diff options
Diffstat (limited to 'lib/bitmap.c')
| -rw-r--r-- | lib/bitmap.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c index fb9371fdd44..23d3b1147fe 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -511,6 +511,172 @@ int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits) } 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 zero (0). + * + * 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 ord = 0; + + if (pos >= 0 && pos < bits) { + int i; + + for (i = find_first_bit(buf, bits); + i < pos; + i = find_next_bit(buf, bits, i + 1)) + ord++; + if (i > pos) + ord = 0; + } + 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. + * If @ord is not the ordinal offset of a set bit in @buf, map to zero (0). + * + * 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 valuds will get mapped to 0. 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 + * @src: subset to be remapped + * @dst: remapped result + * @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 does nothing. + * + * The positions of unset bits in @old are mapped to the position of + * the first set bit in @new. + * + * Apply the above specified mapping to @src, placing the result in + * @dst, clearing any bits previously set in @dst. + * + * The resulting value of @dst will have either the same weight as + * @src, or less weight in the general case that the mapping wasn't + * injective due to the weight of @new being less than that of @old. + * The resulting value of @dst will never have greater weight than + * that of @src, except perhaps in the case that one of the above + * conditions was not met and this routine just returned. + * + * 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 to 12 (the first set bit in @new. So if say @src + * comes into this routine with bits 1, 5 and 7 set, then @dst should + * leave with bits 12, 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 s; + + if (bitmap_weight(old, bits) == 0) + return; + if (bitmap_weight(new, bits) == 0) + return; + if (dst == src) /* following doesn't handle inplace remaps */ + return; + + bitmap_zero(dst, bits); + for (s = find_first_bit(src, bits); + s < bits; + s = find_next_bit(src, bits, s + 1)) { + int x = bitmap_pos_to_ord(old, s, bits); + int y = bitmap_ord_to_pos(new, x, bits); + set_bit(y, 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 the position of + * the first set bit in @new. + * + * 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 to 12 (the first set bit in @new. 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 x = bitmap_pos_to_ord(old, oldbit, bits); + return bitmap_ord_to_pos(new, x, bits); +} +EXPORT_SYMBOL(bitmap_bitremap); + /** * bitmap_find_free_region - find a contiguous aligned mem region * @bitmap: an array of unsigned longs corresponding to the bitmap |