os.rs

// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/*!
 * Higher-level interfaces to libc::* functions and operating system services.
 *
 * In general these take and return rust types, use rust idioms (enums,
 * closures, vectors) rather than C idioms, and do more extensive safety
 * checks.
 *
 * This module is not meant to only contain 1:1 mappings to libc entries; any
 * os-interface code that is reasonably useful and broadly applicable can go
 * here. Including utility routines that merely build on other os code.
 *
 * We assume the general case is that users do not care, and do not want to
 * be made to care, which operating system they are on. While they may want
 * to special case various special cases -- and so we will not _hide_ the
 * facts of which OS the user is on -- they should be given the opportunity
 * to write OS-ignorant code by default.
 */

use cast;
use io;
use libc;
use libc::{c_char, c_void, c_int, size_t};
use libc::{mode_t, FILE};
use option;
use option::{Some, None};
use prelude::*;
use ptr;
use str;
use task;
use uint;
use unstable::finally::Finally;
use vec;

pub use libc::fclose;
pub use os::consts::*;

pub fn close(fd: c_int) -> c_int {
    unsafe {
        libc::close(fd)
    }
}

pub mod rustrt {
    use libc::{c_char, c_int};
    use libc;

    pub extern {
        unsafe fn rust_get_argc() -> c_int;
        unsafe fn rust_get_argv() -> **c_char;
        unsafe fn rust_path_is_dir(path: *libc::c_char) -> c_int;
        unsafe fn rust_path_exists(path: *libc::c_char) -> c_int;
        unsafe fn rust_set_exit_status(code: libc::intptr_t);
    }
}

pub static TMPBUF_SZ : uint = 1000u;
static BUF_BYTES : uint = 2048u;

pub fn getcwd() -> Path {
    let buf = [0 as libc::c_char, ..BUF_BYTES];
    unsafe {
        if(0 as *libc::c_char == libc::getcwd(
            &buf[0],
            BUF_BYTES as libc::size_t)) {
            fail!();
        }
        Path(str::raw::from_c_str(&buf[0]))
    }
}

// FIXME: move these to str perhaps? #2620

pub fn as_c_charp<T>(s: &str, f: &fn(*c_char) -> T) -> T {
    str::as_c_str(s, |b| f(b as *c_char))
}

pub fn fill_charp_buf(f: &fn(*mut c_char, size_t) -> bool)
    -> Option<~str> {
    let mut buf = vec::from_elem(TMPBUF_SZ, 0u8 as c_char);
    do vec::as_mut_buf(buf) |b, sz| {
        if f(b, sz as size_t) {
            unsafe {
                Some(str::raw::from_buf(b as *u8))
            }
        } else {
            None
        }
    }
}

#[cfg(windows)]
pub mod win32 {
    use libc;
    use vec;
    use str;
    use option::{None, Option};
    use option;
    use os::TMPBUF_SZ;
    use libc::types::os::arch::extra::DWORD;

    pub fn fill_utf16_buf_and_decode(f: &fn(*mut u16, DWORD) -> DWORD)
        -> Option<~str> {
        unsafe {
            let mut n = TMPBUF_SZ as DWORD;
            let mut res = None;
            let mut done = false;
            while !done {
                let mut k: DWORD = 0;
                let mut buf = vec::from_elem(n as uint, 0u16);
                do vec::as_mut_buf(buf) |b, _sz| {
                    k = f(b, TMPBUF_SZ as DWORD);
                    if k == (0 as DWORD) {
                        done = true;
                    } else if (k == n &&
                               libc::GetLastError() ==
                               libc::ERROR_INSUFFICIENT_BUFFER as DWORD) {
                        n *= (2 as DWORD);
                    } else {
                        done = true;
                    }
                }
                if k != 0 && done {
                    let sub = vec::slice(buf, 0u, k as uint);
                    res = option::Some(str::from_utf16(sub));
                }
            }
            return res;
        }
    }

    pub fn as_utf16_p<T>(s: &str, f: &fn(*u16) -> T) -> T {
        let mut t = str::to_utf16(s);
        // Null terminate before passing on.
        t += ~[0u16];
        vec::as_imm_buf(t, |buf, _len| f(buf))
    }
}

/*
Accessing environment variables is not generally threadsafe.
This uses a per-runtime lock to serialize access.
FIXME #4726: It would probably be appropriate to make this a real global
*/
fn with_env_lock<T>(f: &fn() -> T) -> T {
    use unstable::global::global_data_clone_create;
    use unstable::{Exclusive, exclusive};

    struct SharedValue(());
    type ValueMutex = Exclusive<SharedValue>;
    fn key(_: ValueMutex) { }

    unsafe {
        let lock: ValueMutex = global_data_clone_create(key, || {
            ~exclusive(SharedValue(()))
        });

        lock.with_imm(|_| f() )
    }
}

pub fn env() -> ~[(~str,~str)] {
    unsafe {
        #[cfg(windows)]
        unsafe fn get_env_pairs() -> ~[~str] {
            use libc::types::os::arch::extra::LPTCH;
            use libc::funcs::extra::kernel32::{
                GetEnvironmentStringsA,
                FreeEnvironmentStringsA
            };
            let ch = GetEnvironmentStringsA();
            if (ch as uint == 0) {
                fail!(fmt!("os::env() failure getting env string from OS: %s",
                           os::last_os_error()));
            }
            let mut curr_ptr: uint = ch as uint;
            let mut result = ~[];
            while(*(curr_ptr as *libc::c_char) != 0 as libc::c_char) {
                let env_pair = str::raw::from_c_str(
                    curr_ptr as *libc::c_char);
                result.push(env_pair);
                curr_ptr +=
                    libc::strlen(curr_ptr as *libc::c_char) as uint
                    + 1;
            }
            FreeEnvironmentStringsA(ch);
            result
        }
        #[cfg(unix)]
        unsafe fn get_env_pairs() -> ~[~str] {
            extern mod rustrt {
                unsafe fn rust_env_pairs() -> **libc::c_char;
            }
            let environ = rustrt::rust_env_pairs();
            if (environ as uint == 0) {
                fail!(fmt!("os::env() failure getting env string from OS: %s",
                           os::last_os_error()));
            }
            let mut result = ~[];
            ptr::array_each(environ, |e| {
                let env_pair = str::raw::from_c_str(e);
                debug!("get_env_pairs: %s",
                       env_pair);
                result.push(env_pair);
            });
            result
        }

