feat: Add outer header option (#183)

tinypass/src/commonMain/kotlin/io/spherelabs/crypto/tinypass/database/header/OuterHeaderOption.kt

@@ -0,0 +1,41 @@
+package io.spherelabs.crypto.tinypass.database.header
+
+import io.spherelabs.crypto.tinypass.database.signature.Signature
+import okio.Buffer
+import okio.BufferedSink
+
+data class OuterHeaderOption(
+    val signature: Signature,
+    val version: Version,
+    val cipherId: CipherId,
+    val compressionFlags: CompressionFlags
+) {
+    fun serialize(sink: BufferedSink) {
+        signature.serialize(sink)
+        version.serialize(sink)
+
+        sink.writeByte(CIPHER_ID)
+        sink.writeIntLe(16)
+        val bytes = Buffer().apply {
+            writeLong(cipherId.uuid.mostSignificantBits)
+            writeLong(cipherId.uuid.leastSignificantBits)
+        }
+        sink.write(bytes.readByteArray())
+
+        sink.writeByte(OuterHeader.COMPRESSION)
+        sink.writeIntLe(Int.SIZE_BYTES)
+        sink.writeIntLe(compressionFlags.ordinal)
+    }
+
+    companion object {
+        val Default = OuterHeaderOption(
+            signature = Signature.Default,
+            version = Version(4, 1),
+            compressionFlags = CompressionFlags.GZip,
+            cipherId = CipherId.Aes,
+        )
+
+        const val CIPHER_ID = 1
+        const val COMPRESSION = 2
+    }
+}