# strlen_P.S

/* Copyright (c) 2002, 2005, 2006, 2007 Marek Michalkiewicz

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the documentation and/or other materials provided with the
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* Neither the name of the copyright holders nor the names of
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from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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/* $Id$ */

/** \file */
/** \ingroup avr_pgmspace
\fn size_t strlen_P(PGM_P src)

The strlen_P() function is similar to strlen(), except that src is a
pointer to a string in program space.

\returns The strlen() function returns the number of characters in src.

\note strlen_P() is implemented as an inline function in the avr/pgmspace.h
header file, which will check if the length of the string is a constant
and known at compile time. If it is not known at compile time, the macro
will issue a call to __strlen_P() which will then calculate the length
of the string as normal.
*/

#if !defined(__AVR_TINY__)

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define src_hi r25
#define src_lo r24

; 11 words, (14 + __strlen_P(src) * 8) cycles

ASSEMBLY_CLIB_SECTION
.global _U(__strlen_P)
.type   _U(__strlen_P), @function
_U(__strlen_P):
X_movw  ZL, src_lo
.L_strlen_P_loop:
X_lpm   r0, Z+
tst     r0
brne    .L_strlen_P_loop
; return Z - 1 - src = (-1 - src) + Z = ~src + Z
com     src_lo
com     src_hi