        fn env_convert(input: ~[~str]) -> ~[(~str, ~str)] {
            let mut pairs = ~[];
            for input.each |p| {
                let mut vs = ~[];
                for str::each_splitn_char(*p, '=', 1) |s| { vs.push(s.to_owned()) }
                debug!("splitting: len: %u",
                    vs.len());
                assert!(vs.len() == 2);
                pairs.push((copy vs[0], copy vs[1]));
            }
            pairs
        }
        do with_env_lock {
            let unparsed_environ = get_env_pairs();
            env_convert(unparsed_environ)
        }
    }
}

#[cfg(unix)]
pub fn getenv(n: &str) -> Option<~str> {
    unsafe {
        do with_env_lock {
            let s = str::as_c_str(n, |s| libc::getenv(s));
            if ptr::null::<u8>() == cast::transmute(s) {
                option::None::<~str>
            } else {
                let s = cast::transmute(s);
                option::Some::<~str>(str::raw::from_buf(s))
            }
        }
    }
}

#[cfg(windows)]
pub fn getenv(n: &str) -> Option<~str> {
    unsafe {
        do with_env_lock {
            use os::win32::{as_utf16_p, fill_utf16_buf_and_decode};
            do as_utf16_p(n) |u| {
                do fill_utf16_buf_and_decode() |buf, sz| {
                    libc::GetEnvironmentVariableW(u, buf, sz)
                }
            }
        }
    }
}


#[cfg(unix)]
pub fn setenv(n: &str, v: &str) {
    unsafe {
        do with_env_lock {
            do str::as_c_str(n) |nbuf| {
                do str::as_c_str(v) |vbuf| {
                    libc::funcs::posix01::unistd::setenv(nbuf, vbuf, 1);
                }
            }
        }
    }
}


#[cfg(windows)]
pub fn setenv(n: &str, v: &str) {
    unsafe {
        do with_env_lock {
            use os::win32::as_utf16_p;
            do as_utf16_p(n) |nbuf| {
                do as_utf16_p(v) |vbuf| {
                    libc::SetEnvironmentVariableW(nbuf, vbuf);
                }
            }
        }
    }
}

pub fn fdopen(fd: c_int) -> *FILE {
    unsafe {
        return do as_c_charp("r") |modebuf| {
            libc::fdopen(fd, modebuf)
        };
    }
}


// fsync related

#[cfg(windows)]
pub fn fsync_fd(fd: c_int, _level: io::fsync::Level) -> c_int {
    unsafe {
        use libc::funcs::extra::msvcrt::*;
        return commit(fd);
    }
}

#[cfg(target_os = "linux")]
#[cfg(target_os = "android")]
pub fn fsync_fd(fd: c_int, level: io::fsync::Level) -> c_int {
    unsafe {
        use libc::funcs::posix01::unistd::*;
        match level {
          io::fsync::FSync
          | io::fsync::FullFSync => return fsync(fd),
          io::fsync::FDataSync => return fdatasync(fd)
        }
    }
}

#[cfg(target_os = "macos")]
pub fn fsync_fd(fd: c_int, level: io::fsync::Level) -> c_int {
    unsafe {
        use libc::consts::os::extra::*;
        use libc::funcs::posix88::fcntl::*;
        use libc::funcs::posix01::unistd::*;
        match level {
          io::fsync::FSync => return fsync(fd),
          _ => {
            // According to man fnctl, the ok retval is only specified to be
            // !=-1
            if (fcntl(F_FULLFSYNC as c_int, fd) == -1 as c_int)
                { return -1 as c_int; }
            else
                { return 0 as c_int; }
          }
        }
    }
}

#[cfg(target_os = "freebsd")]
pub fn fsync_fd(fd: c_int, _l: io::fsync::Level) -> c_int {
    unsafe {
        use libc::funcs::posix01::unistd::*;
        return fsync(fd);
    }
}

pub struct Pipe { mut in: c_int, mut out: c_int }

#[cfg(unix)]
pub fn pipe() -> Pipe {
    unsafe {
        let mut fds = Pipe {in: 0 as c_int,
                        out: 0 as c_int };
        assert!((libc::pipe(&mut fds.in) == (0 as c_int)));
        return Pipe {in: fds.in, out: fds.out};
    }
}



#[cfg(windows)]
pub fn pipe() -> Pipe {
    unsafe {
        // Windows pipes work subtly differently than unix pipes, and their
        // inheritance has to be handled in a different way that I do not
        // fully understand. Here we explicitly make the pipe non-inheritable,
        // which means to pass it to a subprocess they need to be duplicated
        // first, as in core::run.
        let mut fds = Pipe {in: 0 as c_int,
                    out: 0 as c_int };
        let res = libc::pipe(&mut fds.in, 1024 as ::libc::c_uint,
                             (libc::O_BINARY | libc::O_NOINHERIT) as c_int);
        assert!((res == 0 as c_int));
        assert!((fds.in != -1 as c_int && fds.in != 0 as c_int));
        assert!((fds.out != -1 as c_int && fds.in != 0 as c_int));
        return Pipe {in: fds.in, out: fds.out};
    }
}

fn dup2(src: c_int, dst: c_int) -> c_int {
    unsafe {
        libc::dup2(src, dst)
    }
}


pub fn dll_filename(base: &str) -> ~str {
    return str::from_slice(DLL_PREFIX) + str::from_slice(base) +
           str::from_slice(DLL_SUFFIX)
}


pub fn self_exe_path() -> Option<Path> {

    #[cfg(target_os = "freebsd")]
    fn load_self() -> Option<~str> {
        unsafe {
            use libc::funcs::bsd44::*;
            use libc::consts::os::extra::*;
            do fill_charp_buf() |buf, sz| {
                let mib = ~[CTL_KERN as c_int,
                           KERN_PROC as c_int,
                           KERN_PROC_PATHNAME as c_int, -1 as c_int];
                let mut sz = sz;
                sysctl(vec::raw::to_ptr(mib), vec::len(mib) as ::libc::c_uint,
                       buf as *mut c_void, &mut sz, ptr::null(),
                       0u as size_t) == (0 as c_int)
            }
        }
    }

