feat: FunctionSelector type

circuits/cpp/src/aztec3/circuits/abis/.test.cpp

@@ -51,7 +51,10 @@ TEST(abi_tests, native_read_write_call_context)
 TEST(abi_tests, native_read_write_function_data)
 {
     FunctionData<NT> const function_data = {
-        .function_selector = 11,
+        .function_selector =
+            FunctionSelector<NT>{
+                .value = 11,
+            },
         .is_private = false,
         .is_constructor = false,
     };
@@ -67,7 +70,10 @@ TEST(abi_tests, native_read_write_function_data)
 TEST(abi_tests, native_to_circuit_function_data)
 {
     FunctionData<NT> const native_function_data = {
-        .function_selector = 11,
+        .function_selector =
+            FunctionSelector<NT>{
+                .value = 11,
+            },
         .is_private = false,
         .is_constructor = false,
     };

circuits/cpp/src/aztec3/circuits/abis/c_bind.test.cpp

@@ -191,7 +191,10 @@ TEST(abi_tests, compute_function_leaf)
 {
     // Construct FunctionLeafPreimage with some randomized fields
     auto const preimage = FunctionLeafPreimage<NT>{
-        .function_selector = engine.get_random_uint32(),
+        .function_selector =
+            FunctionSelector<NT>{
+                .value = engine.get_random_uint32(),
+            },
         .is_private = static_cast<bool>(engine.get_random_uint8() & 1),
         .vk_hash = NT::fr::random_element(),
         .acir_hash = NT::fr::random_element(),
@@ -279,7 +282,12 @@ TEST(abi_tests, compute_function_tree)
 TEST(abi_tests, hash_constructor)
 {
     // Randomize required values
-    auto const func_data = FunctionData<NT>{ .function_selector = 10, .is_private = true, .is_constructor = false };
+    auto const func_data = FunctionData<NT>{ .function_selector =
+                                                 FunctionSelector<NT>{
+                                                     .value = 10,
+                                                 },
+                                             .is_private = true,
+                                             .is_constructor = false };
 
     NT::fr const args_hash = NT::fr::random_element();
     NT::fr const constructor_vk_hash = NT::fr::random_element();

circuits/cpp/src/aztec3/circuits/abis/function_data.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "aztec3/circuits/abis/function_selector.hpp"
 #include "aztec3/constants.hpp"
 #include "aztec3/utils/types/circuit_types.hpp"
 #include "aztec3/utils/types/convert.hpp"
@@ -17,7 +18,7 @@ template <typename NCT> struct FunctionData {
     using boolean = typename NCT::boolean;
     using fr = typename NCT::fr;
 
-    uint32 function_selector;  // e.g. 1st 4-bytes of abi-encoding of function.
+    FunctionSelector<NCT> function_selector;
     boolean is_internal = false;
     boolean is_private = false;
     boolean is_constructor = false;
@@ -38,7 +39,7 @@ template <typename NCT> struct FunctionData {
         auto to_ct = [&](auto& e) { return aztec3::utils::types::to_ct(builder, e); };
 
         FunctionData<CircuitTypes<Builder>> function_data = {
-            to_ct(function_selector),
+            function_selector.to_circuit_type(builder),
             to_ct(is_internal),
             to_ct(is_private),
             to_ct(is_constructor),
@@ -50,10 +51,11 @@ template <typename NCT> struct FunctionData {
     template <typename Builder> FunctionData<NativeTypes> to_native_type() const
     {
         static_assert(std::is_same<CircuitTypes<Builder>, NCT>::value);
+        auto to_native_type = []<typename T>(T& e) { return e.template to_native_type<Builder>(); };
         auto to_nt = [&](auto& e) { return aztec3::utils::types::to_nt<Builder>(e); };
 
         FunctionData<NativeTypes> function_data = {
-            to_nt(function_selector),
+            to_native_type(function_selector),
             to_nt(is_internal),
             to_nt(is_private),
             to_nt(is_constructor),
@@ -66,7 +68,7 @@ template <typename NCT> struct FunctionData {
     {
         static_assert(!(std::is_same<NativeTypes, NCT>::value));
 
-        fr(function_selector).set_public();
+        function_selector.set_public();
         fr(is_internal).set_public();
         fr(is_private).set_public();
         fr(is_constructor).set_public();
@@ -76,7 +78,7 @@ template <typename NCT> struct FunctionData {
     fr hash() const
     {
         std::vector<fr> const inputs = {
-            fr(function_selector),
+            fr(function_selector.value),
             fr(is_internal),
             fr(is_private),
             fr(is_constructor),

circuits/cpp/src/aztec3/circuits/abis/function_leaf_preimage.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "aztec3/circuits/abis/function_selector.hpp"
 #include "aztec3/constants.hpp"
 #include "aztec3/utils/types/circuit_types.hpp"
 #include "aztec3/utils/types/convert.hpp"
@@ -31,7 +32,7 @@ template <typename NCT> struct FunctionLeafPreimage {
     using fr = typename NCT::fr;
     using uint32 = typename NCT::uint32;
 
