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