proposal: Add possibility to register custom proposal keyword parser

If a proposal string cannot be matched to a token using strcmp (e.g. if
you want to register a whole class of algorithms containing their ID,
like my_alg_2342), you can use the provided function to register a
parser that transforms the given string into a proposal token.

Signed-off-by: Thomas Egerer <[email protected]>

src/libstrongswan/crypto/proposal/proposal_keywords.h

@@ -46,6 +46,8 @@
 typedef struct proposal_token_t proposal_token_t;
 typedef struct proposal_keywords_t proposal_keywords_t;
 
+typedef proposal_token_t*(*proposal_algname_parser_t)(const char *algname);
+
 #include <library.h>
 #include <crypto/transform.h>
 
@@ -101,6 +103,17 @@ struct proposal_keywords_t {
 						   transform_type_t type, u_int16_t algorithm,
 						   u_int16_t keysize);
 
+	/**
+	 * Register an algorithm name parser.
+	 *
+	 * It is meant to parse an algorithm name into a proposal token in a
+	 * generic, user defined way.
+	 *
+	 * @param parser	a pointer to the parser function
+	 */
+	void (*register_algname_parser)(proposal_keywords_t *this,
+									proposal_algname_parser_t parser);
+
 	/**
 	 * Destroy a proposal_keywords_t instance.
 	 */