLogDirs for the full list of possible destinations.
+	logDir string
+
+	// If non-empty, specifies the path of the file to write logs. mutually exclusive
+	// with the log-dir option.
+	logFile string
+
+	// When logFile is specified, this limiter makes sure the logFile won't exceeds a certain size. When exceeds, the
+	// logFile will be cleaned up. If this value is 0, no size limitation will be applied to logFile.
+	logFileMaxSizeMB uint64
+
+	// If true, do not add the prefix headers, useful when used with SetOutput
+	skipHeaders bool
+
+	// If true, do not add the headers to log files
+	skipLogHeaders bool
+}
+
+// buffer holds a byte Buffer for reuse. The zero value is ready for use.
+type buffer struct {
+	bytes.Buffer
+	tmp  [64]byte // temporary byte array for creating headers.
+	next *buffer
+}
+
+var logging loggingT
+
+// setVState sets a consistent state for V logging.
+// l.mu is held.
+func (l *loggingT) setVState(verbosity Level, filter []modulePat, setFilter bool) {
+	// Turn verbosity off so V will not fire while we are in transition.
+	logging.verbosity.set(0)
+	// Ditto for filter length.
+	atomic.StoreInt32(&logging.filterLength, 0)
+
+	// Set the new filters and wipe the pc->Level map if the filter has changed.
+	if setFilter {
+		logging.vmodule.filter = filter
+		logging.vmap = make(map[uintptr]Level)
+	}
+
+	// Things are consistent now, so enable filtering and verbosity.
+	// They are enabled in order opposite to that in V.
+	atomic.StoreInt32(&logging.filterLength, int32(len(filter)))
+	logging.verbosity.set(verbosity)
+}
+
+// getBuffer returns a new, ready-to-use buffer.
+func (l *loggingT) getBuffer() *buffer {
+	l.freeListMu.Lock()
+	b := l.freeList
+	if b != nil {
+		l.freeList = b.next
+	}
+	l.freeListMu.Unlock()
+	if b == nil {
+		b = new(buffer)
+	} else {
+		b.next = nil
+		b.Reset()
+	}
+	return b
+}
+
+// putBuffer returns a buffer to the free list.
+func (l *loggingT) putBuffer(b *buffer) {
+	if b.Len() >= 256 {
+		// Let big buffers die a natural death.
+		return
+	}
+	l.freeListMu.Lock()
+	b.next = l.freeList
+	l.freeList = b
+	l.freeListMu.Unlock()
+}
+
+var timeNow = time.Now // Stubbed out for testing.
+
+/*
+header formats a log header as defined by the C++ implementation.
+It returns a buffer containing the formatted header and the user's file and line number.
+The depth specifies how many stack frames above lives the source line to be identified in the log message.
+
+Log lines have this form:
+	Lmmdd hh:mm:ss.uuuuuu threadid file:line] msg...
+where the fields are defined as follows:
+	L                A single character, representing the log level (eg 'I' for INFO)
+	mm               The month (zero padded; ie May is '05')
+	dd               The day (zero padded)
+	hh:mm:ss.uuuuuu  Time in hours, minutes and fractional seconds
+	threadid         The space-padded thread ID as returned by GetTID()
+	file             The file name
+	line             The line number
+	msg              The user-supplied message
+*/
+func (l *loggingT) header(s severity, depth int) (*buffer, string, int) {
+	_, file, line, ok := runtime.Caller(3 + depth)
+	if !ok {
+		file = "???"
+		line = 1
+	} else {
+		slash := strings.LastIndex(file, "/")
+		if slash >= 0 {
+			file = file[slash+1:]
+		}
+	}
+	return l.formatHeader(s, file, line), file, line
+}
+
+// formatHeader formats a log header using the provided file name and line number.
+func (l *loggingT) formatHeader(s severity, file string, line int) *buffer {
+	now := timeNow()
+	if line < 0 {
+		line = 0 // not a real line number, but acceptable to someDigits
+	}
+	if s > fatalLog {
+		s = infoLog // for safety.
