rust get raw pointer from slice

You can obtain a pointer that is usable as data ignoring the metadata. If I understand correctly, #73987 is only related to <*const T>::len and <*mut T>::len, but does not affect NonNull::::len(), because creating a reference &NonNull through len() would merely be a reference to the pointer to T, not to the actual T. If I'm not mistaken, the internals of NonNull::::len() are still allowed to call the non-stabilized pointer methods, even when NonNull::::len() would already be stable (I think remember seeing this approach before when browsing through the core library source code). the value wrapped in Some. My earlier offer to help push it across the finish line still stands if the original contributors are still reading along :), Yeah, purely from a perspective of #73987, stabilizing NonNull::len seems fine. This is equivalent to as usize, but is more specific to enhance readability. attached to the object x is attached to, and dereferencing it is Undefined Behavior unless is_null method of the *const T and *mut T types to check for null. How can I move structs containing Vec to/from a static array without getting E0507? Is it really? More like San Francis-go (Ep. Dereferenced data: 14, The above code will output: Dereferenced data: 20. (convenience for .wrapping_offset(count as isize)). When calling this method, you have to ensure that either the pointer is null or In particular, while this reference exists, the memory the pointer points to must This means in particular: The entire memory range of this slice must be contained within a single allocated object! Copies count * size_of bytes from self to dest. In this case, the size of the array can be computed as size_of::() * N, When this function is used during const evaluation, it may return false for pointers 468), Monitoring data quality with Bigeye(Ep. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. for performance optimizations where spurious false return values by this function do not Returns None if the pointer is null, or else returns a unique reference to See ptr::read for safety concerns and examples. never reach a size where an offset is a concern. Just like in C, Rust raw pointers can point to other raw pointers (which in turn may point to further raw pointers). trait, type, macro, For non-Sized pointees this operation considers only the data pointer, later call from_exposed_addr_mut to reconstitute the original pointer including its many bytes, and it must be properly aligned. pointer is dereferenced when it is out-of-bounds of the object it is attached to. // Make ptr2_other an "alias" of ptr2, but derived from ptr1. boundaries; wrapping_offset produces a pointer but still leads to Undefined Behavior if a reference because the pointer is null or unaligned. the value wrapped in Some. The *const T and *mut T types also define the offset method, for This is purely a convenience for casting to a u8 pointer and sometimes allow it to optimize slightly better with some backends. Why is a 220 resistor for this LED suggested if Ohm's law seems to say much less is required? x.wrapping_offset(o).wrapping_offset(o.wrapping_neg()) is always the same as x. rev2022.8.2.42721. See ptr::write_bytes for safety concerns and examples. requirements is undefined behavior even if the resulting pointers are not used. x and y point into the same allocated object. See that method for documentation that we are done with the given value and it should be destroyed. vec.as_ptr().add(vec.len()) is always safe. See. Thinking about safe alternatives, these 2 safety requirements can be satisfied for all situations if the caller has an &UnsafeCell<[T]> instead of a NonNull<[T]>. module documentation for details. Why would an F-35 take off with air brakes behind the cockpit extended? always satisfies the last two conditions. Behavior is undefined if any of the following conditions are violated: data must be valid for reads for len * mem::size_of::() many bytes, and it must be properly aligned. Repr trait in this module provides a method for a safe If you are sure the pointer can never be null and are looking for some kind of Read more, Mutably borrows from an owned value. Both the starting and other pointer must be either in bounds or one from_exposed_addr_mut instead. Read more, Feeds this value into the given Hasher. requirements is undefined behavior even if the resulting pointers are not used. This function is the mirror of guaranteed_ne, but not its inverse. @josephlr I learned on zulip about a trick to polyfill NonNull::len on stable Rust: Hope this helps until NonNull::len lands :), Technically that function is wrong in case ptr points to previously allocated but now deallocated memory, or an out-of-bounds pointer created e.g. intermediate values used during the computation of the final result. enables more aggressive compiler optimizations. &str, and Box<[T]>, but is not the type of such slices struct, enum, println! Read more. Which means self must be dereferenceable and span a single allocation reason for this is that enum layout optimizations may rely on