Well managed file descriptor and mmap-ed memory

[primenumber]

Implement class for manage file descriptor / mmap-ed memory for dlk.

Motivation and Context

In current implementation, file descriptor and mmap-ed memory are not managed, so resource leakage occurs.
This PR fixes it.

Description

To manage file descriptor, FDManager
To manage mmap-ed memory, SimpleMappedMem

I considered to use std::unique_ptr:
Type of file descriptor is not pointer, so we have to implement custom class for store file descriptor which can be compare with std::nullptr_t.
munmap() require mapped size, so we have to implement custom class for store pointer with mapped size.
These increase implement cost.

How has this been tested?

$ PYTHONPATH=python/dlk python python/dlk/scripts/generate_project.py -i minimal_graph_with_shape.pb -o tmp/ -p object_detection -hq -ts -cache
$ cd tmp/object_detection.prj
$ mkdir build
$ cd build
$ cmake .. -DTOOLCHAIN_NAME=linux_arm -DUSE_NEON=1 -DRUN_ON_FPGA=1
$ make -j8 lm

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature / Optimization (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[tkng]

For me, this FDManager class represents file descriptor itself, rather than a manager. How about renaming this class to just FD or FileDescriptor or something?

If you are uncomfortable using such a common name, you can also use namespace.

[primenumber]

OK, fixed.

[tkng]

Since MappedMem class seems not be used in the current code, how about removing current MappedMem class and renaming this SimpleMappedMem class to MappedMem class?

[primenumber]

Fixed.

[tkng]

• readability approval
• ownership approval