mirror of
https://git.savannah.gnu.org/git/guile.git
synced 2025-04-30 11:50:28 +02:00
53befeb700
(Not quite finished, the following will be done tomorrow. module/srfi/*.scm module/rnrs/*.scm module/scripts/*.scm testsuite/*.scm guile-readline/* )
423 lines
12 KiB
C
423 lines
12 KiB
C
/* srfi-60.c --- Integers as Bits
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*
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* Copyright (C) 2005, 2006, 2008 Free Software Foundation, Inc.
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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 Lesser General Public License
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* as published by the Free Software Foundation; either version 3 of
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* 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, but
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* 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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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301 USA
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*/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <libguile.h>
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#include <srfi/srfi-60.h>
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SCM_DEFINE (scm_srfi60_log2_binary_factors, "log2-binary-factors", 1, 0, 0,
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(SCM n),
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"Return a count of how many factors of 2 are present in @var{n}.\n"
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"This is also the bit index of the lowest 1 bit in @var{n}. If\n"
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"@var{n} is 0, the return is @math{-1}.\n"
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"\n"
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"@example\n"
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"(log2-binary-factors 6) @result{} 1\n"
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"(log2-binary-factors -8) @result{} 3\n"
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"@end example")
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#define FUNC_NAME s_scm_srfi60_log2_binary_factors
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{
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SCM ret = SCM_EOL;
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if (SCM_I_INUMP (n))
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{
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long nn = SCM_I_INUM (n);
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if (nn == 0)
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return SCM_I_MAKINUM (-1);
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nn = nn ^ (nn-1); /* 1 bits for each low 0 and lowest 1 */
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return scm_logcount (SCM_I_MAKINUM (nn >> 1));
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}
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else if (SCM_BIGP (n))
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{
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/* no need for scm_remember_upto_here_1 here, mpz_scan1 doesn't do
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anything that could result in a gc */
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return SCM_I_MAKINUM (mpz_scan1 (SCM_I_BIG_MPZ (n), 0L));
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}
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else
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SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
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return ret;
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_srfi60_copy_bit, "copy-bit", 3, 0, 0,
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(SCM index, SCM n, SCM bit),
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"Return @var{n} with the bit at @var{index} set according to\n"
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"@var{newbit}. @var{newbit} should be @code{#t} to set the bit\n"
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"to 1, or @code{#f} to set it to 0. Bits other than at\n"
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"@var{index} are unchanged in the return.\n"
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"\n"
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"@example\n"
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"(copy-bit 1 #b0101 #t) @result{} 7\n"
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"@end example")
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#define FUNC_NAME s_scm_srfi60_copy_bit
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{
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SCM r;
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unsigned long ii;
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int bb;
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ii = scm_to_ulong (index);
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bb = scm_to_bool (bit);
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if (SCM_I_INUMP (n))
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{
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long nn = SCM_I_INUM (n);
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/* can't set high bit ii==SCM_LONG_BIT-1, that would change the sign,
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which is not what's wanted */
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if (ii < SCM_LONG_BIT-1)
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{
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nn &= ~(1L << ii); /* zap bit at index */
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nn |= ((long) bb << ii); /* insert desired bit */
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return scm_from_long (nn);
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}
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else
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{
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/* bits at ii==SCM_LONG_BIT-1 and above are all copies of the sign
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bit, if this is already the desired "bit" value then no need to
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make a new bignum value */
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if (bb == (nn < 0))
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return n;
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r = scm_i_long2big (nn);
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goto big;
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}
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}
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else if (SCM_BIGP (n))
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{
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/* if the bit is already what's wanted then no need to make a new
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bignum */
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if (bb == mpz_tstbit (SCM_I_BIG_MPZ (n), ii))
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return n;
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r = scm_i_clonebig (n, 1);
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big:
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if (bb)
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mpz_setbit (SCM_I_BIG_MPZ (r), ii);
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else
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mpz_clrbit (SCM_I_BIG_MPZ (r), ii);
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/* changing a high bit might put the result into range of a fixnum */
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return scm_i_normbig (r);
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}
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else
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SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_srfi60_rotate_bit_field, "rotate-bit-field", 4, 0, 0,
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(SCM n, SCM count, SCM start, SCM end),
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"Return @var{n} with the bit field from @var{start} (inclusive)\n"
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"to @var{end} (exclusive) rotated upwards by @var{count} bits.\n"
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"\n"
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"@var{count} can be positive or negative, and it can be more\n"
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"than the field width (it'll be reduced modulo the width).\n"
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"\n"
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"@example\n"
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"(rotate-bit-field #b0110 2 1 4) @result{} #b1010\n"
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"@end example")
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#define FUNC_NAME s_scm_srfi60_rotate_bit_field
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{
