3 files changed, 127 insertions, 0 deletions
diff --git a/resources/Cargo.toml b/resources/Cargo.toml
new file mode 100644
index 0000000..74f0c35
--- /dev/null
+++ b/resources/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "resources"
+version = "0.1.0"
+authors = ["The Chromium OS Authors"]
+
+[dependencies]
+data_model = { path = "../data_model" }
diff --git a/resources/src/address_allocator.rs b/resources/src/address_allocator.rs
new file mode 100644
index 0000000..6c8513d
--- /dev/null
+++ b/resources/src/address_allocator.rs
@@ -0,0 +1,111 @@
+// 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.
+
+/// Manages allocating address ranges.
+/// Use `AddressAllocator` whenever an address range needs to be allocated to different users.
+///
+/// # Examples
+///
+/// ```
+/// # use resources::AddressAllocator;
+///   AddressAllocator::new(0x1000, 0x10000, Some(0x100)).map(|mut pool| {
+///       assert_eq!(pool.allocate(0x110), Some(0x1000));
+///       assert_eq!(pool.allocate(0x100), Some(0x1200));
+///   });
+/// ```
+#[derive(Debug, Eq, PartialEq)]
+pub struct AddressAllocator {
+    pool_base: u64,
+    pool_end: u64,
+    alignment: u64,
+    next_addr: u64,
+}
+
+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>) -> Option<Self> {
+        if pool_size == 0 {
+            return None;
+        }
+        let pool_end = pool_base.checked_add(pool_size - 1)?;
+        let alignment = align_size.unwrap_or(4);
+        if !alignment.is_power_of_two() || alignment == 0 {
+            return None;
+        }
+        Some(AddressAllocator {
+            pool_base,
+            pool_end,
+            alignment,
+            next_addr: pool_base,
+        })
+    }
+
+    /// Allocates a range of addresses from the managed region. Returns `Some(allocated_address)`
+    /// when successful, or `None` if an area of `size` can't be allocated.
+    pub fn allocate(&mut self, size: u64) -> Option<u64> {
+        if size == 0 {
+            return None;
+        }
+        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)?;
+        let end_addr = addr.checked_add(size - 1)?;
+        if end_addr > self.pool_end {
+            return None;
+        }
+        // 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);
+        Some(addr)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn new_fails_overflow() {
+        assert_eq!(AddressAllocator::new(u64::max_value(), 0x100, None), None);
+    }
+
+    #[test]
+    fn new_fails_size_zero() {
+        assert_eq!(AddressAllocator::new(0x1000, 0, None), None);
+    }
+
+    #[test]
+    fn new_fails_alignment_zero() {
+        assert_eq!(AddressAllocator::new(0x1000, 0x10000, Some(0)), None);
+    }
+
+    #[test]
+    fn new_fails_alignment_non_power_of_two() {
+        assert_eq!(AddressAllocator::new(0x1000, 0x10000, Some(200)), None);
+    }
+
+    #[test]
+    fn allocate_fails_not_enough_space() {
+        let mut pool = AddressAllocator::new(0x1000, 0x1000, Some(0x100)).unwrap();
+        assert_eq!(pool.allocate(0x800), Some(0x1000));
+        assert_eq!(pool.allocate(0x900), None);
+        assert_eq!(pool.allocate(0x800), Some(0x1800));
+    }
+
+    #[test]
+    fn allocate_alignment() {
+        let mut pool = AddressAllocator::new(0x1000, 0x10000, Some(0x100)).unwrap();
+        assert_eq!(pool.allocate(0x110), Some(0x1000));
+        assert_eq!(pool.allocate(0x100), Some(0x1200));
+    }
+}
diff --git a/resources/src/lib.rs b/resources/src/lib.rs
new file mode 100644
index 0000000..de87db6
--- /dev/null
+++ b/resources/src/lib.rs
@@ -0,0 +1,9 @@
+// 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.
+
+//! Manages system resources that can be allocated to VMs and their devices.
+
+mod address_allocator;
+
+pub use address_allocator::AddressAllocator;