linux/tools/power/cpupower/utils/helpers/bitmask.c
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   1// SPDX-License-Identifier: GPL-2.0
   2#include <stdio.h>
   3#include <stdlib.h>
   4#include <string.h>
   5
   6#include <helpers/bitmask.h>
   7
   8/* How many bits in an unsigned long */
   9#define bitsperlong (8 * sizeof(unsigned long))
  10
  11/* howmany(a,b) : how many elements of size b needed to hold all of a */
  12#define howmany(x, y) (((x)+((y)-1))/(y))
  13
  14/* How many longs in mask of n bits */
  15#define longsperbits(n) howmany(n, bitsperlong)
  16
  17#define max(a, b) ((a) > (b) ? (a) : (b))
  18
  19/*
  20 * Allocate and free `struct bitmask *`
  21 */
  22
  23/* Allocate a new `struct bitmask` with a size of n bits */
  24struct bitmask *bitmask_alloc(unsigned int n)
  25{
  26        struct bitmask *bmp;
  27
  28        bmp = malloc(sizeof(*bmp));
  29        if (bmp == 0)
  30                return 0;
  31        bmp->size = n;
  32        bmp->maskp = calloc(longsperbits(n), sizeof(unsigned long));
  33        if (bmp->maskp == 0) {
  34                free(bmp);
  35                return 0;
  36        }
  37        return bmp;
  38}
  39
  40/* Free `struct bitmask` */
  41void bitmask_free(struct bitmask *bmp)
  42{
  43        if (bmp == 0)
  44                return;
  45        free(bmp->maskp);
  46        bmp->maskp = (unsigned long *)0xdeadcdef;  /* double free tripwire */
  47        free(bmp);
  48}
  49
  50/*
  51 * The routines _getbit() and _setbit() are the only
  52 * routines that actually understand the layout of bmp->maskp[].
  53 *
  54 * On little endian architectures, this could simply be an array of
  55 * bytes.  But the kernel layout of bitmasks _is_ visible to userspace
  56 * via the sched_(set/get)affinity calls in Linux 2.6, and on big
  57 * endian architectures, it is painfully obvious that this is an
  58 * array of unsigned longs.
  59 */
  60
  61/* Return the value (0 or 1) of bit n in bitmask bmp */
  62static unsigned int _getbit(const struct bitmask *bmp, unsigned int n)
  63{
  64        if (n < bmp->size)
  65                return (bmp->maskp[n/bitsperlong] >> (n % bitsperlong)) & 1;
  66        else
  67                return 0;
  68}
  69
  70/* Set bit n in bitmask bmp to value v (0 or 1) */
  71static void _setbit(struct bitmask *bmp, unsigned int n, unsigned int v)
  72{
  73        if (n < bmp->size) {
  74                if (v)
  75                        bmp->maskp[n/bitsperlong] |= 1UL << (n % bitsperlong);
  76                else
  77                        bmp->maskp[n/bitsperlong] &=
  78                                ~(1UL << (n % bitsperlong));
  79        }
  80}
  81
  82/*
  83 * When parsing bitmask lists, only allow numbers, separated by one
  84 * of the allowed next characters.
  85 *
  86 * The parameter 'sret' is the return from a sscanf "%u%c".  It is
  87 * -1 if the sscanf input string was empty.  It is 0 if the first
  88 * character in the sscanf input string was not a decimal number.
  89 * It is 1 if the unsigned number matching the "%u" was the end of the
  90 * input string.  It is 2 if one or more additional characters followed
  91 * the matched unsigned number.  If it is 2, then 'nextc' is the first
  92 * character following the number.  The parameter 'ok_next_chars'
  93 * is the nul-terminated list of allowed next characters.
  94 *
  95 * The mask term just scanned was ok if and only if either the numbers
  96 * matching the %u were all of the input or if the next character in
  97 * the input past the numbers was one of the allowed next characters.
  98 */
  99static int scan_was_ok(int sret, char nextc, const char *ok_next_chars)
 100{
 101        return sret == 1 ||
 102                (sret == 2 && strchr(ok_next_chars, nextc) != NULL);
 103}
 104
 105static const char *nexttoken(const char *q,  int sep)
 106{
 107        if (q)
 108                q = strchr(q, sep);
 109        if (q)
 110                q++;
 111        return q;
 112}
 113
 114/* Set a single bit i in bitmask */
 115struct bitmask *bitmask_setbit(struct bitmask *bmp, unsigned int i)
 116{
 117        _setbit(bmp, i, 1);
 118        return bmp;
 119}
 120
 121/* Set all bits in bitmask: bmp = ~0 */
 122struct bitmask *bitmask_setall(struct bitmask *bmp)
 123{
 124        unsigned int i;
 125        for (i = 0; i < bmp->size; i++)
 126                _setbit(bmp, i, 1);
 127        return bmp;
 128}
 129
 130/* Clear all bits in bitmask: bmp = 0 */
 131struct bitmask *bitmask_clearall(struct bitmask *bmp)
 132{
 133        unsigned int i;
 134        for (i = 0; i < bmp->size; i++)
 135                _setbit(bmp, i, 0);
 136        return bmp;
 137}
 138
 139/* True if all bits are clear */
 140int bitmask_isallclear(const struct bitmask *bmp)
 141{
 142        unsigned int i;
 143        for (i = 0; i < bmp->size; i++)
 144                if (_getbit(bmp, i))
 145                        return 0;
 146        return 1;
 147}
 148
 149/* True if specified bit i is set */
 150int bitmask_isbitset(const struct bitmask *bmp, unsigned int i)
 151{
 152        return _getbit(bmp, i);
 153}
 154
 155/* Number of lowest set bit (min) */
 156unsigned int bitmask_first(const struct bitmask *bmp)
 157{
 158        return bitmask_next(bmp, 0);
 159}
 160
 161/* Number of highest set bit (max) */
 162unsigned int bitmask_last(const struct bitmask *bmp)
 163{
 164        unsigned int i;
 165        unsigned int m = bmp->size;
 166        for (i = 0; i < bmp->size; i++)
 167                if (_getbit(bmp, i))
 168                        m = i;
 169        return m;
 170}
 171
 172/* Number of next set bit at or above given bit i */
 173unsigned int bitmask_next(const struct bitmask *bmp, unsigned int i)
 174{
 175        unsigned int n;
 176        for (n = i; n < bmp->size; n++)
 177                if (_getbit(bmp, n))
 178                        break;
 179        return n;
 180}
 181
 182/*
 183 * Parses a comma-separated list of numbers and ranges of numbers,
 184 * with optional ':%u' strides modifying ranges, into provided bitmask.
