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feat: replace bitwise ORs in U256:from_bytes32 with addition #3947

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merged 2 commits into from
Jan 12, 2024
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feat: replace bitwise ORs in U256:from_bytes32 with addition #3947

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feat: replace bitwise ORs in `U256:from_bytes32` with addition
TomAFrench Jan 11, 2024
3af1ba4
Merge branch 'master' into tf/bitwise-or-to-add
TomAFrench Jan 11, 2024
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57 changes: 29 additions & 28 deletions yarn-project/noir-protocol-circuits/src/crates/types/src/utils/uint256.nr
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Original file line number Diff line number Diff line change
Expand Up @@ -14,41 +14,42 @@ struct U256 {

impl U256 {
pub fn from_bytes32(bytes : [u8;32]) -> U256 {
// We use addition rather than a bitwise OR as the bitshifts ensure that none of the bytes overlap each other.
let high_0 = ((bytes[0] as u64) << 56)
| ((bytes[1] as u64) << 48)
| ((bytes[2] as u64) << 40)
| ((bytes[3] as u64) << 32)
| ((bytes[4] as u64) << 24)
| ((bytes[5] as u64) << 16)
| ((bytes[6] as u64) << 8)
| (bytes[7] as u64);
+ ((bytes[1] as u64) << 48)
+ ((bytes[2] as u64) << 40)
+ ((bytes[3] as u64) << 32)
+ ((bytes[4] as u64) << 24)
+ ((bytes[5] as u64) << 16)
+ ((bytes[6] as u64) << 8)
+ (bytes[7] as u64);

let high_1 = ((bytes[8] as u64) << 56)
| ((bytes[9] as u64) << 48)
| ((bytes[10] as u64) << 40)
| ((bytes[11] as u64) << 32)
| ((bytes[12] as u64) << 24)
| ((bytes[13] as u64) << 16)
| ((bytes[14] as u64) << 8)
| (bytes[15] as u64);
+ ((bytes[9] as u64) << 48)
+ ((bytes[10] as u64) << 40)
+ ((bytes[11] as u64) << 32)
+ ((bytes[12] as u64) << 24)
+ ((bytes[13] as u64) << 16)
+ ((bytes[14] as u64) << 8)
+ (bytes[15] as u64);

let low_0 = ((bytes[16] as u64) << 56)
| ((bytes[17] as u64) << 48)
| ((bytes[18] as u64) << 40)
| ((bytes[19] as u64) << 32)
| ((bytes[20] as u64) << 24)
| ((bytes[21] as u64) << 16)
| ((bytes[22] as u64) << 8)
| (bytes[23] as u64);
+ ((bytes[17] as u64) << 48)
+ ((bytes[18] as u64) << 40)
+ ((bytes[19] as u64) << 32)
+ ((bytes[20] as u64) << 24)
+ ((bytes[21] as u64) << 16)
+ ((bytes[22] as u64) << 8)
+ (bytes[23] as u64);

let low_1 = ((bytes[24] as u64) << 56)
| ((bytes[25] as u64) << 48)
| ((bytes[26] as u64) << 40)
| ((bytes[27] as u64) << 32)
| ((bytes[28] as u64) << 24)
| ((bytes[29] as u64) << 16)
| ((bytes[30] as u64) << 8)
| (bytes[31] as u64);
+ ((bytes[25] as u64) << 48)
+ ((bytes[26] as u64) << 40)
+ ((bytes[27] as u64) << 32)
+ ((bytes[28] as u64) << 24)
+ ((bytes[29] as u64) << 16)
+ ((bytes[30] as u64) << 8)
+ (bytes[31] as u64);

U256{inner : [high_0, high_1, low_0, low_1]}
}
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