-    uint32 function_selector = 0;
+    FunctionSelector<NCT> function_selector = {};
     boolean is_internal = false;
     boolean is_private = false;
     fr vk_hash = 0;
@@ -54,7 +55,11 @@ template <typename NCT> struct FunctionLeafPreimage {
         auto to_ct = [&](auto& e) { return aztec3::utils::types::to_ct(builder, e); };
 
         FunctionLeafPreimage<CircuitTypes<Builder>> preimage = {
-            to_ct(function_selector), to_ct(is_internal), to_ct(is_private), to_ct(vk_hash), to_ct(acir_hash),
+            function_selector.to_circuit_type(builder),
+            to_ct(is_internal),
+            to_ct(is_private),
+            to_ct(vk_hash),
+            to_ct(acir_hash),
         };
 
         return preimage;
@@ -63,10 +68,11 @@ template <typename NCT> struct FunctionLeafPreimage {
     template <typename Builder> FunctionLeafPreimage<NativeTypes> to_native_type() const
     {
         static_assert(std::is_same<CircuitTypes<Builder>, NCT>::value);
+        auto to_native_type = []<typename T>(T& e) { return e.template to_native_type<Builder>(); };
         auto to_nt = [&](auto& e) { return aztec3::utils::types::to_nt<Builder>(e); };
 
         FunctionLeafPreimage<NativeTypes> preimage = {
-            to_nt(function_selector), to_nt(is_internal), to_nt(is_private), to_nt(vk_hash), to_nt(acir_hash),
+            to_native_type(function_selector), to_nt(is_internal), to_nt(is_private), to_nt(vk_hash), to_nt(acir_hash),
         };
 
         return preimage;
@@ -86,7 +92,7 @@ template <typename NCT> struct FunctionLeafPreimage {
     fr hash() const
     {
         std::vector<fr> const inputs = {
-            function_selector, fr(is_internal), fr(is_private), vk_hash, acir_hash,
+            function_selector.value, fr(is_internal), fr(is_private), vk_hash, acir_hash,
         };
         return NCT::compress(inputs, GeneratorIndex::FUNCTION_LEAF);
     }

circuits/cpp/src/aztec3/circuits/abis/function_selector.hpp

@@ -0,0 +1,59 @@
+#pragma once
+
+#include "aztec3/utils/types/circuit_types.hpp"
+#include "aztec3/utils/types/convert.hpp"
+#include "aztec3/utils/types/native_types.hpp"
+
+#include "barretenberg/serialize/msgpack.hpp"
+
+namespace aztec3::circuits::abis {
+
+using aztec3::utils::types::CircuitTypes;
+using aztec3::utils::types::NativeTypes;
+
+template <typename NCT> struct FunctionSelector {
+    using uint32 = typename NCT::uint32;
+    using boolean = typename NCT::boolean;
+    using fr = typename NCT::fr;
+
+    uint32 value;  // e.g. 1st 4-bytes of abi-encoding of function.
+
+    MSGPACK_FIELDS(value);
+
+    boolean operator==(FunctionSelector<NCT> const& other) const { return value == other.value; };
+
+    template <typename Builder> FunctionSelector<CircuitTypes<Builder>> to_circuit_type(Builder& builder) const
+    {
+        static_assert((std::is_same<NativeTypes, NCT>::value));
+
+        // Capture the circuit builder:
+        auto to_ct = [&](auto& e) { return aztec3::utils::types::to_ct(builder, e); };
+
+        FunctionSelector<CircuitTypes<Builder>> function_selector = {
+            to_ct(value),
+        };
+
+        return function_selector;
+    };
+
+    template <typename Builder> FunctionSelector<NativeTypes> to_native_type() const
+    {
+        static_assert(std::is_same<CircuitTypes<Builder>, NCT>::value);
+        auto to_nt = [&](auto& e) { return aztec3::utils::types::to_nt<Builder>(e); };
+
+        FunctionSelector<NativeTypes> function_selector = {
+            to_nt(value),
+        };
+
+        return function_selector;
+    };
+
+    void set_public()
+    {
+        static_assert(!(std::is_same<NativeTypes, NCT>::value));
+
+        fr(value).set_public();
+    }
+};
+
+}  // namespace aztec3::circuits::abis

circuits/cpp/src/aztec3/circuits/apps/.test.cpp

@@ -75,7 +75,10 @@ class state_var_tests : public ::testing::Test {
             uint256_t(0x01071e9a23e0f7edULL, 0x5d77b35d1830fa3eULL, 0xc6ba3660bb1f0c0bULL, 0x2ef9f7f09867fd6eULL));
 
