Root/lib/bitmap.c

1/*
2 * lib/bitmap.c
3 * Helper functions for bitmap.h.
4 *
5 * This source code is licensed under the GNU General Public License,
6 * Version 2. See the file COPYING for more details.
7 */
8#include <linux/module.h>
9#include <linux/ctype.h>
10#include <linux/errno.h>
11#include <linux/bitmap.h>
12#include <linux/bitops.h>
13#include <asm/uaccess.h>
14
15/*
16 * bitmaps provide an array of bits, implemented using an an
17 * array of unsigned longs. The number of valid bits in a
18 * given bitmap does _not_ need to be an exact multiple of
19 * BITS_PER_LONG.
20 *
21 * The possible unused bits in the last, partially used word
22 * of a bitmap are 'don't care'. The implementation makes
23 * no particular effort to keep them zero. It ensures that
24 * their value will not affect the results of any operation.
25 * The bitmap operations that return Boolean (bitmap_empty,
26 * for example) or scalar (bitmap_weight, for example) results
27 * carefully filter out these unused bits from impacting their
28 * results.
29 *
30 * These operations actually hold to a slightly stronger rule:
31 * if you don't input any bitmaps to these ops that have some
32 * unused bits set, then they won't output any set unused bits
33 * in output bitmaps.
34 *
35 * The byte ordering of bitmaps is more natural on little
36 * endian architectures. See the big-endian headers
37 * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h
38 * for the best explanations of this ordering.
39 */
40
41int __bitmap_empty(const unsigned long *bitmap, int bits)
42{
43    int k, lim = bits/BITS_PER_LONG;
44    for (k = 0; k < lim; ++k)
45        if (bitmap[k])
46            return 0;
47
48    if (bits % BITS_PER_LONG)
49        if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
50            return 0;
51
52    return 1;
53}
54EXPORT_SYMBOL(__bitmap_empty);
55
56int __bitmap_full(const unsigned long *bitmap, int bits)
57{
58    int k, lim = bits/BITS_PER_LONG;
59    for (k = 0; k < lim; ++k)
60        if (~bitmap[k])
61            return 0;
62
63    if (bits % BITS_PER_LONG)
64        if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
65            return 0;
66
67    return 1;
68}
69EXPORT_SYMBOL(__bitmap_full);
70
71int __bitmap_equal(const unsigned long *bitmap1,
72        const unsigned long *bitmap2, int bits)
73{
74    int k, lim = bits/BITS_PER_LONG;
75    for (k = 0; k < lim; ++k)
76        if (bitmap1[k] != bitmap2[k])
77            return 0;
78
79    if (bits % BITS_PER_LONG)
80        if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
81            return 0;
82
83    return 1;
84}
85EXPORT_SYMBOL(__bitmap_equal);
86
87void __bitmap_complement(unsigned long *dst, const unsigned long *src, int bits)
88{
89    int k, lim = bits/BITS_PER_LONG;
90    for (k = 0; k < lim; ++k)
91        dst[k] = ~src[k];
92
93    if (bits % BITS_PER_LONG)
94        dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits);
95}
96EXPORT_SYMBOL(__bitmap_complement);
97
98/**
99 * __bitmap_shift_right - logical right shift of the bits in a bitmap
100 * @dst : destination bitmap
101 * @src : source bitmap
102 * @shift : shift by this many bits
103 * @bits : bitmap size, in bits
104 *
105 * Shifting right (dividing) means moving bits in the MS -> LS bit
106 * direction. Zeros are fed into the vacated MS positions and the
107 * LS bits shifted off the bottom are lost.
108 */
109void __bitmap_shift_right(unsigned long *dst,
110            const unsigned long *src, int shift, int bits)
111{
112    int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
113    int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
114    unsigned long mask = (1UL << left) - 1;
115    for (k = 0; off + k < lim; ++k) {
116        unsigned long upper, lower;
117
118        /*
119         * If shift is not word aligned, take lower rem bits of
120         * word above and make them the top rem bits of result.
121         */
122        if (!rem || off + k + 1 >= lim)
123            upper = 0;
124        else {
125            upper = src[off + k + 1];
126            if (off + k + 1 == lim - 1 && left)
127                upper &= mask;
128        }
129        lower = src[off + k];
130        if (left && off + k == lim - 1)
131            lower &= mask;
132        dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
133        if (left && k == lim - 1)
134            dst[k] &= mask;
135    }
136    if (off)
137        memset(&dst[lim - off], 0, off*sizeof(unsigned long));
138}
139EXPORT_SYMBOL(__bitmap_shift_right);
140
141
142/**
143 * __bitmap_shift_left - logical left shift of the bits in a bitmap
144 * @dst : destination bitmap
145 * @src : source bitmap
146 * @shift : shift by this many bits
147 * @bits : bitmap size, in bits
148 *
149 * Shifting left (multiplying) means moving bits in the LS -> MS
150 * direction. Zeros are fed into the vacated LS bit positions
151 * and those MS bits shifted off the top are lost.
