refactor: separate OffsetToBytes trait from transpose module (PROOF-8…

…97) (#95)

# Rationale for this change
In an effort to support Blitzar's new `packed_msm` interface, we need to
make a number of updates to the Dory commitment computation. A future PR
will require the use of the `OffsetToBytes` trait. This PR separates the
trait into a different file to make future usage easier.

# What changes are included in this PR?
- The `OffsetToBytes` trait is moved to its own file.

# Are these changes tested?
Yes.

crates/proof-of-sql/src/proof_primitive/dory/dory_commitment_helper_gpu.rs

@@ -1,11 +1,12 @@
 use super::{pairings, transpose, DoryCommitment, DoryProverPublicSetup, DoryScalar, G1Affine};
-use crate::base::commitment::CommittableColumn;
+use crate::{
+    base::commitment::CommittableColumn, proof_primitive::dory::offset_to_bytes::OffsetToBytes,
+};
 use ark_bls12_381::Fr;
 use ark_ec::CurveGroup;
 use ark_std::ops::Mul;
 use blitzar::{compute::ElementP2, sequence::Sequence};
 use rayon::prelude::*;
-use zerocopy::AsBytes;
 
 #[tracing::instrument(name = "get_offset_commits (gpu)", level = "debug", skip_all)]
 fn get_offset_commits(
@@ -94,7 +95,7 @@ fn compute_dory_commitment_impl<'a, T>(
 where
     &'a T: Into<DoryScalar>,
     &'a [T]: Into<Sequence<'a>>,
-    T: AsBytes + Copy + transpose::OffsetToBytes,
+    T: OffsetToBytes,
 {
     let num_columns = 1 << setup.sigma();
     let data_size = std::mem::size_of::<T>();

crates/proof-of-sql/src/proof_primitive/dory/mod.rs

@@ -138,6 +138,7 @@ type DeferredGT = deferred_msm::DeferredMSM<GT, F>;
 type DeferredG1 = deferred_msm::DeferredMSM<G1Affine, F>;
 type DeferredG2 = deferred_msm::DeferredMSM<G2Affine, F>;
 
+mod offset_to_bytes;
 mod pairings;
 mod transpose;
 

crates/proof-of-sql/src/proof_primitive/dory/offset_to_bytes.rs

@@ -0,0 +1,110 @@
+use super::F;
+use zerocopy::AsBytes;
+
+pub trait OffsetToBytes {
+    const IS_SIGNED: bool;
+    fn min_as_fr() -> F;
+    fn offset_to_bytes(&self) -> Vec<u8>;
+}
+
+impl OffsetToBytes for u8 {
+    const IS_SIGNED: bool = false;
+
+    fn min_as_fr() -> F {
+        F::from(0)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        vec![*self]
+    }
+}
+
+impl OffsetToBytes for i16 {
+    const IS_SIGNED: bool = true;
+
+    fn min_as_fr() -> F {
+        F::from(i16::MIN)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        let shifted = self.wrapping_sub(i16::MIN);
+        shifted.to_le_bytes().to_vec()
+    }
+}
+
+impl OffsetToBytes for i32 {
+    const IS_SIGNED: bool = true;
+
+    fn min_as_fr() -> F {
+        F::from(i32::MIN)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        let shifted = self.wrapping_sub(i32::MIN);
+        shifted.to_le_bytes().to_vec()
+    }
+}
+
+impl OffsetToBytes for i64 {
+    const IS_SIGNED: bool = true;
+
+    fn min_as_fr() -> F {
+        F::from(i64::MIN)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        let shifted = self.wrapping_sub(i64::MIN);
+        shifted.to_le_bytes().to_vec()
+    }
+}
+
+impl OffsetToBytes for i128 {
+    const IS_SIGNED: bool = true;
+
+    fn min_as_fr() -> F {
+        F::from(i128::MIN)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        let shifted = self.wrapping_sub(i128::MIN);
+        shifted.to_le_bytes().to_vec()
+    }
+}
+
+impl OffsetToBytes for bool {
+    const IS_SIGNED: bool = false;
+
+    fn min_as_fr() -> F {
+        F::from(false)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        vec![*self as u8]
+    }
+}
+
+impl OffsetToBytes for u64 {
+    const IS_SIGNED: bool = false;
+
+    fn min_as_fr() -> F {
+        F::from(0)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        let bytes = self.to_le_bytes();
+        bytes.to_vec()
+    }
+}
+
+impl OffsetToBytes for [u64; 4] {
+    const IS_SIGNED: bool = false;
+
+    fn min_as_fr() -> F {
+        F::from(0)
+    }
+
+    fn offset_to_bytes(&self) -> Vec<u8> {
+        let slice = self.as_bytes();
+        slice.to_vec()
+    }
+}

crates/proof-of-sql/src/proof_primitive/dory/transpose.rs

@@ -1,116 +1,7 @@
-use ark_bls12_381::Fr;
-use zerocopy::AsBytes;
-
-pub trait OffsetToBytes {
-    const IS_SIGNED: bool;
-    fn min_as_fr() -> Fr;
-    fn offset_to_bytes(&self) -> Vec<u8>;
-}
-
-impl OffsetToBytes for u8 {
-    const IS_SIGNED: bool = false;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(0)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        vec![*self]
-    }
-}
-
-impl OffsetToBytes for i16 {
-    const IS_SIGNED: bool = true;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(i16::MIN)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        let shifted = self.wrapping_sub(i16::MIN);
-        shifted.to_le_bytes().to_vec()
-    }
-}
-
-impl OffsetToBytes for i32 {
-    const IS_SIGNED: bool = true;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(i32::MIN)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        let shifted = self.wrapping_sub(i32::MIN);
-        shifted.to_le_bytes().to_vec()
-    }
-}
-
-impl OffsetToBytes for i64 {
-    const IS_SIGNED: bool = true;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(i64::MIN)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        let shifted = self.wrapping_sub(i64::MIN);
-        shifted.to_le_bytes().to_vec()
-    }
-}
-
-impl OffsetToBytes for i128 {
-    const IS_SIGNED: bool = true;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(i128::MIN)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        let shifted = self.wrapping_sub(i128::MIN);
-        shifted.to_le_bytes().to_vec()
-    }
-}
-
-impl OffsetToBytes for bool {
-    const IS_SIGNED: bool = false;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(false)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        vec![*self as u8]
-    }
-}
-
-impl OffsetToBytes for u64 {
-    const IS_SIGNED: bool = false;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(0)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        let bytes = self.to_le_bytes();
-        bytes.to_vec()
-    }
-}
-
-impl OffsetToBytes for [u64; 4] {
-    const IS_SIGNED: bool = false;
-
-    fn min_as_fr() -> Fr {
-        Fr::from(0)
-    }
-
-    fn offset_to_bytes(&self) -> Vec<u8> {
-        let slice = self.as_bytes();
-        slice.to_vec()
-    }
-}
+use crate::proof_primitive::dory::offset_to_bytes::OffsetToBytes;
 
 #[tracing::instrument(name = "transpose_for_fixed_msm (gpu)", level = "debug", skip_all)]
-pub fn transpose_for_fixed_msm<T: AsBytes + Copy + OffsetToBytes>(
+pub fn transpose_for_fixed_msm<T: OffsetToBytes>(
     column: &[T],
     offset: usize,
     rows: usize,
@@ -134,6 +25,7 @@ pub fn transpose_for_fixed_msm<T: AsBytes + Copy + OffsetToBytes>(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use zerocopy::AsBytes;
 
     #[test]
     fn we_can_transpose_empty_column() {