Search code examples
ccastingstructurepragma

Convert C structure into unsigned char

I have a function UartSend() to send data to network through uart. it takes argument unsigned char and an integer

UartSend(unsigned char *psend_data,int length);

i want to send a structure through this function

#pragma pack(push, 1)
struct packet
{

    int a;
    char b[3];
    ...

}PacketData;

#pragma pack(pop)

How to covert this structure to unsigned char for sending this data through UartSend? thanks..

Solution

  • You can simply cast to unsigned char *, provided you get your size correct:

    PacketData pkt;
UartSend((unsigned char *)&pkt, sizeof(pkt));

    unsigned char * in this context really just means byte.

    Of course, at the other end of the connection, you'll need to incorporate program logic to re-cast to PacketData (or some similar struct).

    EDIT: However, note that as @WhozCraig points out in comments, if your destination platform is not identical to your source platform, you need to consider alignment issues (or, alternatively, rely on a GNU extension like __packed__)