microsd 0.2.0

Light‐weight systemd auxiliars
Documentation 
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
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128

use std::alloc::{Layout, alloc, dealloc, handle_alloc_error};
use std::ffi::CStr;
use std::fmt;
use std::ptr::{self, NonNull};
use std::sync::atomic::AtomicPtr;

use crate::atomic;

enum ThinStrRaw {}
pub struct ThinStr(NonNull<ThinStrRaw>);
pub struct AtomicThinStr(AtomicPtr<ThinStrRaw>);

impl ThinStr {
	fn layout(size: usize) -> (Layout, usize) {
		Layout::array::<u8>(size)
			.and_then(|layout| Layout::new::<usize>().extend(layout))
			.unwrap_or_else(|_| handle_alloc_error(Layout::new::<()>()))
	}

	pub fn new(src: &(impl ?Sized + AsRef<str>)) -> Self {
		let slice = src.as_ref().as_bytes();
		let (layout, offset) = Self::layout(slice.len());
		let ptr = unsafe { alloc(layout) };
		if ptr.is_null() {
			handle_alloc_error(layout);
		}

		unsafe { ptr.cast::<usize>().write(slice.len()) };
		unsafe {
			ptr.byte_add(offset).copy_from_nonoverlapping(slice.as_ptr(), slice.len());
		};

		Self(unsafe { NonNull::new_unchecked(ptr.cast()) })
	}

	#[inline]
	pub fn from_cstr(cstr: &(impl ?Sized + AsRef<CStr>)) -> Option<Self> {
		cstr.as_ref().to_str().ok().map(Self::new)
	}

	#[inline]
	pub fn len(&self) -> usize {
		unsafe { self.0.cast::<usize>().read() }
	}

	#[inline]
	pub fn as_ptr(&self) -> NonNull<[u8]> {
		let size = self.len();
		unsafe {
			NonNull::slice_from_raw_parts(self.0.byte_add(Self::layout(size).1).cast(), size)
		}
	}

	#[inline]
	pub fn as_bytes(&self) -> &[u8] {
		unsafe { self.as_ptr().as_ref() }
	}

	#[inline]
	pub fn as_str(&self) -> &str {
		unsafe { str::from_utf8_unchecked(self.as_bytes()) }
	}

	#[inline]
	fn into_raw(self) -> *mut ThinStrRaw {
		let ptr = self.0.as_ptr().cast();
		std::mem::forget(self);
		ptr
	}

	#[inline]
	unsafe fn from_raw(raw: *mut ThinStrRaw) -> Option<Self> {
		NonNull::new(raw.cast()).map(Self)
	}
}

impl Drop for ThinStr {
	fn drop(&mut self) {
		unsafe { dealloc(self.0.as_ptr().cast(), Self::layout(self.len()).0); }
	}
}

impl fmt::Debug for ThinStr {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.as_str().fmt(f) }
}

impl AsRef<str> for ThinStr {
	#[inline]
	fn as_ref(&self) -> &str { self.as_str() }
}

impl AtomicThinStr {
	pub const fn new() -> Self {
		Self(AtomicPtr::new(ptr::null_mut()))
	}

	pub fn load(&self) -> Option<ThinStr> {
		unsafe { ThinStr::from_raw(atomic::load!(self.0)) }
	}

	pub fn store(&self, thin: ThinStr) {
		atomic::store!(self.0, thin.into_raw());
	}
}

#[cfg(test)]
mod tests {
	use super::ThinStr;

	#[test]
	fn eq() {
		let wide = "foo";
		let thin = ThinStr::new(wide);

		assert_eq!(wide.len(), thin.len());
		assert_eq!(wide, thin.as_str());
	}

	#[test]
	fn restore() {
		let wide = "bar";
		let thin = unsafe {
			ThinStr::from_raw(ThinStr::new(wide).into_raw()).unwrap()
		};

		assert_eq!(wide, thin.as_str());
	}
}