ppapi/shared_impl/array_writer.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 PPAPI_SHARED_IMPL_ARRAY_WRITER_H_
   6 #define PPAPI_SHARED_IMPL_ARRAY_WRITER_H_
   7
   8 #include <string.h>
   9
  10 #include <vector>
  11
  12 #include "base/memory/ref_counted.h"
  13 #include "ppapi/c/pp_array_output.h"
  14 #include "ppapi/c/pp_resource.h"
  15 #include "ppapi/c/pp_var.h"
  16 #include "ppapi/shared_impl/ppapi_shared_export.h"
  17
  18 namespace ppapi {
  19
  20 class Resource;
  21 class Var;
  22
  23 // Holds a PP_ArrayWriter and provides helper functions for writing arrays
  24 // to it. It also handles 0-initialization of the raw C struct and attempts
  25 // to prevent you from writing the array twice.
  26 class PPAPI_SHARED_EXPORT ArrayWriter {
  27  public:
  28   ArrayWriter();  // Creates an is_null() object
  29   ArrayWriter(const PP_ArrayOutput& output);
  30   ~ArrayWriter();
  31
  32   bool is_valid() const { return !!pp_array_output_.GetDataBuffer; }
  33   bool is_null() const { return !is_valid(); }
  34
  35   void set_pp_array_output(const PP_ArrayOutput& output) {
  36     pp_array_output_ = output;
  37   }
  38
  39   // Sets the array output back to its is_null() state.
  40   void Reset();
  41
  42   // StoreArray() and StoreVector() copy the given array/vector of data to the
  43   // plugin output array.
  44   //
  45   // Returns true on success, false if the plugin reported allocation failure.
  46   // In either case, the object will become is_null() immediately after the
  47   // call since one output function should only be issued once.
  48   //
  49   // THIS IS DESIGNED FOR POD ONLY. For the case of resources, for example, we
  50   // want to transfer a reference only on success. Likewise, if you have a
  51   // structure of PP_Vars or a struct that contains a PP_Resource, we need to
  52   // make sure that the right thing happens with the ref on success and failure.
  53   template <typename T>
  54   bool StoreArray(const T* input, uint32_t count) {
  55     // Always call the alloc function, even on 0 array size.
  56     void* dest = pp_array_output_.GetDataBuffer(
  57         pp_array_output_.user_data, count, sizeof(T));
  58
  59     // Regardless of success, we clear the output to prevent future calls on
  60     // this same output object.
  61     Reset();
  62
  63     if (count == 0)
  64       return true;  // Allow plugin to return NULL on 0 elements.
  65     if (!dest)
  66       return false;
  67
  68     if (input)
  69       memcpy(dest, input, sizeof(T) * count);
  70     return true;
  71   }
  72
  73   // Copies the given array/vector of data to the plugin output array.  See
  74   // comment of StoreArray() for detail.
  75   template <typename T>
  76   bool StoreVector(const std::vector<T>& input) {
  77     return StoreArray(input.size() ? &input[0] : NULL, input.size());
  78   }
  79
  80   // Stores the given vector of resources as PP_Resources to the output vector,
  81   // adding one reference to each.
  82   //
  83   // On failure this returns false, nothing will be copied, and the resource
  84   // refcounts will be unchanged. In either case, the object will become
  85   // is_null() immediately after the call since one output function should only
  86   // be issued once.
  87   //
  88   // Note: potentially this could be a template in case you have a vector of
  89   // FileRef objects, for example. However, this saves code since there's only
  90   // one instantiation and is sufficient for now.
  91   bool StoreResourceVector(const std::vector<scoped_refptr<Resource> >& input);
  92
  93   // Like the above version but takes an array of AddRef'ed PP_Resources. On
  94   // storage failure, this will release each resource.
  95   bool StoreResourceVector(const std::vector<PP_Resource>& input);
  96
  97   // Stores the given vector of vars as PP_Vars to the output vector,
  98   // adding one reference to each.
  99   //
 100   // On failure this returns false, nothing will be copied, and the var
 101   // refcounts will be unchanged. In either case, the object will become
 102   // is_null() immediately after the call since one output function should only
 103   // be issued once.
 104   bool StoreVarVector(const std::vector<scoped_refptr<Var> >& input);
 105
 106   // Like the above version but takes an array of AddRef'ed PP_Vars. On
 107   // storage failure, this will release each var.
 108   bool StoreVarVector(const std::vector<PP_Var>& input);
 109
 110  private:
 111   PP_ArrayOutput pp_array_output_;
 112
 113   DISALLOW_COPY_AND_ASSIGN(ArrayWriter);
 114 };
 115
 116 }  // namespace ppapi
 117
 118 #endif  // PPAPI_SHARED_IMPL_ARRAY_WRITER_H_