Initial commit.

This is a sanitized, degoogled version of the internal Google logging package for Go.
It is in effect the Go version of code.google.com/p/google-glog, the C++ original.

Changes from the Go original:
	- changing the package name from log to glog
	- taking out Google-specific details
	- removing some environment variables
diff --git a/README b/README
new file mode 100644
index 0000000..5f9c114
--- /dev/null
+++ b/README
@@ -0,0 +1,44 @@
+glog
+====
+
+Leveled execution logs for Go.
+
+This is an efficient pure Go implementation of leveled logs in the
+manner of the open source C++ package
+	http://code.google.com/p/google-glog
+
+By binding methods to booleans it is possible to use the log package
+without paying the expense of evaluating the arguments to the log.
+Through the -vmodule flag, the package also provides fine-grained
+control over logging at the file level.
+
+The comment from glog.go introduces the ideas:
+
+	Package glog 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")
+
+
+The repository contains an open source version of the log package
+used inside Google. The master copy of the source lives inside
+Google, not here. The code in this repo is for export only and is not itself
+under development. Feature requests will be ignored.
+
+Send bug reports to golang-nuts@googlegroups.com.
diff --git a/README.md b/README.md
deleted file mode 100644
index b0397ed..0000000
--- a/README.md
+++ /dev/null
@@ -1,4 +0,0 @@
-glog
-====
-
-Leveled execution logs
diff --git a/glog.go b/glog.go
new file mode 100644
index 0000000..6bf2170
--- /dev/null
+++ b/glog.go
@@ -0,0 +1,1013 @@
+// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
+//
+// Copyright 2013 The Go Authors.  All rights reserved.
+// http://github.com/golang/glog
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Package glog 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")
+//
+package glog
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"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
+
+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, _ := path.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() {
+	flag.BoolVar(&logging.toStderr, "logtostderr", false, "log to standard error instead of files")
+	flag.BoolVar(&logging.alsoToStderr, "alsologtostderr", false, "log to standard error as well as files")
+	flag.Var(&logging.verbosity, "v", "log level for V logs")
+	flag.Var(&logging.stderrThreshold, "stderrthreshold", "logs at or above this threshold go to stderr")
+	flag.Var(&logging.vmodule, "vmodule", "comma-separated list of pattern=N settings for file-filtered logging")
+	flag.Var(&logging.traceLocation, "log_backtrace_at", "when logging hits line file:N, emit a stack trace")
+
+	// Default stderrThreshold is ERROR.
+	logging.stderrThreshold = errorLog
+
+	logging.setVState(0, nil, false)
+	go logging.flushDaemon()
+}
+
+// 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/
+}
+
+// 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.
+	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.
+
+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) *buffer {
+	// Lmmdd hh:mm:ss.uuuuuu threadid file:line]
+	now := timeNow()
+	_, file, line, ok := runtime.Caller(3) // It's always the same number of frames to the user's call.
+	if !ok {
+		file = "???"
+		line = 1
+	} else {
+		slash := strings.LastIndex(file, "/")
+		if slash >= 0 {
+			file = file[slash+1:]
+		}
+	}
+	if line < 0 {
+		line = 0 // not a real line number, but acceptable to someDigits
+	}
+	if s > fatalLog {
+		s = infoLog // for safety.
+	}
+	buf := l.getBuffer()
+
+	// 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()
+	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)
+	buf.tmp[21] = ' '
+	buf.nDigits(5, 22, pid) // TODO: should be TID
+	buf.tmp[27] = ' '
+	buf.Write(buf.tmp[:28])
+	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 a zero-prefixed n-digit integer at buf.tmp[i].
+func (buf *buffer) nDigits(n, i, d int) {
+	for j := n - 1; j >= 0; j-- {
+		buf.tmp[i+j] = digits[d%10]
+		d /= 10
+	}
+}
+
+// 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 := l.header(s)
+	fmt.Fprintln(buf, args...)
+	l.output(s, buf)
+}
+
+func (l *loggingT) print(s severity, args ...interface{}) {
+	buf := l.header(s)
+	fmt.Fprint(buf, args...)
