bitmap

include/lang2/bitmap.h

@@ -0,0 +1,25 @@
+#ifndef L2_BITMAP_H
+#define L2_BITMAP_H
+
+#include <stdlib.h>
+#include <stdint.h>
+
+typedef long long int l2_bitmap_entry;
+
+struct l2_bitmap {
+	l2_bitmap_entry *tables;
+	size_t tableslen;
+	size_t currtable;
+
+	l2_bitmap_entry *dirs;
+	size_t dirslen;
+	size_t currdir;
+};
+
+void l2_bitmap_init(struct l2_bitmap *bm);
+void l2_bitmap_free(struct l2_bitmap *bm);
+int l2_bitmap_get(struct l2_bitmap *bm, size_t id);
+size_t l2_bitmap_set_next(struct l2_bitmap *bm);
+void l2_bitmap_unset(struct l2_bitmap *bm, size_t id);
+
+#endif

src/bitmap.c

@@ -0,0 +1,114 @@
+#include "bitmap.h"
+
+#include <string.h>
+#include <strings.h>
+#include <limits.h>
+
+#include <stdio.h>
+
+#define ENTSIZ (sizeof(l2_bitmap_entry) * CHAR_BIT)
+
+static l2_bitmap_entry first_unset_bit(l2_bitmap_entry n) {
+	return ~n & (n + 1);
+}
+
+#if defined(__GLIBC__) && ( \
+		(__GLIBC__>= 2 && __GLIBC_MINOR__ >= 27) || \
+		_GNU_SOURCE)
+#define first_set ffsll
+#else
+static int first_set(l2_bitmap_entry n) {
+}
+#endif
+
+static void expand_tables(struct l2_bitmap *bm) {
+	while (bm->currtable >= bm->tableslen) {
+		bm->tables = realloc(bm->tables, bm->tableslen * 2 * sizeof(*bm->tables));
+		memset(bm->tables + bm->tableslen, 0, sizeof(*bm->tables) * bm->tableslen);
+		bm->tableslen *= 2;
+	}
+}
+
+void l2_bitmap_init(struct l2_bitmap *bm) {
+	bm->tableslen = 4;
+	bm->tables = calloc(bm->tableslen, sizeof(*bm->tables));
+	bm->currtable = 0;
+	bm->dirslen = 1;
+	bm->dirs = calloc(bm->dirslen, sizeof(*bm->dirs));
+	bm->currdir = 0;
+}
+
+void l2_bitmap_free(struct l2_bitmap *bm) {
+	free(bm->tables);
+	free(bm->dirs);
+}
+
+int l2_bitmap_get(struct l2_bitmap *bm, size_t id) {
+	size_t tblidx = id / ENTSIZ;
+	size_t tblbit = id % ENTSIZ;
+	if (tblidx >= bm->tableslen) {
+		return 0;
+	}
+
+	return !!(bm->tables[tblidx] & (l2_bitmap_entry)1 << tblbit);
+}
+
+size_t l2_bitmap_set_next(struct l2_bitmap *bm) {
+	l2_bitmap_entry *table = &bm->tables[bm->currtable];
+	l2_bitmap_entry bit = first_unset_bit(*table);
+	*table |= bit;
+	size_t ret = bm->currtable * ENTSIZ + first_set(bit) - 1;
+
+	// Still free space?
+	if (*table != ~(l2_bitmap_entry)0) {
+		return ret;
+	}
+
+	// Ok, this entry is full then...
+	l2_bitmap_entry *dir = &bm->dirs[bm->currdir];
+	*dir |= (l2_bitmap_entry)1 << (bm->currtable % ENTSIZ);
+
+	// Is there still space in this directory?
+	if (*dir != ~(l2_bitmap_entry)0) {
+		bm->currtable = bm->currdir * ENTSIZ + first_set(first_unset_bit(*dir)) - 1;
+		expand_tables(bm);
+		return ret;
+	}
+
+	// Is there a directory with free space?
+	for (size_t i = 0; i < bm->dirslen; ++i) {
+		dir = &bm->dirs[i];
+		if (*dir == ~(l2_bitmap_entry)0) {
+			continue;
+		}
+
+		bm->currdir = i;
+		bm->currtable = bm->currdir * ENTSIZ + first_set(first_unset_bit(*dir)) - 1;
+		expand_tables(bm);
+
+		return ret;
+	}
+
+	// Ok, we gotta make a new dir then
+	bm->currdir = bm->dirslen;
+	bm->currtable = bm->currdir * ENTSIZ;
+	bm->dirs = realloc(bm->dirs, bm->dirslen * 2 * sizeof(*bm->dirs));
+	memset(bm->dirs + bm->dirslen, 0, sizeof(*bm->dirs) * bm->dirslen);
+	bm->dirslen *= 2;
+	expand_tables(bm);
+	return ret;
+}
+
+void l2_bitmap_unset(struct l2_bitmap *bm, size_t id) {
+	size_t tblidx = id / ENTSIZ;
+	size_t tblbit = id % ENTSIZ;
+	size_t diridx = id / (ENTSIZ * ENTSIZ);
+	size_t dirbit = (id / ENTSIZ) % ENTSIZ;
+
+	if (tblidx >= bm->tableslen) {
+		return;
+	}
+
+	bm->tables[tblidx] &= ~((l2_bitmap_entry)1 << tblbit);
+	bm->dirs[diridx] &= ~((l2_bitmap_entry)1 << dirbit);
+}