Wireshark-dev: Re: [Wireshark-dev] Best way to handle a variable-length NULL-terminated string
Separated by. tvb_get_stringz is exactly what I was looking for. Thank you!
On Fri, Apr 30, 2010 at 15:42, Guy Harris <guy@xxxxxxxxxxxx> wrote:
>
> On Apr 30, 2010, at 12:33 PM, Jeremy O'Brien wrote:
>
>> So I have several strings in my protocol, which are separated by
>> NULL's.
>
> Separated by, or terminated by?
>
> I.e., is there a NUL at the end of the *last* string, or just in *between* strings?
>
>> There is no information contained in the packet that gives the
>> length of each string. Is there a better way to add these strings to
>> the protocol dissection besides doing a tvb_get_ephemeral_string() on
>> the section of the tvb in question, searching for the ending NULL's
>> for each string, and manually incrementing the offset for each one?
>> I'm just not sure if wireshark has any convenience functions that
>> would handle this sort of situation.
>
> /**
> * Given a tvbuff and an offset, with the offset assumed to refer to
> * a null-terminated string, find the length of that string (and throw
> * an exception if the tvbuff ends before we find the null), allocate
> * a buffer big enough to hold the string, copy the string into it,
> * and return a pointer to the string. Also return the length of the
> * string (including the terminating null) through a pointer.
> *
> * tvb_get_stringz() returns a string allocated by g_malloc() and therefore
> * MUST be g_free() by the caller in order not to leak
> * memory.
> *
> * tvb_get_ephemeral_stringz() returns a string that does not need to be freed,
> * instead it will automatically be freed once the next
> * packet is dissected.
> *
> * tvb_get_seasonal_stringz() returns a string that does not need to be freed,
> * instead it will automatically be freed when a new capture
> * or file is opened.
> */
> extern guint8 *tvb_get_stringz(tvbuff_t *tvb, const gint offset, gint *lengthp);
> extern guint8 *tvb_get_ephemeral_stringz(tvbuff_t *tvb, const gint offset, gint *lengthp);
> extern guint8 *tvb_get_seasonal_stringz(tvbuff_t *tvb, const gint offset, gint *lengthp);
>
> You presumably want tvb_get_ephemeral_stringz().
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