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we can handle one layer of pointers!

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This commit is contained in:
Pat Hickey
2020-01-24 18:08:37 -08:00
parent e789033651
commit 020778b7da
9 changed files with 155 additions and 86 deletions
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67
crates/memory/src/borrow.rs
View File

@@ -1,59 +1,66 @@
use std::collections::HashMap;
use crate::region::Region;
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct BorrowHandle(usize);
pub struct GuestBorrows {
immutable: Vec<Region>,
mutable: Vec<Region>,
immutable: HashMap<BorrowHandle, Region>,
mutable: HashMap<BorrowHandle, Region>,
next_handle: BorrowHandle,
}
impl GuestBorrows {
pub fn new() -> Self {
GuestBorrows {
immutable: Vec::new(),
mutable: Vec::new(),
immutable: HashMap::new(),
mutable: HashMap::new(),
next_handle: BorrowHandle(0),
}
}
fn is_borrowed_immut(&self, r: Region) -> bool {
!self.immutable.iter().all(|b| !b.overlaps(r))
!self.immutable.values().all(|b| !b.overlaps(r))
}
fn is_borrowed_mut(&self, r: Region) -> bool {
!self.mutable.iter().all(|b| !b.overlaps(r))
!self.mutable.values().all(|b| !b.overlaps(r))
}
pub fn borrow_immut(&mut self, r: Region) -> bool {
fn new_handle(&mut self) -> BorrowHandle {
let h = self.next_handle;
self.next_handle = BorrowHandle(h.0 + 1);
h
}
pub fn borrow_immut(&mut self, r: Region) -> Option<BorrowHandle> {
if self.is_borrowed_mut(r) {
return false;
return None;
}
self.immutable.push(r);
true
let h = self.new_handle();
self.immutable.insert(h, r);
Some(h)
}
pub fn unborrow_immut(&mut self, r: Region) {
let (ix, _) = self
.immutable
.iter()
.enumerate()
.find(|(_, reg)| r == **reg)
.expect("region exists in borrows");
self.immutable.remove(ix);
pub fn unborrow_immut(&mut self, h: BorrowHandle) {
self.immutable
.remove(&h)
.expect("handle exists in immutable borrows");
}
pub fn borrow_mut(&mut self, r: Region) -> bool {
pub fn borrow_mut(&mut self, r: Region) -> Option<BorrowHandle> {
if self.is_borrowed_immut(r) || self.is_borrowed_mut(r) {
return false;
return None;
}
self.mutable.push(r);
true
let h = self.new_handle();
self.mutable.insert(h, r);
Some(h)
}
pub fn unborrow_mut(&mut self, r: Region) {
let (ix, _) = self
.mutable
.iter()
.enumerate()
.find(|(_, reg)| r == **reg)
.expect("region exists in borrows");
self.mutable.remove(ix);
pub fn unborrow_mut(&mut self, h: BorrowHandle) {
self.mutable
.remove(&h)
.expect("handle exists in mutable borrows");
}
}

18
crates/memory/src/guest_type.rs
View File

@@ -1,4 +1,4 @@
use crate::{GuestPtr, GuestPtrMut, MemoryError};
use crate::{GuestPtrMut, GuestPtrRead, MemoryError};
use thiserror::Error;
pub trait GuestType: Sized {
@@ -13,25 +13,25 @@ pub enum GuestValueError {
}
pub trait GuestTypeCopy: GuestType + Copy {
fn read_val(src: GuestPtr<Self>) -> Result<Self, GuestValueError>;
fn write_val(val: Self, dest: GuestPtrMut<Self>);
fn read_val<P: GuestPtrRead<Self>>(src: &P) -> Result<Self, GuestValueError>;
fn write_val(val: Self, dest: &GuestPtrMut<Self>);
}
pub trait GuestTypeClone: GuestType + Clone {
fn read_ref(src: GuestPtr<Self>, dest: &mut Self) -> Result<(), GuestValueError>;
fn write_ref(val: &Self, dest: GuestPtrMut<Self>);
fn read_ref<P: GuestPtrRead<Self>>(src: &P, dest: &mut Self) -> Result<(), GuestValueError>;
fn write_ref(val: &Self, dest: &GuestPtrMut<Self>);
}
impl<T> GuestTypeClone for T
where
T: GuestTypeCopy,
{
fn read_ref(src: GuestPtr<T>, dest: &mut T) -> Result<(), GuestValueError> {
fn read_ref<P: GuestPtrRead<Self>>(src: &P, dest: &mut T) -> Result<(), GuestValueError> {
let val = GuestTypeCopy::read_val(src)?;
*dest = val;
Ok(())
}
fn write_ref(val: &T, dest: GuestPtrMut<T>) {
fn write_ref(val: &T, dest: &GuestPtrMut<T>) {
GuestTypeCopy::write_val(*val, dest)
}
}
@@ -49,12 +49,12 @@ macro_rules! builtin_copy {
}
impl GuestTypeCopy for $t {
fn read_val(src: GuestPtr<$t>) -> Result<$t, GuestValueError> {
fn read_val<P: GuestPtrRead<$t>>(src: &P) -> Result<$t, GuestValueError> {
Ok(unsafe {
::std::ptr::read_unaligned(src.ptr() as *const $t)
})
}
fn write_val(val: $t, dest: GuestPtrMut<$t>) {
fn write_val(val: $t, dest: &GuestPtrMut<$t>) {
unsafe {
::std::ptr::write_unaligned(dest.ptr_mut() as *mut $t, val)
}