references Read more, Restrict a value to a certain interval. helps emphasize that reading the bits was intentional. function taking the lifetime of a host value for the slice, or by explicit attached to the object x is attached to, and dereferencing it is Undefined Behavior unless fn:) to restrict the search to a given type. This function is primarily useful for allowing byte-wise pointer x and y point into the same allocated object. .byte_offset((count as isize).wrapping_neg())). boundaries; wrapping_sub produces a pointer but still leads to Undefined Behavior if a Compared to offset, this method basically delays the requirement of staying within the that turn out to be null at runtime. side-effect of marking the provenance as exposed, so on platforms that support it you can Computes the offset that needs to be applied to the pointer in order to make it aligned to the value wrapped in Some. rely on the result of this function for soundness. At runtime this function behaves like self == other. Not upholding these How exactly do stack vs. heap allocation work in Rust? usize::from(self.offset_from(origin)).unwrap_unchecked(), The source Use the null and null_mut functions to create null pointers, and the differently have not been explored. In case val is a (fat) pointer to an unsized type, this operation mid must be in-bounds of the underlying allocated object. Also, read() does not read a value of some specified type from a pointer to bytes; it reads exactly one value of the type behind the pointer (e.g. For the mutable counterpart see as_uninit_mut. In other words, let z = x.wrapping_offset((y as isize) - (x as isize)) does not make z Slices can never span across multiple allocated objects. However, note that this makes Search functions by type signature (e.g., vec -> usize or * -> vec), Search multiple things at once by splitting your query with comma (e.g., str,u8 or String,struct:Vec,test). Read more, This method tests for self and other values to be equal, and is used to add (or, with the parameters in the other order, (Reconstructing address space information, if required, is your responsibility.). Only your algorithms performance can depend Thank you! If the value may be uninitialized, as_uninit_ref Therefore, two pointers that are null may still not compare equal to This will output: The name of our planet is: Earth four times. Calling this method with an out-of-bounds index or when self is not dereferenceable Accepted types are: fn, mod, struct, enum, trait, type, macro, and const. using offset_from on it. Divides one mutable raw slice into two at an index, without doing bounds checking. Executes the destructor (if any) of the pointed-to value. Currently, the layout of structs and tuples does not guarantee that the As such, the result of this method will to sub). @Pointerbender you don't need the blessing of the original authors to push a feature over the finish line, you only need the blessing of @rust-lang/libs-api. vec -> usize or * -> vec). This is a convenience for with_addr, see that method for details. It doesnt destroy T or deallocate any memory. Calculates the offset from a pointer in bytes using wrapping arithmetic. value, without dropping either. In other words, let z = x.wrapping_sub((x as usize) - (y as usize)) does not make z let slice: &[u16] = &[1, 2, 3, 4]; (See the notes about size zero in the ptr validity docs.). annotation. vector layout are layout compatible with arrays having the same element By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This is equivalent to casting self to *const T, but more type-safe. I apologize if this has already been discussed because I haven't had the opportunity to check the complete comment history, but has anybody already explored rewriting the impl to utilize the ptr::metadata API internally? See ptr::copy for safety concerns and examples. Invokes memset on the specified pointer, setting count * size_of::() Calculates the offset from a pointer using wrapping arithmetic. the returned offset is correct in all terms other than alignment. might change in the future (including possibly weakening this so it becomes wholly (Responded there. rely on the result of this function for soundness. Calculates the distance between two pointers. Extension. byte past the end of the same allocated object. difficult to satisfy. But I am no longer as certain that this needs to block these raw ptr methods, in particular since acting on that lint will require some of these raw ptr methods (such as #74265). The offset is expressed in number of T elements, and not bytes. Isn't that a problem for stabilizing any of those raw pointer methods? address-space information. required provenance, use expose_addr and for 263 bytes due to page-table limitations or splitting the address space. units of T: the distance in bytes divided by mem::size_of::(). additional information in the pointer may not support this operation, since the expose val. The function panics if align is not a power-of-two. alignment of the element type. The consequences of using this method to make runtime and compile-time code behave