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Use Wrapping struct for arithmetic wrapping in BIG/DBIG cmove #77

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Use Wrapping struct for arithmetic wrapping in BIG/DBIG cmove #77

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29 changes: 14 additions & 15 deletions rust/big.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,8 @@
* limitations under the License.
*/

use core::num::Wrapping;

use crate::arch;
use crate::arch::Chunk;

Expand Down Expand Up @@ -214,23 +216,20 @@ impl BIG {

#[inline(never)]
pub fn cmove(&mut self, g: &BIG, b: isize) -> Chunk {
static mut R:Chunk=0;
let w:Chunk;
unsafe {
R=R.wrapping_add(CONDMS);
w=R;
}
let bb=b as Chunk;
let c0=(!bb)&(w+1);
let c1=bb+w;
let w = Wrapping(CONDMS as Chunk);
let bb = Wrapping(b as Chunk);
let c0 = !bb & (w + Wrapping(1));
let c1 = bb + w;
for i in 0..NLEN {
let s = g.w[i];
let t = self.w[i];
unsafe{core::ptr::write_volatile(&mut self.w[i],t.wrapping_mul(c0).wrapping_add(s.wrapping_mul(c1)) /* c0*t+c1*s */)}
self.w[i]=self.w[i].wrapping_sub(w.wrapping_mul(t.wrapping_add(s)));
let s = Wrapping(g.w[i]);
let t = Wrapping(self.w[i]);
let c0_t = c0 * t;
let c1_s = c1 * s;
let w_tssum = w * (t + s);
unsafe { core::ptr::write_volatile(&mut self.w[i], (c0_t + c1_s - w_tssum).0) }
}
return 0 as Chunk;
}
return 0;
}

/*
pub fn cmove(&mut self, g: &BIG, d: isize) -> Chunk {
Expand Down
27 changes: 13 additions & 14 deletions rust/dbig.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,8 @@
* limitations under the License.
*/

use core::num::Wrapping;

use crate::arch;
use crate::arch::Chunk;
use crate::arch::CONDMS;
Expand Down Expand Up @@ -134,22 +136,19 @@ impl DBIG {

#[inline(never)]
pub fn cmove(&mut self, g: &DBIG, b: isize) -> Chunk {
static mut R:Chunk=0;
let w:Chunk;
unsafe {
R=R.wrapping_add(CONDMS);
w=R;
}
let bb=b as Chunk;
let c0=(!bb)&(w+1);
let c1=bb+w;
let w = Wrapping(CONDMS as Chunk);
let bb = Wrapping(b as Chunk);
let c0 = !bb & (w + Wrapping(1));
let c1 = bb + w;
for i in 0..big::DNLEN {
let s = g.w[i];
let t = self.w[i];
unsafe{core::ptr::write_volatile(&mut self.w[i],t.wrapping_mul(c0).wrapping_add(s.wrapping_mul(c1)))}
self.w[i]=self.w[i].wrapping_sub(w.wrapping_mul(t.wrapping_add(s)));
let s = Wrapping(g.w[i]);
let t = Wrapping(self.w[i]);
let c0_t = c0 * t;
let c1_s = c1 * s;
let w_tssum = w * (t + s);
unsafe { core::ptr::write_volatile(&mut self.w[i], (c0_t + c1_s - w_tssum).0) }
}
return 0 as Chunk;
return 0;
}

/* self+=x */
Expand Down