Shifting >= 128 loops (#54)

i.e. n mod 128, so 128 shifts 0, 129 shifts 1 etc
appmattus · Jun 13, 2024 · e723c9e · e723c9e
1 parent 1ed1965
commit e723c9e
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Showing 2 changed files with 8 additions and 6 deletions.
diff --git a/cryptohash/src/commonMain/kotlin/com/appmattus/crypto/internal/core/uint/UInt128Utils.kt b/cryptohash/src/commonMain/kotlin/com/appmattus/crypto/internal/core/uint/UInt128Utils.kt
@@ -105,6 +105,7 @@ internal fun uint128DivMod(dividend: UInt128, divisor: UInt128): Pair<UInt128, U
 
 @Suppress("ReturnCount")
 internal fun uint128Shl(v: UInt128, n: Int): UInt128 {
+    val n = n and 0b1111111
     if (n == 0) {
         return v
     } else if (n >= UInt128.SIZE_BITS || n <= -UInt128.SIZE_BITS) {
@@ -125,6 +126,7 @@ internal fun uint128Shl(v: UInt128, n: Int): UInt128 {
 
 @Suppress("ReturnCount")
 internal fun uint128Shr(v: UInt128, n: Int): UInt128 {
+    val n = n and 0b1111111
     if (n == 0) {
         return v
     } else if (n >= UInt128.SIZE_BITS || n <= -UInt128.SIZE_BITS) {

diff --git a/cryptohash/src/commonTest/kotlin/com/appmattus/crypto/internal/core/uint/UInt128Test.kt b/cryptohash/src/commonTest/kotlin/com/appmattus/crypto/internal/core/uint/UInt128Test.kt
@@ -254,9 +254,9 @@ class UInt128Test {
         assertEquals(UInt128(ULong.MAX_VALUE, ULong.MAX_VALUE - 1u), MAX_VALUE shl 1)
         assertEquals(UInt128(0uL, 2uL), ONE shl 1)
         assertEquals(UInt128(1uL, 0uL), UInt128(0uL, (1uL shl (ULong.SIZE_BITS - 1))) shl 1)
-        assertEquals(ZERO, ONE shl UInt128.SIZE_BITS)
-        assertEquals(ZERO, ONE shl -UInt128.SIZE_BITS)
-        assertEquals(ONE, 2u.toUInt128() shl -1)
+        assertEquals(ONE, ONE shl UInt128.SIZE_BITS)
+        assertEquals(ONE, ONE shl -UInt128.SIZE_BITS)
+        assertEquals((2uL shl -1).toUInt128(), 2u.toUInt128() shl -1)
 
         for (i in 0 until 64) {
             assertEquals((1uL shl i).toUInt128(), ONE shl i)
@@ -279,9 +279,9 @@ class UInt128Test {
         assertEquals(ZERO, ONE shr 1)
         assertEquals(ONE, UInt128(0uL, 2uL) shr 1)
         assertEquals(UInt128(0uL, 0x8000000000000000uL), UInt128(1uL, 0uL) shr 1)
-        assertEquals(ZERO, highBit shr UInt128.SIZE_BITS)
-        assertEquals(ZERO, highBit shr -UInt128.SIZE_BITS)
-        assertEquals(2u.toUInt128(), ONE shr -1)
+        assertEquals(highBit, highBit shr UInt128.SIZE_BITS)
+        assertEquals(highBit, highBit shr -UInt128.SIZE_BITS)
+        assertEquals((1uL shr -1).toUInt128(), ONE shr -1)
 
         val value = ULong.MAX_VALUE.toUInt128()
         for (i in 0 until 64) {