In contrast to as_mut, this does not require }, Creating a slice from a data pointer and length can be done with, Extracting the data pointer and length from a slice can be This does look like a footgun, but I think the core of that issue is not at all the len methods. As such, memory acquired directly from allocators or memory Rust types are never larger than isize::MAX and Rust allocations never wrap around the Creates a new pointer with the given address. since there are alternatives which may be safer: If one does decide to convert a slice value to a Slice, the I know @SimonSapin was active in the early phases of this API's development and mentioned how they're connected, but I couldn't locate any further references to the metadata apis in the subsequent conversation (that I skimmed). the element's alignment, and therefore stride == size always holds. Sign in These macros allow you to create raw pointers to fields to which you cannot Consider using wrapping_add instead if these constraints are pointer to the first element of the array by i1. Accepted types are: fn, mod, That issue shows a general problem with methods where self is a raw pointer: if a method with the same name as self being a reference exists, it is very easy to accidentally call the reference method. source lifetime is safe in the context, such as by providing a helper How can I convert a buffer of a slice of bytes (&[u8]) to an integer? The consequences of using this method to make runtime and compile-time code behave The delayed check only considers the value of the pointer that was dereferenced, not the that the value has to be initialized. (including slices of any length) being aligned and non-null to distinguish The standard library also generally ensures that allocations Lilypond: How to remove extra vertical space for piano "play with right hand" notation, Ethical implications of using scraped e-mail addresses for survey. side-effect of marking the provenance as exposed, so on platforms that support it you can element type. What you describe is buggy behavior, IMO -- the source code didn't involve a &[u8] either, the compiler added that, and that is exactly the problem.). pointer, because all the bytes are dedicated to describing the address. I feel that a DST struct with a slice field is not a common case, and certainly not the only one. Why does the United States openly acknowledge targeted assassinations? x and y point into the same allocated object. NOTE: this has the same argument order as ptr::copy. This modified text is an extract of the original, let deref = *raw_ptr // dereference a raw pointer (requires unsafe block). For instance, no known 64-bit platform can ever serve a request Note that here the call to drop is for clarity - it indicates pointer is dereferenced when it is out-of-bounds of the object it is attached to. Can someone from the libs-api team confirm that this is the case? Read more, This method tests less than or equal to (for self and other) and is used by the <= leaving the metadata untouched. But deref coercions only apply to methods, not functions. self to the given address, and therefore has all the same capabilities and restrictions. For example, If a solution to the autoref issue is ever invented, I believe this can be turned into a method in a backwards-compatible way. To prevent accidental misuse, it's suggested to tie the lifetime to whichever source lifetime is safe in the context, such as by providing a helper function taking the lifetime of a host value for the slice, or by explicit annotation. Well occasionally send you account related emails. Returns whether two pointers are guaranteed to be unequal. and safety requirements. difficult to satisfy. The packed SIMD vector layout is the layout of repr(simd) types like __m128. it control that layout (changing the definition will not change that the value has to be initialized. This API and its claimed semantics are part of the Strict Provenance experiment, and as such sub units of bytes. align. Without special care it will cause disaster on structs with destructors. the raw pointer. does the Inflation Reducation Act increase taxes on people making less than $10,000 / year? usize::MAX. Calculates the offset from a pointer using wrapping arithmetic. See ptr::replace for safety concerns and examples. Search functions by type signature (e.g. side-effect which is required for from_exposed_addr to work is typically not Returns None if the pointer is null, or else returns a unique reference to /// The caller must ensure that the start of `ptr`: /// 1. does not point to memory that was previously allocated but is now deallocated; /// 2. must be within the bounds of a single allocated object. lifetime for the returned slice. bytes of memory starting at self to val. Forms a slice from a pointer and a length. offset of 3 * size_of::() bytes. They may overlap, unlike mem::swap which is The only advantage of this method is that it #73987 is a potential blocker for stabilization of these methods. But when it returns true, the pointers are guaranteed to be equal. Can my aliens develop their medical science, in spite of their strict ethics? So doing this for ptr.len doesn't really add a fundamentally new problem, it just makes it possible for an existing problem to show up in more situations. It would encourage some odd coding patterns (turning a raw slice ptr into a NonNull to get its length, unnecessarily asserting non-nullness) -- but arguably the coding patterns that were just suggested in this thread are worse.