Added io.writer interface

Author: linkdotnet

CHANGELOG.md

@@ -6,6 +6,10 @@ All notable changes to **ValueStringBuilder** will be documented in this file. T
 
 ## [Unreleased]
 
+### Added
+
+- Implemented the `io.Writer` interface so it can be used with the `fmt` package
+
 ## [0.5.3] - 2022-12-28
 
 ### Changed

README.md

@@ -36,4 +36,30 @@ Also more advanced use cases where you want to insert an arbitrary word at an ar
 sb := NewStringBuilderFromString("Hello World")
 sb.Insert(5, " my dear")
 output := sb.ToString() // Hello my dear World
+```
+
+The `StringBuilder` also implements the `io.Writer` interface so it can be use with `fmt.Fprintf` and friends:
+```golang
+s := &StringBuilder{}
+
+for i := 3; i >= 1; i-- {
+	fmt.Fprintf(s, "%d...", i)
+}
+
+s.Append("lift off")
+fmt.PrintLn(s.ToString()) // Prints 3...2...1...lift off
+```
+
+## Benchmark
+Check out the implementation of the benchmark in the corresponding file. Here are some results:
+```no-class
+goos: darwin
+goarch: arm64
+pkg: github.com/linkdotnet/golang-stringbuilder
+BenchmarkStringBuilderConcat
+BenchmarkStringBuilderConcat-10           343710              3394 ns/op            4352 B/op          5 allocs/op
+BenchmarkStringConcat
+BenchmarkStringConcat-10                 1000000              1113 ns/op            6720 B/op         24 allocs/op
+BenchmarkGoStringBuilderConcat
+BenchmarkGoStringBuilderConcat-10        4204142               278.4 ns/op          1448 B/op          6 allocs/op
 ```

stringbuilder.go

@@ -184,6 +184,15 @@ func (s *StringBuilder) Replace(oldValue string, newValue string) {
 	}
 }
 
+// Implements the io.Writer interface so the StringBuilder can be used with fmt.Printf
+func (s *StringBuilder) Write(p []byte) (int, error) {
+	before := s.Len()
+	s.Append(string(p))
+	delta := before - s.Len()
+
+	return delta, nil
+}
+
 func (s *StringBuilder) grow(lenToAdd int) {
 	// Grow times 2 until lenToAdd fits
 	newLen := len(s.data)

stringbuilder_test.go

@@ -1,6 +1,7 @@
 package Text
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 )
@@ -334,6 +335,19 @@ func TestReplace(t *testing.T) {
 	}
 }
 
+func TestWrite(t *testing.T) {
+	const want = "3...2...1..."
+	s := &StringBuilder{}
+
+	for i := 3; i >= 1; i-- {
+		fmt.Fprintf(s, "%d...", i)
+	}
+
+	if got := s.ToString(); got != want {
+		t.Errorf("StringBuilder.Write() = %v, want %v", got, want)
+	}
+}
+
 func slicesEqual(a []int, b []int) bool {
 	if len(a) != len(b) {
 		return false