         FunctionData<NT> const function_data{
-            .function_selector = 1,  // TODO: deduce this from the contract, somehow.
+            .function_selector =
+                FunctionSelector<NT>{
+                    .value = 1,  // TODO: deduce this from the contract, somehow.
+                },
             .is_private = true,
             .is_constructor = false,
         };

circuits/cpp/src/aztec3/circuits/apps/contract.tpp

@@ -13,6 +13,7 @@ namespace aztec3::circuits::apps {
 
 using NT = aztec3::utils::types::NativeTypes;
 using aztec3::circuits::abis::FunctionData;
+using aztec3::circuits::abis::FunctionSelector;
 
 template <typename NCT> void Contract<NCT>::set_functions(std::vector<FunctionDeclaration<NCT>> const& functions)
 {
@@ -22,7 +23,10 @@ template <typename NCT> void Contract<NCT>::set_functions(std::vector<FunctionDe
             throw_or_abort("Name already exists");
         }
         function_datas[function.name] = FunctionData<NCT>{
-            .function_selector = static_cast<uint32>(i),
+            .function_selector =
+                FunctionSelector<NT>{
+                    .value = static_cast<uint32>(i),
+                },
             .is_private = function.is_private,
             .is_constructor = function.is_constructor,
         };

circuits/cpp/src/aztec3/circuits/apps/function_execution_context.hpp

@@ -178,7 +178,10 @@ template <typename Builder> class FunctionExecutionContext {
 
         const FunctionData<CT> f_function_data_ct{
             // Note: we MUST
-            .function_selector = f_encoding_ct,
+            .function_selector =
+                FunctionSelector<CT>{
+                    .value = f_encoding_ct,
+                },
             .is_private = true,
             .is_constructor = false,
         };

circuits/cpp/src/aztec3/circuits/apps/test_apps/escrow/.test.cpp

@@ -16,7 +16,10 @@ class escrow_tests : public ::testing::Test {
             uint256_t(0x01071e9a23e0f7edULL, 0x5d77b35d1830fa3eULL, 0xc6ba3660bb1f0c0bULL, 0x2ef9f7f09867fd6eULL));
 
         FunctionData<NT> const function_data{
-            .function_selector = 1,  // TODO: deduce this from the contract, somehow.
+            .function_selector =
+                FunctionSelector<NT>{
+                    .value = 1,  // TODO: deduce this from the contract, somehow.
+                },
             .is_private = true,
             .is_constructor = false,
         };

circuits/cpp/src/aztec3/circuits/apps/test_apps/private_to_private_function_call/.test.cpp

@@ -22,7 +22,10 @@ TEST(private_to_private_function_call_tests, circuit_private_to_private_function
         uint256_t(0x01071e9a23e0f7edULL, 0x5d77b35d1830fa3eULL, 0xc6ba3660bb1f0c0bULL, 0x2ef9f7f09867fd6eULL);
 
     const FunctionData<NT> function_data{
-        .function_selector = 1,  // TODO: deduce this from the contract, somehow.
+        .function_selector =
+            FunctionSelector<NT>{
+                .value = 1,  // TODO: deduce this from the contract, somehow.
+            },
         .is_private = true,
         .is_constructor = false,
     };

circuits/cpp/src/aztec3/circuits/hash.hpp

@@ -2,6 +2,7 @@
 
 #include "aztec3/circuits/abis/function_data.hpp"
 #include "aztec3/circuits/abis/function_leaf_preimage.hpp"
+#include "aztec3/circuits/abis/function_selector.hpp"
 #include "aztec3/circuits/abis/global_variables.hpp"
 #include "aztec3/circuits/abis/new_contract_data.hpp"
 #include "aztec3/circuits/abis/point.hpp"
@@ -16,6 +17,7 @@
 namespace aztec3::circuits {
 
 using abis::FunctionData;
+using abis::FunctionSelector;
 using abis::Point;
 using aztec3::circuits::abis::ContractLeafPreimage;
 using aztec3::circuits::abis::FunctionLeafPreimage;
@@ -303,7 +305,7 @@ void check_membership(Builder& builder,
  * @return NCT::fr
  */
 template <typename NCT> typename NCT::fr function_tree_root_from_siblings(
-    typename NCT::uint32 const& function_selector,
+    FunctionSelector<NCT> const& function_selector,
     typename NCT::boolean const& is_internal,
     typename NCT::boolean const& is_private,
     typename NCT::fr const& vk_hash,

circuits/cpp/src/aztec3/circuits/kernel/private/native_private_kernel_circuit_init.test.cpp

