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Diffstat (limited to 'lib/bitmap.c')
| -rw-r--r-- | lib/bitmap.c | 1020 |
1 files changed, 1020 insertions, 0 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c new file mode 100644 index 0000000..1338469 --- /dev/null +++ b/lib/bitmap.c @@ -0,0 +1,1020 @@ +/* + * lib/bitmap.c + * Helper functions for bitmap.h. + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. + */ +#include <linux/module.h> +#include <linux/ctype.h> +#include <linux/errno.h> +#include <linux/bitmap.h> +#include <linux/bitops.h> +#include <asm/uaccess.h> + +/* + * bitmaps provide an array of bits, implemented using an an + * array of unsigned longs. The number of valid bits in a + * given bitmap does _not_ need to be an exact multiple of + * BITS_PER_LONG. + * + * The possible unused bits in the last, partially used word + * of a bitmap are 'don't care'. The implementation makes + * no particular effort to keep them zero. It ensures that + * their value will not affect the results of any operation. + * The bitmap operations that return Boolean (bitmap_empty, + * for example) or scalar (bitmap_weight, for example) results + * carefully filter out these unused bits from impacting their + * results. + * + * These operations actually hold to a slightly stronger rule: + * if you don't input any bitmaps to these ops that have some + * unused bits set, then they won't output any set unused bits + * in output bitmaps. + * + * The byte ordering of bitmaps is more natural on little + * endian architectures. See the big-endian headers + * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h + * for the best explanations of this ordering. + */ + +int __bitmap_empty(const unsigned long *bitmap, int bits) +{ + int k, lim = bits/BITS_PER_LONG; + for (k = 0; k < lim; ++k) + if (bitmap[k]) + return 0; + + if (bits % BITS_PER_LONG) + if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits)) + return 0; + + return 1; +} +EXPORT_SYMBOL(__bitmap_empty); + +int __bitmap_full(const unsigned long *bitmap, int bits) +{ + int k, lim = bits/BITS_PER_LONG; + for (k = 0; k < lim; ++k) + if (~bitmap[k]) + return 0; + + if (bits % BITS_PER_LONG) + if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits)) + return 0; + + return 1; +} +EXPORT_SYMBOL(__bitmap_full); + +int __bitmap_equal(const unsigned long *bitmap1, + const unsigned long *bitmap2, int bits) +{ + int k, lim = bits/BITS_PER_LONG; + for (k = 0; k < lim; ++k) + if (bitmap1[k] != bitmap2[k]) + return 0; + + if (bits % BITS_PER_LONG) + if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits)) + return 0; + + return 1; +} +EXPORT_SYMBOL(__bitmap_equal); + +void __bitmap_complement(unsigned long *dst, const unsigned long *src, int bits) +{ + int k, lim = bits/BITS_PER_LONG; + for (k = 0; k < lim; ++k) + dst[k] = ~src[k]; + + if (bits % BITS_PER_LONG) + dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits); +} +EXPORT_SYMBOL(__bitmap_complement); + +/** + * __bitmap_shift_right - logical right shift of the bits in a bitmap + * @dst : destination bitmap + * @src : source bitmap + * @shift : shift by this many bits + * @bits : bitmap size, in bits + * + * Shifting right (dividing) means moving bits in the MS -> LS bit + * direction. Zeros are fed into the vacated MS positions and the + * LS bits shifted off the bottom are lost. + */ +void __bitmap_shift_right(unsigned long *dst, + const unsigned long *src, int shift, int bits) +{ + int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG; + int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG; + unsigned long mask = (1UL << left) - 1; + for (k = 0; off + k < lim; ++k) { + unsigned long upper, lower; + + /* + * If shift is not word aligned, take lower rem bits of + * word above and make them the top rem bits of result. + */ + if (!rem || off + k + 1 >= lim) + upper = 0; + else { + upper = src[off + k + 1]; + if (off + k + 1 == lim - 1 && left) + upper &= mask; + } + lower = src[off + k]; + if (left && off + k == lim - 1) + lower &= mask; + dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem; + if (left && k == lim - 1) + dst[k] &= mask; + } + if (off) + memset(&dst[lim - off], 0, off*sizeof(unsigned long)); +} +EXPORT_SYMBOL(__bitmap_shift_right); + + +/** + * __bitmap_shift_left - logical left shift of the bits in a bitmap + * @dst : destination bitmap + * @src : source bitmap + * @shift : shift by this many bits + * @bits : bitmap size, in bits + * + * Shifting left (multiplying) means moving bits in the LS -> MS + * direction. Zeros are fed into the vacated LS bit positions + * and those MS bits shifted off the top are lost. + */ + +void __bitmap_shift_left(unsigned long *dst, + const unsigned long *src, int shift, int bits) +{ + int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG; + int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG; + for (k = lim - off - 1; k >= 0; --k) { + unsigned long upper, lower; + + /* + * If shift is not word aligned, take upper rem bits of + * word below and make them the bottom rem bits of result. + */ + if (rem && k > 0) + lower = src[k - 1]; + else + lower = 0; + upper = src[k]; + if (left && k == lim - 1) + upper &= (1UL << left) - 1; + dst[k + off] = lower >> (BITS_PER_LONG - rem) | upper << rem; + if (left && k + off == lim - 1) + dst[k + off] &= (1UL << left) - 1; + } + if (off) + memset(dst, 0, off*sizeof(unsigned long)); +} +EXPORT_SYMBOL(__bitmap_shift_left); + +void __bitmap_and(unsigned long *dst, const unsigned long *bitmap1, + const unsigned long *bitmap2, int bits) +{ + int k; + int nr = BITS_TO_LONGS(bits); + + for (k = 0; k < nr; k++) + dst[k] = bitmap1[k] & bitmap2[k]; +} +EXPORT_SYMBOL(__bitmap_and); + +void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1, + const unsigned long *bitmap2, int bits) +{ + int k; + int nr = BITS_TO_LONGS(bits); + + for (k = 0; k < nr; k++) + dst[k] = bitmap1[k] | bitmap2[k]; +} +EXPORT_SYMBOL(__bitmap_or); + +void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1, + const unsigned long *bitmap2, int bits) +{ + int k; + int nr = BITS_TO_LONGS(bits); + + for (k = 0; k < nr; k++) + dst[k] = bitmap1[k] ^ bitmap2[k]; +} +EXPORT_SYMBOL(__bitmap_xor); + +void __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1, + const unsigned long *bitmap2, int bits) +{ + int k; + int nr = BITS_TO_LONGS(bits); + + for (k = 0; k < nr; k++) + dst[k] = bitmap1[k] & ~bitmap2[k]; +} +EXPORT_SYMBOL(__bitmap_andnot); + +int __bitmap_intersects(const unsigned long *bitmap1, + const unsigned long *bitmap2, int bits) +{ + int k, lim = bits/BITS_PER_LONG; + for (k = 0; k < lim; ++k) + if (bitmap1[k] & bitmap2[k]) + return 1; + + if (bits % BITS_PER_LONG) + if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits)) + return 1; + return 0; +} +EXPORT_SYMBOL(__bitmap_intersects); + +int __bitmap_subset(const unsigned long *bitmap1, + const unsigned long *bitmap2, int bits) +{ + int k, lim = bits/BITS_PER_LONG; + for (k = 0; k < lim; ++k) + if (bitmap1[k] & ~bitmap2[k]) + return 0; + + if (bits % BITS_PER_LONG) + if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits)) + return 0; + return 1; +} +EXPORT_SYMBOL(__bitmap_subset); + +int __bitmap_weight(const unsigned long *bitmap, int bits) +{ + int k, w = 0, lim = bits/BITS_PER_LONG; + + for (k = 0; k < lim; k++) + w += hweight_long(bitmap[k]); + + if (bits % BITS_PER_LONG) + w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits)); + + return w; +} +EXPORT_SYMBOL(__bitmap_weight); + +/* + * Bitmap printing & parsing functions: first version by Bill Irwin, + * second version by Paul Jackson, third by Joe Korty. + */ + +#define CHUNKSZ 32 +#define nbits_to_hold_value(val) fls(val) +#define unhex(c) (isdigit(c) ? (c - '0') : (toupper(c) - 'A' + 10)) +#define BASEDEC 10 /* fancier cpuset lists input in decimal */ + +/** + * bitmap_scnprintf - convert bitmap to an ASCII hex string. + * @buf: byte