Commit 1578e70e authored by Benjamin Lindqvist's avatar Benjamin Lindqvist Committed by Jukka Rissanen
Browse files

net: lwm2m: Add path generation macro 



Currently, the Zephyr LwM2M code base is littered with hard-coded
object- and resource IDs, such as

    /* Mark 1st instance of security object as a bootstrap server */
    lwm2m_engine_set_u8("0/0/1", 1);

The purpose of this LoC is extremely opaque without the accompanying
comment. Each use of a resource path requires constantly checking
headers or the object registry to ensure you're not misremembering IDs.

To alleviate this, this commit introduces a variadic LwM2M path
expansion macro which performs preprocessor stringification on each
argument. For instance, "0/0/1" can now be written as

    LWM2M_PATH(LWM2M_OBJECT_SECURITY_ID, 0, SECURITY_BOOTSTRAP_FLAG_ID)

which, while albeit lengthier, avoids the use of hard-coded string
literals, thus making the code much more immediately understandable.

Signed-off-by: default avatarBenjamin Lindqvist <benjamin.lindqvist@endian.se>
parent daa783ae

include/net/lwm2m.h

+1 −0
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@@ -26,6 +26,7 @@ 
#include <kernel.h>

#include <sys/mutex.h>

#include <net/coap.h>

#include <net/lwm2m_path.h>



/**

 * @brief LwM2M Objects managed by OMA for LwM2M tech specification.  Objects

include/net/lwm2m_path.h

0 → 100644
+46 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2020 Endian Technologies AB

 *

 * SPDX-License-Identifier: Apache-2.0

 */



#ifndef ZEPHYR_INCLUDE_NET_LWM2M_PATH_H_

#define ZEPHYR_INCLUDE_NET_LWM2M_PATH_H_



/**

 * @brief Generate LwM2M string paths using numeric components.

 *

 * Accepts at least one and up to four arguments. Each argument will be

 * stringified by the pre-processor, so calling this with non-literals will

 * likely not do what you want. For example,

 *

 *      #define MY_OBJ_ID 3

 *      LWM2M_PATH(MY_OBJ_ID, 0, 1)

 *

 * would evaluate to "3/0/1", while

 *

 *   int x = 3;

 *   LWM2M_PATH(x, 0, 1)

 *

 * evalutes to "x/0/1".

 */

#define LWM2M_PATH(...) \

	LWM2M_PATH_MACRO(__VA_ARGS__, LWM2M_PATH4, LWM2M_PATH3,	\

			 LWM2M_PATH2, LWM2M_PATH1)(__VA_ARGS__)





/* Internal helper macros for the LWM2M_PATH macro */

#define LWM2M_PATH_VA_NUM_ARGS(...) \

	LWM2M_PATH_VA_NUM_ARGS_IMPL(__VA_ARGS__, 5, 4, 3, 2, 1)

#define LWM2M_PATH_VA_NUM_ARGS_IMPL(_1, _2, _3, _4, N, ...) N



#define LWM2M_PATH1(_x) #_x

#define LWM2M_PATH2(_x, _y) #_x "/" #_y

#define LWM2M_PATH3(_x, _y, _z) #_x "/" #_y "/" #_z

#define LWM2M_PATH4(_a, _x, _y, _z) #_a "/" #_x "/" #_y "/" #_z



#define LWM2M_PATH_MACRO(_1, _2, _3, _4, NAME, ...) NAME







#endif /* ZEPHYR_INCLUDE_NET_LWM2M_PATH_H_ */

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