joule-profiler-core 2.1.0

use std::ffi::{CStr, CString};

use crate::JouleProfilerError;

/// Sends a signal to a process.
///
/// SAFETY
///
/// - 'pid' must refer to a valid process identifier.
/// - Calling `libc::kill` is unsafe because it performs a raw syscall using the Linux FFI.
///
/// Race Condition
///
/// The target process may terminate before the
/// signal is made. In that case, the system call will fail and
/// an error will be returned and the signal name will
/// be retrieved for better error handling.
///
/// Errors
///
/// Returns [`JouleProfilerError::ProcessControlFailed`] if the
/// signal could not be delivered (e.g., invalid PID or already exited).
pub fn signal(pid: i32, sig: i32) -> Result<(), JouleProfilerError> {
    if unsafe { libc::kill(pid, sig) } != 0 {
        let sig_name = unsafe {
            let ptr = libc::strsignal(sig);
            if ptr.is_null() {
                "unknown signal".to_string()
            } else {
                CStr::from_ptr(ptr).to_string_lossy().to_string()
            }
        };
        Err(JouleProfilerError::ProcessControlFailed(format!(
            "Cannot send signal {sig_name} to process {pid}"
        )))
    } else {
        Ok(())
    }
}

/// Gets the effective user id of the current process.
///
/// SAFETY
///
/// - Calling `libc::geteuid` is unsafe because it performs a raw syscall using the Linux FFI.
pub fn geteuid() -> u32 {
    unsafe { libc::geteuid() }
}

/// True if the current user is root, else False.
pub fn is_root() -> bool {
    geteuid() == 0
}

/// Gets the current process' user id from its username.
///
/// SAFETY
///
/// - Calling `libc::getpwnam` is unsafe because it uses the Linux FFI.
pub fn get_uid_from_username(username: &str) -> Result<u32, JouleProfilerError> {
    let cname =
        CString::new(username).map_err(|_| JouleProfilerError::CannotRetrieveCurrentUserId)?;
    let passwd = unsafe { libc::getpwnam(cname.as_ptr()) };

    if passwd.is_null() {
        return Err(JouleProfilerError::CannotRetrieveCurrentUserId);
    }

    Ok(unsafe { (*passwd).pw_uid })
}