1/* Copyright (c) 2002, 2007 Marek Michalkiewicz 2 All rights reserved. 3 4 Redistribution and use in source and binary forms, with or without 5 modification, are permitted provided that the following conditions are met: 6 7 * Redistributions of source code must retain the above copyright 8 notice, this list of conditions and the following disclaimer. 9 * Redistributions in binary form must reproduce the above copyright 10 notice, this list of conditions and the following disclaimer in 11 the documentation and/or other materials provided with the 12 distribution. 13 * Neither the name of the copyright holders nor the names of 14 contributors may be used to endorse or promote products derived 15 from this software without specific prior written permission. 16 17 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 18 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 21 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27 POSSIBILITY OF SUCH DAMAGE. */ 28 29/* $Id: strnlen.S 1944 2009-04-01 23:12:20Z arcanum $ */ 30 31/** \file */ 32/** \ingroup avr_string 33 \fn size_t strnlen(const char *src, size_t len) 34 \brief Determine the length of a fixed-size string. 35 36 The strnlen function returns the number of characters in the string 37 pointed to by src, not including the terminating '\\0' character, but at 38 most len. In doing this, strnlen looks only at the first len characters at 39 src and never beyond src+len. 40 41 \returns The strnlen function returns strlen(src), if that is less than 42 len, or len if there is no '\\0' character among the first len 43 characters pointed to by src. */ 44 45#if !defined(__DOXYGEN__) 46 47#include "macros.inc" 48 49#define src_hi r25 50#define src_lo r24 51#define len_hi r23 52#define len_lo r22 53 54 ASSEMBLY_CLIB_SECTION 55 .global _U(strnlen) 56 .type _U(strnlen), @function 57_U(strnlen): 58 X_movw ZL, src_lo 59.L_strnlen_loop: 60 subi len_lo, lo8(1) 61 sbci len_hi, hi8(1) 62 ld __tmp_reg__, Z+ 63 cpse __tmp_reg__, __zero_reg__ 64 brcc .L_strnlen_loop 65; Z points one character past the terminating NUL 66; return Z - 1 - src = (-1 - src) + Z = ~src + Z 67 com src_lo 68 com src_hi 69 add src_lo, ZL 70 adc src_hi, ZH 71 ret 72.L_strnlen_end: 73 .size _U(strnlen), .L_strnlen_end - _U(strnlen) 74 75#endif /* not __DOXYGEN__ */ 76