add start to a logging package.

R=rsc
DELTA=205  (205 added, 0 deleted, 0 changed)
OCL=23448
CL=23478

1 files changed, 135 insertions, 0 deletions

diff --git a/src/lib/log.go b/src/lib/log.go
new file mode 100644
index 000000000..a54ba9f98
--- /dev/null
+++ b/src/lib/log.go
@@ -0,0 +1,135 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Rudimentary logging package. Defines a type, Logger, with simple
+// methods for formatting output to one or two destinations. Also has
+// predefined Loggers accessible through helper functions Stdout[f],
+// Stderr[f], Exit[f], and Crash[f].
+// Exit exits when written to.
+// Crash causes a crash when written to.
+
+package log
+
+import (
+	"fmt";
+	"io";
+	"os";
+	"time";
+)
+
+// Lshortname can be or'd in to cause only the last element of the file name to be printed.
+const (
+	Lok = iota;
+	Lexit;	// terminate execution when written
+	Lcrash;	// crash (panic) when written
+	Lshortname = 1 << 5;
+)
+
+type Logger struct {
+	out0	io.Write;
+	out1	io.Write;
+	flag int;
+}
+
+func NewLogger(out0, out1 io.Write, flag int) *Logger {
+	return &Logger{out0, out1, flag}
+}
+
+var (
+	stdout = NewLogger(os.Stdout, nil, Lok);
+	stderr = NewLogger(os.Stderr, nil, Lok);
+	exit = NewLogger(os.Stderr, nil, Lexit);
+	crash = NewLogger(os.Stderr, nil, Lcrash);
+)
+
+func timestamp(ns int64) string {
+	t := time.SecondsToLocalTime(ns/1e9);
+	// why are time fields private?
+	s := t.RFC1123();
+	return s[5:12] + s[17:25];	// TODO(r): placeholder. this gives "24 Jan 15:50:18"
+}
+
+var shortnames = make(map[string] string)	// cache of short names to avoid allocation.
+
+// The calldepth is provided for generality, although at the moment on all paths it will be 2.
+func (l *Logger) output(calldepth int, s string) {
+	now := time.Nanoseconds();	// get this early.
+	newline := "\n";
+	if len(s) > 0 && s[len(s)-1] == '\n' {
+		newline = ""
+	}
+	pc, file, line, ok := sys.Caller(calldepth);
+	if ok {
+		if l.flag & Lshortname == Lshortname {
+			short, ok := shortnames[file];
+			if !ok {
+				short = file;
+				for i := len(file) - 1; i > 0; i-- {
+					if file[i] == '/' {
+						short = file[i+1:len(file)];
+						shortnames[file] = short;
+						break;
+					}
+				}
+			}
+			file = short;
+		}
+	} else {
+		file = "???";
+		line = 0;
+	}
+	s = fmt.Sprintf("%s %s:%d: %s%s", timestamp(now), file, line, s, newline);
+	io.WriteString(l.out0, s);
+	if l.out1 != nil {
+		io.WriteString(l.out1, s);
+	}
+	switch l.flag & ^Lshortname {
+	case Lcrash:
+		panic("log: fatal error");
+	case Lexit:
+		sys.Exit(1);
+	}
+}
+
+// Basic methods on Logger, analogous to Printf and Print
+func (l *Logger) Logf(format string, v ...) {
+	l.output(2, fmt.Sprintf(format, v))
+}
+
+func (l *Logger) Log(v ...) {
+	l.output(2, fmt.Sprintln(v))
+}
+
+// Helper functions for lightweight simple logging to predefined Loggers.
+func Stdout(v ...) {
+	stdout.output(2, fmt.Sprint(v))
+}
+
+func Stderr(v ...) {
+	stdout.output(2, fmt.Sprintln(v))
+}
+
+func Stdoutf(format string, v ...) {
+	stdout.output(2, fmt.Sprintf(format, v))
+}
+
+func Stderrf(format string, v ...) {
+	stderr.output(2, fmt.Sprintf(format, v))
+}
+
+func Exit(v ...) {
+	exit.output(2, fmt.Sprintln(v))
+}
+
+func Exitf(format string, v ...) {
+	exit.output(2, fmt.Sprintf(format, v))
+}
+
+func Crash(v ...) {
+	crash.output(2, fmt.Sprintln(v))
+}
+
+func Crashf(format string, v ...) {
+	crash.output(2, fmt.Sprintf(format, v))
+}