Add function to export witnesses in gnark-byte format (12 byte header)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sunspot_wasm"
-version = "2.0.1"
+version = "2.1.0"
 edition = "2024"
 
 [lib]

js/README.md

@@ -111,7 +111,7 @@ import { init, prove } from '@reilabs/sunspot_js/sisd-st'; // scalar fallback, s
 - `class ZKey(pk, r1cs)` — bundles a proving key and R1CS.
   - `ZKey.from(pkResponse, r1csResponse)` — load both from `fetch()` responses.
   - `ZKey.fromUnchecked(pkResponse, r1csResponse)` — same but skips on-curve checks on the PK. Only safe for trusted keys.
-- `class Witness(circuit, witnessStackBytes)` — build the gnark-ordered partial witness from a Noir `CompiledCircuit` and the `Noir#execute(...).witness` witness map. Exposes `privateBytes()` and `publicBytes()` (concatenated 32-byte big-endian limbs).
+- `class Witness(circuit, witnessStackBytes)` — gnark-ordered partial witness. Exposes `publicBytes()` / `privateBytes()` (concatenated 32-byte BE limbs), and `gnarkFormatPublicBytes()` (public witness in gnark `MarshalBinary` / `.pw` format — the form Sunspot-produced verifiers expect).
 - `class Proof` — `asBytes()`, `arBytes()`, `bsBytes()`, `krsBytes()`, `commitmentsBytes()`, `commitmentPokBytes()`, `nbCommitments()`, `isValid()`.
 - `prove(input, circuit, zkey): Promise<Proof>` — witness-gen + prove in one call.
 

js/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@reilabs/sunspot_js",
-  "version": "2.0.1",
+  "version": "2.1.0",
   "description": "Groth16 prover for Noir circuits in browser.",
   "license": "Apache-2.0",
   "repository": {

js/src/index.ts

@@ -174,6 +174,8 @@ export class Witness {
   publicBytes(): Uint8Array { return this.inner.public_bytes(); }
   /** Concatenated 32-byte big-endian limbs of the private witness slots. */
   privateBytes(): Uint8Array { return this.inner.private_bytes(); }
+  /** Public witness in gnark's `MarshalBinary` format. */
+  gnarkFormatPublicBytes(): Uint8Array { return this.inner.gnark_format_public_bytes(); }
   free(): void { this.inner.free(); }
   [Symbol.dispose](): void { this.inner[Symbol.dispose](); }
 }

src/wasm.rs

@@ -48,6 +48,20 @@ impl Witness {
     pub fn private_bytes(&self) -> Vec<u8> {
         flatten(&self.0.private)
     }
+
+    /// Public witness in gnark's `MarshalBinary` format:
+    ///  12-byte big-endian header followed by the concatenated
+    ///  32-byte big-endian public entries.
+    pub fn gnark_format_public_bytes(&self) -> Vec<u8> {
+        let body = self.public_bytes();
+        let n = self.0.public.len() as u32;
+        let mut out = Vec::with_capacity(12 + body.len());
+        out.extend_from_slice(&n.to_be_bytes());
+        out.extend_from_slice(&0u32.to_be_bytes());
+        out.extend_from_slice(&n.to_be_bytes());
+        out.extend_from_slice(&body);
+        out
+    }
 }
 
 fn flatten(elems: &[acir::FieldElement]) -> Vec<u8> {