diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs index 674c4fb57c7f0..4a817ebc43b34 100644 --- a/src/libcore/alloc.rs +++ b/src/libcore/alloc.rs @@ -20,6 +20,7 @@ use fmt; use mem; use usize; use ptr::{self, NonNull}; +use num::NonZeroUsize; extern { /// An opaque, unsized type. Used for pointers to allocated memory. @@ -66,7 +67,7 @@ fn size_align() -> (usize, usize) { #[derive(Copy, Clone, Debug, PartialEq, Eq)] pub struct Layout { // size of the requested block of memory, measured in bytes. - size: usize, + size_: usize, // alignment of the requested block of memory, measured in bytes. // we ensure that this is always a power-of-two, because API's @@ -75,17 +76,12 @@ pub struct Layout { // // (However, we do not analogously require `align >= sizeof(void*)`, // even though that is *also* a requirement of `posix_memalign`.) - align: usize, + align_: NonZeroUsize, } - -// FIXME: audit default implementations for overflow errors, -// (potentially switching to overflowing_add and -// overflowing_mul as necessary). - impl Layout { /// Constructs a `Layout` from a given `size` and `align`, - /// or returns `None` if either of the following conditions + /// or returns `LayoutErr` if either of the following conditions /// are not met: /// /// * `align` must be a power of two, @@ -126,23 +122,23 @@ impl Layout { /// /// # Safety /// - /// This function is unsafe as it does not verify that `align` is - /// a power-of-two nor `size` aligned to `align` fits within the - /// address space (i.e. the `Layout::from_size_align` preconditions). + /// This function is unsafe as it does not verify the preconditions from + /// [`Layout::from_size_align`](#method.from_size_align). #[inline] pub unsafe fn from_size_align_unchecked(size: usize, align: usize) -> Self { - Layout { size: size, align: align } + Layout { size_: size, align_: NonZeroUsize::new_unchecked(align) } } /// The minimum size in bytes for a memory block of this layout. #[inline] - pub fn size(&self) -> usize { self.size } + pub fn size(&self) -> usize { self.size_ } /// The minimum byte alignment for a memory block of this layout. #[inline] - pub fn align(&self) -> usize { self.align } + pub fn align(&self) -> usize { self.align_.get() } /// Constructs a `Layout` suitable for holding a value of type `T`. + #[inline] pub fn new() -> Self { let (size, align) = size_align::(); // Note that the align is guaranteed by rustc to be a power of two and @@ -158,6 +154,7 @@ impl Layout { /// Produces layout describing a record that could be used to /// allocate backing structure for `T` (which could be a trait /// or other unsized type like a slice). + #[inline] pub fn for_value(t: &T) -> Self { let (size, align) = (mem::size_of_val(t), mem::align_of_val(t)); // See rationale in `new` for why this us using an unsafe variant below @@ -181,18 +178,19 @@ impl Layout { /// /// # Panics /// - /// Panics if the combination of `self.size` and the given `align` - /// violates the conditions listed in `from_size_align`. + /// Panics if the combination of `self.size()` and the given `align` + /// violates the conditions listed in + /// [`Layout::from_size_align`](#method.from_size_align). #[inline] pub fn align_to(&self, align: usize) -> Self { - Layout::from_size_align(self.size, cmp::max(self.align, align)).unwrap() + Layout::from_size_align(self.size(), cmp::max(self.align(), align)).unwrap() } /// Returns the amount of padding we must insert after `self` /// to ensure that the following address will satisfy `align` /// (measured in bytes). /// - /// E.g. if `self.size` is 9, then `self.padding_needed_for(4)` + /// E.g. if `self.size()` is 9, then `self.padding_needed_for(4)` /// returns 3, because that is the minimum number of bytes of /// padding required to get a 4-aligned address (assuming that the /// corresponding memory block starts at a 4-aligned address). @@ -203,7 +201,7 @@ impl Layout { /// Note that the utility of the returned value requires `align` /// to be less than or equal to the alignment of the starting /// address for the whole allocated block of memory. One way to - /// satisfy this constraint is to ensure `align <= self.align`. + /// satisfy this constraint is to ensure `align <= self.align()`. #[inline] pub fn padding_needed_for(&self, align: usize) -> usize { let len = self.size(); @@ -227,7 +225,8 @@ impl Layout { // size and padding overflow in the above manner should cause // the allocator to yield an error anyway.) - let len_rounded_up = len.wrapping_add(align).wrapping_sub(1) & !align.wrapping_sub(1); + let len_rounded_up = len.wrapping_add(align).wrapping_sub(1) + & !align.wrapping_sub(1); return len_rounded_up.wrapping_sub(len); } @@ -238,14 +237,19 @@ impl Layout { /// layout of the array and `offs` is the distance between the start /// of each element in the array. /// - /// On arithmetic overflow, returns `None`. + /// On arithmetic overflow, returns `LayoutErr`. #[inline] pub fn repeat(&self, n: usize) -> Result<(Self, usize), LayoutErr> { - let padded_size = self.size.checked_add(self.padding_needed_for(self.align)) + let padded_size = self.size().checked_add(self.padding_needed_for(self.align())) .ok_or(LayoutErr { private: () })?; let alloc_size = padded_size.checked_mul(n) .ok_or(LayoutErr { private: () })?; - Ok((Layout::from_size_align(alloc_size, self.align)?, padded_size)) + + unsafe { + // self.align is already known to be valid and alloc_size has been + // padded already. + Ok((Layout::from_size_align_unchecked(alloc_size, self.align()), padded_size)) + } } /// Creates a layout describing the record for `self` followed by @@ -258,16 +262,15 @@ impl Layout { /// start of the `next` embedded within the concatenated record /// (assuming that the record itself starts at offset 0). /// - /// On arithmetic overflow, returns `None`. + /// On arithmetic overflow, returns `LayoutErr`. + #[inline] pub fn extend(&self, next: Self) -> Result<(Self, usize), LayoutErr> { - let new_align = cmp::max(self.align, next.align); - let realigned = Layout::from_size_align(self.size, new_align)?; - - let pad = realigned.padding_needed_for(next.align); + let new_align = cmp::max(self.align(), next.align()); + let pad = self.padding_needed_for(next.align()); - let offset = self.size.checked_add(pad) + let offset = self.size().checked_add(pad) .ok_or(LayoutErr { private: () })?; - let new_size = offset.checked_add(next.size) + let new_size = offset.checked_add(next.size()) .ok_or(LayoutErr { private: () })?; let layout = Layout::from_size_align(new_size, new_align)?; @@ -285,10 +288,11 @@ impl Layout { /// guaranteed that all elements in the array will be properly /// aligned. /// - /// On arithmetic overflow, returns `None`. + /// On arithmetic overflow, returns `LayoutErr`. + #[inline] pub fn repeat_packed(&self, n: usize) -> Result { let size = self.size().checked_mul(n).ok_or(LayoutErr { private: () })?; - Layout::from_size_align(size, self.align) + Layout::from_size_align(size, self.align()) } /// Creates a layout describing the record for `self` followed by @@ -305,17 +309,19 @@ impl Layout { /// signature out of convenience in matching the signature of /// `extend`.) /// - /// On arithmetic overflow, returns `None`. + /// On arithmetic overflow, returns `LayoutErr`. + #[inline] pub fn extend_packed(&self, next: Self) -> Result<(Self, usize), LayoutErr> { let new_size = self.size().checked_add(next.size()) .ok_or(LayoutErr { private: () })?; - let layout = Layout::from_size_align(new_size, self.align)?; + let layout = Layout::from_size_align(new_size, self.align())?; Ok((layout, self.size())) } /// Creates a layout describing the record for a `[T; n]`. /// - /// On arithmetic overflow, returns `None`. + /// On arithmetic overflow, returns `LayoutErr`. + #[inline] pub fn array(n: usize) -> Result { Layout::new::() .repeat(n) @@ -834,7 +840,7 @@ pub unsafe trait Alloc { layout: Layout, new_size: usize) -> Result<(), CannotReallocInPlace> { let _ = ptr; // this default implementation doesn't care about the actual address. - debug_assert!(new_size >= layout.size); + debug_assert!(new_size >= layout.size()); let (_l, u) = self.usable_size(&layout); // _l <= layout.size() [guaranteed by usable_size()] // layout.size() <= new_layout.size() [required by this method] @@ -889,7 +895,7 @@ pub unsafe trait Alloc { layout: Layout, new_size: usize) -> Result<(), CannotReallocInPlace> { let _ = ptr; // this default implementation doesn't care about the actual address. - debug_assert!(new_size <= layout.size); + debug_assert!(new_size <= layout.size()); let (l, _u) = self.usable_size(&layout); // layout.size() <= _u [guaranteed by usable_size()] // new_layout.size() <= layout.size() [required by this method]