1 files changed, 51 insertions, 0 deletions
diff --git a/vendor/elliptic-curve/src/field.rs b/vendor/elliptic-curve/src/field.rs
new file mode 100644
index 0000000..66055ab
--- /dev/null
+++ b/vendor/elliptic-curve/src/field.rs
@@ -0,0 +1,51 @@
+//! Field elements.
+
+use crate::{
+    bigint::{ArrayEncoding, ByteArray, Integer},
+    Curve,
+};
+use generic_array::{typenum::Unsigned, GenericArray};
+
+/// Size of serialized field elements of this elliptic curve.
+pub type FieldBytesSize<C> = <C as Curve>::FieldBytesSize;
+
+/// Byte representation of a base/scalar field element of a given curve.
+pub type FieldBytes<C> = GenericArray<u8, FieldBytesSize<C>>;
+
+/// Trait for decoding/encoding `Curve::Uint` from/to [`FieldBytes`] using
+/// curve-specific rules.
+///
+/// Namely a curve's modulus may be smaller than the big integer type used to
+/// internally represent field elements (since the latter are multiples of the
+/// limb size), such as in the case of curves like NIST P-224 and P-521, and so
+/// it may need to be padded/truncated to the right length.
+///
+/// Additionally, different curves have different endianness conventions, also
+/// captured here.
+pub trait FieldBytesEncoding<C>: ArrayEncoding + Integer
+where
+    C: Curve,
+{
+    /// Decode unsigned integer from serialized field element.
+    ///
+    /// The default implementation assumes a big endian encoding.
+    fn decode_field_bytes(field_bytes: &FieldBytes<C>) -> Self {
+        debug_assert!(field_bytes.len() <= Self::ByteSize::USIZE);
+        let mut byte_array = ByteArray::<Self>::default();
+        let offset = Self::ByteSize::USIZE.saturating_sub(field_bytes.len());
+        byte_array[offset..].copy_from_slice(field_bytes);
+        Self::from_be_byte_array(byte_array)
+    }
+
+    /// Encode unsigned integer into serialized field element.
+    ///
+    /// The default implementation assumes a big endian encoding.
+    fn encode_field_bytes(&self) -> FieldBytes<C> {
+        let mut field_bytes = FieldBytes::<C>::default();
+        debug_assert!(field_bytes.len() <= Self::ByteSize::USIZE);
+
+        let offset = Self::ByteSize::USIZE.saturating_sub(field_bytes.len());
+        field_bytes.copy_from_slice(&self.to_be_byte_array()[offset..]);
+        field_bytes
+    }
+}