+	}
+	buf := l.getBuffer()
+	if l.skipHeaders {
+		return buf
+	}
+
+	// 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] = severityChar[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])
+	return buf
+}
+
+// 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:])
+}
+
+func (l *loggingT) println(s severity, args ...interface{}) {
+	buf, file, line := l.header(s, 0)
+	fmt.Fprintln(buf, args...)
+	l.output(s, buf, file, line, false)
+}
+
+func (l *loggingT) print(s severity, args ...interface{}) {
+	l.printDepth(s, 1, args...)
+}
+
+func (l *loggingT) printDepth(s severity, depth int, args ...interface{}) {
+	buf, file, line := l.header(s, depth)
+	fmt.Fprint(buf, args...)
+	if buf.Bytes()[buf.Len()-1] != '\n' {
+		buf.WriteByte('\n')
+	}
+	l.output(s, buf, file, line, false)
+}
+
+func (l *loggingT) printf(s severity, format string, args ...interface{}) {
+	buf, file, line := l.header(s, 0)
+	fmt.Fprintf(buf, format, args...)
+	if buf.Bytes()[buf.Len()-1] != '\n' {
+		buf.WriteByte('\n')
+	}
+	l.output(s, buf, file, line, false)
+}
+
+// printWithFileLine behaves like print but uses the provided file and line number.  If
+// alsoLogToStderr is true, the log message always appears on standard error; it
+// will also appear in the log file unless --logtostderr is set.
+func (l *loggingT) printWithFileLine(s severity, file string, line int, alsoToStderr bool, args ...interface{}) {
+	buf := l.formatHeader(s, file, line)
+	fmt.Fprint(buf, args...)
+	if buf.Bytes()[buf.Len()-1] != '\n' {
+		buf.WriteByte('\n')
+	}
+	l.output(s, buf, file, line, alsoToStderr)
+}
+
+// redirectBuffer is used to set an alternate destination for the logs
+type redirectBuffer struct {
+	w io.Writer
+}
+
+func (rb *redirectBuffer) Sync() error {
+	return nil
+}
+
+func (rb *redirectBuffer) Flush() error {
+	return nil
+}
+
+func (rb *redirectBuffer) Write(bytes []byte) (n int, err error) {
+	return rb.w.Write(bytes)
+}
+
+// SetOutput sets the output destination for all severities
+func SetOutput(w io.Writer) {
+	for s := fatalLog; s >= infoLog; s-- {
+		rb := &redirectBuffer{
+			w: w,
+		}
+		logging.file[s] = rb
+	}
+}
+
+// SetOutputBySeverity sets the output destination for specific severity
+func SetOutputBySeverity(name string, w io.Writer) {
+	sev, ok := severityByName(name)
+	if !ok {
+		panic(fmt.Sprintf("SetOutputBySeverity(%q): unrecognized severity name", name))
+	}
+	rb := &redirectBuffer{
+		w: w,
+	}
+	logging.file[sev] = rb
+}
+
+// output writes the data to the log files and releases the buffer.
+func (l *loggingT) output(s severity, buf *buffer, file string, line int, alsoToStderr bool) {
+	l.mu.Lock()
+	if l.traceLocation.isSet() {
+		if l.traceLocation.match(file, line) {
+			buf.Write(stacks(false))
+		}
+	}
+	data := buf.Bytes()
+	if l.toStderr {
+		os.Stderr.Write(data)
+	} else {
+		if alsoToStderr || l.alsoToStderr || s >= l.stderrThreshold.get() {
+			os.Stderr.Write(data)
+		}
+		if l.file[s] == nil {
+			if err := l.createFiles(s); err != nil {
+				os.Stderr.Write(data) // Make sure the message appears somewhere.
