impl mul for int types. fix alloc

gadgets/src/binary/rca.rs

@@ -20,7 +20,7 @@ where
 }
 
 // Generic impl
-impl RippleCarryAdder for &[Boolean] {
+impl RippleCarryAdder for Vec<Boolean> {
     fn add_bits<F: PrimeField, CS: ConstraintSystem<F>>(
         &self,
         mut cs: CS,

gadgets/src/signed_integer/arithmetic/add.rs

@@ -25,13 +25,12 @@ macro_rules! add_int_impl {
         impl Add for $gadget {
             fn add<F: PrimeField, CS: ConstraintSystem<F>>(&self, mut cs: CS, other: &Self) -> Result<Self, IntegerError> {
                 // Compute the maximum value of the sum
-                let mut max_bits = <$gadget as Int>::SIZE;
+                let max_bits = <$gadget as Int>::SIZE;
 
                 // Make some arbitrary bounds for ourselves to avoid overflows
                 // in the scalar field
                 assert!(F::Params::MODULUS_BITS >= max_bits as u32);
 
-
                 // Accumulate the value
                 let result_value = match (self.value, other.value) {
                     (Some(a), Some(b)) => {
@@ -60,7 +59,7 @@ macro_rules! add_int_impl {
                 // we discard the carry since we check for overflow above
                 let _carry = bits.pop();
 
-                // Iterate over each bit_gadget of self and add each bit to
+                // Iterate over each bit_gadget of result and add each bit to
                 // the linear combination
                 let mut coeff = F::one();
                 for bit in bits {
@@ -87,6 +86,7 @@ macro_rules! add_int_impl {
                     coeff.double_in_place();
                 }
 
+
                 // The value of the actual result is modulo 2 ^ $size
                 let modular_value = result_value.map(|v| v as <$gadget as Int>::IntegerType);
 
@@ -102,11 +102,13 @@ macro_rules! add_int_impl {
 
                 // Allocate each bit_gadget of the result
                 let mut coeff = F::one();
-                let mut i = 0;
-                while max_bits != 0 {
+                for i in 0..max_bits {
+                    // get bit value
+                    let mask = 1 << i as <$gadget as Int>::IntegerType;
+
                     // Allocate the bit_gadget
                     let b = AllocatedBit::alloc(cs.ns(|| format!("result bit_gadget {}", i)), || {
-                        result_value.map(|v| (v >> i) & 1 == 1).get()
+                        result_value.map(|v| (v & mask) == mask).get()
                     })?;
 
                     // Subtract this bit_gadget from the linear combination to ensure that the sums
@@ -115,8 +117,6 @@ macro_rules! add_int_impl {
 
                     result_bits.push(b.into());
 
-                    max_bits -= 1;
-                    i += 1;
                     coeff.double_in_place();
                 }
 

gadgets/src/signed_integer/arithmetic/mul.rs

@@ -1,7 +1,24 @@
-use crate::{binary::RippleCarryAdder, errors::IntegerError, sign_extend::SignExtend, Int, Int16, Int32, Int64, Int8};
+use crate::{
+    binary::RippleCarryAdder,
+    errors::IntegerError,
+    sign_extend::SignExtend,
+    Int,
+    Int128,
+    Int16,
+    Int32,
+    Int64,
+    Int8,
+};
 use snarkos_models::{
-    curves::PrimeField,
-    gadgets::{r1cs::ConstraintSystem, utilities::boolean::Boolean},
+    curves::{FpParameters, PrimeField},
+    gadgets::{
+        r1cs::{Assignment, ConstraintSystem, LinearCombination},
+        utilities::{
+            alloc::AllocGadget,
+            boolean::{AllocatedBit, Boolean},
+            select::CondSelectGadget,
+        },
+    },
 };
 
 /// Multiplication for a signed integer gadget
@@ -13,32 +30,165 @@ where
     Self: std::marker::Sized,
 {
     #[must_use]
-    fn mul<F: PrimeField, CS: ConstraintSystem<F>>(&self, cs: CS, other: &Self) -> Result<(), IntegerError>;
+    fn mul<F: PrimeField, CS: ConstraintSystem<F>>(&self, cs: CS, other: &Self) -> Result<Self, IntegerError>;
 }
 
