1 use rand::{self, Rng, SeedableRng};
2 use rand::{distributions::Alphanumeric, rngs::SmallRng};
3 use std::ffi::{OsStr, OsString};
4 use std::thread_local;
5 use std::{
6 cell::UnsafeCell,
7 path::{Path, PathBuf},
8 };
9 use std::{io, str};
10
11 use crate::error::IoResultExt;
12
13 thread_local! {
14 static THREAD_RNG: UnsafeCell<SmallRng> = UnsafeCell::new(SmallRng::from_entropy());
15 }
16
tmpname(prefix: &OsStr, suffix: &OsStr, rand_len: usize) -> OsString17 fn tmpname(prefix: &OsStr, suffix: &OsStr, rand_len: usize) -> OsString {
18 let mut buf = OsString::with_capacity(prefix.len() + suffix.len() + rand_len);
19 buf.push(prefix);
20
21 // Push each character in one-by-one. Unfortunately, this is the only
22 // safe(ish) simple way to do this without allocating a temporary
23 // String/Vec.
24 THREAD_RNG.with(|rng| unsafe {
25 (&mut *rng.get())
26 .sample_iter(&Alphanumeric)
27 .take(rand_len)
28 .for_each(|b| buf.push(str::from_utf8_unchecked(&[b as u8])))
29 });
30 buf.push(suffix);
31 buf
32 }
33
create_helper<F, R>( base: &Path, prefix: &OsStr, suffix: &OsStr, random_len: usize, f: F, ) -> io::Result<R> where F: Fn(PathBuf) -> io::Result<R>,34 pub fn create_helper<F, R>(
35 base: &Path,
36 prefix: &OsStr,
37 suffix: &OsStr,
38 random_len: usize,
39 f: F,
40 ) -> io::Result<R>
41 where
42 F: Fn(PathBuf) -> io::Result<R>,
43 {
44 let num_retries = if random_len != 0 {
45 crate::NUM_RETRIES
46 } else {
47 1
48 };
49
50 for _ in 0..num_retries {
51 let path = base.join(tmpname(prefix, suffix, random_len));
52 return match f(path) {
53 Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => continue,
54 res => res,
55 };
56 }
57
58 Err(io::Error::new(
59 io::ErrorKind::AlreadyExists,
60 "too many temporary files exist",
61 ))
62 .with_err_path(|| base)
63 }
64