openpgp-ffi: Add example.

2 files changed, 40 insertions, 1 deletions

diff --git a/openpgp-ffi/examples/Makefile b/openpgp-ffi/examples/Makefile
index 7986d7d6..35c4e9e8 100644
--- a/openpgp-ffi/examples/Makefile
+++ b/openpgp-ffi/examples/Makefile
@@ -8,7 +8,10 @@ CARGO_TARGET_DIR	:= $(abspath $(CARGO_TARGET_DIR))
 # We are producing binaries here.
 EXAMPLE_TARGET_DIR      ?= $(CARGO_TARGET_DIR)/debug/c-examples/openpgp-ffi
 
-EXAMPLES = example reader parser encrypt-for armor type-safety-demo use-after-free-demo
+EXAMPLES = \
+	example reader parser encrypt-for armor \
+	type-safety-demo use-after-free-demo immutable-reference-demo \
+
 CFLAGS  = -I../include -O0 -g -Wall -Werror
 LDFLAGS = -L$(CARGO_TARGET_DIR)/debug -lsequoia_openpgp_ffi
 
diff --git a/openpgp-ffi/examples/immutable-reference-demo.c b/openpgp-ffi/examples/immutable-reference-demo.c
new file mode 100644
index 00000000..a0ada27b
--- /dev/null
+++ b/openpgp-ffi/examples/immutable-reference-demo.c
@@ -0,0 +1,36 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <error.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <sequoia/openpgp.h>
+
+int
+main (int argc, char **argv)
+{
+  /* Create a new TSK.  */
+  pgp_tsk_t tsk;
+  pgp_signature_t revocation;
+  pgp_tsk_new (NULL, "", &tsk, &revocation);
+  pgp_signature_free (revocation);
+
+  /* Let's borrow a immutable reference from it.  */
+  pgp_tpk_t tpk = pgp_tsk_tpk (tsk);
+
+  /* Let's violate The Rules and forge a mutable reference from
+   * the immutable one!  */
+  pgp_tpk_t tpk_mut = (pgp_tpk_t) tpk;
+
+  /* And try to convert the TPK to a TSK, moving the ownership!  */
+  pgp_tpk_into_tsk (tpk_mut);
+
+  /* Always clean up though.  */
+  pgp_tsk_free (tsk);
+  return 0;
+}