我正在尝试制作一个简单的分配器，从固定的缓冲区池中分配和释放缓冲区。
struct AllocatedMemory<'a> {
mem: &'a mut [u8],
next: Option<&'a mut AllocatedMemory<'a>>,
}
struct Alloc<'a> {
glob: Option<&'a mut AllocatedMemory<'a>>,
}
impl<'a> Alloc<'a> {
fn alloc_cell(mut self: &mut Alloc<'a>) -> &mut AllocatedMemory<'a> {
let rest: Option<&'a mut AllocatedMemory<'a>>;
match self.glob {
Some(ref mut root_cell) => {
rest = std::mem::replace(&mut root_cell.next, None);
}
None => rest = None,
}
match std::mem::replace(&mut self.glob, rest) {
Some(mut root_cell) => {
return root_cell;
}
None => panic!("OOM"),
}
}
fn free_cell(mut self: &mut Alloc<'a>, mut val: &'a mut AllocatedMemory<'a>) {
match std::mem::replace(&mut self.glob, None) {
Some(mut x) => {
let discard = std::mem::replace(&mut val.next, Some(x));
let rest: Option<&'a mut AllocatedMemory<'a>>;
}
None => {}
}
self.glob = Some(val);
}
}
fn main() {
let mut buffer0: [u8; 1024] = [0; 1024];
let mut buffer1: [u8; 1024] = [0; 1024];
{
let mut cell1: AllocatedMemory = AllocatedMemory {
mem: &mut buffer1[0..1024],
next: None,
};
let mut cell0: AllocatedMemory = AllocatedMemory {
mem: &mut buffer0[0..1024],
next: None,
};
let mut allocator = Alloc { glob: None };
allocator.free_cell(&mut cell1); //populate allocator with a cell
allocator.free_cell(&mut cell0); //populate allocator with another cell (why does this fail?)
let mut x = allocator.alloc_cell();
allocator.free_cell(x);
let mut y = allocator.alloc_cell();
let mut z = allocator.alloc_cell();
allocator.free_cell(y);
allocator.free_cell(z);
}
}
错误是
error: `cell0` does not live long enough
allocator.free_cell(&mut cell0); //populate allocator with another cell (why does this fail?)
当我简单地删除cell0并且仅对cell1我的单元池可用时，会发生以下错误：
error: allocator does not live long enough
let mut x = allocator.alloc_cell();
^~~~~~~~~
note: reference must be valid for the block suffix following statement 0 at 46:69...
next: None};
let mut cell0 : AllocatedMemory = AllocatedMemory{mem: &mut buffer0[0..1024],
next: None};
let mut allocator = Alloc {glob : None};
allocator.free_cell(&mut cell1); //populate allocator with a cell
//allocator.free_cell(&mut cell0); //populate allocator with another cell (why does this fail?)
note: ...but borrowed value is only valid for the block suffix following statement 2 at 49:48
let mut allocator = Alloc {glob : None};
allocator.free_cell(&mut cell1); //populate allocator with a cell
//allocator.free_cell(&mut cell0); //populate allocator with another cell (why does this fail?)
let mut x = allocator.alloc_cell();
allocator.free_cell(x);
...
error: aborting due to previous error
有没有人建议如何修复此代码以使其编译并在免费列表中可能有 2 个以上的项目？
我想填充对数组的引用列表，然后能够弹出它们 - 使用它们一段时间并将使用/完成的值放回空闲列表中。
这里的动机是构建一个使用该#![nostd]指令的库，因此它需要一个分配器接口才能正常运行。