Fix Split function with 0 erasure (#234)

Fixes #232

Author: klauspost

leopard.go

@@ -272,6 +272,9 @@ func (r *leopardFF16) Split(data []byte) ([][]byte, error) {
 	if len(data) == 0 {
 		return nil, ErrShortData
 	}
+	if r.totalShards == 1 && len(data)&63 == 0 {
+		return [][]byte{data}, nil
+	}
 	dataLen := len(data)
 	// Calculate number of bytes per data shard.
 	perShard := (len(data) + r.dataShards - 1) / r.dataShards
@@ -295,8 +298,9 @@ func (r *leopardFF16) Split(data []byte) ([][]byte, error) {
 			copyFrom = copyFrom[copy(padding[i], copyFrom):]
 		}
 	} else {
-		for i := dataLen; i < dataLen+r.dataShards; i++ {
-			data[i] = 0
+		zero := data[dataLen : r.totalShards*perShard]
+		for i := range zero {
+			zero[i] = 0
 		}
 	}
 

leopard8.go

@@ -312,6 +312,10 @@ func (r *leopardFF8) Split(data []byte) ([][]byte, error) {
 	if len(data) == 0 {
 		return nil, ErrShortData
 	}
+	if r.totalShards == 1 && len(data)&63 == 0 {
+		return [][]byte{data}, nil
+	}
+
 	dataLen := len(data)
 	// Calculate number of bytes per data shard.
 	perShard := (len(data) + r.dataShards - 1) / r.dataShards
@@ -335,8 +339,9 @@ func (r *leopardFF8) Split(data []byte) ([][]byte, error) {
 			copyFrom = copyFrom[copy(padding[i], copyFrom):]
 		}
 	} else {
-		for i := dataLen; i < dataLen+r.dataShards; i++ {
-			data[i] = 0
+		zero := data[dataLen : r.totalShards*perShard]
+		for i := range zero {
+			zero[i] = 0
 		}
 	}
 

reedsolomon.go

@@ -1551,6 +1551,10 @@ func (r *reedSolomon) Split(data []byte) ([][]byte, error) {
 	if len(data) == 0 {
 		return nil, ErrShortData
 	}
+	if r.totalShards == 1 {
+		return [][]byte{data}, nil
+	}
+
 	dataLen := len(data)
 	// Calculate number of bytes per data shard.
 	perShard := (len(data) + r.dataShards - 1) / r.dataShards
@@ -1574,8 +1578,9 @@ func (r *reedSolomon) Split(data []byte) ([][]byte, error) {
 		}
 		data = data[0 : perShard*fullShards]
 	} else {
-		for i := dataLen; i < dataLen+r.dataShards; i++ {
-			data[i] = 0
+		zero := data[dataLen : r.totalShards*perShard]
+		for i := range zero {
+			zero[i] = 0
 		}
 	}
 

reedsolomon_test.go

@@ -1950,6 +1950,20 @@ func TestNew(t *testing.T) {
 	}
 }
 
+func TestSplitZero(t *testing.T) {
+	data := make([]byte, 512)
+	for _, opts := range testOpts() {
+		ecctest, err := New(1, 0, opts...)
+		if err != nil {
+			t.Fatal(err)
+		}
+		_, err = ecctest.Split(data)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
 // Benchmark 10 data shards and 4 parity shards and 160MB data.
 func BenchmarkSplit10x4x160M(b *testing.B) {
 	benchmarkSplit(b, 10, 4, 160*1024*1024)