+				l.exit(err)
+			}
+		}
+		switch s {
+		case fatalLog:
+			l.file[fatalLog].Write(data)
+			fallthrough
+		case errorLog:
+			l.file[errorLog].Write(data)
+			fallthrough
+		case warningLog:
+			l.file[warningLog].Write(data)
+			fallthrough
+		case infoLog:
+			l.file[infoLog].Write(data)
+		}
+	}
+	if s == fatalLog {
+		// If we got here via Exit rather than Fatal, print no stacks.
+		if atomic.LoadUint32(&fatalNoStacks) > 0 {
+			l.mu.Unlock()
+			timeoutFlush(10 * time.Second)
+			os.Exit(1)
+		}
+		// Dump all goroutine stacks before exiting.
+		// First, make sure we see the trace for the current goroutine on standard error.
+		// If -logtostderr has been specified, the loop below will do that anyway
+		// as the first stack in the full dump.
+		if !l.toStderr {
+			os.Stderr.Write(stacks(false))
+		}
+		// Write the stack trace for all goroutines to the files.
+		trace := stacks(true)
+		logExitFunc = func(error) {} // If we get a write error, we'll still exit below.
+		for log := fatalLog; log >= infoLog; log-- {
+			if f := l.file[log]; f != nil { // Can be nil if -logtostderr is set.
+				f.Write(trace)
+			}
+		}
+		l.mu.Unlock()
+		timeoutFlush(10 * time.Second)
+		os.Exit(255) // C++ uses -1, which is silly because it's anded with 255 anyway.
+	}
+	l.putBuffer(buf)
+	l.mu.Unlock()
+	if stats := severityStats[s]; stats != nil {
+		atomic.AddInt64(&stats.lines, 1)
+		atomic.AddInt64(&stats.bytes, int64(len(data)))
+	}
+}
+
+// timeoutFlush calls Flush and returns when it completes or after timeout
+// elapses, whichever happens first.  This is needed because the hooks invoked
+// by Flush may deadlock when glog.Fatal is called from a hook that holds
+// a lock.
+func timeoutFlush(timeout time.Duration) {
+	done := make(chan bool, 1)
+	go func() {
+		Flush() // calls logging.lockAndFlushAll()
+		done <- true
+	}()
+	select {
+	case <-done:
+	case <-time.After(timeout):
+		fmt.Fprintln(os.Stderr, "glog: Flush took longer than", timeout)
+	}
+}
+
+// stacks is a wrapper for runtime.Stack that attempts to recover the data for all goroutines.
+func stacks(all bool) []byte {
+	// We don't know how big the traces are, so grow a few times if they don't fit. Start large, though.
+	n := 10000
+	if all {
+		n = 100000
+	}
+	var trace []byte
+	for i := 0; i < 5; i++ {
+		trace = make([]byte, n)
+		nbytes := runtime.Stack(trace, all)
+		if nbytes < len(trace) {
+			return trace[:nbytes]
+		}
+		n *= 2
+	}
+	return trace
+}
+
+// logExitFunc provides a simple mechanism to override the default behavior
+// of exiting on error. Used in testing and to guarantee we reach a required exit
+// for fatal logs. Instead, exit could be a function rather than a method but that
+// would make its use clumsier.
+var logExitFunc func(error)
+
+// exit is called if there is trouble creating or writing log files.
+// It flushes the logs and exits the program; there's no point in hanging around.
+// l.mu is held.
+func (l *loggingT) exit(err error) {
+	fmt.Fprintf(os.Stderr, "log: exiting because of error: %s\n", err)
+	// If logExitFunc is set, we do that instead of exiting.
+	if logExitFunc != nil {
+		logExitFunc(err)
+		return
+	}
+	l.flushAll()
+	os.Exit(2)
+}
+
+// syncBuffer joins a bufio.Writer to its underlying file, providing access to the
+// file's Sync method and providing a wrapper for the Write method that provides log
+// file rotation. There are conflicting methods, so the file cannot be embedded.
