client/cmd/rpc: RPC CLI

common/indented/writer.go

Index: common/indented/writer.go
diff --git a/common/indented/writer.go b/common/indented/writer.go
new file mode 100644
index 0000000000000000000000000000000000000000..d4bf81d52070b56fdf66a83a6f11847d638b9aba
--- /dev/null
+++ b/common/indented/writer.go
@@ -0,0 +1,77 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package indented
+
+import (
+	"bytes"
+	"io"
+)
+
+// Writer inserts indentation before each line.
+type Writer struct {
+	io.Writer      // underlying writer.
+	Level      int // number of times \t must be inserted before each line.
+	insideLine bool
+}
+
+var indentation []byte
+
+func init() {
+	indentation = make([]byte, 256)
+	for i := range indentation {
+		indentation[i] = '\t'
+	}
+}
+
+// Write writes data inserting a newline before each line.
+// Panics if w.Indent is outside of [0, 256) range.
+func (w *Writer) Write(data []byte) (n int, err error) {
+	// Do not print indentation if there is no data.
+
+	for len(data) > 0 {
+		var printUntil int
+		endsWithNewLine := false
+
+		lineBeginning := !w.insideLine
+		if data[0] == '\n' && lineBeginning {
+			// This is a blank line. Do not indent it, just print as is.
+			printUntil = 1
+		} else {
+			if lineBeginning {
+				// Print indentation.
+				w.Writer.Write(indentation[:w.Level])
+				w.insideLine = true
+			}
+
+			lineEnd := bytes.IndexRune(data, '\n')
+			if lineEnd < 0 {
+				// Print the whole thing.
+				printUntil = len(data)
+			} else {
+				// Print until the newline inclusive.
+				printUntil = lineEnd + 1
+				endsWithNewLine = true
+			}
+		}
+		toPrint := data[:printUntil]
+		data = data[printUntil:]
+
+		// Assertion: none of the runes in toPrint
+		// can be newline except the last rune.
+		// The last rune is newline iff endsWithNewLine==true.
+
+		m, err := w.Writer.Write(toPrint)
+		n += m
+
+		if m == len(toPrint) && endsWithNewLine {
+			// We've printed the newline, so we are the line beginning again.
+			w.insideLine = false
+		}
+		if err != nil {
+			return n, err
+		}
+	}
+	return n, nil
+}