 macro_rules! mul_int_impl {
     ($($gadget: ident)*) => ($(
         impl Mul for $gadget {
-            fn mul<F: PrimeField, CS: ConstraintSystem<F>>(&self, cs: CS, other: &Self) -> Result<(), IntegerError> {
-                // let is_constant = Boolean::constant(Self::result_is_constant(&self, &other));
-                // let constant_result = Self::constant(0 as <$gadget as Int>::)
-                //
-                // let double = <$gadget as Int>::SIZE * 2;
-                //
-                // let a = Boolean::sign_extend(&self.bits, double);
-                // let b = Boolean::sign_extend(&other.bits, double);
-                //
-                // let result =
-                //
-                // for bit in b.iter() {
-                //
-                // }
+            fn mul<F: PrimeField, CS: ConstraintSystem<F>>(&self, mut cs: CS, other: &Self) -> Result<Self, IntegerError> {
+                // Conditionally select constant result
+                let is_constant = Boolean::constant(Self::result_is_constant(&self, &other));
+                let allocated_false = Boolean::from(AllocatedBit::alloc(&mut cs.ns(|| "false"), || Ok(false)).unwrap());
+                let false_bit = Boolean::conditionally_select(
+                    &mut cs.ns(|| "constant_or_allocated_false"),
+                    &is_constant,
+                    &Boolean::constant(false),
+                    &allocated_false,
+                )?;
 
-                Ok(())
+                // Sign extend to double precision
+                let size = <$gadget as Int>::SIZE * 2;
+
+                let a = Boolean::sign_extend(&self.bits, size);
+                let b = Boolean::sign_extend(&other.bits, size);
+
+                let mut bits = vec![false_bit; size];
+
+                // Compute double and add algorithm
+                for (i, b_bit) in b.iter().enumerate() {
+                    // double
+                    let mut a_shifted = vec![false_bit.clone(); i];
+                    a_shifted.append(&mut a.clone());
+                    a_shifted.truncate(size);
+
+                    // conditionally add
+                    let mut to_add = vec![];
+                    for (j, a_bit) in a_shifted.iter().enumerate() {
+                        let selected_bit = Boolean::conditionally_select(
+                            &mut cs.ns(|| format!("select product bit {} {}", i, j)),
+                            b_bit,
+                            a_bit,
+                            &false_bit,
+                        )?;
+
+                        to_add.push(selected_bit);
+                    }
+
+                    bits = bits.add_bits(
+                        &mut cs.ns(|| format!("add bit {}", i)),
+                        &to_add
+                    )?;
+                    let _carry = bits.pop();
+                }
+
+                // Compute the maximum value of the sum
+                let max_bits = <$gadget as Int>::SIZE;
+
+                // Truncate the bits to the size of the integer
+                bits.truncate(max_bits);
+
+                // Make some arbitrary bounds for ourselves to avoid overflows
+                // in the scalar field
+                assert!(F::Params::MODULUS_BITS >= max_bits as u32);
+
+                // Accumulate the value
+                let result_value = match (self.value, other.value) {
+                    (Some(a), Some(b)) => {
+                         // check for addition overflow here
+                         let val = match a.checked_mul(b) {
+                            Some(val) => val,
+                            None => return Err(IntegerError::Overflow)
+                         };
+
+                        Some(val)
+                    },
+                    _ => {
+                        // If any of the operands have unknown value, we won't
+                        // know the value of the result
+                        None
+                    }
+                };
+
+                // This is a linear combination that we will enforce to be zero
+                let mut lc = LinearCombination::zero();
+
+                let mut all_constants = true;
+
+
+                // Iterate over each bit_gadget of result and add each bit to
+                // the linear combination
+                let mut coeff = F::one();
+                for bit in bits {
+                    match bit {
+                        Boolean::Is(ref bit) => {
+                            all_constants = false;
+
+                            // Add the coeff * bit_gadget
+                            lc = lc + (coeff, bit.get_variable());
+                        }
+                        Boolean::Not(ref bit) => {
+                            all_constants = false;
+
+                            // Add coeff * (1 - bit_gadget) = coeff * ONE - coeff * bit_gadget
+                            lc = lc + (coeff, CS::one()) - (coeff, bit.get_variable());
+                        }
+                        Boolean::Constant(bit) => {
+                            if bit {
+                                lc = lc + (coeff, CS::one());
+                            }
+                        }
+                    }
+
+                    coeff.double_in_place();
+                }
+
+                // The value of the actual result is modulo 2 ^ $size
+                let modular_value = result_value.map(|v| v as <$gadget as Int>::IntegerType);
+
+                if all_constants && modular_value.is_some() {
+                    // We can just return a constant, rather than
+                    // unpacking the result into allocated bits.
+
+                    return Ok(Self::constant(modular_value.unwrap()));
+                }
+
+                // Storage area for the resulting bits
+                let mut result_bits = vec![];
+
+                // Allocate each bit_gadget of the result
+                let mut coeff = F::one();
+                for i in 0..max_bits {
+                    // get bit value
+                    let mask = 1 << i as <$gadget as Int>::IntegerType;
+
+                    // Allocate the bit_gadget
+                    let b = AllocatedBit::alloc(cs.ns(|| format!("result bit_gadget {}", i)), || {
+                        result_value.map(|v| (v & mask) == mask).get()
+                    })?;
+
+                    // Subtract this bit_gadget from the linear combination to ensure that the sums
+                    // balance out
+                    lc = lc - (coeff, b.get_variable());
+
+                    result_bits.push(b.into());
+
+                    coeff.double_in_place();
+                }
+
+                // Enforce that the linear combination equals zero
+                cs.enforce(|| "modular multiplication", |lc| lc, |lc| lc, |_| lc);
+
+                // Discard carry bits we don't care about
+                result_bits.truncate(<$gadget as Int>::SIZE);
+
+                Ok(Self {
+                    bits: result_bits,
+                    value: modular_value,
+                })
             }
         }
     )*)
 }
 
