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@xxxxxxxxxxx>
---
v4: Last final version. Caller can now distinguish between the two
error conditions.
v3: Final version. Sage convinced me that there was no need for
ceph_decode_string() other than its use in this function, so
now this implements what that function had been doing directly.
v2: Made the function safe from overrunning the source memory, and
and added a gfp argument to pass to kmalloc().
include/linux/ceph/decode.h | 47
+++++++++++++++++++++++++++++++++++++++++++
1 files changed, 47 insertions(+), 0 deletions(-)
diff --git a/include/linux/ceph/decode.h b/include/linux/ceph/decode.h
index bcbd66c..4bbf2db 100644
--- a/include/linux/ceph/decode.h
+++ b/include/linux/ceph/decode.h
@@ -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>
@@ -85,6 +86,52 @@ static inline int ceph_has_room(void **p, void *end,
size_t 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
*/
static inline void ceph_decode_timespec(struct timespec *ts,
--
1.7.5.4
--
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