| 1 | /* srfi-60.c --- Integers as Bits |
| 2 | * |
| 3 | * Copyright (C) 2005 Free Software Foundation, Inc. |
| 4 | * |
| 5 | * This library is free software; you can redistribute it and/or |
| 6 | * modify it under the terms of the GNU Lesser General Public |
| 7 | * License as published by the Free Software Foundation; either |
| 8 | * version 2.1 of the License, or (at your option) any later version. |
| 9 | * |
| 10 | * This library is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | * Lesser General Public License for more details. |
| 14 | * |
| 15 | * You should have received a copy of the GNU Lesser General Public |
| 16 | * License along with this library; if not, write to the Free Software |
| 17 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 18 | */ |
| 19 | |
| 20 | #include <libguile.h> |
| 21 | #include "libguile/private-gc.h" /* for SCM_MIN */ |
| 22 | #include "srfi-60.h" |
| 23 | |
| 24 | |
| 25 | SCM_DEFINE (scm_srfi60_log2_binary_factors, "log2-binary-factors", 1, 0, 0, |
| 26 | (SCM n), |
| 27 | "Return a count of how many factors of 2 are present in @var{n}.\n" |
| 28 | "This is also the bit index of the lowest 1 bit in @var{n}. If\n" |
| 29 | "@var{n} is 0, the return is @math{-1}.\n" |
| 30 | "\n" |
| 31 | "@example\n" |
| 32 | "(log2-binary-factors 6) @result{} 1\n" |
| 33 | "(log2-binary-factors -8) @result{} 3\n" |
| 34 | "@end example") |
| 35 | #define FUNC_NAME s_scm_srfi60_log2_binary_factors |
| 36 | { |
| 37 | SCM ret = SCM_EOL; |
| 38 | |
| 39 | if (SCM_I_INUMP (n)) |
| 40 | { |
| 41 | long nn = SCM_I_INUM (n); |
| 42 | if (nn == 0) |
| 43 | return SCM_I_MAKINUM (-1); |
| 44 | nn = nn ^ (nn-1); /* 1 bits for each low 0 and lowest 1 */ |
| 45 | return scm_logcount (SCM_I_MAKINUM (nn >> 1)); |
| 46 | } |
| 47 | else if (SCM_BIGP (n)) |
| 48 | { |
| 49 | /* no need for scm_remember_upto_here_1 here, mpz_scan1 doesn't do |
| 50 | anything that could result in a gc */ |
| 51 | return SCM_I_MAKINUM (mpz_scan1 (SCM_I_BIG_MPZ (n), 0L)); |
| 52 | } |
| 53 | else |
| 54 | SCM_WRONG_TYPE_ARG (SCM_ARG1, n); |
| 55 | |
| 56 | return ret; |
| 57 | } |
| 58 | #undef FUNC_NAME |
| 59 | |
| 60 | |
| 61 | SCM_DEFINE (scm_srfi60_copy_bit, "copy-bit", 3, 0, 0, |
| 62 | (SCM index, SCM n, SCM bit), |
| 63 | "Return @var{n} with the bit at @var{index} set according to\n" |
| 64 | "@var{newbit}. @var{newbit} should be @code{#t} to set the bit\n" |
| 65 | "to 1, or @code{#f} to set it to 0. Bits other than at\n" |
| 66 | "@var{index} are unchanged in the return.\n" |
| 67 | "\n" |
| 68 | "@example\n" |
| 69 | "(copy-bit 1 #b0101 #t) @result{} 7\n" |
| 70 | "@end example") |
| 71 | #define FUNC_NAME s_scm_srfi60_copy_bit |
| 72 | { |
| 73 | SCM r; |
| 74 | unsigned long ii; |
| 75 | int bb; |
