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 c4c745587f31fd7fa3b215f49e3a17f360000746..952fbdfae0ee1615d6e10f3e3b1a431d3ee9469c 100644
--- a/core/fxcodec/codec/fx_codec_tiff.cpp
+++ b/core/fxcodec/codec/fx_codec_tiff.cpp
@@ -98,11 +98,14 @@ tsize_t tiff_read(thandle_t context, tdata_t buf, tsize_t length) {
   if (!increment.IsValid())
     return 0;
 
-  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->set_offset(increment.ValueOrDie());
-  return length;
+  pTiffContext->set_offset(increment.ValueOrDie() - length + readSize);
+  return readSize;
 }
 
 tsize_t tiff_write(thandle_t context, tdata_t buf, tsize_t length) {