diff --git a/src/preview.cpp b/src/preview.cpp

index 69f8e01..d20de04 100644

--- a/src/preview.cpp

+++ b/src/preview.cpp

@@ -37,6 +37,7 @@ EXIV2_RCSID("@(#) $Id$")

 #include "preview.hpp"

 #include "futils.hpp"

 #include "enforce.hpp"

+#include "safe_op.hpp"

 #include "image.hpp"

 #include "cr2image.hpp"

@@ -386,7 +387,7 @@ namespace {

             return AutoPtr();

         if (loaderList_[id].imageMimeType_ &&

-            std::string(loaderList_[id].imageMimeType_) != std::string(image.mimeType()))

+            std::string(loaderList_[id].imageMimeType_) != image.mimeType())

             return AutoPtr();

         AutoPtr loader = loaderList_[id].create_(id, image, loaderList_[id].parIdx_);

@@ -548,7 +549,8 @@ namespace {

             }

         }

-        if (offset_ + size_ > static_cast<uint32_t>(image_.io().size())) return;

+        if (Safe::add(offset_, size_) > static_cast<uint32_t>(image_.io().size()))

+            return;

         valid_ = true;

     }

@@ -802,7 +804,7 @@ namespace {

                     // this saves one copying of the buffer

                     uint32_t offset = dataValue.toLong(0);

                     uint32_t size = sizes.toLong(0);

-                    if (offset + size <= static_cast<uint32_t>(io.size()))

+                    if (Safe::add(offset, size) <= static_cast<uint32_t>(io.size()))

                         dataValue.setDataArea(base + offset, size);

                 }

                 else {

@@ -812,8 +814,8 @@ namespace {

                     for (int i = 0; i < sizes.count(); i++) {

                         uint32_t offset = dataValue.toLong(i);

                         uint32_t size = sizes.toLong(i);

-                        enforce(idxBuf + size < size_, kerCorruptedMetadata);

-                        if (size!=0 && offset + size <= static_cast<uint32_t>(io.size()))

+                        enforce(Safe::add(idxBuf, size) < size_, kerCorruptedMetadata);

+                        if (size!=0 && Safe::add(offset, size) <= static_cast<uint32_t>(io.size()))

                             memcpy(&buf.pData_[idxBuf], base + offset, size);

                         idxBuf += size;

                     }

@@ -930,7 +932,7 @@ namespace {

     DataBuf decodeBase64(const std::string& src)

     {

-        const unsigned long srcSize = static_cast<const unsigned long>(src.size());

+        const unsigned long srcSize = src.size();

         // create decoding table

         unsigned long invalid = 64;