Add an UTF-16 equivalent for strlcpy()

Cargo.lock

@@ -15,6 +15,7 @@ version = "0.1.0"
 dependencies = [
  "nih_plug_derive",
  "vst3-sys",
+ "widestring",
 ]
 
 [[package]]
@@ -96,3 +97,9 @@ source = "git+https://github.com/robbert-vdh/vst3-sys.git?branch=fix/vst3-macro-
 dependencies = [
  "vst3-com",
 ]
+
+[[package]]
+name = "widestring"
+version = "1.0.0-beta.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6f1efe828a707edf85994a4501734ac1c1b9d244cfcf4de235f11c4125ace8f"

Cargo.toml

@@ -12,3 +12,4 @@ members = ["nih_plug_derive", "plugins/gain"]
 nih_plug_derive = { path = "nih_plug_derive" }
 # Upstream currently does not support structs with generics and comments
 vst3-sys = { git = "https://github.com/robbert-vdh/vst3-sys.git", branch = "fix/vst3-macro-generics" }
+widestring = "1.0.0-beta.1"

src/wrapper/util.rs

@@ -16,6 +16,8 @@
 
 use std::cmp;
 use std::os::raw::c_char;
+use vst3_sys::vst::TChar;
+use widestring::U16CString;
 
 /// The equivalent of the `strlcpy()` C function. Copy `src` to `dest` as a null-terminated
 /// C-string. If `dest` does not have enough capacity, add a null terminator at the end to prevent
@@ -33,3 +35,26 @@ pub fn strlcpy(dest: &mut [c_char], src: &str) {
     dest[..copy_len].copy_from_slice(&src_bytes_signed[..copy_len]);
     dest[copy_len] = 0;
 }
+
+/// The same as [strlcpy], but for VST3's fun UTF-16 strings instead.
+pub fn u16strlcpy(dest: &mut [TChar], src: &str) {
+    if dest.is_empty() {
+        return;
+    }
+
+    let src_utf16 = match U16CString::from_str(src) {
+        Ok(s) => s,
+        Err(err) => {
+            nih_debug_assert_failure!("Invalid UTF-16 string: {}", err);
+            return;
+        }
+    };
+    let src_utf16_chars = src_utf16.as_slice();
+    let src_utf16_chars_signed: &[TChar] =
+        unsafe { &*(src_utf16_chars as *const [u16] as *const [TChar]) };
+
+    // Make sure there's always room for a null terminator
+    let copy_len = cmp::min(dest.len() - 1, src_utf16_chars_signed.len());
+    dest[..copy_len].copy_from_slice(&src_utf16_chars_signed[..copy_len]);
+    dest[copy_len] = 0;
+}