+// l.mu is held for all its methods.
+type syncBuffer struct {
+	logger *loggingT
+	*bufio.Writer
+	file     *os.File
+	sev      severity
+	nbytes   uint64 // The number of bytes written to this file
+	maxbytes uint64 // The max number of bytes this syncBuffer.file can hold before cleaning up.
+}
+
+func (sb *syncBuffer) Sync() error {
+	return sb.file.Sync()
+}
+
+// CalculateMaxSize returns the real max size in bytes after considering the default max size and the flag options.
+func CalculateMaxSize() uint64 {
+	if logging.logFile != "" {
+		if logging.logFileMaxSizeMB == 0 {
+			// If logFileMaxSizeMB is zero, we don't have limitations on the log size.
+			return math.MaxUint64
+		}
+		// Flag logFileMaxSizeMB is in MB for user convenience.
+		return logging.logFileMaxSizeMB * 1024 * 1024
+	}
+	// If "log_file" flag is not specified, the target file (sb.file) will be cleaned up when reaches a fixed size.
+	return MaxSize
+}
+
+func (sb *syncBuffer) Write(p []byte) (n int, err error) {
+	if sb.nbytes+uint64(len(p)) >= sb.maxbytes {
+		if err := sb.rotateFile(time.Now(), false); err != nil {
+			sb.logger.exit(err)
+		}
+	}
+	n, err = sb.Writer.Write(p)
+	sb.nbytes += uint64(n)
+	if err != nil {
+		sb.logger.exit(err)
+	}
+	return
+}
+
+// rotateFile closes the syncBuffer's file and starts a new one.
+// The startup argument indicates whether this is the initial startup of klog.
+// If startup is true, existing files are opened for appending instead of truncated.
+func (sb *syncBuffer) rotateFile(now time.Time, startup bool) error {
+	if sb.file != nil {
+		sb.Flush()
+		sb.file.Close()
+	}
+	var err error
+	sb.file, _, err = create(severityName[sb.sev], now, startup)
+	sb.nbytes = 0
+	if err != nil {
+		return err
+	}
+
+	sb.Writer = bufio.NewWriterSize(sb.file, bufferSize)
+
+	if sb.logger.skipLogHeaders {
+		return nil
+	}
+
+	// Write header.
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, "Log file created at: %s\n", now.Format("2006/01/02 15:04:05"))
+	fmt.Fprintf(&buf, "Running on machine: %s\n", host)
+	fmt.Fprintf(&buf, "Binary: Built with %s %s for %s/%s\n", runtime.Compiler, runtime.Version(), runtime.GOOS, runtime.GOARCH)
+	fmt.Fprintf(&buf, "Log line format: [IWEF]mmdd hh:mm:ss.uuuuuu threadid file:line] msg\n")
+	n, err := sb.file.Write(buf.Bytes())
+	sb.nbytes += uint64(n)
+	return err
+}
+
+// bufferSize sizes the buffer associated with each log file. It's large
+// so that log records can accumulate without the logging thread blocking
+// on disk I/O. The flushDaemon will block instead.
+const bufferSize = 256 * 1024
+
+// createFiles creates all the log files for severity from sev down to infoLog.
+// l.mu is held.
+func (l *loggingT) createFiles(sev severity) error {
+	now := time.Now()
+	// Files are created in decreasing severity order, so as soon as we find one
+	// has already been created, we can stop.
+	for s := sev; s >= infoLog && l.file[s] == nil; s-- {
+		sb := &syncBuffer{
+			logger:   l,
+			sev:      s,
+			maxbytes: CalculateMaxSize(),
+		}
+		if err := sb.rotateFile(now, true); err != nil {
+			return err
+		}
+		l.file[s] = sb
+	}
+	return nil
+}
+
+const flushInterval = 5 * time.Second
+
+// flushDaemon periodically flushes the log file buffers.
