feat: read number of public inputs from vkey file

packages/rust-verifier/src/main.rs

@@ -6,7 +6,10 @@ use std::{
 
 use ark_serialize::{CanonicalSerialize, Write};
 use clap::{Parser, Subcommand};
-use utils::verifier_utils::{GrothBnProof, GrothBnVkey, JsonDecoder, PublicInputs};
+use serde::Deserialize;
+use utils::verifier_utils::{
+    GrothBnProof, GrothBnVkey, JsonDecoder, PublicInputs, PublicInputsCount,
+};
 
 #[derive(Parser)]
 #[command(name = "rust verifier")]
@@ -48,14 +51,21 @@ fn main() {
         } => {
             println!("Generating verifier with verifying key: {}", verifying_key);
             let vkey = GrothBnVkey::from_json_file(verifying_key);
+            let public_inputs_count = PublicInputsCount::from_json_file(verifying_key);
+
             let mut serialized_vkey = Vec::new();
             let writer = BufWriter::new(&mut serialized_vkey);
             vkey.serialize_compressed(writer).unwrap();
 
             let template = include_str!("verifier_template.rs");
 
-            let verifier_content =
-                template.replace("[COMPRESSED_VKEY]", &format!("{:?}", &serialized_vkey));
+            let verifier_content = template
+                .replace("[COMPRESSED_VKEY]", &format!("{:?}", &serialized_vkey))
+                .replace(
+                    "PUBLIC_INPUTS_COUNT",
+                    public_inputs_count.nPublic.to_string().as_str(),
+                );
+
             let formatted_content =
                 format_rust_code(&verifier_content).expect("Failed to format the code");
 

packages/rust-verifier/src/verifier_template.rs

@@ -18,11 +18,12 @@ pub fn verify(proof: &[u8], public_inputs: &[u8]) -> bool {
     let vk = VerifyingKey::<Bn254>::deserialize_compressed_unchecked([COMPRESSED_VKEY].as_slice())
         .unwrap();
 
-    let public_inputs = <[Fp<MontBackend<FrConfig, 4>, 4>; 3]>::deserialize_with_mode(
-        &public_inputs[..],
-        Compress::Yes,
-        Validate::Yes,
-    );
+    let public_inputs =
+        <[Fp<MontBackend<FrConfig, 4>, 4>; PUBLIC_INPUTS_COUNT]>::deserialize_with_mode(
+            &public_inputs[..],
+            Compress::Yes,
+            Validate::Yes,
+        );
 
     let public_inputs = match public_inputs {
         Ok(inputs) => inputs,

packages/rust-verifier/src/verifier_utils.rs

@@ -43,6 +43,12 @@ pub struct PublicInputs<const N: usize> {
     pub inputs: [GrothFp; N],
 }
 
+// helper struct for deserializing public inputs count
+#[derive(Deserialize)]
+pub struct PublicInputsCount {
+    pub nPublic: usize,
+}
+
 pub trait JsonDecoder {
     fn from_json(json: &str) -> Self;
     fn from_json_file(file_path: &str) -> Self
@@ -144,6 +150,12 @@ impl JsonDecoder for GrothBnVkey {
     }
 }
 
+impl JsonDecoder for PublicInputsCount {
+    fn from_json(json: &str) -> Self {
+        serde_json::from_str(json).unwrap()
+    }
+}
+
 impl<const N: usize> JsonDecoder for PublicInputs<N> {
     fn from_json(json: &str) -> Self {
         let inputs: Vec<String> = serde_json::from_str(json).unwrap();