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

core/fxcodec/codec/fx_codec_tiff.cpp

Index: core/fxcodec/codec/fx_codec_tiff.cpp
diff --git a/core/fxcodec/codec/fx_codec_tiff.cpp b/core/fxcodec/codec/fx_codec_tiff.cpp
index 2a00bb2d2055f9d8f05292dc1d474f600cc405b6..4d9db8ba44571d8ce824dcb34c0c7ad8910eb581 100644
--- a/core/fxcodec/codec/fx_codec_tiff.cpp
+++ b/core/fxcodec/codec/fx_codec_tiff.cpp
@@ -90,11 +90,14 @@ namespace {
 
 tsize_t tiff_read(thandle_t context, tdata_t buf, tsize_t length) {
   CCodec_TiffContext* pTiffContext = (CCodec_TiffContext*)context;
-  if (!pTiffContext->io_in()->ReadBlock(buf, pTiffContext->offset(), length))
+  size_t readSize =
+      pTiffContext->io_in()->ReadBlock(buf, pTiffContext->offset(), length);
+  if (readSize != static_cast<size_t>(length) &&
+      !pTiffContext->io_in()->IsEOF())
     return 0;
 
-  pTiffContext->increment_offset(length);
-  return length;
+  pTiffContext->increment_offset(readSize);
+  return readSize;
 }
 
 tsize_t tiff_write(thandle_t context, tdata_t buf, tsize_t length) {