exposes a new  DB function that allows to retrieve all the
first-level entries of a specific directory.

In the case the open call has been called with the O_DIRECTORY flag the
ENOTSUP (Operation not supported) will be returned.

The path relativization code was not taking into a account corner cases
such as:
 - `/tmp/mountdir`
 - `/tmp/mountidr/`

Now that we use only relative path on daemon side,
also the initial creation of the root directory should be
use a relative path.

Acknowledge the main thread that the IO operation had terminate before
to actually close the file.

This is a "dirty" fix that waits to be refactored.

WARNING: Error on close will not be reported to the client that issued the IO
operation.

Data operation has been grouped under a ChunkStorage class
that will manage all the data backend operations.

The instance of this object is stored into the ADAFS_DATA sigleton.

The metadataDB class was using integer to return errors.
New exceptions classes has been introduced in order to be used as error
propagation method.

In this commit the MetadataDB::get function has been modified in order
to make use of exceptions.

During daemon setup, multiple spdloggers are configured.

Using spdlog::get("<LOGNAME>") is possible to retrieve those and use
them in other part of the code.

Paths are now made relative to the mountdir at client side.

The new relativize_path fucntion in the PreloadContext is used to check
if a path is relative to the pseudo-mount directory and to make it
relative

The new PreloadContext class is used as singleton to store the general context
information of the interception library.

The plan is to move global accessed variables into this sigleton.

At the moment just the logger object has been moved into it.

Metadata::serialize() was appending result instead of ovewriting it.

The new approach is to make serialize function return a new constructed
string instead of accepting a string reference to fill.

The rpc stat handler was the only one calling directly a db function,
bypassing the intermediate adafs_ops interface.

A new function on the adafs_ops interface has been added to be used by
the rpc stat handler.

Setting the properly the JMALLOC_LIBRARIES variable into the find module
made possible to avoid the conditonal inclusion of the library

Tommaso Tocci authored Apr 19, 2018 and Marc Vef committed Apr 27, 2018

The creation was performed through a simple rocksDB PUT operation.

Multiple creation attempts on the same file would override the
previously inserted metadata, in particular the file size.

The creation is now handled with a new MergeOperand.
Now a creation attampt on an already existing file will be converted in
a NOP.

Tommaso Tocci authored Apr 19, 2018 and Marc Vef committed Apr 27, 2018

The new MergeOperand base class can be subclassed in order to implement
new merge-operands with their specific parameters and semantics.