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-rw-r--r--include/osmocom/gsm/tlv.h15
1 files changed, 13 insertions, 2 deletions
diff --git a/include/osmocom/gsm/tlv.h b/include/osmocom/gsm/tlv.h
index 5bf4a87b..8654893b 100644
--- a/include/osmocom/gsm/tlv.h
+++ b/include/osmocom/gsm/tlv.h
@@ -90,13 +90,24 @@ static inline uint8_t *lv_put(uint8_t *buf, uint8_t len,
return buf + len;
}
-/*! put (append) a TLV field */
+/*! Append a TLV field, a Tag-Length-Value field.
+ * \param[out] buf Location in a buffer to append TLV at.
+ * \param[in] tag Tag id to write.
+ * \param[in] len Length field to write and amount of bytes to append.
+ * \param[in] val Pointer to data to append, or NULL to append zero data.
+ * Always append tag and length. Append \a len bytes read from \a val. If val is NULL, append \a len zero
+ * bytes instead. If \a len is zero, do not append any data apart from tag and length. */
static inline uint8_t *tlv_put(uint8_t *buf, uint8_t tag, uint8_t len,
const uint8_t *val)
{
*buf++ = tag;
*buf++ = len;
- memcpy(buf, val, len);
+ if (len) {
+ if (val)
+ memcpy(buf, val, len);
+ else
+ memset(buf, 0, len);
+ }
return buf + len;
}