152 */
153
154void __bitmap_shift_left(unsigned long *dst,
155            const unsigned long *src, int shift, int bits)
156{
157    int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
158    int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
159    for (k = lim - off - 1; k >= 0; --k) {
160        unsigned long upper, lower;
161
162        /*
163         * If shift is not word aligned, take upper rem bits of
164         * word below and make them the bottom rem bits of result.
165         */
166        if (rem && k > 0)
167            lower = src[k - 1];
168        else
169            lower = 0;
170        upper = src[k];
171        if (left && k == lim - 1)
172            upper &= (1UL << left) - 1;
173        dst[k + off] = lower >> (BITS_PER_LONG - rem) | upper << rem;
174        if (left && k + off == lim - 1)
175            dst[k + off] &= (1UL << left) - 1;
176    }
177    if (off)
178        memset(dst, 0, off*sizeof(unsigned long));
179}
180EXPORT_SYMBOL(__bitmap_shift_left);
181
182int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
183                const unsigned long *bitmap2, int bits)
184{
185    int k;
186    int nr = BITS_TO_LONGS(bits);
187    unsigned long result = 0;
188
189    for (k = 0; k < nr; k++)
190        result |= (dst[k] = bitmap1[k] & bitmap2[k]);
191    return result != 0;
192}
193EXPORT_SYMBOL(__bitmap_and);
194
195void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
196                const unsigned long *bitmap2, int bits)
197{
198    int k;
199    int nr = BITS_TO_LONGS(bits);
200
201    for (k = 0; k < nr; k++)
202        dst[k] = bitmap1[k] | bitmap2[k];
203}
204EXPORT_SYMBOL(__bitmap_or);
205
206void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
207                const unsigned long *bitmap2, int bits)
208{
209    int k;
210    int nr = BITS_TO_LONGS(bits);
211
212    for (k = 0; k < nr; k++)
213        dst[k] = bitmap1[k] ^ bitmap2[k];
214}
215EXPORT_SYMBOL(__bitmap_xor);
216
217int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
218                const unsigned long *bitmap2, int bits)
219{
220    int k;
221    int nr = BITS_TO_LONGS(bits);
222    unsigned long result = 0;
223
224    for (k = 0; k < nr; k++)
225        result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
226    return result != 0;
227}
228EXPORT_SYMBOL(__bitmap_andnot);
229
230int __bitmap_intersects(const unsigned long *bitmap1,
231                const unsigned long *bitmap2, int bits)
232{
233    int k, lim = bits/BITS_PER_LONG;
234    for (k = 0; k < lim; ++k)
235        if (bitmap1[k] & bitmap2[k])
236            return 1;
237
238    if (bits % BITS_PER_LONG)
239        if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
240            return 1;
241    return 0;
242}
243EXPORT_SYMBOL(__bitmap_intersects);
244
245int __bitmap_subset(const unsigned long *bitmap1,
246                const unsigned long *bitmap2, int bits)
247{
248    int k, lim = bits/BITS_PER_LONG;
249    for (k = 0; k < lim; ++k)
250        if (bitmap1[k] & ~bitmap2[k])
251            return 0;
252
253    if (bits % BITS_PER_LONG)
254        if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
255            return 0;
256    return 1;
257}
258EXPORT_SYMBOL(__bitmap_subset);
259
260int __bitmap_weight(const unsigned long *bitmap, int bits)
261{
262    int k, w = 0, lim = bits/BITS_PER_LONG;
263
264    for (k = 0; k < lim; k++)
265        w += hweight_long(bitmap[k]);
266
267    if (bits % BITS_PER_LONG)
268        w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));
269
270    return w;
271}
272EXPORT_SYMBOL(__bitmap_weight);
273
274#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))
275
276void bitmap_set(unsigned long *map, int start, int nr)
277{
278    unsigned long *p = map + BIT_WORD(start);
279    const int size = start + nr;
280    int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
281    unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
282
283    while (nr - bits_to_set >= 0) {
284        *p |= mask_to_set;
285        nr -= bits_to_set;
286        bits_to_set = BITS_PER_LONG;
287        mask_to_set = ~0UL;
288        p++;
289    }
290    if (nr) {
291        mask_to_set &= BITMAP_LAST_WORD_MASK(size);
292        *p |= mask_to_set;
293    }
294}
295EXPORT_SYMBOL(bitmap_set);
296
297void bitmap_clear(unsigned long *map, int start, int nr)
298{
299    unsigned long *p = map + BIT_WORD(start);
300    const int size = start + nr;
301    int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
302    unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
303
304    while (nr - bits_to_clear >= 0) {
305        *p &= ~mask_to_clear;
306        nr -= bits_to_clear;
307        bits_to_clear = BITS_PER_LONG;
308        mask_to_clear = ~0UL;
309        p++;
310    }
311    if (nr) {
312        mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
313        *p &= ~mask_to_clear;
314    }
315}
316EXPORT_SYMBOL(bitmap_clear);
317
318/*
319 * bitmap_find_next_zero_area - find a contiguous aligned zero area
320 * @map: The address to base the search on
321 * @size: The bitmap size in bits
322 * @start: The bitnumber to start searching at
323 * @nr: The number of zeroed bits we're looking for
324 * @align_mask: Alignment mask for zero area
325 *
326 * The @align_mask should be one less than a power of 2; the effect is that
327 * the bit offset of all zero areas this function finds is multiples of that
328 * power of 2. A @align_mask of 0 means no alignment is required.
