feat(core): convert to/from ByteArray

ObserverOfTime · ObserverOfTime · commit c0d0f3a5f2ab · 2024-05-09T00:03:40.000+03:00
diff --git a/kbigint/src/androidMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt b/kbigint/src/androidMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt
@@ -14,8 +14,7 @@ actual class KBigInt private constructor(private var value: BigInteger) : Compar
     actual constructor(number: Long) : this(number.toBigInteger())
 
     /** Convert a [ByteArray] to a [KBigInt]. */
-    @Suppress("unused")
-    constructor(bytes: ByteArray) : this(BigInteger(bytes))
+    actual constructor(bytes: ByteArray) : this(BigInteger(bytes))
 
     @get:JvmName("signum")
     actual val sign: Int
@@ -115,6 +114,5 @@ actual class KBigInt private constructor(private var value: BigInteger) : Compar
     fun toDouble() = value.toDouble()
 
     /** Convert the value to a [ByteArray]. */
-    @Suppress("unused")
-    fun toByteArray(): ByteArray = value.toByteArray()
+    actual fun toByteArray(): ByteArray = value.toByteArray()
 }
diff --git a/kbigint/src/androidUnitTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt b/kbigint/src/androidUnitTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt
@@ -52,6 +52,7 @@ actual class KBigIntTest {
     @Test
     actual fun testInvert() {
         assertEquals(KBigInt(-2147483649L), long.inv())
+        assertEquals(KBigInt(2147483649L), -long.inv())
     }
 
     @Test
@@ -101,4 +102,13 @@ actual class KBigIntTest {
         assertEquals(OVER_MAX_INT, long.toLong())
         assertEquals(OVER_MAX_INT.toDouble(), long.toDouble())
     }
+
+    @Test
+    actual fun testByteArray() {
+        assertEquals(KBigInt(262146), KBigInt(byteArrayOf(4, 0, 2)))
+        assertEquals(KBigInt(-6021), KBigInt(byteArrayOf(-24, 123)))
+
+        assertContentEquals(byteArrayOf(4, 0, 2), KBigInt(262146).toByteArray())
+        assertContentEquals(byteArrayOf(-24, 123), KBigInt(-6021).toByteArray())
+    }
 }
diff --git a/kbigint/src/commonMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt b/kbigint/src/commonMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt
@@ -11,6 +11,9 @@ expect class KBigInt : Comparable<KBigInt> {
     /** Convert a [Long] to a [KBigInt]. */
     constructor(number: Long)
 
+    /** Convert a [ByteArray] to a [KBigInt]. */
+    constructor(bytes: ByteArray)
+
     /**
      * The sign of the value:
      *
@@ -71,6 +74,9 @@ expect class KBigInt : Comparable<KBigInt> {
     /** Get the absolute value. */
     fun abs(): KBigInt
 
+    /** Convert the value to a [ByteArray]. */
+    fun toByteArray(): ByteArray
+
     override operator fun compareTo(other: KBigInt): Int
 
     override fun equals(other: Any?): Boolean
diff --git a/kbigint/src/commonTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt b/kbigint/src/commonTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt
@@ -18,4 +18,5 @@ expect class KBigIntTest {
     fun testEquals()
     fun testHashCode()
     fun testToString()
+    fun testByteArray()
 }
diff --git a/kbigint/src/javascript/kbigint-utils.mjs b/kbigint/src/javascript/kbigint-utils.mjs
@@ -1,16 +1,5 @@
 // noinspection JSUnusedGlobalSymbols
 
