From b0708d3e769851093ef633844d894b683a3c0341 Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@gnumonks.org>
Date: Mon, 4 Feb 2019 12:09:05 +0100
Subject: bitvec: Add bitvec_tailroom_bits() function

This is similar to msgb_tailroom(): It returns the amount of space
left at the end of the bit vector (compared to the current cursor).

The function returns the number of bits left in the bitvec.

Change-Id: I8980a6b6d1973b67a2d9ad411c878d956fb428d1
---
 include/osmocom/core/bitvec.h |  6 ++++++
 tests/bitvec/bitvec_test.c    | 19 +++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/osmocom/core/bitvec.h b/include/osmocom/core/bitvec.h
index da2d4e45..bd107093 100644
--- a/include/osmocom/core/bitvec.h
+++ b/include/osmocom/core/bitvec.h
@@ -93,4 +93,10 @@ static inline unsigned int bitvec_used_bytes(const struct bitvec *bv)
 	return bytes;
 }
 
+/*! Return the tailroom in number of unused bits remaining in the bit-vector */
+static inline unsigned int bitvec_tailroom_bits(const struct bitvec *bv)
+{
+	return bv->data_len*8 - bv->cur_bit;
+}
+
 /*! @} */
diff --git a/tests/bitvec/bitvec_test.c b/tests/bitvec/bitvec_test.c
index c8795dbd..fbf5c5dd 100644
--- a/tests/bitvec/bitvec_test.c
+++ b/tests/bitvec/bitvec_test.c
@@ -204,6 +204,24 @@ static void test_used_bytes()
 	}
 }
 
+static void test_tailroom()
+{
+	struct bitvec b;
+	uint8_t d[32];
+	unsigned int i;
+
+	b.data = d;
+	b.data_len = sizeof(d);
+	bitvec_zero(&b);
+
+	OSMO_ASSERT(bitvec_tailroom_bits(&b) == sizeof(d)*8);
+
+	for (i = 0; i < 8*sizeof(d); i++) {
+		bitvec_set_bit(&b, 1);
+		OSMO_ASSERT(bitvec_tailroom_bits(&b) == sizeof(d)*8-(i+1));
+	}
+}
+
 int main(int argc, char **argv)
 {
 	struct bitvec bv;
@@ -311,6 +329,7 @@ int main(int argc, char **argv)
 
 	printf("\nbitvec bytes used.\n");
 	test_used_bytes();
+	test_tailroom();
 
 	printf("\nbitvec ok.\n");
 	return 0;
-- 
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