-// mul_int_impl!(Int8 Int16 Int32 Int64);
-mul_int_impl!(Int8);
+mul_int_impl!(Int8 Int16 Int32 Int64 Int128);

gadgets/src/signed_integer/arithmetic/twos_complement.rs

@@ -1,6 +1,9 @@
 use crate::{binary::RippleCarryAdder, errors::IntegerError, signed_integer::*};
 
-use snarkos_models::{curves::PrimeField, gadgets::r1cs::ConstraintSystem};
+use snarkos_models::{
+    curves::PrimeField,
+    gadgets::{r1cs::ConstraintSystem, utilities::boolean::Boolean},
+};
 
 /// Inverts the given number and adds 1 to the lsb of the result
 pub trait TwosComplement
@@ -11,6 +14,22 @@ where
     fn twos_comp<F: PrimeField, CS: ConstraintSystem<F>>(&self, cs: CS) -> Result<Self, IntegerError>;
 }
 
+impl TwosComplement for Vec<Boolean> {
+    fn twos_comp<F: PrimeField, CS: ConstraintSystem<F>>(&self, mut cs: CS) -> Result<Self, IntegerError> {
+        // flip all bits
+        let flipped: Self = self.iter().map(|bit| bit.not()).collect();
+
+        // add one
+        let mut one = vec![Boolean::constant(true)];
+        one.append(&mut vec![Boolean::Constant(false); self.len() - 1]);
+
+        let mut bits = flipped.add_bits(cs.ns(|| format!("add one")), &one)?;
+        let _carry = bits.pop(); // we already accounted for overflow above
+
+        Ok(bits)
+    }
+}
+
 macro_rules! twos_comp_int_impl {
     ($($gadget: ident)*) => ($(
         impl TwosComplement for $gadget {

gadgets/src/signed_integer/int_impl.rs

@@ -30,17 +30,17 @@ macro_rules! int_impl {
             pub fn constant(value: $type_) -> Self {
                 let mut bits = Vec::with_capacity($size);
 
-                let mut tmp = value;
+                for i in 0..$size {
+                    // shift value by i
+                    let mask = 1 << i as $type_;
+                    let result = value & mask;
 
-                for _ in 0..$size {
                     // If last bit is one, push one.
-                    if tmp & 1 == 1 {
+                    if result == mask {
                         bits.push(Boolean::constant(true))
                     } else {
                         bits.push(Boolean::constant(false))
                     }
-
-                    tmp >>= 1;
                 }
 
                 Self {

gadgets/src/signed_integer/utilities/mod.rs

@@ -7,3 +7,6 @@ pub use self::select::*;
 
 pub mod sign_extend;
 pub use self::sign_extend::*;
+
+pub mod zero_extend;
+pub use self::zero_extend::*;

gadgets/src/signed_integer/utilities/sign_extend.rs

@@ -13,9 +13,10 @@ where
 impl SignExtend for Boolean {
     fn sign_extend(bits: &[Boolean], length: usize) -> Vec<Self> {
         let msb = bits.last().expect("empty bit list");
-        let mut extension = vec![msb.clone(); length];
-        let mut result = Vec::from(bits);
+        let bits_needed = length - bits.len();
+        let mut extension = vec![msb.clone(); bits_needed];
 
+        let mut result = Vec::from(bits);
         result.append(&mut extension);
 
         result

gadgets/src/signed_integer/utilities/zero_extend.rs

@@ -0,0 +1,23 @@
+use snarkos_models::gadgets::utilities::boolean::Boolean;
+
+/// Zero extends an array of bits to the desired length.
+/// Least significant bit first
+pub trait ZeroExtend
+where
+    Self: std::marker::Sized,
+{
+    #[must_use]
+    fn zero_extend(&self, zero: Boolean, length: usize) -> Self;
+}
+
+impl ZeroExtend for Vec<Boolean> {
+    fn zero_extend(&self, zero: Boolean, length: usize) -> Self {
+        let bits_needed = length - self.len();
+        let mut extension = vec![zero.clone(); bits_needed];
+
+        let mut result = self.clone();
+        result.append(&mut extension);
+
+        result
+    }
+}

gadgets/tests/signed_integer/i8.rs

@@ -10,33 +10,64 @@ use snarkos_models::{
 use rand::{Rng, SeedableRng};
 use rand_xorshift::XorShiftRng;
 
