From ad37f24d57a81020ceba4c966563b1ad7c7199e3 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Mon, 3 Jun 2019 14:50:49 +0800 Subject: bitmap: Add bitmap_copy_with_{src|dst}_offset() These helpers copy the source bitmap to destination bitmap with a shift either on the src or dst bitmap. Meanwhile, we never have bitmap tests but we should. This patch also introduces the initial test cases for utils/bitmap.c but it only tests the newly introduced functions. Signed-off-by: Peter Xu Reviewed-by: Juan Quintela Message-Id: <20190603065056.25211-5-peterx@redhat.com> Signed-off-by: Juan Quintela --- Bitmap test used sizeof(unsigned long) instead of BITS_PER_LONG. --- util/bitmap.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) (limited to 'util/bitmap.c') diff --git a/util/bitmap.c b/util/bitmap.c index cb618c65a5..1753ff7f5b 100644 --- a/util/bitmap.c +++ b/util/bitmap.c @@ -402,3 +402,88 @@ void bitmap_to_le(unsigned long *dst, const unsigned long *src, { bitmap_to_from_le(dst, src, nbits); } + +/* + * Copy "src" bitmap with a positive offset and put it into the "dst" + * bitmap. The caller needs to make sure the bitmap size of "src" + * is bigger than (shift + nbits). + */ +void bitmap_copy_with_src_offset(unsigned long *dst, const unsigned long *src, + unsigned long shift, unsigned long nbits) +{ + unsigned long left_mask, right_mask, last_mask; + + /* Proper shift src pointer to the first word to copy from */ + src += BIT_WORD(shift); + shift %= BITS_PER_LONG; + + if (!shift) { + /* Fast path */ + bitmap_copy(dst, src, nbits); + return; + } + + right_mask = (1ul << shift) - 1; + left_mask = ~right_mask; + + while (nbits >= BITS_PER_LONG) { + *dst = (*src & left_mask) >> shift; + *dst |= (src[1] & right_mask) << (BITS_PER_LONG - shift); + dst++; + src++; + nbits -= BITS_PER_LONG; + } + + if (nbits > BITS_PER_LONG - shift) { + *dst = (*src & left_mask) >> shift; + nbits -= BITS_PER_LONG - shift; + last_mask = (1ul << nbits) - 1; + *dst |= (src[1] & last_mask) << (BITS_PER_LONG - shift); + } else if (nbits) { + last_mask = (1ul << nbits) - 1; + *dst = (*src >> shift) & last_mask; + } +} + +/* + * Copy "src" bitmap into the "dst" bitmap with an offset in the + * "dst". The caller needs to make sure the bitmap size of "dst" is + * bigger than (shift + nbits). + */ +void bitmap_copy_with_dst_offset(unsigned long *dst, const unsigned long *src, + unsigned long shift, unsigned long nbits) +{ + unsigned long left_mask, right_mask, last_mask; + + /* Proper shift dst pointer to the first word to copy from */ + dst += BIT_WORD(shift); + shift %= BITS_PER_LONG; + + if (!shift) { + /* Fast path */ + bitmap_copy(dst, src, nbits); + return; + } + + right_mask = (1ul << (BITS_PER_LONG - shift)) - 1; + left_mask = ~right_mask; + + *dst &= (1ul << shift) - 1; + while (nbits >= BITS_PER_LONG) { + *dst |= (*src & right_mask) << shift; + dst[1] = (*src & left_mask) >> (BITS_PER_LONG - shift); + dst++; + src++; + nbits -= BITS_PER_LONG; + } + + if (nbits > BITS_PER_LONG - shift) { + *dst |= (*src & right_mask) << shift; + nbits -= BITS_PER_LONG - shift; + last_mask = ((1ul << nbits) - 1) << (BITS_PER_LONG - shift); + dst[1] = (*src & last_mask) >> (BITS_PER_LONG - shift); + } else if (nbits) { + last_mask = (1ul << nbits) - 1; + *dst |= (*src & last_mask) << shift; + } +} -- cgit v1.2.3