TFW allocators aren't stabilized

breakpad-handler/src/alloc.rs

@@ -0,0 +1,371 @@
+#![allow(unused_unsafe)]
+
+mod page_allocator;
+mod page_vec;
+mod raw_vec;
+
+use std::{
+    alloc::{Layout, LayoutError},
+    fmt,
+    ptr::{self, NonNull},
+};
+
+/// Copy of [`AllocError`](std::alloc::AllocError)
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct AllocError;
+
+impl fmt::Display for AllocError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("memory allocation failed")
+    }
+}
+
+/// The error type for `try_reserve` methods.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum TryReserveError {
+    /// Error due to the computed capacity exceeding the collection's maximum
+    /// (usually `isize::MAX` bytes).
+    CapacityOverflow,
+
+    /// The memory allocator returned an error
+    AllocError {
+        /// The layout of allocation request that failed
+        layout: Layout,
+    },
+}
+
+impl From<LayoutError> for TryReserveError {
+    #[inline]
+    fn from(_: LayoutError) -> Self {
+        TryReserveError::CapacityOverflow
+    }
+}
+
+impl fmt::Display for TryReserveError {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        fmt.write_str("memory allocation failed")?;
+        let reason = match &self {
+            TryReserveError::CapacityOverflow => {
+                " because the computed capacity exceeded the collection's maximum"
+            }
+            TryReserveError::AllocError { .. } => " because the memory allocator returned a error",
+        };
+        fmt.write_str(reason)
+    }
+}
+
+/// Copy of [`AllocRef`](std::alloc::AllocRef)
+pub unsafe trait AllocRef {
+    /// Attempts to allocate a block of memory.
+    ///
+    /// On success, returns a [`NonNull<[u8]>`](std::mem::NonNull) meeting the size and alignment guarantees of `layout`.
+    ///
+    /// The returned block may have a larger size than specified by `layout.size()`, and may or may
+    /// not have its contents initialized.
+    ///
+    /// # Errors
+    ///
+    /// Returning `Err` indicates that either memory is exhausted or `layout` does not meet
+    /// allocator's size or alignment constraints.
+    ///
+    /// Implementations are encouraged to return `Err` on memory exhaustion rather than panicking or
+    /// aborting, but this is not a strict requirement. (Specifically: it is *legal* to implement
+    /// this trait atop an underlying native allocation library that aborts on memory exhaustion.)
+    ///
+    /// Clients wishing to abort computation in response to an allocation error are encouraged to
+    /// call the [`handle_alloc_error`](alloc::alloc::handle_alloc_error) function, rather than
+    /// directly invoking `panic!` or similar.
+    fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>;
+
+    /// Behaves like `alloc`, but also ensures that the returned memory is zero-initialized.
+    ///
+    /// # Errors
+    ///
+    /// Returning `Err` indicates that either memory is exhausted or `layout` does not meet
+    /// allocator's size or alignment constraints.
+    ///
+    /// Implementations are encouraged to return `Err` on memory exhaustion rather than panicking or
+    /// aborting, but this is not a strict requirement. (Specifically: it is *legal* to implement
+    /// this trait atop an underlying native allocation library that aborts on memory exhaustion.)
+    ///
+    /// Clients wishing to abort computation in response to an allocation error are encouraged to
+    /// call the [`handle_alloc_error`](alloc::alloc::handle_alloc_error) function, rather than
+    /// directly invoking `panic!` or similar.
+    fn alloc_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+        let ptr = self.alloc(layout)?;
+        // SAFETY: `alloc` returns a valid memory block
+        unsafe {
+            (*ptr.as_ptr())
+                .as_mut_ptr()
+                .write_bytes(0, (*ptr.as_ptr()).len())
+        }
+        Ok(ptr)
+    }
+
+    /// Deallocates the memory referenced by `ptr`.
+    ///
+    /// # Safety
+    ///
+    /// * `ptr` must denote a block of memory [*currently allocated*] via this allocator, and
+    /// * `layout` must [*fit*] that block of memory.
+    ///
+    /// [*currently allocated*]: #currently-allocated-memory
+    /// [*fit*]: #memory-fitting
+    unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout);
+
+    /// Attempts to extend the memory block.
+    ///
+    /// Returns a new [`NonNull<[u8]>`](std::mem::NonNull) containing a pointer and the actual size of the allocated
+    /// memory. The pointer is suitable for holding data described by `new_layout`. To accomplish
+    /// this, the allocator may extend the allocation referenced by `ptr` to fit the new layout.
+    ///
+    /// If this returns `Ok`, then ownership of the memory block referenced by `ptr` has been
+    /// transferred to this allocator. The memory may or may not have been freed, and should be
+    /// considered unusable unless it was transferred back to the caller again via the return value
+    /// of this method.
+    ///
+    /// If this method returns `Err`, then ownership of the memory block has not been transferred to
+    /// this allocator, and the contents of the memory block are unaltered.
+    ///
+    /// # Safety
+    ///
+    /// * `ptr` must denote a block of memory [*currently allocated*] via this allocator.
+    /// * `old_layout` must [*fit*] that block of memory (The `new_layout` argument need not fit it.).
+    /// * `new_layout.size()` must be greater than or equal to `old_layout.size()`.
+    ///
+    /// [*currently allocated*]: #currently-allocated-memory
+    /// [*fit*]: #memory-fitting
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the new layout does not meet the allocator's size and alignment
+    /// constraints of the allocator, or if growing otherwise fails.
+    ///
+    /// Implementations are encouraged to return `Err` on memory exhaustion rather than panicking or
+    /// aborting, but this is not a strict requirement. (Specifically: it is *legal* to implement
+    /// this trait atop an underlying native allocation library that aborts on memory exhaustion.)
+    ///
+    /// Clients wishing to abort computation in response to an allocation error are encouraged to
+    /// call the [`handle_alloc_error`](alloc::alloc::handle_alloc_error) function, rather than
+    /// directly invoking `panic!` or similar.
+    unsafe fn grow(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        debug_assert!(
+            new_layout.size() >= old_layout.size(),
+            "`new_layout.size()` must be greater than or equal to `old_layout.size()`"
+        );
+
+        let new_ptr = self.alloc(new_layout)?;
+
+        // SAFETY: because `new_layout.size()` must be greater than or equal to
+        // `old_layout.size()`, both the old and new memory allocation are valid for reads and
+        // writes for `old_layout.size()` bytes. Also, because the old allocation wasn't yet
+        // deallocated, it cannot overlap `new_ptr`. Thus, the call to `copy_nonoverlapping` is
+        // safe. The safety contract for `dealloc` must be upheld by the caller.
+        unsafe {
+            ptr::copy_nonoverlapping(
+                ptr.as_ptr(),
+                (*new_ptr.as_ptr()).as_mut_ptr(),
+                old_layout.size(),
+            );
+            self.dealloc(ptr, old_layout);
+        }
+
+        Ok(new_ptr)
+    }
+
+    /// Behaves like `grow`, but also ensures that the new contents are set to zero before being
+    /// returned.
+    ///
+    /// The memory block will contain the following contents after a successful call to
+    /// `grow_zeroed`:
+    ///   * Bytes `0..old_layout.size()` are preserved from the original allocation.
+    ///   * Bytes `old_layout.size()..old_size` will either be preserved or zeroed, depending on
+    ///     the allocator implementation. `old_size` refers to the size of the memory block prior
+    ///     to the `grow_zeroed` call, which may be larger than the size that was originally
+    ///     requested when it was allocated.
+    ///   * Bytes `old_size..new_size` are zeroed. `new_size` refers to the size of the memory
+    ///     block returned by the `grow_zeroed` call.
+    ///
+    /// # Safety
+    ///
+    /// * `ptr` must denote a block of memory [*currently allocated*] via this allocator.
+    /// * `old_layout` must [*fit*] that block of memory (The `new_layout` argument need not fit it.).
+    /// * `new_layout.size()` must be greater than or equal to `old_layout.size()`.
+    ///
+    /// [*currently allocated*]: #currently-allocated-memory
+    /// [*fit*]: #memory-fitting
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the new layout does not meet the allocator's size and alignment
+    /// constraints of the allocator, or if growing otherwise fails.
+    ///
+    /// Implementations are encouraged to return `Err` on memory exhaustion rather than panicking or
+    /// aborting, but this is not a strict requirement. (Specifically: it is *legal* to implement
+    /// this trait atop an underlying native allocation library that aborts on memory exhaustion.)
+    ///
+    /// Clients wishing to abort computation in response to an allocation error are encouraged to
+    /// call the [`handle_alloc_error`](alloc::alloc::handle_alloc_error) function, rather than
+    /// directly invoking `panic!` or similar.
+    unsafe fn grow_zeroed(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        debug_assert!(
+            new_layout.size() >= old_layout.size(),
+            "`new_layout.size()` must be greater than or equal to `old_layout.size()`"
+        );
+
+        let new_ptr = self.alloc_zeroed(new_layout)?;
+
+        // SAFETY: because `new_layout.size()` must be greater than or equal to
+        // `old_layout.size()`, both the old and new memory allocation are valid for reads and
+        // writes for `old_layout.size()` bytes. Also, because the old allocation wasn't yet
+        // deallocated, it cannot overlap `new_ptr`. Thus, the call to `copy_nonoverlapping` is
+        // safe. The safety contract for `dealloc` must be upheld by the caller.
