将结构存储在数组中

Question

Im am trying to make some code, which mimics a simple malloc-function (in C), though it should only control the memory of a big array, and not the actual physical memory. To control the "memory", I would like to store segments of META-data in the memory-array. The META-data is stored as a struct. My question is, how do I correctly store the struct in the bytes of the array? In the example shown here, I try to store some initial META-data on the starting element of the memory-array; however I have syntax wrong to do this.

typedef struct _xMetaData{
    size_t      xSize;
    int*        piNextBlock;
    int     iBlockFree;
}xMetaData;

int8_t memory[ALLOCATE_SIZE];


// Pointer to struct
xMetaData* pxMetaPtr;

xMetaData xInitialData = {BLOCKSIZE, &memory[INITIAL_BLOCK_ADDRESS], BLOCK_FREE};
&memory[0] = xInitialData;

Answer 1

You need to cast the block of memory to xMetaData :

*(xMetaData *) (&memory[0]) = xInitialData;

You should also be aware of structure padding if you're using a struct for this kind of thing (for example, make sure ALLOCATE_SIZE uses sizeof(xMetaData) and not a hardcoded length, and make sure you always access the memory using the struct.)