Revert HDFS-10543 patch due to correctness issues it caused. Done by James Clampffer

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/lib/fs/filehandle.cc

@@ -78,34 +78,26 @@ Status FileHandleImpl::PositionRead(void *buf, size_t *nbyte, off_t offset) {
   LOG_TRACE(kFileHandle, << "FileHandleImpl::[sync]PositionRead("
                          << FMT_THIS_ADDR << ", buf=" << buf
                          << ", nbyte=" << *nbyte << ") called");
-  size_t totalBytesRead = 0;
-  Status stat = Status::OK();
-  while (*nbyte != 0 && offset < (off_t)(file_info_->file_length_)) {
-    auto callstate = std::make_shared<std::promise<std::tuple<Status, size_t>>>();
-    std::future<std::tuple<Status, size_t>> future(callstate->get_future());
 
-    /* wrap async call with promise/future to make it blocking */
-    auto callback = [callstate](const Status &s, size_t bytes) {
-      callstate->set_value(std::make_tuple(s,bytes));
-    };
+  auto callstate = std::make_shared<std::promise<std::tuple<Status, size_t>>>();
+  std::future<std::tuple<Status, size_t>> future(callstate->get_future());
 
-    PositionRead(buf, *nbyte, offset, callback);
+  /* wrap async call with promise/future to make it blocking */
+  auto callback = [callstate](const Status &s, size_t bytes) {
+    callstate->set_value(std::make_tuple(s,bytes));
+  };
 
-    /* wait for async to finish */
-    auto returnstate = future.get();
-    stat = std::get<0>(returnstate);
+  PositionRead(buf, *nbyte, offset, callback);
 
-    if (!stat.ok()) {
-      return stat;
-    }
+  /* wait for async to finish */
+  auto returnstate = future.get();
+  auto stat = std::get<0>(returnstate);
 
-    size_t bytesRead = std::get<1>(returnstate);
-    *nbyte = *nbyte - bytesRead;
-    totalBytesRead += bytesRead;
-    offset += bytesRead;
+  if (!stat.ok()) {
+    return stat;
   }
-  /* Update the bytes read for return */
-  *nbyte = totalBytesRead;
+
+  *nbyte = std::get<1>(returnstate);
   return stat;
 }
 
@@ -118,8 +110,8 @@ Status FileHandleImpl::Read(void *buf, size_t *nbyte) {
   if(!stat.ok()) {
     return stat;
   }
-  offset_ += *nbyte;
 
+  offset_ += *nbyte;
   return Status::OK();
 }