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

fpdfsdk/fpdfview.cpp

Index: fpdfsdk/fpdfview.cpp
diff --git a/fpdfsdk/fpdfview.cpp b/fpdfsdk/fpdfview.cpp
index 3c60ab0041cf07db61fb4051b992955c70ffd14a..ed502872a01f412a5a442c29d8b602ac87fb435e 100644
--- a/fpdfsdk/fpdfview.cpp
+++ b/fpdfsdk/fpdfview.cpp
@@ -118,18 +118,18 @@ FX_FILESIZE CFPDF_FileStream::GetPosition() {
   return m_nCurPos;
 }
 
-FX_BOOL CFPDF_FileStream::ReadBlock(void* buffer,
-                                    FX_FILESIZE offset,
-                                    size_t size) {
+size_t CFPDF_FileStream::ReadBlock(void* buffer,
+                                   FX_FILESIZE offset,
+                                   size_t size) {
   if (!buffer || !size || !m_pFS->ReadBlock)
-    return FALSE;
+    return 0;
 
   if (m_pFS->ReadBlock(m_pFS->clientData, (FPDF_DWORD)offset, buffer,
                        (FPDF_DWORD)size) == 0) {
     m_nCurPos = offset + size;
-    return TRUE;
+    return size;
   }
-  return FALSE;
+  return 0;
 }
 
 size_t CFPDF_FileStream::ReadBlock(void* buffer, size_t size) {
@@ -175,6 +175,7 @@ FX_BOOL CFPDF_FileStream::Flush() {
 
 CPDF_CustomAccess::CPDF_CustomAccess(FPDF_FILEACCESS* pFileAccess) {
   m_FileAccess = *pFileAccess;
+  m_nCurPos = 0;
 #ifdef PDF_ENABLE_XFA
   m_BufferOffset = (uint32_t)-1;
 #endif  // PDF_ENABLE_XFA
@@ -220,21 +221,26 @@ void CPDF_CustomAccess::Release() {
   delete this;
 }
 
-FX_BOOL CPDF_CustomAccess::ReadBlock(void* buffer,
-                                     FX_FILESIZE offset,
-                                     size_t size) {
+FX_BOOL CPDF_CustomAccess::IsEOF() {
+  return m_nCurPos >= static_cast<FX_FILESIZE>(m_FileAccess.m_FileLen);
+}
+
+size_t CPDF_CustomAccess::ReadBlock(void* buffer,
+                                    FX_FILESIZE offset,
+                                    size_t size) {
   if (offset < 0) {
-    return FALSE;
+    return 0;
   }
   FX_SAFE_FILESIZE newPos =
       pdfium::base::checked_cast<FX_FILESIZE, size_t>(size);
   newPos += offset;
   if (!newPos.IsValid() ||
       newPos.ValueOrDie() > static_cast<FX_FILESIZE>(m_FileAccess.m_FileLen)) {
-    return FALSE;
+    return 0;
   }
-  return m_FileAccess.m_GetBlock(m_FileAccess.m_Param, offset, (uint8_t*)buffer,
-                                 size);
+  m_FileAccess.m_GetBlock(m_FileAccess.m_Param, offset, (uint8_t*)buffer, size);
+  m_nCurPos = newPos.ValueOrDie();
+  return size;
 }
 
 // 0 bit: FPDF_POLICY_MACHINETIME_ACCESS
@@ -417,22 +423,25 @@ DLLEXPORT FPDF_BOOL STDCALL FPDF_LoadXFA(FPDF_DOCUMENT document) {
 
 class CMemFile final : public IFX_FileRead {
  public:
-  CMemFile(uint8_t* pBuf, FX_FILESIZE size) : m_pBuf(pBuf), m_size(size) {}
+  CMemFile(uint8_t* pBuf, FX_FILESIZE size)
+      : m_pBuf(pBuf), m_size(size), m_nCurPos(0) {}
 
   void Release() override { delete this; }
+  FX_BOOL IsEOF() override { return m_nCurPos >= m_size; }
   FX_FILESIZE GetSize() override { return m_size; }
-  FX_BOOL ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override {
+  size_t ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override {
     if (offset < 0) {
-      return FALSE;
+      return 0;
     }
     FX_SAFE_FILESIZE newPos =
         pdfium::base::checked_cast<FX_FILESIZE, size_t>(size);
     newPos += offset;
     if (!newPos.IsValid() || newPos.ValueOrDie() > m_size) {
-      return FALSE;
+      return 0;
     }
     FXSYS_memcpy(buffer, m_pBuf + offset, size);
-    return TRUE;
+    m_nCurPos = offset + size;
+    return size;
   }
 
  private:
@@ -440,6 +449,7 @@ class CMemFile final : public IFX_FileRead {
 
   uint8_t* const m_pBuf;
   const FX_FILESIZE m_size;
+  FX_FILESIZE m_nCurPos;
 };
 
 DLLEXPORT FPDF_DOCUMENT STDCALL FPDF_LoadMemDocument(const void* data_buf,