1/* 2Copyright (c) 2009 Nick Clifton <nickc@redhat.com> 3 */ 4 .file "strncat.S" 5 6 .section .text 7 .global _strncat 8 .type _strncat,@function 9_strncat: 10 ;; On entry: r1 => Destination 11 ;; r2 => Source 12 ;; r3 => Max number of bytes to copy 13#ifdef __RX_DISALLOW_STRING_INSNS__ 14 cmp #0, r3 ; If max is zero we have nothing to do. 15 beq 2f 16 17 mov r1, r4 ; Leave the desintation pointer intact for the return value. 18 191: mov.b [r4+], r5 ; Find the NUL byte at the end of the destination. 20 cmp #0, r5 21 bne 1b 22 23 sub #1, r4 24 253: mov.b [r2+], r5 ; Copy bytes from the source into the destination ... 26 mov.b r5, [r4+] 27 cmp #0, r5 ; ... until we reach a NUL byte ... 28 beq 2f 29 sub #1, r3 30 bne 3b ; ... or we have copied N bytes. 31 322: rts 33#else 34 mov r1, r4 ; Save a copy of the dest pointer. 35 mov r2, r5 ; Save a copy of the source pointer. 36 mov r3, r14 ; Save a copy of the byte count. 37 38 mov #0, r2 ; Search for the NUL byte. 39 mov #-1, r3 ; Search until we run out of memory. 40 suntil.b ; Find the end of the destination string. 41 sub #1, r1 ; suntil.b leaves r1 pointing to the byte beyond the NUL. 42 43 mov r14, r3 ; Restore the limit on the number of bytes copied. 44 mov r5, r2 ; Restore the source pointer. 45 mov r1, r5 ; Save a copy of the dest pointer. 46 smovu ; Copy source to destination. 47 48 add #0, r14, r3 ; Restore the number of bytes to copy (again), but this time set the Z flag as well. 49 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. 50 mov #0, r2 ; Otherwise we must check to see if a NUL byte 51 mov r5, r1 ; was included in the bytes that were copied. 52 suntil.b 53 beq 1f ; Z flag is set if a match was found. 54 add r14, r5 ; Point at byte after end of copied bytes. 55 mov.b #0, [r5] ; Store a NUL there. 561: 57 mov r4, r1 ; Return the original dest pointer. 58 rts 59#endif 60 .size _strncat, . - _strncat 61 62