Unify some code

core/fpdfapi/parser/cpdf_linearized.cpp

+// Copyright 2016 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.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#include "core/fpdfapi/parser/cpdf_linearized.h"
+
+#include <algorithm>
+
+#include "core/fpdfapi/parser/cpdf_array.h"
+#include "core/fpdfapi/parser/cpdf_dictionary.h"
+#include "third_party/base/ptr_util.h"
+
+// static
+std::unique_ptr<CPDF_Linearized> CPDF_Linearized::CreateForObject(
+    std::unique_ptr<CPDF_Object, ReleaseDeleter<CPDF_Object>> pObj) {
+  UniqueDictionary pDict = ToDictionary(std::move(pObj));
+  if (!pDict || !pDict->GetObjectFor("Linearized"))
+    return nullptr;
+  auto result = pdfium::WrapUnique(new CPDF_Linearized(pDict.get()));
+  if (result->IsValid())
+    return result;
+  return nullptr;
+}
+
+CPDF_Linearized::CPDF_Linearized(const CPDF_Dictionary* pDict) {
+  m_szFileSize = std::max(pDict->GetIntegerFor("L"), 0);
+  m_dwFirstPageNo = std::max(pDict->GetIntegerFor("P"), 0);
+  m_szLastXRefOffset = std::max(pDict->GetIntegerFor("T"), 0);
+  m_PageCount = std::max(pDict->GetIntegerFor("N"), 0);
+  m_szFirstPageEndOffset = std::max(pDict->GetIntegerFor("E"), 0);
+  m_FirstPageObjNum = std::max(pDict->GetIntegerFor("O"), 0);
+  const CPDF_Array* pHintStreamRange = pDict->GetArrayFor("H");
+  const size_t nHintStreamSize =
+      pHintStreamRange ? pHintStreamRange->GetCount() : 0;
+  if (nHintStreamSize == 2 || nHintStreamSize == 4) {
+    m_szHintStart = std::max(pHintStreamRange->GetIntegerAt(0), 0);
+    m_szHintLength = std::max(pHintStreamRange->GetIntegerAt(1), 0);
+  }
+}
+
+CPDF_Linearized::~CPDF_Linearized() {}
+
+bool CPDF_Linearized::IsValid() const {
+  return GetFileSize() > 0 && GetFirstPageEndOffset() > 0 &&
+         GetPageCount() > 0 && (GetPageCount() == 1 || GetLastXRefOffset() > 0);

[Lei Zhang, 2016/11/03 17:18:00]

Why did you decide GetLastXRefOffset() can be 0 when the page count is 1?

[snake, 2016/11/03 17:50:34]

LastXRefOffset is offset to MainXRefTable, but if linearized document contains
only one page, that we can have only first page xref table. If we have main xref
table, it will be empty, and not necessary to parse it.

+}
+
+bool CPDF_Linearized::HasHintTable() const {
+  return GetPageCount() > 1 && GetHintStart() > 0 && GetHintLength() > 0;
+}