Ensure Circom 1 tests pass with experimental Circom 2 support (#18)

* All tests pass under circom-2 feature flag

- Check for version in WASM, default to version 1
- Include Circom1 when Circom 2 feature flag is enabled

Currently a lot of code duplication. Once Circom-2 is more stable and
proven to work in the wild, feature flag can be removed.

* Separate Circom 1 and Circom2 witness calculation

* Cleanup

* WitnessCalculator helpers for Circom 1 and 2

Also make helper fn private

* Move comment

* Fix expression return

* cargo fmt

* Add cargo test circom-2 to ci

.github/workflows/ci.yml

@@ -44,6 +44,11 @@ jobs:
             export PATH=$HOME/bin:$PATH
             cargo test
 
+      - name: cargo test circom 2 feature flag
+        run: |
+            export PATH=$HOME/bin:$PATH
+            cargo test --features circom-2
+
   lint:
     runs-on: ubuntu-latest
     steps:

Cargo.lock

@@ -97,6 +97,7 @@ dependencies = [
  "fnv",
  "hex",
  "hex-literal",
+ "num",
  "num-bigint",
  "num-traits",
  "serde_json",
@@ -1950,6 +1951,20 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "num"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43db66d1170d347f9a065114077f7dccb00c1b9478c89384490a3425279a4606"
+dependencies = [
+ "num-bigint",
+ "num-complex",
+ "num-integer",
+ "num-iter",
+ "num-rational",
+ "num-traits",
+]
+
 [[package]]
 name = "num-bigint"
 version = "0.4.0"
@@ -1962,6 +1977,15 @@ dependencies = [
  "rand",
 ]
 
+[[package]]
+name = "num-complex"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26873667bbbb7c5182d4a37c1add32cdf09f841af72da53318fdb81543c15085"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "num-integer"
 version = "0.1.44"
@@ -1972,6 +1996,29 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "num-iter"
+version = "0.1.42"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2021c8337a54d21aca0d59a92577a029af9431cb59b909b03252b9c164fad59"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d41702bd167c2df5520b384281bc111a4b5efcf7fbc4c9c222c815b07e0a6a6a"
+dependencies = [
+ "autocfg",
+ "num-bigint",
+ "num-integer",
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.14"

src/witness/circom.rs

@@ -19,6 +19,8 @@ pub trait CircomBase {
     ) -> Result<()>;
     fn set_signal(&self, c_idx: i32, component: i32, signal: i32, p_val: i32) -> Result<()>;
     fn get_i32(&self, name: &str) -> Result<i32>;
+    // Only exists natively in Circom2, hardcoded for Circom
+    fn get_version(&self) -> Result<i32>;
 }
 
 pub trait Circom {
@@ -27,7 +29,6 @@ pub trait Circom {
 }
 
 pub trait Circom2 {
-    fn get_version(&self) -> Result<i32>;
     fn get_field_num_len32(&self) -> Result<i32>;
     fn get_raw_prime(&self) -> Result<()>;
     fn read_shared_rw_memory(&self, i: i32) -> Result<i32>;
@@ -37,7 +38,6 @@ pub trait Circom2 {
     fn get_witness_size(&self) -> Result<i32>;
 }
 
-#[cfg(not(feature = "circom-2"))]
 impl Circom for Wasm {
     fn get_fr_len(&self) -> Result<i32> {
         self.get_i32("getFrLen")
@@ -50,10 +50,6 @@ impl Circom for Wasm {
 
 #[cfg(feature = "circom-2")]
 impl Circom2 for Wasm {
-    fn get_version(&self) -> Result<i32> {
-        self.get_i32("getVersion")
-    }
-
     fn get_field_num_len32(&self) -> Result<i32> {
         self.get_i32("getFieldNumLen32")
     }
@@ -142,6 +138,14 @@ impl CircomBase for Wasm {
         Ok(())
     }
 
+    // Default to version 1 if it isn't explicitly defined
+    fn get_version(&self) -> Result<i32> {
+        match self.0.exports.get_function("getVersion") {
+            Ok(func) => Ok(func.call(&[])?[0].unwrap_i32()),
+            Err(_) => Ok(1),
+        }
+    }
+
     fn get_i32(&self, name: &str) -> Result<i32> {
         let func = self.func(name);
         let result = func.call(&[])?;

src/witness/mod.rs

@@ -10,7 +10,6 @@ pub(super) use circom::{CircomBase, Wasm};
 #[cfg(feature = "circom-2")]
 pub(super) use circom::Circom2;
 
