# atoi.S

/* Copyright (c) 2002, 2007 Reiner Patommel

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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
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */

/* $Id$ */

/*
Contributors:
Created by Reiner Patommel
Changes: Jochen Pernsteiner, Marek Michalkiewicz
Changes: Reiner Patommel, 8 Feb 2003
Changes: Reiner Patommel, 13 May 2003 (DOXYGEN)

TODO: this implementation uses an inline isspace(). If Avr-libc will
use locales other than C/POSIX it is needed to call an external isspace().

ATTENTION: an external __mulhi_const_10() function is used: nonstandart
call conventions: some registers and bit T must be nochanged.
*/

/** \file */
/** \ingroup avr_stdlib
\fn int atoi(const char *s)
\brief Convert a string to an integer.

The atoi() function converts the initial portion of the string
pointed to by \p s to integer representation. In contrast to

\code (int)strtol(s, (char **)NULL, 10); \endcode

this function does not detect overflow (\c errno is not changed and
the result value is not predictable), uses smaller memory (flash and
stack) and works more quickly.
*/

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define str_hi  r25
#define str_lo  r24
#define num_hi  r25
#define num_lo  r24
#define tmp     r18

ASSEMBLY_CLIB_SECTION
.global _U(atoi)
.type   _U(atoi), @function

/*
Skip leading spaces and tabs.  Process optional sign.  Stop conversion
on detection of a non-numeric character.  Return 0 if string contains
no numeric characters. No check is performed whether the value is within
the range of an 'int' i.e. 32768 becomes -32768.
*/

/* This fact is used below.     */
.if     ('\t'-9) | ('\n'-10) | ('\f'-12) | ('\r'-13)    ; '\v' is 11
.err
.endif

_U(atoi):
X_movw  ZL, str_lo              ; set pointer to string
CLR     num_lo
CLR     num_hi                  ; clear number
CLT                             ; clear sign flag

.L_atoi_loop:
LD      tmp, Z+                 ; get (next) character
CPI     tmp, ' '                ; skip whitespace
BREQ    .L_atoi_loop
CPI     tmp, '\t'               ; ASCII sequence is: \t,\n,\v,\f,\r
BRLO    1f
CPI     tmp, '\r'+1
BRLO    .L_atoi_loop
1:
CPI     tmp, '+'                ; if '+' convert
BREQ    .L_atoi_loop2
CPI     tmp, '-'                ; if '-' remember sign
BRNE    .L_atoi_digit
SET                             ; remember number is negative
RJMP    .L_atoi_loop2

2:      XCALL   __mulhi_const_10        ; r25:r24 *= 10
ADD     num_lo, tmp             ; num = (num * 10) + (tmp - '0')
.L_atoi_loop2:
LD      tmp, Z+
.L_atoi_digit:
SUBI    tmp, '0'
CPI     tmp, 10
BRLO    2b

BRTC    .L_atoi_done            ; positive number? -> return
COM     num_hi
NEG     num_lo
SBCI    num_hi, -1              ; make number negative
.L_atoi_done:
RET

.L_atoi_end:
.size _U(atoi), .L_atoi_end - _U(atoi)

#endif /* not __DOXYGEN__ */