Add truncated_blake2s

src/lib.cairo

@@ -1,3 +1,4 @@
 mod channel;
+mod vector_commitment;
 mod common;
 mod structs;

src/vector_commitment.cairo

@@ -0,0 +1,4 @@
+mod vector_commitment;
+
+#[cfg(test)]
+mod tests;

src/vector_commitment/tests.cairo

@@ -0,0 +1 @@
+mod test_vector_commitment;

src/vector_commitment/tests/test_vector_commitment.cairo

@@ -0,0 +1,11 @@
+use cairo_verifier::vector_commitment::vector_commitment::truncated_blake2s;
+use core::debug::PrintTrait;
+
+#[test]
+#[available_gas(9999999999)]
+fn test_truncated_blake2s() {
+    let x = 1157029198022238202306346125123666191662554108005;
+    let y = 129252051435949032402481343903845417193011527432;
+    let out = truncated_blake2s(x, y);
+    assert(out == 642191007116032514313255519742888271333651019057, 'invalid truncated_blake2s');
+}

src/vector_commitment/vector_commitment.cairo

@@ -0,0 +1,13 @@
+use cairo_verifier::common::flip_endianness::FlipEndiannessTrait;
+use cairo_verifier::common::{
+    array_append::ArrayAppendTrait,
+    blake2s::blake2s,
+};
+
+fn truncated_blake2s(x: felt252, y: felt252) -> felt252 {
+    let mut data = ArrayTrait::<u32>::new();
+    data.append_big_endian(x);
+    data.append_big_endian(y);
+    let hash = blake2s(data).flip_endianness() % 0x10000000000000000000000000000000000000000;
+    hash.try_into().unwrap()
+}