1 files changed, 120 insertions, 0 deletions

diff --git a/include/cutils/bitops.h b/include/cutils/bitops.h
new file mode 100644
index 000000000..045830d90
--- /dev/null
+++ b/include/cutils/bitops.h
@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __CUTILS_BITOPS_H
+#define __CUTILS_BITOPS_H
+
+#include <stdbool.h>
+#include <string.h>
+#include <strings.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/*
+ * Bitmask Operations
+ *
+ * Note this doesn't provide any locking/exclusion, and isn't atomic.
+ * Additionally no bounds checking is done on the bitmask array.
+ *
+ * Example:
+ *
+ * int num_resources;
+ * unsigned int resource_bits[BITS_TO_WORDS(num_resources)];
+ * bitmask_init(resource_bits, num_resources);
+ * ...
+ * int bit = bitmask_ffz(resource_bits, num_resources);
+ * bitmask_set(resource_bits, bit);
+ * ...
+ * if (bitmask_test(resource_bits, bit)) { ... }
+ * ...
+ * bitmask_clear(resource_bits, bit);
+ *
+ */
+
+#define BITS_PER_WORD    (sizeof(unsigned int) * 8)
+#define BITS_TO_WORDS(x) (((x) + BITS_PER_WORD - 1) / BITS_PER_WORD)
+#define BIT_IN_WORD(x)   ((x) % BITS_PER_WORD)
+#define BIT_WORD(x)      ((x) / BITS_PER_WORD)
+#define BIT_MASK(x)      (1 << BIT_IN_WORD(x))
+
+static inline void bitmask_init(unsigned int *bitmask, int num_bits)
+{
+    memset(bitmask, 0, BITS_TO_WORDS(num_bits)*sizeof(unsigned int));
+}
+
+static inline int bitmask_ffz(unsigned int *bitmask, int num_bits)
+{
+    int bit, result;
+    size_t i;
+
+    for (i = 0; i < BITS_TO_WORDS(num_bits); i++) {
+        bit = ffs(~bitmask[i]);
+        if (bit) {
+            // ffs is 1-indexed, return 0-indexed result
+            bit--;
+            result = BITS_PER_WORD * i + bit;
+            if (result >= num_bits)
+                return -1;
+            return result;
+        }
+    }
+    return -1;
+}
+
+static inline int bitmask_weight(unsigned int *bitmask, int num_bits)
+{
+    size_t i;
+    int weight = 0;
+
+    for (i = 0; i < BITS_TO_WORDS(num_bits); i++)
+        weight += __builtin_popcount(bitmask[i]);
+    return weight;
+}
+
+static inline void bitmask_set(unsigned int *bitmask, int bit)
+{
+    bitmask[BIT_WORD(bit)] |= BIT_MASK(bit);
+}
+
+static inline void bitmask_clear(unsigned int *bitmask, int bit)
+{
+    bitmask[BIT_WORD(bit)] &= ~BIT_MASK(bit);
+}
+
+static inline bool bitmask_test(unsigned int *bitmask, int bit)
+{
+    return bitmask[BIT_WORD(bit)] & BIT_MASK(bit);
+}
+
+static inline int popcount(unsigned int x)
+{
+    return __builtin_popcount(x);
+}
+
+static inline int popcountl(unsigned long x)
+{
+    return __builtin_popcountl(x);
+}
+
+static inline int popcountll(unsigned long long x)
+{
+    return __builtin_popcountll(x);
+}
+
+__END_DECLS
+
+#endif /* __CUTILS_BITOPS_H */