strings: builder: add clear (#14328)

vlib/strings/builder.c.v

@@ -50,11 +50,9 @@ pub fn (mut b Builder) write_runes(runes []rune) {
 	}
 }
 
-// write_b appends a single `data` byte to the accumulated buffer
-[deprecated: 'Use write_u8() instead']
-[deprecated_after: '2022-02-11']
-pub fn (mut b Builder) write_b(data u8) {
-	b << data
+// clear clears the buffer contents
+pub fn (mut b Builder) clear() {
+	b = []u8{cap: b.cap}
 }
 
 // write_u8 appends a single `data` byte to the accumulated buffer

vlib/strings/builder.js.v

@@ -18,13 +18,12 @@ pub fn new_builder(initial_size int) Builder {
 	return []u8{cap: initial_size}
 }
 
-[deprecated: 'Use write_u8() instead']
-pub fn (mut b Builder) write_b(data u8) {
+pub fn (mut b Builder) write_byte(data byte) {
 	b << data
 }
 
-pub fn (mut b Builder) write_byte(data byte) {
-	b << data
+pub fn (mut b Builder) clear() {
+	b = []u8{cap: b.cap}
 }
 
 pub fn (mut b Builder) write_u8(data u8) {

vlib/strings/builder_test.js.v

@@ -39,6 +39,9 @@ fn test_sb() {
 	assert last_2 == '56'
 	final_sb := sb.str()
 	assert final_sb == '1234'
+
+	sb.clear()
+	assert sb.str() == ''
 	//}
 }
 

vlib/strings/builder_test.v

@@ -40,6 +40,8 @@ fn test_sb() {
 	final_sb := sb.str()
 	assert final_sb == '1234'
 	//}
+	sb.clear()
+	assert sb.str() == ''
 }
 
 fn test_big_sb() {