+	if buf.Bytes()[buf.Len()-1] != '\n' {
+		buf.WriteByte('\n')
+	}
+	l.output(s, buf)
+}
+
+func (l *loggingT) printf(s severity, format string, args ...interface{}) {
+	buf := l.header(s)
+	fmt.Fprintf(buf, format, args...)
+	if buf.Bytes()[buf.Len()-1] != '\n' {
+		buf.WriteByte('\n')
+	}
+	l.output(s, buf)
+}
+
+// output writes the data to the log files and releases the buffer.
+func (l *loggingT) output(s severity, buf *buffer) {
+	l.mu.Lock()
+	if l.traceLocation.isSet() {
+		_, file, line, ok := runtime.Caller(3) // It's always the same number of frames to the user's call (same as header).
+		if ok && l.traceLocation.match(file, line) {
+			buf.Write(stacks(false))
+		}
+	}
+	data := buf.Bytes()
+	if l.toStderr {
+		os.Stderr.Write(data)
+	} else {
+		if 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 {
+		// Make sure we see the trace for the current goroutine on standard error.
+		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
+}
+
+func (sb *syncBuffer) Sync() error {
+	return sb.file.Sync()
+}
+
+func (sb *syncBuffer) Write(p []byte) (n int, err error) {
+	if sb.nbytes+uint64(len(p)) >= MaxSize {
+		if err := sb.rotateFile(time.Now()); 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.
+func (sb *syncBuffer) rotateFile(now time.Time) error {
+	if sb.file != nil {
+		sb.Flush()
+		sb.file.Close()
+	}
+	var err error
+	sb.file, _, err = create(severityName[sb.sev], now)
+	sb.nbytes = 0
+	if err != nil {
+		return err
+	}
+
+	sb.Writer = bufio.NewWriterSize(sb.file, bufferSize)
+
+	// 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,
+		}
+		if err := sb.rotateFile(now); err != nil {
+			return err
+		}
+		l.file[s] = sb
+	}
+	return nil
+}
+
+const flushInterval = 30 * 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
+		}
+	}
+}
+
+// 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 path.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...)
+}
+
+// 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...)
+}
+
+// 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...)
+}
+
+// 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...)
+}
+
+// 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...)
+}
diff --git a/glog_file.go b/glog_file.go
new file mode 100644
index 0000000..ce4aa23
--- /dev/null
+++ b/glog_file.go
@@ -0,0 +1,151 @@
+// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
+//
+// Copyright 2013 The Go Authors.  All rights reserved.
+// http://github.com/golang/glog
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// File I/O for logs.
+
+package glog
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"os/user"
+	"path"
+	"strings"
+	"sync"
+	"time"
+)
+
+// MaxSize is the maximum size of a log file in bytes.
+var MaxSize uint64 = 1024 * 1024 * 1800
+
+// logDirs lists the candidate directories for new log files.
+var logDirs []string
+
+// If non-empty, overrides the choice of directory in which to write logs.
+// See createLogDirs for the full list of possible destinations.
+var log_dir = flag.String("log_dir", "", "If non-empty, write log files in this directory")
+
+func createLogDirs() {
+	candidates := []string{
+		*log_dir,
+
+		// Explicitly-supplied temp dirs
+		os.Getenv("TMPDIR"),
+		os.Getenv("TMP"),
+
+		// If all else fails
+		"/tmp",
+	}
+	for _, dir := range candidates {
+		if len(dir) == 0 {
+			continue
+		}
+		if dir[0] != '/' {
+			dir = "/" + dir
+		}
+		logDirs = append(logDirs, dir)
+	}
+}
+
+var (
+	pid      = os.Getpid()
+	program  = path.Base(os.Args[0])
+	host     = "unknownhost"
+	userName = "unknownuser"
+)
+
+func init() {
+	h, err := os.Hostname()
+	if err == nil {
+		host = shortHostname(h)
+	}
+
+	current, err := user.Current()
+	if err == nil {
+		userName = current.Username
+	}
+}
+
+// shortHostname returns its argument, truncating at the first period.
