Add first sketch of the environment for the serializer circuit

msm/src/serialization/mod.rs

@@ -1,2 +1,3 @@
 pub mod columns;
 pub mod interpreter;
+pub mod witness;

msm/src/serialization/witness.rs

@@ -0,0 +1,29 @@
+use ark_ff::Field;
+
+use crate::LIMBS_NUM;
+
+/// Environment for the serializer interpreter
+/// It is parametrized by the number of field elements to be serialized and the
+/// field
+pub struct Env<const N: usize, Fp> {
+    pub step: usize,
+    pub kimchi_limbs: [[Fp; 3]; N],
+    pub current_kimchi_limbs: [Fp; 3],
+    /// The LIMB_NUM limbs that is used to encode a field element for the MSM
+    pub msm_limbs: [Fp; LIMBS_NUM],
+    /// Used for the decomposition in base 4 of the last limb of the foreign
+    /// field Kimchi gate
+    pub intermediate_limbs: [Fp; 19],
+}
+
+impl<const N: usize, Fp: Field> Env<N, Fp> {
+    pub fn create(kimchi_limbs: [[Fp; 3]; N]) -> Self {
+        Self {
+            step: 0,
+            kimchi_limbs,
+            current_kimchi_limbs: [Fp::zero(); 3],
+            msm_limbs: [Fp::zero(); LIMBS_NUM],
+            intermediate_limbs: [Fp::zero(); 19],
+        }
+    }
+}