| 76 | |
| 77 | ii = scm_to_ulong (index); |
| 78 | bb = scm_to_bool (bit); |
| 79 | |
| 80 | if (SCM_I_INUMP (n)) |
| 81 | { |
| 82 | long nn = SCM_I_INUM (n); |
| 83 | |
| 84 | /* can't set high bit ii==SCM_LONG_BIT-1, that would change the sign, |
| 85 | which is not what's wanted */ |
| 86 | if (ii < SCM_LONG_BIT-1) |
| 87 | { |
| 88 | nn &= ~(1L << ii); /* zap bit at index */ |
| 89 | nn |= (bb << ii); /* insert desired bit */ |
| 90 | return scm_from_long (nn); |
| 91 | } |
| 92 | else |
| 93 | { |
| 94 | /* bits at ii==SCM_LONG_BIT-1 and above are all copies of the sign |
| 95 | bit, if this is already the desired "bit" value then no need to |
| 96 | make a new bignum value */ |
| 97 | if (bb == (nn < 0)) |
| 98 | return n; |
| 99 | |
| 100 | r = scm_i_long2big (nn); |
| 101 | goto big; |
| 102 | } |
| 103 | } |
| 104 | else if (SCM_BIGP (n)) |
| 105 | { |
| 106 | /* if the bit is already what's wanted then no need to make a new |
| 107 | bignum */ |
| 108 | if (bb == mpz_tstbit (SCM_I_BIG_MPZ (n), ii)) |
| 109 | return n; |
| 110 | |
| 111 | r = scm_i_clonebig (n, 1); |
| 112 | big: |
| 113 | if (bb) |
| 114 | mpz_setbit (SCM_I_BIG_MPZ (r), ii); |
| 115 | else |
| 116 | mpz_clrbit (SCM_I_BIG_MPZ (r), ii); |
| 117 | |
| 118 | /* changing a high bit might put the result into range of a fixnum */ |
| 119 | return scm_i_normbig (r); |
| 120 | } |
| 121 | else |
| 122 | SCM_WRONG_TYPE_ARG (SCM_ARG1, n); |
| 123 | } |
| 124 | #undef FUNC_NAME |
| 125 | |
| 126 | |
| 127 | SCM_DEFINE (scm_srfi60_rotate_bit_field, "rotate-bit-field", 4, 0, 0, |
| 128 | (SCM n, SCM count, SCM start, SCM end), |
| 129 | "Return @var{n} with the bit field from @var{start} (inclusive)\n" |
| 130 | "to @var{end} (exclusive) rotated upwards by @var{count} bits.\n" |
| 131 | "\n" |
| 132 | "@var{count} can be positive or negative, and it can be more\n" |
| 133 | "than the field width (it'll be reduced modulo the width).\n" |
| 134 | "\n" |
| 135 | "@example\n" |
| 136 | "(rotate-bit-field #b0110 2 1 4) @result{} #b1010\n" |
| 137 | "@end example") |
| 138 | #define FUNC_NAME s_scm_srfi60_rotate_bit_field |
| 139 | { |
| 140 | unsigned long ss = scm_to_ulong (start); |
| 141 | unsigned long ee = scm_to_ulong (end); |
| 142 | unsigned long ww, cc; |
| 143 | |
| 144 | SCM_ASSERT_RANGE (3, end, (ee >= ss)); |
| 145 | ww = ee - ss; |
| 146 | |
| 147 | cc = scm_to_ulong (scm_modulo (count, scm_difference (end, start))); |
| 148 | |
| 149 | if (SCM_I_INUMP (n)) |
| 150 | { |
| 151 | long nn = SCM_I_INUM (n); |
| 152 | |
| 153 | if (ee <= SCM_LONG_BIT-1) |
| 154 | { |
| 155 | /* all within a long */ |
| 156 | long below = nn & ((1L << ss) - 1); /* before start */ |
| 157 | long above = nn & (-1L << ee); /* above end */ |
| 158 | long fmask = (-1L << ss) & ((1L << ee) - 1); /* field mask */ |
| 159 | long ff = nn & fmask; /* field */ |
| 160 | |
| 161 | return scm_from_long (above |
| 162 | | ((ff << cc) & fmask) |
| 163 | | ((ff >> (ww-cc)) & fmask) |
| 164 | | below); |
| 165 | } |
| 166 | else |
| 167 | { |
| 168 | /* either no movement, or a field of only 0 or 1 bits, result |
| 169 | unchanged, avoid creating a bignum */ |
| 170 | if (cc == 0 || ww <= 1) |
| 171 | return n; |
| 172 | |
| 173 | n = scm_i_long2big (nn); |
| 174 | goto big; |
| 175 | } |
| 176 | } |
| 177 | else if (SCM_BIGP (n)) |
| 178 | { |
| 179 | mpz_t tmp; |
| 180 | SCM r; |
| 181 | |
| 182 | /* either no movement, or in a field of only 0 or 1 bits, result |
| 183 | unchanged, avoid creating a new bignum */ |
| 184 | if (cc == 0 || ww <= 1) |
| 185 | return n; |
| 186 | |
| 187 | big: |
| 188 | r = scm_i_ulong2big (0); |
| 189 | mpz_init (tmp); |
| 190 | |
| 191 | /* portion above end */ |
| 192 | mpz_fdiv_q_2exp (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (n), ee); |
| 193 | mpz_mul_2exp (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), ee); |
| 194 | |
| 195 | /* field high part, width-count bits from start go to start+count */ |
| 196 | mpz_fdiv_q_2exp (tmp, SCM_I_BIG_MPZ (n), ss); |
| 197 | mpz_fdiv_r_2exp (tmp, tmp, ww - cc); |
| 198 | mpz_mul_2exp (tmp, tmp, ss + cc); |
| 199 | mpz_ior (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), tmp); |
| 200 | |
| 201 | /* field high part, count bits from end-count go to start */ |
| 202 | mpz_fdiv_q_2exp (tmp, SCM_I_BIG_MPZ (n), ee - cc); |
| 203 | mpz_fdiv_r_2exp (tmp, tmp, cc); |
| 204 | mpz_mul_2exp (tmp, tmp, ss); |
| 205 | mpz_ior (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), tmp); |
| 206 | |
| 207 | /* portion below start */ |
| 208 | mpz_fdiv_r_2exp (tmp, SCM_I_BIG_MPZ (n), ss); |
| 209 | mpz_ior (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), tmp); |
| 210 | |
| 211 | mpz_clear (tmp); |
| 212 | |
| 213 | /* bits moved around might leave us in range of an inum */ |
| 214 | return scm_i_normbig (r); |
| 215 | } |
| 216 | else |
| 217 | SCM_WRONG_TYPE_ARG (SCM_ARG1, n); |
| 218 | } |
| 219 | #undef FUNC_NAME |
| 220 | |
| 221 | |
| 222 | SCM_DEFINE (scm_srfi60_reverse_bit_field, "reverse-bit-field", 3, 0, 0, |
| 223 | (SCM n, SCM start, SCM end), |
| 224 | "Return @var{n} with the bits between @var{start} (inclusive) to\n" |
| 225 | "@var{end} (exclusive) reversed.\n" |
| 226 | "\n" |
| 227 | "@example\n" |
| 228 | "(reverse-bit-field #b101001 2 4) @result{} #b100101\n" |
| 229 | "@end example") |
| 230 | #define FUNC_NAME s_scm_srfi60_reverse_bit_field |
| 231 | { |
| 232 | long ss = scm_to_long (start); |
| 233 | long ee = scm_to_long (end); |
| 234 | long swaps = (ee - ss) / 2; /* number of swaps */ |
