From 5640fd8396533d3715840e4cbadcf4828c84067a Mon Sep 17 00:00:00 2001
From: Andrey Smirnov <smirnov.andrey@gmail.com>
Date: Tue, 26 Mar 2019 01:01:50 +0300
Subject: [PATCH] Add Buffer.WriteByte and WriteString methods

These methods are equivalent to `AppendByte` and `AppendString`, but
their signatures are compatible with
[bytes.Buffer](https://godoc.org/bytes#Buffer) and
[bufio.Writer](https://godoc.org/bufio#Writer).

This allows to use `Buffer` where `bytes.Buffer` was expected without
extra cost of wrapping. One example is msgpack library which
expects `Writer` to implement `WriteByte` and `WriteString`, otherwise
it is wrapped which incurs extra allocation:
https://github.com/vmihailenco/msgpack/blob/master/encode.go#L63-L67
---
 buffer/buffer.go      | 18 ++++++++++++++++++
 buffer/buffer_test.go |  2 ++
 2 files changed, 20 insertions(+)

diff --git a/buffer/buffer.go b/buffer/buffer.go
index 7592e8c63..c2e3df8d2 100644
--- a/buffer/buffer.go
+++ b/buffer/buffer.go
@@ -98,6 +98,24 @@ func (b *Buffer) Write(bs []byte) (int, error) {
 	return len(bs), nil
 }
 
+// WriteByte writes a single byte to the Buffer.
+//
+// Error returned is always nil, function signature is compatible
+// with bytes.Buffer and bufio.Writer
+func (b *Buffer) WriteByte(v byte) error {
+	b.AppendByte(v)
+	return nil
+}
+
+// WriteString writes a string to the Buffer.
+//
+// Error returned is always nil, function signature is compatible
+// with bytes.Buffer and bufio.Writer
+func (b *Buffer) WriteString(s string) (int, error) {
+	b.AppendString(s)
+	return len(s), nil
+}
+
 // TrimNewline trims any final "\n" byte from the end of the buffer.
 func (b *Buffer) TrimNewline() {
 	if i := len(b.bs) - 1; i >= 0 {
diff --git a/buffer/buffer_test.go b/buffer/buffer_test.go
index 59bc08a6a..8cf1a37c6 100644
--- a/buffer/buffer_test.go
+++ b/buffer/buffer_test.go
@@ -46,6 +46,8 @@ func TestBufferWrites(t *testing.T) {
 		// Intenationally introduce some floating-point error.
 		{"AppendFloat32", func() { buf.AppendFloat(float64(float32(3.14)), 32) }, "3.14"},
 		{"AppendWrite", func() { buf.Write([]byte("foo")) }, "foo"},
+		{"WriteByte", func() { buf.WriteByte('v') }, "v"},
+		{"WriteString", func() { buf.WriteString("foo") }, "foo"},
 	}
 
 	for _, tt := range tests {