-#[cfg(not(feature = "circom-2"))]
 pub(super) use circom::Circom;
 
 use fnv::FnvHasher;

src/witness/witness_calculator.rs

@@ -11,7 +11,6 @@ use num::ToPrimitive;
 #[cfg(feature = "circom-2")]
 use super::Circom2;
 
-#[cfg(not(feature = "circom-2"))]
 use super::Circom;
 
 #[derive(Clone, Debug)]
@@ -19,6 +18,7 @@ pub struct WitnessCalculator {
     pub instance: Wasm,
     pub memory: SafeMemory,
     pub n64: i32,
+    pub circom_version: i32,
 }
 
 // Error type to signal end of execution.
@@ -77,9 +77,16 @@ impl WitnessCalculator {
         };
         let instance = Wasm::new(Instance::new(&module, &import_object)?);
 
-        cfg_if::cfg_if! {
+        let version;
-            if #[cfg(feature = "circom-2")] {
+
-                //let version = instance.get_version()?;
+        match instance.get_version() {
+            Ok(v) => version = v,
+            Err(_) => version = 1,
+        }
+
+        // Circom 2 feature flag with version 2
+        #[cfg(feature = "circom-2")]
+        fn new_circom2(instance: Wasm, memory: Memory, version: i32) -> Result<WitnessCalculator> {
             let n32 = instance.get_field_num_len32()?;
             let mut safe_memory = SafeMemory::new(memory, n32 as usize, BigInt::zero());
             instance.get_raw_prime()?;
@@ -89,15 +96,6 @@ impl WitnessCalculator {
                 arr[(n32 as usize) - (i as usize) - 1] = res;
             }
             let prime = from_array32(arr);
-            } else {
-                // Fallback to Circom 1 behavior
-                //version = 1;
-                let n32 = (instance.get_fr_len()? >> 2) - 2;
-                let mut safe_memory = SafeMemory::new(memory, n32 as usize, BigInt::zero());
-                let ptr = instance.get_ptr_raw_prime()?;
-                let prime = safe_memory.read_big(ptr as usize, n32 as usize)?;
-            }
-        }
 
             let n64 = ((prime.bits() - 1) / 64 + 1) as i32;
             safe_memory.prime = prime;
@@ -106,9 +104,48 @@ impl WitnessCalculator {
                 instance,
                 memory: safe_memory,
                 n64,
+                circom_version: version,
             })
         }
 
+        fn new_circom1(instance: Wasm, memory: Memory, version: i32) -> Result<WitnessCalculator> {
+            // Fallback to Circom 1 behavior
+            let n32 = (instance.get_fr_len()? >> 2) - 2;
+            let mut safe_memory = SafeMemory::new(memory, n32 as usize, BigInt::zero());
+            let ptr = instance.get_ptr_raw_prime()?;
+            let prime = safe_memory.read_big(ptr as usize, n32 as usize)?;
+
+            let n64 = ((prime.bits() - 1) / 64 + 1) as i32;
+            safe_memory.prime = prime;
+
+            Ok(WitnessCalculator {
+                instance,
+                memory: safe_memory,
+                n64,
+                circom_version: version,
+            })
+        }
+
+        // Three possibilities:
+        // a) Circom 2 feature flag enabled, WASM runtime version 2
+        // b) Circom 2 feature flag enabled, WASM runtime version 1
+        // c) Circom 1 default behavior
+        //
+        // Once Circom 2 support is more stable, feature flag can be removed
+
+        cfg_if::cfg_if! {
+            if #[cfg(feature = "circom-2")] {
+                match version {
+                    2 => new_circom2(instance, memory, version),
+                    1 => new_circom1(instance, memory, version),
+                    _ => panic!("Unknown Circom version")
+                }
+            } else {
+                new_circom1(instance, memory, version)
+            }
+        }
+    }
+
     pub fn calculate_witness<I: IntoIterator<Item = (String, Vec<BigInt>)>>(
         &mut self,
         inputs: I,
@@ -118,28 +155,33 @@ impl WitnessCalculator {
 
