Add command-line editing support for interactive pprof (#362)

Add command-line editing support for interactive pprof

This implements basic command-line editing, using
github.com/chzyer/readline. This will not affect the golang
distribution as it uses its own pprof driver, with its own
driver.

Only tested on Linux.
TODO: Implement auto-completion and persistent history.

appveyor.yml

@@ -5,6 +5,7 @@ install:
 
 before_build:
  - go get github.com/ianlancetaylor/demangle
+ - go get github.com/chzyer/readline
 
 build_script:
  - go build github.com/google/pprof

pprof.go

@@ -19,13 +19,88 @@ package main
 import (
 	"fmt"
 	"os"
+	"strings"
 
+	"github.com/chzyer/readline"
 	"github.com/google/pprof/driver"
 )
 
 func main() {
-	if err := driver.PProf(&driver.Options{}); err != nil {
+	if err := driver.PProf(&driver.Options{UI: newUI()}); err != nil {
 		fmt.Fprintf(os.Stderr, "pprof: %v\n", err)
 		os.Exit(2)
 	}
 }
+
+// readlineUI implements the driver.UI interface using the
+// github.com/chzyer/readline library.
+// This is contained in pprof.go to avoid adding the readline
+// dependency in the vendored copy of pprof in the Go distribution,
+// which does not use this file.
+type readlineUI struct {
+	rl *readline.Instance
+}
+
+func newUI() driver.UI {
+	rl, err := readline.New("")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "readline: %v", err)
+		return nil
+	}
+	return &readlineUI{
+		rl: rl,
+	}
+}
+
+// Read returns a line of text (a command) read from the user.
+// prompt is printed before reading the command.
+func (r *readlineUI) ReadLine(prompt string) (string, error) {
+	r.rl.SetPrompt(prompt)
+	return r.rl.Readline()
+}
+
+// Print shows a message to the user.
+// It is printed over stderr as stdout is reserved for regular output.
+func (r *readlineUI) Print(args ...interface{}) {
+	text := fmt.Sprint(args...)
+	if !strings.HasSuffix(text, "\n") {
+		text += "\n"
+	}
+	fmt.Fprint(r.rl.Stderr(), text)
+}
+
+// Print shows a message to the user, colored in red for emphasis.
+// It is printed over stderr as stdout is reserved for regular output.
+func (r *readlineUI) PrintErr(args ...interface{}) {
+	text := fmt.Sprint(args...)
+	if !strings.HasSuffix(text, "\n") {
+		text += "\n"
+	}
+	fmt.Fprint(r.rl.Stderr(), colorize(text))
+}
+
+// colorize the msg using ANSI color escapes.
+func colorize(msg string) string {
+	var red = 31
+	var colorEscape = fmt.Sprintf("\033[0;%dm", red)
+	var colorResetEscape = "\033[0m"
+	return colorEscape + msg + colorResetEscape
+}
+
+// IsTerminal returns whether the UI is known to be tied to an
+// interactive terminal (as opposed to being redirected to a file).
+func (r *readlineUI) IsTerminal() bool {
+	const stdout = 1
+	return readline.IsTerminal(stdout)
+}
+
+// Start a browser on interactive mode.
+func (r *readlineUI) WantBrowser() bool {
+	return r.IsTerminal()
+}
+
+// SetAutoComplete instructs the UI to call complete(cmd) to obtain
+// the auto-completion of cmd, if the UI supports auto-completion at all.
+func (r *readlineUI) SetAutoComplete(complete func(string) string) {
+	// TODO: Implement auto-completion support.
+}