    #[cfg(target_os = "linux")]
    #[cfg(target_os = "android")]
    fn load_self() -> Option<~str> {
        unsafe {
            use libc::funcs::posix01::unistd::readlink;

            let mut path_str = str::with_capacity(TMPBUF_SZ);
            let len = do str::as_c_str(path_str) |buf| {
                let buf = buf as *mut c_char;
                do as_c_charp("/proc/self/exe") |proc_self_buf| {
                    readlink(proc_self_buf, buf, TMPBUF_SZ as size_t)
                }
            };
            if len == -1 {
                None
            } else {
                str::raw::set_len(&mut path_str, len as uint);
                Some(path_str)
            }
        }
    }

    #[cfg(target_os = "macos")]
    fn load_self() -> Option<~str> {
        unsafe {
            do fill_charp_buf() |buf, sz| {
                let mut sz = sz as u32;
                libc::funcs::extra::_NSGetExecutablePath(
                    buf, &mut sz) == (0 as c_int)
            }
        }
    }

    #[cfg(windows)]
    fn load_self() -> Option<~str> {
        unsafe {
            use os::win32::fill_utf16_buf_and_decode;
            do fill_utf16_buf_and_decode() |buf, sz| {
                libc::GetModuleFileNameW(0u as libc::DWORD, buf, sz)
            }
        }
    }

    do load_self().map |pth| {
        Path(*pth).dir_path()
    }
}


/**
 * Returns the path to the user's home directory, if known.
 *
 * On Unix, returns the value of the 'HOME' environment variable if it is set
 * and not equal to the empty string.
 *
 * On Windows, returns the value of the 'HOME' environment variable if it is
 * set and not equal to the empty string. Otherwise, returns the value of the
 * 'USERPROFILE' environment variable if it is set and not equal to the empty
 * string.
 *
 * Otherwise, homedir returns option::none.
 */
pub fn homedir() -> Option<Path> {
    return match getenv(~"HOME") {
        Some(ref p) => if !str::is_empty(*p) {
          Some(Path(*p))
        } else {
          secondary()
        },
        None => secondary()
    };

    #[cfg(unix)]
    fn secondary() -> Option<Path> {
        None
    }

    #[cfg(windows)]
    fn secondary() -> Option<Path> {
        do getenv(~"USERPROFILE").chain |p| {
            if !str::is_empty(p) {
                Some(Path(p))
            } else {
                None
            }
        }
    }
}

/**
 * Returns the path to a temporary directory.
 *
 * On Unix, returns the value of the 'TMPDIR' environment variable if it is
 * set and non-empty and '/tmp' otherwise.
 *
 * On Windows, returns the value of, in order, the 'TMP', 'TEMP',
 * 'USERPROFILE' environment variable  if any are set and not the empty
 * string. Otherwise, tmpdir returns the path to the Windows directory.
 */
pub fn tmpdir() -> Path {
    return lookup();

    fn getenv_nonempty(v: &str) -> Option<Path> {
        match getenv(v) {
            Some(x) =>
                if str::is_empty(x) {
                    None
                } else {
                    Some(Path(x))
                },
            _ => None
        }
    }

    #[cfg(unix)]
    #[allow(non_implicitly_copyable_typarams)]
    fn lookup() -> Path {
        getenv_nonempty("TMPDIR").get_or_default(Path("/tmp"))
    }

    #[cfg(windows)]
    #[allow(non_implicitly_copyable_typarams)]
    fn lookup() -> Path {
        getenv_nonempty("TMP").or(
            getenv_nonempty("TEMP").or(
                getenv_nonempty("USERPROFILE").or(
                   getenv_nonempty("WINDIR")))).get_or_default(Path("C:\\Windows"))
    }
}
/// Recursively walk a directory structure
pub fn walk_dir(p: &Path, f: &fn(&Path) -> bool) {

    walk_dir_(p, f);

    fn walk_dir_(p: &Path, f: &fn(&Path) -> bool) -> bool {
        let mut keepgoing = true;
        do list_dir(p).each |q| {
            let path = &p.push(*q);
            if !f(path) {
                keepgoing = false;
                false
            } else {
                if path_is_dir(path) {
                    if !walk_dir_(path, f) {
                        keepgoing = false;
                        false
                    } else {
                        true
                    }
                } else {
                    true
                }
            }
        }
        return keepgoing;
    }
}

/// Indicates whether a path represents a directory
pub fn path_is_dir(p: &Path) -> bool {
    unsafe {
        do str::as_c_str(p.to_str()) |buf| {
            rustrt::rust_path_is_dir(buf) != 0 as c_int
        }
    }
}

/// Indicates whether a path exists
pub fn path_exists(p: &Path) -> bool {
    unsafe {
        do str::as_c_str(p.to_str()) |buf| {
            rustrt::rust_path_exists(buf) != 0 as c_int
        }
    }
}

/**
 * Convert a relative path to an absolute path
 *
 * If the given path is relative, return it prepended with the current working
 * directory. If the given path is already an absolute path, return it
 * as is.
 */
// NB: this is here rather than in path because it is a form of environment
// querying; what it does depends on the process working directory, not just
// the input paths.
pub fn make_absolute(p: &Path) -> Path {
    if p.is_absolute {
        copy *p
    } else {
        getcwd().push_many(p.components)
    }
}


/// Creates a directory at the specified path
pub fn make_dir(p: &Path, mode: c_int) -> bool {
    return mkdir(p, mode);

    #[cfg(windows)]
    fn mkdir(p: &Path, _mode: c_int) -> bool {
        unsafe {
            use os::win32::as_utf16_p;
            // FIXME: turn mode into something useful? #2623
            do as_utf16_p(p.to_str()) |buf| {
                libc::CreateDirectoryW(buf, unsafe {
                    cast::transmute(0)
                })
                    != (0 as libc::BOOL)
            }
        }
    }

    #[cfg(unix)]
    fn mkdir(p: &Path, mode: c_int) -> bool {
        unsafe {
            do as_c_charp(p.to_str()) |c| {
                libc::mkdir(c, mode as mode_t) == (0 as c_int)
            }
        }
    }
}

/// Creates a directory with a given mode.
/// Returns true iff creation
/// succeeded. Also creates all intermediate subdirectories
/// if they don't already exist, giving all of them the same mode.