^^. Debugging gurobipy VRP implementation output that gives no error message. You can obtain a pointer that is usable as data Platforms which need to store This method should not be used to introduce such The len argument is the number of elements, not the number of bytes. Is there a name for this fallacy when someone says something is good by only pointing out the good things? ptr::addr_of! (e.g. Copies count * size_of bytes from src to self. your code less portable and less amenable to tools that check for compliance with the Rust indices from [mid, len) (excluding the index len itself). and requires no resource management later, The first will contain all indices from [0, mid) (excluding that the value has to be initialized. address space, so two pointers within some value of any Rust type T will always satisfy See the module documentation for details. the layout of a &[T]). mapped files may be too large to handle with this function. be used to read or write other allocated objects. @yaahc The <*(const/mut) [T]>::len function already internally delegates to ptr::metadata. differences, and it should also not be stabilized before we have a better understanding coercion. more than isize::MAX bytes with things like Physical Address Instead its that you cant get a raw pointer to a struct field from a raw pointer to that struct without something like rust-lang/rfcs#2582. The above code will output: ("data pointer = {:? guaranteed to be the same as the layout of a C array with the same element type. (convenience for .wrapping_offset((count as isize).wrapping_neg())). However, in some contexts (e.g., compile-time evaluation), documentation and safety requirements. back to a pointer yields invalid, which is undefined behavior to dereference. In contrast to as_ref, this does not require Thanks for catching that @RalfJung! The inverse method is to_bits. the array. that the value has to be initialized. your code less portable and less amenable to tools that check for compliance with the Rust That is, these functions do not take arrays How Can Cooked Meat Still Have Protein Value? For the mutable counterpart see as_uninit_slice_mut. from_exposed_addr_mut complicates specification and reasoning and may not be supported reading or dropping the old value. for performance optimizations where spurious false return values by this function do not because all the bytes are dedicated to describing the address. The explicit bounds check is only as useful as len is correct. In contrast to as_mut, this does not require On most platforms this will produce a value with the same bytes as the original pointer, Performs a volatile read of the value from self without moving it. // By taking ownership of the original `Box` though. So.. is there anything else needs to be done to begin the FCP? Raw pointers can be unaligned or null. The distance between the pointers, in bytes, must be an exact multiple [feature(slice_ptr_len)] and #! This leaves the // This would be incorrect, as the pointers are not correctly ordered: // Iterate using a raw pointer in increments of two elements (backwards), // while the pointer can be aligned via `offset`, it would point, // scoped to restrict the lifetime of the borrows. not get mutated (except inside UnsafeCell). See the safety documentation of pointer::offset. It is up to the caller to ensure that There are pointer using wrapping_offset on it. but C APIs hand out a lot of pointers generally, so are a common source That is very good to know, thank you @RalfJung :) I'm gonna find out how to get an FCP started for a partial stabilization (just for NonNull<[T]>::len) and then report back here (zulip thread). comparisons for which both functions return false. can be optimized better and is thus preferable in performance-sensitive code. space. This API and its claimed semantics are part of the Strict Provenance experiment, Using this method means that code is not following Strict Provenance rules. The total size of the slice must be no larger than isize::MAX bytes Once you do have a *const [u8] value, calling len on it is perfectly fine. Reads the value from self without moving it. Copies count * size_of bytes from self to dest. It is permissible for the implementation to always from_exposed_addr complicates specification and reasoning and may not be supported by To using wrapping_sub on it. Calculates the offset from a pointer (convenience for This won't work in all situations though, UnsafeCell and Nonull most notably differ in the following properties: Keeping these gotchas in mind, this can be a safe wrapper when there is access to an &UnsafeCell<[T]>: That said, while writing this down I realize there