+func (l *loggingT) flushDaemon() {
+	for range time.NewTicker(flushInterval).C {
+		l.lockAndFlushAll()
+	}
+}
+
+// lockAndFlushAll is like flushAll but locks l.mu first.
+func (l *loggingT) lockAndFlushAll() {
+	l.mu.Lock()
+	l.flushAll()
+	l.mu.Unlock()
+}
+
+// flushAll flushes all the logs and attempts to "sync" their data to disk.
+// l.mu is held.
+func (l *loggingT) flushAll() {
+	// Flush from fatal down, in case there's trouble flushing.
+	for s := fatalLog; s >= infoLog; s-- {
+		file := l.file[s]
+		if file != nil {
+			file.Flush() // ignore error
+			file.Sync()  // ignore error
+		}
+	}
+}
+
+// CopyStandardLogTo arranges for messages written to the Go "log" package's
+// default logs to also appear in the Google logs for the named and lower
+// severities.  Subsequent changes to the standard log's default output location
+// or format may break this behavior.
+//
+// Valid names are "INFO", "WARNING", "ERROR", and "FATAL".  If the name is not
+// recognized, CopyStandardLogTo panics.
+func CopyStandardLogTo(name string) {
+	sev, ok := severityByName(name)
+	if !ok {
+		panic(fmt.Sprintf("log.CopyStandardLogTo(%q): unrecognized severity name", name))
+	}
+	// Set a log format that captures the user's file and line:
+	//   d.go:23: message
+	stdLog.SetFlags(stdLog.Lshortfile)
+	stdLog.SetOutput(logBridge(sev))
+}
+
+// logBridge provides the Write method that enables CopyStandardLogTo to connect
+// Go's standard logs to the logs provided by this package.
+type logBridge severity
+
+// Write parses the standard logging line and passes its components to the
+// logger for severity(lb).
+func (lb logBridge) Write(b []byte) (n int, err error) {
+	var (
+		file = "???"
+		line = 1
+		text string
+	)
+	// Split "d.go:23: message" into "d.go", "23", and "message".
+	if parts := bytes.SplitN(b, []byte{':'}, 3); len(parts) != 3 || len(parts[0]) < 1 || len(parts[2]) < 1 {
+		text = fmt.Sprintf("bad log format: %s", b)
+	} else {
+		file = string(parts[0])
+		text = string(parts[2][1:]) // skip leading space
+		line, err = strconv.Atoi(string(parts[1]))
+		if err != nil {
+			text = fmt.Sprintf("bad line number: %s", b)
+			line = 1
+		}
+	}
+	// printWithFileLine with alsoToStderr=true, so standard log messages
+	// always appear on standard error.
+	logging.printWithFileLine(severity(lb), file, line, true, text)
+	return len(b), nil
+}
+
+// setV computes and remembers the V level for a given PC
+// when vmodule is enabled.
+// File pattern matching takes the basename of the file, stripped
+// of its .go suffix, and uses filepath.Match, which is a little more
+// general than the *? matching used in C++.
+// l.mu is held.
+func (l *loggingT) setV(pc uintptr) Level {
+	fn := runtime.FuncForPC(pc)
+	file, _ := fn.FileLine(pc)
+	// The file is something like /a/b/c/d.go. We want just the d.
+	if strings.HasSuffix(file, ".go") {
+		file = file[:len(file)-3]
+	}
+	if slash := strings.LastIndex(file, "/"); slash >= 0 {
+		file = file[slash+1:]
+	}
+	for _, filter := range l.vmodule.filter {
+		if filter.match(file) {
+			l.vmap[pc] = filter.level
+			return filter.level
+		}
+	}
+	l.vmap[pc] = 0
+	return 0
+}
+
+// Verbose is a boolean type that implements Infof (like Printf) etc.
+// See the documentation of V for more information.
+type Verbose bool
+
+// V reports whether verbosity at the call site is at least the requested level.
