From e3d3ce04e585c4a6c5596056bdf1ced639c763d7 Mon Sep 17 00:00:00 2001
From: Artem Strygin <art-snake@yandex-team.ru>
Date: Tue, 26 Jun 2018 16:01:38 +0000
Subject: 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>
---
 core/fpdfapi/parser/cpdf_object_stream.cpp | 136 +++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)
 create mode 100644 core/fpdfapi/parser/cpdf_object_stream.cpp

(limited to 'core/fpdfapi/parser/cpdf_object_stream.cpp')

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);
+}
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