1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
use crate::{CppBox, CppDeletable, DynamicCast, MutRef, Ref, StaticDowncast, StaticUpcast};
use std::ffi::CStr;
use std::fmt;
use std::ops::{Deref, DerefMut};
use std::os::raw::c_char;

/// A mutable pointer to a C++ object (similar to a C++ pointer).
///
/// A `MutPtr` may or may not be owned. If you actually own the object, it's recommended to
/// convert it to `CppBox` using `to_box` method.
///
/// Note that unlike Rust references, `MutPtr` can be freely copied,
/// producing multiple mutable pointers to the same object, which is usually necessary
/// to do when working with C++ libraries.
///
/// `MutPtr` implements operator traits and delegates them
/// to the corresponding C++ operators.
/// This means that you can use `&ptr + value` to access the object's `operator+`.
///
/// `MutPtr` implements `Deref` and `DerefMut`, allowing to call the object's methods
/// directly. In addition, methods of the object's first base class are also directly available
/// thanks to nested `Deref` implementations.
///
/// `MutPtr` can contain a null pointer. `Deref` will panic if attempted to dereference
/// a null pointer.
///
/// If the object provides an iterator interface through `begin()` and `end()` functions,
/// `MutPtr` will implement `IntoIterator`, so you can iterate on it directly.
///
/// ### Safety
///
/// It's not possible to automatically track the ownership of objects possibly managed by C++
/// libraries. The user must ensure that the object is alive while `MutPtr` exists. Note that
/// with `MutPtr`, it's possible to call unsafe C++ code without using any more unsafe Rust code,
/// for example, by using operator traits, so care should be taken when exposing
/// `MutPtr` in a safe interface.
///
/// Null pointers must not be dereferenced.
pub struct MutPtr<T>(*mut T);

/// Creates another pointer to the same object.
impl<T> Clone for MutPtr<T> {
    fn clone(&self) -> Self {
        MutPtr(self.0)
    }
}

/// Creates another pointer to the same object.
impl<T> Copy for MutPtr<T> {}

impl<T> fmt::Debug for MutPtr<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "MutPtr({:?})", self.0)
    }
}

impl<T> MutPtr<T> {
    /// Creates a `MutPtr` from a raw pointer.
    ///
    /// ### Safety
    ///
    /// See type level documentation.
    pub unsafe fn from_raw(ptr: *mut T) -> Self {
        MutPtr(ptr)
    }

    /// Creates a null pointer.
    ///
    /// Note that you can also use `NullPtr` to specify a null pointer to a function accepting
    /// `impl CastInto<MutPtr<_>>`. Unlike `MutPtr`, `NullPtr` is not a generic type, so it will
    /// not cause type inference issues.
    ///
    /// ### Safety
    ///
    /// Null pointers must not be dereferenced. See type level documentation.
    pub unsafe fn null() -> Self {
        MutPtr(std::ptr::null_mut())
    }

    /// Returns the content as a raw const pointer.
    pub fn as_raw_ptr(self) -> *const T {
        self.0
    }

    /// Returns the content as a raw mutable pointer.
    pub fn as_mut_raw_ptr(self) -> *mut T {
        self.0
    }

    /// Returns the content as a const `Ptr`.
    ///
    /// ### Safety
    ///
    /// The operation is safe as long as `self` is valid or null. See type level documentation.
    pub unsafe fn as_ptr(self) -> Ptr<T> {
        Ptr::from_raw(self.0)
    }

    /// Returns the content as a const `Ref`. Returns `None` if `self` is a null pointer.
    ///
    /// ### Safety
    ///
    /// The operation is safe as long as `self` is valid or null. See type level documentation.
    pub unsafe fn as_ref(self) -> Option<Ref<T>> {
        Ref::from_raw(self.0)
    }

    /// Returns the content as a `MutRef`. Returns `None` if `self` is a null pointer.
    ///
    /// ### Safety
    ///
    /// The operation is safe as long as `self` is valid or null. See type level documentation.
    pub unsafe fn as_mut_ref(self) -> Option<MutRef<T>> {
        MutRef::from_raw(self.0)
    }

    /// Returns true if the pointer is null.
    pub fn is_null(self) -> bool {
        self.0.is_null()
    }

    /// Converts the pointer to the base class type `U`.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid or null.
    pub unsafe fn static_upcast<U>(self) -> Ptr<U>
    where
        T: StaticUpcast<U>,
    {
        StaticUpcast::static_upcast(self.as_ptr())
    }

    /// Converts the pointer to the derived class type `U`.
    ///
    /// It's recommended to use `dynamic_cast` instead because it performs a checked conversion.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid and it's type is `U` or inherits from `U`,
    /// of if `self` is a null pointer.
    pub unsafe fn static_downcast<U>(self) -> Ptr<U>
    where
        T: StaticDowncast<U>,
    {
        StaticDowncast::static_downcast(self.as_ptr())
    }

