*
* 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,
*/
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;
}
* @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.
*
/**
* 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
* 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);
* 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.
* 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);
git.openpandora.org / pandora-kernel.git / blobdiff