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Implement CoreFoundation minimal bindings
Add platform/src/cf.rs with:
- Raw extern "C" bindings to CoreFoundation.framework: CFStringCreateWithBytes,
CFRetain, CFRelease, CFStringGetLength, CFStringGetCString
- CFStringRef type alias and CFStringEncoding constants
- CfString RAII wrapper: creates CFStringRef from &str, calls CFRelease on drop
- Clone impl that calls CFRetain for proper reference counting
- Debug/Display impls, len/is_empty helpers, to_string_lossy for round-tripping
- cf_retain/cf_release public wrappers for manual reference counting
- 10 unit tests covering creation, length, empty strings, unicode, emoji,
clone/drop, debug/display formatting, and pointer validity
This is needed for passing string parameters to AppKit APIs (window titles,
menu items, etc).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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crates/platform/src/cf.rs
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crates/platform/src/cf.rs
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//! Minimal CoreFoundation bindings.
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//!
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//! Provides `CFStringRef` creation from Rust strings and RAII reference
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//! counting via [`CfString`]. These bindings are needed for passing string
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//! parameters to AppKit APIs (window titles, menu items, etc).
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//!
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//! # Safety
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//!
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//! This module contains `unsafe` code for FFI with CoreFoundation.
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//! The `platform` crate is one of the few crates where `unsafe` is permitted.
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use std::fmt;
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use std::os::raw::c_void;
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use std::ptr::NonNull;
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// ---------------------------------------------------------------------------
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// Raw FFI types
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// ---------------------------------------------------------------------------
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/// Opaque CoreFoundation string type.
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#[repr(C)]
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pub struct __CFString {
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_private: [u8; 0],
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}
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/// A reference to a CoreFoundation string (immutable).
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pub type CFStringRef = *const __CFString;
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/// CoreFoundation index/size type.
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pub type CFIndex = isize;
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/// CoreFoundation string encoding identifier.
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pub type CFStringEncoding = u32;
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/// CoreFoundation Boolean type.
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pub type CFBoolean = u8;
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/// UTF-8 encoding constant.
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pub const K_CF_STRING_ENCODING_UTF8: CFStringEncoding = 0x0800_0100;
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// ---------------------------------------------------------------------------
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// Raw FFI bindings to CoreFoundation.framework
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// ---------------------------------------------------------------------------
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#[link(name = "CoreFoundation", kind = "framework")]
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extern "C" {
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fn CFStringCreateWithBytes(
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alloc: *const c_void,
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bytes: *const u8,
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num_bytes: CFIndex,
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encoding: CFStringEncoding,
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is_external_representation: CFBoolean,
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) -> CFStringRef;
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fn CFRetain(cf: *const c_void) -> *const c_void;
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fn CFRelease(cf: *const c_void);
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fn CFStringGetLength(string: CFStringRef) -> CFIndex;
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fn CFStringGetCString(
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string: CFStringRef,
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buffer: *mut u8,
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buffer_size: CFIndex,
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encoding: CFStringEncoding,
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) -> CFBoolean;
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}
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// ---------------------------------------------------------------------------
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// Public wrappers for CFRetain / CFRelease
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// ---------------------------------------------------------------------------
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/// Increment the reference count of a CoreFoundation object.
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///
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/// # Safety
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///
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/// `ptr` must point to a valid CoreFoundation object.
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#[inline]
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pub unsafe fn cf_retain(ptr: *const c_void) -> *const c_void {
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CFRetain(ptr)
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}
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/// Decrement the reference count of a CoreFoundation object.
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///
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/// # Safety
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///
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/// `ptr` must point to a valid CoreFoundation object with a positive
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/// reference count. The object may be deallocated after this call.
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#[inline]
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pub unsafe fn cf_release(ptr: *const c_void) {
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CFRelease(ptr);
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}
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// ---------------------------------------------------------------------------
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// CfString — RAII wrapper around CFStringRef
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// ---------------------------------------------------------------------------
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/// An owned CoreFoundation string that calls `CFRelease` on drop.
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///
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/// Created from a Rust `&str` via [`CfString::new`]. The underlying
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/// `CFStringRef` can be borrowed with [`CfString::as_ref`] for passing
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/// to AppKit APIs.
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pub struct CfString(NonNull<__CFString>);
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impl CfString {
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/// Create a `CfString` from a Rust string slice.
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///
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/// Returns `None` if CoreFoundation fails to create the string (should
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/// only happen for extremely large strings or out-of-memory conditions).
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pub fn new(s: &str) -> Option<CfString> {
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let ptr = unsafe {
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CFStringCreateWithBytes(
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std::ptr::null(), // default allocator
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s.as_ptr(),
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s.len() as CFIndex,
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K_CF_STRING_ENCODING_UTF8,
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0, // not external representation
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)
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};
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// CFStringCreateWithBytes returns null on failure.
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NonNull::new(ptr as *mut __CFString).map(CfString)
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}
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/// Return the raw `CFStringRef` for passing to CoreFoundation / AppKit APIs.
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#[inline]
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pub fn as_cf_ref(&self) -> CFStringRef {
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self.0.as_ptr() as CFStringRef
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}
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/// Return the raw pointer as `*const c_void` for APIs that take a generic
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/// CoreFoundation type reference.
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#[inline]
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pub fn as_void_ptr(&self) -> *const c_void {
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self.0.as_ptr() as *const c_void
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}
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/// Get the length of the string in UTF-16 code units.
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pub fn len(&self) -> usize {
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let len = unsafe { CFStringGetLength(self.as_cf_ref()) };
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len as usize
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}
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/// Returns `true` if the string is empty.
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pub fn is_empty(&self) -> bool {
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self.len() == 0
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}
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/// Try to extract the string contents as a Rust `String`.
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///
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/// This is primarily useful for testing and debugging.
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pub fn to_string_lossy(&self) -> String {
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// Allocate a buffer large enough for the UTF-8 representation.
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// CFStringGetCString needs space for a NUL terminator.
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// Worst case: each UTF-16 code unit -> 3 UTF-8 bytes + NUL.
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let max_len = self.len() * 3 + 1;
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let mut buf = vec![0u8; max_len];
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let ok = unsafe {
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CFStringGetCString(
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self.as_cf_ref(),
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buf.as_mut_ptr(),
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buf.len() as CFIndex,
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K_CF_STRING_ENCODING_UTF8,
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)
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};
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if ok != 0 {
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// Find the NUL terminator.
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let nul_pos = buf.iter().position(|&b| b == 0).unwrap_or(buf.len());
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String::from_utf8_lossy(&buf[..nul_pos]).into_owned()
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} else {
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String::new()
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}
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}
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}
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impl Clone for CfString {
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fn clone(&self) -> CfString {
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unsafe { cf_retain(self.as_void_ptr()) };
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CfString(self.0)
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}
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}
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impl Drop for CfString {
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fn drop(&mut self) {
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unsafe { cf_release(self.as_void_ptr()) };
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}
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}
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impl fmt::Debug for CfString {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "CfString(\"{}\")", self.to_string_lossy())
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}
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}
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impl fmt::Display for CfString {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "{}", self.to_string_lossy())
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}
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}
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// SAFETY: CFString is an immutable, reference-counted CoreFoundation type.
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// CFRetain/CFRelease are thread-safe.
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unsafe impl Send for CfString {}
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unsafe impl Sync for CfString {}
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// ---------------------------------------------------------------------------
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// Tests
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// ---------------------------------------------------------------------------
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn create_cfstring_from_str() {
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let s = CfString::new("Hello, world!").expect("should create CFString");
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assert_eq!(s.to_string_lossy(), "Hello, world!");
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}
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#[test]
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fn cfstring_length() {
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let s = CfString::new("abc").expect("should create CFString");
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assert_eq!(s.len(), 3);
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}
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#[test]
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fn cfstring_empty() {
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let s = CfString::new("").expect("should create empty CFString");
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assert!(s.is_empty());
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assert_eq!(s.len(), 0);
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assert_eq!(s.to_string_lossy(), "");
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}
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#[test]
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fn cfstring_unicode() {
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let s = CfString::new("caf\u{00e9}").expect("should handle unicode");
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assert_eq!(s.to_string_lossy(), "caf\u{00e9}");
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// "caf\u{e9}" is 4 UTF-16 code units
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assert_eq!(s.len(), 4);
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}
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#[test]
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fn cfstring_emoji() {
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// Emoji outside BMP: encoded as surrogate pair in UTF-16 (2 code units)
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let s = CfString::new("\u{1F600}").expect("should handle emoji");
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assert_eq!(s.to_string_lossy(), "\u{1F600}");
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assert_eq!(s.len(), 2); // surrogate pair
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}
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#[test]
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fn cfstring_clone_and_drop() {
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let s = CfString::new("test clone").expect("should create");
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let s2 = s.clone();
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assert_eq!(s.to_string_lossy(), s2.to_string_lossy());
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// Both should be droppable without crash (refcount was incremented).
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drop(s);
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assert_eq!(s2.to_string_lossy(), "test clone");
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}
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#[test]
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fn cfstring_debug_format() {
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let s = CfString::new("debug").expect("should create");
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let debug = format!("{:?}", s);
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assert!(debug.contains("CfString"));
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assert!(debug.contains("debug"));
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}
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#[test]
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fn cfstring_display_format() {
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let s = CfString::new("display").expect("should create");
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let display = format!("{}", s);
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assert_eq!(display, "display");
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}
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#[test]
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fn cfstring_as_cf_ref_not_null() {
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let s = CfString::new("ptr test").expect("should create");
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assert!(!s.as_cf_ref().is_null());
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}
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#[test]
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fn cfstring_as_void_ptr_not_null() {
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let s = CfString::new("void test").expect("should create");
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assert!(!s.as_void_ptr().is_null());
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}
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}