SAP Stringbuilder for ABAP?

I am looking for a faster way to add to an existing line in ABAP.

ABAP version NW 7.x

Nowadays, string concatenation takes a very long time, especially after the string gets big. We need to build lines> 10 mb in size.

The line is built logically with many operations x = x + y

.

concatenate l_main_string l_extra into l_main_string. " very slow

      

        
        
        
      

    

Is there a faster way to build large strings in ABAP? Perhaps a kernel tool can be called?

EDIT: Based on feedback and response.
Most helpful is the VWegert related blog. In fact, this is the answer to the question. It also seems that the old kernels that clients use are the key issue.

& & and Concatenate, which are very similar to our system. (NW 7.50) 1.46s versus 1.50s re. Obviously the same optimization has been run and it works in an acceptable way.

  METHOD PERF_TEST_STRING.  " 1.50 sec
     DATA: n TYPE i value 5000000,
          lv_string TYPE string.
         do n times.
            CONCATENATE lv_string 'ABCDEFGHIJ0123456789' into lv_string.
        ENDDO.
        r_len = strlen( lv_string ).
    ENDMETHOD.
    METHOD PERF_TEST_STRING2. "1.46  
        DATA: n TYPE i value 5000000,
              lv_string TYPE string.
        do n times.
          lv_string = lv_string && 'ABCDEFGHIJ0123456789'.
        ENDDO.
        r_len = strlen( lv_string ).
     ENDMETHOD.

      

        
        
        
      

    

So, I want to check the client kernel layer and look for another reason why things are going slowly.
BTW: i cant use

x = x && Y.    " doesnt work prior to < 7.20

      

        
        
        
      

    

as many clients don't have> = 7.20 :(