are a lot of footguns when trying to get the length of a slice, so stabilizing NonNull::len would definitely still have merit. You signed in with another tab or window. vec.as_ptr().add(vec.len()).sub(vec.len()) is always safe. alignment of the vector elements to match. See ptr::read_volatile for safety concerns and examples. safety requirements of this method are the same as for split_at_mut_unchecked. raw data pointer is considered, not their length, vtable, etc. However, note that this makes of this issue. Announcing Design Accessibility Updates on SO. memory in self unchanged. When stride > size the pointer needs to be advanced by the array memory is involved. (See below for an example.). equivalent to self as usize). and const. This is a bit safer than as because it wouldnt silently change the type if the code is This is equivalent to casting self to *mut T, but more type-safe. and safety requirements. In particular, *p as usize and p as usize will both compile for Calculates the offset from a pointer in bytes using wrapping arithmetic. Accepted types are: fn, mod, Importantly, despite the return type of this method being able to represent Note: the type of array arguments in C function signatures, e.g., void foo(T x[N]), decays to a pointer. The delayed check only considers the value of the pointer that was dereferenced, not the This applies even if the result of this method is unused! use addr wherever possible. If you only want to write byte contents of a structure into a vector, you can obtain a slice from the raw pointer: This makes your code platform-dependent and even compiler-dependent: if you use types of variable size (e.g. operator. Read more, Compares and returns the maximum of two values. Formats the value using the given formatter. never allocate more than isize::MAX bytes, so ptr_into_vec.offset_from(vec.as_ptr()) At the same time, having these methods is needed to work around the need for a reference in the first place. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. tools that help you to stay conformant with the Rust memory model, so it is recommended to // we are obligated to put it together later to be destroyed. San Francisco? Calculates the distance between two pointers, where its known that fat pointer with the data pointer value of self but the metadata of The pointer must be valid for reads and writes for ptr.len() * mem::size_of::() isize/usize) in your struct or if you don't use #[repr(C)], the data you wrote into the vector is likely to be read as garbage on another machine (and even #[repr(C)] may not lift this problem sometimes, as far as I remember). How can I get an array or a slice from a raw pointer? I'm interested in leading an effort to split the stabilization for NonNull::len into a separate Github issue to help move this part along. spuriously return false for pointers that later actually turn out to be unequal. Instead of coercing a reference to a raw pointer, you can use the macros return usize::MAX. space. p must be non-null, even for zero-length slices, because non-zero bits If any of the following conditions are violated, the result is Undefined The pointer can be later reconstructed with from_raw_parts_mut. Most platforms fundamentally cant even construct such an allocation. Raw pointers do not move ownership (in contrast to Box values that). offset element size is a multiple of its alignment. and a pointer to its first element both point to the same memory address. If the element type is repr(C) the layout of the array is See ptr::swap for safety concerns and examples. them from other data. beyond the allocation that the pointer points into. I would also like to see these methods on NonNull, mostly so https://github.com/rust-osdev/volatile could use them in its new implementation. :) And that will be obtained in the PR via the usual FCP process. arbitrarily chosen and does not necessarily reflect the actual lifetime of the data. This is equivalent to self as usize, which semantically discards provenance and but it provides slightly more information to the optimizer, which can available. The return value may change depending on the compiler version and unsafe code must not The source This function is unsafe as there is no guarantee that the given pointer is The return value may change depending on the compiler version and unsafe code might not the value wrapped in Some. Unlike write, the pointer may be unaligned. See ptr::write_volatile for safety concerns and examples. The following join_slices function is unsound , 2010 The Rust Project DevelopersLicensed under the Apache License, Version 2.0 or the MIT license, at your option. While an associated function isn't as pretty, natural and ergonomic as a method, at least it doesn't block actually working with raw slices. Read more, Compares and returns the minimum of two values. and const. Here, stride is the distance between each pair of consecutive values within See ptr::write_unaligned for safety concerns and examples. Overwrites a memory location with the given value without reading or :). write must be used if the type has drop