-/**
- * @private
- * @param {bigint} n
- * @param {bigint} k
- * @returns {bigint}
- * @see https://stackoverflow.com/a/53684036/21974435
- */
-function newtonRoot(n, k) {
-    const x = ((n / k) + k) >> 1n;
-    return k === x || k === (x - 1n) ? k : newtonRoot(n, x);
-}
 /**
  * Return the sign of the value.
  *
@@ -64,3 +53,112 @@ export function cmp(a, b) {
 export function pow(value, n) {
     return value ** BigInt(n);
 }
+
+/**
+ * Convert a {@link BigInt} to an {@link Int8Array}.
+ *
+ * @param value {bigint}
+ * @return {Int8Array}
+ * @see https://coolaj86.com/articles/convert-js-bigints-to-typedarrays/
+ */
+export function toByteArray(value) {
+    let hex = bnToHex(value);
+    if (hex.length & 1) hex = '0' + hex;
+    const len = hex.length >> 1;
+    const arr = new Int8Array(len);
+    for (let i = 0, j = 0; i < len; i += 1, j += 2) {
+        arr[i] = parseInt(hex.slice(j, j + 2), 16);
+    }
+    return arr;
+}
+
+/**
+ * Convert a numeric {@link Array} to a {@link BigInt}.
+ *
+ * @param bytes {number[] | ArrayLike<number>}
+ * @return {bigint}
+ * @see https://coolaj86.com/articles/convert-js-bigints-to-typedarrays/
+ */
+export function fromByteArray(bytes) {
+    const hex = new Array(bytes.length);
+    Uint8Array.from(bytes).forEach(n => {
+        const h = n.toString(16);
+        hex.push(h.length & 1 ? '0' + h : h);
+    });
+    return hexToBn(hex.join(''));
+}
+
+/**
+ * @private
+ * @param {bigint} n
+ * @param {bigint} k
+ * @returns {bigint}
+ * @see https://stackoverflow.com/a/53684036/21974435
+ */
+function newtonRoot(n, k) {
+    const x = ((n / k) + k) >> 1n;
+    return k === x || k === (x - 1n) ? k : newtonRoot(n, x);
+}
+
+/**
+ * @private
+ * @param str {string}
+ * @return {string}
+ */
+function bitFlip(str) {
+    return Array.from(str, i => i === '0' ? '1' : '0').join('')
+}
+
+/**
+ * @private
+ * @param bn {bigint}
+ * @return {bigint}
+ * @see https://coolaj86.com/articles/convert-decimal-to-hex-with-js-bigints/
+ */
+function bitNot(bn) {
+    let bin = (-bn).toString(2)
+    while (bin.length % 8) bin = '0' + bin;
+    const prefix = bin[0] === '1' && bin.slice(1).includes('1')
+        ? '11111111' : ''
+    return BigInt('0b' + prefix + bitFlip(bin)) + 1n;
+}
+
+/**
+ * @private
+ * @param hex {string}
+ * @return {number}
+ */
+function highByte(hex) {
+    return parseInt(hex.slice(0, 2), 16);
+}
+
+/**
+ * @private
+ * @param hex {string}
+ * @return {bigint}
+ * @see https://coolaj86.com/articles/convert-hex-to-decimal-with-js-bigints/
+ */
+function hexToBn(hex) {
+    if (hex.length & 1) hex = '0' + hex;
+    let bn = BigInt('0x' + hex);
+    if (highByte(hex) & 128) {
+        // manually perform two's complement (flip bits, add one)
+        // (because JS binary operators are incorrect for negatives)
+        bn = -(BigInt('0b' + bitFlip(bn.toString(2))) + 1n);
+    }
+    return bn;
+}
+
+/**
+ * @private
+ * @param bn {bigint}
+ * @return {string}
+ * @see https://coolaj86.com/articles/convert-decimal-to-hex-with-js-bigints/
+ */
+function bnToHex(bn) {
+    const pos = bn >= 0n;
+    let hex = (pos ? bn : bitNot(bn)).toString(16);
+    if (hex.length & 1) hex = '0' + hex;
+    if (pos && (highByte(hex) & 128)) hex = '00' + hex;
+    return hex;
+}
diff --git a/kbigint/src/jsMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt b/kbigint/src/jsMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt
@@ -14,6 +14,9 @@ actual class KBigInt private constructor(@JsExternalArgument private var value:
     @Suppress("NON_EXPORTABLE_TYPE")
     actual constructor(number: Long) : this(BigInt(number))
 
+    @JsName("fromBuffer")
+    actual constructor(bytes: ByteArray) : this(BigInt(KBigIntUtils.fromByteArray(bytes)))
+
     actual val sign: Int
         get() = KBigIntUtils.sign(value)
 
