Struct dlopen::symbor::PtrOrNullMut
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pub struct PtrOrNullMut<'lib, T: 'lib> { /* fields omitted */ }
Safe wrapper around mutable pointer.
It is recommended only for obtaining pointers that can have null value.
Methods
impl<'lib, T> PtrOrNullMut<'lib, T>
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fn new(pointer: *mut T) -> PtrOrNullMut<'lib, T>
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Methods from Deref<Target = *mut T>
fn is_null(self) -> bool
1.0.0[src]
Returns true
if the pointer is null.
Examples
Basic usage:
let s: &str = "Follow the rabbit"; let ptr: *const u8 = s.as_ptr(); assert!(!ptr.is_null());
unsafe fn as_ref<'a>(self) -> Option<&'a T>
1.9.0[src]
Returns None
if the pointer is null, or else returns a reference to
the value wrapped in Some
.
Safety
While this method and its mutable counterpart are useful for null-safety, it is important to note that this is still an unsafe operation because the returned value could be pointing to invalid memory.
Additionally, the lifetime 'a
returned is arbitrarily chosen and does
not necessarily reflect the actual lifetime of the data.
Examples
Basic usage:
let ptr: *const u8 = &10u8 as *const u8; unsafe { if let Some(val_back) = ptr.as_ref() { println!("We got back the value: {}!", val_back); } }
unsafe fn offset(self, count: isize) -> *const T
1.0.0[src]
Calculates the offset from a pointer. count
is in units of T; e.g. a
count
of 3 represents a pointer offset of 3 * size_of::<T>()
bytes.
Safety
Both the starting and resulting pointer must be either in bounds or one byte past the end of an allocated object. If either pointer is out of bounds or arithmetic overflow occurs then any further use of the returned value will result in undefined behavior.
Examples
Basic usage:
let s: &str = "123"; let ptr: *const u8 = s.as_ptr(); unsafe { println!("{}", *ptr.offset(1) as char); println!("{}", *ptr.offset(2) as char); }
fn wrapping_offset(self, count: isize) -> *const T
1.16.0[src]
Calculates the offset from a pointer using wrapping arithmetic.
count
is in units of T; e.g. a count
of 3 represents a pointer
offset of 3 * size_of::<T>()
bytes.
Safety
The resulting pointer does not need to be in bounds, but it is
potentially hazardous to dereference (which requires unsafe
).
Always use .offset(count)
instead when possible, because offset
allows the compiler to optimize better.
Examples
Basic usage:
// Iterate using a raw pointer in increments of two elements let data = [1u8, 2, 3, 4, 5]; let mut ptr: *const u8 = data.as_ptr(); let step = 2; let end_rounded_up = ptr.wrapping_offset(6); // This loop prints "1, 3, 5, " while ptr != end_rounded_up { unsafe { print!("{}, ", *ptr); } ptr = ptr.wrapping_offset(step); }
fn offset_to(self, other: *const T) -> Option<isize>
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offset_to
)Calculates the distance between two pointers. The returned value is in
units of T: the distance in bytes is divided by mem::size_of::<T>()
.
If the address different between the two pointers ia not a multiple of
mem::size_of::<T>()
then the result of the division is rounded towards
zero.
This function returns None
if T
is a zero-sized typed.
Examples
Basic usage:
#![feature(offset_to)] fn main() { let a = [0; 5]; let ptr1: *const i32 = &a[1]; let ptr2: *const i32 = &a[3]; assert_eq!(ptr1.offset_to(ptr2), Some(2)); assert_eq!(ptr2.offset_to(ptr1), Some(-2)); assert_eq!(unsafe { ptr1.offset(2) }, ptr2); assert_eq!(unsafe { ptr2.offset(-2) }, ptr1); }
fn is_null(self) -> bool
1.0.0[src]
Returns true
if the pointer is null.
Examples
Basic usage:
let mut s = [1, 2, 3]; let ptr: *mut u32 = s.as_mut_ptr(); assert!(!ptr.is_null());
unsafe fn as_ref<'a>(self) -> Option<&'a T>
1.9.0[src]
Returns None
if the pointer is null, or else returns a reference to
the value wrapped in Some
.
Safety
While this method and its mutable counterpart are useful for null-safety, it is important to note that this is still an unsafe operation because the returned value could be pointing to invalid memory.
