Mercurial > dropbear
view libtommath/bn_mp_div_3.c @ 1499:2d450c1056e3
options: Complete the transition to numeric toggles (`#if')
For the sake of review, this commit alters only the code; the affiliated
comments within the source files also need to be updated, but doing so
now would obscure the operational changes that have been made here.
* All on/off options have been switched to the numeric `#if' variant;
that is the only way to make this `default_options.h.in' thing work
in a reasonable manner.
* There is now some very minor compile-time checking of the user's
choice of options.
* NO_FAST_EXPTMOD doesn't seem to be used, so it has been removed.
* ENABLE_USER_ALGO_LIST was supposed to be renamed DROPBEAR_USER_ALGO_LIST,
and this commit completes that work.
* DROPBEAR_FUZZ seems to be a relatively new, as-yet undocumented option,
which was added by the following commit:
commit 6e0b539e9ca0b5628c6c5a3d118ad6a2e79e8039
Author: Matt Johnston <[email protected]>
Date: Tue May 23 22:29:21 2017 +0800
split out checkpubkey_line() separately
It has now been added to `sysoptions.h' and defined as `0' by default.
* The configuration option `DROPBEAR_PASSWORD_ENV' is no longer listed in
`default_options.h.in'; it is no longer meant to be set by the user, and
is instead left to be defined in `sysoptions.h' (where it was already being
defined) as merely the name of the environment variable in question:
DROPBEAR_PASSWORD
To enable or disable use of that environment variable, the user must now
toggle `DROPBEAR_USE_DROPBEAR_PASSWORD'.
* The sFTP support is now toggled by setting `DROPBEAR_SFTPSERVER', and the
path of the sFTP server program is set independently through the usual
SFTPSERVER_PATH.
author | Michael Witten <mfwitten@gmail.com> |
---|---|
date | Thu, 20 Jul 2017 19:38:26 +0000 |
parents | 8bba51a55704 |
children | f52919ffd3b1 |
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#include <tommath_private.h> #ifdef BN_MP_DIV_3_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * * LibTomMath is a library that provides multiple-precision * integer arithmetic as well as number theoretic functionality. * * The library was designed directly after the MPI library by * Michael Fromberger but has been written from scratch with * additional optimizations in place. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, [email protected], http://libtom.org */ /* divide by three (based on routine from MPI and the GMP manual) */ int mp_div_3 (mp_int * a, mp_int *c, mp_digit * d) { mp_int q; mp_word w, t; mp_digit b; int res, ix; /* b = 2**DIGIT_BIT / 3 */ b = (((mp_word)1) << ((mp_word)DIGIT_BIT)) / ((mp_word)3); if ((res = mp_init_size(&q, a->used)) != MP_OKAY) { return res; } q.used = a->used; q.sign = a->sign; w = 0; for (ix = a->used - 1; ix >= 0; ix--) { w = (w << ((mp_word)DIGIT_BIT)) | ((mp_word)a->dp[ix]); if (w >= 3) { /* multiply w by [1/3] */ t = (w * ((mp_word)b)) >> ((mp_word)DIGIT_BIT); /* now subtract 3 * [w/3] from w, to get the remainder */ w -= t+t+t; /* fixup the remainder as required since * the optimization is not exact. */ while (w >= 3) { t += 1; w -= 3; } } else { t = 0; } q.dp[ix] = (mp_digit)t; } /* [optional] store the remainder */ if (d != NULL) { *d = (mp_digit)w; } /* [optional] store the quotient */ if (c != NULL) { mp_clamp(&q); mp_exch(&q, c); } mp_clear(&q); return res; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */