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From: Stefano Brivio <sbrivio@redhat.com>
To: Pablo Neira Ayuso <pablo@netfilter.org>, netfilter-devel@vger.kernel.org
Cc: "Florian Westphal" <fw@strlen.de>,
	"Kadlecsik József" <kadlec@blackhole.kfki.hu>,
	"Eric Garver" <eric@garver.life>, "Phil Sutter" <phil@nwl.cc>
Subject: [PATCH nf-next v4 4/9] bitmap: Introduce bitmap_cut(): cut bits and shift remaining
Date: Wed, 22 Jan 2020 00:17:54 +0100
Message-ID: <a4ee22fb535ef6cf978085a2aa0980cbf48f3634.1579647351.git.sbrivio@redhat.com> (raw)
In-Reply-To: <cover.1579647351.git.sbrivio@redhat.com>

The new bitmap function bitmap_cut() copies bits from source to
destination by removing the region specified by parameters first
and cut, and remapping the bits above the cut region by right
shifting them.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
v4: No changes
v3: No changes
v2: No changes

 include/linux/bitmap.h |  4 +++
 lib/bitmap.c           | 66 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index ff335b22f23c..f0f3a9fffa6a 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -53,6 +53,7 @@
  *  bitmap_find_next_zero_area_off(buf, len, pos, n, mask)  as above
  *  bitmap_shift_right(dst, src, n, nbits)      *dst = *src >> n
  *  bitmap_shift_left(dst, src, n, nbits)       *dst = *src << n
+ *  bitmap_cut(dst, src, first, n, nbits)       Cut n bits from first, copy rest
  *  bitmap_replace(dst, old, new, mask, nbits)  *dst = (*old & ~(*mask)) | (*new & *mask)
  *  bitmap_remap(dst, src, old, new, nbits)     *dst = map(old, new)(src)
  *  bitmap_bitremap(oldbit, old, new, nbits)    newbit = map(old, new)(oldbit)
@@ -133,6 +134,9 @@ extern void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
 				unsigned int shift, unsigned int nbits);
 extern void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
 				unsigned int shift, unsigned int nbits);
+extern void bitmap_cut(unsigned long *dst, const unsigned long *src,
+		       unsigned int first, unsigned int cut,
+		       unsigned int nbits);
 extern int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 			const unsigned long *bitmap2, unsigned int nbits);
 extern void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 4250519d7d1c..6e175fbd69a9 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -168,6 +168,72 @@ void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
 }
 EXPORT_SYMBOL(__bitmap_shift_left);
 
+/**
+ * bitmap_cut() - remove bit region from bitmap and right shift remaining bits
+ * @dst: destination bitmap, might overlap with src
+ * @src: source bitmap
+ * @first: start bit of region to be removed
+ * @cut: number of bits to remove
+ * @nbits: bitmap size, in bits
+ *
+ * Set the n-th bit of @dst iff the n-th bit of @src is set and
+ * n is less than @first, or the m-th bit of @src is set for any
+ * m such that @first <= n < nbits, and m = n + @cut.
+ *
+ * In pictures, example for a big-endian 32-bit architecture:
+ *
+ * @src:
+ * 31                                   63
+ * |                                    |
+ * 10000000 11000001 11110010 00010101  10000000 11000001 01110010 00010101
+ *                 |  |              |                                    |
+ *                16  14             0                                   32
+ *
+ * if @cut is 3, and @first is 14, bits 14-16 in @src are cut and @dst is:
+ *
+ * 31                                   63
+ * |                                    |
+ * 10110000 00011000 00110010 00010101  00010000 00011000 00101110 01000010
+ *                    |              |                                    |
+ *                    14 (bit 17     0                                   32
+ *                        from @src)
+ *
+ * Note that @dst and @src might overlap partially or entirely.
+ *
+ * This is implemented in the obvious way, with a shift and carry
+ * step for each moved bit. Optimisation is left as an exercise
+ * for the compiler.
+ */
+void bitmap_cut(unsigned long *dst, const unsigned long *src,
+		unsigned int first, unsigned int cut, unsigned int nbits)
+{
+	unsigned int len = BITS_TO_LONGS(nbits);
+	unsigned long keep = 0, carry;
+	int i;
+
+	memmove(dst, src, len * sizeof(*dst));
+
+	if (first % BITS_PER_LONG) {
+		keep = src[first / BITS_PER_LONG] &
+		       (~0UL >> (BITS_PER_LONG - first % BITS_PER_LONG));
+	}
+
+	while (cut--) {
+		for (i = first / BITS_PER_LONG; i < len; i++) {
+			if (i < len - 1)
+				carry = dst[i + 1] & 1UL;
+			else
+				carry = 0;
+
+			dst[i] = (dst[i] >> 1) | (carry << (BITS_PER_LONG - 1));
+		}
+	}
+
+	dst[first / BITS_PER_LONG] &= ~0UL << (first % BITS_PER_LONG);
+	dst[first / BITS_PER_LONG] |= keep;
+}
+EXPORT_SYMBOL(bitmap_cut);
+
 int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 				const unsigned long *bitmap2, unsigned int bits)
 {
-- 
2.24.1


  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-21 23:17 [PATCH nf-next v4 0/9] nftables: Set implementation for arbitrary concatenation of ranges Stefano Brivio
2020-01-21 23:17 ` [PATCH nf-next v4 1/9] netfilter: nf_tables: add nft_setelem_parse_key() Stefano Brivio
2020-01-21 23:17 ` [PATCH nf-next v4 2/9] netfilter: nf_tables: add NFTA_SET_ELEM_KEY_END attribute Stefano Brivio
2020-01-21 23:17 ` [PATCH nf-next v4 3/9] netfilter: nf_tables: Support for sets with multiple ranged fields Stefano Brivio
2020-01-21 23:17 ` Stefano Brivio [this message]
2020-01-21 23:17 ` [PATCH nf-next v4 5/9] nf_tables: Add set type for arbitrary concatenation of ranges Stefano Brivio
2020-02-07 11:23   ` Pablo Neira Ayuso
2020-02-10 15:10     ` Stefano Brivio
2020-02-14 18:16       ` Pablo Neira Ayuso
2020-02-14 19:42         ` Stefano Brivio
2020-02-14 20:42           ` Pablo Neira Ayuso
2020-02-14 23:06             ` Stefano Brivio
2020-01-21 23:17 ` [PATCH nf-next v4 6/9] selftests: netfilter: Introduce tests for sets with range concatenation Stefano Brivio
2020-01-21 23:17 ` [PATCH nf-next v4 7/9] nft_set_pipapo: Prepare for vectorised implementation: alignment Stefano Brivio
2020-01-21 23:17 ` [PATCH nf-next v4 8/9] nft_set_pipapo: Prepare for vectorised implementation: helpers Stefano Brivio
2020-01-21 23:17 ` [PATCH nf-next v4 9/9] nft_set_pipapo: Introduce AVX2-based lookup implementation Stefano Brivio
2020-01-27  6:41   ` kbuild test robot
2020-01-27  8:20 ` [PATCH nf-next v4 0/9] nftables: Set implementation for arbitrary concatenation of ranges Pablo Neira Ayuso
2020-02-20 10:52 ` Phil Sutter
2020-02-20 11:04   ` Stefano Brivio

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