@@ -153,4 +156,6 @@ actual class KBigInt private constructor(@JsExternalArgument private var value:
     fun toDouble() = toString().toDouble()
 
     actual override fun toString() = value.toString()
+
+    actual fun toByteArray() = KBigIntUtils.toByteArray(value)
 }
diff --git a/kbigint/src/jsMain/kotlin/io/github/observeroftime/kbigint/KBigIntUtils.kt b/kbigint/src/jsMain/kotlin/io/github/observeroftime/kbigint/KBigIntUtils.kt
@@ -12,4 +12,6 @@ internal external object KBigIntUtils {
     fun sign(value: BigInt): Int
     fun cmp(a: BigInt, b: BigInt): Int
     fun pow(value: BigInt, n: Int): BigInt
+    fun toByteArray(value: BigInt): ByteArray
+    fun fromByteArray(bytes: ByteArray): BigInt
 }
diff --git a/kbigint/src/jsTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt b/kbigint/src/jsTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt
@@ -52,6 +52,7 @@ actual class KBigIntTest {
     @Test
     actual fun testInvert() {
         assertEquals(KBigInt(-2147483649L), long.inv())
+        assertEquals(KBigInt(2147483649L), -long.inv())
     }
 
     @Test
@@ -103,4 +104,13 @@ actual class KBigIntTest {
         assertFailsWith(NumberFormatException::class) { long.toInt() }
         assertEquals(OVER_MAX_INT.toDouble(), long.toDouble())
     }
+
+    @Test
+    actual fun testByteArray() {
+        assertContentEquals(byteArrayOf(4, 0, 2), KBigInt(262146).toByteArray())
+        assertContentEquals(byteArrayOf(-24, 123), KBigInt(-6021).toByteArray())
+
+        assertEquals(KBigInt(262146), KBigInt(byteArrayOf(4, 0, 2)))
+        assertEquals(KBigInt(-6021), KBigInt(byteArrayOf(-24, 123)))
+    }
 }
diff --git a/kbigint/src/jvmMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt b/kbigint/src/jvmMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt
@@ -12,8 +12,7 @@ actual class KBigInt private constructor(private var value: BigInteger) : Compar
     actual constructor(number: Long) : this(number.toBigInteger())
 
     /** Convert a [ByteArray] to a [KBigInt]. */
-    @Suppress("unused")
-    constructor(bytes: ByteArray) : this(BigInteger(bytes))
+    actual constructor(bytes: ByteArray) : this(BigInteger(bytes))
 
     @get:JvmName("signum")
     actual val sign: Int
@@ -118,6 +117,5 @@ actual class KBigInt private constructor(private var value: BigInteger) : Compar
      *
      * @see [BigInteger.toByteArray]
      */
-    @Suppress("unused")
-    fun toByteArray(): ByteArray = value.toByteArray()
+    actual fun toByteArray(): ByteArray = value.toByteArray()
 }
diff --git a/kbigint/src/jvmTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt b/kbigint/src/jvmTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt
@@ -52,6 +52,7 @@ actual class KBigIntTest {
     @Test
     actual fun testInvert() {
         assertEquals(KBigInt(-2147483649L), long.inv())
+        assertEquals(KBigInt(2147483649L), -long.inv())
     }
 
     @Test
@@ -101,4 +102,13 @@ actual class KBigIntTest {
         assertEquals(OVER_MAX_INT, long.toLong())
         assertEquals(OVER_MAX_INT.toDouble(), long.toDouble())
     }
+
+    @Test
+    actual fun testByteArray() {
+        assertEquals(KBigInt(262146), KBigInt(byteArrayOf(4, 0, 2)))
+        assertEquals(KBigInt(-6021), KBigInt(byteArrayOf(-24, 123)))
+
+        assertContentEquals(byteArrayOf(4, 0, 2), KBigInt(262146).toByteArray())
+        assertContentEquals(byteArrayOf(-24, 123), KBigInt(-6021).toByteArray())
+    }
 }
diff --git a/kbigint/src/nativeMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt b/kbigint/src/nativeMain/kotlin/io/github/observeroftime/kbigint/KBigInt.kt
@@ -2,6 +2,7 @@ package io.github.observeroftime.kbigint
 
 import kotlin.experimental.ExperimentalNativeApi
 import kotlin.experimental.ExperimentalObjCName
+import kotlin.experimental.inv
 import kotlin.native.ref.createCleaner
 import kotlinx.cinterop.*
 import net.libtom.libtommath.*
@@ -52,6 +53,25 @@ actual class KBigInt private constructor(private var value: mp_int) : Comparable
         mp_init_i64(value.ptr, number).check()
     }
 
