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

xfa/fxfa/app/xfa_ffapp.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/fxfa/xfa_ffapp.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "xfa/fgas/font/fgas_stdfontmgr.h"
 #include "xfa/fwl/core/cfwl_widgetmgr.h"
 #include "xfa/fwl/core/fwl_noteimp.h"
 #include "xfa/fxfa/app/xfa_fwladapter.h"
 #include "xfa/fxfa/app/xfa_fwltheme.h"
 #include "xfa/fxfa/xfa_ffdoc.h"
 #include "xfa/fxfa/xfa_ffdochandler.h"
 #include "xfa/fxfa/xfa_ffwidgethandler.h"
 #include "xfa/fxfa/xfa_fontmgr.h"
 
 CXFA_FileRead::CXFA_FileRead(const std::vector<CPDF_Stream*>& streams) {
+  m_FileSize = 0;
+  m_nCurPos = 0;
   for (CPDF_Stream* pStream : streams) {
     CPDF_StreamAcc& acc = m_Data.Add();
     acc.LoadAllData(pStream);
+    m_FileSize += pdfium::base::checked_cast<FX_FILESIZE>(acc.GetSize());
   }
 }
 
 CXFA_FileRead::~CXFA_FileRead() {}
 
-FX_FILESIZE CXFA_FileRead::GetSize() {
-  uint32_t dwSize = 0;
-  int32_t iCount = m_Data.GetSize();
-  for (int32_t i = 0; i < iCount; i++) {
-    CPDF_StreamAcc& acc = m_Data[i];
-    dwSize += acc.GetSize();
-  }
-  return dwSize;
+bool CXFA_FileRead::IsEOF() {
+  return m_nCurPos >= GetSize();
 }
 
-bool CXFA_FileRead::ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) {
+FX_FILESIZE CXFA_FileRead::GetSize() {
+  return m_FileSize;
+}
+
+size_t CXFA_FileRead::ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) {
+  if (offset < 0 || GetSize() < offset) {
+    return 0;
+  }
+  size_t readSize =
+      std::min(pdfium::base::checked_cast<size_t>(GetSize() - offset), size);
   int32_t iCount = m_Data.GetSize();
   int32_t index = 0;
   while (index < iCount) {
     CPDF_StreamAcc& acc = m_Data[index];
     FX_FILESIZE dwSize = acc.GetSize();
     if (offset < dwSize) {
       break;
     }
     offset -= dwSize;
     index++;
   }
   while (index < iCount) {
     CPDF_StreamAcc& acc = m_Data[index];
     uint32_t dwSize = acc.GetSize();
     size_t dwRead = std::min(size, static_cast<size_t>(dwSize - offset));
     FXSYS_memcpy(buffer, acc.GetData() + offset, dwRead);
     size -= dwRead;
     if (size == 0) {
-      return true;
+      break;
     }
     buffer = (uint8_t*)buffer + dwRead;
     offset = 0;
     index++;
   }
-  return false;
+  return readSize;
 }
 
 void CXFA_FileRead::Release() {
   delete this;
 }
 
 CXFA_FFApp::CXFA_FFApp(IXFA_AppProvider* pProvider)
     : m_pProvider(pProvider),
       m_pWidgetMgrDelegate(nullptr),
       m_pFWLApp(new IFWL_App(this)) {
@@ skipping 67 matching lines @@
   return m_pAdapterWidgetMgr.get();
 }
 
 IFWL_AdapterTimerMgr* CXFA_FFApp::GetTimerMgr() const {
   return m_pProvider->GetTimerMgr();
 }
 
 void CXFA_FFApp::ClearEventTargets() {
   m_pFWLApp->GetNoteDriver()->ClearEventTargets(false);
 }