/rust/registry/src/index.crates.io-1949cf8c6b5b557f/regex-automata-0.4.9/src/util/int.rs

Source
/*!
This module provides several integer oriented traits for converting between
both fixed size integers and integers whose size varies based on the target
(like `usize`).

The driving design principle of this module is to attempt to centralize as many
`as` casts as possible here. And in particular, we separate casts into two
buckets:

* Casts that we use for their truncating behavior. In this case, we use more
descriptive names, like `low_u32` and `high_u32`.
* Casts that we use for converting back-and-forth between `usize`. These
conversions are generally necessary because we often store indices in different
formats to save on memory, which requires converting to and from `usize`. In
this case, we very specifically do not want to overflow, and so the methods
defined here will panic if the `as` cast would be lossy in debug mode. (A
normal `as` cast will never panic!)

For `as` casts between raw pointers, we use `cast`, so `as` isn't needed there.

For regex engines, floating point is just never used, so we don't have to worry
about `as` casts for those.

Otherwise, this module pretty much covers all of our `as` needs except for one
thing: const contexts. There are a select few places in this crate where we
still need to use `as` because const functions on traits aren't stable yet.
If we wind up significantly expanding our const footprint in this crate, it
might be worth defining free functions to handle those cases. But at the time
of writing, that just seemed like too much ceremony. Instead, I comment each
such use of `as` in a const context with a "fixme" notice.

NOTE: for simplicity, we don't take target pointer width into account here for
`usize` conversions. Since we currently only panic in debug mode, skipping the
check when it can be proven it isn't needed at compile time doesn't really
matter. Now, if we wind up wanting to do as many checks as possible in release
mode, then we would want to skip those when we know the conversions are always
non-lossy.

NOTE: this module isn't an exhaustive API. For example, we still use things
like `u64::from` where possible, or even `usize::try_from()` for when we do
explicitly want to panic or when we want to return an error for overflow.
*/

// We define a little more than what we need, but I'd rather just have
// everything via a consistent and uniform API then have holes.
#![allow(dead_code)]

pub(crate) trait U8 {
    fn as_usize(self) -> usize;
}

impl U8 for u8 {
    fn as_usize(self) -> usize {
        usize::from(self)
    }
}

pub(crate) trait U16 {
    fn as_usize(self) -> usize;
    fn low_u8(self) -> u8;
    fn high_u8(self) -> u8;
}

impl U16 for u16 {
    fn as_usize(self) -> usize {
        usize::from(self)
    }

    fn low_u8(self) -> u8 {
        self as u8
    }

    fn high_u8(self) -> u8 {
        (self >> 8) as u8
    }
}

pub(crate) trait U32 {
    fn as_usize(self) -> usize;
    fn low_u8(self) -> u8;
    fn low_u16(self) -> u16;
    fn high_u16(self) -> u16;
}

impl U32 for u32 {
    fn as_usize(self) -> usize {
        #[cfg(debug_assertions)]
        {
            usize::try_from(self).expect("u32 overflowed usize")
        }
        #[cfg(not(debug_assertions))]
        {
            self as usize
        }
    }

    fn low_u8(self) -> u8 {
        self as u8
    }

    fn low_u16(self) -> u16 {
        self as u16
    }

    fn high_u16(self) -> u16 {
        (self >> 16) as u16
    }
}

pub(crate) trait U64 {
    fn as_usize(self) -> usize;
    fn low_u8(self) -> u8;
    fn low_u16(self) -> u16;
    fn low_u32(self) -> u32;
    fn high_u32(self) -> u32;
}

impl U64 for u64 {
    fn as_usize(self) -> usize {
        #[cfg(debug_assertions)]
        {
            usize::try_from(self).expect("u64 overflowed usize")
        }
        #[cfg(not(debug_assertions))]
        {
            self as usize
        }
    }

    fn low_u8(self) -> u8 {
        self as u8
    }

    fn low_u16(self) -> u16 {
        self as u16
    }

    fn low_u32(self) -> u32 {
        self as u32
    }

    fn high_u32(self) -> u32 {
        (self >> 32) as u32
    }
}

pub(crate) trait I32 {
    fn as_usize(self) -> usize;
    fn to_bits(self) -> u32;
    fn from_bits(n: u32) -> i32;
}

impl I32 for i32 {
    fn as_usize(self) -> usize {
        #[cfg(debug_assertions)]
        {
            usize::try_from(self).expect("i32 overflowed usize")
        }
        #[cfg(not(debug_assertions))]
        {
            self as usize
        }
    }

    fn to_bits(self) -> u32 {
        self as u32
    }

    fn from_bits(n: u32) -> i32 {
        n as i32
    }
}

pub(crate) trait Usize {
    fn as_u8(self) -> u8;
    fn as_u16(self) -> u16;
    fn as_u32(self) -> u32;
    fn as_u64(self) -> u64;
}