// tjc: if directory exists but with different permissions,
// should we return false?
pub fn mkdir_recursive(p: &Path, mode: c_int) -> bool {
    if path_is_dir(p) {
        return true;
    }
    else if p.components.is_empty() {
        return false;
    }
    else if p.components.len() == 1 {
        // No parent directories to create
        path_is_dir(p) || make_dir(p, mode)
    }
    else {
        mkdir_recursive(&p.pop(), mode) && make_dir(p, mode)
    }
}

/// Lists the contents of a directory
#[allow(non_implicitly_copyable_typarams)]
pub fn list_dir(p: &Path) -> ~[~str] {
    unsafe {
        #[cfg(target_os = "linux")]
        #[cfg(target_os = "android")]
        #[cfg(target_os = "freebsd")]
        #[cfg(target_os = "macos")]
        unsafe fn get_list(p: &Path) -> ~[~str] {
            use libc::{dirent_t};
            use libc::{opendir, readdir, closedir};
            extern mod rustrt {
                unsafe fn rust_list_dir_val(ptr: *dirent_t)
                    -> *libc::c_char;
            }
            let input = p.to_str();
            let mut strings = ~[];
            let input_ptr = ::cast::transmute(&input[0]);
            debug!("os::list_dir -- BEFORE OPENDIR");
            let dir_ptr = opendir(input_ptr);
            if (dir_ptr as uint != 0) {
        debug!("os::list_dir -- opendir() SUCCESS");
                let mut entry_ptr = readdir(dir_ptr);
                while (entry_ptr as uint != 0) {
                    strings.push(
                        str::raw::from_c_str(
                            rustrt::rust_list_dir_val(
                                entry_ptr)));
                    entry_ptr = readdir(dir_ptr);
                }
                closedir(dir_ptr);
            }
            else {
        debug!("os::list_dir -- opendir() FAILURE");
            }
            debug!(
                "os::list_dir -- AFTER -- #: %?",
                     strings.len());
            strings
        }
        #[cfg(windows)]
        unsafe fn get_list(p: &Path) -> ~[~str] {
            use libc::types::os::arch::extra::{LPCTSTR, HANDLE, BOOL};
            use libc::consts::os::extra::INVALID_HANDLE_VALUE;
            use libc::wcslen;
            use libc::funcs::extra::kernel32::{
                FindFirstFileW,
                FindNextFileW,
                FindClose,
            };
            use os::win32::{
                as_utf16_p
            };
            use unstable::exchange_alloc::{malloc_raw, free_raw};
            #[nolink]
            extern mod rustrt {
                unsafe fn rust_list_dir_wfd_size() -> libc::size_t;
                unsafe fn rust_list_dir_wfd_fp_buf(wfd: *libc::c_void)
                    -> *u16;
            }
            fn star(p: &Path) -> Path { p.push("*") }
            do as_utf16_p(star(p).to_str()) |path_ptr| {
                let mut strings = ~[];
                let wfd_ptr = malloc_raw(
                    rustrt::rust_list_dir_wfd_size() as uint);
                let find_handle =
                    FindFirstFileW(
                        path_ptr,
                        ::cast::transmute(wfd_ptr));
                if find_handle as int != INVALID_HANDLE_VALUE {
                    let mut more_files = 1 as libc::c_int;
                    while more_files != 0 {
                        let fp_buf = rustrt::rust_list_dir_wfd_fp_buf(
                            wfd_ptr);
                        if fp_buf as uint == 0 {
                            fail!(~"os::list_dir() failure:"+
                                  ~" got null ptr from wfd");
                        }
                        else {
                            let fp_vec = vec::from_buf(
                                fp_buf, wcslen(fp_buf) as uint);
                            let fp_str = str::from_utf16(fp_vec);
                            strings.push(fp_str);
                        }
                        more_files = FindNextFileW(
                            find_handle,
                            ::cast::transmute(wfd_ptr));
                    }
                    FindClose(find_handle);
                    free_raw(wfd_ptr);
                }
                strings
            }
        }
        do get_list(p).filtered |filename| {
            *filename != ~"." && *filename != ~".."
        }
    }
}

/**
 * Lists the contents of a directory
 *
 * This version prepends each entry with the directory.
 */
pub fn list_dir_path(p: &Path) -> ~[~Path] {
    list_dir(p).map(|f| ~p.push(*f))
}

/// Removes a directory at the specified path
pub fn remove_dir(p: &Path) -> bool {
   return rmdir(p);

    #[cfg(windows)]
    fn rmdir(p: &Path) -> bool {
        unsafe {
            use os::win32::as_utf16_p;
            return do as_utf16_p(p.to_str()) |buf| {
                libc::RemoveDirectoryW(buf) != (0 as libc::BOOL)
            };
        }
    }

    #[cfg(unix)]
    fn rmdir(p: &Path) -> bool {
        unsafe {
            return do as_c_charp(p.to_str()) |buf| {
                libc::rmdir(buf) == (0 as c_int)
            };
        }
    }
}

pub fn change_dir(p: &Path) -> bool {
    return chdir(p);

    #[cfg(windows)]
    fn chdir(p: &Path) -> bool {
        unsafe {
            use os::win32::as_utf16_p;
            return do as_utf16_p(p.to_str()) |buf| {
                libc::SetCurrentDirectoryW(buf) != (0 as libc::BOOL)
            };
        }
    }

