openat_ct 0.2.0-pre9

use std::ffi::{CStr, CString, OsStr};
use std::io;
use std::fmt;
use std::mem;
use std::os::unix::ffi::OsStrExt;
use std::sync::Arc;

use crate::{dir::libc_ok, metadata, Metadata, SimpleType};

// We have such weird constants because C types are ugly
const DOT: [libc::c_char; 2] = [b'.' as libc::c_char, 0];
const DOTDOT: [libc::c_char; 3] = [b'.' as libc::c_char, b'.' as libc::c_char, 0];

/// Iterator over directory entries
///
/// Created using `Dir::list_dir()`
pub struct DirIter {
    // Needs Arc here to be shared with Entries, for metdata()
    dir: Arc<DirHandle>,
}

// It may not be thread-safe to call readdir concurrently from multiple threads on a single
// `DIR*`, but all `Send` requires is that we can call it from different threads
// non-concurrently - so this is fine.
//
// `man readdir` says:
//
// > It is expected that a future version of POSIX.1 will require that readdir() be
// > thread-safe when concurrently employed on different directory streams.
//
// so in the future we may also be able to implement `Sync`.
unsafe impl Send for DirIter {}

/// Position in a DirIter as obtained by 'DirIter::current_position()'
///
/// The position is only valid for the DirIter it was retrieved from.
pub struct DirPosition {
    pos: libc::c_long,
}

/// Entry returned by iterating over `DirIter` iterator
pub struct Entry {
    dir:             Arc<DirHandle>,
    pub(crate) name: CString,
    file_type:       Option<SimpleType>,
    ino:             libc::ino_t,
}

impl Entry {
    /// Returns the file name of this entry
    pub fn file_name(&self) -> &OsStr {
        OsStr::from_bytes(self.name.to_bytes())
    }

    /// Returns the simplified type of this entry
    pub fn simple_type(&self) -> Option<SimpleType> {
        self.file_type
    }

    /// Returns the inode number of this entry
    pub fn inode(&self) -> libc::ino_t {
        self.ino
    }

    /// Returns the metadata of this entry
    pub fn metadata(&self) -> io::Result<Metadata> {
        unsafe {
            let mut stat = mem::zeroed(); // TODO(cehteh): uninit
            libc_ok(libc::fstatat(
                libc::dirfd(self.dir.raw()),
                self.name.as_ptr(),
                &mut stat,
                libc::AT_SYMLINK_NOFOLLOW,
            ))?;
            Ok(metadata::new(stat))
        }
    }
}

impl fmt::Debug for Entry {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Entry")
            .field("dir", &Arc::as_ptr(&self.dir))
            .field("name", &self.name)
            .field("file_type", &self.file_type)
            .field("ino", &self.ino)
            .finish()
    }
}

#[cfg(any(target_os = "linux", target_os = "fuchsia"))]
unsafe fn errno_location() -> *mut libc::c_int {
    libc::__errno_location()
}

#[cfg(any(target_os = "openbsd", target_os = "netbsd", target_os = "android"))]
unsafe fn errno_location() -> *mut libc::c_int {
    libc::__errno()
}

#[cfg(not(any(
    target_os = "linux",
    target_os = "openbsd",
    target_os = "netbsd",
    target_os = "android",
    target_os = "fuchsia"
)))]
unsafe fn errno_location() -> *mut libc::c_int {
    libc::__error()
}

impl DirIter {
    unsafe fn next_entry(&mut self) -> io::Result<Option<&libc::dirent>> {
        // Reset errno to detect if error occurred
        *errno_location() = 0;

        let entry = libc::readdir(self.dir.raw());
        if entry.is_null() {
            if *errno_location() == 0 {
                return Ok(None);
            } else {
                return Err(io::Error::last_os_error());
            }
        }
        Ok(Some(&*entry))
    }

    /// Returns the current directory iterator position. The result should be handled as opaque value
    pub fn current_position(&self) -> io::Result<DirPosition> {
        let pos = unsafe { libc::telldir(self.dir.raw()) };

        if pos == -1 {
            Err(io::Error::last_os_error())
        } else {
            Ok(DirPosition { pos })
        }
    }

    // note the C-API does not report errors for seekdir/rewinddir, thus we don't do as well.
    /// Sets the current directory iterator position to some location queried by 'current_position()'
    pub fn seek(&self, position: DirPosition) {
        unsafe { libc::seekdir(self.dir.raw(), position.pos) };
    }

    /// Resets the current directory iterator position to the beginning
    pub fn rewind(&self) {
        unsafe { libc::rewinddir(self.dir.raw()) };
    }
}

pub fn open_dirfd(fd: libc::c_int) -> io::Result<DirIter> {
    let dir = unsafe { libc::fdopendir(fd) };
    if dir.is_null() {
        Err(io::Error::last_os_error())
    } else {
        Ok(DirIter {
            dir: Arc::new(DirHandle::new(dir)),
        })
    }
}

impl Iterator for DirIter {
    type Item = io::Result<Entry>;

    fn next(&mut self) -> Option<Self::Item> {
        unsafe {
            loop {
                let dir = Arc::clone(&self.dir);
                match self.next_entry() {
                    Err(e) => return Some(Err(e)),
                    Ok(None) => return None,
                    Ok(Some(e)) if e.d_name[..2] == DOT => continue,
                    Ok(Some(e)) if e.d_name[..3] == DOTDOT => continue,
                    Ok(Some(e)) => {
                        return Some(Ok(Entry {
                            dir,
                            name: CStr::from_ptr((e.d_name).as_ptr()).to_owned(),
                            file_type: match e.d_type {
                                0 => None,
                                libc::DT_REG => Some(SimpleType::File),
                                libc::DT_DIR => Some(SimpleType::Dir),
                                libc::DT_LNK => Some(SimpleType::Symlink),
                                _ => Some(SimpleType::Other),
                            },
                            ino: e.d_ino,
                        }));
                    }
                }
            }
        }
    }
}

//#[derive(Debug)]
struct DirHandle(*mut libc::DIR);

impl DirHandle {
    fn new(dir: *mut libc::DIR) -> Self {
        DirHandle(dir)
    }

    fn raw(&self) -> *mut libc::DIR {
        self.0
    }
}

impl Drop for DirHandle {
    fn drop(&mut self) {
        unsafe {
            libc::closedir(self.0);
        }
    }
}

#[cfg(test)]
mod test {
    use crate::Dir;

    #[test]
    fn test() {
        let d = Dir::open(".").unwrap();
        for e in d.list_self().unwrap() {
            if let Ok(e) = e {
                if let Ok(m) = e.metadata() {
                    eprintln!("{:?} : {:?}", e.file_name(), m);
                }
            }
        }
    }
}