Copy array into array index C

Question

I want to copy an array into a second array at the position index.

What I did is:

uint8_t* _data = (uint8_t *)malloc(8U*1024);
uint32_t index= 4U;
uint8_t name[] ="TEST";
memcpy(&data[index], name, sizeof(uint32_t));
index+= 4U;

When I print data using:

    for (int j =0; j<index; j++)
    {
        printf("%c \n",data[j]);
    }

it is empty. I want to find at data[3] "TEST"

Answer 1

You need to read from the same place you were writing to.

You want this:

  uint8_t* data = malloc(8U * 1024);    // remove the (uint8_t*) cast, it's useless
                                        // but it doesn't do any harm
  uint32_t index = 4U;
  uint8_t name[] = "TEST";
  memcpy(&data[index], name, sizeof(name));     // use sizeof(name)

  //  index += 4U;                                << delete this line

  for (int j = index; j < index + sizeof(name); j++)  // start at j = index 
  {                                                   // and use sizeof(name)
    printf("%c \n", data[j]);
  }