ui/surface/transport_dib.h

   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 UI_SURFACE_TRANSPORT_DIB_H_
   6 #define UI_SURFACE_TRANSPORT_DIB_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/memory/shared_memory.h"
  10 #include "ui/surface/surface_export.h"
  11
  12 #if defined(OS_WIN)
  13 #include <windows.h>
  14 #endif
  15
  16 class SkCanvas;
  17
  18 // -----------------------------------------------------------------------------
  19 // A TransportDIB is a block of memory that is used to transport pixels
  20 // between processes: from the renderer process to the browser, and
  21 // between renderer and plugin processes.
  22 // -----------------------------------------------------------------------------
  23 class SURFACE_EXPORT TransportDIB {
  24  public:
  25   ~TransportDIB();
  26
  27 // A Handle is the type which can be sent over the wire so that the remote
  28 // side can map the transport DIB.
  29 #if defined(OS_WIN)
  30   typedef HANDLE Handle;
  31 #else  // OS_POSIX
  32   typedef base::SharedMemoryHandle Handle;
  33 #endif
  34
  35   // Returns a default, invalid handle, that is meant to indicate a missing
  36   // Transport DIB.
  37   static Handle DefaultHandleValue() {
  38     return base::SharedMemory::NULLHandle();
  39   }
  40
  41   // Create a new TransportDIB, returning NULL on failure.
  42   //
  43   // The size is the minimum size in bytes of the memory backing the transport
  44   // DIB (we may actually allocate more than that to give us better reuse when
  45   // cached).
  46   //
  47   // The sequence number is used to uniquely identify the transport DIB. It
  48   // should be unique for all transport DIBs ever created in the same
  49   // renderer.
  50   static TransportDIB* Create(size_t size, uint32 sequence_num);
  51
  52   // Map the referenced transport DIB.  The caller owns the returned object.
  53   // Returns NULL on failure.
  54   static TransportDIB* Map(Handle transport_dib);
  55
  56   // Create a new |TransportDIB| with a handle to the shared memory. This
  57   // always returns a valid pointer. The DIB is not mapped.
  58   static TransportDIB* CreateWithHandle(Handle handle);
  59
  60   // Returns true if the handle is valid.
  61   static bool is_valid_handle(Handle dib);
  62
  63   // Returns a canvas using the memory of this TransportDIB. The returned
  64   // pointer will be owned by the caller. The bitmap will be of the given size,
  65   // which should fit inside this memory.
  66   //
  67   // On POSIX, this |TransportDIB| will be mapped if not already. On Windows,
  68   // this |TransportDIB| will NOT be mapped and should not be mapped prior,
  69   // because PlatformCanvas will map the file internally.
  70   //
  71   // Will return NULL on allocation failure. This could be because the image
  72   // is too large to map into the current process' address space.
  73   SkCanvas* GetPlatformCanvas(int w, int h);
  74
  75   // Map the DIB into the current process if it is not already. This is used to
  76   // map a DIB that has already been created. Returns true if the DIB is mapped.
  77   bool Map();
  78
  79   // Return a pointer to the shared memory.
  80   void* memory() const;
  81
  82   // Return the maximum size of the shared memory. This is not the amount of
  83   // data which is valid, you have to know that via other means, this is simply
  84   // the maximum amount that /could/ be valid.
  85   size_t size() const { return size_; }
  86
  87   // Returns a pointer to the SharedMemory object that backs the transport dib.
  88   base::SharedMemory* shared_memory();
  89
  90  private:
  91   TransportDIB();
  92
  93   // Verifies that the dib can hold a canvas of the requested dimensions.
  94   bool VerifyCanvasSize(int w, int h);
  95
  96   explicit TransportDIB(base::SharedMemoryHandle dib);
  97   base::SharedMemory shared_memory_;
  98   uint32 sequence_num_;
  99   size_t size_;  // length, in bytes
 100
 101   DISALLOW_COPY_AND_ASSIGN(TransportDIB);
 102 };
 103
 104 #endif  // UI_SURFACE_TRANSPORT_DIB_H_