/**
* __bitmap_shift_right - logical right shift of the bits in a bitmap
- * @dst - destination bitmap
- * @src - source bitmap
- * @nbits - shift by this many bits
- * @bits - bitmap size, in bits
+ * @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
/**
* __bitmap_shift_left - logical left shift of the bits in a bitmap
- * @dst - destination bitmap
- * @src - source bitmap
- * @nbits - shift by this many bits
- * @bits - bitmap size, in bits
+ * @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
/* 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;
}
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
*/
int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)
{
- int pos; /* scans bitmap by regions of size order */
+ int pos, end; /* 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;
+ for (pos = 0 ; (end = pos + (1 << order)) <= bits; pos = end) {
+ if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
+ continue;
+ __reg_op(bitmap, pos, order, REG_OP_ALLOC);
+ return pos;
+ }
+ return -ENOMEM;
}
EXPORT_SYMBOL(bitmap_find_free_region);
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);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff