发送动态数据

Question

我为移动定义了一个结构

typedef struct {
    MsgType msgType;
    int newFallenStonesSize;
    char *newFallenStones;
} MsgMove;

然后像这样发送数据：

MsgMove message;
message.msgType = MsgTypeMove;     
message.newFallenStones = (char *)malloc(nrNewFallenStones*sizeof(char));
for (int i=0; i<nrNewFallenStones; i++) {
    message.newFallenStones[i]=newFallenStones[i];
}
message.newFallenStonesSize = nrNewFallenStones;

NSData *data = [NSData dataWithBytes:&message length:(2*sizeof(int)+message.newFallenStonesSize*sizeof(char))];          

[[KKGameKitHelper sharedGameKitHelper] sendDataToAllPlayers:data reliable:YES]; 

数据在发送时是正确的，但是当我像这样接收数据时：

else if (msg->msgType == MsgTypeMove)
{
    MsgMove *msgMove = (MsgMove *) [data bytes]; 
    for (int i=0; i<msgMove->newFallenStonesSize; i++) {
        NSLog(@"New Stone received:%i",msgMove->newFallenStones[i]);
    }
}

值已更改。例如1，6，3，我得到76,10598。

有人知道为什么会这样吗？

Answer 1

主要问题是，您通过网络发送指向数据的指针，而不是实际的数据。当您为message.newFallenStones分配空间时，它将被设置为内存中某个明显随机的位置，该位置与您的MsgMove结构不相邻。然后将您的数据写入这个另一个内存位置。您打包要传输的是MsgMove结构(带有指向内存中其他位置的指针)，外加内存中紧跟其后的任何随机字节。

处理这种情况的典型方法是将整个消息放在一起，并将数据写入消息的末尾。更像是：

typedef struct {
    MsgType msgType;
    int newFallenStonesSize;
    char newFallenStones;        // The first newFallenStones value
} MsgMove;

，然后与

MsgMove *message;
message = (MsgMove *)malloc(sizeof(MsgMove)+nrNewFallenStones-1);
message->msgType = MsgTypeMove;     
message->newFallenStonesSize = nrNewFallenStones;
char *newStones = &MsgMove->newFallenStones;
for (int i=0; i<nrNewFallenStones; i++) {
    newStones[i]=newFallenStones[i];
}

NSData *data = [NSData dataWithBytes:message length:(sizeof(MsgMove)+nrNewFallenStones-1)];          

[[KKGameKitHelper sharedGameKitHelper] sendDataToAllPlayers:data reliable:YES];