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1. 

   pyrohaz
   Member

   Hey,
   As you can probably tell from my questions, i'm porting from arduino to maple. So far so good!

   The only question, on my arduino, I can use the command memcpy to copy a 64 piece array from one section to another, for example:
   memcpy(array1, array2, 128);

   The small snippet of code above will copy array2 to array1.

   When I tried to write this code to my maple, it said that memcpy was not declared in this scope, the arduino IDE allows me to use this piece of code.

   What am I doing wrong?

   Thanks,
   Harris

   Posted 3 years ago #
2. 

   bubulindo
   Member

   did you include string.h?

   This compiles for me:

   #include <string.h> <------ THIS??

   void setup(){}

   void loop(){

   char array1[130];
   char array2[130];

   memcpy(array1, array2, 128);
   }

   Posted 3 years ago #
3. 

   pyrohaz
   Member

   Heh! Brilliant, thats sorted it, I never needed to do that on arduino haha thanks a lot dude! :)

   Posted 3 years ago #
4. 

   gbulmer
   Moderator

   pyrohaz - I'd like to suggest a slightly more robust approach to copying memory.

   Instead of memcpy(array1, array2, 128);
   do memcpy(array1, array2, sizeof(array1));

   sizeof is applied to the destination of the memcpy.

   Arduino (AVR, ATmega) and Maple (ARM, STM32) have different sizes for data types, for example int, so using a fixed value might not work when porting code. The compiler calculates sizeof() at compile time, and ensures the value is the actual size of the variable, which is more robust when porting code. sizeof() can be used in calculations, e.g. sizeof(array1)-1

   NB, for folks who aren't familiar with sizeof; sizeof calculates the size of the value stored in the variable, sizeof does not calculate the size of object a variable may point at:
   

   char array1[130];
   char *p = array1;
   char array2[130];
   memcpy(p, array2, sizeof(p));

   will only copy the size of a char pointer (4 bytes on STM32), and not the size of the array p is pointing to.
   memcpy(p, array2, sizeof(*p));
   copies 1 byte.

   Posted 3 years ago #
5. 

   pyrohaz
   Member

   Thats really useful actually, all of my arrays are 64 pieces of data but by using size of, that eases things by a lot! Thanks for that :)

   Posted 3 years ago #

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