Data commit

Task/Bitwise-IO/Kotlin/bitwise-io.kotlin

@@ -0,0 +1,84 @@
+// version 1.2.31
+
+import java.io.File
+
+class BitFilter(val f: File, var accu: Int = 0, var bits: Int = 0) {
+
+    private val bw = f.bufferedWriter()
+    private val br = f.bufferedReader()
+
+    fun write(buf: ByteArray, start: Int, _nBits: Int, _shift: Int) {
+        var nBits = _nBits
+        var index = start + _shift / 8
+        var shift = _shift % 8
+
+        while (nBits != 0 || bits >= 8) {
+            while (bits >= 8) {
+                bits -= 8
+                bw.write(accu ushr bits)
+                accu = accu and ((1 shl bits) - 1)
+            }
+            while (bits < 8 && nBits != 0) {
+                val b = buf[index].toInt()
+                accu = (accu shl 1) or (((128 ushr shift) and b) ushr (7 - shift))
+                nBits--
+                bits++
+                if (++shift == 8) { shift = 0; index++ }
+            }
+        }
+    }
+
+    fun read(buf: ByteArray, start: Int, _nBits: Int, _shift: Int) {
+        var nBits = _nBits
+        var index = start + _shift / 8
+        var shift = _shift % 8
+
+        while (nBits != 0) {
+            while (bits != 0 && nBits != 0) {
+                val mask = 128 ushr shift
+                if ((accu and (1 shl (bits - 1))) != 0)
+                    buf[index] = (buf[index].toInt() or mask).toByte()
+                else
+                    buf[index] = (buf[index].toInt() and mask.inv()).toByte()
+                nBits--
+                bits--
+                if (++shift >= 8) { shift = 0; index++ }
+            }
+            if (nBits == 0) break
+            accu = (accu shl 8) or br.read()
+            bits += 8
+        }
+    }
+
+    fun closeWriter() {
+        if (bits != 0) {
+            accu = (accu shl (8 - bits))
+            bw.write(accu)
+        }
+        bw.close()
+        accu = 0
+        bits = 0
+    }
+
+    fun closeReader() {
+        br.close()
+        accu = 0
+        bits = 0
+    }
+}
+
+fun main(args: Array<String>) {
+    val s = "abcdefghijk".toByteArray(Charsets.UTF_8)
+    val f = File("test.bin")
+    val bf = BitFilter(f)
+
+    /* for each byte in s, write 7 bits skipping 1 */
+    for (i in 0 until s.size) bf.write(s, i, 7, 1)
+    bf.closeWriter()
+
+    /* read 7 bits and expand to each byte of s2 skipping 1 bit */
+    val s2 = ByteArray(s.size)
+    for (i in 0 until s2.size) bf.read(s2, i, 7, 1)
+    bf.closeReader()
+    println(String(s2, Charsets.UTF_8))
+}