Implement CPDF_ObjStream.

It is allow do not store raw objects streams within CPDF_Document
for reduce memory usage.

Change-Id: I4377bd5119d87314e76f14255171618cf6ee533d
Reviewed-on: https://pdfium-review.googlesource.com/35430
Reviewed-by: dsinclair <dsinclair@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Art Snake <art-snake@yandex-team.ru>

5 files changed, 219 insertions, 56 deletions

diff --git a/core/fpdfapi/parser/cpdf_object_stream.cpp b/core/fpdfapi/parser/cpdf_object_stream.cpp
new file mode 100644
index 0000000000..779fbffd83
--- /dev/null
+++ b/core/fpdfapi/parser/cpdf_object_stream.cpp
@@ -0,0 +1,136 @@
+// Copyright 2018 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/fpdfapi/parser/cpdf_object_stream.h"
+
+#include <utility>
+
+#include "core/fpdfapi/parser/cpdf_dictionary.h"
+#include "core/fpdfapi/parser/cpdf_number.h"
+#include "core/fpdfapi/parser/cpdf_parser.h"
+#include "core/fpdfapi/parser/cpdf_reference.h"
+#include "core/fpdfapi/parser/cpdf_stream.h"
+#include "core/fpdfapi/parser/cpdf_stream_acc.h"
+#include "core/fxcrt/cfx_memorystream.h"
+#include "third_party/base/stl_util.h"
+
+// static
+bool CPDF_ObjectStream::IsObjectsStreamObject(const CPDF_Object* object) {
+  const CPDF_Stream* stream = ToStream(object);
+  if (!stream)
+    return false;
+
+  const CPDF_Dictionary* stream_dict = stream->GetDict();
+  if (!stream_dict)
+    return false;
+
+  if (stream_dict->GetStringFor("Type") != "ObjStm")
+    return false;
+
+  const CPDF_Number* number_of_objects =
+      ToNumber(stream_dict->GetObjectFor("N"));
+  if (!number_of_objects || !number_of_objects->IsInteger() ||
+      number_of_objects->GetInteger() < 0 ||
+      number_of_objects->GetInteger() >=
+          static_cast<int>(CPDF_Parser::kMaxObjectNumber)) {
+    return false;
+  }
+
+  const CPDF_Number* first_object_offset =
+      ToNumber(stream_dict->GetObjectFor("First"));
+  if (!first_object_offset || !first_object_offset->IsInteger() ||
+      first_object_offset->GetInteger() < 0) {
+    return false;
+  }
+
+  return true;
+}
+
+//  static
+std::unique_ptr<CPDF_ObjectStream> CPDF_ObjectStream::Create(
+    const CPDF_Stream* stream) {
+  if (!IsObjectsStreamObject(stream))
+    return nullptr;
+  // The ctor of CPDF_ObjectStream is protected. Use WrapUnique instead
+  // MakeUnique.
+  return pdfium::WrapUnique(new CPDF_ObjectStream(stream));
+}
+
+CPDF_ObjectStream::CPDF_ObjectStream(const CPDF_Stream* obj_stream)
+    : obj_num_(obj_stream->GetObjNum()),
+      first_object_offset_(obj_stream->GetDict()->GetIntegerFor("First")) {
+  DCHECK(IsObjectsStreamObject(obj_stream));
+  if (const auto* extends_ref =
+          ToReference(obj_stream->GetDict()->GetObjectFor("Extends"))) {
+    extends_obj_num_ = extends_ref->GetRefObjNum();
+  }
+  Init(obj_stream);
+}
+
+CPDF_ObjectStream::~CPDF_ObjectStream() = default;
+
+bool CPDF_ObjectStream::HasObject(uint32_t obj_number) const {
+  return pdfium::ContainsKey(objects_offsets_, obj_number);
+}
+
+std::unique_ptr<CPDF_Object> CPDF_ObjectStream::ParseObject(
+    CPDF_IndirectObjectHolder* pObjList,
+    uint32_t obj_number) const {
+  const auto it = objects_offsets_.find(obj_number);
+  if (it == objects_offsets_.end())
+    return nullptr;
+
+  std::unique_ptr<CPDF_Object> result =
+      ParseObjectAtOffset(pObjList, it->second);
+  if (!result)
+    return nullptr;
+
+  result->SetObjNum(obj_number);
+  return result;
+}
+
+void CPDF_ObjectStream::Init(const CPDF_Stream* stream) {
+  {
+    auto stream_acc = pdfium::MakeRetain<CPDF_StreamAcc>(stream);
+    stream_acc->LoadAllDataFiltered();
+    const uint32_t data_size = stream_acc->GetSize();
