1 files changed, 163 insertions, 0 deletions
diff --git a/pkg/log/glog.go b/pkg/log/glog.go
new file mode 100644
index 000000000..58b4052e6
--- /dev/null
+++ b/pkg/log/glog.go
@@ -0,0 +1,163 @@
+// Copyright 2018 Google Inc.
+//
+// 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 log
+
+import (
+	"os"
+	"time"
+)
+
+// GoogleEmitter is a wrapper that emits logs in a format compatible with
+// package github.com/golang/glog.
+type GoogleEmitter struct {
+	// Emitter is the underlying emitter.
+	Emitter
+}
+
+// buffer is a simple inline buffer to avoid churn. The data slice is generally
+// kept to the local byte array, and we avoid having to allocate it on the heap.
+type buffer struct {
+	local [256]byte
+	data  []byte
+}
+
+func (b *buffer) start() {
+	b.data = b.local[:0]
+}
+
+func (b *buffer) String() string {
+	return unsafeString(b.data)
+}
+
+func (b *buffer) write(c byte) {
+	b.data = append(b.data, c)
+}
+
+func (b *buffer) writeAll(d []byte) {
+	b.data = append(b.data, d...)
+}
+
+func (b *buffer) writeOneDigit(d byte) {
+	b.write('0' + d)
+}
+
+func (b *buffer) writeTwoDigits(v int) {
+	v = v % 100
+	b.writeOneDigit(byte(v / 10))
+	b.writeOneDigit(byte(v % 10))
+}
+
+func (b *buffer) writeSixDigits(v int) {
+	v = v % 1000000
+	b.writeOneDigit(byte(v / 100000))
+	b.writeOneDigit(byte((v % 100000) / 10000))
+	b.writeOneDigit(byte((v % 10000) / 1000))
+	b.writeOneDigit(byte((v % 1000) / 100))
+	b.writeOneDigit(byte((v % 100) / 10))
+	b.writeOneDigit(byte(v % 10))
+}
+
+func calculateBytes(v int, pad int) []byte {
+	var d []byte
+	r := 1
+
+	for n := 10; v >= r; n = n * 10 {
+		d = append(d, '0'+byte((v%n)/r))
+		r = n
+	}
+
+	for i := len(d); i < pad; i++ {
+		d = append(d, ' ')
+	}
+
+	for i := 0; i < len(d)/2; i++ {
+		d[i], d[len(d)-(i+1)] = d[len(d)-(i+1)], d[i]
+	}
+	return d
+}
+
+// pid is used for the threadid component of the header.
+//
+// The glog package logger uses 7 spaces of padding. See
+// glob.loggingT.formatHeader.
+var pid = calculateBytes(os.Getpid(), 7)
+
+// caller is faked out as the caller. See FIXME below.
+var caller = []byte("x:0")
+
+// Emit emits the message, google-style.
+func (g GoogleEmitter) Emit(level Level, timestamp time.Time, format string, args ...interface{}) {
+	var b buffer
+	b.start()
+
+	// 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
+
+	// Log level.
+	switch level {
+	case Debug:
+		b.write('D')
+	case Info:
+		b.write('I')
+	case Warning:
+		b.write('W')
+	}
+
+	// Timestamp.
+	_, month, day := timestamp.Date()
+	hour, minute, second := timestamp.Clock()
+	b.writeTwoDigits(int(month))
+	b.writeTwoDigits(int(day))
+	b.write(' ')
+	b.writeTwoDigits(int(hour))
+	b.write(':')
+	b.writeTwoDigits(int(minute))
+	b.write(':')
+	b.writeTwoDigits(int(second))
+	b.write('.')
+	b.writeSixDigits(int(timestamp.Nanosecond() / 1000))
+	b.write(' ')
+
+	// The pid.
+	b.writeAll(pid)
+	b.write(' ')
+
+	// FIXME: The caller, fabricated. This really sucks, but it
+	// is unacceptable to put runtime.Callers() in the hot path.
+	b.writeAll(caller)
+	b.write(']')
+	b.write(' ')
+
+	// User-provided format string, copied.
+	for i := 0; i < len(format); i++ {
+		b.write(format[i])
+	}
+
+	// End with a newline.
+	b.write('\n')
+
+	// Pass to the underlying routine.
+	g.Emitter.Emit(level, timestamp, b.String(), args...)
+}