[email protected] wrote on Thu, 03 Sep 2009 13:44 -0400:
> Pete Wyckoff wrote:
> > [email protected] wrote on Thu, 03 Sep 2009 11:51 -0400:
> >> In looking at some issues I was having with the encoding of PVFS_dirent
> >> structs in requests I saw an inconsistency in how here_strings are
> >> encoded and decoded. encode_string memcpys strings starting at *(pptr)+4
> >> unless it's length 0 in which case it sets *(pptr) to 0. However,
> >> decode_here_string always copys from *(pptr) + 4. So, if d_name is an
> >> empty string when encoded d_name gets 1 byte of *(pptr)+4 instead of 0
> >> on decoding.
> >>
> >> The fix is just to handle decoding like encoding. Is there a reason for
> >> always copying to *(pptr)+4 in decode_here_string? Is this something
> >> that should be changed?
> >
> > encode_string always ships at least 8 bytes. For a null string, that's 8
> > bytes of zeroes. Decoding a null "here" string will use one of
> > those zero bytes to set pbuf[0] = '\0'. I figured it would be nice
> > to make sure the string was set to NULL.
> >
>
> I see where 8 bytes are always shipped in encode_string but I'm not
> seeing where 8 bytes of '\0' get encoded for a NULL string or if the
> length of the string is 0.
>
> However, adding an 8 byte memset worth of '\0' to *(pptr) in the else
> (length 0) branch of encode_string also resolves the problem I was
> seeing. So, your point may make for a better solution.
uint8_t *wiredata;
char mystr[20];
decode_here_string(&wiredata, mystr);
wiredata -> 0 0 0 0 0 0 0 0
mystr unititialized
131 memcpy(pbuf, *(pptr) + 4, len + 1); \
memcpy(pbuf, <bunch of zeroes>, 1)
equiv to
pbuf[0] = '\0';
or
mystr[0] = '\0';
right? It's a _here_ string, you don't want to destroy the pointer,
you want to put a zero into it to nullify the string.
The comment does say "odd variation". I don't remember where this
even gets used.
-- Pete
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