Support ByteString to/from NSData conversions (#384)

* Support ByteString to/from NSData conversions

Closes #266

bytestring/api/kotlinx-io-bytestring.klib.api

@@ -1,5 +1,6 @@
 // Klib ABI Dump
 // Targets: [androidNativeArm32, androidNativeArm64, androidNativeX64, androidNativeX86, iosArm64, iosSimulatorArm64, iosX64, js, linuxArm32Hfp, linuxArm64, linuxX64, macosArm64, macosX64, mingwX64, tvosArm64, tvosSimulatorArm64, tvosX64, wasmJs, wasmWasi, watchosArm32, watchosArm64, watchosDeviceArm64, watchosSimulatorArm64, watchosX64]
+// Alias: apple => [iosArm64, iosSimulatorArm64, iosX64, macosArm64, macosX64, tvosArm64, tvosSimulatorArm64, tvosX64, watchosArm32, watchosArm64, watchosDeviceArm64, watchosSimulatorArm64, watchosX64]
 // Rendering settings:
 // - Signature version: 2
 // - Show manifest properties: true
@@ -84,3 +85,9 @@ final fun kotlinx.io.bytestring/ByteString(): kotlinx.io.bytestring/ByteString /
 final fun kotlinx.io.bytestring/ByteString(kotlin/ByteArray...): kotlinx.io.bytestring/ByteString // kotlinx.io.bytestring/ByteString|ByteString(kotlin.ByteArray...){}[0]
 final fun kotlinx.io.bytestring/ByteString(kotlin/UByteArray...): kotlinx.io.bytestring/ByteString // kotlinx.io.bytestring/ByteString|ByteString(kotlin.UByteArray...){}[0]
 final inline fun kotlinx.io.bytestring/buildByteString(kotlin/Int = ..., kotlin/Function1<kotlinx.io.bytestring/ByteStringBuilder, kotlin/Unit>): kotlinx.io.bytestring/ByteString // kotlinx.io.bytestring/buildByteString|buildByteString(kotlin.Int;kotlin.Function1<kotlinx.io.bytestring.ByteStringBuilder,kotlin.Unit>){}[0]
+
+// Targets: [apple]
+final fun (kotlinx.io.bytestring/ByteString).kotlinx.io.bytestring/toNSData(): platform.Foundation/NSData // kotlinx.io.bytestring/toNSData|toNSData@kotlinx.io.bytestring.ByteString(){}[0]
+
+// Targets: [apple]
+final fun (platform.Foundation/NSData).kotlinx.io.bytestring/toByteString(): kotlinx.io.bytestring/ByteString // kotlinx.io.bytestring/toByteString|toByteString@platform.Foundation.NSData(){}[0]

bytestring/apple/src/ByteStringApple.kt

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2017-2024 JetBrains s.r.o. and respective authors and developers.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the LICENCE file.
+ */
+
+package kotlinx.io.bytestring
+
+import kotlinx.cinterop.*
+import kotlinx.io.bytestring.unsafe.UnsafeByteStringApi
+import kotlinx.io.bytestring.unsafe.UnsafeByteStringOperations
+import platform.Foundation.NSData
+import platform.Foundation.create
+
+/**
+ * Returns a new [NSData] instance initialized with bytes copied from [this] ByteString.
+ *
+ * @sample kotlinx.io.bytestring.samples.ByteStringSamplesApple.nsDataConversion
+ */
+@OptIn(UnsafeNumber::class, BetaInteropApi::class, ExperimentalForeignApi::class)
+public fun ByteString.toNSData(): NSData {
+    if (isEmpty()) {
+        return NSData()
+    }
+    val data = getBackingArrayReference()
+    return data.usePinned {
+        NSData.create(bytes = it.addressOf(0), length = data.size.convert())
+    }
+}
+
+/**
+ * Returns a new [ByteString] holding data copied from [this] NSData.
+ *
+ * @sample kotlinx.io.bytestring.samples.ByteStringSamplesApple.nsDataConversion
+ */
+@OptIn(ExperimentalForeignApi::class, UnsafeNumber::class, UnsafeByteStringApi::class)
+public fun NSData.toByteString(): ByteString {
+    val l = length.toLong()
+    if (l == 0L) {
+        return ByteString.EMPTY
+    }
+    if (l > Int.MAX_VALUE) {
+        throw IllegalArgumentException("NSData content is to long to read as byte array: $l")
+    }
+    return UnsafeByteStringOperations.wrapUnsafe(
+        bytes!!.readBytes(l.toInt())
+    )
+}

