array_writer.h revision 5821806d5e7f356e8fa4b058a389a808ea183019 
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
18namespace ppapi {
19
20class Resource;
21
22// Holds a PP_ArrayWriter and provides helper functions for writing arrays
23// to it. It also handles 0-initialization of the raw C struct and attempts
24// to prevent you from writing the array twice.
25class PPAPI_SHARED_EXPORT ArrayWriter {
26 public:
27  ArrayWriter();  // Creates an is_null() object
28  ArrayWriter(const PP_ArrayOutput& output);
29  ~ArrayWriter();
30
31  bool is_valid() const { return !!pp_array_output_.GetDataBuffer; }
32  bool is_null() const { return !is_valid(); }
33
34  void set_pp_array_output(const PP_ArrayOutput& output) {
35    pp_array_output_ = output;
36  }
37
38  // Sets the array output back to its is_null() state.
39  void Reset();
40
41  // Copies the given vector of data to the plugin output array.
42  //
43  // Returns true on success, false if the plugin reported allocation failure.
44  // In either case, the object will become is_null() immediately after the
45  // call since one output function should only be issued once.
46  //
47  // THIS IS DESIGNED FOR POD ONLY. For the case of resources, for example, we
48  // want to transfer a reference only on success. Likewise, if you have a
49  // structure of PP_Vars or a struct that contains a PP_Resource, we need to
50  // make sure that the right thing happens with the ref on success and failure.
51  template<typename T>
52  bool StoreVector(const std::vector<T>& input) {
53    // Always call the alloc function, even on 0 array size.
54    void* dest = pp_array_output_.GetDataBuffer(
55        pp_array_output_.user_data,
56        static_cast<uint32_t>(input.size()),
57        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 (input.empty())
64      return true;  // Allow plugin to return NULL on 0 elements.
65    if (!dest)
66      return false;
67
68    memcpy(dest, &input[0], sizeof(T) * input.size());
69    return true;
70  }
71
72  // Stores the given vector of resources as PP_Resources to the output vector,
73  // adding one reference to each.
74  //
75  // On failure this returns false, nothing will be copied, and the resource
76  // refcounts will be unchanged. In either case, the object will become
77  // is_null() immediately after the call since one output function should only
78  // be issued once.
79  //
80  // Note: potentially this could be a template in case you have a vector of
81  // FileRef objects, for example. However, this saves code since there's only
82  // one instantiation and is sufficient for now.
83  bool StoreResourceVector(
84      const std::vector< scoped_refptr<Resource> >& input);
85
86  // Like the above version but takes an array of AddRed'ed PP_Resources. On
87  // storage failure, this will release each resource.
88  bool StoreResourceVector(const std::vector<PP_Resource>& input);
89
90 private:
91  PP_ArrayOutput pp_array_output_;
92
93  DISALLOW_COPY_AND_ASSIGN(ArrayWriter);
94};
95
96}  // namespace ppapi
97
98#endif  // PPAPI_SHARED_IMPL_ARRAY_WRITER_H_
99