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// Copyright 2018 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
use std::collections::HashMap;
use crate::{Alloc, Error, Result};
/// Manages allocating address ranges.
/// Use `AddressAllocator` whenever an address range needs to be allocated to different users.
/// Allocations must be uniquely tagged with an Alloc enum, which can be used for lookup.
/// An human-readable tag String must also be provided for debugging / reference.
///
/// # Examples
///
/// ```
/// // Anon is used for brevity. Don't manually instantiate Anon allocs!
/// # use resources::{Alloc, AddressAllocator};
/// AddressAllocator::new(0x1000, 0x10000, Some(0x100)).map(|mut pool| {
/// assert_eq!(pool.allocate(0x110, Alloc::Anon(0), "caps".to_string()), Ok(0x1000));
/// assert_eq!(pool.allocate(0x100, Alloc::Anon(1), "cache".to_string()), Ok(0x1200));
/// assert_eq!(pool.allocate(0x100, Alloc::Anon(2), "etc".to_string()), Ok(0x1300));
/// assert_eq!(pool.get(&Alloc::Anon(1)), Some(&(0x1200, 0x100, "cache".to_string())));
/// });
/// ```
#[derive(Debug, Eq, PartialEq)]
pub struct AddressAllocator {
pool_base: u64,
pool_end: u64,
alignment: u64,
next_addr: u64,
allocs: HashMap<Alloc, (u64, u64, String)>,
}
impl AddressAllocator {
/// Creates a new `AddressAllocator` for managing a range of addresses.
/// Can return `None` if `pool_base` + `pool_size` overflows a u64 or if alignment isn't a power
/// of two.
///
/// * `pool_base` - The starting address of the range to manage.
/// * `pool_size` - The size of the address range in bytes.
/// * `align_size` - The minimum size of an address region to align to, defaults to four.
pub fn new(pool_base: u64, pool_size: u64, align_size: Option<u64>) -> Result<Self> {
if pool_size == 0 {
return Err(Error::PoolSizeZero);
}
let pool_end = pool_base
.checked_add(pool_size - 1)
.ok_or(Error::PoolOverflow {
base: pool_base,
size: pool_size,
})?;
let alignment = align_size.unwrap_or(4);
if !alignment.is_power_of_two() || alignment == 0 {
return Err(Error::BadAlignment);
}
Ok(AddressAllocator {
pool_base,
pool_end,
alignment,
next_addr: pool_base,
allocs: HashMap::new(),
})
}
/// Allocates a range of addresses from the managed region with an optional tag.
/// Returns allocated_address. (allocated_address, size, tag) can be retrieved
/// through the `get` method.
pub fn allocate(&mut self, size: u64, alloc: Alloc, tag: String) -> Result<u64> {
if self.allocs.contains_key(&alloc) {
return Err(Error::ExistingAlloc(alloc));
}
if size == 0 {
return Err(Error::AllocSizeZero);
}
let align_adjust = if self.next_addr % self.alignment != 0 {
self.alignment - (self.next_addr % self.alignment)
} else {
0
};
let addr = self
.next_addr
.checked_add(align_adjust)
.ok_or(Error::OutOfSpace)?;
let end_addr = addr.checked_add(size - 1).ok_or(Error::OutOfSpace)?;
if end_addr > self.pool_end {
return Err(Error::OutOfSpace);
}
// TODO(dgreid): Use a smarter allocation strategy. The current strategy is just
// bumping this pointer, meaning it will eventually exhaust available addresses.
self.next_addr = end_addr.saturating_add(1);
self.allocs.insert(alloc, (addr, size, tag));
Ok(addr)
}
/// Returns allocation associated with `alloc`, or None if no such allocation exists.
pub fn get(&self, alloc: &Alloc) -> Option<&(u64, u64, String)> {
self.allocs.get(alloc)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn new_fails_overflow() {
assert!(AddressAllocator::new(u64::max_value(), 0x100, None).is_err());
}
#[test]
fn new_fails_size_zero() {
assert!(AddressAllocator::new(0x1000, 0, None).is_err());
}
#[test]
fn new_fails_alignment_zero() {
assert!(AddressAllocator::new(0x1000, 0x10000, Some(0)).is_err());
}
#[test]
fn new_fails_alignment_non_power_of_two() {
assert!(AddressAllocator::new(0x1000, 0x10000, Some(200)).is_err());
}
#[test]
fn allocate_fails_exising_alloc() {
let mut pool = AddressAllocator::new(0x1000, 0x1000, Some(0x100)).unwrap();
assert_eq!(
pool.allocate(0x800, Alloc::Anon(0), String::from("bar0")),
Ok(0x1000)
);
assert_eq!(
pool.allocate(0x800, Alloc::Anon(0), String::from("bar0")),
Err(Error::ExistingAlloc(Alloc::Anon(0)))
);
}
#[test]
fn allocate_fails_not_enough_space() {
let mut pool = AddressAllocator::new(0x1000, 0x1000, Some(0x100)).unwrap();
assert_eq!(
pool.allocate(0x800, Alloc::Anon(0), String::from("bar0")),
Ok(0x1000)
);
assert_eq!(
pool.allocate(0x900, Alloc::Anon(1), String::from("bar1")),
Err(Error::OutOfSpace)
);
assert_eq!(
pool.allocate(0x800, Alloc::Anon(2), String::from("bar2")),
Ok(0x1800)
);
}
#[test]
fn allocate_alignment() {
let mut pool = AddressAllocator::new(0x1000, 0x10000, Some(0x100)).unwrap();
assert_eq!(
pool.allocate(0x110, Alloc::Anon(0), String::from("bar0")),
Ok(0x1000)
);
assert_eq!(
pool.allocate(0x100, Alloc::Anon(1), String::from("bar1")),
Ok(0x1200)
);
}
#[test]
fn allocate_retrieve_alloc() {
let mut pool = AddressAllocator::new(0x1000, 0x10000, Some(0x100)).unwrap();
assert_eq!(
pool.allocate(0x110, Alloc::Anon(0), String::from("bar0")),
Ok(0x1000)
);
assert_eq!(
pool.get(&Alloc::Anon(0)),
Some(&(0x1000, 0x110, String::from("bar0")))
);
}
}
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