46 lines
3.0 KiB
XML
Executable File
46 lines
3.0 KiB
XML
Executable File
<chapter id="ljp.csp.versions">
|
|
<title>Protocol Versions</title>
|
|
<para>
|
|
The LiveJournal protocol (so far) has been more or less static; while new
|
|
modes have been added, the basic operation has not changed much. However,
|
|
recent introduction of Unicode support in LiveJournal necessitated changes
|
|
in the way text is encoded in protocol requests and responses. In order to
|
|
allow new clients to take advantage of Unicode support and at the same time
|
|
avoid breaking existing clients, a versioning scheme has been put into the
|
|
protocol. The client sends the number of the highest protocol version it
|
|
supports in every request, inside a <varname>ver</varname> attribute; version
|
|
<literal>0</literal> is implicit if the client does not send the
|
|
<varname>ver</varname> attribute. Currently there are two versions of the
|
|
protocol, and the Unicode-enabled server code supports both of them.
|
|
</para>
|
|
<itemizedlist>
|
|
<listitem><formalpara><title>Version <literal>0</literal></title>
|
|
<para>
|
|
If a client does not send a <varname>ver</varname> key on a request,
|
|
it assumed to support protocol Version <literal>0</literal>. In protocol
|
|
Version <literal>0</literal>, textual information transmitted from or to
|
|
the server is always assumed to be a stream of 8-bit bytes, not necessarily
|
|
<abbrev>ASCII</abbrev>, but without any guarantee that the
|
|
non-<abbrev>ASCII</abbrev> bytes are presented in any particular encoding.
|
|
</para></formalpara></listitem>
|
|
<listitem><formalpara><title>Version <literal>1</literal></title>
|
|
<para>
|
|
Version <literal>1</literal> differs from Version <literal>0</literal> only
|
|
by imposing additional requirements on the text transmitted through requests
|
|
and responses; there aren't any changes in protocol modes. The additional
|
|
requirements are that in a Version <literal>1</literal> request, the client
|
|
<emphasis>must</emphasis> transmit all textual information as a stream of
|
|
Unicode data encoded in <abbrev>UTF-8</abbrev>; the server <emphasis>must</emphasis>
|
|
respond to Version <literal>1</literal> requests with Version <literal>1</literal>
|
|
responses; in such Version <literal>1</literal> responses, the server
|
|
<emphasis>must</emphasis> also transmit all textual information encoded in
|
|
<abbrev>UTF-8</abbrev>; and the client <emphasis>must</emphasis> expect that
|
|
and handle such responses correctly. In other words, all information transmitted
|
|
via protocol when Version <literal>1</literal> is used is always encoded in
|
|
<abbrev>UTF-8</abbrev>. <abbrev>UTF-8</abbrev> is a representation of Unicode
|
|
in a bytestream format compatible with <abbrev>ASCII</abbrev>.
|
|
<footnote id="unicode"><para>See the <ulink url="http://www.unicode.org/">Unicode Consortium website</ulink>
|
|
for more information on Unicode and <abbrev>UTF-8</abbrev>.</para></footnote>
|
|
</para></formalpara></listitem>
|
|
</itemizedlist>
|
|
</chapter> |