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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 // This file contains the definition of the IdAllocator class.
      6 
      7 #ifndef GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_
      8 #define GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_
      9 
     10 #include <stdint.h>
     11 
     12 #include <set>
     13 #include <utility>
     14 
     15 #include "base/compiler_specific.h"
     16 #include "base/macros.h"
     17 #include "gpu/gpu_export.h"
     18 
     19 namespace gpu {
     20 
     21 // A resource ID, key to the resource maps.
     22 typedef uint32_t ResourceId;
     23 // Invalid resource ID.
     24 static const ResourceId kInvalidResource = 0u;
     25 
     26 class GPU_EXPORT IdAllocatorInterface {
     27  public:
     28   virtual ~IdAllocatorInterface();
     29 
     30   // Allocates a new resource ID.
     31   virtual ResourceId AllocateID() = 0;
     32 
     33   // Allocates an Id starting at or above desired_id.
     34   // Note: may wrap if it starts near limit.
     35   virtual ResourceId AllocateIDAtOrAbove(ResourceId desired_id) = 0;
     36 
     37   // Marks an id as used. Returns false if id was already used.
     38   virtual bool MarkAsUsed(ResourceId id) = 0;
     39 
     40   // Frees a resource ID.
     41   virtual void FreeID(ResourceId id) = 0;
     42 
     43   // Checks whether or not a resource ID is in use.
     44   virtual bool InUse(ResourceId id) const = 0;
     45 };
     46 
     47 // A class to manage the allocation of resource IDs.
     48 class GPU_EXPORT IdAllocator : public IdAllocatorInterface {
     49  public:
     50   IdAllocator();
     51   virtual ~IdAllocator();
     52 
     53   // Implement IdAllocatorInterface.
     54   virtual ResourceId AllocateID() OVERRIDE;
     55   virtual ResourceId AllocateIDAtOrAbove(ResourceId desired_id) OVERRIDE;
     56   virtual bool MarkAsUsed(ResourceId id) OVERRIDE;
     57   virtual void FreeID(ResourceId id) OVERRIDE;
     58   virtual bool InUse(ResourceId id) const OVERRIDE;
     59 
     60  private:
     61   // TODO(gman): This would work much better with ranges or a hash table.
     62   typedef std::set<ResourceId> ResourceIdSet;
     63 
     64   // The highest ID on the used list.
     65   ResourceId LastUsedId() const;
     66 
     67   // Lowest ID that isn't on the used list. This is slow, use as a last resort.
     68   ResourceId FindFirstUnusedId() const;
     69 
     70   ResourceIdSet used_ids_;
     71   ResourceIdSet free_ids_;
     72 
     73   DISALLOW_COPY_AND_ASSIGN(IdAllocator);
     74 };
     75 
     76 // A class to manage the allocation of resource IDs that are never reused. This
     77 // implementation does not track which IDs are currently used. It is useful for
     78 // shared and programs which cannot be implicitly created by binding a
     79 // previously unused ID.
     80 class NonReusedIdAllocator : public IdAllocatorInterface {
     81  public:
     82   NonReusedIdAllocator();
     83   virtual ~NonReusedIdAllocator();
     84 
     85   // Implement IdAllocatorInterface.
     86   virtual ResourceId AllocateID() OVERRIDE;
     87   virtual ResourceId AllocateIDAtOrAbove(ResourceId desired_id) OVERRIDE;
     88   virtual bool MarkAsUsed(ResourceId id) OVERRIDE;
     89   virtual void FreeID(ResourceId id) OVERRIDE;
     90   virtual bool InUse(ResourceId id) const OVERRIDE;
     91 
     92  private:
     93   ResourceId last_id_;
     94 
     95   DISALLOW_COPY_AND_ASSIGN(NonReusedIdAllocator);
     96 };
     97 
     98 }  // namespace gpu
     99 
    100 #endif  // GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_
    101