Implement streaming API

src/commonMain/kotlin/com/infendro/hash/util/Buffer.kt

@@ -0,0 +1,46 @@
+package com.infendro.hash.util
+
+import com.infendro.bytes.ByteOrder
+import com.infendro.bytes.ByteOrder.BIG_ENDIAN
+import com.infendro.bytes.int.copyInto
+import com.infendro.bytes.long.copyInto
+
+internal class Buffer(val size: Int) {
+    val value = ByteArray(size)
+    var offset = 0
+
+    val free: Int
+        get() = size - offset
+
+    fun isEmpty(): Boolean = offset == 0
+    fun isNotEmpty(): Boolean = !isEmpty()
+    fun isFull(): Boolean = offset == size
+
+    fun reset() {
+        value.fill(0x00)
+        offset = 0
+    }
+
+    fun jumpTo(offset: Int) {
+        this.offset = offset
+    }
+
+    fun append(byte: Byte) {
+        value[offset++] = byte
+    }
+
+    fun append(bytes: ByteArray, startIndex: Int = 0, endIndex: Int = bytes.size) {
+        bytes.copyInto(value, offset, startIndex, endIndex)
+        offset += (endIndex - startIndex)
+    }
+
+    fun append(n: Int, order: ByteOrder = BIG_ENDIAN) {
+        n.copyInto(value, offset, order = order)
+        offset += 4
+    }
+
+    fun append(n: Long, order: ByteOrder = BIG_ENDIAN) {
+        n.copyInto(value, offset, order = order)
+        offset += 8
+    }
+}