| 235 | SCM b; |
| 236 | |
| 237 | if (SCM_I_INUMP (n)) |
| 238 | { |
| 239 | long nn = SCM_I_INUM (n); |
| 240 | |
| 241 | if (ee <= SCM_LONG_BIT-1) |
| 242 | { |
| 243 | /* all within a long */ |
| 244 | long smask = 1L << ss; |
| 245 | long emask = 1L << (ee-1); |
| 246 | for ( ; swaps > 0; swaps--) |
| 247 | { |
| 248 | long sbit = nn & smask; |
| 249 | long ebit = nn & emask; |
| 250 | nn ^= sbit ^ (ebit ? smask : 0) /* zap sbit, put ebit value */ |
| 251 | ^ ebit ^ (sbit ? emask : 0); /* zap ebit, put sbit value */ |
| 252 | |
| 253 | smask <<= 1; |
| 254 | emask >>= 1; |
| 255 | } |
| 256 | return scm_from_long (nn); |
| 257 | } |
| 258 | else |
| 259 | { |
| 260 | /* avoid creating a new bignum if reversing only 0 or 1 bits */ |
| 261 | if (ee - ss <= 1) |
| 262 | return n; |
| 263 | |
| 264 | b = scm_i_long2big (nn); |
| 265 | goto big; |
| 266 | } |
| 267 | } |
| 268 | else if (SCM_BIGP (n)) |
| 269 | { |
| 270 | /* avoid creating a new bignum if reversing only 0 or 1 bits */ |
| 271 | if (ee - ss <= 1) |
| 272 | return n; |
| 273 | |
| 274 | b = scm_i_clonebig (n, 1); |
| 275 | big: |
| 276 | |
| 277 | ee--; |
| 278 | for ( ; swaps > 0; swaps--) |
| 279 | { |
| 280 | int sbit = mpz_tstbit (SCM_I_BIG_MPZ (b), ss); |
| 281 | int ebit = mpz_tstbit (SCM_I_BIG_MPZ (b), ee); |
| 282 | if (sbit ^ ebit) |
| 283 | { |
| 284 | /* the two bits are different, flip them */ |
| 285 | if (sbit) |
| 286 | { |
| 287 | mpz_clrbit (SCM_I_BIG_MPZ (b), ss); |
| 288 | mpz_setbit (SCM_I_BIG_MPZ (b), ee); |
| 289 | } |
| 290 | else |
| 291 | { |
| 292 | mpz_setbit (SCM_I_BIG_MPZ (b), ss); |
| 293 | mpz_clrbit (SCM_I_BIG_MPZ (b), ee); |
| 294 | } |
| 295 | } |
| 296 | ss++; |
| 297 | ee--; |
| 298 | } |
| 299 | /* swapping zero bits into the high might make us fit a fixnum */ |
| 300 | return scm_i_normbig (b); |
| 301 | } |
| 302 | else |
| 303 | SCM_WRONG_TYPE_ARG (SCM_ARG1, n); |
| 304 | } |
| 305 | #undef FUNC_NAME |
| 306 | |
| 307 | |
| 308 | SCM_DEFINE (scm_srfi60_integer_to_list, "integer->list", 1, 1, 0, |
| 309 | (SCM n, SCM len), |
| 310 | "Return bits from @var{n} in the form of a list of @code{#t} for\n" |
| 311 | "1 and @code{#f} for 0. The least significant @var{len} bits\n" |
| 312 | "are returned, and the first list element is the most\n" |
| 313 | "significant of those bits. If @var{len} is not given, the\n" |
| 314 | "default is @code{(integer-length @var{n})} (@pxref{Bitwise\n" |
| 315 | "Operations}).\n" |
| 316 | "\n" |
| 317 | "@example\n" |
| 318 | "(integer->list 6) @result{} (#t #t #f)\n" |
| 319 | "(integer->list 1 4) @result{} (#f #f #f #t)\n" |
| 320 | "@end example") |
| 321 | #define FUNC_NAME s_scm_srfi60_integer_to_list |
| 322 | { |
| 323 | SCM ret = SCM_EOL; |
