June 2018 Update

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))
+}

Task/Bitwise-IO/Python/bitwise-io-1.py

@@ -4,10 +4,16 @@ class BitWriter(object):
         self.bcount = 0
         self.out = f
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.flush()
+
     def __del__(self):
         try:
             self.flush()
-        except ValueError:   # I/O operation on closed file
+        except ValueError:   # I/O operation on closed file.
             pass
 
     def _writebit(self, bit):
@@ -35,6 +41,12 @@ class BitReader(object):
         self.bcount = 0
         self.read = 0
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        pass
+
     def _readbit(self):
         if not self.bcount:
             a = self.input.read(1)
@@ -56,22 +68,22 @@ class BitReader(object):
 if __name__ == '__main__':
     import os
     import sys
-    # determine module name from this file's name and import it
+    # Determine this module's name from it's file name and import it.
     module_name = os.path.splitext(os.path.basename(__file__))[0]
     bitio = __import__(module_name)
 
     with open('bitio_test.dat', 'wb') as outfile:
-        writer = bitio.BitWriter(outfile)
-        chars = '12345abcde'
-        for ch in chars:
-            writer.writebits(ord(ch), 7)
+        with bitio.BitWriter(outfile) as writer:
+            chars = '12345abcde'
+            for ch in chars:
+                writer.writebits(ord(ch), 7)
 
     with open('bitio_test.dat', 'rb') as infile:
-        reader = bitio.BitReader(infile)
-        chars = []
-        while True:
-            x = reader.readbits(7)
-            if reader.read == 0:
-                break
-            chars.append(chr(x))
-        print(''.join(chars))
+        with bitio.BitReader(infile) as reader:
+            chars = []
+            while True:
+                x = reader.readbits(7)
+                if not reader.read:  # End-of-file?
+                    break
+                chars.append(chr(x))
+            print(''.join(chars))

Task/Bitwise-IO/Python/bitwise-io-2.py

@@ -6,3 +6,4 @@ c = sys.stdin.read(1)
 while len(c) > 0:
     o.writebits(ord(c), 7)
     c = sys.stdin.read(1)
+o.flush()