-fn check_all_constant_bits(mut expected: i8, actual: Int8) {
-    for b in actual.bits.iter() {
+fn check_all_constant_bits(expected: i8, actual: Int8) {
+    for (i, b) in actual.bits.iter().enumerate() {
+        // shift value by i
+        let mask = 1 << i as i8;
+        let result = expected & mask;
+
         match b {
             &Boolean::Is(_) => panic!(),
             &Boolean::Not(_) => panic!(),
             &Boolean::Constant(b) => {
-                assert!(b == (expected & 1 == 1));
+                let bit = result == mask;
+                assert_eq!(b, bit);
             }
         }
-
-        expected >>= 1;
     }
 }
 
-fn check_all_allocated_bits(mut expected: i8, actual: Int8) {
-    for b in actual.bits.iter() {
+fn check_all_allocated_bits(expected: i8, actual: Int8) {
+    for (i, b) in actual.bits.iter().enumerate() {
+        // shift value by i
+        let mask = 1 << i as i8;
+        let result = expected & mask;
+
         match b {
             &Boolean::Is(ref b) => {
-                assert!(b.get_value().unwrap() == (expected & 1 == 1));
+                let bit = result == mask;
+                assert_eq!(b.get_value().unwrap(), bit);
             }
             &Boolean::Not(ref b) => {
-                assert!(!b.get_value().unwrap() == (expected & 1 == 1));
+                let bit = result == mask;
+                assert_eq!(!b.get_value().unwrap(), bit);
             }
             &Boolean::Constant(_) => unreachable!(),
         }
+    }
+}
 
-        expected >>= 1;
+#[test]
+fn test_int8_constant_and_alloc() {
+    let mut rng = XorShiftRng::seed_from_u64(1231275789u64);
+
+    for _ in 0..1000 {
+        let mut cs = TestConstraintSystem::<Fr>::new();
+
+        let a: i8 = rng.gen();
+
+        let a_const = Int8::constant(a);
+
+        assert!(a_const.value == Some(a));
+
+        check_all_constant_bits(a, a_const);
+
+        let a_bit = Int8::alloc(cs.ns(|| "a_bit"), || Ok(a)).unwrap();
+
+        assert!(cs.is_satisfied());
+        assert!(a_bit.value == Some(a));
+
+        check_all_allocated_bits(a, a_bit);
     }
 }
 
@@ -178,3 +209,66 @@ fn test_int8_sub() {
         assert!(!cs.is_satisfied());
     }
 }
+
+#[test]
+fn test_int8_mul_constants() {
+    let mut rng = XorShiftRng::seed_from_u64(1231275789u64);
+
+    for _ in 0..1000 {
+        let mut cs = TestConstraintSystem::<Fr>::new();
+
+        let a: i8 = rng.gen();
+        let b: i8 = rng.gen();
+
+        let expected = match a.checked_mul(b) {
+            Some(valid) => valid,
+            None => continue,
+        };
+
+        let a_bit = Int8::constant(a);
+        let b_bit = Int8::constant(b);
+
+        let r = a_bit.mul(cs.ns(|| "multiplication"), &b_bit).unwrap();
+
+        assert!(r.value == Some(expected));
+
+        check_all_constant_bits(expected, r);
+    }
+}
+
+#[test]
+fn test_int8_mul() {
+    let mut rng = XorShiftRng::seed_from_u64(1231275789u64);
+
+    for _ in 0..1000 {
+        let mut cs = TestConstraintSystem::<Fr>::new();
+
+        let a: i8 = rng.gen();
+        let b: i8 = rng.gen();
+
+        let expected = match a.checked_mul(b) {
+            Some(valid) => valid,
+            None => continue,
+        };
+
+        let a_bit = Int8::alloc(cs.ns(|| "a_bit"), || Ok(a)).unwrap();
+        let b_bit = Int8::alloc(cs.ns(|| "b_bit"), || Ok(b)).unwrap();
+
+        let r = a_bit.mul(cs.ns(|| "multiplication"), &b_bit).unwrap();
+
+        assert!(cs.is_satisfied());
+
+        assert!(r.value == Some(expected));
+
+        check_all_allocated_bits(expected, r);
+
+        // Flip a bit_gadget and see if the multiplication constraint still works
+        if cs.get("multiplication/result bit_gadget 0/boolean").is_zero() {
+            cs.set("multiplication/result bit_gadget 0/boolean", Fr::one());
+        } else {
+            cs.set("multiplication/result bit_gadget 0/boolean", Fr::zero());
+        }
+
+        assert!(!cs.is_satisfied());
+    }
+}