From 437e5e4f03ea190c195c35a6cfdefef03cb50d10 Mon Sep 17 00:00:00 2001
From: Artem Strygin <art-snake@yandex-team.ru>
Date: Wed, 13 Jun 2018 18:37:56 +0000
Subject: Merge the offset calculation logic within  CPDF_HintsTable.

Change-Id: If120ee16c53117ae148447e141cbbd8143194b36
Reviewed-on: https://pdfium-review.googlesource.com/15811
Commit-Queue: Art Snake <art-snake@yandex-team.ru>
Reviewed-by: dsinclair <dsinclair@chromium.org>
---
 core/fpdfapi/parser/cpdf_hint_tables.cpp | 50 ++++++++++++++++++--------------
 core/fpdfapi/parser/cpdf_hint_tables.h   |  2 ++
 2 files changed, 30 insertions(+), 22 deletions(-)

diff --git a/core/fpdfapi/parser/cpdf_hint_tables.cpp b/core/fpdfapi/parser/cpdf_hint_tables.cpp
index a85fb2b052..a412fdc34d 100644
--- a/core/fpdfapi/parser/cpdf_hint_tables.cpp
+++ b/core/fpdfapi/parser/cpdf_hint_tables.cpp
@@ -62,9 +62,6 @@ bool CPDF_HintTables::ReadPageHintTable(CFX_BitStream* hStream) {
   if (!hStream || hStream->IsEOF())
     return false;
 
-  const FX_FILESIZE nStreamOffset = m_pLinearized->GetHintStart();
-  const uint32_t nStreamLen = m_pLinearized->GetHintLength();
-
   const uint32_t kHeaderSize = 288;
   if (hStream->BitsRemaining() < kHeaderSize)
     return false;
@@ -75,18 +72,12 @@ bool CPDF_HintTables::ReadPageHintTable(CFX_BitStream* hStream) {
     return false;
 
   // Item 2: The location of the first page's page object.
-  const uint32_t dwFirstObjLoc = hStream->GetBits(32);
-  if (dwFirstObjLoc > static_cast<uint32_t>(nStreamOffset)) {
-    FX_SAFE_FILESIZE safeLoc = nStreamLen;
-    safeLoc += dwFirstObjLoc;
-    if (!safeLoc.IsValid())
-      return false;
-    m_szFirstPageObjOffset = safeLoc.ValueOrDie();
-  } else {
-    if (!pdfium::base::IsValueInRangeForNumericType<FX_FILESIZE>(dwFirstObjLoc))
-      return false;
-    m_szFirstPageObjOffset = dwFirstObjLoc;
-  }
+  const FX_FILESIZE szFirstObjLoc =
+      HintsOffsetToFileOffset(hStream->GetBits(32));
+  if (!szFirstObjLoc)
+    return false;
+
+  m_szFirstPageObjOffset = szFirstObjLoc;
 
   // Item 3: The number of bits needed to represent the difference
   // between the greatest and least number of objects in a page.
@@ -238,9 +229,6 @@ bool CPDF_HintTables::ReadSharedObjHintTable(CFX_BitStream* hStream,
   if (!hStream || hStream->IsEOF())
     return false;
 
-  const FX_FILESIZE nStreamOffset = m_pLinearized->GetHintStart();
-  const uint32_t nStreamLen = m_pLinearized->GetHintLength();
-
   FX_SAFE_UINT32 bit_offset = offset;
   bit_offset *= 8;
   if (!bit_offset.IsValid() || hStream->GetPos() > bit_offset.ValueOrDie())
@@ -256,9 +244,10 @@ bool CPDF_HintTables::ReadSharedObjHintTable(CFX_BitStream* hStream,
   uint32_t dwFirstSharedObjNum = hStream->GetBits(32);
 
   // Item 2: The location of the first object in the shared objects section.
-  uint32_t dwFirstSharedObjLoc = hStream->GetBits(32);
-  if (dwFirstSharedObjLoc > static_cast<uint32_t>(nStreamOffset))
-    dwFirstSharedObjLoc += nStreamLen;
+  const FX_FILESIZE szFirstSharedObjLoc =
+      HintsOffsetToFileOffset(hStream->GetBits(32));
+  if (!szFirstSharedObjLoc)
+    return false;
 
   // Item 3: The number of shared object entries for the first page.
   m_nFirstPageSharedObjs = hStream->GetBits(32);
@@ -318,7 +307,7 @@ bool CPDF_HintTables::ReadSharedObjHintTable(CFX_BitStream* hStream,
 
       m_dwSharedObjNumArray.push_back(safeObjNum.ValueOrDie());
       if (i == m_nFirstPageSharedObjs) {
-        FX_SAFE_FILESIZE safeLoc = dwFirstSharedObjLoc;
+        FX_SAFE_FILESIZE safeLoc = szFirstSharedObjLoc;
         if (!safeLoc.IsValid())
           return false;
 
@@ -464,3 +453,20 @@ bool CPDF_HintTables::LoadHintStream(CPDF_Stream* pHintStream) {
   return ReadPageHintTable(&bs) &&
          ReadSharedObjHintTable(&bs, shared_hint_table_offset);
 }
+
+FX_FILESIZE CPDF_HintTables::HintsOffsetToFileOffset(
+    uint32_t hints_offset) const {
+  FX_SAFE_FILESIZE file_offset = hints_offset;
+  if (!file_offset.IsValid())
+    return 0;
+
+  // The resulting positions shall be interpreted as if the primary hint stream
+  // itself were not present. That is, a position greater than the hint stream
+  // offset shall have the hint stream length added to it to determine the
+  // actual offset relative to the beginning of the file.
+  // See specification PDF 32000-1:2008 Annex F.4 (Hint tables).
+  if (file_offset.ValueOrDie() > m_pLinearized->GetHintStart())
+    file_offset += m_pLinearized->GetHintLength();
+
+  return file_offset.ValueOrDefault(0);
+}
diff --git a/core/fpdfapi/parser/cpdf_hint_tables.h b/core/fpdfapi/parser/cpdf_hint_tables.h
index 3664e1517c..c51d95a255 100644
--- a/core/fpdfapi/parser/cpdf_hint_tables.h
+++ b/core/fpdfapi/parser/cpdf_hint_tables.h
@@ -41,6 +41,8 @@ class CPDF_HintTables {
   uint32_t GetItemLength(uint32_t index,
                          const std::vector<FX_FILESIZE>& szArray) const;
 
+  FX_FILESIZE HintsOffsetToFileOffset(uint32_t hints_offset) const;
+
   // Owned by |m_pDataAvail|.
   UnownedPtr<CPDF_ReadValidator> m_pValidator;
 
-- 
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