Protocol: new functions and associated docs.

The header declares new functions:

	* tlv_init()
	* tlv_destroy()
	* tlv_push()
	* tlv_get_raw()
	* tlv_raw_size()

Signed-off-by: Ramūnas Mažeikis <ramunasnezinomas@gmail.com>

2 files changed, 61 insertions, 6 deletions

diff --git a/include/protocol.h b/include/protocol.h
index 34ad4a3..38f5aa9 100644
--- a/include/protocol.h
+++ b/include/protocol.h
@@ -23,10 +23,11 @@
 
 #include <errno.h>
 
-#define	E_TLV_OVERFLOW		(1 << 0)
+#define E_TLV_OVERFLOW		(1 << 0)
 #define E_UNKNOWN_TYPE		(1 << 1)
-#define E_IVALID_DESCRIPTOR	(1 << 2)
-#define END_OF_PACKET		(1 << 3)
+#define END_OF_PACKET		(1 << 2)
+
+#define TLV_SZ_MAX_RAW		(MTU - 64)
 
 /**
  * Regular packets contain tlv's defined by tlv_type.
@@ -122,16 +123,38 @@ int get_tlv(struct tlv_parser *parser, struct tlv *ret);
  * */
 int push_data(struct tlv_packet *packet, enum tlv_type type, char *data);
 
-
 /**
  * Resets offset to 0 and set entire buffer to 0.
  */
 void clear_data(struct tlv_packet *packet);
 
+/**
+ * Initialises tlv to sane values.
+ */
+void tlv_init(struct tlv *t);
+
+/**
+ * Frees data held in the tlv structure. The structure itself shall be freed as
+ * needed by calling code.
+ */
+void tlv_destroy(struct tlv *t);
+
+/**
+ * Tells amount of bytes needed to push tlv to a buffer
+ */
+size_t tlv_raw_size(struct tlv *t);
+
+/**
+ * Pushes tlv to buffer as contiguous data. Check tlv size with tlv_raw_size
+ * beforehand. If you don't do that and overflow --- tough tiddy.
+ */
+int tlv_get_raw(struct tlv *t, char *buf);
 
 /**
- * Tells what size of buffer is needed for next tlv.
+ * Pushes data to tlv. Returns E_TLV_OVERFLOW if pushing data would cause the
+ * final size to be greater than TLV_SZ_MAX_RAW. In case of such error the data is left
+ * untouched.
  */
-size_t tlv_data_size(struct tlv_parser *parser);
+int tlv_push(struct tlv *t, const char *data, size_t size);
 
 #endif /* USURPATION_PROTOCOL_H_INCLUDED */
diff --git a/src/common/protocol.c b/src/common/protocol.c
index b2e0d40..edaf491 100644
--- a/src/common/protocol.c
+++ b/src/common/protocol.c
@@ -131,3 +131,35 @@ size_t tlv_data_size(struct tlv_parser *parser)
 	}
 	return size;
 }
+
+void tlv_destroy(struct tlv *t)
+{
+	free(t->data);
+	t->length = 0;
+}
+
+size_t tlv_raw_size(struct tlv *t)
+{
+	return sizeof(*t) + t->length;
+}
+
+int tlv_push(struct tlv *t, const char *data, size_t size)
+{
+	int ret = 0;
+	size_t final_size = tlv_raw_size(t) + size;
+	if (final_size > TLV_SZ_MAX_RAW) {
+		ret = E_TLV_OVERFLOW;
+	} else {
+		t->data = realloc(t->data, final_size);
+		memcpy(t->data + t->length, data, size);
+		t->length = final_size;
+	}
+	return ret;
+}
+
+void tlv_init(struct tlv *t)
+{
+	t->type = TEXT;
+	t->length = 0;
+	t->data = NULL;
+}
\ No newline at end of file