包名重构

protocol/bt/peer/message/msg_bitfield.go

@@ -0,0 +1,60 @@
+package message
+
+// bitfield: <len=0001+X><id=5><bitfield>
+type Bitfield struct {
+	*Message
+	payload []byte
+}
+
+func NewBitfield(payload []byte) *Bitfield {
+	return &Bitfield{
+		Message: &Message{
+			Length: uint32(len(payload) + 1),
+			ID:     IdBitfield,
+		},
+		payload: payload,
+	}
+}
+
+func (b *Bitfield) Encode() []byte {
+	return append(b.Message.Encode(), b.payload...)
+}
+
+func (b *Bitfield) Decode(buf []byte) Serialize {
+	b.Message = &Message{}
+	b.Message.Decode(buf)
+	b.payload = buf[5:]
+	return b
+}
+
+// 某个分片是否下载完成
+func (b *Bitfield) IsComplete(i int) bool {
+	index := i / 8
+	if index >= len(b.payload) {
+		return false
+	}
+	return b.payload[index]&(1<<(7-i%8)) > 0
+}
+
+// 给定一组分片下载状态，计算出当前peer能提供下载的分片下标
+func (b *Bitfield) Have(pieces []bool) []int {
+	arr := make([]int, 0)
+	length := len(pieces) / 8
+	if len(pieces)%8 != 0 {
+		length++
+	}
+
+	for i := 0; i < length; i++ {
+		for j := 0; j < 8; j++ {
+			index := i*8 + j
+			// 如果此分片在本地还未下载，检查peer是否能提供该分片下载
+			if index < len(pieces) &&
+				!pieces[index] &&
+				i < len(b.payload) &&
+				b.payload[i]&(1<<(7-j)) > 0 {
+				arr = append(arr, index)
+			}
+		}
+	}
+	return arr
+}