buffer into which string is placed + * @buflen: reserved size of @buf, in bytes + * @maskp: pointer to bitmap to convert + * @nmaskbits: size of bitmap, in bits + * + * Exactly @nmaskbits bits are displayed. Hex digits are grouped into + * comma-separated sets of eight digits per set. + */ +int bitmap_scnprintf(char *buf, unsigned int buflen, + const unsigned long *maskp, int nmaskbits) +{ + int i, word, bit, len = 0; + unsigned long val; + const char *sep = ""; + int chunksz; + u32 chunkmask; + + chunksz = nmaskbits & (CHUNKSZ - 1); + if (chunksz == 0) + chunksz = CHUNKSZ; + + i = ALIGN(nmaskbits, CHUNKSZ) - CHUNKSZ; + for (; i >= 0; i -= CHUNKSZ) { + chunkmask = ((1ULL << chunksz) - 1); + word = i / BITS_PER_LONG; + bit = i % BITS_PER_LONG; + val = (maskp[word] >> bit) & chunkmask; + len += scnprintf(buf+len, buflen-len, "%s%0*lx", sep, + (chunksz+3)/4, val); + chunksz = CHUNKSZ; + sep = ","; + } + return len; +} +EXPORT_SYMBOL(bitmap_scnprintf); + +/** + * __bitmap_parse - convert an ASCII hex string into a bitmap. + * @buf: pointer to buffer containing string. + * @buflen: buffer size in bytes. If string is smaller than this + * then it must be terminated with a \0. + * @is_user: location of buffer, 0 indicates kernel space + * @maskp: pointer to bitmap array that will contain result. + * @nmaskbits: size of bitmap, in bits. + * + * Commas group hex digits into chunks. Each chunk defines exactly 32 + * bits of the resultant bitmask. No chunk may specify a value larger + * than 32 bits (%-EOVERFLOW), and if a chunk specifies a smaller value + * then leading 0-bits are prepended. %-EINVAL is returned for illegal + * characters and for grouping errors such as "1,,5", ",44", "," and "". + * Leading and trailing whitespace accepted, but not embedded whitespace. + */ +int __bitmap_parse(const char *buf, unsigned int buflen, + int is_user, unsigned long *maskp, + int nmaskbits) +{ + int c, old_c, totaldigits, ndigits, nchunks, nbits; + u32 chunk; + const char __user *ubuf = buf; + + bitmap_zero(maskp, nmaskbits); + + nchunks = nbits = totaldigits = c = 0; + do { + chunk = ndigits = 0; + + /* Get the next chunk of the bitmap */ + while (buflen) { + old_c = c; + if (is_user) { + if (__get_user(c, ubuf++)) + return -EFAULT; + } + else + c = *buf++; + buflen--; + if (isspace(c)) + continue; + + /* + * If the last character was a space and the current + * character isn't '\0', we've got embedded whitespace. + * This is a no-no, so throw an error. + */ + if (totaldigits && c && isspace(old_c)) + return -EINVAL; + + /* A '\0' or a ',' signal the end of the chunk */ + if (c == '\0' || c == ',') + break; + + if (!isxdigit(c)) + return -EINVAL; + + /* + * Make sure there are at least 4 free bits in 'chunk'. + * If not, this hexdigit will overflow 'chunk', so + * throw an error. + */ + if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1)) + return -EOVERFLOW; + + chunk = (chunk << 4) | unhex(c); + ndigits++; totaldigits++; + } + if (ndigits == 0) + return -EINVAL; + if (nchunks == 0 && chunk == 0) + continue; + + __bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits); + *maskp |= chunk; + nchunks++; + nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ; + if (nbits > nmaskbits) + return -EOVERFLOW; + } while (buflen && c == ','); + + return 0; +} +EXPORT_SYMBOL(__bitmap_parse); + +/** + * bitmap_parse_user() + * + * @ubuf: pointer to user buffer containing string. + * @ulen: buffer size in bytes. If string is smaller than this + * then it must be terminated with a \0. + * @maskp: pointer to bitmap array that will contain result. + * @nmaskbits: size of bitmap, in bits. + * + * Wrapper for __bitmap_parse(), providing it with user buffer. + * + * We cannot have this as an inline function in bitmap.h because it needs + * linux/uaccess.h to get the access_ok() declaration and this causes + * cyclic dependencies. + */ +int bitmap_parse_user(const char __user *ubuf, + unsigned int