+    data_stream_ = pdfium::MakeRetain<CFX_MemoryStream>(
+        stream_acc->DetachData().release(), static_cast<size_t>(data_size),
+        true);
+  }
+
+  CPDF_SyntaxParser syntax;
+  syntax.InitParser(data_stream_, 0);
+
+  const int object_count = stream->GetDict()->GetIntegerFor("N");
+  for (int32_t i = object_count; i > 0; --i) {
+    if (syntax.GetPos() >= data_stream_->GetSize())
+      break;
+
+    const uint32_t obj_num = syntax.GetDirectNum();
+    const uint32_t obj_offset = syntax.GetDirectNum();
+    if (!obj_num)
+      continue;
+
+    objects_offsets_[obj_num] = obj_offset;
+  }
+}
+
+std::unique_ptr<CPDF_Object> CPDF_ObjectStream::ParseObjectAtOffset(
+    CPDF_IndirectObjectHolder* pObjList,
+    uint32_t object_offset) const {
+  FX_SAFE_FILESIZE offset_in_stream = first_object_offset_;
+  offset_in_stream += object_offset;
+
+  if (!offset_in_stream.IsValid())
+    return nullptr;
+
+  if (offset_in_stream.ValueOrDie() >= data_stream_->GetSize())
+    return nullptr;
+
+  CPDF_SyntaxParser syntax;
+  syntax.InitParser(data_stream_, 0);
+  syntax.SetPos(offset_in_stream.ValueOrDie());
+  return syntax.GetObjectBody(pObjList);
+}
diff --git a/core/fpdfapi/parser/cpdf_object_stream.h b/core/fpdfapi/parser/cpdf_object_stream.h
new file mode 100644
index 0000000000..816c1be77e
--- /dev/null
+++ b/core/fpdfapi/parser/cpdf_object_stream.h
@@ -0,0 +1,52 @@
+// Copyright 2018 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CORE_FPDFAPI_PARSER_CPDF_OBJECT_STREAM_H_
+#define CORE_FPDFAPI_PARSER_CPDF_OBJECT_STREAM_H_
+
+#include <map>
+#include <memory>
+#include <vector>
+
+#include "core/fpdfapi/parser/cpdf_object.h"
+#include "core/fxcrt/retain_ptr.h"
+
+class CPDF_IndirectObjectHolder;
+class CPDF_Stream;
+class CPDF_StreamAcc;
+class IFX_SeekableReadStream;
+
+// Implementation of logic of PDF "Object Streams".
+// See "PDF 32000-1:2008" Spec. section 7.5.7.
+class CPDF_ObjectStream {
+ public:
+  static bool IsObjectsStreamObject(const CPDF_Object* object);
+
+  static std::unique_ptr<CPDF_ObjectStream> Create(const CPDF_Stream* stream);
+
+  ~CPDF_ObjectStream();
+
+  uint32_t obj_num() const { return obj_num_; }
+  uint32_t extends_obj_num() const { return extends_obj_num_; }
+
+  bool HasObject(uint32_t obj_number) const;
+  std::unique_ptr<CPDF_Object> ParseObject(CPDF_IndirectObjectHolder* pObjList,
+                                           uint32_t obj_number) const;
+
+ protected:
+  explicit CPDF_ObjectStream(const CPDF_Stream* stream);
+
+  void Init(const CPDF_Stream* stream);
+  std::unique_ptr<CPDF_Object> ParseObjectAtOffset(
+      CPDF_IndirectObjectHolder* pObjList,
+      uint32_t object_offset) const;
+
+  uint32_t obj_num_ = CPDF_Object::kInvalidObjNum;
+  uint32_t extends_obj_num_ = CPDF_Object::kInvalidObjNum;
+  RetainPtr<IFX_SeekableReadStream> data_stream_;
+  int first_object_offset_ = 0;
+  std::map<uint32_t, uint32_t> objects_offsets_;
+};
+
+#endif  // CORE_FPDFAPI_PARSER_CPDF_OBJECT_STREAM_H_
diff --git a/core/fpdfapi/parser/cpdf_parser.cpp b/core/fpdfapi/parser/cpdf_parser.cpp
index 73b4bcdc0c..6cdd6ab789 100644
--- a/core/fpdfapi/parser/cpdf_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_parser.cpp
@@ -16,6 +16,7 @@
 #include "core/fpdfapi/parser/cpdf_document.h"
 #include "core/fpdfapi/parser/cpdf_linearized_header.h"
 #include "core/fpdfapi/parser/cpdf_number.h"
+#include "core/fpdfapi/parser/cpdf_object_stream.h"
 #include "core/fpdfapi/parser/cpdf_read_validator.h"
 #include "core/fpdfapi/parser/cpdf_reference.h"
 #include "core/fpdfapi/parser/cpdf_security_handler.h"
@@ -46,14 +47,6 @@ uint32_t GetVarInt(const uint8_t* p, int32_t n) {
   return result;
 }
 