bytestring/apple/test/ByteStringAppleTest.kt

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2017-2024 JetBrains s.r.o. and respective authors and developers.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the LICENCE file.
+ */
+
+package kotlinx.io.bytestring
+
+import kotlinx.cinterop.*
+import kotlinx.io.bytestring.unsafe.UnsafeByteStringApi
+import kotlinx.io.bytestring.unsafe.UnsafeByteStringOperations
+import platform.Foundation.NSData
+import platform.Foundation.create
+import platform.posix.memset
+import kotlin.io.encoding.Base64
+import kotlin.io.encoding.ExperimentalEncodingApi
+import kotlin.test.*
+
+@OptIn(UnsafeNumber::class)
+class ByteStringAppleTest {
+    @OptIn(ExperimentalForeignApi::class)
+    @Test
+    fun toNSData() {
+        val emptyData = ByteString().toNSData()
+        assertEquals(0u, emptyData.length)
+
+        val copy = ByteString(0, 1, 2, 3, 4, 5).toNSData()
+        assertContentEquals(byteArrayOf(0, 1, 2, 3, 4, 5), copy.bytes!!.readBytes(copy.length.convert()))
+    }
+
+    @OptIn(BetaInteropApi::class, ExperimentalEncodingApi::class)
+    @Test
+    fun fromNSData() {
+        assertTrue(NSData().toByteString().isEmpty())
+        val src = NSData.create(
+            base64EncodedString = Base64.Default.encode(byteArrayOf(0, 1, 2, 3, 4, 5)),
+            options = 0u
+        )!!
+        val copy = src.toByteString()
+        assertContentEquals(byteArrayOf(0, 1, 2, 3, 4, 5), copy.toByteArray())
+    }
+
+    @OptIn(UnsafeByteStringApi::class, ExperimentalForeignApi::class)
+    @Test
+    fun toNSDataDataIntegrity() {
+        val mutableArray = byteArrayOf(0, 0, 0, 0, 0, 0)
+        // Don't try that at home, kids!
+        val cursedString = UnsafeByteStringOperations.wrapUnsafe(mutableArray)
+        val nsData = cursedString.toNSData()
+
+        mutableArray.fill(42)
+        // NSData should hold a copy
+        assertContentEquals(ByteArray(6), nsData.bytes!!.readBytes(6))
+    }
+
+    @OptIn(ExperimentalForeignApi::class, BetaInteropApi::class)
+    @Test
+    fun fromNSDataIntegrity() = memScoped {
+        val length = 6
+        val data = allocArray<ByteVar>(length)
+        memset(data, 0, length.convert())
+
+        val cursedData = NSData.create(
+            bytesNoCopy = data, length = length.convert(),
+            freeWhenDone = false
+        )
+
+        val byteString = cursedData.toByteString()
+        memset(data, 42, length.convert())
+
+        assertContentEquals(ByteArray(length), byteString.toByteArray())
+    }
+}

bytestring/apple/test/samples/samplesApple.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2017-2024 JetBrains s.r.o. and respective authors and developers.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the LICENCE file.
+ */
+
+package kotlinx.io.bytestring.samples
+
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.UnsafeNumber
+import kotlinx.io.bytestring.*
+import platform.Foundation.*
+import kotlin.test.*
+
+class ByteStringSamplesApple {
+    @OptIn(UnsafeNumber::class, ExperimentalForeignApi::class, ExperimentalStdlibApi::class)
+    @Test
+    fun nsDataConversion() {
+        val originalByteString: ByteString = "Compress me, please!".encodeToByteString()
+
+        val compressedNSData: NSData = originalByteString.toNSData().compressedDataUsingAlgorithm(
+            algorithm = NSDataCompressionAlgorithmZlib,
+            error = null
+        )!!
+
+        val compressedByteString: ByteString = compressedNSData.toByteString()
+        assertEquals("73cecf2d284a2d2e56c84dd55128c8494d2c4e550400", compressedByteString.toHexString())
+        // If there's no zlib-flate on your path, you can test it using:
+        // zlib.decompress(binascii.unhexlify("73cecf2d284a2d2e56c84dd55128c8494d2c4e550400"), -15)
+    }
+}