+    /** Convert a [ByteArray] to a [KBigInt]. */
+    actual constructor(bytes: ByteArray) : this() {
+        val size = bytes.size + 1
+        val sign = if (bytes.any { it < 0 }) 1 else 0
+        // XXX: libtommath expects bytes in this format
+        val copy = ByteArray(size) {
+            when {
+                it == 0 -> sign.toByte()
+                sign == 0 -> bytes[it - 1]
+                bytes[it - 1] <= 0 -> bytes[it - 1].inv()
+                else -> bytes[it - 1].unaryMinus().toByte()
+            }
+        }
+        memScoped {
+            val array = allocArrayOf(copy).reinterpret<UByteVar>()
+            mp_from_sbin(value.ptr, array, size.toULong()).check()
+        }
+    }
+
     actual val sign: Int
         get() = kbi_mp_sign(value.ptr)
 
@@ -355,6 +375,23 @@ actual class KBigInt private constructor(private var value: mp_int) : Comparable
     /** Convert the value to a [Double]. */
     fun toDouble() = mp_get_double(value.ptr)
 
+    /** Convert the value to a [ByteArray]. */
+    actual fun toByteArray(): ByteArray = memScoped {
+        val size = mp_sbin_size(value.ptr)
+        val array = allocArray<UByteVar>(size.toInt())
+        mp_to_sbin(value.ptr, array, size, null).check()
+        val sign = array[0].toInt()
+        ByteArray(size.toInt() - 1) {
+            val byte = array[it + 1].toByte()
+            when {
+                sign == 0 -> byte
+                byte > 0 -> byte.inv()
+                byte.toInt() == -1 -> 0
+                else -> byte.unaryMinus().toByte()
+            }
+        }
+    }
+
     private inline fun dispose(value: mp_int) {
         mp_clear(value.ptr)
         nativeHeap.free(value)
diff --git a/kbigint/src/nativeTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt b/kbigint/src/nativeTest/kotlin/io/github/observeroftime/kbigint/KBigIntTest.kt
@@ -68,6 +68,7 @@ actual class KBigIntTest {
     @Test
     actual fun testInvert() {
         assertEquals(KBigInt(-2147483649L), long.inv())
+        assertEquals(KBigInt(2147483649L), -long.inv())
     }
 
     @Test
@@ -117,4 +118,13 @@ actual class KBigIntTest {
         assertEquals(OVER_MAX_INT, long.toLong())
         assertEquals(OVER_MAX_INT.toDouble(), long.toDouble())
     }
+
+    @Test
+    actual fun testByteArray() {
+        assertContentEquals(byteArrayOf(4, 0, 2), KBigInt(262146).toByteArray())
+        assertContentEquals(byteArrayOf(-24, 123), KBigInt(-6021).toByteArray())
+
+        assertEquals(KBigInt(262146), KBigInt(byteArrayOf(4, 0, 2)))
+        assertEquals(KBigInt(-6021), KBigInt(byteArrayOf(-24, 123)))
+    }
 }

Original file line number	Diff line number	Diff line change
`@@ -18,4 +18,5 @@ expect class KBigIntTest {`
`18`	`18`	`fun testEquals()`
`19`	`19`	`fun testHashCode()`
`20`	`20`	`fun testToString()`
	`21`	`+ fun testByteArray()`
`21`	`22`	`}`
Original file line number	Diff line number	Diff line change
`@@ -12,4 +12,6 @@ internal external object KBigIntUtils {`
`12`	`12`	`fun sign(value: BigInt): Int`
`13`	`13`	`fun cmp(a: BigInt, b: BigInt): Int`
`14`	`14`	`fun pow(value: BigInt, n: Int): BigInt`
	`15`	`+ fun toByteArray(value: BigInt): ByteArray`
	`16`	`+ fun fromByteArray(bytes: ByteArray): BigInt`
`15`	`17`	`}`