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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: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Ilya Dryomov 2016-06-02 14:23:32 +02:00
parent 281dbe5db8
commit 22748f9d61
1 changed files with 54 additions and 0 deletions
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54
include/linux/ceph/decode.h
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@ -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))) \