将结构/工会成员链接到另一个结构/工会成员

Question

I am somewhat new to C in regards to structures, unions and bitfields and need help. Below is the SLPH_CONTROL which will "control" the bits in the destination of DRVCONF0 and DRVCONF1. After the code snippet I will explain what I need.

/* SLPH_CONTROL **********************************************/

typedef union
{
    struct
    {
        unsigned int SH0_BIT0 :1;
        unsigned int SH0_BIT1 :1;
    };
    uint8 SLPH_CONTROL_byte;
} SLPH_CONTROL;

SLPH_CONTROL my_SLPH_CONTROL;

/* DRVCONF0 **********************************************/

typedef union
{
    struct
    {
        unsigned int DF0_BIT0 :1;
        unsigned int DF0_BIT1 :1;
        unsigned int DF0_BIT2 :1;
        unsigned int DF0_BIT3 :1;
        unsigned int DF0_BIT4 :1;
    };
    uint8 DRVCONF0_byte;
} DRVCONF0;

DRVCONF0 my_DRVCONF0;

/* DRVCONF0 **********************************************/

typedef union
{
    struct
    {
        unsigned int DF1_BIT0 :1;
        unsigned int DF1_BIT1 :1;
        unsigned int DF1_BIT2 :1;
        unsigned int DF1_BIT3 :1;
        unsigned int DF1_BIT4 :1;
    };
    uint8 DRVCONF1_byte;
} DRVCONF1;

DRVCONF1 my_DRVCONF1;

Now with the code above I want to link or copy data from and to like so:

SH0_BIT0:1 to DF0_BIT4:1;
SH1_BIT1:1 to DF1_BIT0:1;

Is there a way to do this? I am really lost and looked everywhere online for a solution to this. Any suggestions are welcome!!!

Thanks,

Eric

Answer 1

Maybe this is possible on special embedded H/W (I don't know) but not on a regular PC with standard C.

Bit fields describe individual bits in one or more consecutive bytes. Actually, bytes are addressable but bits are not. The read/write access to bits is internally solved by bit-wise operations (like in C expressed with & , | , ^ , ~ ).

my_DRVCONF0 and my_DRVCONF1 are individual variables in your sample. Thus, it's even not granted that they will be allocated/stored in consecutive memory. (They definitely will not if some kind of word-alignment is enabled.)

You probably have to make the control more sophisticated (eg providing pairs of address and bit index) to do what's intended.