tempfile 2.2.0

Securely create temporary files.
Documentation 
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use std::os::windows::ffi::OsStrExt;
use std::os::windows::io::{FromRawHandle, AsRawHandle, RawHandle};
use std::path::Path;
use std::io;
use std::ptr;
use std::fs::File;
use winapi::{self, DWORD, HANDLE};
use kernel32::{CreateFileW, ReOpenFile, SetFileAttributesW, MoveFileExW};
use util;

#[cfg_attr(irustfmt, rustfmt_skip)]
const ACCESS: DWORD     = winapi::FILE_GENERIC_READ
                        | winapi::FILE_GENERIC_WRITE;
#[cfg_attr(irustfmt, rustfmt_skip)]
const SHARE_MODE: DWORD = winapi::FILE_SHARE_DELETE
                        | winapi::FILE_SHARE_READ
                        | winapi::FILE_SHARE_WRITE;
#[cfg_attr(irustfmt, rustfmt_skip)]
const FLAGS: DWORD      = winapi::FILE_ATTRIBUTE_HIDDEN
                        | winapi::FILE_ATTRIBUTE_TEMPORARY;


fn to_utf16(s: &Path) -> Vec<u16> {
    s.as_os_str().encode_wide().chain(Some(0).into_iter()).collect()
}

fn win_create(path: &Path,
              access: DWORD,
              share_mode: DWORD,
              disp: DWORD,
              flags: DWORD)
              -> io::Result<File> {

    let path = to_utf16(path);
    let handle = unsafe {
        CreateFileW(path.as_ptr(),
                    access,
                    share_mode,
                    0 as *mut _,
                    disp,
                    flags,
                    ptr::null_mut())
    };
    if handle == winapi::INVALID_HANDLE_VALUE {
        Err(io::Error::last_os_error())
    } else {
        Ok(unsafe { File::from_raw_handle(handle as RawHandle) })
    }
}

pub fn create_named(path: &Path) -> io::Result<File> {
    win_create(path, ACCESS, SHARE_MODE, winapi::CREATE_NEW, FLAGS)
}

pub fn create(dir: &Path) -> io::Result<File> {
    for _ in 0..::NUM_RETRIES {
        return match win_create(&dir.join(&util::tmpname(".tmp", "", ::NUM_RAND_CHARS)),
                                ACCESS,
                                0, // Exclusive
                                winapi::CREATE_NEW,
                                FLAGS | winapi::FILE_FLAG_DELETE_ON_CLOSE) {
            Ok(f) => Ok(f),
            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => continue,
            Err(e) => Err(e),
        };
    }
    Err(io::Error::new(io::ErrorKind::AlreadyExists,
                       "too many temporary directories already exist"))
}

pub fn reopen(file: &File, path: &Path) -> io::Result<File> {
    let handle = file.as_raw_handle();
    unsafe {
        let handle = ReOpenFile(handle as HANDLE, ACCESS, SHARE_MODE, 0);
        if handle == winapi::INVALID_HANDLE_VALUE {
            Err(io::Error::last_os_error())
        } else {
            Ok(FromRawHandle::from_raw_handle(handle as RawHandle))
        }
    }
}

pub fn persist(old_path: &Path, new_path: &Path, overwrite: bool) -> io::Result<()> {
    // TODO: We should probably do this in one-shot using SetFileInformationByHandle but the API is
    // really painful.

    unsafe {
        let old_path_w = to_utf16(old_path);
        let new_path_w = to_utf16(new_path);

        // Don't succeed if this fails. We don't want to claim to have successfully persisted a file
        // still marked as temporary because this file won't have the same consistency guarantees.
        if SetFileAttributesW(old_path_w.as_ptr(), winapi::FILE_ATTRIBUTE_NORMAL) == 0 {
            return Err(io::Error::last_os_error());
        }

        let mut flags = 0;

        if overwrite {
            flags |= winapi::MOVEFILE_REPLACE_EXISTING;
        }

        if MoveFileExW(old_path_w.as_ptr(), new_path_w.as_ptr(), flags) == 0 {
            let e = io::Error::last_os_error();
            // If this fails, the temporary file is now un-hidden and no longer marked temporary
            // (slightly less efficient) but it will still work.
            let _ = SetFileAttributesW(old_path_w.as_ptr(), FLAGS);
            Err(e)
        } else {
            Ok(())
        }
    }
}