ulen, unsigned long *maskp, + int nmaskbits) +{ + if (!access_ok(VERIFY_READ, ubuf, ulen)) + return -EFAULT; + return __bitmap_parse((const char *)ubuf, ulen, 1, maskp, nmaskbits); +} +EXPORT_SYMBOL(bitmap_parse_user); + +/* + * bscnl_emit(buf, buflen, rbot, rtop, bp) + * + * Helper routine for bitmap_scnlistprintf(). Write decimal number + * or range to buf, suppressing output past buf+buflen, with optional + * comma-prefix. Return len of what would be written to buf, if it + * all fit. + */ +static inline int bscnl_emit(char *buf, int buflen, int rbot, int rtop, int len) +{ + if (len > 0) + len += scnprintf(buf + len, buflen - len, ","); + if (rbot == rtop) + len += scnprintf(buf + len, buflen - len, "%d", rbot); + else + len += scnprintf(buf + len, buflen - len, "%d-%d", rbot, rtop); + return len; +} + +/** + * bitmap_scnlistprintf - convert bitmap to list format ASCII string + * @buf: byte buffer into which string is placed + * @buflen: reserved size of @buf, in bytes + * @maskp: pointer to bitmap to convert + * @nmaskbits: size of bitmap, in bits + * + * Output format is a comma-separated list of decimal numbers and + * ranges. Consecutively set bits are shown as two hyphen-separated + * decimal numbers, the smallest and largest bit numbers set in + * the range. Output format is compatible with the format + * accepted as input by bitmap_parselist(). + * + * The return value is the number of characters which would be + * generated for the given input, excluding the trailing '\0', as + * per ISO C99. + */ +int bitmap_scnlistprintf(char *buf, unsigned int buflen, + const unsigned long *maskp, int nmaskbits) +{ + int len = 0; + /* current bit is 'cur', most recently seen range is [rbot, rtop] */ + int cur, rbot, rtop; + + if (buflen == 0) + return 0; + buf[0] = 0; + + rbot = cur = find_first_bit(maskp, nmaskbits); + while (cur < nmaskbits) { + rtop = cur; + cur = find_next_bit(maskp, nmaskbits, cur+1); + if (cur >= nmaskbits || cur > rtop + 1) { + len = bscnl_emit(buf, buflen, rbot, rtop, len); + rbot = cur; + } + } + return len; +} +EXPORT_SYMBOL(bitmap_scnlistprintf); + +/** + * bitmap_parselist - convert list format ASCII string to bitmap + * @bp: read nul-terminated user string from this buffer + * @maskp: write resulting mask here + * @nmaskbits: number of bits in mask to be written + * + * Input format is a comma-separated list of decimal numbers and + * ranges. Consecutively set bits are shown as two hyphen-separated + * decimal numbers, the smallest and largest bit numbers set in + * the range. + * + * Returns 0 on success, -errno on invalid input strings. + * Error values: + * %-EINVAL: second number in range smaller than first + * %-EINVAL: invalid character in string + * %-ERANGE: bit number specified too large for mask + */ +int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits) +{ + unsigned a, b; + + bitmap_zero(maskp, nmaskbits); + do { + if (!isdigit(*bp)) + return -EINVAL; + b = a = simple_strtoul(bp, (char **)&bp, BASEDEC); + if (*bp == '-') { + bp++; + if (!isdigit(*bp)) + return -EINVAL; + b = simple_strtoul(bp, (char **)&bp, BASEDEC); + } + if (!(a <= b)) + return -EINVAL; + if (b >= nmaskbits) + return -ERANGE; + while (a <= b) { + set_bit(a, maskp); + a++; + } + if (*bp == ',') + bp++; + } while (*bp != '\0' && *bp != '\n'); + return 0; +} +EXPORT_SYMBOL(bitmap_parselist); + +/** + * bitmap_pos_to_ord(buf, pos, bits) + * @buf: pointer to a bitmap + * @pos: a bit position in @buf (0 <= @pos < @bits) + * @bits: number of valid bit positions in @buf + * + * Map the bit at position @pos in @buf (of length @bits) to the + * ordinal of which set bit it is. If it is not set or if @pos + * is not a valid bit position, map to -1. + * + * If for example, just bits 4 through 7 are set in @buf, then @pos + * values 4 through 7 will get mapped to 0 through 3, respectively, + * and other @pos values will get mapped to 0. When @pos value 7 + * gets mapped to (returns) @ord value 3 in this example, that means + * that bit 7 is the 3rd (starting with 0th) set bit in @buf. + * + * The bit positions 0 through @bits are valid positions in @buf. + */ +static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits) +{ + int i, ord; + + if (pos < 0 || pos >= bits || !test_bit(pos, buf)) + return -1; + + i = find_first_bit(buf, bits); + ord = 0; + while (i < pos) { + i = find_next_bit(buf, bits, i + 1); + ord++; + } + BUG_ON(i != pos); + + return ord; +} + +/** + * bitmap_ord_to_pos(buf, ord, bits) + * @buf: pointer to bitmap + * @ord: ordinal bit position (n-th set bit, n >= 0) + * @bits: number of valid bit positions in @buf + * + * Map the ordinal offset of bit @ord in @buf to its position in @buf. + * Value of @ord should be in range 0 <= @ord < weight(buf), else + * results are undefined. + * + * If for example, just bits 4 through 7 are set in @buf, then @ord + * values 0 through 3 will get mapped to 4 through 7, respectively, + * and all other @ord values return undefined values. When @ord value 3 + * gets mapped to (returns) @pos value 7 in this example, that means + * that the 3rd set bit (starting with 0th) is at position 7 in @buf. + * + * The bit positions 0 through @bits are valid positions in @buf. + */ +static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits) +{ + int pos = 0; + + if (ord >= 0 && ord < bits) { + int i; + + for (i = find_first_bit(buf, bits); + i < bits && ord > 0; + i = find_next_bit(buf, bits, i + 1)) + ord--; + if (i < bits && ord == 0) + pos = i; + } + + return pos; +} + +/** + * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap + * @dst: remapped result + * @src: subset to be remapped + * @old: defines domain of map + * @new: defines range of map + * @bits: number of bits in each of these bitmaps + * + * Let @old and @new define a mapping of bit positions, such that + * whatever position is held by the n-th set bit in @old is mapped + * to the n-th set bit in @new. In the more general case, allowing + * for the possibility that the weight 'w' of @new is less than the + * weight of @old, map the position of the n-th set bit in @old to + * the position of the m-th set bit in @new, where m == n % w. + * + * If either of the @old and @new bitmaps are empty, or if @src and + * @dst point to the same location, then this routine copies @src + * to @dst. + * + * The positions of unset bits in @old are mapped to themselves + * (the identify map). + * + * Apply the above specified mapping to @src, placing the result in + * @dst, clearing any bits previously set in @dst. + * + * For example, lets say that @old has bits 4 through 7 set, and + * @new has bits 12 through 15 set. This defines the mapping of bit + * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other + * bit positions unchanged. So if say @src comes into this routine + * with bits 1, 5 and 7 set, then @dst should leave with bits 1, + * 13 and 15 set. + */ +void bitmap_remap(unsigned long *dst, const unsigned long *src, + const unsigned long *old, const unsigned long *new, + int bits) +{ + int oldbit, w; + + if (dst == src) /* following doesn't handle inplace remaps */ + return; + bitmap_zero(dst, bits); + + w = bitmap_weight(new, bits); + for (oldbit = find_first_bit(src, bits); + oldbit < bits; + oldbit = find_next_bit(src, bits, oldbit + 1)) { + int n = bitmap_pos_to_ord(old, oldbit, bits); + if (n < 0 || w == 0) + set_bit(oldbit, dst); /* identity map */ + else + set_bit(bitmap_ord_to_pos(new, n % w, bits), dst); + } +} +EXPORT_SYMBOL(bitmap_remap); + +/** + * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit + * @oldbit: bit position to be mapped + * @old: defines domain of map + * @new: defines range of map + * @bits: number of bits in each of these bitmaps + * + * Let @old and @new define a mapping of bit positions, such that + * whatever position is held by the n-th set bit in @old is mapped + * to the n-th set bit in @new. In