libosmo-gtlv: add C code generator for IE structs and arrays

Defining a protocol of message types with lists of IEs bears a lot of
repetitive, copy-paste-error-prone writing out of data structures.
Add a third layer to libosmo-gtlv, which allows helpful code generation.

By non-repetitive data structures that briefly describe the protocol's
messages and IEs, generate possibly repetitive IE list arrays and
decoded-struct definitions automatically, avoiding grunt work errors.

I tried C macros for this at first, but it became too convoluted.
Generating C code that can be read and grepped makes things easier.

A usage example is found in tests/libosmo-gtlv/test_gtlv_gen/.

Related: SYS#5599
Change-Id: Ifb3ea54d2797ce060b95834aa117725ec2d6c4cf

1 files changed, 261 insertions, 0 deletions

diff --git a/tests/libosmo-gtlv/test_gtlv_gen/gtlv_gen_test.c b/tests/libosmo-gtlv/test_gtlv_gen/gtlv_gen_test.c
new file mode 100644
index 0000000..ef5372c
--- /dev/null
+++ b/tests/libosmo-gtlv/test_gtlv_gen/gtlv_gen_test.c
@@ -0,0 +1,261 @@
+/*
+ * (C) 2021-2022 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved.
+ *
+ * Author: Neels Janosch Hofmeyr <nhofmeyr@sysmocom.de>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <stdio.h>
+#include <errno.h>
+
+#include <osmocom/core/application.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/msgb.h>
+
+#include <osmocom/gtlv/gtlv.h>
+
+#include <myproto_ies_auto.h>
+
+struct myproto_msg {
+	enum myproto_msg_type type;
+	union myproto_ies ies;
+};
+
+static void err_cb(void *data, void *decoded_struct, const char *file, int line, const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	//printf("ERR: %s:%d ", file, line);
+	printf("ERR: ");
+	vprintf(fmt, args);
+	va_end(args);
+}
+
+static int myproto_msg_enc(struct msgb *dst, const struct myproto_msg *msg, const struct osmo_gtlv_cfg *cfg)
+{
+	struct osmo_gtlv_put gtlv = {
+		.cfg = cfg,
+		.dst = dst,
+	};
+
+	msgb_put_u8(gtlv.dst, msg->type);
+	return myproto_ies_encode(&gtlv, (void *)&msg->ies, msg->type, err_cb, NULL, myproto_iei_names);
+}
+
+static int myproto_msg_dec(struct myproto_msg *msg, const uint8_t *data, size_t data_len,
+			   const struct osmo_gtlv_cfg *cfg, bool ordered)
+{
+	struct osmo_gtlv_load gtlv;
+	if (data_len < 1)
+		return -EINVAL;
+	msg->type = data[0];
+	gtlv = (struct osmo_gtlv_load){
+		.cfg = cfg,
+		.src = { data + 1, data_len - 1 },
+	};
+	return myproto_ies_decode(&msg->ies, &gtlv, ordered, msg->type, err_cb, NULL, myproto_iei_names);
+}
+
+void *ctx;
+
+struct myproto_msg tests[] = {
+	{
+		MYPROTO_MSGT_MOO,
+		{
+			.moo = {
+				.foo = 23,
+				.bar = { "twentythree" },
+			},
+		},
+	},
+	{
+		MYPROTO_MSGT_MOO,
+		{
+			.moo = {
+				.foo = 23,
+				.bar = { "twentythree" },
+
+				.baz_present = true,
+				.baz = {
+					.v_int = 2323,
+					.v_bool = true,
+				},
+			},
+		},
+	},
+	{
+		MYPROTO_MSGT_MOO,
+		{
+			.moo = {
+				.foo = 23,
+				.bar = { "twentythree" },
+
+				.baz_present = true,
+				.baz = {
+					.v_int = 2323,
+					.v_bool = true,
+				},
+
+				.repeat_int_count = 3,
+				.repeat_int = { 1, 2, 0x7fff },
+			},
+		},
+	},
+	{
