Does a "circular memcpy" exist?-CodePudding

Is there a method of using memcpy (or similar) to copy from one circular array into another, but with an offset? I can do it with loops, but I want to do it more fasterer and betterer. Obviously 'circular' isn't a thing with memory, but I hope you get what I mean.

Cheers all.

This is what I want to achieve but without having to use a For;;loop

uint8_t array1[SIZE];
uint8_t array2[SIZE];

uint8_t offset = SOME_OFFSET;
uint8_t offsetAdj;

for (uint8_t index = 0; index < SIZE; index  )
{
    offsetAdj = offset   index;
   if (offsetAdj >= SIZE)
      offsetAdj -= SIZE;
   array2[offsetAdj] = array1[index];
}

CodePudding user response：

That's a std::rotate_copy that you have implemented with your code.

uint8_t array1[SIZE];
uint8_t array2[SIZE];
uint8_t offset = SOME_OFFSET;

std::rotate_copy( std::begin(array1),
                  std::begin(array1)   offset,
                  std::end  (array1),
                  std::begin(array2) );

Unlike memcpy, std::rotate_copy will also work on non-contiguous containers and containers of types that are not trivially copyable.

CodePudding user response：

Here is a simple working example

#include <stdio.h>
#include <string.h>
#include <stdint.h>


int main() {
    
    uint8_t SIZE = 8;
    uint8_t array1[SIZE];
    uint8_t array2[SIZE];
    uint8_t offset = 3;
    uint8_t i = 0; 
  
  // Initialize the arrays with some values
  for (i = 0; i < SIZE; i  ) {
    array1[i] = i;
    array2[i] = 0;
  }

  // Copy the elements of array1 into array2 with an offset of 3
  memcpy(&array2[offset], array1, SIZE - offset);
  memcpy(array2, &array1[SIZE - offset], offset);

  // Print the contents of array1 and array2 to verify the copy
    
  for (i = 0; i < SIZE; i  )
    printf("%d ", array1[i]);
  
  printf("\n");
  
  for (i = 0; i < SIZE; i  )
    printf("%d ", array2[i]);
  
  return 0;
}