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Implement bitmap_ffu(), which finds the first unset bit.

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This commit is contained in:
Jason Evans 2017-03-23 17:59:47 -07:00
parent a832ebaee9
commit c8021d01f6
6 changed files with 136 additions and 25 deletions
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27
src/bitmap.c
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@ -39,16 +39,26 @@ bitmap_info_ngroups(const bitmap_info_t *binfo) {
}
void
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo) {
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
size_t extra;
unsigned i;
/*
* Bits are actually inverted with regard to the external bitmap
* interface, so the bitmap starts out with all 1 bits, except for
* trailing unused bits (if any). Note that each group uses bit 0 to
* correspond to the first logical bit in the group, so extra bits
* are the most significant bits of the last group.
* interface.
*/
if (fill) {
/* The "filled" bitmap starts out with all 0 bits. */
memset(bitmap, 0, bitmap_size(binfo));
return;
}
/*
* The "empty" bitmap starts out with all 1 bits, except for trailing
* unused bits (if any). Note that each group uses bit 0 to correspond
* to the first logical bit in the group, so extra bits are the most
* significant bits of the last group.
*/
memset(bitmap, 0xffU, bitmap_size(binfo));
extra = (BITMAP_GROUP_NBITS - (binfo->nbits & BITMAP_GROUP_NBITS_MASK))
@ -84,9 +94,14 @@ bitmap_info_ngroups(const bitmap_info_t *binfo) {
}
void
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo) {
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
size_t extra;
if (fill) {
memset(bitmap, 0, bitmap_size(binfo));
return;
}
memset(bitmap, 0xffU, bitmap_size(binfo));
extra = (BITMAP_GROUP_NBITS - (binfo->nbits & BITMAP_GROUP_NBITS_MASK))
& BITMAP_GROUP_NBITS_MASK;