Refactor Utilities

This refactors the utilities which at the moment is only `RandomAccessDocument`.

app/src/main/java/emu/skyline/utility/RandomAccessDocument.kt

@@ -10,44 +10,84 @@ import android.os.ParcelFileDescriptor
 import androidx.documentfile.provider.DocumentFile
 import java.nio.ByteBuffer
 
+/**
+ * This is made as a parallel to [java.io.RandomAccessFile] for [DocumentFile]s
+ *
+ * @param parcelFileDescriptor The file descriptor for the [DocumentFile]
+ */
 class RandomAccessDocument(private var parcelFileDescriptor: ParcelFileDescriptor) {
-    constructor(context: Context, file: DocumentFile) : this(context.contentResolver.openFileDescriptor(file.uri, "r")!!)
-
+    /**
+     * The actual file descriptor for the [DocumentFile] as an [FileDescriptor] object
+     */
     private val fileDescriptor = parcelFileDescriptor.fileDescriptor
+
+    /**
+     * The current position of where the file is being read
+     */
     private var position: Long = 0
 
+    /**
+     * The constructor sets [parcelFileDescriptor] by opening a read-only FD to [file]
+     */
+    constructor(context: Context, file: DocumentFile) : this(context.contentResolver.openFileDescriptor(file.uri, "r")!!)
+
+    /**
+     * This reads in as many as possible bytes into [array] (Generally [array].size)
+     *
+     * @return The amount of bytes read from the file
+     */
     fun read(array: ByteArray): Int {
         val bytesRead = android.system.Os.pread(fileDescriptor, array, 0, array.size, position)
         position += bytesRead
         return bytesRead
     }
 
+    /**
+     * This reads in as many as possible bytes into [buffer] (Generally [buffer].array().size)
+     *
+     * @return The amount of bytes read from the file
+     */
     fun read(buffer: ByteBuffer): Int {
         val bytesRead = android.system.Os.pread(fileDescriptor, buffer.array(), 0, buffer.array().size, position)
         position += bytesRead
         return bytesRead
     }
 
+    /**
+     * This returns a single [Long] from the file at the current [position]
+     */
     fun readLong(): Long {
         val buffer: ByteBuffer = ByteBuffer.allocate(Long.SIZE_BYTES)
         read(buffer)
         return buffer.long
     }
 
+    /**
+     * This returns a single [Int] from the file at the current [position]
+     */
     fun readInt(): Int {
         val buffer: ByteBuffer = ByteBuffer.allocate(Int.SIZE_BYTES)
         read(buffer)
         return buffer.int
     }
 
+    /**
+     * This sets [RandomAccessDocument.position] to the supplied [position]
+     */
     fun seek(position: Long) {
         this.position = position
     }
 
-    fun skipBytes(position: Long) {
-        this.position += position
+    /**
+     * This increments [position] by [amount]
+     */
+    fun skipBytes(amount: Long) {
+        this.position += amount
     }
 
+    /**
+     * This closes [parcelFileDescriptor] so this class doesn't leak file descriptors
+     */
     fun close() {
         parcelFileDescriptor.close()
     }