der_encode_to_buffer()

ChangeLog

@@ -15,6 +15,7 @@
 	* ber_dec_rval_t renamed into asn_dec_rval_t: more generality.
 	* Removed order dependency in DEFAULT references to ENUMERATED
 	  identifiers (./tests/68-*-OK.asn1).
+	* Implemented der_encode_to_buffer() procedure.
 
 0.9.7.1:	2004-Oct-12
 

skeletons/der_encoder.c

@@ -28,6 +28,50 @@ der_encode(asn_TYPE_descriptor_t *type_descriptor, void *struct_ptr,
 		consume_bytes, app_key);
 }
 
+/*
+ * Argument type and callback necessary for der_encode_to_buffer().
+ */
+typedef struct enc_to_buf_arg {
+	void *buffer;
+	size_t left;
+} enc_to_buf_arg;
+static int encode_to_buffer_cb(const void *buffer, size_t size, void *key) {
+	enc_to_buf_arg *arg = key;
+
+	if(arg->left < size)
+		return -1;	/* Data exceeds the available buffer size */
+
+	memcpy(arg->buffer, buffer, size);
+	arg->buffer = ((char *)arg->buffer) + size;
+	arg->left -= size;
+
+	return 0;
+}
+
+/*
+ * A variant of the der_encode() which encodes the data into the provided buffer
+ */
+asn_enc_rval_t
+der_encode_to_buffer(asn_TYPE_descriptor_t *type_descriptor, void *struct_ptr,
+	void *buffer, size_t *buffer_size) {
+	enc_to_buf_arg arg;
+	asn_enc_rval_t ec;
+
+	arg.buffer = buffer;
+	arg.left = *buffer_size;
+
+	ec = type_descriptor->der_encoder(type_descriptor,
+		struct_ptr,	/* Pointer to the destination structure */
+		0, 0, encode_to_buffer_cb, &arg);
+	if(ec.encoded != -1) {
+		assert(ec.encoded == (*buffer_size - arg.left));
+		/* Return the encoded contents size */
+		*buffer_size = ec.encoded;
+	}
+	return ec;
+}
+
+
 /*
  * Write out leading TL[v] sequence according to the type definition.
  */

skeletons/der_encoder.h

@@ -18,6 +18,14 @@ asn_enc_rval_t der_encode(struct asn_TYPE_descriptor_s *type_descriptor,
 		void *app_key		/* Arbitrary callback argument */
 	);
 
+/* A variant of der_encode() which encodes data into the pre-allocated buffer */
+asn_enc_rval_t der_encode_to_buffer(
+		struct asn_TYPE_descriptor_s *type_descriptor,
+		void *struct_ptr,	/* Structure to be encoded */
+		void *buffer,		/* Pre-allocated buffer */
+		size_t *buffer_size	/* Initial buffer size (max) */
+	);
+
 /*
  * Type of the generic DER encoder.
  */