 185 * Some examples of input lists and their equivalent simple list:
 186 *      Input           Equivalent to
 187 *      0-3             0,1,2,3
 188 *      0-7:2           0,2,4,6
 189 *      1,3,5-7         1,3,5,6,7
 190 *      0-3:2,8-15:4    0,2,8,12
 191 */
 192int bitmask_parselist(const char *buf, struct bitmask *bmp)
 193{
 194        const char *p, *q;
 195
 196        bitmask_clearall(bmp);
 197
 198        q = buf;
 199        while (p = q, q = nexttoken(q, ','), p) {
 200                unsigned int a;         /* begin of range */
 201                unsigned int b;         /* end of range */
 202                unsigned int s;         /* stride */
 203                const char *c1, *c2;    /* next tokens after '-' or ',' */
 204                char nextc;             /* char after sscanf %u match */
 205                int sret;               /* sscanf return (number of matches) */
 206
 207                sret = sscanf(p, "%u%c", &a, &nextc);
 208                if (!scan_was_ok(sret, nextc, ",-"))
 209                        goto err;
 210                b = a;
 211                s = 1;
 212                c1 = nexttoken(p, '-');
 213                c2 = nexttoken(p, ',');
 214                if (c1 != NULL && (c2 == NULL || c1 < c2)) {
 215                        sret = sscanf(c1, "%u%c", &b, &nextc);
 216                        if (!scan_was_ok(sret, nextc, ",:"))
 217                                goto err;
 218                        c1 = nexttoken(c1, ':');
 219                        if (c1 != NULL && (c2 == NULL || c1 < c2)) {
 220                                sret = sscanf(c1, "%u%c", &s, &nextc);
 221                                if (!scan_was_ok(sret, nextc, ","))
 222                                        goto err;
 223                        }
 224                }
 225                if (!(a <= b))
 226                        goto err;
 227                if (b >= bmp->size)
 228                        goto err;
 229                while (a <= b) {
 230                        _setbit(bmp, a, 1);
 231                        a += s;
 232                }
 233        }
 234        return 0;
 235err:
 236        bitmask_clearall(bmp);
 237        return -1;
 238}
 239
 240/*
 241 * emit(buf, buflen, rbot, rtop, len)
 242 *
 243 * Helper routine for bitmask_displaylist().  Write decimal number
 244 * or range to buf+len, suppressing output past buf+buflen, with optional
 245 * comma-prefix.  Return len of what would be written to buf, if it
 246 * all fit.
 247 */
 248
 249static inline int emit(char *buf, int buflen, int rbot, int rtop, int len)
 250{
 251        if (len > 0)
 252                len += snprintf(buf + len, max(buflen - len, 0), ",");
 253        if (rbot == rtop)
 254                len += snprintf(buf + len, max(buflen - len, 0), "%d", rbot);
 255        else
 256                len += snprintf(buf + len, max(buflen - len, 0), "%d-%d",
 257                                rbot, rtop);
 258        return len;
 259}
 260
 261/*
 262 * Write decimal list representation of bmp to buf.
 263 *
 264 * Output format is a comma-separated list of decimal numbers and
 265 * ranges.  Consecutively set bits are shown as two hyphen-separated
 266 * decimal numbers, the smallest and largest bit numbers set in
 267 * the range.  Output format is compatible with the format
 268 * accepted as input by bitmap_parselist().
 269 *
 270 * The return value is the number of characters which would be
 271 * generated for the given input, excluding the trailing '\0', as
 272 * per ISO C99.
 273 */
 274
 275int bitmask_displaylist(char *buf, int buflen, const struct bitmask *bmp)
 276{
 277        int len = 0;
 278        /* current bit is 'cur', most recently seen range is [rbot, rtop] */
 279        unsigned int cur, rbot, rtop;
 280
 281        if (buflen > 0)
 282                *buf = 0;
 283        rbot = cur = bitmask_first(bmp);
 284        while (cur < bmp->size) {
 285                rtop = cur;
 286                cur = bitmask_next(bmp, cur+1);
 287                if (cur >= bmp->size || cur > rtop + 1) {
 288                        len = emit(buf, buflen, rbot, rtop, len);
 289                        rbot = cur;
 290                }
 291        }
 292        return len;
 293}
 294