+// For instance, given "www.google.com" it returns "www".
+func shortHostname(hostname string) string {
+	if i := strings.Index(hostname, "."); i >= 0 {
+		return hostname[:i]
+	}
+	return hostname
+}
+
+// logName returns a new log file name containing tag, with start time t, and
+// the name for the symlink for tag.
+func logName(tag string, t time.Time) (name, link string) {
+	name = fmt.Sprintf("%s.%s.%s.log.%s.%04d%02d%02d-%02d%02d%02d.%d",
+		program,
+		host,
+		userName,
+		tag,
+		t.Year(),
+		t.Month(),
+		t.Day(),
+		t.Hour(),
+		t.Minute(),
+		t.Second(),
+		pid)
+	return name, program + "." + tag
+}
+
+var onceLogDirs sync.Once
+
+// create creates a new log file and returns the file and its filename, which
+// contains tag ("INFO", "FATAL", etc.) and t.  If the file is created
+// successfully, create also attempts to update the symlink for that tag, ignoring
+// errors.
+func create(tag string, t time.Time) (f *os.File, filename string, err error) {
+	onceLogDirs.Do(createLogDirs)
+	if len(logDirs) == 0 {
+		return nil, "", errors.New("log: no log dirs")
+	}
+	name, link := logName(tag, t)
+	var lastErr error
+	for _, dir := range logDirs {
+		fname := path.Join(dir, name)
+		f, err := os.Create(fname)
+		if err == nil {
+			symlink := path.Join(dir, link)
+			os.Remove(symlink)         // ignore err
+			os.Symlink(fname, symlink) // ignore err
+			return f, fname, nil
+		}
+		lastErr = err
+	}
+	return nil, "", fmt.Errorf("log: cannot create log: %v", lastErr)
+}
diff --git a/glog_test.go b/glog_test.go
new file mode 100644
index 0000000..1efd5fb
--- /dev/null
+++ b/glog_test.go
@@ -0,0 +1,349 @@
+// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
+//
+// Copyright 2013 The Go Authors.  All rights reserved.
+// http://github.com/golang/glog
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package glog
+
+import (
+	"bytes"
+	"fmt"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+)
+
+// Test that shortHostname works as advertised.
+func TestShortHostname(t *testing.T) {
+	for hostname, expect := range map[string]string{
+		"":                     "",
+		"host":                 "host",
+		"host.google.com":      "host",
+	} {
+		if got := shortHostname(hostname); expect != got {
+			t.Errorf("shortHostname(%q): expected %q, got %q", hostname, expect, got)
+		}
+	}
+}
+
+// flushBuffer wraps a bytes.Buffer to satisfy flushSyncWriter.
+type flushBuffer struct {
+	bytes.Buffer
+}
+
+func (f *flushBuffer) Flush() error {
+	return nil
+}
+
+func (f *flushBuffer) Sync() error {
+	return nil
+}
+
+// swap sets the log writers and returns the old array.
+func (l *loggingT) swap(writers [numSeverity]flushSyncWriter) (old [numSeverity]flushSyncWriter) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	old = l.file
+	for i, w := range writers {
+		logging.file[i] = w
+	}
+	return
+}
+
+// newBuffers sets the log writers to all new byte buffers and returns the old array.
+func (l *loggingT) newBuffers() [numSeverity]flushSyncWriter {
+	return l.swap([numSeverity]flushSyncWriter{new(flushBuffer), new(flushBuffer), new(flushBuffer), new(flushBuffer)})
+}
+
+// contents returns the specified log value as a string.
+func contents(s severity) string {
+	return logging.file[s].(*flushBuffer).String()
+}
+
+// contains reports whether the string is contained in the log.
+func contains(s severity, str string, t *testing.T) bool {
+	return strings.Contains(contents(s), str)
+}
+
+// setFlags configures the logging flags how the test expects them.
+func setFlags() {
+	logging.toStderr = false
+}
+
+// Test that Info works as advertised.