-int32_t GetStreamNCount(const RetainPtr<CPDF_StreamAcc>& pObjStream) {
-  return pObjStream->GetDict()->GetIntegerFor("N");
-}
-
-int32_t GetStreamFirst(const RetainPtr<CPDF_StreamAcc>& pObjStream) {
-  return pObjStream->GetDict()->GetIntegerFor("First");
-}
-
 }  // namespace
 
 class CPDF_Parser::TrailerData {
@@ -1198,8 +1191,7 @@ std::unique_ptr<CPDF_Object> CPDF_Parser::ParseIndirectObject(
     return nullptr;
 
   pdfium::ScopedSetInsertion<uint32_t> local_insert(&m_ParsingObjNums, objnum);
-  if (GetObjectType(objnum) == ObjectType::kNotCompressed ||
-      GetObjectType(objnum) == ObjectType::kNull) {
+  if (GetObjectType(objnum) == ObjectType::kNotCompressed) {
     FX_FILESIZE pos = m_ObjectInfo[objnum].pos;
     if (pos <= 0)
       return nullptr;
@@ -1208,52 +1200,43 @@ std::unique_ptr<CPDF_Object> CPDF_Parser::ParseIndirectObject(
   if (GetObjectType(objnum) != ObjectType::kCompressed)
     return nullptr;
 
-  RetainPtr<CPDF_StreamAcc> pObjStream =
-      GetObjectStream(m_ObjectInfo[objnum].pos);
+  const CPDF_ObjectStream* pObjStream =
+      GetObjectStream(pObjList, m_ObjectInfo[objnum].pos);
   if (!pObjStream)
     return nullptr;
 
-  auto file = pdfium::MakeRetain<CFX_MemoryStream>(
-      const_cast<uint8_t*>(pObjStream->GetData()),
-      static_cast<size_t>(pObjStream->GetSize()), false);
-  CPDF_SyntaxParser syntax;
-  syntax.InitParser(file, 0);
-  const int32_t offset = GetStreamFirst(pObjStream);
-
-  // Read object numbers from |pObjStream| into a cache.
-  if (!pdfium::ContainsKey(m_ObjCache, pObjStream)) {
-    for (int32_t i = GetStreamNCount(pObjStream); i > 0; --i) {
-      uint32_t thisnum = syntax.GetDirectNum();
-      uint32_t thisoff = syntax.GetDirectNum();
-      m_ObjCache[pObjStream][thisnum] = thisoff;
-    }
-  }
+  return pObjStream->ParseObject(pObjList, objnum);
+}
 
-  const auto it = m_ObjCache[pObjStream].find(objnum);
-  if (it == m_ObjCache[pObjStream].end())
+const CPDF_ObjectStream* CPDF_Parser::GetObjectStream(
+    CPDF_IndirectObjectHolder* pObjList,
+    uint32_t object_number) {
+  // Prevent circular parsing the same object.
+  if (pdfium::ContainsKey(m_ParsingObjNums, object_number))
     return nullptr;
 
-  syntax.SetPos(offset + it->second);
-  return syntax.GetObjectBody(pObjList);
-}
+  pdfium::ScopedSetInsertion<uint32_t> local_insert(&m_ParsingObjNums,
+                                                    object_number);
 
-RetainPtr<CPDF_StreamAcc> CPDF_Parser::GetObjectStream(uint32_t objnum) {
-  auto it = m_ObjectStreamMap.find(objnum);
+  auto it = m_ObjectStreamMap.find(object_number);
   if (it != m_ObjectStreamMap.end())
-    return it->second;
+    return it->second.get();
 
-  if (!m_pDocument)
+  const FX_FILESIZE object_pos = GetObjectPositionOrZero(object_number);
+  if (object_pos <= 0)
     return nullptr;
 
-  const CPDF_Stream* pStream =
-      ToStream(m_pDocument->GetOrParseIndirectObject(objnum));
-  if (!pStream)
+  std::unique_ptr<CPDF_Object> object =
+      ParseIndirectObjectAt(pObjList, object_pos, object_number);
+  if (!object)
     return nullptr;
 