@@ -193,7 +193,9 @@ TEST_F(native_private_kernel_init_tests, contract_deployment_function_data_misma
     auto private_inputs = do_private_call_get_kernel_inputs_init(true, constructor, standard_test_args());
 
     // Modify the function selector in function data.
-    private_inputs.tx_request.function_data.function_selector = numeric::random::get_engine().get_random_uint32();
+    private_inputs.tx_request.function_data.function_selector = FunctionSelector<NT>{
+        .value = numeric::random::get_engine().get_random_uint32(),
+    };
 
     // Invoke the native private kernel circuit
     DummyBuilder builder = DummyBuilder("private_kernel_tests__contract_deployment_function_data_mismatch_fails");

circuits/cpp/src/aztec3/circuits/kernel/private/testing_harness.cpp

@@ -156,7 +156,10 @@ std::pair<PrivateCallData<NT>, ContractDeploymentData<NT>> create_private_call_d
     const Point<NT> msg_sender_pub_key = { .x = 123456789, .y = 123456789 };
 
     FunctionData<NT> const function_data{
-        .function_selector = 1,  // TODO(suyash): deduce this from the contract, somehow.
+        .function_selector =
+            FunctionSelector<NT>{
+                .value = 1,  // TODO: deduce this from the contract, somehow.
+            },
         .is_private = true,
         .is_constructor = is_constructor,
     };

circuits/cpp/src/aztec3/circuits/kernel/public/.test.cpp

@@ -107,7 +107,10 @@ PublicCallStackItem generate_call_stack_item(NT::fr contract_address,
 {
     NT::uint32 count = seed + 1;
     FunctionData<NT> const function_data{
-        .function_selector = count,
+        .function_selector =
+            FunctionSelector<NT>{
+                .value = count,
+            },
         .is_private = false,
         .is_constructor = false,
     };
@@ -264,7 +267,10 @@ PublicKernelInputs<NT> get_kernel_inputs_with_previous_kernel(NT::boolean privat
     const NT::address msg_sender = NT::fr(1);
 
     FunctionData<NT> const function_data{
-        .function_selector = 1,
+        .function_selector =
+            FunctionSelector<NT>{
+                .value = 1,
+            },
         .is_private = false,
         .is_constructor = false,
     };
@@ -640,7 +646,9 @@ TEST(public_kernel_tests, function_selector_must_be_valid)
     DummyBuilder dummyBuilder = DummyBuilder("public_kernel_tests__function_selector_must_be_valid");
     PublicKernelInputs<NT> inputs = get_kernel_inputs_with_previous_kernel(true);
 
-    inputs.public_call.call_stack_item.function_data.function_selector = 0;
+    inputs.public_call.call_stack_item.function_data.function_selector = FunctionSelector<NT>{
+        .value = 0,
+    };
     auto public_inputs = native_public_kernel_circuit_private_previous_kernel(dummyBuilder, inputs);
     ASSERT_TRUE(dummyBuilder.failed());
     ASSERT_EQ(dummyBuilder.get_first_failure().code, CircuitErrorCode::PUBLIC_KERNEL__FUNCTION_SIGNATURE_INVALID);

circuits/cpp/src/aztec3/circuits/kernel/public/common.hpp

@@ -180,7 +180,7 @@ void common_validate_inputs(DummyBuilder& builder, KernelInput const& public_ker
     builder.do_assert(this_call_stack_item.contract_address != 0,
                       "Contract address must be non-zero",
                       CircuitErrorCode::PUBLIC_KERNEL__CONTRACT_ADDRESS_INVALID);
-    builder.do_assert(this_call_stack_item.function_data.function_selector != 0,
+    builder.do_assert(this_call_stack_item.function_data.function_selector.value != 0,
                       "Function signature must be non-zero",
                       CircuitErrorCode::PUBLIC_KERNEL__FUNCTION_SIGNATURE_INVALID);
     builder.do_assert(this_call_stack_item.function_data.is_constructor == false,

yarn-project/acir-simulator/src/acvm/deserialize.ts

@@ -57,15 +57,6 @@ export function frToBoolean(fr: Fr): boolean {
   return buf[buf.length - 1] !== 0;
 }
 
-/**
- * Converts a field to a function selector.
- * @param fr - The field to convert.
- * @returns The function selector.
- */
-export function frToSelector(fr: Fr): Buffer {
-  return fr.toBuffer().slice(-4);
-}
-
 /**
  * Extracts the return fields of a given partial witness.
  * @param acir - The bytecode of the function.