38 lines
917 B
Rust
38 lines
917 B
Rust
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use alloc::borrow::Cow;
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use core::iter::repeat;
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use smallvec::SmallVec;
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use crate::big_digit::BITS;
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use crate::BigUint;
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#[inline]
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pub fn biguint_shl(n: Cow<BigUint>, bits: usize) -> BigUint {
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let n_unit = bits / BITS;
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let mut data = match n_unit {
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0 => n.into_owned().data,
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_ => {
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let len = n_unit + n.data.len() + 1;
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let mut data = SmallVec::with_capacity(len);
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data.extend(repeat(0).take(n_unit));
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data.extend(n.data.iter().cloned());
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data
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}
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};
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let n_bits = bits % BITS;
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if n_bits > 0 {
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let mut carry = 0;
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for elem in data[n_unit..].iter_mut() {
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let new_carry = *elem >> (BITS - n_bits);
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*elem = (*elem << n_bits) | carry;
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carry = new_carry;
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}
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if carry != 0 {
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data.push(carry);
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}
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}
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BigUint::new_native(data)
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}
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