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

core/fxcrt/fx_xml_parser.cpp

 // Copyright 2014 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/fxcrt/xml_int.h"
 
 #include <vector>
 
@@ skipping 78 matching lines @@
   m_nStart += (FX_FILESIZE)m_dwSize;
   if (m_nStart >= nLength) {
     return FALSE;
   }
   static const FX_FILESIZE FX_XMLDATASTREAM_BufferSize = 32 * 1024;
   m_dwSize = static_cast<size_t>(
       std::min(FX_XMLDATASTREAM_BufferSize, nLength - m_nStart));
   if (!m_pBuffer) {
     m_pBuffer = FX_Alloc(uint8_t, m_dwSize);
   }
-  return m_pFileRead->ReadBlock(m_pBuffer, m_nStart, m_dwSize);
+  return m_pFileRead->ReadBlock(m_pBuffer, m_nStart, m_dwSize) == m_dwSize ||
+         m_pFileRead->IsEOF();
 }
 
 const uint8_t* CXML_DataStmAcc::GetBlockBuffer() {
   return (const uint8_t*)m_pBuffer;
 }
 
 size_t CXML_DataStmAcc::GetBlockSize() {
   return m_dwSize;
 }
 
@@ skipping 796 matching lines @@
   m_pMap->push_back({space, name, CFX_WideString(value)});
 }
 
 int CXML_AttrMap::GetSize() const {
   return m_pMap ? pdfium::CollectionSize<int>(*m_pMap) : 0;
 }
 
 CXML_AttrItem& CXML_AttrMap::GetAt(int index) const {
   return (*m_pMap)[index];
 }