Adapt to new fspp interface

Author: smessmer

src/CopyOpenFile.cpp

@@ -36,7 +36,7 @@ void CopyOpenFile::truncate(off_t size) const {
   CHECK_RETVAL(retval);
 }
 
-ssize_t CopyOpenFile::read(void *buf, size_t count, off_t offset) const {
+size_t CopyOpenFile::read(void *buf, size_t count, off_t offset) const {
   int retval = ::pread(_descriptor, buf, count, offset);
   CHECK_RETVAL(retval);
   ASSERT(static_cast<unsigned int>(retval) <= count, "Read wrong number of bytes");

src/CopyOpenFile.h

@@ -15,7 +15,7 @@ class CopyOpenFile final: public fspp::OpenFile {
 
   void stat(struct ::stat *result) const override;
   void truncate(off_t size) const override;
-  ssize_t read(void *buf, size_t count, off_t offset) const override;
+  size_t read(void *buf, size_t count, off_t offset) const override;
   void write(const void *buf, size_t count, off_t offset) override;
   void flush() override;
   void fsync() override;