the more general case, allowing + * for the possibility that the weight 'w' of @new is less than the + * weight of @old, map the position of the n-th set bit in @old to + * the position of the m-th set bit in @new, where m == n % w. + * + * The positions of unset bits in @old are mapped to themselves + * (the identify map). + * + * Apply the above specified mapping to bit position @oldbit, returning + * the new bit position. + * + * For example, lets say that @old has bits 4 through 7 set, and + * @new has bits 12 through 15 set. This defines the mapping of bit + * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other + * bit positions unchanged. So if say @oldbit is 5, then this routine + * returns 13. + */ +int bitmap_bitremap(int oldbit, const unsigned long *old, + const unsigned long *new, int bits) +{ + int w = bitmap_weight(new, bits); + int n = bitmap_pos_to_ord(old, oldbit, bits); + if (n < 0 || w == 0) + return oldbit; + else + return bitmap_ord_to_pos(new, n % w, bits); +} +EXPORT_SYMBOL(bitmap_bitremap); + +/** + * bitmap_onto - translate one bitmap relative to another + * @dst: resulting translated bitmap + * @orig: original untranslated bitmap + * @relmap: bitmap relative to which translated + * @bits: number of bits in each of these bitmaps + * + * Set the n-th bit of @dst iff there exists some m such that the + * n-th bit of @relmap is set, the m-th bit of @orig is set, and + * the n-th bit of @relmap is also the m-th _set_ bit of @relmap. + * (If you understood the previous sentence the first time your + * read it, you're overqualified for your current job.) + * + * In other words, @orig is mapped onto (surjectively) @dst, + * using the the map { <n, m> | the n-th bit of @relmap is the + * m-th set bit of @relmap }. + * + * Any set bits in @orig above bit number W, where W is the + * weight of (number of set bits in) @relmap are mapped nowhere. + * In particular, if for all bits m set in @orig, m >= W, then + * @dst will end up empty. In situations where the possibility + * of such an empty result is not desired, one way to avoid it is + * to use the bitmap_fold() operator, below, to first fold the + * @orig bitmap over itself so that all its set bits x are in the + * range 0 <= x < W. The bitmap_fold() operator does this by + * setting the bit (m % W) in @dst, for each bit (m) set in @orig. + * + * Example [1] for bitmap_onto(): + * Let's say @relmap has bits 30-39 set, and @orig has bits + * 1, 3, 5, 7, 9 and 11 set. Then on return from this routine, + * @dst will have bits 31, 33, 35, 37 and 39 set. + * + * When bit 0 is set in @orig, it means turn on the bit in + * @dst corresponding to whatever is the first bit (if any) + * that is turned on in @relmap. Since bit 0 was off in the + * above example, we leave off that bit (bit 30) in @dst. + * + * When bit 1 is set in @orig (as in the above example), it + * means turn on the bit in @dst corresponding to whatever + * is the second bit that is turned on in @relmap. The second + * bit in @relmap that was turned on in the above example was + * bit 31, so we turned on bit 31 in @dst. + * + * Similarly, we turned on bits 33, 35, 37 and 39 in @dst, + * because they were the 4th, 6th, 8th and 10th set bits + * set in @relmap, and the 4th, 6th, 8th and 10th bits of + * @orig (i.e. bits 3, 5, 7 and 9) were also set. + * + * When bit 11 is set in @orig, it means turn on the bit in + * @dst corresponding to whatever is the twelth bit that is + * turned on in @relmap. In the above example, there were + * only ten bits turned on in @relmap (30..39), so that bit + * 11 was set in @orig had no affect on @dst. + * + * Example [2] for bitmap_fold() + bitmap_onto(): + * Let's say @relmap has these ten bits set: + * 40 41 42 43 45 48 53 61 74 95 + * (for the curious, that's 40 plus the first ten terms of the + * Fibonacci sequence.) + * + * Further lets say we use the following code, invoking + * bitmap_fold() then