impl Usize for usize {
    fn as_u8(self) -> u8 {
        #[cfg(debug_assertions)]
        {
            u8::try_from(self).expect("usize overflowed u8")
        }
        #[cfg(not(debug_assertions))]
        {
            self as u8
        }
    }

    fn as_u16(self) -> u16 {
        #[cfg(debug_assertions)]
        {
            u16::try_from(self).expect("usize overflowed u16")
        }
        #[cfg(not(debug_assertions))]
        {
            self as u16
        }
    }

    fn as_u32(self) -> u32 {
        #[cfg(debug_assertions)]
        {
            u32::try_from(self).expect("usize overflowed u32")
        }
        #[cfg(not(debug_assertions))]
        {
            self as u32
        }
    }

    fn as_u64(self) -> u64 {
        #[cfg(debug_assertions)]
        {
            u64::try_from(self).expect("usize overflowed u64")
        }
        #[cfg(not(debug_assertions))]
        {
            self as u64
        }
    }
}

// Pointers aren't integers, but we convert pointers to integers to perform
// offset arithmetic in some places. (And no, we don't convert the integers
// back to pointers.) So add 'as_usize' conversions here too for completeness.
//
// These 'as' casts are actually okay because they're always non-lossy. But the
// idea here is to just try and remove as much 'as' as possible, particularly
// in this crate where we are being really paranoid about offsets and making
// sure we don't panic on inputs that might be untrusted. This way, the 'as'
// casts become easier to audit if they're all in one place, even when some of
// them are actually okay 100% of the time.

pub(crate) trait Pointer {
    fn as_usize(self) -> usize;
}

impl<T> Pointer for *const T {
    fn as_usize(self) -> usize {
        self as usize
    }
}

