initial commit

client/wire/varint.go

@@ -0,0 +1,51 @@
+package wire
+
+import (
+	"errors"
+	"io"
+)
+
+// VarIntMaxBytes is the maximum encoded length of a Minecraft VarInt.
+const VarIntMaxBytes = 5
+
+var errVarIntTooBig = errors.New("wire: VarInt exceeds 5 bytes")
+
+// ReadVarInt reads a Minecraft-style VarInt from a byte reader.
+func ReadVarInt(r io.ByteReader) (int, error) {
+	var value, shift int
+	for {
+		b, err := r.ReadByte()
+		if err != nil {
+			return 0, err
+		}
+		value |= int(b&0x7F) << shift
+		if b&0x80 == 0 {
+			return value, nil
+		}
+		shift += 7
+		if shift >= 32 {
+			return 0, errVarIntTooBig
+		}
+	}
+}
+
+// AppendVarInt appends v encoded as a VarInt to dst.
+func AppendVarInt(dst []byte, v int) []byte {
+	u := uint32(v)
+	for u&^uint32(0x7F) != 0 {
+		dst = append(dst, byte(u&0x7F)|0x80)
+		u >>= 7
+	}
+	return append(dst, byte(u))
+}
+
+// VarIntSize returns the encoded byte length of v.
+func VarIntSize(v int) int {
+	n := 1
+	u := uint32(v)
+	for u&^uint32(0x7F) != 0 {
+		u >>= 7
+		n++
+	}
+	return n
+}