106 lines
2.5 KiB
Rust
106 lines
2.5 KiB
Rust
use core::marker::PhantomData;
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use std::alloc;
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use std::ptr;
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pub trait RawBlockTraits {
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fn init_size() -> usize;
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fn align() -> usize;
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}
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#[derive(Debug)]
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pub struct RawBlock<T: RawBlockTraits> {
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pub base: *const u8,
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pub top: *const u8,
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pub ptr: *mut u8,
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_marker: PhantomData<T>,
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}
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impl<T: RawBlockTraits> RawBlock<T> {
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#[inline]
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fn empty_block() -> Self {
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RawBlock {
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base: ptr::null(),
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top: ptr::null(),
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ptr: ptr::null_mut(),
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_marker: PhantomData,
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}
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}
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pub fn new() -> Self {
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let mut block = Self::empty_block();
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unsafe {
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block.grow();
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}
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block
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}
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unsafe fn init_at_size(&mut self, cap: usize) {
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let layout = alloc::Layout::from_size_align_unchecked(cap, T::align());
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self.base = alloc::alloc(layout) as *const _;
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self.top = (self.base as usize + cap) as *const _;
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self.ptr = self.base as *mut _;
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}
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pub unsafe fn grow(&mut self) {
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if self.base.is_null() {
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self.init_at_size(T::init_size());
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} else {
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let size = self.size();
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let layout = alloc::Layout::from_size_align_unchecked(size, T::align());
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self.base = alloc::realloc(self.base as *mut _, layout, size * 2) as *const _;
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self.top = (self.base as usize + size * 2) as *const _;
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self.ptr = (self.base as usize + size) as *mut _;
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}
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}
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/*
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#[inline]
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pub fn take(&mut self) -> Self {
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mem::replace(self, Self::empty_block())
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}
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*/
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#[inline]
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pub fn size(&self) -> usize {
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self.top as usize - self.base as usize
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}
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#[inline(always)]
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fn free_space(&self) -> usize {
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debug_assert!(
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self.ptr as *const _ >= self.base,
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"self.ptr = {:?} < {:?} = self.base",
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self.ptr,
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self.base
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);
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self.top as usize - self.ptr as usize
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}
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pub unsafe fn alloc(&mut self, size: usize) -> *mut u8 {
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if self.free_space() >= size {
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let ptr = self.ptr;
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self.ptr = (self.ptr as usize + size) as *mut _;
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ptr
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} else {
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ptr::null_mut()
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}
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}
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pub fn deallocate(&mut self) {
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unsafe {
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let layout = alloc::Layout::from_size_align_unchecked(self.size(), T::align());
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alloc::dealloc(self.base as *mut _, layout);
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self.top = ptr::null();
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self.base = ptr::null();
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self.ptr = ptr::null_mut();
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}
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}
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}
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