diff options
Diffstat (limited to 'lib/bitmap.c')
| -rw-r--r-- | lib/bitmap.c | 89 |
1 files changed, 44 insertions, 45 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c index 23d3b11..48e7083 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -519,7 +519,7 @@ EXPORT_SYMBOL(bitmap_parselist); * * 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). + * 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, @@ -531,18 +531,19 @@ EXPORT_SYMBOL(bitmap_parselist); */ static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits) { - int ord = 0; + int i, ord; - if (pos >= 0 && pos < bits) { - int i; + if (pos < 0 || pos >= bits || !test_bit(pos, buf)) + return -1; - for (i = find_first_bit(buf, bits); - i < pos; - i = find_next_bit(buf, bits, i + 1)) - ord++; - if (i > pos) - ord = 0; + 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; } @@ -553,11 +554,12 @@ static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits) * @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). + * 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 valuds will get mapped to 0. When @ord value 3 + * 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. * @@ -583,8 +585,8 @@ static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits) /** * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap - * @src: subset to be remapped * @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 @@ -596,49 +598,42 @@ static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits) * 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. + * 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 the position of - * the first set bit in @new. + * 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. * - * 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. + * 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 s; + int oldbit, w; - 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); + + 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); @@ -657,8 +652,8 @@ EXPORT_SYMBOL(bitmap_remap); * 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. + * 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. @@ -666,14 +661,18 @@ EXPORT_SYMBOL(bitmap_remap); * 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. + * 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 x = bitmap_pos_to_ord(old, oldbit, bits); - return bitmap_ord_to_pos(new, x, 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); |