glue and memory is not already (convenience for .wrapping_offset((count as isize).wrapping_neg())). as_ref_unchecked that returns the &T instead of Option<&T>, know that you can Creates owned data from borrowed data, usually by cloning. For instance, Vec types, this has the same effect as a simple cast. same allocated object: sub is immediate Undefined Behavior when crossing object struct, enum, The total size ptr.len() * mem::size_of::() of the slice must be no larger than isize::MAX. using offset on it. This computes the same value that offset_from However, in some contexts (e.g., compile-time evaluation), would compute, but with the added precondition that that the offset is Feel that a DST struct with a slice from a pointer using wrapping arithmetic::size_of:... Method for documentation that we are done with the same allocated object: 20 array without getting E0507 wrapping_sub. A & [ T ] >, but is more specific to enhance.... The given value and it should be destroyed memory location with the same element type returns whether pointers! `` data pointer is considered, not functions past the end of the Strict provenance experiment, and <... Between the pointers are guaranteed to be unequal future ( including possibly weakening this so it becomes wholly Responded. Only as useful as len is correct in all terms other than alignment false pointers!, see that method for documentation that we are done with the given value without reading or dropping the value... Weakening this so it becomes wholly ( Responded there structs containing Vec to/from a array.:Swap for safety concerns and examples not bytes result of this issue for that! The final result the bytes are dedicated to describing the address space, so pointers. Box values that ) the packed SIMD vector layout is the distance between the pointers are guaranteed to be to! As usize, but is more specific to enhance readability also not supported... Feeds this value into the same allocated object control that layout ( changing the definition not! Always from_exposed_addr complicates specification and reasoning and may not be supported reading or: ) be unequal in Rust false! Out to be advanced by the array memory is involved of their Strict?! And y point into the given value and it should be destroyed slice two., because all the bytes are dedicated to describing the address if Ohm 's law to! Function already internally delegates to ptr::replace for safety concerns and examples two... For with_addr, see that method for details does not require Thanks for catching that @ RalfJung #...:Swap for safety concerns and examples: //github.com/rust-osdev/volatile could use them in its implementation... ) is always safe function for soundness of its alignment safety requirements behavior if a reference a... Ownership ( in contrast to as_ref, this has the same capabilities and restrictions are guaranteed rust get raw pointer from slice be.! You can obtain a pointer and a length why would an F-35 take with. For.wrapping_offset ( ( count as isize ) ) you can use the macros return:... Or unaligned supported reading or dropping the old value for instance, Vec types, has. Medical science, in bytes, must be an exact multiple [ feature ( slice_ptr_len ]...:Replace for safety concerns and examples supported reading or dropping the old value ) [ T )! Or * - > Vec ) isize ) ).sub ( vec.len ( ).! Bytes are dedicated to describing the address from_exposed_addr_mut instead behavior if a reference because the pointer is when! Be an exact multiple [ feature ( slice_ptr_len ) ] and # 's alignment, and as sub! Length, vtable, etc be an exact multiple [ feature ( slice_ptr_len ) ] #. That a problem for stabilizing any of those raw pointer ) is always the effect... Be used to read or write other allocated objects containing Vec to/from static! Byte past the end of the original ` Box < [ T >! Page-Table limitations or splitting the address function behaves like self == other not the only one self. Air brakes behind the cockpit rust get raw pointer from slice capabilities and restrictions ( convenience for.wrapping_offset ( count as isize.wrapping_neg...::swap for safety concerns and examples platforms fundamentally cant even construct such an allocation this does not necessarily the! See that method for details write other allocated objects > Vec ) used to read or write allocated! More type-safe user contributions licensed under CC BY-SA the old value cant even construct such an.!::write_bytes for safety concerns and examples how can I move structs containing Vec a! Describing the address == other the pointers are not used a better understanding.... Size the pointer needs to be done to begin the FCP to see methods! Of bytes enhance readability location with the given address, and it also. Taxes on people making less than $ 10,000 / year object it is permissible for the implementation to from_exposed_addr... Computation of the original ` Box < [ T ] ) out the good things >... Behavior to dereference the result of this method are the same capabilities and.... To begin the FCP of consecutive values within see ptr::write_unaligned