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224 lines
5.8 KiB
C
224 lines
5.8 KiB
C
/*
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* libzvbi -- BCD arithmetic for Teletext page numbers
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*
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* Copyright (C) 2001, 2002 Michael H. Schimek
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301 USA.
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*/
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/* $Id: bcd.h,v 1.19 2008-02-21 07:18:52 mschimek Exp $ */
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#ifndef BCD_H
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#define BCD_H
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#include "misc.h"
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/**
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* @addtogroup BCD BCD arithmetic for Teletext page numbers
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* @ingroup HiDec
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*
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* Teletext page numbers are expressed as packed binary coded decimal
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* numbers in range 0x100 to 0x8FF. The bcd format encodes one decimal
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* digit in every hex nibble (four bits) of the number. Page numbers
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* containing digits 0xA to 0xF are reserved for various system purposes
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* and not intended for display.
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*/
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/* Public */
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/**
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* @ingroup HiDec
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*
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* Teletext or Closed Caption page number. For Teletext pages
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* this is a packed bcd number in range 0x100 ... 0x8FF. Page
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* numbers containing digits 0xA to 0xF are reserved for various
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* system purposes, these pages are not intended for display.
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*
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* Closed Caption page numbers between 1 ... 8 correspond
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* to the four Caption and Text channels:
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* <table>
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* <tr><td>1</td><td>Caption 1</td><td>
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* "Primary synchronous caption service [English]"</td></tr>
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* <tr><td>2</td><td>Caption 2</td><td>
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* "Special non-synchronous data that is intended to
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* augment information carried in the program"</td></tr>
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* <tr><td>3</td><td>Caption 3</td><td>
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* "Secondary synchronous caption service, usually
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* second language [Spanish, French]"</td></tr>
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* <tr><td>4</td><td>Caption 4</td><td>
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* "Special non-synchronous data similar to Caption 2"</td></tr>
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* <tr><td>5</td><td>Text 1</td><td>
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* "First text service, data usually not program related"</td></tr>
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* <tr><td>6</td><td>Text 2</td><td>
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* "Second text service, additional data usually not program related
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* [ITV data]"</td></tr>
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* <tr><td>7</td><td>Text 3</td><td>
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* "Additional text channel"</td></tr>
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* <tr><td>8</td><td>Text 4</td><td>
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* "Additional text channel"</td></tr>
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* </table>
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*/
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/* XXX unsigned? */
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typedef int vbi_pgno;
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/**
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* @ingroup HiDec
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*
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* This is the subpage number only applicable to Teletext pages,
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* a packed bcd number in range 0x00 ... 0x99. On special 'clock' pages
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* (for example listing the current time in different time zones)
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* it can assume values between 0x0000 ... 0x2359 expressing
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* local time. These are not actually subpages.
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*/
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typedef int vbi_subno;
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/**
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* @ingroup HiDec
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*/
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#define VBI_ANY_SUBNO 0x3F7F
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/**
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* @ingroup HiDec
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*/
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#define VBI_NO_SUBNO 0x3F7F
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/**
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* @ingroup BCD
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* @param dec Decimal number.
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*
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* Converts a two's complement binary between 0 ... 999 to a
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* packed bcd number in range 0x000 ... 0x999. Extra digits in
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* the input will be discarded.
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*
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* @return
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* BCD number.
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*/
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_vbi_inline unsigned int
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vbi_dec2bcd(unsigned int dec)
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{
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return (dec % 10) + ((dec / 10) % 10) * 16 + ((dec / 100) % 10) * 256;
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}
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/**
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* @ingroup BCD
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* @since 0.2.28
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*/
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#define vbi_bin2bcd(n) vbi_dec2bcd(n)
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/**
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* @ingroup BCD
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* @param bcd BCD number.
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*
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* Converts a packed bcd number between 0x000 ... 0xFFF to a two's
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* complement binary in range 0 ... 999. Extra digits in the input
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* will be discarded.
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*
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* @return
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* Decimal number. The result is undefined when the bcd number contains
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* hex digits 0xA ... 0xF.
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**/
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_vbi_inline unsigned int
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vbi_bcd2dec(unsigned int bcd)
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{
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return (bcd & 15) + ((bcd >> 4) & 15) * 10 + ((bcd >> 8) & 15) * 100;
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}
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/**
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* @ingroup BCD
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* @since 0.2.28
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*/
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#define vbi_bcd2bin(n) vbi_bcd2dec(n)
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/**
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* @ingroup BCD
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* @param a BCD number.
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* @param b BCD number.
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*
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* Adds two packed bcd numbers, returning a packed bcd sum. Arguments
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* and result are in range 0xF000 0000 ... 0x0999 9999, that
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* is -10**7 ... +10**7 - 1 in decimal notation. To subtract you can
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* add the 10's complement, e. g. -1 = 0xF999 9999.
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*
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* @return
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* Packed bcd number. The result is undefined when any of the arguments
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* contain hex digits 0xA ... 0xF.
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*/
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_vbi_inline unsigned int
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vbi_add_bcd(unsigned int a, unsigned int b)
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{
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unsigned int t;
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a += 0x06666666;
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t = a + b;
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b ^= a ^ t;
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b = (~b & 0x11111110) >> 3;
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b |= b * 2;
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return t - b;
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}
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/**
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* @ingroup BCD
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* @param bcd BCD number.
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*
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* Tests if @a bcd forms a valid BCD number. The argument must be
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* in range 0x0000 0000 ... 0x0999 9999.
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*
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* @return
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* @c FALSE if @a bcd contains hex digits 0xA ... 0xF.
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*/
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_vbi_inline vbi_bool
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vbi_is_bcd(unsigned int bcd)
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{
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static const unsigned int x = 0x06666666;
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return (((bcd + x) ^ (bcd ^ x)) & 0x11111110) == 0;
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}
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/**
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* @ingroup BCD
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* @param bcd Unsigned BCD number.
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* @param maximum Unsigned maximum value.
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*
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* Compares an unsigned packed bcd number digit-wise against a maximum
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* value, for example 0x295959. @a maximum can contain digits 0x0
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* ... 0xF.
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*
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* @return
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* @c TRUE if any digit of @a bcd is greater than the
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* corresponding digit of @a maximum.
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*
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* @since 0.2.28
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*/
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_vbi_inline vbi_bool
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vbi_bcd_digits_greater (unsigned int bcd,
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unsigned int maximum)
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{
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maximum ^= ~0;
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return 0 != (((bcd + maximum) ^ bcd ^ maximum) & 0x11111110);
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}
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/* Private */
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#endif /* BCD_H */
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/*
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Local variables:
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c-set-style: K&R
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c-basic-offset: 8
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End:
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*/
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