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How to concatenate two dynamic memory segments (All Platforms)

There is a limitation within Synergy DBL regarding the maximum size of an argument. This limit is 64K
This is not normally a problem however when working with dynamic memory, sometimes you need to merge or concatenate large memory segments

So here is an example of a routine to add / concatenate to two dynamic memory segments. The first dynamic memory handle is resized and to hold the result and must be created as with the option DM_STATIC
The code can be download from here

.subroutine concat_dynmem, stack
    a_hdl1    ,n    ;mem handle 1
    a_hdl2    ,n    ;mem handle 2

;max size of data to move
.define MAX64K    ,65535

.align
record
    datasize    ,i4
    datapos    ,i4
    frompos    ,i4

structure dyndata
    dynchar    ,a1

.proc
    ;get this size of the two data areas
    datapos = %mem_proc(DM_GETSIZE, a_hdl1)
    datasize = %mem_proc(DM_GETSIZE, a_hdl2)

    ;resize first memory segment to hold result
    a_hdl1 = %mem_proc(DM_RESIZ, datapos + datasize, a_hdl1)

    frompos = 1
    repeat
        begin
        if (datasize .le. MAX64K)    ;less than 64k left
        exitloop

        ;move memory in 64K chunks
        ^m(dyndata[1].dynchar(datapos+1:max64k), a_hdl1) =
        &    ^m(dyndata[1].dynchar(frompos:max64k), a_hdl2)
        datasize = datasize - MAX64K
        datapos = datapos + MAX64K
        frompos = frompos + MAX64K
        end

    ;move the remaining memory
    if (datasize)
        ^m(dyndata[1].dynchar(datapos+1:datasize), a_hdl1) =
        &    ^m(dyndata[1].dynchar(frompos:datasize), a_hdl2)
    xreturn
.end

Referencing a chunk of dynamic memory larger than 64K results in one of to runtime errors depending on what you are doing.
Either a 'MAP outside bounds of field or handle' or 'Invalid Subscript specified'.

If you have any comments on this code. Please let me know.

Note: Synergy DBL Version 7 or higher required.