+// The returned value is a boolean of type Verbose, which implements Info, Infoln
+// and Infof. These methods will write to the Info log if called.
+// Thus, one may write either
+//	if glog.V(2) { glog.Info("log this") }
+// or
+//	glog.V(2).Info("log this")
+// The second form is shorter but the first is cheaper if logging is off because it does
+// not evaluate its arguments.
+//
+// Whether an individual call to V generates a log record depends on the setting of
+// the -v and --vmodule flags; both are off by default. If the level in the call to
+// V is at least the value of -v, or of -vmodule for the source file containing the
+// call, the V call will log.
+func V(level Level) Verbose {
+	// This function tries hard to be cheap unless there's work to do.
+	// The fast path is two atomic loads and compares.
+
+	// Here is a cheap but safe test to see if V logging is enabled globally.
+	if logging.verbosity.get() >= level {
+		return Verbose(true)
+	}
+
+	// It's off globally but it vmodule may still be set.
+	// Here is another cheap but safe test to see if vmodule is enabled.
+	if atomic.LoadInt32(&logging.filterLength) > 0 {
+		// Now we need a proper lock to use the logging structure. The pcs field
+		// is shared so we must lock before accessing it. This is fairly expensive,
+		// but if V logging is enabled we're slow anyway.
+		logging.mu.Lock()
+		defer logging.mu.Unlock()
+		if runtime.Callers(2, logging.pcs[:]) == 0 {
+			return Verbose(false)
+		}
+		v, ok := logging.vmap[logging.pcs[0]]
+		if !ok {
+			v = logging.setV(logging.pcs[0])
+		}
+		return Verbose(v >= level)
+	}
+	return Verbose(false)
+}
+
+// Info is equivalent to the global Info function, guarded by the value of v.
+// See the documentation of V for usage.
+func (v Verbose) Info(args ...interface{}) {
+	if v {
+		logging.print(infoLog, args...)
+	}
+}
+
+// Infoln is equivalent to the global Infoln function, guarded by the value of v.
+// See the documentation of V for usage.
+func (v Verbose) Infoln(args ...interface{}) {
+	if v {
+		logging.println(infoLog, args...)
+	}
+}
+
+// Infof is equivalent to the global Infof function, guarded by the value of v.
+// See the documentation of V for usage.
+func (v Verbose) Infof(format string, args ...interface{}) {
+	if v {
+		logging.printf(infoLog, format, args...)
+	}
+}
+
+// Info logs to the INFO log.
+// Arguments are handled in the manner of fmt.Print; a newline is appended if missing.
+func Info(args ...interface{}) {
+	logging.print(infoLog, args...)
+}
+
+// InfoDepth acts as Info but uses depth to determine which call frame to log.
+// InfoDepth(0, "msg") is the same as Info("msg").
+func InfoDepth(depth int, args ...interface{}) {
+	logging.printDepth(infoLog, depth, args...)
+}
+
+// Infoln logs to the INFO log.
+// Arguments are handled in the manner of fmt.Println; a newline is appended if missing.
+func Infoln(args ...interface{}) {
+	logging.println(infoLog, args...)
+}
+
+// Infof logs to the INFO log.
+// Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.
+func Infof(format string, args ...interface{}) {
+	logging.printf(infoLog, format, args...)
+}
+
+// Warning logs to the WARNING and INFO logs.
+// Arguments are handled in the manner of fmt.Print; a newline is appended if missing.
+func Warning(args ...interface{}) {
+	logging.print(warningLog, args...)
+}
+
+// WarningDepth acts as Warning but uses depth to determine which call frame to log.
+// WarningDepth(0, "msg") is the same as Warning("msg").
+func WarningDepth(depth int, args ...interface{}) {
+	logging.printDepth(warningLog, depth, args...)
+}
+
+// Warningln logs to the WARNING and INFO logs.
+// Arguments are handled in the manner of fmt.Println; a newline is appended if missing.
