crypto_bigint/uint/
from.rs

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1//! `From`-like conversions for [`UInt`].
2
3use crate::{Limb, UInt, WideWord, Word, U128, U64};
4
5impl<const LIMBS: usize> UInt<LIMBS> {
6    /// Create a [`UInt`] from a `u8` (const-friendly)
7    // TODO(tarcieri): replace with `const impl From<u8>` when stable
8    pub const fn from_u8(n: u8) -> Self {
9        assert!(LIMBS >= 1, "number of limbs must be greater than zero");
10        let mut limbs = [Limb::ZERO; LIMBS];
11        limbs[0].0 = n as Word;
12        Self { limbs }
13    }
14
15    /// Create a [`UInt`] from a `u16` (const-friendly)
16    // TODO(tarcieri): replace with `const impl From<u16>` when stable
17    pub const fn from_u16(n: u16) -> Self {
18        assert!(LIMBS >= 1, "number of limbs must be greater than zero");
19        let mut limbs = [Limb::ZERO; LIMBS];
20        limbs[0].0 = n as Word;
21        Self { limbs }
22    }
23
24    /// Create a [`UInt`] from a `u32` (const-friendly)
25    // TODO(tarcieri): replace with `const impl From<u32>` when stable
26    #[allow(trivial_numeric_casts)]
27    pub const fn from_u32(n: u32) -> Self {
28        assert!(LIMBS >= 1, "number of limbs must be greater than zero");
29        let mut limbs = [Limb::ZERO; LIMBS];
30        limbs[0].0 = n as Word;
31        Self { limbs }
32    }
33
34    /// Create a [`UInt`] from a `u64` (const-friendly)
35    // TODO(tarcieri): replace with `const impl From<u64>` when stable
36    #[cfg(target_pointer_width = "32")]
37    pub const fn from_u64(n: u64) -> Self {
38        assert!(LIMBS >= 2, "number of limbs must be two or greater");
39        let mut limbs = [Limb::ZERO; LIMBS];
40        limbs[0].0 = (n & 0xFFFFFFFF) as u32;
41        limbs[1].0 = (n >> 32) as u32;
42        Self { limbs }
43    }
44
45    /// Create a [`UInt`] from a `u64` (const-friendly)
46    // TODO(tarcieri): replace with `const impl From<u64>` when stable
47    #[cfg(target_pointer_width = "64")]
48    pub const fn from_u64(n: u64) -> Self {
49        assert!(LIMBS >= 1, "number of limbs must be greater than zero");
50        let mut limbs = [Limb::ZERO; LIMBS];
51        limbs[0].0 = n;
52        Self { limbs }
53    }
54
55    /// Create a [`UInt`] from a `u128` (const-friendly)
56    // TODO(tarcieri): replace with `const impl From<u128>` when stable
57    pub const fn from_u128(n: u128) -> Self {
58        assert!(
59            LIMBS >= (128 / Limb::BIT_SIZE),
60            "number of limbs must be greater than zero"
61        );
62
63        let lo = U64::from_u64((n & 0xffff_ffff_ffff_ffff) as u64);
64        let hi = U64::from_u64((n >> 64) as u64);
65
66        let mut limbs = [Limb::ZERO; LIMBS];
67
68        let mut i = 0;
69        while i < lo.limbs.len() {
70            limbs[i] = lo.limbs[i];
71            i += 1;
72        }
73
74        let mut j = 0;
75        while j < hi.limbs.len() {
76            limbs[i + j] = hi.limbs[j];
77            j += 1;
78        }
79
80        Self { limbs }
81    }
82
83    /// Create a [`UInt`] from a `Word` (const-friendly)
84    // TODO(tarcieri): replace with `const impl From<Word>` when stable
85    pub const fn from_word(n: Word) -> Self {
86        assert!(LIMBS >= 1, "number of limbs must be greater than zero");
87        let mut limbs = [Limb::ZERO; LIMBS];
88        limbs[0].0 = n;
89        Self { limbs }
90    }
91
92    /// Create a [`UInt`] from a `WideWord` (const-friendly)
93    // TODO(tarcieri): replace with `const impl From<WideWord>` when stable
94    pub const fn from_wide_word(n: WideWord) -> Self {
95        assert!(LIMBS >= 2, "number of limbs must be two or greater");
96        let mut limbs = [Limb::ZERO; LIMBS];
97        limbs[0].0 = n as Word;
98        limbs[1].0 = (n >> Limb::BIT_SIZE) as Word;
99        Self { limbs }
100    }
101}
102
