Re: define string

[Simon Tatham <anakin%pobox.com@localhost>]

Glenn McGrath  <bug1%optushome.com.au@localhost> wrote:
> By trying to talk to openssh and lsh servers i worked out a string is
> 
> char string_length
> char *string
> char extra_terminators[3]
> 
> I understand why string_length is there, its can make it easier to
> handle the string, but why are there three extra '\0' terminators ?
> 
> Irrespective of the reasoning i think the format of the string should be
> documented somewhere

It is. Look in draft-ietf-secsh-architecture-13.txt, which contains
general material which applies to more than one of the transport,
userauth and connect drafts:

string

      Arbitrary length binary string.  Strings are allowed to
      contain arbitrary binary data, including null characters and
      8-bit characters.  They are stored as a uint32 containing its
      length (number of bytes that follow) and zero (= empty string)
      or more bytes that are the value of the string.  Terminating
      null characters are not used.
		  
      Strings are also used to store text.  In that case, US-ASCII
      is used for internal names, and ISO-10646 UTF-8 for text that
      might be displayed to the user.  The terminating null
      character SHOULD NOT normally be stored in the string.

      For example, the US-ASCII string "testing" is represented as
      00 00 00 07 t e s t i n g.  The UTF8 mapping does not alter
      the encoding of US-ASCII characters.

In other words, your `three extra terminators' are actually part of
the 32-bit length field of the _next_ string.

Hope that helps,
Simon
-- 
Simon Tatham         "Thieves respect property; they only wish the property to
<anakin%pobox.com@localhost>    be their own, that they may more properly respect it."