finish dec128blk1

decode.go

@@ -1,5 +1,63 @@
 package unibase2n
 
+import (
+	"encoding/binary"
+)
+
 func (bs Base) Decode(data []byte) []byte {
 	return nil
 }
+
+// dec128blk1 for bit 1
+//    len(in)>0, len(in)%16==0, len(out)==len(in)/16
+func dec128blk1(mask uint128be, in, out []byte) {
+	for i := range out {
+		c := i * 16
+		n := readuint128be(in[c : c+16])
+		one := u128one
+		n.subeq(mask)
+		sum := n.and(one)
+		n.shreq(16 - 1)
+		one.shleq(1)
+		sum.oreq(n.and(one))
+		n.shreq(16 - 1)
+		one.shleq(1)
+		sum.oreq(n.and(one))
+		n.shreq(16 - 1)
+		one.shleq(1)
+		sum.oreq(n.and(one))
+		n.shreq(16 - 1)
+		one.shleq(1)
+		sum.oreq(n.and(one))
+		n.shreq(16 - 1)
+		one.shleq(1)
+		sum.oreq(n.and(one))
+		n.shreq(16 - 1)
+		one.shleq(1)
+		sum.oreq(n.and(one))
+		n.shreq(16 - 1)
+		one.shleq(1)
+		sum.oreq(n.and(one))
+		out[i] = uint8(sum.b)
+	}
+}
+
+// dec64blk2 for bit 2
+//    len(in)!=0, len(out)==len(in)/8
+func dec64blk2(mask uint64, in, out []byte) {
+	for i, n := range in {
+		c := i * 8
+		x := (uint64(n)<<42 | uint64(n)<<28 | uint64(n)<<14 | uint64(n)) & 0x00030003_00030003
+		binary.BigEndian.PutUint64(out[c:c+8], x+mask)
+	}
+}
+
+// dec32blk4 for bit 4
+//    len(in)!=0, len(out)==len(in)/4
+func dec32blk4(mask uint32, in, out []byte) {
+	for i, n := range in {
+		c := i * 4
+		x := (uint32(n)<<12 | uint32(n)) & 0x000f000f
+		binary.BigEndian.PutUint32(out[c:c+4], x+mask)
+	}
+}