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Add proper float formatting to vuprintf

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Wanted to see how gnarly it is to do.

Big number handling could be done with better algorithms
since it can get a bit slow with large integers or tiny
fractions with many lead zeros when only a few digits are
needed.

Anyway, it supports %e, %E, %f, %F, %g and %G. No %a or long
double support seems warranted at the moment.

Assumes IEEE 754 double format but it's laid out to be able to
replace a function to handle others if needed.

Tested in a driver program that has a duplicate vuprintf and
the content was pasted in once it looked sound enough to put
up a patch.

Change-Id: I6dae8624d3208e644c88e36e6a17d8fc9144f988
This commit is contained in:
Michael Sevakis 2018-01-06 07:17:04 -05:00 • committed by Franklin Wei
parent 3e2b50ed3b
commit b70fecf21d
4 changed files with 793 additions and 10 deletions
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59
firmware/include/ap_int.h Normal file
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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2018 by Michael A. Sevakis
*
* 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 software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#ifndef AP_INT_H
#define AP_INT_H
/* Miscellaneous large-sized integer functions */
#include <stdbool.h>
#include <stdint.h>
/* return floor(log(2)*base2exp) - assists in estimating buffer sizes
* when converting to decimal */
static inline int base10exp(int base2exp)
{
/* 1292913986 = floor(2^32*log(2)) */
static const long log10of2 = 1292913986L;
return log10of2 * (int64_t)base2exp >> 32;
}
struct ap_int
{
long numchunks; /* number of uint32_t chunks or zero */
long basechunk; /* chunk of start of value bits */
uint32_t *chunks; /* pointer to chunk array (caller alloced) */
long len; /* length of output */
long shift; /* number of fractional bits */
uint64_t val; /* value, if it fits and numchunks is zero */
};
bool round_number_string10(char *p_rdig, long len);
/* format arbitrary-precision base 10 integer */
char * format_ap_int10(struct ap_int *a,
char *p_end);
/* format arbitrary-precision base 10 fraction */
char * format_ap_frac10(struct ap_int *a,
char *p_start,
long precision);
#endif /* AP_INT_H */