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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 #ifndef GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_
      6 #define GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_
      7 
      8 #include "gpu/command_buffer/common/buffer.h"
      9 #include "gpu/command_buffer/common/constants.h"
     10 #include "gpu/gpu_export.h"
     11 
     12 namespace base {
     13 class SharedMemory;
     14 }
     15 
     16 namespace gpu {
     17 
     18 // Common interface for CommandBuffer implementations.
     19 class GPU_EXPORT CommandBuffer {
     20  public:
     21   struct State {
     22     State()
     23         : num_entries(0),
     24           get_offset(0),
     25           put_offset(0),
     26           token(-1),
     27           error(error::kNoError),
     28           context_lost_reason(error::kUnknown),
     29           generation(0) {
     30     }
     31 
     32     // Size of the command buffer in command buffer entries.
     33     int32 num_entries;
     34 
     35     // The offset (in entries) from which the reader is reading.
     36     int32 get_offset;
     37 
     38     // The offset (in entries) at which the writer is writing.
     39     int32 put_offset;
     40 
     41     // The current token value. This is used by the writer to defer
     42     // changes to shared memory objects until the reader has reached a certain
     43     // point in the command buffer. The reader is responsible for updating the
     44     // token value, for example in response to an asynchronous set token command
     45     // embedded in the command buffer. The default token value is zero.
     46     int32 token;
     47 
     48     // Error status.
     49     error::Error error;
     50 
     51     // Lost context detail information.
     52     error::ContextLostReason context_lost_reason;
     53 
     54     // Generation index of this state. The generation index is incremented every
     55     // time a new state is retrieved from the command processor, so that
     56     // consistency can be kept even if IPC messages are processed out-of-order.
     57     uint32 generation;
     58   };
     59 
     60   struct ConsoleMessage {
     61     // An user supplied id.
     62     int32 id;
     63     // The message.
     64     std::string message;
     65   };
     66 
     67   CommandBuffer() {
     68   }
     69 
     70   virtual ~CommandBuffer() {
     71   }
     72 
     73   // Check if a value is between a start and end value, inclusive, allowing
     74   // for wrapping if start > end.
     75   static bool InRange(int32 start, int32 end, int32 value) {
     76     if (start <= end)
     77       return start <= value && value <= end;
     78     else
     79       return start <= value || value <= end;
     80   }
     81 
     82   // Initialize the command buffer with the given size.
     83   virtual bool Initialize() = 0;
     84 
     85   // Returns the last state without synchronizing with the service.
     86   virtual State GetLastState() = 0;
     87 
     88   // Returns the last token without synchronizing with the service. Note that
     89   // while you could just call GetLastState().token, GetLastState needs to be
     90   // fast as it is called for every command where GetLastToken is only called
     91   // by code that needs to know the last token so it can be slower but more up
     92   // to date than GetLastState.
     93   virtual int32 GetLastToken() = 0;
     94 
     95   // The writer calls this to update its put offset. This ensures the reader
     96   // sees the latest added commands, and will eventually process them. On the
     97   // service side, commands are processed up to the given put_offset before
     98   // subsequent Flushes on the same GpuChannel.
     99   virtual void Flush(int32 put_offset) = 0;
    100 
    101   // The writer calls this to wait until the current token is within a
    102   // specific range, inclusive. Can return early if an error is generated.
    103   virtual void WaitForTokenInRange(int32 start, int32 end) = 0;
    104 
    105   // The writer calls this to wait until the current get offset is within a
    106   // specific range, inclusive. Can return early if an error is generated.
    107   virtual void WaitForGetOffsetInRange(int32 start, int32 end) = 0;
    108 
    109   // Sets the buffer commands are read from.
    110   // Also resets the get and put offsets to 0.
    111   virtual void SetGetBuffer(int32 transfer_buffer_id) = 0;
    112 
    113   // Create a transfer buffer of the given size. Returns its ID or -1 on
    114   // error.
    115   virtual scoped_refptr<gpu::Buffer> CreateTransferBuffer(size_t size,
    116                                                           int32* id) = 0;
    117 
    118   // Destroy a transfer buffer. The ID must be positive.
    119   virtual void DestroyTransferBuffer(int32 id) = 0;
    120 
    121 // The NaCl Win64 build only really needs the struct definitions above; having
    122 // GetLastError declared would mean we'd have to also define it, and pull more
    123 // of gpu in to the NaCl Win64 build.
    124 #if !defined(NACL_WIN64)
    125   // TODO(apatrick): this is a temporary optimization while skia is calling
    126   // RendererGLContext::MakeCurrent prior to every GL call. It saves returning 6
    127   // ints redundantly when only the error is needed for the CommandBufferProxy
    128   // implementation.
    129   virtual error::Error GetLastError();
    130 #endif
    131 
    132  private:
    133   DISALLOW_COPY_AND_ASSIGN(CommandBuffer);
    134 };
    135 
    136 }  // namespace gpu
    137 
    138 #endif  // GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_
    139