+func Warningln(args ...interface{}) {
+	logging.println(warningLog, args...)
+}
+
+// Warningf logs to the WARNING and INFO logs.
+// Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.
+func Warningf(format string, args ...interface{}) {
+	logging.printf(warningLog, format, args...)
+}
+
+// Error logs to the ERROR, WARNING, and INFO logs.
+// Arguments are handled in the manner of fmt.Print; a newline is appended if missing.
+func Error(args ...interface{}) {
+	logging.print(errorLog, args...)
+}
+
+// ErrorDepth acts as Error but uses depth to determine which call frame to log.
+// ErrorDepth(0, "msg") is the same as Error("msg").
+func ErrorDepth(depth int, args ...interface{}) {
+	logging.printDepth(errorLog, depth, args...)
+}
+
+// Errorln logs to the ERROR, WARNING, and INFO logs.
+// Arguments are handled in the manner of fmt.Println; a newline is appended if missing.
+func Errorln(args ...interface{}) {
+	logging.println(errorLog, args...)
+}
+
+// Errorf logs to the ERROR, WARNING, and INFO logs.
+// Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.
+func Errorf(format string, args ...interface{}) {
+	logging.printf(errorLog, format, args...)
+}
+
+// Fatal logs to the FATAL, ERROR, WARNING, and INFO logs,
+// including a stack trace of all running goroutines, then calls os.Exit(255).
+// Arguments are handled in the manner of fmt.Print; a newline is appended if missing.
+func Fatal(args ...interface{}) {
+	logging.print(fatalLog, args...)
+}
+
+// FatalDepth acts as Fatal but uses depth to determine which call frame to log.
+// FatalDepth(0, "msg") is the same as Fatal("msg").
+func FatalDepth(depth int, args ...interface{}) {
+	logging.printDepth(fatalLog, depth, args...)
+}
+
+// Fatalln logs to the FATAL, ERROR, WARNING, and INFO logs,
+// including a stack trace of all running goroutines, then calls os.Exit(255).
+// Arguments are handled in the manner of fmt.Println; a newline is appended if missing.
+func Fatalln(args ...interface{}) {
+	logging.println(fatalLog, args...)
+}
+
+// Fatalf logs to the FATAL, ERROR, WARNING, and INFO logs,
+// including a stack trace of all running goroutines, then calls os.Exit(255).
+// Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.
+func Fatalf(format string, args ...interface{}) {
+	logging.printf(fatalLog, format, args...)
+}
+
+// fatalNoStacks is non-zero if we are to exit without dumping goroutine stacks.
+// It allows Exit and relatives to use the Fatal logs.
+var fatalNoStacks uint32
+
+// Exit logs to the FATAL, ERROR, WARNING, and INFO logs, then calls os.Exit(1).
+// Arguments are handled in the manner of fmt.Print; a newline is appended if missing.
+func Exit(args ...interface{}) {
+	atomic.StoreUint32(&fatalNoStacks, 1)
+	logging.print(fatalLog, args...)
+}
+
+// ExitDepth acts as Exit but uses depth to determine which call frame to log.
+// ExitDepth(0, "msg") is the same as Exit("msg").
+func ExitDepth(depth int, args ...interface{}) {
+	atomic.StoreUint32(&fatalNoStacks, 1)
+	logging.printDepth(fatalLog, depth, args...)
+}
+
+// Exitln logs to the FATAL, ERROR, WARNING, and INFO logs, then calls os.Exit(1).
+func Exitln(args ...interface{}) {
+	atomic.StoreUint32(&fatalNoStacks, 1)
+	logging.println(fatalLog, args...)
+}
+
+// Exitf logs to the FATAL, ERROR, WARNING, and INFO logs, then calls os.Exit(1).
+// Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.
+func Exitf(format string, args ...interface{}) {
+	atomic.StoreUint32(&fatalNoStacks, 1)
+	logging.printf(fatalLog, format, args...)
+}