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

fpdfsdk/fpdf_dataavail.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 "public/fpdf_dataavail.h"
 
 #include <memory>
 #include <utility>
 
 #include "core/fpdfapi/parser/cpdf_data_avail.h"
 #include "core/fpdfapi/parser/cpdf_document.h"
+#include "core/fxcrt/fx_safe_types.h"
 #include "fpdfsdk/fsdk_define.h"
 #include "public/fpdf_formfill.h"
+#include "third_party/base/numerics/safe_conversions_impl.h"
 #include "third_party/base/ptr_util.h"
 
 // These checks are here because core/ and public/ cannot depend on each other.
 static_assert(CPDF_DataAvail::DataError == PDF_DATA_ERROR,
               "CPDF_DataAvail::DataError value mismatch");
 static_assert(CPDF_DataAvail::DataNotAvailable == PDF_DATA_NOTAVAIL,
               "CPDF_DataAvail::DataNotAvailable value mismatch");
 static_assert(CPDF_DataAvail::DataAvailable == PDF_DATA_AVAIL,
               "CPDF_DataAvail::DataAvailable value mismatch");
 
@@ skipping 26 matching lines @@
   bool IsDataAvail(FX_FILESIZE offset, uint32_t size) override {
     return !!m_pfileAvail->IsDataAvail(m_pfileAvail, offset, size);
   }
 
  private:
   FX_FILEAVAIL* m_pfileAvail;
 };
 
 class CFPDF_FileAccessWrap : public IFX_SeekableReadStream {
  public:
-  CFPDF_FileAccessWrap() { m_pFileAccess = nullptr; }
+  CFPDF_FileAccessWrap() {
+    m_pFileAccess = nullptr;
+    m_nCurPos = 0;
+  }
   ~CFPDF_FileAccessWrap() override {}
 
   void Set(FPDF_FILEACCESS* pFile) { m_pFileAccess = pFile; }
 
-  // IFX_SeekableReadStream
+  bool IsEOF() override {
+    return m_nCurPos >=
+           pdfium::base::checked_cast<FX_FILESIZE>(m_pFileAccess->m_FileLen);
+  }
+
+  // IFX_FileRead
   FX_FILESIZE GetSize() override { return m_pFileAccess->m_FileLen; }
 
-  bool ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override {
-    return !!m_pFileAccess->m_GetBlock(m_pFileAccess->m_Param, offset,
-                                       (uint8_t*)buffer, size);
+  size_t ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override {
+    int blockSize = m_pFileAccess->m_GetBlock(m_pFileAccess->m_Param, offset,
+                                              (uint8_t*)buffer, size);
+    m_nCurPos = offset + pdfium::base::checked_cast<FX_FILESIZE>(blockSize);
+    return pdfium::base::checked_cast<size_t>(blockSize);
   }
 
   void Release() override {}
 
  private:
   FPDF_FILEACCESS* m_pFileAccess;
+  FX_FILESIZE m_nCurPos;
 };
 
 class CFPDF_DownloadHintsWrap : public CPDF_DataAvail::DownloadHints {
  public:
   explicit CFPDF_DownloadHintsWrap(FX_DOWNLOADHINTS* pDownloadHints) {
     m_pDownloadHints = pDownloadHints;
   }
   ~CFPDF_DownloadHintsWrap() override {}
 
  public:
@@ skipping 91 matching lines @@
   CFPDF_DownloadHintsWrap hints_wrap(hints);
   return CFPDFDataAvailFromFPDFAvail(avail)->m_pDataAvail->IsFormAvail(
       &hints_wrap);
 }
 
 DLLEXPORT int STDCALL FPDFAvail_IsLinearized(FPDF_AVAIL avail) {
   if (!avail)
     return PDF_LINEARIZATION_UNKNOWN;
   return CFPDFDataAvailFromFPDFAvail(avail)->m_pDataAvail->IsLinearizedPDF();
 }