Additionally, the lifetime 'a
returned is arbitrarily chosen and does
not necessarily reflect the actual lifetime of the data.
Examples
Basic usage:
let ptr: *mut u8 = &mut 10u8 as *mut u8; unsafe { if let Some(val_back) = ptr.as_ref() { println!("We got back the value: {}!", val_back); } }
unsafe fn offset(self, count: isize) -> *mut T
1.0.0[src]
Calculates the offset from a pointer. count
is in units of T; e.g. a
count
of 3 represents a pointer offset of 3 * size_of::<T>()
bytes.
Safety
The offset must be in-bounds of the object, or one-byte-past-the-end.
Otherwise offset
invokes Undefined Behavior, regardless of whether
the pointer is used.
Examples
Basic usage:
let mut s = [1, 2, 3]; let ptr: *mut u32 = s.as_mut_ptr(); unsafe { println!("{}", *ptr.offset(1)); println!("{}", *ptr.offset(2)); }
fn wrapping_offset(self, count: isize) -> *mut T
1.16.0[src]
Calculates the offset from a pointer using wrapping arithmetic.
count
is in units of T; e.g. a count
of 3 represents a pointer
offset of 3 * size_of::<T>()
bytes.
Safety
The resulting pointer does not need to be in bounds, but it is
potentially hazardous to dereference (which requires unsafe
).
Always use .offset(count)
instead when possible, because offset
allows the compiler to optimize better.
Examples
Basic usage:
// Iterate using a raw pointer in increments of two elements let mut data = [1u8, 2, 3, 4, 5]; let mut ptr: *mut u8 = data.as_mut_ptr(); let step = 2; let end_rounded_up = ptr.wrapping_offset(6); while ptr != end_rounded_up { unsafe { *ptr = 0; } ptr = ptr.wrapping_offset(step); } assert_eq!(&data, &[0, 2, 0, 4, 0]);
unsafe fn as_mut<'a>(self) -> Option<&'a mut T>
1.9.0[src]
Returns None
if the pointer is null, or else returns a mutable
reference to the value wrapped in Some
.
Safety
As with as_ref
, this is unsafe because it cannot verify the validity
of the returned pointer, nor can it ensure that the lifetime 'a
returned is indeed a valid lifetime for the contained data.
Examples
Basic usage:
let mut s = [1, 2, 3]; let ptr: *mut u32 = s.as_mut_ptr(); let first_value = unsafe { ptr.as_mut().unwrap() }; *first_value = 4; println!("{:?}", s); // It'll print: "[4, 2, 3]".
fn offset_to(self, other: *const T) -> Option<isize>
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offset_to
)Calculates the distance between two pointers. The returned value is in
units of T: the distance in bytes is divided by mem::size_of::<T>()
.
If the address different between the two pointers ia not a multiple of
mem::size_of::<T>()
then the result of the division is rounded towards
zero.
This function returns None
if T
is a zero-sized typed.
Examples
Basic usage:
#![feature(offset_to)] fn main() { let mut a = [0; 5]; let ptr1: *mut i32 = &mut a[1]; let ptr2: *mut i32 = &mut a[3]; assert_eq!(ptr1.offset_to(ptr2), Some(2)); assert_eq!(ptr2.offset_to(ptr1), Some(-2)); assert_eq!(unsafe { ptr1.offset(2) }, ptr2); assert_eq!(unsafe { ptr2.offset(-2) }, ptr1); }
Trait Implementations
impl<'lib, T: Debug + 'lib> Debug for PtrOrNullMut<'lib, T>
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impl<'lib, T: Clone + 'lib> Clone for PtrOrNullMut<'lib, T>
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fn clone(&self) -> PtrOrNullMut<'lib, T>
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Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl<'lib, T: Copy + 'lib> Copy for PtrOrNullMut<'lib, T>
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impl<'lib, T> FromRawResult for PtrOrNullMut<'lib, T>
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unsafe fn from_raw_result(
raw_result: Result<PtrOrNull<'a, ()>, Error>
) -> Result<Self, Error>
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raw_result: Result<PtrOrNull<'a, ()>, Error>
) -> Result<Self, Error>
impl<'lib, T> Deref for PtrOrNullMut<'lib, T>
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type Target = *mut T
The resulting type after dereferencing.
fn deref(&self) -> &*mut T
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Dereferences the value.