From: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
For small unique id generation we may use bitfield since it is very fast
and memory efficient. Helpers are added to generate id from 1 to 32 to
utils.
---
src/shared/util.c | 29 +++++++++++++++++++++++++++++
src/shared/util.h | 3 +++
2 files changed, 32 insertions(+)
diff --git a/src/shared/util.c b/src/shared/util.c
index 74ffb08..a70c709 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -33,6 +33,7 @@
#include <unistd.h>
#include <dirent.h>
#include <limits.h>
+#include <string.h>
#include "src/shared/util.h"
@@ -106,3 +107,31 @@ unsigned char util_get_dt(const char *parent, const char *name)
return DT_UNKNOWN;
}
+
+/* Helpers for bitfield operations */
+
+/* Find unique id in range from 1 to max but no bigger then
+ * sizeof(int) * 8. ffs() is used since it is POSIX standard
+ */
+uint8_t util_get_uid(unsigned int *bitmap, uint8_t max)
+{
+ uint8_t id;
+
+ id = ffs(~*bitmap);
+
+ if (!id || id > max)
+ return 0;
+
+ *bitmap |= 1 << (id - 1);
+
+ return id;
+}
+
+/* Clear id bit in bitmap */
+void util_clear_uid(unsigned int *bitmap, uint8_t id)
+{
+ if (!id)
+ return;
+
+ *bitmap &= ~(1 << (id - 1));
+}
diff --git a/src/shared/util.h b/src/shared/util.h
index 8437662..7dba1b3 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -93,6 +93,9 @@ void util_hexdump(const char dir, const unsigned char *buf, size_t len,
unsigned char util_get_dt(const char *parent, const char *name);
+uint8_t util_get_uid(unsigned int *bitmap, uint8_t max);
+void util_clear_uid(unsigned int *bitmap, uint8_t id);
+
static inline void bswap_128(const void *src, void *dst)
{
const uint8_t *s = src;
--
2.1.0
--
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