feat: Added initial type and first functions

Author: linkdotnet

go.mod

@@ -0,0 +1,3 @@
+module github.com/linkdotnet/golang-stringbuilder
+
+go 1.19

stringbuilder.go

@@ -0,0 +1,66 @@
+package Text
+
+type StringBuilder struct {
+	data     []rune
+	position int
+}
+
+// Creates a new instance of the StringBuilder with preallocated array
+func NewStringBuilder(initialCapacity int) *StringBuilder {
+	return &StringBuilder{data: make([]rune, initialCapacity)}
+}
+
+// Appends a text to the StringBuilder instance
+func (s *StringBuilder) Append(text string) {
+	newLen := s.position + len(text)
+	if newLen > cap(s.data) {
+		s.grow(newLen)
+	}
+
+	copy(s.data[s.position:], []rune(text))
+	s.position = newLen
+}
+
+// Appends a text and a new line character to the StringBuilder instance
+func (s *StringBuilder) AppendLine(text string) {
+	s.Append(text)
+	s.Append("\n")
+}
+
+// Appends a single character to the StringBuilder instance
+func (s *StringBuilder) AppendRune(char rune) {
+	newLen := s.position + 1
+	if newLen > cap(s.data) {
+		s.grow(newLen)
+	}
+
+	s.data[s.position] = char
+	s.position++
+}
+
+// Returns the current length of the represented string
+func (s *StringBuilder) Len() int {
+	return s.position
+}
+
+// Returns the represented string
+func (s *StringBuilder) ToString() string {
+	return string(s.data[:s.position])
+}
+
+func (s *StringBuilder) grow(lenToAdd int) {
+	// Grow times 2 until lenToAdd fits
+	newLen := cap(s.data)
+
+	if cap(s.data) == 0 {
+		newLen = 8
+	}
+
+	for newLen < lenToAdd {
+		newLen = newLen * 2
+	}
+
+	new := make([]rune, newLen)
+	copy(new, s.data)
+	s.data = new
+}

stringbuilder_test.go

@@ -0,0 +1,47 @@
+package Text
+
+import "testing"
+
+func TestAppend(t *testing.T) {
+	const expected string = "Hello World"
+	sb := StringBuilder{}
+
+	sb.Append(expected)
+
+	if result := sb.ToString(); result != expected {
+		t.Errorf("Actual %q, Expected: %q", result, expected)
+	}
+}
+
+func TestLen(t *testing.T) {
+	sb := StringBuilder{}
+
+	sb.Append("1234")
+
+	if len := sb.Len(); len != 4 {
+		t.Errorf("Actual %q, Expected: %q", len, 4)
+	}
+}
+
+func TestAppendLine(t *testing.T) {
+	const expected string = "Hello World\n"
+	sb := NewStringBuilder(100)
+
+	sb.AppendLine("Hello World")
+
+	if result := sb.ToString(); result != expected {
+		t.Errorf("Actual %q, Expected: %q", result, expected)
+	}
+}
+
+func TestAppendRune(t *testing.T) {
+	const expected string = "Hello"
+	sb := NewStringBuilder(100)
+
+	sb.Append("Hell")
+	sb.AppendRune('o')
+
+	if result := sb.ToString(); result != expected {
+		t.Errorf("Actual %q, Expected: %q", result, expected)
+	}
+}