         cfg_if::cfg_if! {
             if #[cfg(feature = "circom-2")] {
-                let n32 = self.instance.get_field_num_len32()?;
+                match self.circom_version {
+                    2 => self.calculate_witness_circom2(inputs, sanity_check),
+                    1 => self.calculate_witness_circom1(inputs, sanity_check),
+                    _ => panic!("Unknown Circom version")
+                }
             } else {
+                self.calculate_witness_circom1(inputs, sanity_check)
+            }
+        }
+    }
+
+    // Circom 1 default behavior
+    fn calculate_witness_circom1<I: IntoIterator<Item = (String, Vec<BigInt>)>>(
+        &mut self,
+        inputs: I,
+        sanity_check: bool,
+    ) -> Result<Vec<BigInt>> {
+        self.instance.init(sanity_check)?;
+
         let old_mem_free_pos = self.memory.free_pos();
         let p_sig_offset = self.memory.alloc_u32();
         let p_fr = self.memory.alloc_fr();
-            }
-        }
 
         // allocate the inputs
         for (name, values) in inputs.into_iter() {
             let (msb, lsb) = fnv(&name);
 
-            cfg_if::cfg_if! {
-                if #[cfg(feature = "circom-2")] {
-                    for (i, value) in values.into_iter().enumerate() {
-                        let f_arr = to_array32(&value, n32 as usize);
-                        for j in 0..n32 {
-                            self.instance.write_shared_rw_memory(j as i32, f_arr[(n32 as usize) - 1 - (j as usize)])?;
-                        }
-                        self.instance.set_input_signal(msb as i32, lsb as i32, i as i32)?;
-                    }
-                } else {
             self.instance
                 .get_signal_offset32(p_sig_offset, 0, msb, lsb)?;
 
@@ -151,24 +193,9 @@ impl WitnessCalculator {
                     .set_signal(0, 0, (sig_offset + i) as i32, p_fr as i32)?;
             }
         }
-            }
-        }
 
         let mut w = Vec::new();
 
-        cfg_if::cfg_if! {
-            if #[cfg(feature = "circom-2")] {
-                let witness_size = self.instance.get_witness_size()?;
-                for i in 0..witness_size {
-                    self.instance.get_witness(i)?;
-                    let mut arr = vec![0; n32 as usize];
-                    for j in 0..n32 {
-                        arr[(n32 as usize) - 1- (j as usize)] = self.instance.read_shared_rw_memory(j)?;
-                    }
-                    w.push(from_array32(arr));
-                }
-
-            } else {
         let n_vars = self.instance.get_n_vars()?;
         for i in 0..n_vars {
             let ptr = self.instance.get_ptr_witness(i)? as usize;
@@ -177,7 +204,48 @@ impl WitnessCalculator {
         }
 
         self.memory.set_free_pos(old_mem_free_pos);
+
+        Ok(w)
     }
+
+    // Circom 2 feature flag with version 2
+    #[cfg(feature = "circom-2")]
+    fn calculate_witness_circom2<I: IntoIterator<Item = (String, Vec<BigInt>)>>(
+        &mut self,
+        inputs: I,
+        sanity_check: bool,
+    ) -> Result<Vec<BigInt>> {
+        self.instance.init(sanity_check)?;
+
+        let n32 = self.instance.get_field_num_len32()?;
+
+        // allocate the inputs
+        for (name, values) in inputs.into_iter() {
+            let (msb, lsb) = fnv(&name);
+
+            for (i, value) in values.into_iter().enumerate() {
+                let f_arr = to_array32(&value, n32 as usize);
+                for j in 0..n32 {
+                    self.instance.write_shared_rw_memory(
+                        j as i32,
+                        f_arr[(n32 as usize) - 1 - (j as usize)],
+                    )?;
+                }
+                self.instance
+                    .set_input_signal(msb as i32, lsb as i32, i as i32)?;
+            }
+        }
+
+        let mut w = Vec::new();
+
+        let witness_size = self.instance.get_witness_size()?;
+        for i in 0..witness_size {
+            self.instance.get_witness(i)?;
+            let mut arr = vec![0; n32 as usize];
+            for j in 0..n32 {
+                arr[(n32 as usize) - 1 - (j as usize)] = self.instance.read_shared_rw_memory(j)?;
+            }
+            w.push(from_array32(arr));
         }
 
         Ok(w)