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libceph: define ceph_extract_encoded_string()

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This adds a new utility routine which will return a dynamically-
allocated buffer containing a string that has been decoded from ceph
over-the-wire format.  It also returns the length of the string
if the address of a size variable is supplied to receive it.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
This commit is contained in:
Alex Elder 2012-07-11 08:24:45 -05:00 committed by Sage Weil
parent ad4f232f28
commit f8c36c58ac
1 changed files with 47 additions and 0 deletions
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47
include/linux/ceph/decode.h
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@ -1,6 +1,7 @@
#ifndef __CEPH_DECODE_H
#define __CEPH_DECODE_H
#include <linux/err.h>
#include <linux/bug.h>
#include <linux/time.h>
#include <asm/unaligned.h>
@ -84,6 +85,52 @@ static inline int ceph_has_room(void **p, void *end, size_t n)
ceph_decode_copy(p, pv, n); \
} while (0)
/*
* Allocate a buffer big enough to hold the wire-encoded string, and
* decode the string into it. The resulting string will always be
* terminated with '\0'. If successful, *p will be advanced
* past the decoded data. Also, if lenp is not a null pointer, the
* length (not including the terminating '\0') will be recorded in
* *lenp. Note that a zero-length string is a valid return value.
*
* Returns a pointer to the newly-allocated string buffer, or a
* pointer-coded errno if an error occurs. Neither *p nor *lenp
* will have been updated if an error is returned.
*
* There are two possible failures:
* - converting the string would require accessing memory at or
* beyond the "end" pointer provided (-E
* - memory could not be allocated for the result
*/
static inline char *ceph_extract_encoded_string(void **p, void *end,
size_t *lenp, gfp_t gfp)
{
u32 len;
void *sp = *p;
char *buf;
ceph_decode_32_safe(&sp, end, len, bad);
if (!ceph_has_room(&sp, end, len))
goto bad;
buf = kmalloc(len + 1, gfp);
if (!buf)
return ERR_PTR(-ENOMEM);
if (len)
memcpy(buf, sp, len);
buf[len] = '\0';
*p = (char *) *p + sizeof (u32) + len;
if (lenp)
*lenp = (size_t) len;
return buf;
bad:
return ERR_PTR(-ERANGE);
}
/*
* struct ceph_timespec <-> struct timespec
*/