From 36f61bb3f2542125bacd2a5434fea3f88f149193 Mon Sep 17 00:00:00 2001
From: mohab metwally <mohab-metwally@riseup.net>
Date: Thu, 12 Jan 2023 01:07:34 +0200
Subject: [PATCH] [consensus/utils] fixed bug in fbig2ibig, added extra test
 case

---
 src/consensus/utils.rs | 70 +++++++++++++++++++++++++-----------------
 1 file changed, 42 insertions(+), 28 deletions(-)

diff --git a/src/consensus/utils.rs b/src/consensus/utils.rs
index cf868e25b..cfdc2ee00 100644
--- a/src/consensus/utils.rs
+++ b/src/consensus/utils.rs
@@ -19,6 +19,9 @@
 use darkfi_sdk::pasta::pallas;
 use dashu::integer::{IBig, Sign};
 use log::debug;
+use dashu::integer::UBig;
+use darkfi_sdk::pasta::group::ff::PrimeField;
+use crate::consensus::{constants::RADIX_BITS};
 
 use super::Float10;
 
@@ -26,27 +29,18 @@ pub fn fbig2ibig(f: Float10) -> IBig {
     let rad = IBig::try_from(10).unwrap();
     let sig = f.repr().significand();
     let exp = f.repr().exponent();
-    let val: IBig = if exp >= 0 { sig.clone() * rad.pow(exp as usize) } else { sig.clone() };
-    debug!(target: "consensus::utils", "fbig2ibig (f): {}", f);
-    debug!(target: "consensus::utils", "fbig2ibig (i): {}", val);
+
+    let val: IBig = if exp >= 0 {
+        sig.clone() * rad.pow(exp as usize)
+    } else {
+        sig.clone() / rad.pow(exp.abs() as usize)
+    };
+
     val
 }
-/*
-pub fn base2ibig(base: pallas::Base) -> IBig {
-    //
-    let byts: [u8; 32] = base.to_repr();
-    let words: [u64; 4] = [
-        u64::from_le_bytes(byts[0..8].try_into().expect("")),
-        u64::from_le_bytes(byts[8..16].try_into().expect("")),
-        u64::from_le_bytes(byts[16..24].try_into().expect("")),
-        u64::from_le_bytes(byts[24..32].try_into().expect("")),
-    ];
-    let uparts = UBig::from_words(&words);
-    //TODO both y, and t are positive, but workout the sign for general use
-    let ibig = IBig::from_parts(Sign::Positive, uparts);
-    ibig
-}
-*/
+
+/// note! nagative values in pallas field won't wraps, and won't
+/// convert back to same value.
 pub fn fbig2base(f: Float10) -> pallas::Base {
     debug!(target: "consensus::utils", "fbig -> base (f): {}", f);
     let val: IBig = fbig2ibig(f);
@@ -59,11 +53,28 @@ pub fn fbig2base(f: Float10) -> pallas::Base {
     }
 }
 
+/// note! only support positive conversion, and zero.
+/// used for testing purpose on non-negative values at the moment.
+pub fn base2ibig(base: pallas::Base) -> IBig {
+    //
+    let byts: [u8; 32] = base.to_repr();
+    let words: [u64; 4] = [
+        u64::from_le_bytes(byts[0..8].try_into().expect("")),
+        u64::from_le_bytes(byts[8..16].try_into().expect("")),
+        u64::from_le_bytes(byts[16..24].try_into().expect("")),
+        u64::from_le_bytes(byts[24..32].try_into().expect("")),
+    ];
+    let uparts = UBig::from_words(&words);
+    let ibig = IBig::from_parts(Sign::Positive, uparts);
+    ibig
+}
 #[cfg(test)]
 mod tests {
     use dashu::integer::IBig;
 
-    use crate::consensus::{types::Float10, utils::fbig2ibig};
+    use darkfi_sdk::pasta::{pallas, group::ff::PrimeField};
+    use crate::consensus::{constants::RADIX_BITS, types::Float10, utils::{fbig2ibig, fbig2base, base2ibig}};
+
 
     #[test]
     fn dashu_fbig2ibig() {
@@ -73,20 +84,23 @@ mod tests {
         assert_eq!(i, sig);
     }
 
-    /*
     #[test]
     fn dashu_test_base2ibig() {
         //
-        let fbig: Float10 = Float10::from_str_native(
-            "28948022309329048855892746252171976963363056481941560715954676764349967630337",
-        )
-        .unwrap()
-        .with_precision(RADIX_BITS)
-        .value();
+        let fbig: Float10 = Float10::from_str_native("289480223093290488558927462521719769633630564819415607159546767643499676303").unwrap().with_precision(RADIX_BITS).value();
         let ibig = fbig2ibig(fbig.clone());
         let res_base: pallas::Base = fbig2base(fbig.clone());
         let res_ibig: IBig = base2ibig(res_base);
         assert_eq!(res_ibig, ibig);
     }
-    */
+
+    #[test]
+    fn dashu_test2_base2ibig() {
+        //assert that field wrapping for negative values won't hold during conversions.
+        let fbig: Float10 = Float10::from_str_native("-20065240046497827215558476051577517633529246907153511707181011345840062564.87").unwrap().with_precision(RADIX_BITS).value();
+        let ibig = fbig2ibig(fbig.clone());
+        let res_base: pallas::Base = fbig2base(fbig.clone());
+        let res_ibig: IBig = base2ibig(res_base);
+        assert_ne!(res_ibig, ibig);
+    }
 }