329 */
330unsigned long bitmap_find_next_zero_area(unsigned long *map,
331                     unsigned long size,
332                     unsigned long start,
333                     unsigned int nr,
334                     unsigned long align_mask)
335{
336    unsigned long index, end, i;
337again:
338    index = find_next_zero_bit(map, size, start);
339
340    /* Align allocation */
341    index = __ALIGN_MASK(index, align_mask);
342
343    end = index + nr;
344    if (end > size)
345        return end;
346    i = find_next_bit(map, end, index);
347    if (i < end) {
348        start = i + 1;
349        goto again;
350    }
351    return index;
352}
353EXPORT_SYMBOL(bitmap_find_next_zero_area);
354
355/*
356 * Bitmap printing & parsing functions: first version by Bill Irwin,
357 * second version by Paul Jackson, third by Joe Korty.
358 */
359
360#define CHUNKSZ 32
361#define nbits_to_hold_value(val) fls(val)
362#define unhex(c) (isdigit(c) ? (c - '0') : (toupper(c) - 'A' + 10))
363#define BASEDEC 10 /* fancier cpuset lists input in decimal */
364
365/**
366 * bitmap_scnprintf - convert bitmap to an ASCII hex string.
367 * @buf: byte buffer into which string is placed
368 * @buflen: reserved size of @buf, in bytes
369 * @maskp: pointer to bitmap to convert
370 * @nmaskbits: size of bitmap, in bits
371 *
372 * Exactly @nmaskbits bits are displayed. Hex digits are grouped into
373 * comma-separated sets of eight digits per set.
374 */
375int bitmap_scnprintf(char *buf, unsigned int buflen,
376    const unsigned long *maskp, int nmaskbits)
377{
378    int i, word, bit, len = 0;
379    unsigned long val;
380    const char *sep = "";
381    int chunksz;
382    u32 chunkmask;
383
384    chunksz = nmaskbits & (CHUNKSZ - 1);
385    if (chunksz == 0)
386        chunksz = CHUNKSZ;
387
388    i = ALIGN(nmaskbits, CHUNKSZ) - CHUNKSZ;
389    for (; i >= 0; i -= CHUNKSZ) {
390        chunkmask = ((1ULL << chunksz) - 1);
391        word = i / BITS_PER_LONG;
392        bit = i % BITS_PER_LONG;
393        val = (maskp[word] >> bit) & chunkmask;
394        len += scnprintf(buf+len, buflen-len, "%s%0*lx", sep,
395            (chunksz+3)/4, val);
396        chunksz = CHUNKSZ;
397        sep = ",";
398    }
399    return len;
400}
401EXPORT_SYMBOL(bitmap_scnprintf);
402
403/**
404 * __bitmap_parse - convert an ASCII hex string into a bitmap.
405 * @buf: pointer to buffer containing string.
406 * @buflen: buffer size in bytes. If string is smaller than this
407 * then it must be terminated with a \0.
408 * @is_user: location of buffer, 0 indicates kernel space
409 * @maskp: pointer to bitmap array that will contain result.
410 * @nmaskbits: size of bitmap, in bits.
411 *
412 * Commas group hex digits into chunks. Each chunk defines exactly 32
413 * bits of the resultant bitmask. No chunk may specify a value larger
414 * than 32 bits (%-EOVERFLOW), and if a chunk specifies a smaller value
415 * then leading 0-bits are prepended. %-EINVAL is returned for illegal
416 * characters and for grouping errors such as "1,,5", ",44", "," and "".
417 * Leading and trailing whitespace accepted, but not embedded whitespace.
418 */
419int __bitmap_parse(const char *buf, unsigned int buflen,
420        int is_user, unsigned long *maskp,
421        int nmaskbits)
422{
423    int c, old_c, totaldigits, ndigits, nchunks, nbits;
424    u32 chunk;
425    const char __user *ubuf = buf;
426
427    bitmap_zero(maskp, nmaskbits);
428
429    nchunks = nbits = totaldigits = c = 0;
430    do {
431        chunk = ndigits = 0;
432
433        /* Get the next chunk of the bitmap */
434        while (buflen) {
435            old_c = c;
436            if (is_user) {
437                if (__get_user(c, ubuf++))
438                    return -EFAULT;
439            }
440            else
441                c = *buf++;
442            buflen--;
443            if (isspace(c))
444                continue;
445
446            /*
447             * If the last character was a space and the current
448             * character isn't '\0', we've got embedded whitespace.
449             * This is a no-no, so throw an error.
