Add functions to format ByteArray as bit string

Author: tobiasvonderheidt

app/src/main/java/org/vonderheidt/hips/utils/Format.kt

@@ -0,0 +1,38 @@
+package org.vonderheidt.hips.utils
+
+/**
+ * Object (i.e. singleton class) that represents various functions for string formatting.
+ */
+object Format {
+    /**
+     * Function to format a ByteArray as a bit string.
+     *
+     * @param byteArray A ByteArray.
+     * @return The bit string.
+     */
+    fun asBitString(byteArray: ByteArray): String {
+        val bitString = byteArray.joinToString(separator = "") { byte ->
+            String.format(format = "%8s", Integer.toBinaryString(byte.toInt() and 0xFF)).replace(oldChar = ' ', newChar = '0')
+        }
+
+        return bitString
+    }
+
+    /**
+     * Function to reverse formatting of a ByteArray as a bit string (i.e. to reverse `Format.asBitString(ByteArray)`).
+     *
+     * @param bitString A bit string.
+     * @return The ByteArray.
+     */
+    fun asByteArray(bitString: String): ByteArray {
+        // Don't assert string length to be a multiple of 8, causes error in Huffman encoding with 3 bits/token
+        val byteArray = ByteArray(size = bitString.length / 8) { index ->
+            val byteString = bitString.substring(startIndex = index * 8, endIndex = (index + 1) * 8)
+            val byte = byteString.toInt(radix = 2).toByte()
+
+            byte
+        }
+
+        return byteArray
+    }
+}