    /// Converts the pointer to the derived class type `U`. Returns `None` if the object's type
    /// is not `U` and doesn't inherit `U`.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid or null.
    pub unsafe fn dynamic_cast<U>(self) -> Ptr<U>
    where
        T: DynamicCast<U>,
    {
        DynamicCast::dynamic_cast(self.as_ptr())
    }

    /// Converts the pointer to the base class type `U`.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid or null.
    pub unsafe fn static_upcast_mut<U>(self) -> MutPtr<U>
    where
        T: StaticUpcast<U>,
    {
        StaticUpcast::static_upcast_mut(self)
    }

    /// Converts the pointer to the derived class type `U`.
    ///
    /// It's recommended to use `dynamic_cast` instead because it performs a checked conversion.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid and it's type is `U` or inherits from `U`,
    /// of if `self` is a null pointer.
    pub unsafe fn static_downcast_mut<U>(self) -> MutPtr<U>
    where
        T: StaticDowncast<U>,
    {
        StaticDowncast::static_downcast_mut(self)
    }

    /// Converts the pointer to the derived class type `U`. Returns `None` if the object's type
    /// is not `U` and doesn't inherit `U`.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid or null.
    pub unsafe fn dynamic_cast_mut<U>(self) -> MutPtr<U>
    where
        T: DynamicCast<U>,
    {
        DynamicCast::dynamic_cast_mut(self)
    }
}

impl<T: CppDeletable> MutPtr<T> {
    /// Converts this pointer to a `CppBox`. Returns `None` if `self`
    /// is a null pointer.
    ///
    /// Use this function to take ownership of the object. This is
    /// the same as `CppBox::new`.
    pub unsafe fn to_box(self) -> Option<CppBox<T>> {
        CppBox::new(self)
    }
}

/// Allows to call member functions of `T` and its base classes directly on the pointer.
impl<T> Deref for MutPtr<T> {
    type Target = T;

    fn deref(&self) -> &T {
        if self.0.is_null() {
            panic!("attempted to deref a null MutPtr<T>");
        }
        unsafe { &(*self.0) }
    }
}

/// Allows to call member functions of `T` and its base classes directly on the pointer.
impl<T> DerefMut for MutPtr<T> {
    fn deref_mut(&mut self) -> &mut T {
        if self.0.is_null() {
            panic!("attempted to deref a null MutPtr<T>");
        }
        unsafe { &mut (*self.0) }
    }
}

impl MutPtr<c_char> {
    /// Creates a `MutPtr<c_char>`, i.e. C++'s `char*` from a `CStr`.
    ///
    /// ### Safety
    ///
    /// The source `str` must be valid
    /// while `MutPtr` exists and while
    /// it's used by the C++ library.
    ///
    /// After passing `str` to `MutPtr`, it's unsafe to use `str` and
    /// any references to the same buffer from Rust because
    /// the memory can be modified through `MutPtr`.
    pub unsafe fn from_c_str(str: &CStr) -> Self {
        Self::from_raw(str.as_ptr() as *mut c_char)
    }

    /// Converts `MutPtr<c_char>`, i.e. C++'s `char*` to a `&CStr`.
    ///
    /// ### Safety
    ///
    /// No guarantees can be made about the validity and lifetime of
    /// the buffer, since it could be produced by a C++ library.
    pub unsafe fn to_c_str<'a>(self) -> &'a CStr {
        CStr::from_ptr(self.0)
    }
}

/// A const pointer to a C++ object (similar to a C++ pointer).
///
/// A `Ptr` may or may not be owned. If you actually own the object, it's recommended to
/// convert it to `CppBox` using `to_box` method.
///
/// Note that unlike Rust references, `Ptr` can be freely copied,
/// producing multiple pointers to the same object, which is usually necessary
/// to do when working with C++ libraries.
///
/// `Ptr` implements operator traits and delegates them
/// to the corresponding C++ operators.
/// This means that you can use `&ptr + value` to access the object's `operator+`.
///
/// `Ptr` implements `Deref`, allowing to call the object's methods
/// directly. In addition, methods of the object's first base class are also directly available
/// thanks to nested `Deref` implementations.
///
/// `Ptr` can contain a null pointer. `Deref` will panic if attempted to dereference
/// a null pointer.
///
/// If the object provides an iterator interface through `begin()` and `end()` functions,
/// `Ptr` will implement `IntoIterator`, so you can iterate on it directly.
///
/// ### Safety
///
/// It's not possible to automatically track the ownership of objects possibly managed by C++
/// libraries. The user must ensure that the object is alive while `Ptr` exists. Note that
/// with `Ptr`, it's possible to call unsafe C++ code without using any more unsafe Rust code,
/// for example, by using operator traits, so care should be taken when exposing
/// `Ptr` in a safe interface.
///
/// Null pointers must not be dereferenced.
pub struct Ptr<T>(*const T);

