ADDED   src/0dev.org/commands/short/main.go
Index: src/0dev.org/commands/short/main.go
==================================================================
--- src/0dev.org/commands/short/main.go
+++ src/0dev.org/commands/short/main.go
@@ -0,0 +1,189 @@
+package main
+
+import (
+	iou "0dev.org/ioutil"
+	"fmt"
+	"io"
+	"os"
+	"sort"
+)
+
+func main() {
+	f, err := os.Open(os.Args[1])
+	if err != nil {
+		os.Stderr.WriteString("Unable to open input file. " + err.Error())
+		os.Exit(1)
+	}
+
+	pairs, symbols := analyze(f)
+
+	rec := recommend(pairs, symbols)
+	fmt.Println(*rec)
+}
+
+type recommendation struct {
+	p2s map[uint16]byte
+	s2p map[byte]uint16
+}
+
+func apply(rec *recommendation, reader io.Reader) {
+	symbolReader := iou.SizedReader(iou.ReaderFunc(func(output []byte) (int, error) {
+		for i := 0; i < len(output)-1; i++ {
+			// Read a byte from the underlying reader
+			count, err := reader.Read(output[i : i+1])
+			if err != nil || count != 1 {
+				return i + count, err
+			}
+
+			// Convert the byte to a pair if there is a mapping for it
+			if pair, ok := rec.s2p[output[i]]; ok {
+				output[i] = byte(pair >> 8) // extract the high byte from the pair
+				i++
+				output[i] = byte(pair) // leave only the low byte from the pair
+			}
+		}
+	}), 2)
+}
+
+func recommend(pairs pairSlice, symbols symbolSlice) *recommendation {
+	var (
+		rec         recommendation
+		pairsLength = len(pairs)
+	)
+
+	rec.p2s = make(map[uint16]byte) // Store pair to symbol mappings
+	rec.s2p = make(map[byte]uint16) // Store symbol to pair mappings
+
+	for i := 0; i < pairsLength; i++ {
+		currentPair := pairs[i]
+
+		// Termination condition for when we are out of symbols
+		if len(symbols) == 0 {
+			break
+		}
+
+		gain := currentPair.count - 4 // 4 bytes for the default header
+		currentSymbol := symbols[0]
+
+		if currentSymbol.count == 0 {
+			// Termination condition for possitive compression effect
+			if gain <= 0 {
+				break
+			}
+
+			// Mark the recommendation and proceed with the next pair
+			rec.p2s[currentPair.value] = currentSymbol.value
+			continue
+		} else { // if the current symbol is present in the data
+			// Decrease the gain by a symbol -> p`, p -> symbol replacement
+			gain -= 2                   // Additional 2 bytes for the more complex header
+			gain -= currentSymbol.count // Account for swaping the symbol to a pair in order to free it
+
+			// Termination condition for possitive compression effect
+			if gain <= 0 {
+				break
+			}
+
+			// Mark this symbol for replacement by the last unused pair
+			rec.s2p[currentSymbol.value] = pairs[pairsLength-1].value
+			pairsLength--
+
+			// Mark the current pair for replacement by the current symbol
+			rec.p2s[currentPair.value] = currentSymbol.value
+		}
+	}
+
+	return &rec
+}
+
+// Reads the provided input and returns information about the available byte pair and used symbols
+func analyze(reader io.Reader) (pairSlice, symbolSlice) {
+	var (
+		current uint16   // Stores a pair of bytes in it's high and low bits
+		buffer  []byte   = make([]byte, 1)
+		pairs   []uint64 = make([]uint64, 65536) // all possible pairs, 512kb
+		symbols []uint64 = make([]uint64, 256)   // all possible characters, 2kb
+	)
+
+	// Read the first byte and store in the low bits of the current pair
+	if c, err := reader.Read(buffer); err != nil || c != 1 {
+		os.Stderr.WriteString("Error reading input.")
+		os.Exit(1)
+	}
+	current = uint16(buffer[0])
+
+	// Read all of the data and note the counts of bytes and byte pairs
+	io.Copy(iou.WriterFunc(func(data []byte) (int, error) {
+		for _, value := range data {
+			// Store pairs frequency
+			current <<= 8            // Shift the previous byte from low to high
+			current |= uint16(value) // Add the current byte to low
+			pairs[current]++
+
+			// Store bytes frequency
+			symbols[value]++
+		}
+		return len(data), nil
+	}), reader)
+
+	// Extract and sort all byte pairs
+	availablePairs := make(pairSlice, 0)
+	for index, value := range pairs {
+		availablePairs = append(availablePairs, pair{value: uint16(index), count: value})
+	}
+	sort.Sort(availablePairs)
+
+	// Extract and sort all symbols (including the ones with zero counts)
+	allSymbols := make(symbolSlice, 0)
+	for index, value := range symbols {
+		allSymbols = append(allSymbols, symbol{value: byte(index), count: value})
+	}
+	sort.Sort(allSymbols)
+
+	return availablePairs, allSymbols
+}
+
+type pair struct {
+	value uint16
+	count uint64
+}
+
+type symbol struct {
+	value byte
+	count uint64
+}
+
+// Implements fmt.Stringer, used for debugging
+func (p pair) String() string {
+	return fmt.Sprintf("[ %d %d (%d) ]", (p.value >> 8), ((p.value << 8) >> 8), p.count)
+}
+
+type pairSlice []pair
+
+func (s pairSlice) Len() int {
+	return len(s)
+}
+
+func (s pairSlice) Less(i, j int) bool {
+	// Sort in descending order
+	return s[i].count > s[j].count
+}
+
+func (s pairSlice) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+type symbolSlice []symbol
+
+func (s symbolSlice) Len() int {
+	return len(s)
+}
+
+func (s symbolSlice) Less(i, j int) bool {
+	// Sort in ascending order
+	return s[i].count < s[j].count
+}
+
+func (s symbolSlice) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}