WIP: Lightweight version of `ark-circom` (#41)

* remove ethers-core

* test

* return ethereum and add a feature

* lint fixes

---------

Co-authored-by: s1fr0 <28568419+s1fr0@users.noreply.github.com>
Co-authored-by: tyshkor <tyshko1@gmail.com>

Cargo.toml

@@ -26,11 +26,12 @@ hex = "0.4.3"
 byteorder = "1.4.3"
 
 # ethereum compat
-ethers-core = { git = "https://github.com/gakonst/ethers-rs", default-features = false }
+ethers-core = { git = "https://github.com/gakonst/ethers-rs", default-features = false, optional = true }
+ethers = { git = "https://github.com/gakonst/ethers-rs", features = ["abigen"], optional = true }
 
 # error handling
 thiserror = "1.0.26"
-color-eyre = "0.5"
+color-eyre = "0.6.1"
 criterion = "0.3.4"
 
 cfg-if = "1.0"
@@ -39,7 +40,6 @@ cfg-if = "1.0"
 hex-literal = "0.2.1"
 tokio = { version = "1.7.1", features = ["macros"] }
 serde_json = "1.0.64"
-ethers = { git = "https://github.com/gakonst/ethers-rs", features = ["abigen"] }
 
 [[bench]]
 name = "groth16"
@@ -48,3 +48,5 @@ harness = false
 [features]
 bench-complex-all = []
 circom-2 = []
+full = ["ethers", "ethers-core"]
+default = ["full"]

src/circom/r1cs_reader.rs

@@ -73,7 +73,7 @@ impl R1CSFile {
         for _ in 0..num_sections {
             let sec_type = reader.read_u32::<LittleEndian>()?;
             let sec_size = reader.read_u64::<LittleEndian>()?;
-            let offset = reader.seek(SeekFrom::Current(0))?;
+            let offset = reader.stream_position()?;
             sec_offsets.insert(sec_type, offset);
             sec_sizes.insert(sec_type, sec_size);
             reader.seek(SeekFrom::Current(sec_size as i64))?;

src/lib.rs

@@ -7,6 +7,7 @@ pub use witness::WitnessCalculator;
 pub mod circom;
 pub use circom::{CircomBuilder, CircomCircuit, CircomConfig, CircomReduction};
 
+#[cfg(feature = "full")]
 pub mod ethereum;
 
 mod zkey;

src/witness/witness_calculator.rs

@@ -313,8 +313,7 @@ mod runtime {
             // NOTE: We can also get more information why it is failing, see p2str etc here:
             // https://github.com/iden3/circom_runtime/blob/master/js/witness_calculator.js#L52-L64
             println!(
-                "runtime error, exiting early: {0} {1} {2} {3} {4} {5}",
-                a, b, c, d, e, f
+                "runtime error, exiting early: {a} {b} {c} {d} {e} {f}",
             );
             Err(RuntimeError::user(Box::new(ExitCode(1))))
         }