450             */
451            if (totaldigits && c && isspace(old_c))
452                return -EINVAL;
453
454            /* A '\0' or a ',' signal the end of the chunk */
455            if (c == '\0' || c == ',')
456                break;
457
458            if (!isxdigit(c))
459                return -EINVAL;
460
461            /*
462             * Make sure there are at least 4 free bits in 'chunk'.
463             * If not, this hexdigit will overflow 'chunk', so
464             * throw an error.
465             */
466            if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1))
467                return -EOVERFLOW;
468
469            chunk = (chunk << 4) | unhex(c);
470            ndigits++; totaldigits++;
471        }
472        if (ndigits == 0)
473            return -EINVAL;
474        if (nchunks == 0 && chunk == 0)
475            continue;
476
477        __bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits);
478        *maskp |= chunk;
479        nchunks++;
480        nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
481        if (nbits > nmaskbits)
482            return -EOVERFLOW;
483    } while (buflen && c == ',');
484
485    return 0;
486}
487EXPORT_SYMBOL(__bitmap_parse);
488
489/**
490 * bitmap_parse_user - convert an ASCII hex string in a user buffer into a bitmap
491 *
492 * @ubuf: pointer to user buffer containing string.
493 * @ulen: buffer size in bytes. If string is smaller than this
494 * then it must be terminated with a \0.
495 * @maskp: pointer to bitmap array that will contain result.
496 * @nmaskbits: size of bitmap, in bits.
497 *
498 * Wrapper for __bitmap_parse(), providing it with user buffer.
499 *
500 * We cannot have this as an inline function in bitmap.h because it needs
501 * linux/uaccess.h to get the access_ok() declaration and this causes
502 * cyclic dependencies.
503 */
504int bitmap_parse_user(const char __user *ubuf,
505            unsigned int ulen, unsigned long *maskp,
506            int nmaskbits)
507{
508    if (!access_ok(VERIFY_READ, ubuf, ulen))
509        return -EFAULT;
510    return __bitmap_parse((const char *)ubuf, ulen, 1, maskp, nmaskbits);
511}
512EXPORT_SYMBOL(bitmap_parse_user);
513
514/*
515 * bscnl_emit(buf, buflen, rbot, rtop, bp)
516 *
517 * Helper routine for bitmap_scnlistprintf(). Write decimal number
518 * or range to buf, suppressing output past buf+buflen, with optional
519 * comma-prefix. Return len of what would be written to buf, if it
520 * all fit.
521 */
522static inline int bscnl_emit(char *buf, int buflen, int rbot, int rtop, int len)
523{
524    if (len > 0)
525        len += scnprintf(buf + len, buflen - len, ",");
526    if (rbot == rtop)
527        len += scnprintf(buf + len, buflen - len, "%d", rbot);
528    else
529        len += scnprintf(buf + len, buflen - len, "%d-%d", rbot, rtop);
530    return len;
531}
532
533/**
534 * bitmap_scnlistprintf - convert bitmap to list format ASCII string
535 * @buf: byte buffer into which string is placed
536 * @buflen: reserved size of @buf, in bytes
537 * @maskp: pointer to bitmap to convert
538 * @nmaskbits: size of bitmap, in bits
539 *
540 * Output format is a comma-separated list of decimal numbers and
541 * ranges. Consecutively set bits are shown as two hyphen-separated
542 * decimal numbers, the smallest and largest bit numbers set in
543 * the range. Output format is compatible with the format
544 * accepted as input by bitmap_parselist().
545 *
546 * The return value is the number of characters which would be
547 * generated for the given input, excluding the trailing '\0', as
548 * per ISO C99.
549 */
550int bitmap_scnlistprintf(char *buf, unsigned int buflen,
551    const unsigned long *maskp, int nmaskbits)
552{
553    int len = 0;
554    /* current bit is 'cur', most recently seen range is [rbot, rtop] */
555    int cur, rbot, rtop;
556
557    if (buflen == 0)
558        return 0;
559    buf[0] = 0;
560
561    rbot = cur = find_first_bit(maskp, nmaskbits);
562    while (cur < nmaskbits) {
563        rtop = cur;
564        cur = find_next_bit(maskp, nmaskbits, cur+1);
565        if (cur >= nmaskbits || cur > rtop + 1) {
566            len = bscnl_emit(buf, buflen, rbot, rtop, len);
567            rbot = cur;
568        }
569    }
570    return len;
571}
572EXPORT_SYMBOL(bitmap_scnlistprintf);
573
574/**
575 * bitmap_parselist - convert list format ASCII string to bitmap
576 * @bp: read nul-terminated user string from this buffer
577 * @maskp: write resulting mask here
578 * @nmaskbits: number of bits in mask to be written
579 *
580 * Input format is a comma-separated list of decimal numbers and
581 * ranges. Consecutively set bits are shown as two hyphen-separated
582 * decimal numbers, the smallest and largest bit numbers set in
583 * the range.
584 *
585 * Returns 0 on success, -errno on invalid input strings.
