From 10a5b78f35a017b92a3f24e1d9c88a16b3f9ecac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timoth=C3=A9e=20Delabrouille?=
 <34384633+tdelabro@users.noreply.github.com>
Date: Thu, 11 Jan 2024 05:39:11 +0100
Subject: [PATCH] feat: impl From<EthAddress> for StarkFelt (#164)

* feat: impl From<EthAddress> for StarkFelt

* add safety comment on new_unchecked

* improve docstrings
---
 .gitignore  |  1 +
 src/core.rs |  9 +++++++++
 src/hash.rs | 18 ++++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/.gitignore b/.gitignore
index 8e1ad418..d68be5fc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 /logs
 /target
 /Cargo.lock
+*.DS_Store
diff --git a/src/core.rs b/src/core.rs
index 20b37f13..561a3f54 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -264,6 +264,15 @@ impl TryFrom<StarkFelt> for EthAddress {
     }
 }
 
+impl From<EthAddress> for StarkFelt {
+    fn from(value: EthAddress) -> Self {
+        let mut bytes = [0u8; 32];
+        // Padding H160 with zeros to 32 bytes (big endian)
+        bytes[12..32].copy_from_slice(value.0.as_bytes());
+        StarkFelt::new_unchecked(bytes)
+    }
+}
+
 impl TryFrom<PrefixedBytesAsHex<20_usize>> for EthAddress {
     type Error = StarknetApiError;
     fn try_from(val: PrefixedBytesAsHex<20_usize>) -> Result<Self, Self::Error> {
diff --git a/src/hash.rs b/src/hash.rs
index acbb1838..e9ab99d2 100644
--- a/src/hash.rs
+++ b/src/hash.rs
@@ -69,6 +69,24 @@ impl StarkFelt {
         Err(StarknetApiError::OutOfRange { string: hex_str_from_bytes::<32, true>(bytes) })
     }
 
+    /// Returns a new *unchecked* [`StarkFelt`]
+    ///
+    /// # Safety
+    ///
+    /// To avoid undefined behavior, refer to [`StarkFelt`] struct's docstring
+    /// for the required constraints on the `bytes` argument, or use [`StarkFelt::new`] instead of
+    /// this method.
+    ///
+    /// # Usage
+    ///
+    /// Most of the time you should use `new` instead, but it comes in handy for a few cases:
+    /// - creating instances of `StarkFelt` at compile time
+    /// - implementing `From<T> for StarkFelt` for types that have a smaller binary representation
+    ///   than `StarkFelt`
+    pub const fn new_unchecked(bytes: [u8; 32]) -> StarkFelt {
+        Self(bytes)
+    }
+
     /// [StarkFelt] constant that's equal to 0.
     pub const ZERO: Self = { Self::from_u128(0_u128) };