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

xfa/fde/xml/cfx_saxreader.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 "xfa/fde/xml/cfx_saxreader.h"
 
 #include <algorithm>
 #include <utility>
@@ skipping 68 matching lines @@
     return false;
   }
   if (dwLen == static_cast<uint32_t>(-1) || dwStart + dwLen > dwSize) {
     dwLen = dwSize - dwStart;
   }
   if (dwLen == 0) {
     return false;
   }
   m_dwBufSize = std::min(dwLen, kSaxFileBufSize);
   m_pBuf = FX_Alloc(uint8_t, m_dwBufSize);
-  if (!pFile->ReadBlock(m_pBuf, dwStart, m_dwBufSize)) {
+  if (pFile->ReadBlock(m_pBuf, dwStart, m_dwBufSize) != m_dwBufSize &&
+      !pFile->IsEOF()) {
     return false;
   }
   m_dwStart = dwStart;
   m_dwEnd = dwStart + dwLen;
   m_dwCur = dwStart;
   m_pFile = pFile;
   m_dwBufIndex = 0;
   return true;
 }
 
 bool CFX_SAXFile::ReadNextBlock() {
   ASSERT(m_pFile);
   uint32_t dwSize = m_dwEnd - m_dwCur;
   if (dwSize == 0) {
     return false;
   }
   m_dwBufSize = std::min(dwSize, kSaxFileBufSize);
-  if (!m_pFile->ReadBlock(m_pBuf, m_dwCur, m_dwBufSize)) {
+  if (m_pFile->ReadBlock(m_pBuf, m_dwCur, m_dwBufSize) != m_dwBufSize &&
+      !m_pFile->IsEOF()) {
     return false;
   }
   m_dwBufIndex = 0;
   return true;
 }
 
 void CFX_SAXFile::Reset() {
   if (m_pBuf) {
     FX_Free(m_pBuf);
     m_pBuf = nullptr;
@@ skipping 609 matching lines @@
   CFX_SAXItem* pItem = GetCurrentItem();
   if (!pItem)
     return;
 
   pItem->m_bSkip = true;
 }
 
 void CFX_SAXReader::SetHandler(CXFA_SAXReaderHandler* pHandler) {
   m_pHandler = pHandler;
 }