586 * Error values:
587 * %-EINVAL: second number in range smaller than first
588 * %-EINVAL: invalid character in string
589 * %-ERANGE: bit number specified too large for mask
590 */
591int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
592{
593    unsigned a, b;
594
595    bitmap_zero(maskp, nmaskbits);
596    do {
597        if (!isdigit(*bp))
598            return -EINVAL;
599        b = a = simple_strtoul(bp, (char **)&bp, BASEDEC);
600        if (*bp == '-') {
601            bp++;
602            if (!isdigit(*bp))
603                return -EINVAL;
604            b = simple_strtoul(bp, (char **)&bp, BASEDEC);
605        }
606        if (!(a <= b))
607            return -EINVAL;
608        if (b >= nmaskbits)
609            return -ERANGE;
610        while (a <= b) {
611            set_bit(a, maskp);
612            a++;
613        }
614        if (*bp == ',')
615            bp++;
616    } while (*bp != '\0' && *bp != '\n');
617    return 0;
618}
619EXPORT_SYMBOL(bitmap_parselist);
620
621/**
622 * bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap
623 * @buf: pointer to a bitmap
624 * @pos: a bit position in @buf (0 <= @pos < @bits)
625 * @bits: number of valid bit positions in @buf
626 *
627 * Map the bit at position @pos in @buf (of length @bits) to the
628 * ordinal of which set bit it is. If it is not set or if @pos
629 * is not a valid bit position, map to -1.
630 *
631 * If for example, just bits 4 through 7 are set in @buf, then @pos
632 * values 4 through 7 will get mapped to 0 through 3, respectively,
633 * and other @pos values will get mapped to 0. When @pos value 7
634 * gets mapped to (returns) @ord value 3 in this example, that means
635 * that bit 7 is the 3rd (starting with 0th) set bit in @buf.
636 *
637 * The bit positions 0 through @bits are valid positions in @buf.
638 */
639static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits)
640{
641    int i, ord;
642
643    if (pos < 0 || pos >= bits || !test_bit(pos, buf))
644        return -1;
645
646    i = find_first_bit(buf, bits);
647    ord = 0;
648    while (i < pos) {
649        i = find_next_bit(buf, bits, i + 1);
650             ord++;
651    }
652    BUG_ON(i != pos);
653
654    return ord;
655}
656
657/**
658 * bitmap_ord_to_pos - find position of n-th set bit in bitmap
659 * @buf: pointer to bitmap
660 * @ord: ordinal bit position (n-th set bit, n >= 0)
661 * @bits: number of valid bit positions in @buf
662 *
663 * Map the ordinal offset of bit @ord in @buf to its position in @buf.
664 * Value of @ord should be in range 0 <= @ord < weight(buf), else
665 * results are undefined.
666 *
667 * If for example, just bits 4 through 7 are set in @buf, then @ord
668 * values 0 through 3 will get mapped to 4 through 7, respectively,
669 * and all other @ord values return undefined values. When @ord value 3
670 * gets mapped to (returns) @pos value 7 in this example, that means
671 * that the 3rd set bit (starting with 0th) is at position 7 in @buf.
672 *
673 * The bit positions 0 through @bits are valid positions in @buf.
674 */
675static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
676{
677    int pos = 0;
678
679    if (ord >= 0 && ord < bits) {
680        int i;
681
682        for (i = find_first_bit(buf, bits);
683             i < bits && ord > 0;
684             i = find_next_bit(buf, bits, i + 1))
685                 ord--;
686        if (i < bits && ord == 0)
687            pos = i;
688    }
689
690    return pos;
691}
692
693/**
694 * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap
695 * @dst: remapped result
696 * @src: subset to be remapped
697 * @old: defines domain of map
698 * @new: defines range of map
699 * @bits: number of bits in each of these bitmaps
700 *
701 * Let @old and @new define a mapping of bit positions, such that
702 * whatever position is held by the n-th set bit in @old is mapped
703 * to the n-th set bit in @new. In the more general case, allowing
704 * for the possibility that the weight 'w' of @new is less than the
705 * weight of @old, map the position of the n-th set bit in @old to
706 * the position of the m-th set bit in @new, where m == n % w.
707 *
708 * If either of the @old and @new bitmaps are empty, or if @src and
709 * @dst point to the same location, then this routine copies @src
710 * to @dst.
711 *
712 * The positions of unset bits in @old are mapped to themselves
713 * (the identify map).
714 *
715 * Apply the above specified mapping to @src, placing the result in
716 * @dst, clearing any bits previously set in @dst.
717 *
718 * For example, lets say that @old has bits 4 through 7 set, and
719 * @new has bits 12 through 15 set. This defines the mapping of bit
720 * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
721 * bit positions unchanged. So if say @src comes into this routine
722 * with bits 1, 5 and 7 set, then @dst should leave with bits 1,
723 * 13 and 15 set.