    #[cfg(unix)]
    fn chdir(p: &Path) -> bool {
        unsafe {
            return do as_c_charp(p.to_str()) |buf| {
                libc::chdir(buf) == (0 as c_int)
            };
        }
    }
}

/// Changes the current working directory to the specified
/// path while acquiring a global lock, then calls `action`.
/// If the change is successful, releases the lock and restores the
/// CWD to what it was before, returning true.
/// Returns false if the directory doesn't exist or if the directory change
/// is otherwise unsuccessful.
pub fn change_dir_locked(p: &Path, action: &fn()) -> bool {
    use unstable::global::global_data_clone_create;
    use unstable::{Exclusive, exclusive};

    fn key(_: Exclusive<()>) { }

    let result = unsafe {
        global_data_clone_create(key, || {
            ~exclusive(())
        })
    };

    do result.with_imm() |_| {
        let old_dir = os::getcwd();
        if change_dir(p) {
            action();
            change_dir(&old_dir)
        }
        else {
            false
        }
    }
}

/// Copies a file from one location to another
pub fn copy_file(from: &Path, to: &Path) -> bool {
    return do_copy_file(from, to);

    #[cfg(windows)]
    fn do_copy_file(from: &Path, to: &Path) -> bool {
        unsafe {
            use os::win32::as_utf16_p;
            return do as_utf16_p(from.to_str()) |fromp| {
                do as_utf16_p(to.to_str()) |top| {
                    libc::CopyFileW(fromp, top, (0 as libc::BOOL)) !=
                        (0 as libc::BOOL)
                }
            }
        }
    }

    #[cfg(unix)]
    fn do_copy_file(from: &Path, to: &Path) -> bool {
        unsafe {
            let istream = do as_c_charp(from.to_str()) |fromp| {
                do as_c_charp("rb") |modebuf| {
                    libc::fopen(fromp, modebuf)
                }
            };
            if istream as uint == 0u {
                return false;
            }
            let ostream = do as_c_charp(to.to_str()) |top| {
                do as_c_charp("w+b") |modebuf| {
                    libc::fopen(top, modebuf)
                }
            };
            if ostream as uint == 0u {
                fclose(istream);
                return false;
            }
            let bufsize = 8192u;
            let mut buf = vec::with_capacity::<u8>(bufsize);
            let mut done = false;
            let mut ok = true;
            while !done {
                do vec::as_mut_buf(buf) |b, _sz| {
                  let nread = libc::fread(b as *mut c_void, 1u as size_t,
                                          bufsize as size_t,
                                          istream);
                  if nread > 0 as size_t {
                      if libc::fwrite(b as *c_void, 1u as size_t, nread,
                                      ostream) != nread {
                          ok = false;
                          done = true;
                      }
                  } else {
                      done = true;
                  }
              }
            }
            fclose(istream);
            fclose(ostream);
            return ok;
        }
    }
}

/// Deletes an existing file
pub fn remove_file(p: &Path) -> bool {
    return unlink(p);

    #[cfg(windows)]
    fn unlink(p: &Path) -> bool {
        unsafe {
            use os::win32::as_utf16_p;
            return do as_utf16_p(p.to_str()) |buf| {
                libc::DeleteFileW(buf) != (0 as libc::BOOL)
            };
        }
    }

    #[cfg(unix)]
    fn unlink(p: &Path) -> bool {
        unsafe {
            return do as_c_charp(p.to_str()) |buf| {
                libc::unlink(buf) == (0 as c_int)
            };
        }
    }
}

#[cfg(unix)]
pub fn errno() -> int {
    #[cfg(target_os = "macos")]
    #[cfg(target_os = "freebsd")]
    fn errno_location() -> *c_int {
        #[nolink]
        extern {
            unsafe fn __error() -> *c_int;
        }
        unsafe {
            __error()
        }
    }

    #[cfg(target_os = "linux")]
    #[cfg(target_os = "android")]
    fn errno_location() -> *c_int {
        #[nolink]
        extern {
            unsafe fn __errno_location() -> *c_int;
        }
        unsafe {
            __errno_location()
        }
    }

    unsafe {
        (*errno_location()) as int
    }
}

#[cfg(windows)]
pub fn errno() -> uint {
    use libc::types::os::arch::extra::DWORD;

    #[link_name = "kernel32"]
    #[abi = "stdcall"]
    extern "stdcall" {
        unsafe fn GetLastError() -> DWORD;
    }

    unsafe {
        GetLastError() as uint
    }
}

/// Get a string representing the platform-dependent last error
pub fn last_os_error() -> ~str {
    #[cfg(unix)]
    fn strerror() -> ~str {
        #[cfg(target_os = "macos")]
        #[cfg(target_os = "android")]
        #[cfg(target_os = "freebsd")]
        fn strerror_r(errnum: c_int, buf: *c_char, buflen: size_t) -> c_int {
            #[nolink]
            extern {
                unsafe fn strerror_r(errnum: c_int, buf: *c_char,
                                     buflen: size_t) -> c_int;
            }
            unsafe {
                strerror_r(errnum, buf, buflen)
            }
        }

        // GNU libc provides a non-compliant version of strerror_r by default
        // and requires macros to instead use the POSIX compliant variant.
        // So we just use __xpg_strerror_r which is always POSIX compliant
        #[cfg(target_os = "linux")]
        fn strerror_r(errnum: c_int, buf: *c_char, buflen: size_t) -> c_int {
            #[nolink]
            extern {
                unsafe fn __xpg_strerror_r(errnum: c_int, buf: *c_char,
                                           buflen: size_t) -> c_int;
            }
            unsafe {
                __xpg_strerror_r(errnum, buf, buflen)
            }
        }

        let mut buf = [0 as c_char, ..TMPBUF_SZ];
        unsafe {
            let err = strerror_r(errno() as c_int, &buf[0],
                                 TMPBUF_SZ as size_t);
            if err < 0 {
                fail!(~"strerror_r failure");
            }

            str::raw::from_c_str(&buf[0])
        }
    }

    #[cfg(windows)]
    fn strerror() -> ~str {
        use libc::types::os::arch::extra::DWORD;
        use libc::types::os::arch::extra::LPSTR;
        use libc::types::os::arch::extra::LPVOID;

