Default put/unput routines

 - After der_unpack() use der_put_default() to allow defaults to be set
 - Before der_pack() use der_unput_default() to remove values matching the default

include/arpa2/quick-der.h

@@ -720,6 +720,24 @@ int der_get_bool (dercursor crs, bool *valp);
 typedef uint8_t der_buf_bool_t [1];
 dercursor der_put_bool (uint8_t *der_buf_bool, bool value);
 
+/* When the optional is absent, set its value to the default.
+ * Since Quick DER does not process default values, this must be
+ * done manually.  The work can help to simplify programs, by
+ * reducing the number of code paths and improve coverage.
+ *
+ * This function is not directly usable for CHOICE, which is
+ * unrolled into a sequence of dercursor values that may or may
+ * not have a value, but the multiplicity of the values is not
+ * taken care of below.
+ */
+void der_put_default (dercursor *optional, dercursor default_value);
+
+/* Test if the appointed optional equals the default.  If so, set it
+ * to the default/absent entry, .derptr==NULL and .derlen==0
+ * This is useful prior to sending.
+ */
+void der_unput_default (dercursor *optional, dercursor default_value);
+
 /* Compare the values pointed to by cursors @p c1 and @p c2.
  * Returns 0 if the (binary) values are equal, otherwise returns
  * the difference between the first two differing bytes (similar

lib/CMakeLists.txt

@@ -23,6 +23,8 @@ set(quickder_SRC
 	der_put_uint32.c
 	der_get_bool.c
 	der_put_bool.c
+	der_put_default.c
+	der_unput_default.c
 	der_cmp.c
 	der_cmp_int.c
 )

lib/der_put_default.c

@@ -0,0 +1,18 @@
+
+#include <arpa2/quick-der.h>
+
+/* When the optional is absent, set its value to the default.
+ * Since Quick DER does not process default values, this must be
+ * done manually.  The work can help to simplify programs, by
+ * reducing the number of code paths and improve coverage.
+ *
+ * This function is not directly usable for CHOICE, which is
+ * unrolled into a sequence of dercursor values that may or may
+ * not have a value, but the multiplicity of the values is not
+ * taken care of below.
+ */
+void der_put_default (dercursor *optional, dercursor default_value) {
+	if (optional->derptr == NULL) {
+		*optional = default_value;
+	}
+}

lib/der_unput_default.c

@@ -0,0 +1,12 @@
+
+#include <arpa2/quick-der.h>
+
+/* Test if the appointed optional equals the default.  If so, set it
+ * to the default/absent entry, .derptr==NULL and .derlen==0
+ * This is useful prior to sending.
+ */
+void der_unput_default (dercursor *optional, dercursor default_value) {
+	if (der_cmp (*optional, default_value) == 0) {
+		memset (optional, 0, sizeof (dercursor));
+	}
+}

test/CMakeLists.txt

@@ -55,3 +55,4 @@ c_test(der_data)
 c_test(int_putget)
 c_test(bool_putget)
 c_test(data_putget)
+c_test(default_putunput)

test/default_putunput.c

@@ -0,0 +1,91 @@
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+#include <arpa2/quick-der.h>
+
+
+dercursor abba = {
+	.derptr = "ABBA",
+	.derlen = 4
+};
+
+dercursor ledz = {
+	.derptr = "LED Zeppelin",
+	.derlen = 12
+};
+
+dercursor ledy = {
+	.derptr = "LED Zeppelinny",
+	.derlen = 12
+};
+
+dercursor null = {
+	.derptr = NULL,
+	.derlen = 0
+};
+
+dercursor band;
+
+
+int errors = 0;
+
+
+void maybe (dercursor dflt) {
+	der_put_default (&band, dflt);
+}
+
+
+void notbe (dercursor dflt) {
+	der_unput_default (&band, dflt);
+}
+
+
+void should (dercursor target) {
+	static int testnr = 0;
+	if (der_cmp (band, target) != 0) {
+		errors++;
+		fprintf (stderr, "Test #%d failed; found \"%.*s\", expected \"%.*s\"\n",
+			testnr, band.derlen, band.derptr, target.derlen, target.derptr);
+	}
+	testnr++;
+}
+
+
+int main (int argc, char *argv []) {
+	errors = 0;
+	band = null;
+	should (null);
+	maybe (abba);
+	should (abba);
+	maybe (abba);
+	should (abba);
+	maybe (ledz);
+	should (abba);
+	notbe (ledz);
+	should (abba);
+	notbe (abba);
+	should (null);
+	maybe (ledz);
+	should (ledz);
+	should (ledy);
+	notbe (ledy);
+	should (null);
+	maybe (ledy);
+	should (ledy);
+	should (ledz);
+	maybe (abba);
+	should (ledy);
+	should (ledz);
+	maybe (ledz);
+	should (ledy);
+	should (ledz);
+	maybe (null);
+	should (ledz);
+	should (ledy);
+	notbe (ledz);
+	should (null);
+	exit (errors);
+}