724 */
725void bitmap_remap(unsigned long *dst, const unsigned long *src,
726        const unsigned long *old, const unsigned long *new,
727        int bits)
728{
729    int oldbit, w;
730
731    if (dst == src) /* following doesn't handle inplace remaps */
732        return;
733    bitmap_zero(dst, bits);
734
735    w = bitmap_weight(new, bits);
736    for_each_set_bit(oldbit, src, bits) {
737             int n = bitmap_pos_to_ord(old, oldbit, bits);
738
739        if (n < 0 || w == 0)
740            set_bit(oldbit, dst); /* identity map */
741        else
742            set_bit(bitmap_ord_to_pos(new, n % w, bits), dst);
743    }
744}
745EXPORT_SYMBOL(bitmap_remap);
746
747/**
748 * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit
749 * @oldbit: bit position to be mapped
750 * @old: defines domain of map
751 * @new: defines range of map
752 * @bits: number of bits in each of these bitmaps
753 *
754 * Let @old and @new define a mapping of bit positions, such that
755 * whatever position is held by the n-th set bit in @old is mapped
756 * to the n-th set bit in @new. In the more general case, allowing
757 * for the possibility that the weight 'w' of @new is less than the
758 * weight of @old, map the position of the n-th set bit in @old to
759 * the position of the m-th set bit in @new, where m == n % w.
760 *
761 * The positions of unset bits in @old are mapped to themselves
762 * (the identify map).
763 *
764 * Apply the above specified mapping to bit position @oldbit, returning
765 * the new bit position.
766 *
767 * For example, lets say that @old has bits 4 through 7 set, and
768 * @new has bits 12 through 15 set. This defines the mapping of bit
769 * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
770 * bit positions unchanged. So if say @oldbit is 5, then this routine
771 * returns 13.
772 */
773int bitmap_bitremap(int oldbit, const unsigned long *old,
774                const unsigned long *new, int bits)
775{
776    int w = bitmap_weight(new, bits);
777    int n = bitmap_pos_to_ord(old, oldbit, bits);
778    if (n < 0 || w == 0)
779        return oldbit;
780    else
781        return bitmap_ord_to_pos(new, n % w, bits);
782}
783EXPORT_SYMBOL(bitmap_bitremap);
784
785/**
786 * bitmap_onto - translate one bitmap relative to another
787 * @dst: resulting translated bitmap
788 * @orig: original untranslated bitmap
789 * @relmap: bitmap relative to which translated
790 * @bits: number of bits in each of these bitmaps
791 *
792 * Set the n-th bit of @dst iff there exists some m such that the
793 * n-th bit of @relmap is set, the m-th bit of @orig is set, and
794 * the n-th bit of @relmap is also the m-th _set_ bit of @relmap.
795 * (If you understood the previous sentence the first time your
796 * read it, you're overqualified for your current job.)
797 *
798 * In other words, @orig is mapped onto (surjectively) @dst,
799 * using the the map { <n, m> | the n-th bit of @relmap is the
800 * m-th set bit of @relmap }.
801 *
802 * Any set bits in @orig above bit number W, where W is the
803 * weight of (number of set bits in) @relmap are mapped nowhere.
804 * In particular, if for all bits m set in @orig, m >= W, then
805 * @dst will end up empty. In situations where the possibility
806 * of such an empty result is not desired, one way to avoid it is
807 * to use the bitmap_fold() operator, below, to first fold the
808 * @orig bitmap over itself so that all its set bits x are in the
809 * range 0 <= x < W. The bitmap_fold() operator does this by
810 * setting the bit (m % W) in @dst, for each bit (m) set in @orig.
811 *
812 * Example [1] for bitmap_onto():
813 * Let's say @relmap has bits 30-39 set, and @orig has bits
814 * 1, 3, 5, 7, 9 and 11 set. Then on return from this routine,
815 * @dst will have bits 31, 33, 35, 37 and 39 set.
816 *
817 * When bit 0 is set in @orig, it means turn on the bit in
818 * @dst corresponding to whatever is the first bit (if any)
819 * that is turned on in @relmap. Since bit 0 was off in the
820 * above example, we leave off that bit (bit 30) in @dst.
821 *
822 * When bit 1 is set in @orig (as in the above example), it
823 * means turn on the bit in @dst corresponding to whatever
824 * is the second bit that is turned on in @relmap. The second
825 * bit in @relmap that was turned on in the above example was
826 * bit 31, so we turned on bit 31 in @dst.
827 *
828 * Similarly, we turned on bits 33, 35, 37 and 39 in @dst,
829 * because they were the 4th, 6th, 8th and 10th set bits
830 * set in @relmap, and the 4th, 6th, 8th and 10th bits of
831 * @orig (i.e. bits 3, 5, 7 and 9) were also set.
832 *
833 * When bit 11 is set in @orig, it means turn on the bit in
834 * @dst corresponding to whatever is the twelth bit that is
835 * turned on in @relmap. In the above example, there were
836 * only ten bits turned on in @relmap (30..39), so that bit
837 * 11 was set in @orig had no affect on @dst.
838 *
839 * Example [2] for bitmap_fold() + bitmap_onto():
840 * Let's say @relmap has these ten bits set:
841 * 40 41 42 43 45 48 53 61 74 95
842 * (for the curious, that's 40 plus the first ten terms of the
843 * Fibonacci sequence.)