+		MYPROTO_MSGT_MOO,
+		{
+			.moo = {
+				.foo = 23,
+				.bar = { "twentythree" },
+
+				.baz_present = true,
+				.baz = {
+					.v_int = 2323,
+					.v_bool = true,
+				},
+
+				.repeat_int_count = 3,
+				.repeat_int = { 1, 2, 0x7fff },
+
+				.repeat_struct_count = 2,
+				.repeat_struct = {
+					{
+						.v_int = 1001,
+						.v_bool = true,
+						.v_enum = R_A,
+					},
+					{
+						.v_int = 1002,
+						.v_bool = false,
+						.v_enum = R_B,
+					},
+				},
+
+				.nest_present = true,
+				.nest = {
+					.foo = 42,
+					.bar = { "fortytwo" },
+					.baz = {
+						.v_int = 4242,
+						.v_bool = false,
+					},
+				},
+			},
+		},
+	},
+	{
+		MYPROTO_MSGT_GOO,
+		{
+			.goo = {
+				.foo = 17,
+
+				.bar_present = true,
+				.bar = { "gooei" },
+
+				.nest_count = 2,
+				.nest = {
+					{
+						.val_present = true,
+						.val = 0x0123456789abcdef,
+						.nest = {
+							.foo = 11,
+							.bar = { "eleven" },
+							.baz = {
+								.v_int = 1111,
+								.v_bool = true,
+							},
+						},
+					},
+					{
+						.val_present = false,
+						.nest = {
+							.foo = 12,
+							.bar = { "twelve" },
+							.baz = {
+								.v_int = 1212,
+								.v_bool = false,
+							},
+						},
+					},
+				},
+			},
+		},
+	},
+};
+
+int myproto_msg_to_str_buf(char *buf, size_t buflen, const struct myproto_msg *m)
+{
+	struct osmo_strbuf sb = { .buf = buf, .len = buflen };
+	OSMO_STRBUF_PRINTF(sb, "%s={", get_value_string(myproto_msg_type_names, m->type));
+	OSMO_STRBUF_APPEND(sb, osmo_gtlvs_encode_to_str_buf, &m->ies, 0, myproto_get_msg_coding(m->type),
+			   myproto_iei_names);
+	OSMO_STRBUF_PRINTF(sb, " }");
+	return sb.chars_needed;
+
+}
+
+char *myproto_msg_to_str(const struct myproto_msg *m)
+{
+	OSMO_NAME_C_IMPL(ctx, 256, "ERROR", myproto_msg_to_str_buf, m)
+}
+
+void test_enc_dec(const char *label, const struct osmo_gtlv_cfg *cfg, bool ordered)
+{
+	int i;
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
+		int rc;
+		const struct myproto_msg *orig = &tests[i];
+		struct myproto_msg parsed = {};
+		struct msgb *msg;
+
+		printf("\n=== start %s %s[%d]\n", label, __func__, i);
+		printf("encoded: %s\n", myproto_msg_to_str(orig));
+
+		msg = msgb_alloc(1024, __func__);
+		rc = myproto_msg_enc(msg, orig, cfg);
+		printf("myproto_msg_enc() rc = %d\n", rc);
+		printf("%s.\n", osmo_hexdump(msg->data, msg->len));
+
+		rc = myproto_msg_dec(&parsed, msg->data, msg->len, cfg, ordered);
+		printf("myproto_msg_dec() rc = %d\n", rc);
+		printf("decoded: %s\n", myproto_msg_to_str(&parsed));
+		if (strcmp(myproto_msg_to_str(orig), myproto_msg_to_str(&parsed))) {
+			printf(" ERROR: parsed != orig\n");
+			exit(1);
+		}
+
+		msgb_free(msg);
+		printf("=== end %s %s[%d]\n", label, __func__, i);
+	}
+}
+
+int main()
+{
+	ctx = talloc_named_const(NULL, 0, "test_gen_tlv");
+	msgb_talloc_ctx_init(ctx, 0);
+
+	test_enc_dec("t8l8v ordered", &osmo_t8l8v_cfg, true);
+	test_enc_dec("t8l8v unordered", &osmo_t8l8v_cfg, false);
+
+	test_enc_dec("t16l16v ordered", &osmo_t16l16v_cfg, true);
+	test_enc_dec("t16l16v unordered", &osmo_t16l16v_cfg, false);
+
+	talloc_free(ctx);
+	return 0;
+}