// Copyright 2023 The ChromiumOS Authors

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file.

use std::os::unix::io::RawFd;

use libc::c_int;

use libc::fcntl;

use libc::F_GETFL;

use libc::F_SETFL;

use crate::errno::Result;

use crate::syscall;

/// Returns the file flags set for the given `RawFD`

///

/// Returns an error if the OS indicates the flags can't be retrieved.

fn get_fd_flags(fd: RawFd) -> Result<c_int> {

    syscall!(

        // SAFETY:

        // Safe because no third parameter is expected and we check the return result.

        unsafe { fcntl(fd, F_GETFL) }

    )

}

/// Sets the file flags set for the given `RawFD`.

///

/// Returns an error if the OS indicates the flags can't be retrieved.

fn set_fd_flags(fd: RawFd, flags: c_int) -> Result<()> {

    syscall!(

        // SAFETY:

        // Safe because we supply the third parameter and we check the return result.

        // fcntlt is trusted not to modify the memory of the calling process.

        unsafe { fcntl(fd, F_SETFL, flags) }

    )

    .map(|_| ())

}

/// Performs a logical OR of the given flags with the FD's flags, setting the given bits for the

/// FD.

///

/// Returns an error if the OS indicates the flags can't be retrieved or set.

pub fn add_fd_flags(fd: RawFd, set_flags: c_int) -> Result<()> {

    let start_flags = get_fd_flags(fd)?;

    set_fd_flags(fd, start_flags | set_flags)

}

/// Clears the given flags in the FD's flags.

///

/// Returns an error if the OS indicates the flags can't be retrieved or set.

pub fn clear_fd_flags(fd: RawFd, clear_flags: c_int) -> Result<()> {

    let start_flags = get_fd_flags(fd)?;

    set_fd_flags(fd, start_flags & !clear_flags)

}