844 *
845 * Further lets say we use the following code, invoking
846 * bitmap_fold() then bitmap_onto, as suggested above to
847 * avoid the possitility of an empty @dst result:
848 *
849 * unsigned long *tmp; // a temporary bitmap's bits
850 *
851 * bitmap_fold(tmp, orig, bitmap_weight(relmap, bits), bits);
852 * bitmap_onto(dst, tmp, relmap, bits);
853 *
854 * Then this table shows what various values of @dst would be, for
855 * various @orig's. I list the zero-based positions of each set bit.
856 * The tmp column shows the intermediate result, as computed by
857 * using bitmap_fold() to fold the @orig bitmap modulo ten
858 * (the weight of @relmap).
859 *
860 * @orig tmp @dst
861 * 0 0 40
862 * 1 1 41
863 * 9 9 95
864 * 10 0 40 (*)
865 * 1 3 5 7 1 3 5 7 41 43 48 61
866 * 0 1 2 3 4 0 1 2 3 4 40 41 42 43 45
867 * 0 9 18 27 0 9 8 7 40 61 74 95
868 * 0 10 20 30 0 40
869 * 0 11 22 33 0 1 2 3 40 41 42 43
870 * 0 12 24 36 0 2 4 6 40 42 45 53
871 * 78 102 211 1 2 8 41 42 74 (*)
872 *
873 * (*) For these marked lines, if we hadn't first done bitmap_fold()
874 * into tmp, then the @dst result would have been empty.
875 *
876 * If either of @orig or @relmap is empty (no set bits), then @dst
877 * will be returned empty.
878 *
879 * If (as explained above) the only set bits in @orig are in positions
880 * m where m >= W, (where W is the weight of @relmap) then @dst will
881 * once again be returned empty.
882 *
883 * All bits in @dst not set by the above rule are cleared.
884 */
885void bitmap_onto(unsigned long *dst, const unsigned long *orig,
886            const unsigned long *relmap, int bits)
887{
888    int n, m; /* same meaning as in above comment */
889
890    if (dst == orig) /* following doesn't handle inplace mappings */
891        return;
892    bitmap_zero(dst, bits);
893
894    /*
895     * The following code is a more efficient, but less
896     * obvious, equivalent to the loop:
897     * for (m = 0; m < bitmap_weight(relmap, bits); m++) {
898     * n = bitmap_ord_to_pos(orig, m, bits);
899     * if (test_bit(m, orig))
900     * set_bit(n, dst);
901     * }
902     */
903
904    m = 0;
905    for_each_set_bit(n, relmap, bits) {
906        /* m == bitmap_pos_to_ord(relmap, n, bits) */
907        if (test_bit(m, orig))
908            set_bit(n, dst);
909        m++;
910    }
911}
912EXPORT_SYMBOL(bitmap_onto);
913
914/**
915 * bitmap_fold - fold larger bitmap into smaller, modulo specified size
916 * @dst: resulting smaller bitmap
917 * @orig: original larger bitmap
918 * @sz: specified size
919 * @bits: number of bits in each of these bitmaps
920 *
921 * For each bit oldbit in @orig, set bit oldbit mod @sz in @dst.
922 * Clear all other bits in @dst. See further the comment and
923 * Example [2] for bitmap_onto() for why and how to use this.
924 */
925void bitmap_fold(unsigned long *dst, const unsigned long *orig,
926            int sz, int bits)
927{
928    int oldbit;
929
930    if (dst == orig) /* following doesn't handle inplace mappings */
931        return;
932    bitmap_zero(dst, bits);
933
934    for_each_set_bit(oldbit, orig, bits)
935        set_bit(oldbit % sz, dst);
936}
937EXPORT_SYMBOL(bitmap_fold);
938
939/*
940 * Common code for bitmap_*_region() routines.
941 * bitmap: array of unsigned longs corresponding to the bitmap
942 * pos: the beginning of the region
943 * order: region size (log base 2 of number of bits)
944 * reg_op: operation(s) to perform on that region of bitmap
945 *
946 * Can set, verify and/or release a region of bits in a bitmap,
947 * depending on which combination of REG_OP_* flag bits is set.
948 *
949 * A region of a bitmap is a sequence of bits in the bitmap, of
950 * some size '1 << order' (a power of two), aligned to that same
951 * '1 << order' power of two.
952 *
953 * Returns 1 if REG_OP_ISFREE succeeds (region is all zero bits).
954 * Returns 0 in all other cases and reg_ops.
955 */
956
957enum {
958    REG_OP_ISFREE, /* true if region is all zero bits */
959    REG_OP_ALLOC, /* set all bits in region */
960    REG_OP_RELEASE, /* clear all bits in region */
961};
962
963static int __reg_op(unsigned long *bitmap, int pos, int order, int reg_op)
964{
965    int nbits_reg; /* number of bits in region */
966    int index; /* index first long of region in bitmap */
967    int offset; /* bit offset region in bitmap[index] */
968    int nlongs_reg; /* num longs spanned by region in bitmap */
969    int nbitsinlong; /* num bits of region in each spanned long */
970    unsigned long mask; /* bitmask for one long of region */
971    int i; /* scans bitmap by longs */
972    int ret = 0; /* return value */
973
974    /*
975     * Either nlongs_reg == 1 (for small orders that fit in one long)
976     * or (offset == 0 && mask == ~0UL) (for larger multiword orders.)