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unsigned long ss = scm_to_ulong (start);
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unsigned long ee = scm_to_ulong (end);
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unsigned long ww, cc;
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SCM_ASSERT_RANGE (3, end, (ee >= ss));
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ww = ee - ss;
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cc = scm_to_ulong (scm_modulo (count, scm_difference (end, start)));
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if (SCM_I_INUMP (n))
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{
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long nn = SCM_I_INUM (n);
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if (ee <= SCM_LONG_BIT-1)
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{
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/* all within a long */
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long below = nn & ((1L << ss) - 1); /* before start */
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long above = nn & (-1L << ee); /* above end */
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long fmask = (-1L << ss) & ((1L << ee) - 1); /* field mask */
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long ff = nn & fmask; /* field */
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return scm_from_long (above
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| ((ff << cc) & fmask)
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| ((ff >> (ww-cc)) & fmask)
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| below);
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}
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else
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{
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/* either no movement, or a field of only 0 or 1 bits, result
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unchanged, avoid creating a bignum */
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if (cc == 0 || ww <= 1)
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return n;
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n = scm_i_long2big (nn);
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goto big;
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}
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}
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else if (SCM_BIGP (n))
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{
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mpz_t tmp;
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SCM r;
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/* either no movement, or in a field of only 0 or 1 bits, result
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unchanged, avoid creating a new bignum */
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if (cc == 0 || ww <= 1)
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return n;
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big:
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r = scm_i_ulong2big (0);
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mpz_init (tmp);
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/* portion above end */
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mpz_fdiv_q_2exp (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (n), ee);
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mpz_mul_2exp (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), ee);
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/* field high part, width-count bits from start go to start+count */
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mpz_fdiv_q_2exp (tmp, SCM_I_BIG_MPZ (n), ss);
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mpz_fdiv_r_2exp (tmp, tmp, ww - cc);
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mpz_mul_2exp (tmp, tmp, ss + cc);
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mpz_ior (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), tmp);
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/* field high part, count bits from end-count go to start */
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mpz_fdiv_q_2exp (tmp, SCM_I_BIG_MPZ (n), ee - cc);
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mpz_fdiv_r_2exp (tmp, tmp, cc);
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mpz_mul_2exp (tmp, tmp, ss);
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mpz_ior (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), tmp);
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/* portion below start */
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mpz_fdiv_r_2exp (tmp, SCM_I_BIG_MPZ (n), ss);
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mpz_ior (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), tmp);
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mpz_clear (tmp);
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/* bits moved around might leave us in range of an inum */
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return scm_i_normbig (r);
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}
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else
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SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_srfi60_reverse_bit_field, "reverse-bit-field", 3, 0, 0,
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(SCM n, SCM start, SCM end),
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"Return @var{n} with the bits between @var{start} (inclusive) to\n"
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"@var{end} (exclusive) reversed.\n"
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"\n"
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"@example\n"
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"(reverse-bit-field #b101001 2 4) @result{} #b100101\n"
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"@end example")
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#define FUNC_NAME s_scm_srfi60_reverse_bit_field
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{
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long ss = scm_to_long (start);
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long ee = scm_to_long (end);
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long swaps = (ee - ss) / 2; /* number of swaps */
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SCM b;
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if (SCM_I_INUMP (n))
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{
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long nn = SCM_I_INUM (n);
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if (ee <= SCM_LONG_BIT-1)
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{
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/* all within a long */
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long smask = 1L << ss;
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long emask = 1L << (ee-1);
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for ( ; swaps > 0; swaps--)
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{
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long sbit = nn & smask;
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long ebit = nn & emask;
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nn ^= sbit ^ (ebit ? smask : 0) /* zap sbit, put ebit value */
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^ ebit ^ (sbit ? emask : 0); /* zap ebit, put sbit value */
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smask <<= 1;
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emask >>= 1;
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}
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return scm_from_long (nn);
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}
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else
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{
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/* avoid creating a new bignum if reversing only 0 or 1 bits */
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if (ee - ss <= 1)
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return n;
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b = scm_i_long2big (nn);
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goto big;
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}
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}
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else if (SCM_BIGP (n))
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{
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/* avoid creating a new bignum if reversing only 0 or 1 bits */
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if (ee - ss <= 1)
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return n;
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b = scm_i_clonebig (n, 1);
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big:
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ee--;
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for ( ; swaps > 0; swaps--)
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{
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int sbit = mpz_tstbit (SCM_I_BIG_MPZ (b), ss);
