initial commit

src/util.zig

@@ -0,0 +1,24 @@
+const std = @import("std");
+
+/// Convert a string to lowercase using a pre-allocated buffer.
+/// Returns null if the buffer is too small.
+pub fn toLower(s: []const u8, buf: []u8) ?[]const u8 {
+    if (s.len > buf.len) return null;
+    for (s, 0..) |c, i| {
+        buf[i] = std.ascii.toLower(c);
+    }
+    return buf[0..s.len];
+}
+
+test "toLower" {
+    const testing = std.testing;
+    var buf: [64]u8 = undefined;
+
+    try testing.expectEqualStrings("hello", toLower("HELLO", &buf).?);
+    try testing.expectEqualStrings("hello", toLower("hello", &buf).?);
+    try testing.expectEqualStrings("hello123", toLower("HeLLo123", &buf).?);
+
+    // Buffer too small
+    var small_buf: [2]u8 = undefined;
+    try testing.expect(toLower("hello", &small_buf) == null);
+}