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

xfa/fxfa/app/xfa_ffapp.cpp

Index: xfa/fxfa/app/xfa_ffapp.cpp
diff --git a/xfa/fxfa/app/xfa_ffapp.cpp b/xfa/fxfa/app/xfa_ffapp.cpp
index 9e86c3aa68cf212ffd0a0aadae5751b0fa955d9a..1456ca2a7aae9ed0911dec25385a7c2efa3e9b95 100644
--- a/xfa/fxfa/app/xfa_ffapp.cpp
+++ b/xfa/fxfa/app/xfa_ffapp.cpp
@@ -19,28 +19,31 @@
 #include "xfa/fxfa/include/xfa_fontmgr.h"
 
 CXFA_FileRead::CXFA_FileRead(const CFX_ArrayTemplate<CPDF_Stream*>& streams) {
+  m_FileSize = 0;
+  m_nCurPos = 0;
   int32_t iCount = streams.GetSize();
   for (int32_t i = 0; i < iCount; i++) {
     CPDF_StreamAcc& acc = m_Data.Add();
     acc.LoadAllData(streams[i]);
+    m_FileSize += acc.GetSize();
   }
 }
 
 CXFA_FileRead::~CXFA_FileRead() {}
 
+FX_BOOL CXFA_FileRead::IsEOF() {
+  return m_nCurPos >= GetSize();
+}
+
 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;
+  return m_FileSize;
 }
 
-FX_BOOL CXFA_FileRead::ReadBlock(void* buffer,
-                                 FX_FILESIZE offset,
-                                 size_t size) {
+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(static_cast<size_t>(GetSize() - offset), size);
   int32_t iCount = m_Data.GetSize();
   int32_t index = 0;
   while (index < iCount) {
@@ -59,13 +62,13 @@ FX_BOOL CXFA_FileRead::ReadBlock(void* buffer,
     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() {