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int ebit = mpz_tstbit (SCM_I_BIG_MPZ (b), ee);
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if (sbit ^ ebit)
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{
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/* the two bits are different, flip them */
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if (sbit)
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{
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mpz_clrbit (SCM_I_BIG_MPZ (b), ss);
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mpz_setbit (SCM_I_BIG_MPZ (b), ee);
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}
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else
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{
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mpz_setbit (SCM_I_BIG_MPZ (b), ss);
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mpz_clrbit (SCM_I_BIG_MPZ (b), ee);
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}
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}
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ss++;
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ee--;
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}
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/* swapping zero bits into the high might make us fit a fixnum */
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return scm_i_normbig (b);
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}
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else
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SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_srfi60_integer_to_list, "integer->list", 1, 1, 0,
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(SCM n, SCM len),
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"Return bits from @var{n} in the form of a list of @code{#t} for\n"
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"1 and @code{#f} for 0. The least significant @var{len} bits\n"
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"are returned, and the first list element is the most\n"
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"significant of those bits. If @var{len} is not given, the\n"
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"default is @code{(integer-length @var{n})} (@pxref{Bitwise\n"
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"Operations}).\n"
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"\n"
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"@example\n"
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"(integer->list 6) @result{} (#t #t #f)\n"
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"(integer->list 1 4) @result{} (#f #f #f #t)\n"
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"@end example")
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#define FUNC_NAME s_scm_srfi60_integer_to_list
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{
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SCM ret = SCM_EOL;
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unsigned long ll, i;
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if (SCM_UNBNDP (len))
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len = scm_integer_length (n);
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ll = scm_to_ulong (len);
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if (SCM_I_INUMP (n))
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{
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long nn = SCM_I_INUM (n);
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for (i = 0; i < ll; i++)
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{
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unsigned long shift =
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(i < ((unsigned long) SCM_LONG_BIT-1))
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? i : ((unsigned long) SCM_LONG_BIT-1);
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int bit = (nn >> shift) & 1;
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ret = scm_cons (scm_from_bool (bit), ret);
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}
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}
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else if (SCM_BIGP (n))
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{
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for (i = 0; i < ll; i++)
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ret = scm_cons (scm_from_bool (mpz_tstbit (SCM_I_BIG_MPZ (n), i)),
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ret);
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scm_remember_upto_here_1 (n);
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}
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else
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SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
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return ret;
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_srfi60_list_to_integer, "list->integer", 1, 0, 0,
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(SCM lst),
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"Return an integer formed bitwise from the given @var{lst} list\n"
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"of booleans. Each boolean is @code{#t} for a 1 and @code{#f}\n"
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"for a 0. The first element becomes the most significant bit in\n"
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"the return.\n"
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"\n"
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"@example\n"
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"(list->integer '(#t #f #t #f)) @result{} 10\n"
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"@end example")
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#define FUNC_NAME s_scm_srfi60_list_to_integer
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{
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long len;
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/* strip high zero bits from lst; after this the length tells us whether
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an inum or bignum is required */
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while (scm_is_pair (lst) && scm_is_false (SCM_CAR (lst)))
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lst = SCM_CDR (lst);
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SCM_VALIDATE_LIST_COPYLEN (SCM_ARG1, lst, len);
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if (len <= SCM_I_FIXNUM_BIT - 1)
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{
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/* fits an inum (a positive inum) */
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long n = 0;
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while (scm_is_pair (lst))
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{
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n <<= 1;
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if (! scm_is_false (SCM_CAR (lst)))
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n++;
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lst = SCM_CDR (lst);
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}
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return SCM_I_MAKINUM (n);
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}
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else
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{
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/* need a bignum */
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SCM n = scm_i_ulong2big (0);
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while (scm_is_pair (lst))
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{
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len--;
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if (! scm_is_false (SCM_CAR (lst)))
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mpz_setbit (SCM_I_BIG_MPZ (n), len);
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lst = SCM_CDR (lst);
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}
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return n;
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}
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}
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#undef FUNC_NAME
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/* note: don't put "scm_srfi60_list_to_integer" arg on its own line, a
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newline breaks the snarfer */
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SCM_REGISTER_PROC (s_srfi60_booleans_to_integer, "booleans->integer", 0, 0, 1, scm_srfi60_list_to_integer);
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void
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scm_init_srfi_60 (void)
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{
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#ifndef SCM_MAGIC_SNARFER
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#include "srfi/srfi-60.x"
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#endif
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}
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