Re: [libvirt] [PATCH v4 1/3] bitmap: add virBitmapLastSetBit for finding the last bit position of bitmap

Signed-off-by: Chen Fan <chen.fan.fnst(a)cn.fujitsu.com&gt; --- src/libvirt_private.syms | 1 + src/util/virbitmap.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ src/util/virbitmap.h | 3 +++ tests/virbitmaptest.c | 13 ++++++++++++- 4 files changed, 61 insertions(+), 1 deletion(-) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index d63a8f0..1e2bc0a 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -1011,6 +1011,7 @@ virBitmapFree; virBitmapGetBit; virBitmapIsAllClear; virBitmapIsAllSet; +virBitmapLastSetBit; virBitmapNew; virBitmapNewCopy; virBitmapNewData; diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c index b6bd074..3e7269e 100644 --- a/src/util/virbitmap.c +++ b/src/util/virbitmap.c @@ -651,6 +651,51 @@ virBitmapNextSetBit(virBitmapPtr bitmap, ssize_t pos) } /** + * virBitmapLastSetBit: + * @bitmap: the bitmap + * + * Search for the last set bit in bitmap @bitmap. + * + * Returns the position of the found bit, or -1 if no bit found.

+ */ +ssize_t +virBitmapLastSetBit(virBitmapPtr bitmap) +{ + ssize_t i; + int unusedBits; + ssize_t sz; + unsigned long bits; + + unusedBits = bitmap->map_len * VIR_BITMAP_BITS_PER_UNIT - bitmap->max_bit; + + sz = bitmap->map_len - 1; + if (unusedBits > 0) { + bits = bitmap->map[sz] & (VIR_BITMAP_BIT(VIR_BITMAP_BITS_PER_UNIT - unusedBits) - 1); + if (bits != 0) + goto found; + + sz--; + } + + for (; sz >= 0; sz--) { + bits = bitmap->map[sz]; + if (bits != 0) + goto found; + } + + if (bits == 0) + return -1; + +found: