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authorSander Vrijders <sander.vrijders@intec.ugent.be>2016-02-17 17:19:08 +0100
committerSander Vrijders <sander.vrijders@intec.ugent.be>2016-02-17 17:19:08 +0100
commit86bc5c03c08c4f62db02a41a734cc5ffdaada50f (patch)
tree4c75496d20bd40634684bbe3647cdc8429be8140 /src
parent2a207aaf819b4bc8edf8953a2cff8dd818d969e6 (diff)
downloadouroboros-86bc5c03c08c4f62db02a41a734cc5ffdaada50f.tar.gz
ouroboros-86bc5c03c08c4f62db02a41a734cc5ffdaada50f.zip
include: Add bitmap implementation
This adds a bitmap implementation loosely based on the one found in the Linux kernel. The functions in the header file actually act as a wrapper around the actual bitmap implementation for portability reasons.
Diffstat (limited to 'src')
-rw-r--r--src/lib/bitmap.c194
1 files changed, 194 insertions, 0 deletions
diff --git a/src/lib/bitmap.c b/src/lib/bitmap.c
new file mode 100644
index 00000000..3e1ba049
--- /dev/null
+++ b/src/lib/bitmap.c
@@ -0,0 +1,194 @@
+/*
+ * Ouroboros - Copyright (C) 2016
+ *
+ * Bitmap implementation - taken partly from Linux kernel
+ *
+ * Sander Vrijders <sander.vrijders@intec.ugent.be>
+ * Francesco Salvestrini <f.salvestrini@nextworks.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <ouroboros/bitmap.h>
+#include <stdbool.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BITS_PER_BYTE 8
+
+#define BITS_PER_LONG (sizeof(long) * BITS_PER_BYTE)
+
+#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
+
+#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
+
+#define BITS_TO_LONGS(nr) \
+ DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
+
+#define BITS_IN_BITMAP ((2 << BITS_PER_BYTE) * sizeof(size_t))
+
+static unsigned long find_next_zero_bit(const unsigned long * addr,
+ unsigned long nbits)
+{
+ unsigned long tmp;
+ unsigned long start = 0;
+ unsigned long pos = 0;
+ unsigned long mask;
+
+ /* First find correct word */
+ tmp = ~addr[start];
+ while (!tmp) {
+ start++;
+ if (start >= (nbits / BITS_PER_LONG))
+ return nbits;
+
+ tmp = ~addr[start];
+ }
+
+ /* Find the free bit in the word */
+ mask = 1UL;
+ while (!(tmp ^ mask)) {
+ pos++;
+ mask = 1UL << pos;
+ }
+
+ return (start * BITS_PER_LONG) + pos;
+}
+
+static void bitmap_zero(unsigned long * dst,
+ unsigned int nbits)
+{
+ unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
+ memset(dst, 0, len);
+}
+
+static void bitmap_clear(unsigned long * map,
+ unsigned int start)
+{
+ unsigned long * p = map + BIT_WORD(start);
+ unsigned long mask = ~(1UL << (start % (BITS_PER_LONG - 1)));
+
+ *p &= mask;
+}
+
+
+static void bitmap_set(unsigned long * map,
+ unsigned int start)
+{
+ unsigned long * p = map + BIT_WORD(start);
+ unsigned long mask = 1UL << (start % (BITS_PER_LONG - 1));
+
+ *p |= mask;
+}
+
+struct rbmp {
+ ssize_t offset;
+ size_t size;
+
+ unsigned long bitmap[BITS_TO_LONGS(BITS_IN_BITMAP)];
+};
+
+struct rbmp * rbmp_create(size_t bits, ssize_t offset)
+{
+ struct rbmp * tmp;
+
+ if (bits == 0)
+ return NULL;
+
+ tmp = malloc(sizeof(*tmp));
+ if (!tmp)
+ return NULL;
+
+ tmp->size = bits;
+ tmp->offset = offset;
+ bitmap_zero(tmp->bitmap, BITS_IN_BITMAP);
+
+ return tmp;
+}
+
+
+int rbmp_destroy(struct rbmp * b)
+{
+ if (!b)
+ return -1;
+
+ free(b);
+
+ return 0;
+}
+
+static ssize_t bad_id(struct rbmp * b)
+{
+ assert(b);
+
+ return b->offset - 1;
+}
+
+ssize_t rbmp_allocate(struct rbmp * b)
+{
+ ssize_t id;
+
+ if (!b)
+ return bad_id(b);
+
+ id = (ssize_t) find_next_zero_bit(b->bitmap,
+ BITS_IN_BITMAP);
+
+ if (id == BITS_IN_BITMAP)
+ return bad_id(b);
+
+ bitmap_set(b->bitmap, id);
+
+ return id + b->offset;
+}
+
+static bool is_id_ok(struct rbmp * b,
+ ssize_t id)
+{
+ assert(b);
+
+ if ((id < b->offset) || (id > (b->offset + b->size)))
+ return false;
+
+ return true;
+}
+
+bool rbmp_is_id_ok(struct rbmp * b,
+ ssize_t id)
+{
+ if (!b)
+ return false;
+
+ return is_id_ok(b, id);
+}
+
+int rbmp_release(struct rbmp * b,
+ ssize_t id)
+{
+ ssize_t rid;
+
+ if (!b)
+ return -1;
+
+ if (!is_id_ok(b, id))
+ return -1;
+
+ rid = id - b->offset;
+
+ bitmap_clear(b->bitmap, id);
+
+ return 0;
+}