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