| // Copyright 2018 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef PAGE_TABLE_SLOT_ALLOCATOR_H_ |
| #define PAGE_TABLE_SLOT_ALLOCATOR_H_ |
| |
| #include "magma_util/macros.h" |
| #include <atomic> |
| #include <mutex> |
| #include <vector> |
| |
| // Thread-safe. |
| class PageTableSlotAllocator { |
| public: |
| PageTableSlotAllocator(uint32_t size) : slot_busy_(size), next_index_(size - 1) {} |
| |
| uint32_t size() { return slot_busy_.size(); } |
| |
| bool Alloc(uint32_t* index_out) |
| { |
| std::lock_guard<std::mutex> lock(mutex_); |
| for (uint32_t i = 0; i < slot_busy_.size(); i++) { |
| uint32_t index = (next_index_ + i) % slot_busy_.size(); |
| if (!slot_busy_[index]) { |
| slot_busy_[index] = true; |
| *index_out = index; |
| next_index_ = index + 1; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| // Called on the connection thread. |
| void Free(uint32_t index) |
| { |
| DASSERT(index < slot_busy_.size()); |
| DASSERT(slot_busy_[index]); |
| slot_busy_[index] = false; |
| } |
| |
| private: |
| std::vector<std::atomic<bool>> slot_busy_; |
| std::mutex mutex_; |
| uint32_t next_index_; |
| |
| friend class TestPageTableSlotAllocator; |
| }; |
| |
| #endif // PAGE_TABLE_SLOT_ALLOCATOR_H_ |