Efficient I/O with Memory-Mapped Files

Explain the performance benefits of memory-mapped I/O (`mmap`) over standard `read`/`write` calls for large datasets.

Implement file creation and pre-allocation to a specific size using `ftruncate` and POSIX file descriptors.

Map a pre-allocated file into the process's virtual address space using `mmap` for direct memory access.

Design a file layout for storing vector data and metadata contiguously for efficient access.

Implement functions to write vector data directly into the memory-mapped region.

Use `msync` to control the synchronization of in-memory changes to the underlying physical disk.