Cross-platform APIs for working with files using direct I/O.
Depending on OS, this will use direct I/O, unbuffered, uncaches passthrough file reads/writes, bypassing as much of OS machinery as possible.
NOTE: There are major alignment requirements described here: https://learn.microsoft.com/en-us/windows/win32/fileio/file-buffering#alignment-and-file-access-requirements https://man7.org/linux/man-pages/man2/open.2.html