Merge #58

58: Add accessor to get the sign of a Mpi r=Goirad a=jack-fortanix



Co-authored-by: Jack Lloyd <[email protected]>

Author: bors[bot]

mbedtls/src/bignum/mod.rs

@@ -80,6 +80,13 @@ impl ::core::str::FromStr for Mpi {
     }
 }
 
+#[derive(Debug,Copy,Clone,Eq,PartialEq)]
+pub enum Sign {
+    Negative,
+    Zero,
+    Positive,
+}
+
 impl Clone for Mpi {
     fn clone(&self) -> Self {
         Mpi::copy(&self.handle()).expect("copy succeeded")
@@ -140,6 +147,17 @@ impl Mpi {
         Ok(self.get_limb(0) as u32)
     }
 
+    pub fn sign(&self) -> Sign {
+        let cmp = unsafe { mpi_cmp_int(&self.inner, 0) };
+        if cmp < 0 {
+            Sign::Negative
+        } else if cmp == 0 {
+            Sign::Zero
+        } else {
+            Sign::Positive
+        }
+    }
+
     pub fn to_string_radix(&self, radix: i32) -> Result<String> {
         let mut olen = 0;
         let r =

mbedtls/tests/bignum.rs

@@ -8,7 +8,7 @@
 
 extern crate mbedtls;
 
-use mbedtls::bignum::Mpi;
+use mbedtls::bignum::{Mpi, Sign};
 
 #[cfg(feature = "std")]
 #[test]
@@ -130,8 +130,10 @@ fn bignum_op_assign() {
     x *= 2;
     assert_eq!(format!("{}", x), "360");
 
+    assert_eq!(x.sign(), Sign::Positive);
     x *= Mpi::new(-2).unwrap();
     assert_eq!(format!("{}", x), "-720");
+    assert_eq!(x.sign(), Sign::Negative);
 
     x /= Mpi::new(-3).unwrap();
     assert_eq!(format!("{}", x), "240");
@@ -354,6 +356,7 @@ const BASE58_ALPHABET: &[u8] = b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmno
 
 fn base58_encode(bits: &[u8]) -> mbedtls::Result<String> {
     let zero = Mpi::new(0)?;
+    assert_eq!(zero.sign(), Sign::Zero);
     let mut n = Mpi::from_binary(bits)?;
     let radix: i64 = 58;