Add redundancy factor to encoder

encode.go

@@ -9,13 +9,15 @@ import (
 
 // Encoder represents protocol encoder.
 type Encoder struct {
-	chunkLen int
+	chunkLen         int
+	redundancyFactor float64
 }
 
 // NewEncoder creates and inits a new encoder for the given chunk length.
 func NewEncoder(n int) *Encoder {
 	return &Encoder{
-		chunkLen: n,
+		chunkLen:         n,
+		redundancyFactor: 1.5,
 	}
 }
 
@@ -30,7 +32,7 @@ func (e *Encoder) Encode(str string) ([]string, error) {
 	codec := fountain.NewLubyCodec(numChunks, rand.New(fountain.NewMersenneTwister(200)), solitonDistribution(numChunks))
 
 	var msg = []byte(str) // copy of str, as EncodeLTBlock is destructive to msg
-	idsToEncode := ids(numChunks)
+	idsToEncode := ids(int(float64(numChunks) * e.redundancyFactor))
 	lubyBlocks := fountain.EncodeLTBlocks(msg, idsToEncode, codec)
 
 	// TODO(divan): use sync.Pool as this probably will be used many times
@@ -41,6 +43,11 @@ func (e *Encoder) Encode(str string) ([]string, error) {
 	return ret, nil
 }
 
+// SetRedundancyFactor changes the value of redundancy factor.
+func (e *Encoder) SetRedundancyFactor(rf float64) {
+	e.redundancyFactor = rf
+}
+
 func (e *Encoder) frame(blockCode int64, total int, data []byte) string {
 	return fmt.Sprintf("%d/%d/%d|%s", blockCode, e.chunkLen, total, string(data))
 }

fountain.go

@@ -22,9 +22,8 @@ func solitonDistribution(n int) []float64 {
 
 // ids create slice with IDs for 0..n values.
 func ids(n int) []int64 {
-	N := n + n/2
-	ids := make([]int64, N)
-	for i := int64(0); i < int64(N); i++ {
+	ids := make([]int64, n)
+	for i := int64(0); i < int64(n); i++ {
 		ids[i] = i
 	}
 	return ids