        #[link_name = "kernel32"]
        #[abi = "stdcall"]
        extern "stdcall" {
            unsafe fn FormatMessageA(flags: DWORD, lpSrc: LPVOID,
                                     msgId: DWORD, langId: DWORD,
                                     buf: LPSTR, nsize: DWORD,
                                     args: *c_void) -> DWORD;
        }

        static FORMAT_MESSAGE_FROM_SYSTEM: DWORD = 0x00001000;
        static FORMAT_MESSAGE_IGNORE_INSERTS: DWORD = 0x00000200;

        let mut buf = [0 as c_char, ..TMPBUF_SZ];

        // This value is calculated from the macro
        // MAKELANGID(LANG_SYSTEM_DEFAULT, SUBLANG_SYS_DEFAULT)
        let langId = 0x0800 as DWORD;
        let err = errno() as DWORD;
        unsafe {
            let res = FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM |
                                     FORMAT_MESSAGE_IGNORE_INSERTS,
                                     ptr::mut_null(), err, langId,
                                     &mut buf[0], TMPBUF_SZ as DWORD,
                                     ptr::null());
            if res == 0 {
                fail!(fmt!("[%?] FormatMessage failure", errno()));
            }

            str::raw::from_c_str(&buf[0])
        }
    }

    strerror()
}

/**
 * Sets the process exit code
 *
 * Sets the exit code returned by the process if all supervised tasks
 * terminate successfully (without failing). If the current root task fails
 * and is supervised by the scheduler then any user-specified exit status is
 * ignored and the process exits with the default failure status
 */
pub fn set_exit_status(code: int) {
    unsafe {
        rustrt::rust_set_exit_status(code as libc::intptr_t);
    }
}

unsafe fn load_argc_and_argv(argc: c_int, argv: **c_char) -> ~[~str] {
    let mut args = ~[];
    for uint::range(0, argc as uint) |i| {
        vec::push(&mut args, str::raw::from_c_str(*argv.offset(i)));
    }
    args
}

/**
 * Returns the command line arguments
 *
 * Returns a list of the command line arguments.
 */
#[cfg(target_os = "macos")]
pub fn real_args() -> ~[~str] {
    unsafe {
        let (argc, argv) = (*_NSGetArgc() as c_int,
                            *_NSGetArgv() as **c_char);
        load_argc_and_argv(argc, argv)
    }
}

#[cfg(target_os = "linux")]
#[cfg(target_os = "android")]
#[cfg(target_os = "freebsd")]
pub fn real_args() -> ~[~str] {
    unsafe {
        let argc = rustrt::rust_get_argc();
        let argv = rustrt::rust_get_argv();
        load_argc_and_argv(argc, argv)
    }
}

#[cfg(windows)]
pub fn real_args() -> ~[~str] {
    let mut nArgs: c_int = 0;
    let lpArgCount = ptr::to_mut_unsafe_ptr(&mut nArgs);
    let lpCmdLine = unsafe { GetCommandLineW() };
    let szArgList = unsafe { CommandLineToArgvW(lpCmdLine, lpArgCount) };

    let mut args = ~[];
    for uint::range(0, nArgs as uint) |i| {
        unsafe {
            // Determine the length of this argument.
            let ptr = *szArgList.offset(i);
            let mut len = 0;
            while *ptr.offset(len) != 0 { len += 1; }

            // Push it onto the list.
            vec::push(&mut args,
                      vec::raw::buf_as_slice(ptr, len,
                                             str::from_utf16));
        }
    }

    unsafe {
        LocalFree(cast::transmute(szArgList));
    }

    return args;
}

type LPCWSTR = *u16;

#[cfg(windows)]
#[link_name="kernel32"]
#[abi="stdcall"]
extern "stdcall" {
    fn GetCommandLineW() -> LPCWSTR;
    fn LocalFree(ptr: *c_void);
}

#[cfg(windows)]
#[link_name="shell32"]
#[abi="stdcall"]
extern "stdcall" {
    fn CommandLineToArgvW(lpCmdLine: LPCWSTR, pNumArgs: *mut c_int) -> **u16;
}

struct OverriddenArgs {
    val: ~[~str]
}

fn overridden_arg_key(_v: @OverriddenArgs) {}

pub fn args() -> ~[~str] {
    unsafe {
        match task::local_data::local_data_get(overridden_arg_key) {
            None => real_args(),
            Some(args) => copy args.val
        }
    }
}

pub fn set_args(new_args: ~[~str]) {
    unsafe {
        let overridden_args = @OverriddenArgs { val: copy new_args };
        task::local_data::local_data_set(overridden_arg_key, overridden_args);
    }
}

// FIXME #6100 we should really use an internal implementation of this - using
// the POSIX glob functions isn't portable to windows, probably has slight
// inconsistencies even where it is implemented, and makes extending
// functionality a lot more difficult
// FIXME #6101 also provide a non-allocating version - each_glob or so?
/// Returns a vector of Path objects that match the given glob pattern
#[cfg(target_os = "linux")]
#[cfg(target_os = "android")]
#[cfg(target_os = "freebsd")]
#[cfg(target_os = "macos")]
pub fn glob(pattern: &str) -> ~[Path] {
    #[cfg(target_os = "linux")]
    #[cfg(target_os = "android")]
    fn default_glob_t () -> libc::glob_t {
        libc::glob_t {
            gl_pathc: 0,
            gl_pathv: ptr::null(),
            gl_offs: 0,
            __unused1: ptr::null(),
            __unused2: ptr::null(),
            __unused3: ptr::null(),
            __unused4: ptr::null(),
            __unused5: ptr::null(),
        }
    }

