Add wav header file in kotlin

Author: lemcoder

core/src/commonMain/kotlin/pl/lemanski/pandamidi/io/wav/WavFileHeader.kt

@@ -0,0 +1,32 @@
+package pl.lemanski.pandamidi.io.wav
+
+data class WavFileHeader(
+    val chunkID: String = "RIFF",
+    val chunkSize: UInt,
+    val format: String = "WAVE",
+    val subchunk1ID: String = "fmt ",
+    val subchunk1Size: UInt = 16u,
+    val audioFormat: UShort = 3u, // IEEE float
+    val numChannels: UShort,
+    val sampleRate: UInt,
+    val byteRate: UInt,
+    val blockAlign: UShort,
+    val bitsPerSample: UShort = 32u,
+    val subchunk2ID: String = "data",
+    val subchunk2Size: UInt
+) {
+    companion object {
+        fun write(sampleRate: UInt, numSamples: UInt, numChannels: UShort): WavFileHeader {
+            return WavFileHeader(
+                chunkSize = 36u + numSamples * numChannels * Float.SIZE_BYTES.toUInt(),
+                numChannels = numChannels,
+                sampleRate = sampleRate,
+                byteRate = sampleRate * numChannels * Float.SIZE_BYTES.toUInt(),
+                blockAlign = (numChannels * Float.SIZE_BYTES.toUInt()).toUShort(),
+                subchunk2Size = numSamples * numChannels * Float.SIZE_BYTES.toUInt()
+            )
+        }
+    }
+}
+
+expect fun WavFileHeader.toByteArray(): ByteArray

core/src/commonTest/kotlin/pl/lemanski/pandamidi/io/wav/WavFileHeaderTest.kt

@@ -0,0 +1,22 @@
+package pl.lemanski.pandamidi.io.wav
+
+import kotlin.test.DefaultAsserter.assertEquals
+import kotlin.test.Test
+
+class WavFileHeaderTest {
+    @OptIn(ExperimentalStdlibApi::class)
+    @Test
+    fun should_write_correct_bytes_for_empty_file_header() {
+        val wavFileHex = WavFileHeader.write(44100u, 0u, 2u).toByteArray().toHexString().uppercase()
+        val expectedHex = "524946462400000057415645666d7420100000000300020044ac000020620500080020006461746100000000".uppercase()
+        assertEquals("", expectedHex, wavFileHex)
+    }
+
+    @OptIn(ExperimentalStdlibApi::class)
+    @Test
+    fun should_write_correct_bytes_for_non_empty_file_header() {
+        val wavFileHex = WavFileHeader.write(44100u, 1024u, 2u).toByteArray().toHexString().uppercase()
+        val expectedHex = "524946462420000057415645666D7420100000000300020044AC000020620500080020006461746100200000".uppercase()
+        assertEquals("", expectedHex, wavFileHex)
+    }
+}

core/src/mingwX64Main/kotlin/pl/lemanski/pandamidi/io/wav/WavFileHeader.mingwX64.kt

@@ -0,0 +1,56 @@
+package pl.lemanski.pandamidi.io.wav
+
+import kotlinx.cinterop.ByteVar
+import kotlinx.cinterop.ByteVarOf
+import kotlinx.cinterop.CPointer
+import kotlinx.cinterop.CVariable
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.UIntVar
+import kotlinx.cinterop.UIntVarOf
+import kotlinx.cinterop.UShortVar
+import kotlinx.cinterop.addressOf
+import kotlinx.cinterop.cstr
+import kotlinx.cinterop.memScoped
+import kotlinx.cinterop.pin
+import kotlinx.cinterop.plus
+import kotlinx.cinterop.pointed
+import kotlinx.cinterop.reinterpret
+import kotlinx.cinterop.value
+import platform.posix.memcpy
+
+@OptIn(ExperimentalForeignApi::class)
+actual fun WavFileHeader.toByteArray(): ByteArray {
+    val byteArray = ByteArray(44)
+
+    memScoped {
+        val buffer = byteArray.pin().addressOf(0).reinterpret<ByteVar>()
+
+        memcpy(buffer, chunkID.cstr.ptr, 4u)
+        buffer.setUIntValueAt(4, chunkSize)
+        memcpy(buffer.plus(8), format.cstr.ptr, 4u)
+        memcpy(buffer.plus(12), subchunk1ID.cstr.ptr, 4u)
+        buffer.setUIntValueAt(16, subchunk1Size)
+        buffer.setUShortValueAt(20, audioFormat)
+        buffer.setUShortValueAt(22, numChannels)
+        buffer.setUIntValueAt(24, sampleRate)
+        buffer.setUIntValueAt(28, byteRate)
+        buffer.setUShortValueAt(32, blockAlign)
+        buffer.setUShortValueAt(34, bitsPerSample)
+        memcpy(buffer.plus(36), subchunk2ID.cstr.ptr, 4u)
+        buffer.setUIntValueAt(40, subchunk2Size)
+    }
+
+    return byteArray
+}
+
+@OptIn(ExperimentalForeignApi::class)
+private fun <T : ByteVarOf<*>> CPointer<T>.setUIntValueAt(index: Int, value: UInt): Int {
+    this.plus(index)?.reinterpret<UIntVar>()?.pointed?.let { it.value = value } ?: return -1
+    return 0
+}
+
+@OptIn(ExperimentalForeignApi::class)
+private fun <T : ByteVarOf<*>> CPointer<T>.setUShortValueAt(index: Int, value: UShort): Int {
+    this.plus(index)?.reinterpret<UShortVar>()?.pointed?.let { it.value = value } ?: return -1
+    return 0
+}