+        unsafe {
+            ptr::copy_nonoverlapping(
+                ptr.as_ptr(),
+                (*new_ptr.as_ptr()).as_mut_ptr(),
+                old_layout.size(),
+            );
+            self.dealloc(ptr, old_layout);
+        }
+
+        Ok(new_ptr)
+    }
+
+    /// Attempts to shrink the memory block.
+    ///
+    /// Returns a new [`NonNull<[u8]>`](std::mem::NonNull) containing a pointer and the actual size of the allocated
+    /// memory. The pointer is suitable for holding data described by `new_layout`. To accomplish
+    /// this, the allocator may shrink the allocation referenced by `ptr` to fit the new layout.
+    ///
+    /// If this returns `Ok`, then ownership of the memory block referenced by `ptr` has been
+    /// transferred to this allocator. The memory may or may not have been freed, and should be
+    /// considered unusable unless it was transferred back to the caller again via the return value
+    /// of this method.
+    ///
+    /// If this method returns `Err`, then ownership of the memory block has not been transferred to
+    /// this allocator, and the contents of the memory block are unaltered.
+    ///
+    /// # Safety
+    ///
+    /// * `ptr` must denote a block of memory [*currently allocated*] via this allocator.
+    /// * `old_layout` must [*fit*] that block of memory (The `new_layout` argument need not fit it.).
+    /// * `new_layout.size()` must be smaller than or equal to `old_layout.size()`.
+    ///
+    /// [*currently allocated*]: #currently-allocated-memory
+    /// [*fit*]: #memory-fitting
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the new layout does not meet the allocator's size and alignment
+    /// constraints of the allocator, or if shrinking otherwise fails.
+    ///
+    /// Implementations are encouraged to return `Err` on memory exhaustion rather than panicking or
+    /// aborting, but this is not a strict requirement. (Specifically: it is *legal* to implement
+    /// this trait atop an underlying native allocation library that aborts on memory exhaustion.)
+    ///
+    /// Clients wishing to abort computation in response to an allocation error are encouraged to
+    /// call the [`handle_alloc_error`](alloc::alloc::handle_alloc_error) function, rather than
+    /// directly invoking `panic!` or similar.
+    unsafe fn shrink(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        debug_assert!(
+            new_layout.size() <= old_layout.size(),
+            "`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
+        );
+
+        let new_ptr = self.alloc(new_layout)?;
+
+        // SAFETY: because `new_layout.size()` must be lower than or equal to
+        // `old_layout.size()`, both the old and new memory allocation are valid for reads and
+        // writes for `new_layout.size()` bytes. Also, because the old allocation wasn't yet
+        // deallocated, it cannot overlap `new_ptr`. Thus, the call to `copy_nonoverlapping` is
+        // safe. The safety contract for `dealloc` must be upheld by the caller.
+        unsafe {
+            ptr::copy_nonoverlapping(
+                ptr.as_ptr(),
+                (*new_ptr.as_ptr()).as_mut_ptr(),
+                new_layout.size(),
+            );
+            self.dealloc(ptr, old_layout);
+        }
+
+        Ok(new_ptr)
+    }
+
+    /// Creates a "by reference" adaptor for this instance of `AllocRef`.
+    ///
+    /// The returned adaptor also implements `AllocRef` and will simply borrow this.
+    #[inline(always)]
+    fn by_ref(&self) -> &Self {
+        self
+    }
+}
+
+unsafe impl<A> AllocRef for &A
+where
+    A: AllocRef + ?Sized,
+{
+    #[inline]
+    fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+        (**self).alloc(layout)
+    }
+
+    #[inline]
+    fn alloc_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+        (**self).alloc_zeroed(layout)
+    }
+
+    #[inline]
+    unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout) {
+        // SAFETY: the safety contract must be upheld by the caller
+        unsafe { (**self).dealloc(ptr, layout) }
+    }
+
+    #[inline]
+    unsafe fn grow(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: the safety contract must be upheld by the caller
+        unsafe { (**self).grow(ptr, old_layout, new_layout) }
+    }
+
+    #[inline]
+    unsafe fn grow_zeroed(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: the safety contract must be upheld by the caller
+        unsafe { (**self).grow_zeroed(ptr, old_layout, new_layout) }
+    }
+
+    #[inline]
+    unsafe fn shrink(
+        &self,
+        ptr: NonNull<u8>,
+        old_layout: Layout,
+        new_layout: Layout,
+    ) -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: the safety contract must be upheld by the caller
+        unsafe { (**self).shrink(ptr, old_layout, new_layout) }
+    }
+}