    #[cfg(target_os = "freebsd")]
    fn default_glob_t () -> libc::glob_t {
        libc::glob_t {
            gl_pathc: 0,
            __unused1: 0,
            gl_offs: 0,
            __unused2: 0,
            gl_pathv: ptr::null(),
            __unused3: ptr::null(),
            __unused4: ptr::null(),
            __unused5: ptr::null(),
            __unused6: ptr::null(),
            __unused7: ptr::null(),
            __unused8: ptr::null(),
        }
    }

    #[cfg(target_os = "macos")]
    fn default_glob_t () -> libc::glob_t {
        libc::glob_t {
            gl_pathc: 0,
            __unused1: 0,
            gl_offs: 0,
            __unused2: 0,
            gl_pathv: ptr::null(),
            __unused3: ptr::null(),
            __unused4: ptr::null(),
            __unused5: ptr::null(),
            __unused6: ptr::null(),
            __unused7: ptr::null(),
            __unused8: ptr::null(),
        }
    }

    let mut g = default_glob_t();
    do str::as_c_str(pattern) |c_pattern| {
        unsafe { libc::glob(c_pattern, 0, ptr::null(), &mut g) }
    };
    do(|| {
        let paths = unsafe {
            vec::raw::from_buf_raw(g.gl_pathv, g.gl_pathc as uint)
        };
        do paths.map |&c_str| {
            Path(unsafe { str::raw::from_c_str(c_str) })
        }
    }).finally {
        unsafe { libc::globfree(&mut g) };
    }
}

/// Returns a vector of Path objects that match the given glob pattern
#[cfg(target_os = "win32")]
pub fn glob(pattern: &str) -> ~[Path] {
    fail!(~"glob() is unimplemented on Windows")
}

#[cfg(target_os = "macos")]
extern {
    // These functions are in crt_externs.h.
    pub fn _NSGetArgc() -> *c_int;
    pub fn _NSGetArgv() -> ***c_char;
}

pub mod consts {

    #[cfg(unix)]
    pub use os::consts::unix::*;

    #[cfg(windows)]
    pub use os::consts::windows::*;

    #[cfg(target_os = "macos")]
    pub use os::consts::macos::*;

    #[cfg(target_os = "freebsd")]
    pub use os::consts::freebsd::*;

    #[cfg(target_os = "linux")]
    pub use os::consts::linux::*;

    #[cfg(target_os = "android")]
    pub use os::consts::android::*;

    #[cfg(target_os = "win32")]
    pub use os::consts::win32::*;

    #[cfg(target_arch = "x86")]
    pub use os::consts::x86::*;

    #[cfg(target_arch = "x86_64")]
    pub use os::consts::x86_64::*;

    #[cfg(target_arch = "arm")]
    pub use os::consts::arm::*;

    #[cfg(target_arch = "mips")]
    use os::consts::mips::*;

    pub mod unix {
        pub static FAMILY: &'static str = "unix";
    }

    pub mod windows {
        pub static FAMILY: &'static str = "windows";
    }

    pub mod macos {
        pub static SYSNAME: &'static str = "macos";
        pub static DLL_PREFIX: &'static str = "lib";
        pub static DLL_SUFFIX: &'static str = ".dylib";
        pub static EXE_SUFFIX: &'static str = "";
    }

    pub mod freebsd {
        pub static SYSNAME: &'static str = "freebsd";
        pub static DLL_PREFIX: &'static str = "lib";
        pub static DLL_SUFFIX: &'static str = ".so";
        pub static EXE_SUFFIX: &'static str = "";
    }

    pub mod linux {
        pub static SYSNAME: &'static str = "linux";
        pub static DLL_PREFIX: &'static str = "lib";
        pub static DLL_SUFFIX: &'static str = ".so";
        pub static EXE_SUFFIX: &'static str = "";
    }

    pub mod android {
        pub static SYSNAME: &'static str = "android";
        pub static DLL_PREFIX: &'static str = "lib";
        pub static DLL_SUFFIX: &'static str = ".so";
        pub static EXE_SUFFIX: &'static str = "";
    }

    pub mod win32 {
        pub static SYSNAME: &'static str = "win32";
        pub static DLL_PREFIX: &'static str = "";
        pub static DLL_SUFFIX: &'static str = ".dll";
        pub static EXE_SUFFIX: &'static str = ".exe";
    }


    pub mod x86 {
        pub static ARCH: &'static str = "x86";
    }
    pub mod x86_64 {
        pub static ARCH: &'static str = "x86_64";
    }
    pub mod arm {
        pub static ARCH: &'static str = "arm";
    }
    pub mod mips {
        pub static ARCH: &'static str = "mips";
    }
}

#[cfg(test)]
#[allow(non_implicitly_copyable_typarams)]
mod tests {
    use libc::{c_int, c_void, size_t};
    use libc;
    use option::Some;
    use option;
    use os::{as_c_charp, env, getcwd, getenv, make_absolute, real_args};
    use os::{remove_file, setenv};
    use os;
    use path::Path;
    use rand::RngUtil;
    use rand;
    use run;
    use str;
    use vec;
    use libc::consts::os::posix88::{S_IRUSR, S_IWUSR, S_IXUSR};


    #[test]
    pub fn last_os_error() {
        debug!(os::last_os_error());
    }

    #[test]
    pub fn test_args() {
        let a = real_args();
        assert!(a.len() >= 1);
    }

    fn make_rand_name() -> ~str {
        let rng = rand::rng();
        let n = ~"TEST" + rng.gen_str(10u);
        assert!(getenv(n).is_none());
        n
    }

    #[test]
    fn test_setenv() {
        let n = make_rand_name();
        setenv(n, ~"VALUE");
        assert!(getenv(n) == option::Some(~"VALUE"));
    }

    #[test]
    #[ignore(cfg(windows))]
    #[ignore]
    fn test_setenv_overwrite() {
        let n = make_rand_name();
        setenv(n, ~"1");
        setenv(n, ~"2");
        assert!(getenv(n) == option::Some(~"2"));
        setenv(n, ~"");
        assert!(getenv(n) == option::Some(~""));
    }