2
crates/memory/src/lib.rs
View File

@@ -4,5 +4,5 @@ mod memory;
mod region;
pub use guest_type::{GuestError, GuestType, GuestTypeClone, GuestTypeCopy, GuestValueError};
pub use memory::{GuestMemory, GuestPtr, GuestPtrMut, MemoryError};
pub use memory::{GuestMemory, GuestPtr, GuestPtrMut, GuestPtrRead, MemoryError};
pub use region::Region;

61
crates/memory/src/memory.rs
View File

@@ -3,7 +3,7 @@ use std::marker::PhantomData;
use std::rc::Rc;
use thiserror::Error;
use crate::borrow::GuestBorrows;
use crate::borrow::{BorrowHandle, GuestBorrows};
use crate::guest_type::GuestType;
use crate::region::Region;
@@ -31,80 +31,85 @@ impl<'a> GuestMemory<'a> {
}
pub fn ptr<T: GuestType>(&'a self, at: u32) -> Result<GuestPtr<'a, T>, MemoryError> {
let r = Region {
let region = Region {
start: at,
len: T::size(),
};
let mut borrows = self.borrows.borrow_mut();
if !self.contains(r) {
Err(MemoryError::OutOfBounds(r))?;
if !self.contains(region) {
Err(MemoryError::OutOfBounds(region))?;
}
if borrows.borrow_immut(r) {
let mut borrows = self.borrows.borrow_mut();
if let Some(handle) = borrows.borrow_immut(region) {
Ok(GuestPtr {
mem: &self,
region: r,
region,
handle,
type_: PhantomData,
})
} else {
Err(MemoryError::Borrowed(r))
Err(MemoryError::Borrowed(region))
}
}
pub fn ptr_mut<T: GuestType>(&'a self, at: u32) -> Result<GuestPtrMut<'a, T>, MemoryError> {
let r = Region {
let region = Region {
start: at,
len: T::size(),
};
let mut borrows = self.borrows.borrow_mut();
if !self.contains(r) {
Err(MemoryError::OutOfBounds(r))?;
if !self.contains(region) {
Err(MemoryError::OutOfBounds(region))?;
}
if borrows.borrow_mut(r) {
let mut borrows = self.borrows.borrow_mut();
if let Some(handle) = borrows.borrow_mut(region) {
Ok(GuestPtrMut {
mem: &self,
region: r,
region,
handle,
type_: PhantomData,
})
} else {
Err(MemoryError::Borrowed(r))
Err(MemoryError::Borrowed(region))
}
}
}
pub trait GuestPtrRead<T> {
fn ptr(&self) -> *const u8;
}
pub struct GuestPtr<'a, T> {
mem: &'a GuestMemory<'a>,
region: Region,
handle: BorrowHandle,
type_: PhantomData<T>,
}
impl<'a, T: GuestType> GuestPtr<'a, T> {
pub fn ptr(&self) -> *const u8 {
impl<'a, T: GuestType> GuestPtrRead<T> for GuestPtr<'a, T> {
fn ptr(&self) -> *const u8 {
(self.mem.ptr as usize + self.region.start as usize) as *const u8
}
pub unsafe fn downcast<Q: GuestType>(self) -> GuestPtr<'a, Q> {
debug_assert!(T::size() == Q::size(), "downcast to type of same size");
GuestPtr {
mem: self.mem,
region: self.region,
type_: PhantomData,
}
}
}
impl<'a, T> Drop for GuestPtr<'a, T> {
fn drop(&mut self) {
let mut borrows = self.mem.borrows.borrow_mut();
borrows.unborrow_immut(self.region);
borrows.unborrow_immut(self.handle);
}
}
pub struct GuestPtrMut<'a, T> {
mem: &'a GuestMemory<'a>,
region: Region,
handle: BorrowHandle,
type_: PhantomData<T>,
}
impl<'a, T: GuestType> GuestPtrRead<T> for GuestPtrMut<'a, T> {
fn ptr(&self) -> *const u8 {
(self.mem.ptr as usize + self.region.start as usize) as *const u8
}
}
impl<'a, T> GuestPtrMut<'a, T> {
pub fn ptr_mut(&self) -> *mut u8 {
(self.mem.ptr as usize + self.region.start as usize) as *mut u8
@@ -113,7 +118,7 @@ impl<'a, T> GuestPtrMut<'a, T> {
impl<'a, T> Drop for GuestPtrMut<'a, T> {
fn drop(&mut self) {
let mut borrows = self.mem.borrows.borrow_mut();
borrows.unborrow_mut(self.region);
borrows.unborrow_mut(self.handle);
}
}