+func TestInfo(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	Info("test")
+	if !contains(infoLog, "I", t) {
+		t.Errorf("Info has wrong character: %q", contents(infoLog))
+	}
+	if !contains(infoLog, "test", t) {
+		t.Error("Info failed")
+	}
+}
+
+// Test that the header has the correct format.
+func TestHeader(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	defer func(previous func() time.Time) { timeNow = previous }(timeNow)
+	timeNow = func() time.Time {
+		return time.Date(2006, 1, 2, 15, 4, 5, .678901e9, time.Local)
+	}
+	Info("test")
+	var line, pid int
+	n, err := fmt.Sscanf(contents(infoLog), "I0102 15:04:05.678901 %d glog_test.go:%d] test\n", &pid, &line)
+	if n != 2 || err != nil {
+		t.Errorf("log format error: %d elements, error %s:\n%s", n, err, contents(infoLog))
+	}
+}
+
+// Test that an Error log goes to Warning and Info.
+// Even in the Info log, the source character will be E, so the data should
+// all be identical.
+func TestError(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	Error("test")
+	if !contains(errorLog, "E", t) {
+		t.Errorf("Error has wrong character: %q", contents(errorLog))
+	}
+	if !contains(errorLog, "test", t) {
+		t.Error("Error failed")
+	}
+	str := contents(errorLog)
+	if !contains(warningLog, str, t) {
+		t.Error("Warning failed")
+	}
+	if !contains(infoLog, str, t) {
+		t.Error("Info failed")
+	}
+}
+
+// Test that a Warning log goes to Info.
+// Even in the Info log, the source character will be W, so the data should
+// all be identical.
+func TestWarning(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	Warning("test")
+	if !contains(warningLog, "W", t) {
+		t.Errorf("Warning has wrong character: %q", contents(warningLog))
+	}
+	if !contains(warningLog, "test", t) {
+		t.Error("Warning failed")
+	}
+	str := contents(warningLog)
+	if !contains(infoLog, str, t) {
+		t.Error("Info failed")
+	}
+}
+
+// Test that a V log goes to Info.
+func TestV(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	logging.verbosity.Set("2")
+	defer logging.verbosity.Set("0")
+	V(2).Info("test")
+	if !contains(infoLog, "I", t) {
+		t.Errorf("Info has wrong character: %q", contents(infoLog))
+	}
+	if !contains(infoLog, "test", t) {
+		t.Error("Info failed")
+	}
+}
+
+// Test that a vmodule enables a log in this file.
+func TestVmoduleOn(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	logging.vmodule.Set("glog_test=2")
+	defer logging.vmodule.Set("")
+	if !V(1) {
+		t.Error("V not enabled for 1")
+	}
+	if !V(2) {
+		t.Error("V not enabled for 2")
+	}
+	if V(3) {
+		t.Error("V enabled for 3")
+	}
+	V(2).Info("test")
+	if !contains(infoLog, "I", t) {
+		t.Errorf("Info has wrong character: %q", contents(infoLog))
+	}
+	if !contains(infoLog, "test", t) {
+		t.Error("Info failed")
+	}
+}
+
+// Test that a vmodule of another file does not enable a log in this file.
+func TestVmoduleOff(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	logging.vmodule.Set("notthisfile=2")
+	defer logging.vmodule.Set("")
+	for i := 1; i <= 3; i++ {
+		if V(Level(i)) {
+			t.Errorf("V enabled for %d", i)
+		}
+	}
+	V(2).Info("test")
+	if contents(infoLog) != "" {
+		t.Error("V logged incorrectly")
+	}
+}
+
+// vGlobs are patterns that match/don't match this file at V=2.
+var vGlobs = map[string]bool{
+	// Easy to test the numeric match here.
+	"glog_test=1": false, // If -vmodule sets V to 1, V(2) will fail.
+	"glog_test=2": true,
+	"glog_test=3": true, // If -vmodule sets V to 1, V(3) will succeed.
+	// These all use 2 and check the patterns. All are true.
+	"*=2":          true,
+	"?l*=2":         true,
+	"????_*=2":      true,
+	"??[mno]?_*t=2": true,
+	// These all use 2 and check the patterns. All are false.
