X-Git-Url: http://sigrok.org/gitweb/?a=blobdiff_plain;f=src%2Fstrutil.c;h=050f37bf7090532cc67282e07c10ce2867a985b6;hb=HEAD;hp=63cd2fdfc62baf8e2ea65b88f9a0378ceee3a23e;hpb=227913f26433bb09b353c2339c1ecc339692df61;p=libsigrok.git

diff --git a/src/strutil.c b/src/strutil.c
index 63cd2fdf..2136bd49 100644
--- a/src/strutil.c
+++ b/src/strutil.c
@@ -1819,4 +1819,57 @@ SR_API char *sr_text_next_word(char *s, char **next)
 	return word;
 }
 
+/**
+ * Get the number of necessary bits to hold a given value. Also gets
+ * the next power-of-two value at or above the caller provided value.
+ *
+ * @param[in] value The value that must get stored.
+ * @param[out] bits The required number of bits.
+ * @param[out] power The corresponding power-of-two.
+ *
+ * @return SR_OK upon success, SR_ERR* otherwise.
+ *
+ * TODO Move this routine to a more appropriate location, it is not
+ * strictly string related.
+ *
+ * @since 0.6.0
+ */
+SR_API int sr_next_power_of_two(size_t value, size_t *bits, size_t *power)
+{
+	size_t need_bits;
+	size_t check_mask;
+
+	if (bits)
+		*bits = 0;
+	if (power)
+		*power = 0;
+
+	/*
+	 * Handle the special case of input value 0 (needs 1 bit
+	 * and results in "power of two" value 1) here. It is not
+	 * covered by the generic logic below.
+	 */
+	if (!value) {
+		if (bits)
+			*bits = 1;
+		if (power)
+			*power = 1;
+		return SR_OK;
+	}
+
+	need_bits = 0;
+	check_mask = 0;
+	do {
+		need_bits++;
+		check_mask <<= 1;
+		check_mask |= 1UL << 0;
+	} while (value & ~check_mask);
+
+	if (bits)
+		*bits = need_bits;
+	if (power)
+		*power = ++check_mask;
+	return SR_OK;
+}
+
 /** @} */