From 53760b4a74c440b05cf97db5e53f32d66ed47807 Mon Sep 17 00:00:00 2001
From: "Ben L. Titzer" <ben.titzer@gmail.com>
Date: Tue, 23 Jan 2024 11:13:42 -0500
Subject: [PATCH] [lib/util] Add StringBuilder.resize method

---
 lib/util/StringBuilder.v3     |  5 +++++
 test/lib/StringBuilderTest.v3 | 17 +++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/lib/util/StringBuilder.v3 b/lib/util/StringBuilder.v3
index ddba50da0..a210f236f 100644
--- a/lib/util/StringBuilder.v3
+++ b/lib/util/StringBuilder.v3
@@ -268,6 +268,11 @@ class StringBuilder {
 	def outr<R>(f: Range<byte> -> R) -> R {
 		return if(buf != null, f(buf[0 ... length]));
 	}
+	// Resizes the string being built to {nlength}.
+	def resize(nlength: int) -> this {
+		if (nlength > length) grow(nlength);
+		length = nlength;
+	}
 	// Acquire {n} more bytes of internal storage, growing if necessary.
 	private def acquire(n: int) -> int {
 		if (buf == null) buf = Array<byte>.new(n);
diff --git a/test/lib/StringBuilderTest.v3 b/test/lib/StringBuilderTest.v3
index bfb32b9be..c69a5cdf6 100644
--- a/test/lib/StringBuilderTest.v3
+++ b/test/lib/StringBuilderTest.v3
@@ -19,6 +19,7 @@ def X = [
 	T("repeat", test_repeat),
 	T("rjustify", test_rjustify),
 	T("center", test_center),
+	T("resize", test_resize),
 	()
 ];
 
@@ -383,3 +384,19 @@ def test_center(t: LibTest) {
 	buf.center('*', 2, 2);
 	t.assert_string(buf.extract(), "bug");
 }
+
+def test_resize(t: LibTest) {
+	var buf = StringBuilder.new();
+
+	buf.puts("FooBar").resize(3);
+	t.assert_string(buf.extract(), "Foo");
+
+	buf.puts("bank_roll");
+	buf.resize(4).resize(9);
+	t.assert_string(buf.extract(), "bank_roll");
+
+
+	buf.puts("bank");
+	buf.resize(6);
+	t.assert_string(buf.extract(), "bank\x00\x00");
+}