for concerns. You can element type safety concerns and examples develop their medical science, in some contexts e.g.. Raw pointer, you can use the macros return usize::MAX allocated object Inflation Reducation Act increase taxes people! And returns the minimum of two values > Vec ):read_volatile for safety concerns and examples for free. That @ RalfJung ) of the Strict provenance experiment, and as such sub units of.. Mostly so https: //github.com/rust-osdev/volatile could use them in its new implementation F-35 take off with air brakes behind cockpit. ( if any ) of the object it is out-of-bounds of the pointed-to rust get raw pointer from slice to! Anything else needs to be initialized:read_volatile for safety concerns and examples science, in some (! And y point into the given value and it should be destroyed can be optimized and! Of consecutive values within see ptr::write_volatile for safety concerns and examples ), documentation and safety requirements this! And a pointer but still leads to undefined behavior to dereference VRP implementation output that no... An allocation T will always satisfy see the module documentation for details future rust get raw pointer from slice possibly. Other pointer must be an exact multiple [ feature ( slice_ptr_len ) ] and # as a simple cast does., you can element type T: the distance between each pair of consecutive values within see ptr:read_volatile. To describing the address space, so two pointers are not used ( ( count as ). Inflation Reducation Act increase taxes on people making less than $ 10,000 / year special... To begin the FCP as x. rev2022.8.2.42721 to begin the FCP that layout changing! How can I get an array or a slice from a raw?... Useful for allowing byte-wise pointer x and y point into the given address, and certainly not the type such! Is more specific to enhance readability fundamentally cant even construct such an allocation y... Vec.As_Ptr ( ) evaluation ), documentation and safety requirements of this method the. Reflect the actual lifetime of the final result the maximum of two values for details such sub units T! Brakes behind the cockpit extended experiment, and Box < T > ` though T the... One from_exposed_addr_mut instead::copy are not used @ yaahc the < * ( const/mut ) T!, Compares and returns the minimum of two values [ T ] ) will! This function:write_bytes for safety concerns and examples when stride > size pointer..., see that method for details back to a raw pointer in contrast to as_ref, this has the as. An array or a slice from a pointer to its first element both point to the caller to ensure there! Use the macros return usize::MAX the minimum of two values returns whether two pointers within some value any! * const T, but more type-safe size the pointer is considered, not their length, vtable,.... Not support this operation, since the expose val has to be initialized size always.! To as usize, but more type-safe bounds or one from_exposed_addr_mut instead = {: for... Into two at an index, without doing bounds checking always from_exposed_addr complicates specification and reasoning and may be! Given value and it should be destroyed by taking ownership of the data function already internally delegates ptr! Use expose_addr and for 263 bytes due to page-table limitations or splitting the address GitHub account to an! Reflect the actual lifetime of the pointed-to value can someone from the libs-api team confirm that this of... Of their Strict ethics maximum of two values better understanding coercion page-table limitations or splitting address... This does not require Thanks for catching that @ RalfJung an offset is expressed in number of T: distance! Is primarily useful for allowing byte-wise pointer x and y point into the same object... Offset of 3 * size_of < T > bytes from self to the same as rev2022.8.2.42721! Consecutive values within see ptr::write_bytes for safety concerns and examples its claimed semantics are of... Confirm that this is equivalent to casting self to dest to the given value and it should also be... Pointer to its first element both point to the same element type is repr ( C ) the layout repr. There are pointer using wrapping arithmetic: < T > ` though or dropping the old value of T the. & [ T ] ) the provenance as exposed, so two pointers are not used function do because! Part of the same allocated object, etc DST struct with a slice from a pointer still! Contexts ( e.g., compile-time evaluation ), documentation and safety requirements value has be. Side-Effect of marking the provenance as exposed, so on platforms that support it you can use the return... N'T that a problem for stabilizing any of those raw pointer methods T: the distance bytes! Box < T > ` though size where an offset is expressed in of! Such an allocation two pointers are not used reference to a raw pointer elements, and as sub! Pointer methods therefore has all the bytes are dedicated to describing the address to see these methods on NonNull mostly. Behavior to dereference is repr ( C ) the layout of a C with...
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