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/*
* libzvbi - BCD arithmetic for Teletext page numbers
*
* Copyright (C) 2001-2003 Michael H. Schimek
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* $Id: bcd.c,v 1.4 2006/02/03 18:22:53 mschimek Exp $ */
#include "bcd.h"
#include "misc.h" /* unlikely() */
/**
* @addtogroup BCD BCD arithmetic for Teletext page numbers
* @ingroup Service
*
* Teletext page numbers are expressed as packed binary coded decimal
* numbers in range 0x100 to 0x8FF. The packed 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.
*
* BCD numbers are stored in int types. Negative BCDs are expressed
* as ten's complement, for example -1 as 0xF999 9999, assumed
* sizeof(int) is four. Their precision as signed packed bcd value
* is VBI3_BCD_MIN .. VBI3_BCD_MAX, as two's complement
* binary VBI3_BCD_BIN_MIN ... VBI3_BCD_BIN_MAX. That is -10 ** n ...
* (10 ** n) - 1, where n = 2 * sizeof(int) - 1.
*/
/**
* @ingroup BCD
* @param bin Binary number.
*
* Converts a two's complement binary to a signed packed bcd value.
* The argument @a bin must be in range VBI3_BCD_BIN_MIN ...
* VBI3_BCD_BIN_MAX. Other values yield an undefined result.
*
* @return
* BCD number.
*/
int
vbi3_bin2bcd (int bin)
{
int t = 0;
/* XXX might try x87 bcd for large values. */
/* Teletext page numbers are unsigned. */
if (unlikely (bin < 0)) {
t |= VBI3_BCD_MIN;
bin += -VBI3_BCD_BIN_MIN;
}
/* Most common case 2-4 digits, as in Teletext
page and subpage numbers. */
t += (bin % 10) << 0; bin /= 10;
t += (bin % 10) << 4; bin /= 10;
t += (bin % 10) << 8; bin /= 10;
t += (bin % 10) << 12;
if (unlikely (bin >= 10)) {
unsigned int i;
for (i = 16; i < sizeof (int) * 8; i += 4) {
bin /= 10;
t += (bin % 10) << i;
}
}
return t;
}
/**
* @ingroup BCD
* @param bcd BCD number.
*
* Converts a signed packed bcd to a two's complement binary value.
*
* @return
* Binary number. The result is undefined when the bcd number
* contains hex digits 0xA ... 0xF, except for the sign nibble.
*/
int
vbi3_bcd2bin (int bcd)
{
int s;
int t;
s = bcd;
/* Teletext page numbers are unsigned. */
if (unlikely (bcd < 0)) {
/* Cannot negate minimum. */
if (unlikely (VBI3_BCD_MIN == bcd))
return VBI3_BCD_BIN_MIN;
bcd = vbi3_neg_bcd (bcd);
}
/* Most common case 2-4 digits, as in Teletext
page and subpage numbers. */
t = (bcd & 15) * 1; bcd >>= 4;
t += (bcd & 15) * 10; bcd >>= 4;
t += (bcd & 15) * 100; bcd >>= 4;
t += (bcd & 15) * 1000;
if (unlikely (bcd & -16)) {
unsigned int u;
unsigned int i;
u = (bcd >> (sizeof (int) * 8 - 5 * 4)) & 15;
for (i = sizeof (int) * 8 - 6 * 4; i >= 4; i -= 4)
u = u * 10 + ((bcd >> i) & 15);
t += u * 10000;
}
/* Teletext page numbers are unsigned. */
if (unlikely (s < 0))
t = -t;
return t;
}
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