5 .type _strncat,@function
7 ;; On entry: r1 => Destination
9 ;; r3 => Max number of bytes to copy
11 mov r1, r4 ; Save a copy of the dest pointer.
12 mov r2, r5 ; Save a copy of the source pointer.
13 mov r3, r14 ; Save a copy of the byte count.
15 mov #0, r2 ; Search for the NUL byte.
16 mov #-1, r3 ; Search until we run out of memory.
17 suntil.b ; Find the end of the destination string.
18 sub #1, r1 ; suntil.b leaves r1 pointing to the byte beyond the NUL.
20 mov r14, r3 ; Restore the limit on the number of bytes copied.
21 mov r5, r2 ; Restore the source pointer.
22 mov r1, r5 ; Save a copy of the dest pointer.
23 smovu ; Copy source to destination.
25 add #0, r14, r3 ; Restore the number of bytes to copy (again), but this time set the Z flag as well.
26 beq 1f ; If we copied 0 bytes then we already know that the dest string is NUL terminated, so we do not have to do anything.
27 mov #0, r2 ; Otherwise we must check to see if a NUL byte
28 mov r5, r1 ; was included in the bytes that were copied.
30 beq 1f ; Z flag is set if a match was found.
31 add r14, r5 ; Point at byte after end of copied bytes.
32 mov.b #0, [r5] ; Store a NUL there.
34 mov r4, r1 ; Return the original dest pointer.