+	"*x=2":         false,
+	"m*=2":         false,
+	"??_*=2":       false,
+	"?[abc]?_*t=2": false,
+}
+
+// Test that vmodule globbing works as advertised.
+func testVmoduleGlob(pat string, match bool, t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	defer logging.vmodule.Set("")
+	logging.vmodule.Set(pat)
+	if V(2) != Verbose(match) {
+		t.Errorf("incorrect match for %q: got %t expected %t", pat, V(2), match)
+	}
+}
+
+// Test that a vmodule globbing works as advertised.
+func TestVmoduleGlob(t *testing.T) {
+	for glob, match := range vGlobs {
+		testVmoduleGlob(glob, match, t)
+	}
+}
+
+func TestRollover(t *testing.T) {
+	setFlags()
+	var err error
+	defer func(previous func(error)) { logExitFunc = previous }(logExitFunc)
+	logExitFunc = func(e error) {
+		err = e
+	}
+	defer func(previous uint64) { MaxSize = previous }(MaxSize)
+	MaxSize = 512
+
+	Info("x") // Be sure we have a file.
+	info, ok := logging.file[infoLog].(*syncBuffer)
+	if !ok {
+		t.Fatal("info wasn't created")
+	}
+	if err != nil {
+		t.Fatalf("info has initial error: %v", err)
+	}
+	fname0 := info.file.Name()
+	Info(strings.Repeat("x", int(MaxSize))) // force a rollover
+	if err != nil {
+		t.Fatalf("info has error after big write: %v", err)
+	}
+
+	// Make sure the next log file gets a file name with a different
+	// time stamp.
+	//
+	// TODO: determine whether we need to support subsecond log
+	// rotation.  C++ does not appear to handle this case (nor does it
+	// handle Daylight Savings Time properly).
+	time.Sleep(1 * time.Second)
+
+	Info("x") // create a new file
+	if err != nil {
+		t.Fatalf("error after rotation: %v", err)
+	}
+	fname1 := info.file.Name()
+	if fname0 == fname1 {
+		t.Errorf("info.f.Name did not change: %v", fname0)
+	}
+	if info.nbytes >= MaxSize {
+		t.Errorf("file size was not reset: %d", info.nbytes)
+	}
+}
+
+func TestLogBacktraceAt(t *testing.T) {
+	setFlags()
+	defer logging.swap(logging.newBuffers())
+	// The peculiar style of this code simplifies line counting and maintenance of the
+	// tracing block below.
+	var infoLine string
+	setTraceLocation := func(file string, line int, ok bool, delta int) {
+		if !ok {
+			t.Fatal("could not get file:line")
+		}
+		if i := strings.LastIndex(file, "/"); i >= 0 {
+			file = file[i+1:]
+		}
+		infoLine = fmt.Sprintf("%s:%d", file, line+delta)
+		err := logging.traceLocation.Set(infoLine)
+		if err != nil {
+			t.Fatal("error setting log_backtrace_at: ", err)
+		}
+	}
+	{
+		// Start of tracing block. These lines know about each other's relative position.
+		_, file, line, ok := runtime.Caller(0)
+		setTraceLocation(file, line, ok, +2) // Two lines between Caller and Info calls.
+		Info("we want a stack trace here")
+	}
+	numAppearances := strings.Count(contents(infoLog), infoLine)
+	if numAppearances < 2 {
+		// Need 2 appearances, one in the log header and one in the trace:
+		//   log_test.go:281: I0511 16:36:06.952398 02238 log_test.go:280] we want a stack trace here
+		//   ...
+		//   github.com/glog/glog_test.go:280 (0x41ba91)
+		//   ...
+		// We could be more precise but that would require knowing the details
+		// of the traceback format, which may not be dependable.
+		t.Fatal("got no trace back; log is ", contents(infoLog))
+	}
+}
+
+func BenchmarkHeader(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		logging.putBuffer(logging.header(infoLog))
+	}
+}
\ No newline at end of file