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

core/fpdfapi/parser/cpdf_syntax_parser.cpp

Index: core/fpdfapi/parser/cpdf_syntax_parser.cpp
diff --git a/core/fpdfapi/parser/cpdf_syntax_parser.cpp b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
index 842ef2b22201143cbda709303041412adf3c8a30..e874d87e7f6c9d38b3135183c4e6140144e01c21 100644
--- a/core/fpdfapi/parser/cpdf_syntax_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
@@ -64,7 +64,8 @@ bool CPDF_SyntaxParser::ReadChar(FX_FILESIZE read_pos, uint32_t read_size) {
       read_pos = m_FileLen - read_size;
     }
   }
-  if (!m_pFileAccess->ReadBlock(m_pFileBuf, read_pos, read_size))
+  if (m_pFileAccess->ReadBlock(m_pFileBuf, read_pos, read_size) != read_size &&
+      !m_pFileAccess->IsEOF())
     return false;
 
   m_BufOffset = read_pos;
@@ -108,9 +109,11 @@ bool CPDF_SyntaxParser::GetCharAtBackward(FX_FILESIZE pos, uint8_t& ch) {
 }
 
 bool CPDF_SyntaxParser::ReadBlock(uint8_t* pBuf, uint32_t size) {
-  if (!m_pFileAccess->ReadBlock(pBuf, m_Pos + m_HeaderOffset, size))
+  uint32_t readSize =
+      m_pFileAccess->ReadBlock(pBuf, m_Pos + m_HeaderOffset, size);
+  if (readSize != size && !m_pFileAccess->IsEOF())
     return false;
-  m_Pos += size;
+  m_Pos += readSize;
   return true;
 }