/rust/registry/src/index.crates.io-6f17d22bba15001f/ring-0.17.14/src/bits.rs

Source (jump to first uncovered line)
// Copyright 2016 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

//! Bit lengths.

use crate::{error::InputTooLongError, polyfill};

/// The length of something, in bits.
///
/// This can represent a bit length that isn't a whole number of bytes.
#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd)]
#[repr(transparent)]
pub struct BitLength<T = usize>(T);

pub(crate) trait FromByteLen<T>: Sized {
    /// Constructs a `BitLength` from the given length in bytes.
    ///
    /// Fails if `bytes * 8` is too large for a `T`.
    fn from_byte_len(bytes: T) -> Result<Self, InputTooLongError<T>>;
}

impl FromByteLen<usize> for BitLength<usize> {
    #[inline]
    fn from_byte_len(bytes: usize) -> Result<Self, InputTooLongError> {
        match bytes.checked_mul(8) {
            Some(bits) => Ok(Self(bits)),
            None => Err(InputTooLongError::new(bytes)),
        }
    }
}

impl FromByteLen<u64> for BitLength<u64> {
    #[inline]
    fn from_byte_len(bytes: u64) -> Result<Self, InputTooLongError<u64>> {
        match bytes.checked_mul(8) {
            Some(bits) => Ok(Self(bits)),
            None => Err(InputTooLongError::new(bytes)),
        }
    }
}

impl FromByteLen<usize> for BitLength<u64> {
    #[inline]
    fn from_byte_len(bytes: usize) -> Result<Self, InputTooLongError<usize>> {
        match polyfill::u64_from_usize(bytes).checked_mul(8) {
            Some(bits) => Ok(Self(bits)),
            None => Err(InputTooLongError::new(bytes)),
        }
    }
}

impl<T> BitLength<T> {
    /// Constructs a `BitLength` from the given length in bits.
    #[inline]
    pub const fn from_bits(bits: T) -> Self {
        Self(bits)
    }
}

impl<T: Copy> BitLength<T> {
    /// The number of bits this bit length represents, as the underlying type.
    #[inline]
    pub fn as_bits(self) -> T {
        self.0
    }
}

// Lengths measured in bits, where all arithmetic is guaranteed not to
// overflow.
impl BitLength<usize> {
    #[cfg(feature = "alloc")]
    #[inline]
    pub(crate) fn half_rounded_up(&self) -> Self {
        let round_up = self.0 & 1;
        Self((self.0 / 2) + round_up)
    }

    /// The bit length, rounded up to a whole number of bytes.
    #[inline]
    pub const fn as_usize_bytes_rounded_up(&self) -> usize {
        // Equivalent to (self.0 + 7) / 8, except with no potential for
        // overflow and without branches.

        // Branchless round_up = if self.0 & 0b111 != 0 { 1 } else { 0 };
        let round_up = ((self.0 >> 2) | (self.0 >> 1) | self.0) & 1;

        (self.0 / 8) + round_up
    }

    #[cfg(feature = "alloc")]
    #[inline]
    pub(crate) fn try_sub_1(self) -> Result<Self, crate::error::Unspecified> {
        let sum = self.0.checked_sub(1).ok_or(crate::error::Unspecified)?;
        Ok(Self(sum))
    }
}

impl BitLength<u64> {
    pub fn to_be_bytes(self) -> [u8; 8] {
        self.0.to_be_bytes()
    }
}

#[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
impl From<BitLength<usize>> for BitLength<u64> {
    fn from(BitLength(value): BitLength<usize>) -> Self {
        BitLength(polyfill::u64_from_usize(value))
    }
}

impl TryFrom<BitLength<u64>> for BitLength<core::num::NonZeroU64> {
    type Error = <core::num::NonZeroU64 as TryFrom<u64>>::Error;

    fn try_from(BitLength(value): BitLength<u64>) -> Result<Self, Self::Error> {
        value.try_into().map(BitLength)
    }
}

const _TEST_AS_USIZE_BYTES_ROUNDED_UP_EVEN: () =
    assert!(BitLength::from_bits(8192).as_usize_bytes_rounded_up() == 8192 / 8);
const _TEST_AS_USIZE_BYTES_ROUNDED_UP_ONE_BIT_HIGH: () =
    assert!(BitLength::from_bits(8192 + 1).as_usize_bytes_rounded_up() == (8192 / 8) + 1);
const _TEST_AS_USIZE_BYTES_ROUNDED_UP_SEVEN_BITS_HIGH: () =
    assert!(BitLength::from_bits(8192 + 7).as_usize_bytes_rounded_up() == (8192 / 8) + 1);