| 324 | unsigned long ll, i; |
| 325 | |
| 326 | if (SCM_UNBNDP (len)) |
| 327 | len = scm_integer_length (n); |
| 328 | ll = scm_to_ulong (len); |
| 329 | |
| 330 | if (SCM_I_INUMP (n)) |
| 331 | { |
| 332 | long nn = SCM_I_INUM (n); |
| 333 | for (i = 0; i < ll; i++) |
| 334 | { |
| 335 | unsigned long shift = SCM_MIN (i, (unsigned long) SCM_LONG_BIT-1); |
| 336 | int bit = (nn >> shift) & 1; |
| 337 | ret = scm_cons (scm_from_bool (bit), ret); |
| 338 | } |
| 339 | } |
| 340 | else if (SCM_BIGP (n)) |
| 341 | { |
| 342 | for (i = 0; i < ll; i++) |
| 343 | ret = scm_cons (scm_from_bool (mpz_tstbit (SCM_I_BIG_MPZ (n), i)), |
| 344 | ret); |
| 345 | scm_remember_upto_here_1 (n); |
| 346 | } |
| 347 | else |
| 348 | SCM_WRONG_TYPE_ARG (SCM_ARG1, n); |
| 349 | |
| 350 | return ret; |
| 351 | } |
| 352 | #undef FUNC_NAME |
| 353 | |
| 354 | |
| 355 | SCM_DEFINE (scm_srfi60_list_to_integer, "list->integer", 1, 0, 0, |
| 356 | (SCM lst), |
| 357 | "Return an integer formed bitwise from the given @var{lst} list\n" |
| 358 | "of booleans. Each boolean is @code{#t} for a 1 and @code{#f}\n" |
| 359 | "for a 0. The first element becomes the most significant bit in\n" |
| 360 | "the return.\n" |
| 361 | "\n" |
| 362 | "@example\n" |
| 363 | "(list->integer '(#t #f #t #f)) @result{} 10\n" |
| 364 | "@end example") |
| 365 | #define FUNC_NAME s_scm_srfi60_list_to_integer |
| 366 | { |
| 367 | long len; |
| 368 | |
| 369 | /* strip high zero bits from lst; after this the length tells us whether |
| 370 | an inum or bignum is required */ |
| 371 | while (scm_is_pair (lst) && scm_is_false (SCM_CAR (lst))) |
| 372 | lst = SCM_CDR (lst); |
| 373 | |
| 374 | SCM_VALIDATE_LIST_COPYLEN (SCM_ARG1, lst, len); |
| 375 | |
| 376 | if (len <= SCM_I_FIXNUM_BIT - 1) |
| 377 | { |
| 378 | /* fits an inum (a positive inum) */ |
| 379 | long n = 0; |
| 380 | while (scm_is_pair (lst)) |
| 381 | { |
| 382 | n <<= 1; |
| 383 | if (! scm_is_false (SCM_CAR (lst))) |
| 384 | n++; |
| 385 | lst = SCM_CDR (lst); |
| 386 | } |
| 387 | return SCM_I_MAKINUM (n); |
| 388 | } |
| 389 | else |
| 390 | { |
| 391 | /* need a bignum */ |
| 392 | SCM n = scm_i_ulong2big (0); |
| 393 | while (scm_is_pair (lst)) |
| 394 | { |
| 395 | len--; |
| 396 | if (! scm_is_false (SCM_CAR (lst))) |
| 397 | mpz_setbit (SCM_I_BIG_MPZ (n), len); |
| 398 | lst = SCM_CDR (lst); |
| 399 | } |
| 400 | return n; |
| 401 | } |
| 402 | } |
| 403 | #undef FUNC_NAME |
| 404 | |
| 405 | |
| 406 | SCM_REGISTER_PROC (s_srfi60_booleans_to_integer, "booleans->integer", 0, 0, 1, |
| 407 | scm_srfi60_list_to_integer); |
| 408 | |
| 409 | |
| 410 | void |
| 411 | scm_init_srfi_60 (void) |
| 412 | { |
| 413 | #ifndef SCM_MAGIC_SNARFER |
| 414 | #include "srfi/srfi-60.x" |
| 415 | #endif |
| 416 | } |