mojo/public/cpp/system/buffer.h

   1 // Copyright 2014 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 MOJO_PUBLIC_CPP_SYSTEM_BUFFER_H_
   6 #define MOJO_PUBLIC_CPP_SYSTEM_BUFFER_H_
   7
   8 #include <assert.h>
   9
  10 #include "mojo/public/c/system/buffer.h"
  11 #include "mojo/public/cpp/system/handle.h"
  12 #include "mojo/public/cpp/system/macros.h"
  13
  14 namespace mojo {
  15
  16 // SharedBufferHandle ----------------------------------------------------------
  17
  18 class SharedBufferHandle : public Handle {
  19  public:
  20   SharedBufferHandle() {}
  21   explicit SharedBufferHandle(MojoHandle value) : Handle(value) {}
  22
  23   // Copying and assignment allowed.
  24 };
  25
  26 MOJO_COMPILE_ASSERT(sizeof(SharedBufferHandle) == sizeof(Handle),
  27                     bad_size_for_cpp_SharedBufferHandle);
  28
  29 typedef ScopedHandleBase<SharedBufferHandle> ScopedSharedBufferHandle;
  30 MOJO_COMPILE_ASSERT(sizeof(ScopedSharedBufferHandle) ==
  31                         sizeof(SharedBufferHandle),
  32                     bad_size_for_cpp_ScopedSharedBufferHandle);
  33
  34 inline MojoResult CreateSharedBuffer(
  35     const MojoCreateSharedBufferOptions* options,
  36     uint64_t num_bytes,
  37     ScopedSharedBufferHandle* shared_buffer) {
  38   assert(shared_buffer);
  39   SharedBufferHandle handle;
  40   MojoResult rv = MojoCreateSharedBuffer(options, num_bytes,
  41                                          handle.mutable_value());
  42   // Reset even on failure (reduces the chances that a "stale"/incorrect handle
  43   // will be used).
  44   shared_buffer->reset(handle);
  45   return rv;
  46 }
  47
  48 // TODO(vtl): This (and also the functions below) are templatized to allow for
  49 // future/other buffer types. A bit "safer" would be to overload this function
  50 // manually. (The template enforces that the in and out handles to be of the
  51 // same type.)
  52 template <class BufferHandleType>
  53 inline MojoResult DuplicateBuffer(
  54     BufferHandleType buffer,
  55     const MojoDuplicateBufferHandleOptions* options,
  56     ScopedHandleBase<BufferHandleType>* new_buffer) {
  57   assert(new_buffer);
  58   BufferHandleType handle;
  59   MojoResult rv = MojoDuplicateBufferHandle(
  60       buffer.value(), options, handle.mutable_value());
  61   // Reset even on failure (reduces the chances that a "stale"/incorrect handle
  62   // will be used).
  63   new_buffer->reset(handle);
  64   return rv;
  65 }
  66
  67 template <class BufferHandleType>
  68 inline MojoResult MapBuffer(BufferHandleType buffer,
  69                             uint64_t offset,
  70                             uint64_t num_bytes,
  71                             void** pointer,
  72                             MojoMapBufferFlags flags) {
  73   assert(buffer.is_valid());
  74   return MojoMapBuffer(buffer.value(), offset, num_bytes, pointer, flags);
  75 }
  76
  77 inline MojoResult UnmapBuffer(void* pointer) {
  78   assert(pointer);
  79   return MojoUnmapBuffer(pointer);
  80 }
  81
  82 // A wrapper class that automatically creates a shared buffer and owns the
  83 // handle.
  84 class SharedBuffer {
  85  public:
  86   explicit SharedBuffer(uint64_t num_bytes);
  87   SharedBuffer(uint64_t num_bytes,
  88                const MojoCreateSharedBufferOptions& options);
  89   ~SharedBuffer();
  90
  91   ScopedSharedBufferHandle handle;
  92 };
  93
  94 inline SharedBuffer::SharedBuffer(uint64_t num_bytes) {
  95   MojoResult result MOJO_ALLOW_UNUSED =
  96       CreateSharedBuffer(NULL, num_bytes, &handle);
  97   assert(result == MOJO_RESULT_OK);
  98 }
  99
 100 inline SharedBuffer::SharedBuffer(
 101     uint64_t num_bytes,
 102     const MojoCreateSharedBufferOptions& options) {
 103   MojoResult result MOJO_ALLOW_UNUSED =
 104       CreateSharedBuffer(&options, num_bytes, &handle);
 105   assert(result == MOJO_RESULT_OK);
 106 }
 107
 108 inline SharedBuffer::~SharedBuffer() {
 109 }
 110
 111 }  // namespace mojo
 112
 113 #endif  // MOJO_PUBLIC_CPP_SYSTEM_BUFFER_H_