1 files changed, 112 insertions, 0 deletions
diff --git a/bitmap.h b/bitmap.h
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+/**
+ * bitmap.h
+ * Copyright (c) 2022 Jon Santmyer <jon@jonsantmyer.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * A freestanding implementation of a variable length bitmap.
+ * Depends on compiler provided header files
+ * stdint, stddef, stdbool
+ *
+ *  Allocation for bitmap_vl is dependent on allocator implementation
+ *  Static length bitmaps can be defined using this example
+ *
+ *  struct bitmap_sl
+ *  {
+ *      struct bitmap_head head;
+ *      bmcell_t cells[BITMAP_CELLS(n)];
+ *  };
+ *  where n is the number of bits you want in the bitmap
+ *  To use said struct, you need to feed bmvl_setup with a cast pointer to
+ *  bitmap_sl and the number of bits you have.
+ *
+ *  For other bit systems, replace the type defined as 
+ *  bm_signed_t and bm_unsigned_t
+ *  with an (u)int_t type of the proper bit length
+ *  
+ *  For using the bitmap, use the functions declared under #define blocks.
+ *  The hidden functions are for genericising other bitmap types following
+ *  the above format.
+ *
+ *  bitmap_head contains a last_free variable which is used to accelerate the
+ *  average allocation times. Instead of iterating through the entire map, the
+ *  allocator can iterate from last_free until length.
+ *  Most bm_take operations will be O(1) because last_free is assumed to mark an
+ *  empty bit in the map
+ */
+
+#ifndef BITMAP_H
+#define BITMAP_H 1
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+
+/*Can be changed to int32_t/uint32_t for 32-bit systems*/
+typedef int64_t bm_signed_t;
+typedef uint64_t bm_unsigned_t;
+typedef bm_unsigned_t bmcell_t;
+
+struct bitmap_head
+{
+    size_t length;
+    size_t bits_free;
+    size_t last_free;
+};
+
+struct bitmap_vl
+{
+    struct bitmap_head head;
+    bmcell_t cells[];
+};
+
+#define BITMAP_BITS_PER_CELL (8 * sizeof(bmcell_t))
+#define BITMAP_CELLS(bits) \
+    ((bits + (BITMAP_BITS_PER_CELL - 1)) / (BITMAP_BITS_PER_CELL))
+#define BITMAP_LEN(bits) ((bits / 8) + (sizeof(struct bitmap_head)))
+
+/*Fills a bitmap struct with proper length, and status vars. Zeros the cells*/
+void bmvl_setup(struct bitmap_vl *bm, size_t bits);
+
+/*Check if bit in bitmap is taken*/
+bool __bm_test(bmcell_t *cells, size_t i);
+#define bm_test(bitmap, i) __bm_test(bitmap->cells, i)
+
+/*Functions for taking free bits in the bitmap. Returns -1 if none are
+ * available. Returns the index of the (first) bit if a suitable range is found
+ */
+bm_signed_t __bm_take(struct bitmap_head *head, bmcell_t *cells);
+bm_signed_t __bm_take_contig(struct bitmap_head *head, bmcell_t *cells, size_t l);
+#define bm_take(bitmap) __bm_take(&bitmap->head, bitmap->cells)
+#define bm_take_contig(bitmap, l) \
+    __bm_take_contig(&bitmap->head, bitmap->cells, l)
+
+/* Fills the bit/bits at i. Runs until l if applicable */
+void __bm_reserve(struct bitmap_head *head, bmcell_t *cells, size_t i);
+void __bm_reserve_contig(struct bitmap_head *head, bmcell_t *cells, size_t i, size_t l);
+#define bm_reserve(bitmap, i) __bm_reserve(&bitmap->head, bitmap->cells, i)
+#define bm_reserve_contig(bitmap, i, l) __bm_reserve_contig(&bitmap->head, bitmap->cells, i, l)
+
+/* Clears the bit/bits at i. Runs until l if applicable */
+void __bm_release(struct bitmap_head *head, bmcell_t *cells, size_t i);
+void __bm_release_contig(struct bitmap_head *head, bmcell_t *cells, size_t i, size_t l);
+#define bm_release(bitmap, i) __bm_release(&bitmap->head, bitmap->cells, i)
+#define bm_release_contig(bitmap, i, l) __bm_release_contig(&bitmap->head, bitmap->cells, i, l)
+
+#endif