Hi,

"So what about sending the data to memory, as they're doing, then bring it to a VFP array using your library, make the modifications in the array with VFP, and then sending the array back in just one time ?
That would avoid all those SYS(2600) calls...
Is that correct ?"

In theory yes, practically no.
cause the FoxPro LCK array functions can only address up to 65000 elements in a array, this would limit the string size to 65000 bytes.

Additionally one would have to store the individual characters as a number not as a string into the array, since otherwise there would be 1 memory allocation per character which would slow down the process considerably.

To repeat myself: VFP IS THE WRONG TOOL FOR THE JOB!!

Christian