Merge pull request #332 from DaniPopes/bytes-perf

perf: generalize specialized full-limb `from_*_bytes` impl
recmo · Oct 15, 2023 · 666cd31 · 666cd31
2 parents 23fc40f + 4a6074d
commit 666cd31
Showing 1 changed file with 25 additions and 25 deletions.
diff --git a/src/bytes.rs b/src/bytes.rs
@@ -210,19 +210,7 @@ impl<const BITS: usize, const LIMBS: usize> Uint<BITS, LIMBS> {
     pub const fn from_be_bytes<const BYTES: usize>(bytes: [u8; BYTES]) -> Self {
         // TODO: Use a `const {}` block for this assertion
         assert!(BYTES == Self::BYTES, "BYTES must be equal to Self::BYTES");
-        if BYTES % 8 == 0 {
-            // Optimized implementation for full-limb types.
-            let mut limbs = [0; LIMBS];
-            let end = bytes.as_ptr_range().end;
-            let mut i = 0;
-            while i < LIMBS {
-                limbs[i] = u64::from_be_bytes(unsafe { *end.sub((i + 1) * 8).cast() });
-                i += 1;
-            }
-            Self::from_limbs(limbs)
-        } else {
-            Self::from_be_slice(&bytes)
-        }
+        Self::from_be_slice(&bytes)
     }
 
     /// Creates a new integer from a big endian slice of bytes.
@@ -256,6 +244,18 @@ impl<const BITS: usize, const LIMBS: usize> Uint<BITS, LIMBS> {
             return None;
         }
 
+        if Self::BYTES % 8 == 0 && bytes.len() == Self::BYTES {
+            // Optimized implementation for full-limb types.
+            let mut limbs = [0; LIMBS];
+            let end = bytes.as_ptr_range().end;
+            let mut i = 0;
+            while i < LIMBS {
+                limbs[i] = u64::from_be_bytes(unsafe { *end.sub((i + 1) * 8).cast() });
+                i += 1;
+            }
+            return Some(Self::from_limbs(limbs));
+        }
+
         let mut limbs = [0; LIMBS];
         let mut i = 0;
         let mut c = bytes.len();
@@ -288,18 +288,7 @@ impl<const BITS: usize, const LIMBS: usize> Uint<BITS, LIMBS> {
     pub const fn from_le_bytes<const BYTES: usize>(bytes: [u8; BYTES]) -> Self {
         // TODO: Use a `const {}` block for this assertion
         assert!(BYTES == Self::BYTES, "BYTES must be equal to Self::BYTES");
-        if BYTES % 8 == 0 {
-            // Optimized implementation for full-limb types.
-            let mut limbs = [0; LIMBS];
-            let mut i = 0;
-            while i < LIMBS {
-                limbs[i] = u64::from_le_bytes(unsafe { *bytes.as_ptr().add(i * 8).cast() });
-                i += 1;
-            }
-            Self::from_limbs(limbs)
-        } else {
-            Self::from_le_slice(&bytes)
-        }
+        Self::from_le_slice(&bytes)
     }
 
     /// Creates a new integer from a little endian slice of bytes.
@@ -333,6 +322,17 @@ impl<const BITS: usize, const LIMBS: usize> Uint<BITS, LIMBS> {
             return None;
         }
 
+        if Self::BYTES % 8 == 0 && bytes.len() == Self::BYTES {
+            // Optimized implementation for full-limb types.
+            let mut limbs = [0; LIMBS];
+            let mut i = 0;
+            while i < LIMBS {
+                limbs[i] = u64::from_le_bytes(unsafe { *bytes.as_ptr().add(i * 8).cast() });
+                i += 1;
+            }
+            return Some(Self::from_limbs(limbs));
+        }
+
         let mut limbs = [0; LIMBS];
         let mut i = 0;
         while i < bytes.len() {