File: strncasecmp.S

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/*
   strncasecmp.S
   Case insensitive compare

   Contributors:
     Created by Reiner Patommel

   THIS SOFTWARE IS NOT COPYRIGHTED

   This source code is offered for use in the public domain.  You may
   use, modify or distribute it freely.

   This code is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY.  ALL WARRANTIES, EXPRESS OR IMPLIED ARE HEREBY
   DISCLAIMED.  This includes but is not limited to warranties of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*/
#include "macros.inc"

#define s1_hi r25
#define s1_lo r24
#define s2_hi r23
#define s2_lo r22
#define len_hi r21
#define len_lo r20
#define tmp r19
#define cht r18

#define ret_hi r25
#define ret_lo r24

; int strncasecmp(const char *s1, const char *s2, size_t len)

    .text
    .global _U(strncasecmp)
    .type   _U(strncasecmp), @function
_U(strncasecmp):
    LOAD_Z(s2_lo, s2_hi)
    LOAD_X(s1_lo, s1_hi)
.strncasecmp_loop:
    SUBI    len_lo, lo8(1)
    SBCI    len_hi, hi8(1)
    BRCS    .strncasecmp_equal
    LD      ret_lo, X+          ; load *s1
    LD      tmp, Z+             ; load *s2
    MOV     cht, tmp            ; copy of *s2 to cht
    ORI     cht, 0x20           ; make it lower case
    CPI     cht, 'a'            ; test on [a .. z]
    BRLT    .strncasecmp_tst
    CPI     cht, 'z'+1
    BRGE    .strncasecmp_tst
    ORI     tmp, 0x20           ; we got an alpha in s2
    ORI     ret_lo, 0x20        ; make *s1, *s2 lower case
.strncasecmp_tst:
    SUB     ret_lo, tmp         ; compare chars
    BRNE    .strncasecmp_done
    TST     tmp                 ; end of s2?
    BRNE    .strncasecmp_loop
.strncasecmp_equal:
    SUB     ret_lo, ret_lo      ; clear ret_lo and C flag
.strncasecmp_done:
; ret_hi = SREG.C ? 0xFF : 0
    SBC     ret_hi, ret_hi
    RET
.strncasecmp_end:
    .size   _U(strncasecmp), .strncasecmp_end - _U(strncasecmp)