Chromium roll (https://codereview.chromium.org/976353002)

gpu/command_buffer/common/id_allocator.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains the definition of the IdAllocator class.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_
 #define GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_
 
 #include <stdint.h>
 
-#include <set>
+#include <map>
 #include <utility>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "gpu/gpu_export.h"
 
 namespace gpu {
 
 // A resource ID, key to the resource maps.
 typedef uint32_t ResourceId;
 // Invalid resource ID.
 static const ResourceId kInvalidResource = 0u;
 
 // A class to manage the allocation of resource IDs.
 class GPU_EXPORT IdAllocator {
  public:
   IdAllocator();
   ~IdAllocator();
 
   // Allocates a new resource ID.
   ResourceId AllocateID();
 
   // Allocates an Id starting at or above desired_id.
   // Note: may wrap if it starts near limit.
   ResourceId AllocateIDAtOrAbove(ResourceId desired_id);
 
+  // Allocates |range| amount of contiguous ids.
+  // Returns the first id to |first_id| or |kInvalidResource| if
+  // allocation failed.
+  ResourceId AllocateIDRange(uint32_t range);
+
   // Marks an id as used. Returns false if id was already used.
   bool MarkAsUsed(ResourceId id);
 
   // Frees a resource ID.
   void FreeID(ResourceId id);
 
+  // Frees a |range| amount of contiguous ids, starting from |first_id|.
+  void FreeIDRange(ResourceId first_id, uint32_t range);
+
   // Checks whether or not a resource ID is in use.
   bool InUse(ResourceId id) const;
 
  private:
-  // TODO(gman): This would work much better with ranges or a hash table.
-  typedef std::set<ResourceId> ResourceIdSet;
+  // first_id -> last_id mapping.
+  typedef std::map<ResourceId, ResourceId> ResourceIdRangeMap;
 
-  // The highest ID on the used list.
-  ResourceId LastUsedId() const;
-
-  // Lowest ID that isn't on the used list. This is slow, use as a last resort.
-  ResourceId FindFirstUnusedId() const;
-
-  ResourceIdSet used_ids_;
-  ResourceIdSet free_ids_;
+  ResourceIdRangeMap used_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(IdAllocator);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_