in the attempt to fix 627393, changed IFX_FileRead's readBlock to return the length it reads

core/fpdfapi/parser/cpdf_syntax_parser.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_syntax_parser.h"
 
 #include <vector>
 
@@ skipping 46 matching lines @@
 
 bool CPDF_SyntaxParser::ReadChar(FX_FILESIZE read_pos, uint32_t read_size) {
   if (static_cast<FX_FILESIZE>(read_pos + read_size) > m_FileLen) {
     if (m_FileLen < static_cast<FX_FILESIZE>(read_size)) {
       read_pos = 0;
       read_size = static_cast<uint32_t>(m_FileLen);
     } else {
       read_pos = m_FileLen - read_size;
     }
   }
-  if (!m_pFileAccess->ReadBlock(m_pFileBuf, read_pos, read_size))
+  if (m_pFileAccess->ReadBlock(m_pFileBuf, read_pos, read_size) != read_size &&
+      !m_pFileAccess->IsEOF())
     return false;
 
   m_BufOffset = read_pos;
   return true;
 }
 
 bool CPDF_SyntaxParser::GetNextChar(uint8_t& ch) {
   FX_FILESIZE pos = m_Pos + m_HeaderOffset;
   if (pos >= m_FileLen)
     return false;
@@ skipping 23 matching lines @@
       read_pos = pos - m_BufSize + 1;
     uint32_t read_size = m_BufSize;
     if (!ReadChar(read_pos, read_size))
       return false;
   }
   ch = m_pFileBuf[pos - m_BufOffset];
   return true;
 }
 
 bool CPDF_SyntaxParser::ReadBlock(uint8_t* pBuf, uint32_t size) {
-  if (!m_pFileAccess->ReadBlock(pBuf, m_Pos + m_HeaderOffset, size))
+  uint32_t readSize =
+      m_pFileAccess->ReadBlock(pBuf, m_Pos + m_HeaderOffset, size);
+  if (readSize != size && !m_pFileAccess->IsEOF())
     return false;
-  m_Pos += size;
+  m_Pos += readSize;
   return true;
 }
 
 void CPDF_SyntaxParser::GetNextWordInternal(bool* bIsNumber) {
   m_WordSize = 0;
   if (bIsNumber)
     *bIsNumber = true;
 
   uint8_t ch;
   if (!GetNextChar(ch))
@@ skipping 789 matching lines @@
 }
 
 void CPDF_SyntaxParser::SetEncrypt(
     std::unique_ptr<CPDF_CryptoHandler> pCryptoHandler) {
   m_pCryptoHandler = std::move(pCryptoHandler);
 }
 
 CFX_ByteString CPDF_SyntaxParser::MaybeIntern(const CFX_ByteString& str) {
   return m_pPool ? m_pPool->Intern(str) : str;
 }