[fix] used div_rem when using / and % in same value (keep-starknet-st…

…range#219)

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- [x] issue keep-starknet-strange#206
- [x] follows contribution
[guide](https://github.com/keep-starknet-strange/shinigami/blob/main/CONTRIBUTING.md)
- [x] code change includes tests

<!-- PR description below -->
This PR will add the usage of div_rem when using / and % in the same
value.

*Pending:* in utils.cairo file, the ``` fast_power ``` function is
giving problems for using div_rem.

Co-authored-by: Brandon Roberts <brandonjroberts22@gmail.com>

packages/engine/src/signature/signature.cairo

@@ -213,9 +213,10 @@ pub fn check_signature_encoding<T, +Drop<T>>(
         let s_value = u256_from_byte_array_with_offset(sig_bytes, s_offset, 32);
         let mut half_order = Secp256Trait::<Secp256k1Point>::get_curve_size();
 
-        let carry = half_order.high % 2;
+        let (half_order_high_upper, half_order_high_lower) = DivRem::div_rem(half_order.high, 2);
+        let carry = half_order_high_lower;
         half_order.low = (half_order.low / 2) + (carry * (constants::MAX_U128 / 2 + 1));
-        half_order.high /= 2;
+        half_order.high = half_order_high_upper;
 
         if s_value > half_order {
             return Result::Err('sig not canonical high S value');

packages/utils/src/byte_array.cairo

@@ -73,8 +73,9 @@ pub fn felt252_to_byte_array(value: felt252) -> ByteArray {
     let mut byte_array = "";
     let mut valueU256: u256 = value.into();
     while valueU256 != 0 {
-        byte_array.append_byte((valueU256 % byte_shift).try_into().unwrap());
-        valueU256 /= byte_shift;
+        let (value_upper, value_lower) = DivRem::div_rem(valueU256, byte_shift);
+        byte_array.append_byte(value_lower.try_into().unwrap());
+        valueU256 = value_upper;
     };
     byte_array.rev()
 }

packages/utils/src/bytecode.cairo

@@ -43,8 +43,7 @@ pub fn bytecode_to_hex(bytecode: @ByteArray) -> ByteArray {
         return "0x00";
     }
     while i != bytecode_len {
-        let upper_half_byte = bytecode[i] / half_byte_shift;
-        let lower_half_byte = bytecode[i] % half_byte_shift;
+        let (upper_half_byte, lower_half_byte) = DivRem::div_rem(bytecode[i], half_byte_shift);
         let upper_half: u8 = if upper_half_byte < 10 {
             upper_half_byte + zero
         } else {

packages/utils/src/hex.cairo

@@ -1,9 +1,8 @@
 pub fn int_to_hex(value: u8) -> felt252 {
     let half_byte_shift = 16;
     let byte_shift = 256;
-    let upper_half_value = value / half_byte_shift;
-    let lower_half_value = value % half_byte_shift;
 
+    let (upper_half_value, lower_half_value) = DivRem::div_rem(value, half_byte_shift);
     let upper_half: u8 = if upper_half_value < 10 {
         upper_half_value + '0'
     } else {