bitmap_onto, as suggested above to + * avoid the possitility of an empty @dst result: + * + * unsigned long *tmp; // a temporary bitmap's bits + * + * bitmap_fold(tmp, orig, bitmap_weight(relmap, bits), bits); + * bitmap_onto(dst, tmp, relmap, bits); + * + * Then this table shows what various values of @dst would be, for + * various @orig's. I list the zero-based positions of each set bit. + * The tmp column shows the intermediate result, as computed by + * using bitmap_fold() to fold the @orig bitmap modulo ten + * (the weight of @relmap). + * + * @orig tmp @dst + * 0 0 40 + * 1 1 41 + * 9 9 95 + * 10 0 40 (*) + * 1 3 5 7 1 3 5 7 41 43 48 61 + * 0 1 2 3 4 0 1 2 3 4 40 41 42 43 45 + * 0 9 18 27 0 9 8 7 40 61 74 95 + * 0 10 20 30 0 40 + * 0 11 22 33 0 1 2 3 40 41 42 43 + * 0 12 24 36 0 2 4 6 40 42 45 53 + * 78 102 211 1 2 8 41 42 74 (*) + * + * (*) For these marked lines, if we hadn't first done bitmap_fold() + * into tmp, then the @dst result would have been empty. + * + * If either of @orig or @relmap is empty (no set bits), then @dst + * will be returned empty. + * + * If (as explained above) the only set bits in @orig are in positions + * m where m >= W, (where W is the weight of @relmap) then @dst will + * once again be returned empty. + * + * All bits in @dst not set by the above rule are cleared. + */ +void bitmap_onto(unsigned long *dst, const unsigned long *orig, + const unsigned long *relmap, int bits) +{ + int n, m; /* same meaning as in above comment */ + + if (dst == orig) /* following doesn't handle inplace mappings */ + return; + bitmap_zero(dst, bits); + + /* + * The following code is a more efficient, but less + * obvious, equivalent to the loop: + * for (m = 0; m < bitmap_weight(relmap, bits); m++) { + * n = bitmap_ord_to_pos(orig, m, bits); + * if (test_bit(m, orig)) + * set_bit(n, dst); + * } + */ + + m = 0; + for (n = find_first_bit(relmap, bits); + n < bits; + n = find_next_bit(relmap, bits, n + 1)) { + /* m == bitmap_pos_to_ord(relmap, n, bits) */ + if (test_bit(m, orig)) + set_bit(n, dst); + m++; + } +} +EXPORT_SYMBOL(bitmap_onto); + +/** + * bitmap_fold - fold larger bitmap into smaller, modulo specified size + * @dst: resulting smaller bitmap + * @orig: original larger bitmap + * @sz: specified size + * @bits: number of bits in each of these bitmaps + * + * For each bit oldbit in @orig, set bit oldbit mod @sz in @dst. + * Clear all other bits in @dst. See further the comment and + * Example [2] for bitmap_onto() for why and how to use this. + */ +void bitmap_fold(unsigned long *dst, const unsigned long *orig, + int sz, int bits) +{ + int oldbit; + + if (dst == orig) /* following doesn't handle inplace mappings */ + return; + bitmap_zero(dst, bits); + + for (oldbit = find_first_bit(orig, bits); + oldbit < bits; + oldbit = find_next_bit(orig, bits, oldbit + 1)) + set_bit(oldbit % sz, dst); +} +EXPORT_SYMBOL(bitmap_fold); + +/* + * Common code for bitmap_*_region() routines. + * bitmap: array of unsigned longs corresponding to the bitmap + * pos: the beginning of the region + * order: region size (log base 2 of number of bits) + * reg_op: operation(s) to perform on that region of bitmap + * + * Can set, verify and/or release a region of bits in a bitmap, + * depending on which combination of REG_OP_* flag bits is set. + * + * A region of a bitmap is a sequence of bits in the bitmap, of + * some size '1 << order' (a power of two), aligned to that same + * '1 << order' power of two. + * + * Returns 1 if REG_OP_ISFREE succeeds (region is all zero bits). + * Returns 0 in all other cases and reg_ops. + */ + +enum { + REG_OP_ISFREE, /* true if region is all zero bits */ + REG_OP_ALLOC, /* set all bits in region */ + REG_OP_RELEASE, /* clear all bits in region */ +}; + +static int __reg_op(unsigned long *bitmap, int pos, int order, int reg_op) +{ + int nbits_reg; /* number of bits in region */ + int index; /* index first long of region in bitmap */ + int offset; /* bit