From 6dc3cf3b873e375d47394cd6fd77b7de32e14674 Mon Sep 17 00:00:00 2001
From: Infendro <infendro@noreply.infendro.com>
Date: Thu, 4 Dec 2025 19:13:39 +0100
Subject: [PATCH] refactor Keccak

---
 .../kotlin/com/infendro/hash/keccak/Keccak.kt | 71 +++++++++++--------
 1 file changed, 42 insertions(+), 29 deletions(-)

diff --git a/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt b/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
index 0365c8c..7d92f9e 100644
--- a/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
@@ -41,44 +41,39 @@ open class Keccak(
     ): UByteArray {
         val state = ULongArray(25)
 
-        // padding
-        val paddedValue = buildList {
+        val blocks = pad(value)
+            .chunked(rate) { it.toUByteArray() }
+        for (block in blocks) {
+            absorb(state, block)
+        }
+
+        return squeeze(state)
+    }
+
+    private fun pad(
+        value: UByteArray,
+    ): UByteArray {
+        return buildList {
             addAll(value)
             add(domain)
             while ((size % rate) != (rate - 1)) {
                 add(0x00U)
             }
             add(0x80U)
-        }
-
-        // absorb
-        val blocks = paddedValue
-            .chunked(rate) { it.toUByteArray() }
-        for (block in blocks) {
-            val numbers = block.toULongArray(LITTLE_ENDIAN)
-            for ((i, number) in numbers.withIndex()) {
-                state[i] = state[i] xor number
-            }
-            permute(state)
-        }
-
-        // squeeze
-        return buildList {
-            var i = 0
-            while (size < bytes) {
-                if (i == rate / 8) {
-                    permute(state)
-                    i = 0
-                }
-
-                addAll(
-                    state[i++].toUByteArray(LITTLE_ENDIAN)
-                        .sliceArray(0..<min(bytes - size, 8))
-                )
-            }
         }.toUByteArray()
     }
 
+    private fun absorb(
+        state: ULongArray,
+        block: UByteArray,
+    ) {
+        val numbers = block.toULongArray(LITTLE_ENDIAN)
+        for ((i, number) in numbers.withIndex()) {
+            state[i] = state[i] xor number
+        }
+        permute(state)
+    }
+
     private fun permute(
         a: ULongArray,
     ) {
@@ -112,4 +107,22 @@ open class Keccak(
             a[0] = a[0] xor rc[round]
         }
     }
+
+    fun squeeze(
+        state: ULongArray,
+    ): UByteArray {
+        return buildList {
+            var i = 0
+            while (size < bytes) {
+                if (i == rate / 8) {
+                    permute(state)
+                    i = 0
+                }
+                addAll(
+                    state[i++].toUByteArray(LITTLE_ENDIAN)
+                        .sliceArray(0..<min(bytes - size, 8))
+                )
+            }
+        }.toUByteArray()
+    }
 }