Add Point::serialized_len

Signed-off by: Nikita Sorokovikov <nikita@dfns.co>

Author: maurges

generic-ec/CHANGELOG.md

@@ -1,3 +1,6 @@
+## v0.4.3
+* Add `Point::serialized_len`
+
 ## v0.4.2
 * Update links, add info about our discord [#44]
 

generic-ec/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "generic-ec"
-version = "0.4.2"
+version = "0.4.3"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/LFDT-Lockness/generic-ec"

generic-ec/src/point/mod.rs

@@ -97,6 +97,19 @@ impl<E: Curve> Point<E> {
             .and_then(Self::try_from_raw)
             .ok_or(InvalidPoint)
     }
+
+    /// Returns size of bytes buffer that can fit a serialized point
+    ///
+    /// `compressed` parameter has the same meaning as for [`Point::to_bytes`]; a
+    /// buffer created with length of `Point::serialized_len(compress)` would fit
+    /// exactly the serialization `p.to_bytes(compress)`.
+    pub fn serialized_len(compressed: bool) -> usize {
+        if compressed {
+            E::CompressedPointArray::zeroes().as_ref().len()
+        } else {
+            E::UncompressedPointArray::zeroes().as_ref().len()
+        }
+    }
 }
 
 impl<E: Curve> TryFromRaw for Point<E> {

tests/tests/curves.rs

@@ -110,6 +110,8 @@ mod tests {
             let bytes_compressed = point.to_bytes(true);
             let bytes_uncompressed = point.to_bytes(false);
             assert!(bytes_compressed.len() <= bytes_uncompressed.len());
+            assert_eq!(bytes_compressed.len(), Point::<E>::serialized_len(true));
+            assert_eq!(bytes_uncompressed.len(), Point::<E>::serialized_len(false));
 
             let p1 = Point::<E>::from_bytes(&bytes_compressed).unwrap();
             let p2 = Point::<E>::from_bytes(&bytes_uncompressed).unwrap();