Godeps/_workspace/src/gopkg.in/mgo.v2/socket.go
func (socket *mongoSocket) readLoop() {
	p := make([]byte, 36) // 16 from header + 20 from OP_REPLY fixed fields
	s := make([]byte, 4)
	conn := socket.conn // No locking, conn never changes.
	for {
		// XXX Handle timeouts, , etc
		err := fill(conn, p)
		if err != nil {
			socket.kill(err, true)
			return
		}

		totalLen := getInt32(p, 0)
		responseTo := getInt32(p, 8)
		opCode := getInt32(p, 12)

		// Don't use socket.server.Addr here.  socket is not
		// locked and socket.server may go away.
		debugf("Socket %p to %s: got reply (%d bytes)", socket, socket.addr, totalLen)

		_ = totalLen

		if opCode != 1 {
			socket.kill(errors.New("opcode != 1, corrupted data?"), true)
			return
		}

		reply := replyOp{
			flags:     uint32(getInt32(p, 16)),
			cursorId:  getInt64(p, 20),
			firstDoc:  getInt32(p, 28),
			replyDocs: getInt32(p, 32),
		}

		stats.receivedOps(+1)
		stats.receivedDocs(int(reply.replyDocs))

		socket.Lock()
		replyFunc, ok := socket.replyFuncs[uint32(responseTo)]
		if ok {
			delete(socket.replyFuncs, uint32(responseTo))
		}
		socket.Unlock()

		if replyFunc != nil && reply.replyDocs == 0 {
			replyFunc(nil, &reply, -1, nil)
		} else {
			for i := 0; i != int(reply.replyDocs); i++ {
				err := fill(conn, s)
				if err != nil {
					if replyFunc != nil {
						replyFunc(err, nil, -1, nil)
					}
					socket.kill(err, true)
					return
				}

				b := make([]byte, int(getInt32(s, 0)))

				// copy(b, s) in an efficient way.
				b[0] = s[0]
				b[1] = s[1]
				b[2] = s[2]
				b[3] = s[3]

				err = fill(conn, b[4:])
				if err != nil {
					if replyFunc != nil {
						replyFunc(err, nil, -1, nil)
					}
					socket.kill(err, true)
					return
				}

				if globalDebug && globalLogger != nil {
					m := bson.M{}
					if err := bson.Unmarshal(b, m); err == nil {
						debugf("Socket %p to %s: received document: %#v", socket, socket.addr, m)
					}
				}

				if replyFunc != nil {
					replyFunc(nil, &reply, i, b)
				}

				// XXX Do bound checking against totalLen.
			}
		}

		socket.Lock()
		if len(socket.replyFuncs) == 0 {
			// Nothing else to read for now. Disable deadline.
			socket.conn.SetReadDeadline(time.Time{})
		} else {
			socket.updateDeadline(readDeadline)
		}
		socket.Unlock()

		// XXX Do bound checking against totalLen.
	}
}
func (socket *mongoSocket) readLoop() {
	p := make([]byte, 36) // 16 from header + 20 from OP_REPLY fixed fields
	s := make([]byte, 4)
	conn := socket.conn // No locking, conn never changes.
	for {
		// XXX Handle timeouts, , etc
		err := fill(conn, p)
		if err != nil {
			socket.kill(err, true)
			return
		}

		totalLen := getInt32(p, 0)
		responseTo := getInt32(p, 8)
		opCode := getInt32(p, 12)

		// Don't use socket.server.Addr here.  socket is not
		// locked and socket.server may go away.
		debugf("Socket %p to %s: got reply (%d bytes)", socket, socket.addr, totalLen)

		_ = totalLen

		if opCode != 1 {
			socket.kill(errors.New("opcode != 1, corrupted data?"), true)
			return
		}

		reply := replyOp{
			flags:     uint32(getInt32(p, 16)),
			cursorId:  getInt64(p, 20),
			firstDoc:  getInt32(p, 28),
			replyDocs: getInt32(p, 32),
		}

		stats.receivedOps(+1)
		stats.receivedDocs(int(reply.replyDocs))

		socket.Lock()
		replyFunc, ok := socket.replyFuncs[uint32(responseTo)]
		if ok {
			delete(socket.replyFuncs, uint32(responseTo))
		}
		socket.Unlock()

		if replyFunc != nil && reply.replyDocs == 0 {
			replyFunc(nil, &reply, -1, nil)
		} else {
			for i := 0; i != int(reply.replyDocs); i++ {
				err := fill(conn, s)
				if err != nil {
					if replyFunc != nil {
						replyFunc(err, nil, -1, nil)
					}
					socket.kill(err, true)
					return
				}

				b := make([]byte, int(getInt32(s, 0)))

				// copy(b, s) in an efficient way.
				b[0] = s[0]
				b[1] = s[1]
				b[2] = s[2]
				b[3] = s[3]

				err = fill(conn, b[4:])
				if err != nil {
					if replyFunc != nil {
						replyFunc(err, nil, -1, nil)
					}
					socket.kill(err, true)
					return
				}

				if globalDebug && globalLogger != nil {
					m := bson.M{}
					if err := bson.Unmarshal(b, m); err == nil {
						debugf("Socket %p to %s: received document: %#v", socket, socket.addr, m)
					}
				}

				if replyFunc != nil {
					replyFunc(nil, &reply, i, b)
				}

				// XXX Do bound checking against totalLen.
			}
		}

		socket.Lock()
		if len(socket.replyFuncs) == 0 {
			// Nothing else to read for now. Disable deadline.
			socket.conn.SetReadDeadline(time.Time{})
		} else {
			socket.updateDeadline(readDeadline)
		}
		socket.Unlock()

		// XXX Do bound checking against totalLen.
	}
}
// Estimated minimum cost per socket: 1 goroutine + memory for the largest
// document ever seen.