    // Windows GetEnvironmentVariable requires some extra work to make sure
    // the buffer the variable is copied into is the right size
    #[test]
    #[ignore(cfg(windows))]
    #[ignore]
    fn test_getenv_big() {
        let mut s = ~"";
        let mut i = 0;
        while i < 100 { s += ~"aaaaaaaaaa"; i += 1; }
        let n = make_rand_name();
        setenv(n, s);
        debug!(copy s);
        assert!(getenv(n) == option::Some(s));
    }

    #[test]
    fn test_self_exe_path() {
        let path = os::self_exe_path();
        assert!(path.is_some());
        let path = path.get();
        debug!(copy path);

        // Hard to test this function
        assert!(path.is_absolute);
    }

    #[test]
    #[ignore]
    fn test_env_getenv() {
        let e = env();
        assert!(vec::len(e) > 0u);
        for vec::each(e) |p| {
            let (n, v) = copy *p;
            debug!(copy n);
            let v2 = getenv(n);
            // MingW seems to set some funky environment variables like
            // "=C:=C:\MinGW\msys\1.0\bin" and "!::=::\" that are returned
            // from env() but not visible from getenv().
            assert!(v2.is_none() || v2 == option::Some(v));
        }
    }

    #[test]
    fn test_env_setenv() {
        let n = make_rand_name();

        let mut e = env();
        setenv(n, ~"VALUE");
        assert!(!vec::contains(e, &(copy n, ~"VALUE")));

        e = env();
        assert!(vec::contains(e, &(n, ~"VALUE")));
    }

    #[test]
    fn test() {
        assert!((!Path("test-path").is_absolute));

        debug!(~"Current working directory: " + getcwd().to_str());

        debug!(make_absolute(&Path("test-path")));
        debug!(make_absolute(&Path("/usr/bin")));
    }

    #[test]
    #[cfg(unix)]
    fn homedir() {
        let oldhome = getenv(~"HOME");

        setenv(~"HOME", ~"/home/MountainView");
        assert!(os::homedir() == Some(Path("/home/MountainView")));

        setenv(~"HOME", ~"");
        assert!(os::homedir().is_none());

        for oldhome.each |s| { setenv(~"HOME", *s) }
    }

    #[test]
    #[cfg(windows)]
    fn homedir() {

        let oldhome = getenv(~"HOME");
        let olduserprofile = getenv(~"USERPROFILE");

        setenv(~"HOME", ~"");
        setenv(~"USERPROFILE", ~"");

        assert!(os::homedir().is_none());

        setenv(~"HOME", ~"/home/MountainView");
        assert!(os::homedir() == Some(Path("/home/MountainView")));

        setenv(~"HOME", ~"");

        setenv(~"USERPROFILE", ~"/home/MountainView");
        assert!(os::homedir() == Some(Path("/home/MountainView")));

        setenv(~"HOME", ~"/home/MountainView");
        setenv(~"USERPROFILE", ~"/home/PaloAlto");
        assert!(os::homedir() == Some(Path("/home/MountainView")));

        oldhome.each(|s| {setenv(~"HOME", *s);true});
        olduserprofile.each(|s| {setenv(~"USERPROFILE", *s);true});
    }

    #[test]
    fn tmpdir() {
        assert!(!str::is_empty(os::tmpdir().to_str()));
    }

    // Issue #712
    #[test]
    fn test_list_dir_no_invalid_memory_access() {
        os::list_dir(&Path("."));
    }

    #[test]
    fn list_dir() {
        let dirs = os::list_dir(&Path("."));
        // Just assuming that we've got some contents in the current directory
        assert!((vec::len(dirs) > 0u));

        for vec::each(dirs) |dir| {
            debug!(copy *dir);
        }
    }

    #[test]
    fn path_is_dir() {
        assert!((os::path_is_dir(&Path("."))));
        assert!((!os::path_is_dir(&Path("test/stdtest/fs.rs"))));
    }

    #[test]
    fn path_exists() {
        assert!((os::path_exists(&Path("."))));
        assert!((!os::path_exists(&Path(
                     "test/nonexistent-bogus-path"))));
    }

    #[test]
    fn copy_file_does_not_exist() {
      assert!(!os::copy_file(&Path("test/nonexistent-bogus-path"),
                            &Path("test/other-bogus-path")));
      assert!(!os::path_exists(&Path("test/other-bogus-path")));
    }

    #[test]
    fn copy_file_ok() {
        unsafe {
          let tempdir = getcwd(); // would like to use $TMPDIR,
                                  // doesn't seem to work on Linux
          assert!((str::len(tempdir.to_str()) > 0u));
          let in = tempdir.push("in.txt");
          let out = tempdir.push("out.txt");

          /* Write the temp input file */
            let ostream = do as_c_charp(in.to_str()) |fromp| {
                do as_c_charp("w+b") |modebuf| {
                    libc::fopen(fromp, modebuf)
                }
          };
          assert!((ostream as uint != 0u));
          let s = ~"hello";
          let mut buf = str::to_bytes(s) + ~[0 as u8];
          do vec::as_mut_buf(buf) |b, _len| {
              assert!((libc::fwrite(b as *c_void, 1u as size_t,
                                   (str::len(s) + 1u) as size_t, ostream)
                      == buf.len() as size_t))
          }
          assert!((libc::fclose(ostream) == (0u as c_int)));
          let rs = os::copy_file(&in, &out);
          if (!os::path_exists(&in)) {
            fail!(fmt!("%s doesn't exist", in.to_str()));
          }
          assert!((rs));
          let rslt = run::run_program(~"diff", ~[in.to_str(), out.to_str()]);
          assert!((rslt == 0));
          assert!((remove_file(&in)));
          assert!((remove_file(&out)));
        }
    }

    #[test]
    fn recursive_mkdir_slash() {
        let path = Path("/");
        assert!(os::mkdir_recursive(&path,  (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
    }

    #[test]
    fn recursive_mkdir_empty() {
        let path = Path("");
        assert!(!os::mkdir_recursive(&path, (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
    }

    // More recursive_mkdir tests are in std::tempfile
}