103impl<const LIMBS: usize> From<u8> for UInt<LIMBS> {
104    fn from(n: u8) -> Self {
105        // TODO(tarcieri): const where clause when possible
106        debug_assert!(LIMBS > 0, "limbs must be non-zero");
107        Self::from_u8(n)
108    }
109}
110
111impl<const LIMBS: usize> From<u16> for UInt<LIMBS> {
112    fn from(n: u16) -> Self {
113        // TODO(tarcieri): const where clause when possible
114        debug_assert!(LIMBS > 0, "limbs must be non-zero");
115        Self::from_u16(n)
116    }
117}
118
119impl<const LIMBS: usize> From<u32> for UInt<LIMBS> {
120    fn from(n: u32) -> Self {
121        // TODO(tarcieri): const where clause when possible
122        debug_assert!(LIMBS > 0, "limbs must be non-zero");
123        Self::from_u32(n)
124    }
125}
126
127impl<const LIMBS: usize> From<u64> for UInt<LIMBS> {
128    fn from(n: u64) -> Self {
129        // TODO(tarcieri): const where clause when possible
130        debug_assert!(LIMBS >= (64 / Limb::BIT_SIZE), "not enough limbs");
131        Self::from_u64(n)
132    }
133}
134
135impl<const LIMBS: usize> From<u128> for UInt<LIMBS> {
136    fn from(n: u128) -> Self {
137        // TODO(tarcieri): const where clause when possible
138        debug_assert!(LIMBS >= (128 / Limb::BIT_SIZE), "not enough limbs");
139        Self::from_u128(n)
140    }
141}
142
143#[cfg(target_pointer_width = "32")]
144#[cfg_attr(docsrs, doc(cfg(target_pointer_width = "32")))]
145impl From<U64> for u64 {
146    fn from(n: U64) -> u64 {
147        (n.limbs[0].0 as u64) | ((n.limbs[1].0 as u64) << 32)
148    }
149}
150
151#[cfg(target_pointer_width = "64")]
152#[cfg_attr(docsrs, doc(cfg(target_pointer_width = "64")))]
153impl From<U64> for u64 {
154    fn from(n: U64) -> u64 {
155        n.limbs[0].into()
156    }
157}
158
159impl From<U128> for u128 {
160    fn from(n: U128) -> u128 {
161        let (hi, lo) = n.split();
162        (u64::from(hi) as u128) << 64 | (u64::from(lo) as u128)
163    }
164}
165
166impl<const LIMBS: usize> From<[Word; LIMBS]> for UInt<LIMBS> {
167    fn from(arr: [Word; LIMBS]) -> Self {
168        Self::from_words(arr)
169    }
170}
171
172impl<const LIMBS: usize> From<UInt<LIMBS>> for [Word; LIMBS] {
173    fn from(n: UInt<LIMBS>) -> [Word; LIMBS] {
174        *n.as_ref()
175    }
176}
177
178impl<const LIMBS: usize> From<[Limb; LIMBS]> for UInt<LIMBS> {
179    fn from(limbs: [Limb; LIMBS]) -> Self {
180        Self { limbs }
181    }
182}
183
184impl<const LIMBS: usize> From<UInt<LIMBS>> for [Limb; LIMBS] {
185    fn from(n: UInt<LIMBS>) -> [Limb; LIMBS] {
186        n.limbs
187    }
188}
189
190impl<const LIMBS: usize> From<Limb> for UInt<LIMBS> {
191    fn from(limb: Limb) -> Self {
192        limb.0.into()
193    }
194}
195
196#[cfg(test)]
197mod tests {
198    use crate::{Limb, Word, U128};
199
200    #[cfg(target_pointer_width = "32")]
201    use crate::U64 as UIntEx;
202
203    #[cfg(target_pointer_width = "64")]
204    use crate::U128 as UIntEx;
205
206    #[test]
207    fn from_u8() {
208        let n = UIntEx::from(42u8);
209        assert_eq!(n.limbs(), &[Limb(42), Limb(0)]);
210    }
211
212    #[test]
213    fn from_u16() {
214        let n = UIntEx::from(42u16);
215        assert_eq!(n.limbs(), &[Limb(42), Limb(0)]);
216    }
217
218    #[test]
219    fn from_u64() {
220        let n = UIntEx::from(42u64);
221        assert_eq!(n.limbs(), &[Limb(42), Limb(0)]);
222    }
223
224    #[test]
225    fn from_u128() {
226        let n = U128::from(42u128);
227        assert_eq!(&n.limbs()[..2], &[Limb(42), Limb(0)]);
228        assert_eq!(u128::from(n), 42u128);
229    }
230
231    #[test]
232    fn array_round_trip() {
233        let arr1 = [1, 2];
234        let n = UIntEx::from(arr1);
235        let arr2: [Word; 2] = n.into();
236        assert_eq!(arr1, arr2);
237    }
238}
crypto_bigint/uint/from.rs

crypto_bigint/uint/
from.rs
