ppapi/c/pp_array_output.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
   6 /* From pp_array_output.idl modified Thu Mar 28 11:07:53 2013. */
   7
   8 #ifndef PPAPI_C_PP_ARRAY_OUTPUT_H_
   9 #define PPAPI_C_PP_ARRAY_OUTPUT_H_
  10
  11 #include "ppapi/c/pp_macros.h"
  12 #include "ppapi/c/pp_stdint.h"
  13
  14 /**
  15  * @file
  16  * PP_ArrayOutput_GetDataBuffer is a callback function to allocate plugin
  17  * memory for an array. It returns the allocated memory or null on failure.
  18  *
  19  * This function will be called reentrantly. This means that if you call a
  20  * function PPB_Foo.GetData(&array_output), GetData will call your
  21  * GetDataBuffer function before it returns.
  22  *
  23  * This function will be called even when returning 0-length arrays, so be sure
  24  * your implementation can support that. You can return NULL for 0 length
  25  * arrays and it will not be treated as a failure.
  26  *
  27  * You should not perform any processing in this callback, including calling
  28  * other PPAPI functions, outside of allocating memory. You should not throw
  29  * any exceptions. In C++, this means using "new (nothrow)" or being sure to
  30  * catch any exceptions before returning.
  31  *
  32  * The C++ wrapper provides a convenient templatized implementation around
  33  * std::vector which you should generally use instead of coding this
  34  * specifically.
  35  *
  36  * @param user_data The pointer provided in the PP_ArrayOutput structure. This
  37  * has no meaning to the browser, it is intended to be used by the
  38  * implementation to figure out where to put the data.
  39  *
  40  * @param element_count The number of elements in the array. This will be 0
  41  * if there is no data to return.
  42  *
  43  * @param element_size The size of each element in bytes.
  44  *
  45  * @return Returns a pointer to the allocated memory. On failure, returns null.
  46  * You can also return null if the element_count is 0.
  47  */
  48
  49
  50 /**
  51  * @addtogroup Typedefs
  52  * @{
  53  */
  54 typedef void* (*PP_ArrayOutput_GetDataBuffer)(void* user_data,
  55                                               uint32_t element_count,
  56                                               uint32_t element_size);
  57 /**
  58  * @}
  59  */
  60
  61 /**
  62  * @addtogroup Structs
  63  * @{
  64  */
  65 /**
  66  * A structure that defines a way for the browser to return arrays of data
  67  * to the plugin. The browser can not allocate memory on behalf of the plugin
  68  * because the plugin and browser may have different allocators.
  69  *
  70  * Array output works by having the browser call to the plugin to allocate a
  71  * buffer, and then the browser will copy the contents of the array into that
  72  * buffer.
  73  *
  74  * In C, you would typically implement this as follows:
  75  *
  76  * @code
  77  * struct MyArrayOutput {
  78  *   void* data;
  79  *   int element_count;
  80  * };
  81  * void* MyGetDataBuffer(void* user_data, uint32_t count, uint32_t size) {
  82  *   MyArrayOutput* output = (MyArrayOutput*)user_data;
  83  *   output->element_count = count;
  84  *   if (size) {
  85  *     output->data = malloc(count * size);
  86  *     if (!output->data)  // Be careful to set size properly on malloc failure.
  87  *       output->element_count = 0;
  88  *   } else {
  89  *     output->data = NULL;
  90  *   }
  91  *   return output->data;
  92  * }
  93  * void MyFunction() {
  94  *   MyArrayOutput array = { NULL, 0 };
  95  *   PP_ArrayOutput output = { &MyGetDataBuffer, &array };
  96  *   ppb_foo->GetData(&output);
  97  * }
  98  * @endcode
  99  */
 100 struct PP_ArrayOutput {
 101   /**
 102    * A pointer to the allocation function that the browser implements.
 103    */
 104   PP_ArrayOutput_GetDataBuffer GetDataBuffer;
 105   /**
 106    * Data that is passed to the allocation function. Typically, this is used
 107    * to communicate how the data should be stored.
 108    */
 109   void* user_data;
 110 };
 111 /**
 112  * @}
 113  */
 114
 115 #endif  /* PPAPI_C_PP_ARRAY_OUTPUT_H_ */
 116