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use crate::alloc::{GlobalAlloc, Layout, System};
use crate::ptr;
use crate::sys::common::alloc::{realloc_fallback, MIN_ALIGN};
#[stable(feature = "alloc_system_type", since = "1.28.0")]
unsafe impl GlobalAlloc for System {
#[inline]
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
// jemalloc provides alignment less than MIN_ALIGN for small allocations.
// So only rely on MIN_ALIGN if size >= align.
// Also see <https://github.com/rust-lang/rust/issues/45955> and
// <https://github.com/rust-lang/rust/issues/62251#issuecomment-507580914>.
if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
libc::malloc(layout.size()) as *mut u8
} else {
aligned_malloc(&layout)
}
}
#[inline]
unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
// See the comment above in `alloc` for why this check looks the way it does.
if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
libc::calloc(layout.size(), 1) as *mut u8
} else {
let ptr = self.alloc(layout);
if !ptr.is_null() {
ptr::write_bytes(ptr, 0, layout.size());
}
ptr
}
}
#[inline]
unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
libc::free(ptr as *mut libc::c_void)
}
#[inline]
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
if layout.align() <= MIN_ALIGN && layout.align() <= new_size {
libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8
} else {
realloc_fallback(self, ptr, layout, new_size)
}
}
}
#[inline]
unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
let mut out = ptr::null_mut();
// posix_memalign requires that the alignment be a multiple of `sizeof(void*)`.
// Since these are all powers of 2, we can just use max.
let align = layout.align().max(crate::mem::size_of::<usize>());
let ret = libc::posix_memalign(&mut out, align, layout.size());
if ret != 0 { ptr::null_mut() } else { out as *mut u8 }
}
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