From 9c4ea7ae26a0d148014cd7ef0412325ba38fc7de Mon Sep 17 00:00:00 2001
From: Adam Wick <awick@uhsure.com>
Date: Fri, 23 Mar 2018 22:12:34 -0700
Subject: [PATCH] Start working variable-length numbers.

---
 src/cryptonum/conversions.rs |  29 ++++++
 src/cryptonum/mod.rs         | 165 +++++++++++++++++++++++++++++++++++
 2 files changed, 194 insertions(+)
 create mode 100644 src/cryptonum/conversions.rs
 create mode 100644 src/cryptonum/mod.rs

diff --git a/src/cryptonum/conversions.rs b/src/cryptonum/conversions.rs
new file mode 100644
index 0000000..ea579c8
--- /dev/null
+++ b/src/cryptonum/conversions.rs
@@ -0,0 +1,29 @@
+macro_rules! define_from
+{
+    ($type: ident, $base: ident) => {
+        impl From<$base> for $type {
+            fn from(x: $base) -> $type {
+                if x == 0 {
+                    UCN{ contents: Vec::new() }
+                } else {
+                    UCN{ contents: vec![x as u64] }
+                }
+            }
+        }
+    }
+}
+
+macro_rules! define_into
+{
+    ($type: ident, $base: ident) => {
+        impl Into<$base> for $type {
+            fn into(self) -> $base {
+                if self.contents.is_empty() {
+                    0
+                } else {
+                    self.contents[0] as $base
+                }
+            }
+        }
+    }
+}
diff --git a/src/cryptonum/mod.rs b/src/cryptonum/mod.rs
new file mode 100644
index 0000000..389e7b9
--- /dev/null
+++ b/src/cryptonum/mod.rs
@@ -0,0 +1,165 @@
+#[macro_use]
+mod conversions;
+
+use num::{BigUint,ToPrimitive,Zero};
+use std::cmp::Ordering;
+
+/// In case you were wondering, it stands for "Unsigned Crypto Num".
+#[derive(Clone,Debug,PartialEq,Eq)]
+pub struct UCN {
+    contents: Vec<u64>
+}
+
+//------------------------------------------------------------------------------
+//
+//  Conversions to/from crypto nums.
+//
+//------------------------------------------------------------------------------
+
+define_from!(UCN, u8);
+define_from!(UCN, u16);
+define_from!(UCN, u32);
+define_from!(UCN, u64);
+define_into!(UCN, u8);
+define_into!(UCN, u16);
+define_into!(UCN, u32);
+define_into!(UCN, u64);
+
+impl From<BigUint> for UCN {
+    fn from(mut x: BigUint) -> UCN {
+        let mut dest = Vec::new();
+        let mask = BigUint::from(0xFFFFFFFFFFFFFFFF as u64);
+
+        while !x.is_zero() {
+            match (&x & &mask).to_u64() {
+                None =>
+                    panic!("Can't use BigUint in From<BigUint>"),
+                Some(val) =>
+                    dest.push(val)
+            }
+            x >>= 64;
+        }
+
+        UCN{ contents: dest }
+    }
+}
+
+impl Into<BigUint> for UCN {
+    fn into(self) -> BigUint {
+        let mut result = BigUint::zero();
+
+        for part in self.contents.iter().rev() {
+            result <<= 64;
+            result += BigUint::from(*part);
+        }
+
+        result
+    }
+}
+
+//------------------------------------------------------------------------------
+//
+//  Comparisons
+//
+//------------------------------------------------------------------------------
+
+impl PartialOrd for UCN {
+    fn partial_cmp(&self, other: &UCN) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for UCN {
+    fn cmp(&self, other: &UCN) -> Ordering {
+        let mut iter_left  = self.contents.iter();
+        let mut iter_right = other.contents.iter();
+
+        loop {
+            match (iter_left.next(), iter_right.next()) {
+                (None,    None)    => return Ordering::Equal,
+                (Some(_), None)    => return Ordering::Greater,
+                (None,    Some(_)) => return Ordering::Less,
+                (Some(x), Some(y)) =>
+                    match x.cmp(y) {
+                        Ordering::Equal => continue,
+                        result          => return result
+                    }
+            }
+        }
+    }
+}
+
+
+//------------------------------------------------------------------------------
+//
+//  Tests!
+//
+//------------------------------------------------------------------------------
+
+#[cfg(test)]
+mod test {
+    use quickcheck::{Arbitrary,Gen};
+    use super::*;
+
+    #[test]
+    #[allow(overflowing_literals)]
+    fn test_builders() {
+        assert_eq!(UCN{ contents: vec![] },
+                   UCN::from(0 as u8));
+        assert_eq!(UCN{ contents: vec![0x7F] },
+                   UCN::from(0x7F as u8));
+        assert_eq!(UCN{ contents: vec![0x7F7F] },
+                   UCN::from(0x7F7F as u16));
+        assert_eq!(UCN{ contents: vec![0xCA5CADE5] },
+                   UCN::from(0xCA5CADE5 as u32));
+        assert_eq!(UCN{ contents: vec![0xFFFFFFFFFFFFFFFF] },
+                   UCN::from(0xFFFFFFFFFFFFFFFF as u64));
+        assert_eq!(UCN{ contents: vec![0x00000000FFFFFFFF] },
+                   UCN::from(0xFFFFFFFFFFFFFFFF as u32));
+    }
+
+    quickcheck! {
+        fn builder_u8_upgrade_u16(x: u8) -> bool {
+            UCN::from(x) == UCN::from(x as u16)
+        }
+        fn builder_u16_upgrade_u32(x: u16) -> bool {
+            UCN::from(x) == UCN::from(x as u32)
+        }
+        fn builder_u32_upgrade_u64(x: u32) -> bool {
+            UCN::from(x) == UCN::from(x as u64)
+        }
+        fn builder_u8_roundtrips(x: u8) -> bool {
+            let thereback: u8 = UCN::from(x).into();
+            x == thereback
+        }
+        fn builder_u16_roundtrips(x: u16) -> bool {
+            let thereback: u16 = UCN::from(x).into();
+            x == thereback
+        }
+        fn builder_u32_roundtrips(x: u32) -> bool {
+            let thereback: u32 = UCN::from(x).into();
+            x == thereback
+        }
+        fn builder_u64_roundtrips(x: u64) -> bool {
+            let thereback: u64 = UCN::from(x).into();
+            x == thereback
+        }
+    }
+
+    quickcheck! {
+        fn u64_comparison_sane(x: u64, y: u64) -> bool {
+            let ucnx = UCN::from(x);
+            let ucny = UCN::from(y);
+            ucnx.cmp(&ucny) == x.cmp(&y)
+        }
+        fn longer_is_greater(x: u64, y: u64) -> bool {
+            if x == 0 {
+                true
+            } else {
+                let ucnx = UCN{ contents: vec![x, 1] };
+                let ucny = UCN::from(y);
+                ucnx.cmp(&ucny) == Ordering::Greater
+            }
+        }
+    }
+}