bytes: add example with (*Buffer).Cap, (*Buffer).Read, (*Buffer).Read…

…Byte

Change-Id: Ieb107fdfccde9f054491f667a384b16f7af71dea
Reviewed-on: https://go-review.googlesource.com/c/go/+/355289
Run-TryBot: Ian Lance Taylor <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Trust: Cherry Mui <[email protected]>

src/bytes/example_test.go

@@ -37,6 +37,16 @@ func ExampleBuffer_Bytes() {
  // Output: hello world
 }
 
+func ExampleBuffer_Cap() {
+ buf1 := bytes.NewBuffer(make([]byte, 10))
+ buf2 := bytes.NewBuffer(make([]byte, 0, 10))
+ fmt.Println(buf1.Cap())
+ fmt.Println(buf2.Cap())
+ // Output:
+ // 10
+ // 10
+}
+
 func ExampleBuffer_Grow() {
  var b bytes.Buffer
  b.Grow(64)
@@ -67,6 +77,39 @@ func ExampleBuffer_Next() {
  // e
 }
 
+func ExampleBuffer_Read() {
+ var b bytes.Buffer
+ b.Grow(64)
+ b.Write([]byte("abcde"))
+ rdbuf := make([]byte, 1)
+ n, err := b.Read(rdbuf)
+ if err != nil {
+ panic(err)
+ }
+ fmt.Println(n)
+ fmt.Println(b.String())
+ fmt.Println(string(rdbuf))
+ // Output
+ // 1
+ // bcde
+ // a
+}
+
+func ExampleBuffer_ReadByte() {
+ var b bytes.Buffer
+ b.Grow(64)
+ b.Write([]byte("abcde"))
+ c, err := b.ReadByte()
+ if err != nil {
+ panic(err)
+ }
+ fmt.Println(c)
+ fmt.Println(b.String())
+ // Output
+ // 97
+ // bcde
+}
+
 func ExampleCompare() {
  // Interpret Compare's result by comparing it to zero.
  var a, b []byte