/// Creates another pointer to the same object.
impl<T> Clone for Ptr<T> {
    fn clone(&self) -> Self {
        Ptr(self.0)
    }
}

/// Creates another pointer to the same object.
impl<T> Copy for Ptr<T> {}

impl<T> fmt::Debug for Ptr<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Ptr({:?})", self.0)
    }
}

impl<T> Ptr<T> {
    /// Creates a `Ptr` from a raw pointer.
    ///
    /// ### Safety
    ///
    /// See type level documentation.
    pub unsafe fn from_raw(ptr: *const T) -> Self {
        Ptr(ptr)
    }

    /// Creates a null pointer.
    ///
    /// Note that you can also use `NullPtr` to specify a null pointer to a function accepting
    /// `impl CastInto<Ptr<_>>`. Unlike `Ptr`, `NullPtr` is not a generic type, so it will
    /// not cause type inference issues.
    ///
    /// ### Safety
    ///
    /// Null pointers must not be dereferenced. See type level documentation.
    pub unsafe fn null() -> Self {
        Ptr(std::ptr::null())
    }

    /// Returns the content as a raw const pointer.
    pub fn as_raw_ptr(self) -> *const T {
        self.0
    }

    /// Returns the content as a const `Ref`. Returns `None` if `self` is a null pointer.
    ///
    /// ### Safety
    ///
    /// The operation is safe as long as `self` is valid or null. See type level documentation.
    pub unsafe fn as_ref(self) -> Option<Ref<T>> {
        Ref::from_raw(self.0)
    }

    /// Returns true if the pointer is null.
    pub fn is_null(self) -> bool {
        self.0.is_null()
    }

    /// Converts the pointer to the base class type `U`.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid or null.
    pub unsafe fn static_upcast<U>(self) -> Ptr<U>
    where
        T: StaticUpcast<U>,
    {
        StaticUpcast::static_upcast(self)
    }

    /// Converts the pointer to the derived class type `U`.
    ///
    /// It's recommended to use `dynamic_cast` instead because it performs a checked conversion.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid and it's type is `U` or inherits from `U`,
    /// of if `self` is a null pointer.
    pub unsafe fn static_downcast<U>(self) -> Ptr<U>
    where
        T: StaticDowncast<U>,
    {
        StaticDowncast::static_downcast(self)
    }

    /// Converts the pointer to the derived class type `U`. Returns `None` if the object's type
    /// is not `U` and doesn't inherit `U`.
    ///
    /// ### Safety
    ///
    /// This operation is safe as long as `self` is valid or null.
    pub unsafe fn dynamic_cast<U>(self) -> Ptr<U>
    where
        T: DynamicCast<U>,
    {
        DynamicCast::dynamic_cast(self)
    }
}

/// Allows to call member functions of `T` and its base classes directly on the pointer.
impl<T> Deref for Ptr<T> {
    type Target = T;

    fn deref(&self) -> &T {
        if self.0.is_null() {
            panic!("attempted to deref a null Ptr<T>");
        }
        unsafe { &(*self.0) }
    }
}

/// Allows to call member functions of `T` and its base classes directly on the pointer.
impl Ptr<c_char> {
    /// Creates a `Ptr<c_char>`, i.e. C++'s `const char*` from a `CStr`.
    ///
    /// ### Safety
    ///
    /// The source `str` must be valid
    /// while `Ptr` exists and while
    /// it's used by the C++ library.
    ///
    /// After passing `str` to `Ptr`, it's unsafe to use `str` and
    /// any references to the same buffer from Rust because
    /// the memory can be modified through `Ptr`.
    pub unsafe fn from_c_str(str: &CStr) -> Self {
        Self::from_raw(str.as_ptr())
    }

    /// Converts `Ptr<c_char>`, i.e. C++'s `const char*` to a `&CStr`.
    ///
    /// ### Safety
    ///
    /// No guarantees can be made about the validity and lifetime of
    /// the buffer, since it could be produced by a C++ library.
    pub unsafe fn to_c_str<'a>(self) -> &'a CStr {
        CStr::from_ptr(self.0)
    }
}

/// A null pointer.
///
/// `NullPtr` implements `CastInto<Ptr<T>>` and `CastInto<MutPtr<T>>`, so it can be
/// passed as argument to functions accepting pointers. It's possible to use `Ptr::null()`
/// as well, but that would require a type annotation.
pub struct NullPtr;

#[test]
fn ptr_deref() {
    let mut i = 42;
    unsafe {
        let ptr: MutPtr<i32> = MutPtr::from_raw(&mut i as *mut i32);
        assert_eq!(*ptr, 42);
    }
}