1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
extern crate libc;
use libc::size_t;
use std::iter::repeat;
use std::io::Error;
use std::os::raw::*;
const INITIAL_BUFFER_SIZE: usize = 512;
pub type Result<T> = ::std::result::Result<T, Error>;
pub unsafe fn vsprintf<V>(format: *const c_char,
va_list: *mut V) -> Result<String> {
vsprintf_raw(format, va_list).map(|bytes| {
String::from_utf8(bytes).expect("vsprintf result is not valid utf-8")
})
}
pub unsafe fn vsprintf_raw<V>(format: *const c_char,
va_list: *mut V) -> Result<Vec<u8>> {
let list_ptr = va_list as *mut c_void;
let mut buffer = Vec::new();
buffer.extend([0u8; INITIAL_BUFFER_SIZE].iter().cloned());
loop {
let character_count = vsnprintf_wrapper(
buffer.as_mut_ptr(), buffer.len(), format, list_ptr
);
if character_count == -1 {
return Err(Error::last_os_error());
} else {
assert!(character_count >= 0);
let character_count = character_count as usize;
let current_max = buffer.len() - 1;
if character_count > current_max {
let extra_space_required = character_count - current_max;
buffer.extend(repeat(0).take(extra_space_required as usize));
continue;
} else {
buffer = buffer.into_iter()
.take_while(|&b| b != 0)
.collect();
break;
}
}
}
Ok(buffer)
}
extern {
fn vsnprintf_wrapper(buffer: *mut u8,
size: size_t,
format: *const c_char,
va_list: *mut c_void) -> libc::c_int;
}