-  auto pStreamAcc = pdfium::MakeRetain<CPDF_StreamAcc>(pStream);
-  pStreamAcc->LoadAllDataFiltered();
-  m_ObjectStreamMap[objnum] = pStreamAcc;
-  return pStreamAcc;
+  std::unique_ptr<CPDF_ObjectStream> objs_stream =
+      CPDF_ObjectStream::Create(ToStream(object.get()));
+  const CPDF_ObjectStream* result = objs_stream.get();
+  m_ObjectStreamMap[object_number] = std::move(objs_stream);
+
+  return result;
 }
 
 std::unique_ptr<CPDF_Object> CPDF_Parser::ParseIndirectObjectAt(
@@ -1437,7 +1420,6 @@ CPDF_Parser::Error CPDF_Parser::LoadLinearizedMainXRefTable() {
   const AutoRestorer<uint32_t> save_metadata_objnum(&m_MetadataObjnum);
   m_MetadataObjnum = 0;
   m_ObjectStreamMap.clear();
-  m_ObjCache.clear();
 
   if (!LoadLinearizedAllCrossRefV4(main_xref_offset.ValueOrDie()) &&
       !LoadLinearizedAllCrossRefV5(main_xref_offset.ValueOrDie())) {
diff --git a/core/fpdfapi/parser/cpdf_parser.h b/core/fpdfapi/parser/cpdf_parser.h
index 5f0a4a1cf3..705fad9bdb 100644
--- a/core/fpdfapi/parser/cpdf_parser.h
+++ b/core/fpdfapi/parser/cpdf_parser.h
@@ -26,9 +26,9 @@ class CPDF_Document;
 class CPDF_IndirectObjectHolder;
 class CPDF_LinearizedHeader;
 class CPDF_Object;
+class CPDF_ObjectStream;
 class CPDF_ReadValidator;
 class CPDF_SecurityHandler;
-class CPDF_StreamAcc;
 class CPDF_SyntaxParser;
 class IFX_SeekableReadStream;
 
@@ -172,7 +172,8 @@ class CPDF_Parser {
   bool LoadLinearizedAllCrossRefV4(FX_FILESIZE pos);
   bool LoadLinearizedAllCrossRefV5(FX_FILESIZE pos);
   Error LoadLinearizedMainXRefTable();
-  RetainPtr<CPDF_StreamAcc> GetObjectStream(uint32_t number);
+  const CPDF_ObjectStream* GetObjectStream(CPDF_IndirectObjectHolder* pObjList,
+                                           uint32_t object_number);
   std::unique_ptr<CPDF_LinearizedHeader> ParseLinearizedHeader();
   void SetEncryptDictionary(CPDF_Dictionary* pDict);
   void ShrinkObjectMap(uint32_t size);
@@ -218,15 +219,7 @@ class CPDF_Parser {
   std::unique_ptr<CPDF_LinearizedHeader> m_pLinearized;
 
   // A map of object numbers to indirect streams.
-  std::map<uint32_t, RetainPtr<CPDF_StreamAcc>> m_ObjectStreamMap;
-
-  // Mapping of object numbers to offsets. The offsets are relative to the first
-  // object in the stream.
-  using StreamObjectCache = std::map<uint32_t, uint32_t>;
-
-  // Mapping of streams to their object caches. This is valid as long as the
-  // streams in |m_ObjectStreamMap| are valid.
-  std::map<RetainPtr<CPDF_StreamAcc>, StreamObjectCache> m_ObjCache;
+  std::map<uint32_t, std::unique_ptr<CPDF_ObjectStream>> m_ObjectStreamMap;
 
   // All indirect object numbers that are being parsed.
   std::set<uint32_t> m_ParsingObjNums;
diff --git a/core/fpdfapi/parser/cpdf_syntax_parser.h b/core/fpdfapi/parser/cpdf_syntax_parser.h
index 5aad2e463c..ed760934b9 100644
--- a/core/fpdfapi/parser/cpdf_syntax_parser.h
+++ b/core/fpdfapi/parser/cpdf_syntax_parser.h
@@ -60,6 +60,7 @@ class CPDF_SyntaxParser {
   const RetainPtr<CPDF_ReadValidator>& GetValidator() const {
     return m_pFileAccess;
   }
+  uint32_t GetDirectNum();
 
  private:
   friend class CPDF_Parser;
@@ -69,7 +70,6 @@ class CPDF_SyntaxParser {
   static const int kParserMaxRecursionDepth = 64;
   static int s_CurrentRecursionDepth;
 
-  uint32_t GetDirectNum();
   bool ReadBlockAt(FX_FILESIZE read_pos);
   bool GetNextChar(uint8_t& ch);
   bool GetCharAtBackward(FX_FILESIZE pos, uint8_t* ch);