[PATCH] bitmap: add scan init at given position

[Volodymyr Fialko]

Currently, in the case when we search for a bit set after a particular
value, the bitmap has to be scanned from the beginning and
rte_bitmap_scan() has to be called multiple times until we hit the value.

Add a new __rte_bitmap_scan_init_at() function to initialize scan state at
the given position, this will allow getting the next bit set after some
value within one rte_bitmap_scan() call.

Signed-off-by: Volodymyr Fialko <vfialko at marvell.com>
---
 app/test/test_bitmap.c       | 23 +++++++++++++++++++++++
 lib/eal/include/rte_bitmap.h | 22 ++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/app/test/test_bitmap.c b/app/test/test_bitmap.c
index e9c61590ae..69ff7262f3 100644
--- a/app/test/test_bitmap.c
+++ b/app/test/test_bitmap.c
@@ -71,6 +71,29 @@ test_bitmap_scan_operations(struct rte_bitmap *bmp)
 		return TEST_FAILED;
 	}
 
+	/* Scan reset with count check. */
+	__rte_bitmap_scan_init_at(bmp, pos + RTE_BITMAP_SLAB_BIT_SIZE);
+	if (!rte_bitmap_scan(bmp, &pos, &out_slab)) {
+		printf("Failed to get slab from bitmap.\n");
+		return TEST_FAILED;
+	}
+
+	if (slab2_magic != out_slab) {
+		printf("Scan init at operation failed.\n");
+		return TEST_FAILED;
+	}
+
+	__rte_bitmap_scan_init_at(bmp, pos + 2 * RTE_BITMAP_SLAB_BIT_SIZE);
+	if (!rte_bitmap_scan(bmp, &pos, &out_slab)) {
+		printf("Failed to get slab from bitmap.\n");
+		return TEST_FAILED;
+	}
+
+	if (slab1_magic != out_slab) {
+		printf("Scan init at operation failed.\n");
+		return TEST_FAILED;
+	}
+
 	/* Test scan when a cline is half full */
 	rte_bitmap_reset(bmp);
 	for (i = 0; i < MAX_BITS; i++)
diff --git a/lib/eal/include/rte_bitmap.h b/lib/eal/include/rte_bitmap.h
index 27ee3d18a4..54a986aa8f 100644
--- a/lib/eal/include/rte_bitmap.h
+++ b/lib/eal/include/rte_bitmap.h
@@ -137,6 +137,28 @@ __rte_bitmap_scan_init(struct rte_bitmap *bmp)
 	bmp->go2 = 0;
 }
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Bitmap initialize internal scan pointers at the given position for the scan function.
+ * @see rte_bitmap_scan()
+ *
+ * @param bmp
+ *   Handle to bitmap instance
+ * @param pos
+ *   Bit position to start scan
+ */
+__rte_experimental
+static inline void
+__rte_bitmap_scan_init_at(struct rte_bitmap *bmp, uint32_t pos)
+{
+	bmp->index1 = pos >> (RTE_BITMAP_SLAB_BIT_SIZE_LOG2 + RTE_BITMAP_CL_BIT_SIZE_LOG2);
+	bmp->offset1 = (pos >> RTE_BITMAP_CL_BIT_SIZE_LOG2) & RTE_BITMAP_SLAB_BIT_MASK;
+	bmp->index2 = pos >> RTE_BITMAP_SLAB_BIT_SIZE_LOG2;
+	bmp->go2 = 1;
+}
+
 /**
  * Bitmap memory footprint calculation
  *
-- 
2.34.1