977     */
978    nbits_reg = 1 << order;
979    index = pos / BITS_PER_LONG;
980    offset = pos - (index * BITS_PER_LONG);
981    nlongs_reg = BITS_TO_LONGS(nbits_reg);
982    nbitsinlong = min(nbits_reg, BITS_PER_LONG);
983
984    /*
985     * Can't do "mask = (1UL << nbitsinlong) - 1", as that
986     * overflows if nbitsinlong == BITS_PER_LONG.
987     */
988    mask = (1UL << (nbitsinlong - 1));
989    mask += mask - 1;
990    mask <<= offset;
991
992    switch (reg_op) {
993    case REG_OP_ISFREE:
994        for (i = 0; i < nlongs_reg; i++) {
995            if (bitmap[index + i] & mask)
996                goto done;
997        }
998        ret = 1; /* all bits in region free (zero) */
999        break;
1000
1001    case REG_OP_ALLOC:
1002        for (i = 0; i < nlongs_reg; i++)
1003            bitmap[index + i] |= mask;
1004        break;
1005
1006    case REG_OP_RELEASE:
1007        for (i = 0; i < nlongs_reg; i++)
1008            bitmap[index + i] &= ~mask;
1009        break;
1010    }
1011done:
1012    return ret;
1013}
1014
1015/**
1016 * bitmap_find_free_region - find a contiguous aligned mem region
1017 * @bitmap: array of unsigned longs corresponding to the bitmap
1018 * @bits: number of bits in the bitmap
1019 * @order: region size (log base 2 of number of bits) to find
1020 *
1021 * Find a region of free (zero) bits in a @bitmap of @bits bits and
1022 * allocate them (set them to one). Only consider regions of length
1023 * a power (@order) of two, aligned to that power of two, which
1024 * makes the search algorithm much faster.
1025 *
1026 * Return the bit offset in bitmap of the allocated region,
1027 * or -errno on failure.
1028 */
1029int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)
1030{
1031    int pos, end; /* scans bitmap by regions of size order */
1032
1033    for (pos = 0 ; (end = pos + (1 << order)) <= bits; pos = end) {
1034        if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
1035            continue;
1036        __reg_op(bitmap, pos, order, REG_OP_ALLOC);
1037        return pos;
1038    }
1039    return -ENOMEM;
1040}
1041EXPORT_SYMBOL(bitmap_find_free_region);
1042
1043/**
1044 * bitmap_release_region - release allocated bitmap region
1045 * @bitmap: array of unsigned longs corresponding to the bitmap
1046 * @pos: beginning of bit region to release
1047 * @order: region size (log base 2 of number of bits) to release
1048 *
1049 * This is the complement to __bitmap_find_free_region() and releases
1050 * the found region (by clearing it in the bitmap).
1051 *
1052 * No return value.
1053 */
1054void bitmap_release_region(unsigned long *bitmap, int pos, int order)
1055{
1056    __reg_op(bitmap, pos, order, REG_OP_RELEASE);
1057}
1058EXPORT_SYMBOL(bitmap_release_region);
1059
1060/**
1061 * bitmap_allocate_region - allocate bitmap region
1062 * @bitmap: array of unsigned longs corresponding to the bitmap
1063 * @pos: beginning of bit region to allocate
1064 * @order: region size (log base 2 of number of bits) to allocate
1065 *
1066 * Allocate (set bits in) a specified region of a bitmap.
1067 *
1068 * Return 0 on success, or %-EBUSY if specified region wasn't
1069 * free (not all bits were zero).
1070 */
1071int bitmap_allocate_region(unsigned long *bitmap, int pos, int order)
1072{
1073    if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
1074        return -EBUSY;
1075    __reg_op(bitmap, pos, order, REG_OP_ALLOC);
1076    return 0;
1077}
1078EXPORT_SYMBOL(bitmap_allocate_region);
1079
1080/**
1081 * bitmap_copy_le - copy a bitmap, putting the bits into little-endian order.
1082 * @dst: destination buffer
1083 * @src: bitmap to copy
1084 * @nbits: number of bits in the bitmap
1085 *
1086 * Require nbits % BITS_PER_LONG == 0.
1087 */
1088void bitmap_copy_le(void *dst, const unsigned long *src, int nbits)
1089{
1090    unsigned long *d = dst;
1091    int i;
1092
1093    for (i = 0; i < nbits/BITS_PER_LONG; i++) {
1094        if (BITS_PER_LONG == 64)
1095            d[i] = cpu_to_le64(src[i]);
1096        else
1097            d[i] = cpu_to_le32(src[i]);
1098    }
1099}
1100EXPORT_SYMBOL(bitmap_copy_le);
1101

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