Line	Count	Source (jump to first uncovered line)
1		// Copyright 2016 Brian Smith.
2		//
3		// Permission to use, copy, modify, and/or distribute this software for any
4		// purpose with or without fee is hereby granted, provided that the above
5		// copyright notice and this permission notice appear in all copies.
6		//
7		// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8		// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9		// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10		// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11		// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12		// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13		// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15		//! Bit lengths.
16
17		use crate::{error::InputTooLongError, polyfill};
18
19		/// The length of something, in bits.
20		///
21		/// This can represent a bit length that isn't a whole number of bytes.
22		#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd)]
23		#[repr(transparent)]
24		pub struct BitLength<T = usize>(T);
25
26		pub(crate) trait FromByteLen<T>: Sized {
27		/// Constructs a `BitLength` from the given length in bytes.
28		///
29		/// Fails if `bytes * 8` is too large for a `T`.
30		fn from_byte_len(bytes: T) -> Result<Self, InputTooLongError<T>>;
31		}
32
33		impl FromByteLen<usize> for BitLength<usize> {
34		#[inline]
35	0	fn from_byte_len(bytes: usize) -> Result<Self, InputTooLongError> {
36	0	match bytes.checked_mul(8) {
37	0	Some(bits) => Ok(Self(bits)),
38	0	None => Err(InputTooLongError::new(bytes)),
39		}
40	0	}
41		}
42
43		impl FromByteLen<u64> for BitLength<u64> {
44		#[inline]
45	0	fn from_byte_len(bytes: u64) -> Result<Self, InputTooLongError<u64>> {
46	0	match bytes.checked_mul(8) {
47	0	Some(bits) => Ok(Self(bits)),
48	0	None => Err(InputTooLongError::new(bytes)),
49		}
50	0	}
51		}
52
53		impl FromByteLen<usize> for BitLength<u64> {
54		#[inline]
55	0	fn from_byte_len(bytes: usize) -> Result<Self, InputTooLongError<usize>> {
56	0	match polyfill::u64_from_usize(bytes).checked_mul(8) {
57	0	Some(bits) => Ok(Self(bits)),
58	0	None => Err(InputTooLongError::new(bytes)),
59		}
60	0	}
61		}
62
63		impl<T> BitLength<T> {
64		/// Constructs a `BitLength` from the given length in bits.
65		#[inline]
66	0	pub const fn from_bits(bits: T) -> Self {
67	0	Self(bits)
68	0	} Unexecuted instantiation: <ring::bits::BitLength<i32>>::from_bits Unexecuted instantiation: <ring::bits::BitLength>::from_bits
69		}
70
71		impl<T: Copy> BitLength<T> {
72		/// The number of bits this bit length represents, as the underlying type.
73		#[inline]
74	0	pub fn as_bits(self) -> T {
75	0	self.0
76	0	}
77		}
78
79		// Lengths measured in bits, where all arithmetic is guaranteed not to
80		// overflow.
81		impl BitLength<usize> {
82		#[cfg(feature = "alloc")]
83		#[inline]
84	0	pub(crate) fn half_rounded_up(&self) -> Self {
85	0	let round_up = self.0 & 1;
86	0	Self((self.0 / 2) + round_up)
87	0	}
88
89		/// The bit length, rounded up to a whole number of bytes.
90		#[inline]
91	0	pub const fn as_usize_bytes_rounded_up(&self) -> usize {
92	0	// Equivalent to (self.0 + 7) / 8, except with no potential for
93	0	// overflow and without branches.
94	0
95	0	// Branchless round_up = if self.0 & 0b111 != 0 { 1 } else { 0 };
96	0	let round_up = ((self.0 >> 2) \| (self.0 >> 1) \| self.0) & 1;
97	0
98	0	(self.0 / 8) + round_up
99	0	}
100
101		#[cfg(feature = "alloc")]
102		#[inline]
103	0	pub(crate) fn try_sub_1(self) -> Result<Self, crate::error::Unspecified> {
104	0	let sum = self.0.checked_sub(1).ok_or(crate::error::Unspecified)?;
105	0	Ok(Self(sum))
106	0	}
107		}
108
109		impl BitLength<u64> {
110	0	pub fn to_be_bytes(self) -> [u8; 8] {
111	0	self.0.to_be_bytes()
112	0	}
113		}
114
115		#[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
116		impl From<BitLength<usize>> for BitLength<u64> {
117	0	fn from(BitLength(value): BitLength<usize>) -> Self {
118	0	BitLength(polyfill::u64_from_usize(value))
119	0	}
120		}
121
122		impl TryFrom<BitLength<u64>> for BitLength<core::num::NonZeroU64> {
123		type Error = <core::num::NonZeroU64 as TryFrom<u64>>::Error;
124
125	0	fn try_from(BitLength(value): BitLength<u64>) -> Result<Self, Self::Error> {
126	0	value.try_into().map(BitLength)
127	0	}
128		}
129
130		const _TEST_AS_USIZE_BYTES_ROUNDED_UP_EVEN: () =
131		assert!(BitLength::from_bits(8192).as_usize_bytes_rounded_up() == 8192 / 8);
132		const _TEST_AS_USIZE_BYTES_ROUNDED_UP_ONE_BIT_HIGH: () =
133		assert!(BitLength::from_bits(8192 + 1).as_usize_bytes_rounded_up() == (8192 / 8) + 1);
134		const _TEST_AS_USIZE_BYTES_ROUNDED_UP_SEVEN_BITS_HIGH: () =
135		assert!(BitLength::from_bits(8192 + 7).as_usize_bytes_rounded_up() == (8192 / 8) + 1);

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Created: 2025-05-07 06:59