zircon/kernel/hypervisor/include/hypervisor/id_allocator.h

// Copyright 2017 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#ifndef ZIRCON_KERNEL_HYPERVISOR_INCLUDE_HYPERVISOR_ID_ALLOCATOR_H_
#define ZIRCON_KERNEL_HYPERVISOR_INCLUDE_HYPERVISOR_ID_ALLOCATOR_H_

#include <bitmap/raw-bitmap.h>
#include <bitmap/storage.h>

namespace hypervisor {

// Allocates architecture-specific resource IDs.
//
// |T| is the type of the ID, and is an integral type.
// |N| is the maximum value of an ID.
template <typename T, T N>
class IdAllocator {
 public:
  zx_status_t Init() { return id_bitmap_.Reset(N); }

  zx_status_t AllocId(T* id) {
    size_t first_unset;
    bool all_set = id_bitmap_.Get(0, N, &first_unset);
    if (all_set)
      return ZX_ERR_NO_RESOURCES;
    if (first_unset >= N)
      return ZX_ERR_OUT_OF_RANGE;
    *id = static_cast<T>(first_unset + 1);
    return id_bitmap_.SetOne(first_unset);
  }

  zx_status_t FreeId(T id) {
    if (id == 0 || !id_bitmap_.GetOne(id - 1))
      return ZX_ERR_INVALID_ARGS;
    return id_bitmap_.ClearOne(id - 1);
  }

 private:
  bitmap::RawBitmapGeneric<bitmap::FixedStorage<N>> id_bitmap_;
};

}  // namespace hypervisor

#endif  // ZIRCON_KERNEL_HYPERVISOR_INCLUDE_HYPERVISOR_ID_ALLOCATOR_H_