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Commit 22748f9d authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

libceph: add start en/decoding block helpers 



Add ceph_start_encoding() and ceph_start_decoding(), the equivalent of
ENCODE_START and DECODE_START in the userspace ceph code.

This is based on a patch from Mike Christie <michaelc@cs.wisc.edu>.

Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 281dbe5d

include/linux/ceph/decode.h

+54 −0
Original line number Diff line number Diff line
@@ -218,6 +218,60 @@ static inline void ceph_encode_string(void **p, void *end, 
	*p += len;

}



/*

 * version and length starting block encoders/decoders

 */



/* current code version (u8) + compat code version (u8) + len of struct (u32) */

#define CEPH_ENCODING_START_BLK_LEN 6



/**

 * ceph_start_encoding - start encoding block

 * @struct_v: current (code) version of the encoding

 * @struct_compat: oldest code version that can decode it

 * @struct_len: length of struct encoding

 */

static inline void ceph_start_encoding(void **p, u8 struct_v, u8 struct_compat,

				       u32 struct_len)

{

	ceph_encode_8(p, struct_v);

	ceph_encode_8(p, struct_compat);

	ceph_encode_32(p, struct_len);

}



/**

 * ceph_start_decoding - start decoding block

 * @v: current version of the encoding that the code supports

 * @name: name of the struct (free-form)

 * @struct_v: out param for the encoding version

 * @struct_len: out param for the length of struct encoding

 *

 * Validates the length of struct encoding, so unsafe ceph_decode_*

 * variants can be used for decoding.

 */

static inline int ceph_start_decoding(void **p, void *end, u8 v,

				      const char *name, u8 *struct_v,

				      u32 *struct_len)

{

	u8 struct_compat;



	ceph_decode_need(p, end, CEPH_ENCODING_START_BLK_LEN, bad);

	*struct_v = ceph_decode_8(p);

	struct_compat = ceph_decode_8(p);

	if (v < struct_compat) {

		pr_warn("got struct_v %d struct_compat %d > %d of %s\n",

			*struct_v, struct_compat, v, name);

		return -EINVAL;

	}



	*struct_len = ceph_decode_32(p);

	ceph_decode_need(p, end, *struct_len, bad);

	return 0;



bad:

	return -ERANGE;

}



#define ceph_encode_need(p, end, n, bad)			\

	do {							\

		if (!likely(ceph_has_room(p, end, n)))		\