Coverage Report

Created: 2025-10-31 06:57

Line	Count	Source
1		/*!
2		This module provides several integer oriented traits for converting between
3		both fixed size integers and integers whose size varies based on the target
4		(like `usize`).
5
6		The driving design principle of this module is to attempt to centralize as many
7		`as` casts as possible here. And in particular, we separate casts into two
8		buckets:
9
10		* Casts that we use for their truncating behavior. In this case, we use more
11		descriptive names, like `low_u32` and `high_u32`.
12		* Casts that we use for converting back-and-forth between `usize`. These
13		conversions are generally necessary because we often store indices in different
14		formats to save on memory, which requires converting to and from `usize`. In
15		this case, we very specifically do not want to overflow, and so the methods
16		defined here will panic if the `as` cast would be lossy in debug mode. (A
17		normal `as` cast will never panic!)
18
19		For `as` casts between raw pointers, we use `cast`, so `as` isn't needed there.
20
21		For regex engines, floating point is just never used, so we don't have to worry
22		about `as` casts for those.
23
24		Otherwise, this module pretty much covers all of our `as` needs except for one
25		thing: const contexts. There are a select few places in this crate where we
26		still need to use `as` because const functions on traits aren't stable yet.
27		If we wind up significantly expanding our const footprint in this crate, it
28		might be worth defining free functions to handle those cases. But at the time
29		of writing, that just seemed like too much ceremony. Instead, I comment each
30		such use of `as` in a const context with a "fixme" notice.
31
32		NOTE: for simplicity, we don't take target pointer width into account here for
33		`usize` conversions. Since we currently only panic in debug mode, skipping the
34		check when it can be proven it isn't needed at compile time doesn't really
35		matter. Now, if we wind up wanting to do as many checks as possible in release
36		mode, then we would want to skip those when we know the conversions are always
37		non-lossy.
38
39		NOTE: this module isn't an exhaustive API. For example, we still use things
40		like `u64::from` where possible, or even `usize::try_from()` for when we do
41		explicitly want to panic or when we want to return an error for overflow.
42		*/
43
44		// We define a little more than what we need, but I'd rather just have
45		// everything via a consistent and uniform API then have holes.
46		#![allow(dead_code)]
47
48		pub(crate) trait U8 {
49		fn as_usize(self) -> usize;
50		}
51
52		impl U8 for u8 {
53	0	fn as_usize(self) -> usize {
54	0	usize::from(self)
55	0	}
56		}
57
58		pub(crate) trait U16 {
59		fn as_usize(self) -> usize;
60		fn low_u8(self) -> u8;
61		fn high_u8(self) -> u8;
62		}
63
64		impl U16 for u16 {
65	0	fn as_usize(self) -> usize {
66	0	usize::from(self)
67	0	}
68
69	0	fn low_u8(self) -> u8 {
70	0	self as u8
71	0	}
72
73	0	fn high_u8(self) -> u8 {
74	0	(self >> 8) as u8
75	0	}
76		}
77
78		pub(crate) trait U32 {
79		fn as_usize(self) -> usize;
80		fn low_u8(self) -> u8;
81		fn low_u16(self) -> u16;
82		fn high_u16(self) -> u16;
83		}
84
85		impl U32 for u32 {
86	0	fn as_usize(self) -> usize {
87		#[cfg(debug_assertions)]
88		{
89		usize::try_from(self).expect("u32 overflowed usize")
90		}
91		#[cfg(not(debug_assertions))]
92		{
93	0	self as usize
94		}
95	0	}
96
97	0	fn low_u8(self) -> u8 {
98	0	self as u8
99	0	}
100
101	0	fn low_u16(self) -> u16 {
102	0	self as u16
103	0	}
104
105	0	fn high_u16(self) -> u16 {
106	0	(self >> 16) as u16
107	0	}
108		}
109
110		pub(crate) trait U64 {
111		fn as_usize(self) -> usize;
112		fn low_u8(self) -> u8;
113		fn low_u16(self) -> u16;
114		fn low_u32(self) -> u32;
115		fn high_u32(self) -> u32;
116		}
117
118		impl U64 for u64 {
119	0	fn as_usize(self) -> usize {
120		#[cfg(debug_assertions)]
121		{
122		usize::try_from(self).expect("u64 overflowed usize")
123		}
124		#[cfg(not(debug_assertions))]
125		{
126	0	self as usize
127		}
128	0	}
129
130	0	fn low_u8(self) -> u8 {
131	0	self as u8
132	0	}
133
134	0	fn low_u16(self) -> u16 {
135	0	self as u16
136	0	}
137
138	0	fn low_u32(self) -> u32 {
139	0	self as u32
140	0	}
141
142	0	fn high_u32(self) -> u32 {
143	0	(self >> 32) as u32
144	0	}
145		}
146
147		pub(crate) trait I32 {
148		fn as_usize(self) -> usize;
149		fn to_bits(self) -> u32;
150		fn from_bits(n: u32) -> i32;
151		}
152
153		impl I32 for i32 {
154	0	fn as_usize(self) -> usize {
155		#[cfg(debug_assertions)]
156		{
157		usize::try_from(self).expect("i32 overflowed usize")
158		}
159		#[cfg(not(debug_assertions))]
160		{
161	0	self as usize
162		}
163	0	}
164
165	0	fn to_bits(self) -> u32 {
166	0	self as u32
167	0	}
168
169	0	fn from_bits(n: u32) -> i32 {
170	0	n as i32
171	0	}
172		}
173
174		pub(crate) trait Usize {
175		fn as_u8(self) -> u8;
176		fn as_u16(self) -> u16;
177		fn as_u32(self) -> u32;
178		fn as_u64(self) -> u64;
179		}
180
181		impl Usize for usize {
182	0	fn as_u8(self) -> u8 {
183		#[cfg(debug_assertions)]
184		{
185		u8::try_from(self).expect("usize overflowed u8")
186		}
187		#[cfg(not(debug_assertions))]
188		{
189	0	self as u8
190		}
191	0	}
192
193	0	fn as_u16(self) -> u16 {
194		#[cfg(debug_assertions)]
195		{
196		u16::try_from(self).expect("usize overflowed u16")
197		}
198		#[cfg(not(debug_assertions))]
199		{
200	0	self as u16
201		}
202	0	}
203
204	0	fn as_u32(self) -> u32 {
205		#[cfg(debug_assertions)]
206		{
207		u32::try_from(self).expect("usize overflowed u32")
208		}
209		#[cfg(not(debug_assertions))]
210		{
211	0	self as u32
212		}
213	0	}
214
215	0	fn as_u64(self) -> u64 {
216		#[cfg(debug_assertions)]
217		{
218		u64::try_from(self).expect("usize overflowed u64")
219		}
220		#[cfg(not(debug_assertions))]
221		{
222	0	self as u64
223		}
224	0	}
225		}
226
227		// Pointers aren't integers, but we convert pointers to integers to perform
228		// offset arithmetic in some places. (And no, we don't convert the integers
229		// back to pointers.) So add 'as_usize' conversions here too for completeness.
230		//
231		// These 'as' casts are actually okay because they're always non-lossy. But the
232		// idea here is to just try and remove as much 'as' as possible, particularly
233		// in this crate where we are being really paranoid about offsets and making
234		// sure we don't panic on inputs that might be untrusted. This way, the 'as'
235		// casts become easier to audit if they're all in one place, even when some of
236		// them are actually okay 100% of the time.
237
238		pub(crate) trait Pointer {
239		fn as_usize(self) -> usize;
240		}
241
242		impl<T> Pointer for *const T {
243	0	fn as_usize(self) -> usize {
244	0	self as usize
245	0	}
246		}