ADDED   src/0dev.org/mtf/mtf.go
Index: src/0dev.org/mtf/mtf.go
==================================================================
--- /dev/null
+++ src/0dev.org/mtf/mtf.go
@@ -0,0 +1,123 @@
+// Package mtf provides a move-to-front encoder and decoder implementations
+package mtf
+
+import (
+	"io"
+)
+
+// A static table with the initial condition for the mtf algorithm
+var initial [256]byte = [...]byte{
+	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
+	16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+	32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
+	48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
+	64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
+	80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,
+	96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
+	112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
+	128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143,
+	144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159,
+	160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175,
+	176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191,
+	192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,
+	208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223,
+	224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239,
+	240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255,
+}
+
+type context struct {
+	table [256]byte
+}
+
+// Returns an MTF encoder over the provided io.Writer
+func Encoder(writer io.Writer) io.Writer {
+	var enc encoder
+	enc.table = initial
+	enc.target = writer
+	return &enc
+}
+
+type encoder struct {
+	context
+	target io.Writer
+}
+
+func (c *encoder) Write(data []byte) (int, error) {
+	var (
+		dataLength int    = len(data)
+		buffer     []byte = make([]byte, dataLength)
+	)
+
+	// io.Write must not modify the passed data in any way
+	// TODO - check sync.Pool or a local free-list for amortizing buffers
+	// TODO - use a buffer with a fixed max size to avoid OOM conditions
+
+	// Loop over the input data
+	for index, value := range data {
+
+		// Shortcut for sequential, equal values
+		if c.table[0] == value {
+			buffer[index] = 0
+			continue
+		}
+
+		// Loop over the MTF table
+		for j := byte(1); j != 0; j++ {
+			if c.table[j] == value {
+				// Output the value
+				buffer[index] = j
+
+				// Shift the table
+				copy(c.table[1:j+1], c.table[0:j])
+
+				// Restore the value in front and break
+				c.table[0] = value
+				break
+			}
+		}
+	}
+
+	return c.target.Write(buffer)
+}
+
+// Returns an MTF decoder over the provided io.Writer
+func Decoder(reader io.Reader) io.Reader {
+	var dec decoder
+	dec.table = initial
+	dec.source = reader
+	return &dec
+}
+
+type decoder struct {
+	context
+	source io.Reader
+}
+
+func (c *decoder) Read(output []byte) (int, error) {
+	var (
+		count    int
+		err      error
+		position byte
+	)
+
+	// Read from the source and decode in place
+	count, err = c.source.Read(output)
+	for i := 0; i < count; i++ {
+		position = output[i]
+
+		// Shortcut for sequential, equal values
+		if position == 0 {
+			output[i] = c.table[0]
+			continue
+		}
+
+		// Output the value
+		output[i] = c.table[position]
+
+		// Shift the table and restore the value in front
+		copy(c.table[1:position+1], c.table[0:position])
+		c.table[0] = output[i]
+	}
+
+	return count, err
+}

ADDED   src/0dev.org/mtf/mtf_test.go
Index: src/0dev.org/mtf/mtf_test.go
==================================================================
--- /dev/null
+++ src/0dev.org/mtf/mtf_test.go
@@ -0,0 +1,61 @@
+package mtf
+
+import (
+	diff "0dev.org/diff"
+	"bytes"
+	"io"
+	"testing"
+)
+
+func TestEncoder(t *testing.T) {
+	var (
+		input    []byte = []byte{1, 1, 0, 0}
+		expected []byte = []byte{1, 0, 1, 0}
+
+		buffer  bytes.Buffer
+		encoder io.Writer = Encoder(&buffer)
+	)
+
+	count, err := encoder.Write(input)
+	if count != len(input) {
+		t.Error("Unexpected write count from encoder", count)
+	}
+	if err != nil {
+		t.Error("Unexpected write error from encoder", err)
+	}
+
+	output := buffer.Bytes()
+
+	// Diff the output against the expected result
+	delta := diff.Diff(diff.D{Len1: len(expected), Len2: len(output),
+		EqualFunc: func(i, j int) bool { return expected[i] == output[j] }})
+	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
+		t.Error("Differences detected ", delta)
+	}
+}
+
+func TestDecoder(t *testing.T) {
+	var (
+		input    []byte = []byte{1, 0, 1, 0}
+		expected []byte = []byte{1, 1, 0, 0}
+		output   []byte = make([]byte, 4)
+
+		reader  *bytes.Reader = bytes.NewReader(input)
+		decoder io.Reader     = Decoder(reader)
+	)
+
+	count, err := decoder.Read(output)
+	if count != len(output) {
+		t.Error("Unexpected read count from decoder", count)
+	}
+	if err != nil {
+		t.Error("Unexpected read error from decoder", err)
+	}
+
+	// Diff the output against the expected result
+	delta := diff.Diff(diff.D{Len1: len(expected), Len2: len(output),
+		EqualFunc: func(i, j int) bool { return expected[i] == output[j] }})
+	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
+		t.Error("Differences detected ", delta)
+	}
+}