extern crate libc;
use std::env;
use std::ffi::CString;
use std::ptr;
use std::os::unix::ffi::OsStrExt;
const DEFAULT_PAGER_ENV: &'static str = "PAGER";
#[derive(Debug, Default)]
pub struct Pager {
env: String,
ok: bool,
}
impl Pager {
pub fn new() -> Self {
Pager {
env: String::from(DEFAULT_PAGER_ENV),
ok: true,
}
}
pub fn env(env: &str) -> Self {
Pager {
env: String::from(env),
ok: true,
}
}
pub fn ok(&self) -> bool {
self.ok
}
pub fn setup(&mut self) {
if let Some(pager) = getenv(&self.env) {
let (pager_stdin, main_stdout) = pipe();
let pid = fork();
match pid {
-1 => {
close(pager_stdin);
close(main_stdout);
self.ok = false
}
0 => {
dup2(main_stdout, libc::STDOUT_FILENO);
close(pager_stdin);
}
_ => {
let argv = vec![pager.as_ptr(), ptr::null()];
dup2(pager_stdin, libc::STDIN_FILENO);
close(main_stdout);
execvp(argv);
}
}
}
}
}
fn getenv(var: &str) -> Option<CString> {
if let Some(value) = env::var_os(var) {
let value = value.as_os_str().as_bytes();
let value = CString::new(value);
value.ok()
} else {
None
}
}
fn fork() -> libc::pid_t {
unsafe { libc::fork() }
}
fn execvp(argv: Vec<*const libc::c_char>) {
assert!(unsafe { libc::execvp(argv[0], argv.as_ptr()) } > -1);
}
fn dup2(fd1: i32, fd2: i32) {
assert!(unsafe { libc::dup2(fd1, fd2) } > -1);
}
fn close(fd: i32) {
assert_eq!(unsafe { libc::close(fd) }, 0);
}
fn pipe() -> (i32, i32) {
let mut fds = [0; 2];
assert_eq!(unsafe { libc::pipe(fds.as_mut_ptr()) }, 0);
(fds[0], fds[1])
}