offset region in bitmap[index] */ + int nlongs_reg; /* num longs spanned by region in bitmap */ + int nbitsinlong; /* num bits of region in each spanned long */ + unsigned long mask; /* bitmask for one long of region */ + int i; /* scans bitmap by longs */ + int ret = 0; /* return value */ + + /* + * Either nlongs_reg == 1 (for small orders that fit in one long) + * or (offset == 0 && mask == ~0UL) (for larger multiword orders.) + */ + nbits_reg = 1 << order; + index = pos / BITS_PER_LONG; + offset = pos - (index * BITS_PER_LONG); + nlongs_reg = BITS_TO_LONGS(nbits_reg); + nbitsinlong = min(nbits_reg, BITS_PER_LONG); + + /* + * Can't do "mask = (1UL << nbitsinlong) - 1", as that + * overflows if nbitsinlong == BITS_PER_LONG. + */ + mask = (1UL << (nbitsinlong - 1)); + mask += mask - 1; + mask <<= offset; + + switch (reg_op) { + case REG_OP_ISFREE: + for (i = 0; i < nlongs_reg; i++) { + if (bitmap[index + i] & mask) + goto done; + } + ret = 1; /* all bits in region free (zero) */ + break; + + case REG_OP_ALLOC: + for (i = 0; i < nlongs_reg; i++) + bitmap[index + i] |= mask; + break; + + case REG_OP_RELEASE: + for (i = 0; i < nlongs_reg; i++) + bitmap[index + i] &= ~mask; + break; + } +done: + return ret; +} + +/** + * bitmap_find_free_region - find a contiguous aligned mem region + * @bitmap: array of unsigned longs corresponding to the bitmap + * @bits: number of bits in the bitmap + * @order: region size (log base 2 of number of bits) to find + * + * Find a region of free (zero) bits in a @bitmap of @bits bits and + * allocate them (set them to one). Only consider regions of length + * a power (@order) of two, aligned to that power of two, which + * makes the search algorithm much faster. + * + * Return the bit offset in bitmap of the allocated region, + * or -errno on failure. + */ +int bitmap_find_free_region(unsigned long *bitmap, int bits, int order) +{ + int pos; /* scans bitmap by regions of size order */ + + for (pos = 0; pos < bits; pos += (1 << order)) + if (__reg_op(bitmap, pos, order, REG_OP_ISFREE)) + break; + if (pos == bits) + return -ENOMEM; + __reg_op(bitmap, pos, order, REG_OP_ALLOC); + return pos; +} +EXPORT_SYMBOL(bitmap_find_free_region); + +/** + * bitmap_release_region - release allocated bitmap region + * @bitmap: array of unsigned longs corresponding to the bitmap + * @pos: beginning of bit region to release + * @order: region size (log base 2 of number of bits) to release + * + * This is the complement to __bitmap_find_free_region() and releases + * the found region (by clearing it in the bitmap). + * + * No return value. + */ +void bitmap_release_region(unsigned long *bitmap, int pos, int order) +{ + __reg_op(bitmap, pos, order, REG_OP_RELEASE); +} +EXPORT_SYMBOL(bitmap_release_region); + +/** + * bitmap_allocate_region - allocate bitmap region + * @bitmap: array of unsigned longs corresponding to the bitmap + * @pos: beginning of bit region to allocate + * @order: region size (log base 2 of number of bits) to allocate + * + * Allocate (set bits in) a specified region of a bitmap. + * + * Return 0 on success, or %-EBUSY if specified region wasn't + * free (not all bits were zero). + */ +int bitmap_allocate_region(unsigned long *bitmap, int pos, int order) +{ + if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE)) + return -EBUSY; + __reg_op(bitmap, pos, order, REG_OP_ALLOC); + return 0; +} +EXPORT_SYMBOL(bitmap_allocate_region); + +/** + * bitmap_copy_le - copy a bitmap, putting the bits into little-endian order. + * @dst: destination buffer + * @src: bitmap to copy + * @nbits: number of bits in the bitmap + * + * Require nbits % BITS_PER_LONG == 0. + */ +void bitmap_copy_le(void *dst, const unsigned long *src, int nbits) +{ + unsigned long *d = dst; + int i; + + for (i = 0; i < nbits/BITS_PER_LONG; i++) { + if (BITS_PER_LONG == 64) + d[i] = cpu_to_le64(src[i]); + else + d[i] = cpu_to_le32(src[i]); + } +} +EXPORT_SYMBOL(bitmap_copy_le); |
