1 // Copyright 2018 The PDFium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "core/fpdfapi/parser/cpdf_object_stream.h"
6
7 #include <utility>
8
9 #include "core/fpdfapi/parser/cpdf_dictionary.h"
10 #include "core/fpdfapi/parser/cpdf_number.h"
11 #include "core/fpdfapi/parser/cpdf_parser.h"
12 #include "core/fpdfapi/parser/cpdf_reference.h"
13 #include "core/fpdfapi/parser/cpdf_stream.h"
14 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
15 #include "core/fpdfapi/parser/cpdf_syntax_parser.h"
16 #include "core/fpdfapi/parser/fpdf_parser_utility.h"
17 #include "core/fxcrt/cfx_read_only_span_stream.h"
18 #include "core/fxcrt/fx_safe_types.h"
19 #include "third_party/base/check.h"
20 #include "third_party/base/memory/ptr_util.h"
21
22 namespace {
23
IsObjectStream(const CPDF_Object * object)24 bool IsObjectStream(const CPDF_Object* object) {
25 const CPDF_Stream* stream = ToStream(object);
26 if (!stream)
27 return false;
28
29 // See ISO 32000-1:2008 spec, table 16.
30 RetainPtr<const CPDF_Dictionary> stream_dict = stream->GetDict();
31 if (!ValidateDictType(stream_dict.Get(), "ObjStm"))
32 return false;
33
34 RetainPtr<const CPDF_Number> number_of_objects =
35 stream_dict->GetNumberFor("N");
36 if (!number_of_objects || !number_of_objects->IsInteger() ||
37 number_of_objects->GetInteger() < 0 ||
38 number_of_objects->GetInteger() >=
39 static_cast<int>(CPDF_Parser::kMaxObjectNumber)) {
40 return false;
41 }
42
43 RetainPtr<const CPDF_Number> first_object_offset =
44 stream_dict->GetNumberFor("First");
45 if (!first_object_offset || !first_object_offset->IsInteger() ||
46 first_object_offset->GetInteger() < 0) {
47 return false;
48 }
49
50 return true;
51 }
52
53 } // namespace
54
55 // static
Create(RetainPtr<const CPDF_Stream> stream)56 std::unique_ptr<CPDF_ObjectStream> CPDF_ObjectStream::Create(
57 RetainPtr<const CPDF_Stream> stream) {
58 if (!IsObjectStream(stream.Get()))
59 return nullptr;
60
61 // Protected constructor.
62 return pdfium::WrapUnique(new CPDF_ObjectStream(std::move(stream)));
63 }
64
CPDF_ObjectStream(RetainPtr<const CPDF_Stream> obj_stream)65 CPDF_ObjectStream::CPDF_ObjectStream(RetainPtr<const CPDF_Stream> obj_stream)
66 : stream_acc_(pdfium::MakeRetain<CPDF_StreamAcc>(obj_stream)),
67 first_object_offset_(obj_stream->GetDict()->GetIntegerFor("First")) {
68 DCHECK(IsObjectStream(obj_stream.Get()));
69 Init(obj_stream.Get());
70 }
71
72 CPDF_ObjectStream::~CPDF_ObjectStream() = default;
73
ParseObject(CPDF_IndirectObjectHolder * pObjList,uint32_t obj_number,uint32_t archive_obj_index) const74 RetainPtr<CPDF_Object> CPDF_ObjectStream::ParseObject(
75 CPDF_IndirectObjectHolder* pObjList,
76 uint32_t obj_number,
77 uint32_t archive_obj_index) const {
78 if (archive_obj_index >= object_info_.size())
79 return nullptr;
80
81 const auto& info = object_info_[archive_obj_index];
82 if (info.obj_num != obj_number)
83 return nullptr;
84
85 RetainPtr<CPDF_Object> result =
86 ParseObjectAtOffset(pObjList, info.obj_offset);
87 if (result)
88 result->SetObjNum(obj_number);
89 return result;
90 }
91
Init(const CPDF_Stream * stream)92 void CPDF_ObjectStream::Init(const CPDF_Stream* stream) {
93 stream_acc_->LoadAllDataFiltered();
94 data_stream_ =
95 pdfium::MakeRetain<CFX_ReadOnlySpanStream>(stream_acc_->GetSpan());
96
97 CPDF_SyntaxParser syntax(data_stream_);
98 const int object_count = stream->GetDict()->GetIntegerFor("N");
99 for (int32_t i = object_count; i > 0; --i) {
100 if (syntax.GetPos() >= data_stream_->GetSize())
101 break;
102
103 const uint32_t obj_num = syntax.GetDirectNum();
104 const uint32_t obj_offset = syntax.GetDirectNum();
105 if (!obj_num)
106 continue;
107
108 object_info_.emplace_back(obj_num, obj_offset);
109 }
110 }
111
ParseObjectAtOffset(CPDF_IndirectObjectHolder * pObjList,uint32_t object_offset) const112 RetainPtr<CPDF_Object> CPDF_ObjectStream::ParseObjectAtOffset(
113 CPDF_IndirectObjectHolder* pObjList,
114 uint32_t object_offset) const {
115 FX_SAFE_FILESIZE offset_in_stream = first_object_offset_;
116 offset_in_stream += object_offset;
117
118 if (!offset_in_stream.IsValid())
119 return nullptr;
120
121 if (offset_in_stream.ValueOrDie() >= data_stream_->GetSize())
122 return nullptr;
123
124 CPDF_SyntaxParser syntax(data_stream_);
125 syntax.SetPos(offset_in_stream.ValueOrDie());
126 return syntax.GetObjectBody(pObjList);
127 }
128