Merge branch 'master' of ssh://git.ikiwiki.info/srv/git/ikiwiki.info

[ikiwiki.git] / doc / plugins / write / external.mdwn

diff --git a/doc/plugins/write/external.mdwn b/doc/plugins/write/external.mdwn
index 058b9e58a2da357c925dc1507e3d904120a61ba5..272f74a7c9d76d59bb7df14cdfcfd04bcffd0a3b 100644 (file)
--- a/doc/plugins/write/external.mdwn
+++ b/doc/plugins/write/external.mdwn
@@ -1,8 +1,10 @@
 External plugins are standalone, executable programs, that can be written
 in any language. When ikiwiki starts up, it runs the program, and
 External plugins are standalone, executable programs, that can be written
 in any language. When ikiwiki starts up, it runs the program, and

-communicates with it using XML RPC. If you want to [[write]] an external
+communicates with it using [XML RPC][xmlrpc]. If you want to [[write]] an external

 plugin, read on..
 
 plugin, read on..
 

+[xmlrpc]: http://www.xmlrpc.com/
+

 ikiwiki contains one sample external plugin, named `externaldemo`. This is
 written in perl, but is intended to be an example of how to write an
 external plugin in your favorite programming language. Wow us at how much
 ikiwiki contains one sample external plugin, named `externaldemo`. This is
 written in perl, but is intended to be an example of how to write an
 external plugin in your favorite programming language. Wow us at how much


@@ -11,7 +13,7 @@ easier you can do the same thing in your favorite language. ;-)
 There's now a second external plugin, the [[rst]] plugin, written in
 python. It uses a `proxy.py`, a helper library for ikiwiki python plugins.
 
 There's now a second external plugin, the [[rst]] plugin, written in
 python. It uses a `proxy.py`, a helper library for ikiwiki python plugins.
 

-[[toc ]]
+[[!toc ]]

 
 ## How external plugins use XML RPC
 
 
 ## How external plugins use XML RPC
 


@@ -27,7 +29,7 @@ stdin, using XML RPC. Dispatch the command, and return its result to
 stdout, also using XML RPC. After reading a command, and before returning
 the result, the plugin can output XML RPC requests of its own, calling
 functions in ikiwiki. Note: *Never* make an XML RPC request at any other
 stdout, also using XML RPC. After reading a command, and before returning
 the result, the plugin can output XML RPC requests of its own, calling
 functions in ikiwiki. Note: *Never* make an XML RPC request at any other

-time. Ikiwiki won't be listening for it, and you will deadlock.
+time. IkiWiki won't be listening for it, and you will deadlock.

 
 When ikiwiki starts up an external plugin, the first RPC it will make
 is to call the plugin's `import()` function. That function typically makes
 
 When ikiwiki starts up an external plugin, the first RPC it will make
 is to call the plugin's `import()` function. That function typically makes


@@ -42,7 +44,7 @@ supported in ikiwiki version 2.6.
 
 ## Accessing data structures
 
 
 ## Accessing data structures
 

-Ikiwiki has a few global data structures such as `%config`, which holds
+IkiWiki has a few global data structures such as `%config`, which holds

 its configuration. External plugins can use the `getvar` and `setvar` RPCs
 to access any such global hash. To get the "url" configuration value,
 call `getvar("config", "url")`. To set it, call 
 its configuration. External plugins can use the `getvar` and `setvar` RPCs
 to access any such global hash. To get the "url" configuration value,
 call `getvar("config", "url")`. To set it, call 


@@ -54,7 +56,7 @@ stored state, call `getstate("page", "id", "key")`, and to store state,
 call `setstate("page", "id", "key", "value")`.
 
 To access ikiwiki's ARGV array, call `getargv()`. To change its ARGV, call
 call `setstate("page", "id", "key", "value")`.
 
 To access ikiwiki's ARGV array, call `getargv()`. To change its ARGV, call

-`setargv(value)`.
+`setargv(array)`.

 
 ## Notes on function parameters
 
 
 ## Notes on function parameters
 


@@ -79,6 +81,19 @@ Other languages might not find it so easy. If not, it might be a good idea
 to convert these named parameters into something more natural for the
 language as part of their XML RPC interface.
 
 to convert these named parameters into something more natural for the
 language as part of their XML RPC interface.
 

+## undef
+
+XML RPC has a limitation that it does not have a way to pass
+undef/NULL/None. There is an extension to the protocol that supports this,
+but it is not yet available in the [[!cpan XML::RPC]] library used by
+ikiwiki.
+
+Until the extension is available, ikiwiki allows undef to be communicated
+over XML RPC by passing a sentinal value, a hash with a single key "null"
+with a value of an empty string. External plugins that need to communicate
+null values to or from ikiwiki will have to translate between undef and
+the sentinal.
+

 ## Function injection
 
 Some parts of ikiwiki are extensible by adding functions. For example, the
 ## Function injection
 
 Some parts of ikiwiki are extensible by adding functions. For example, the


@@ -119,12 +134,12 @@ large quantity of data conversion going on. In contrast, `preprocess` hooks
 are called generally rarely, and pass around minimal data.
 
 External plugins should avoid making RPC calls unnecessarily (ie, in a loop).
 are called generally rarely, and pass around minimal data.
 
 External plugins should avoid making RPC calls unnecessarily (ie, in a loop).

-Memoizing the results of appropriate RPC calls is one good way to minimise the
+Memoizing the results of appropriate RPC calls is one good way to minimize the

 number of calls.
 
 Injecting a replacement for a commonly called ikiwiki function
 could result in a lot more RPC calls than expected and slow
 number of calls.
 
 Injecting a replacement for a commonly called ikiwiki function
 could result in a lot more RPC calls than expected and slow

-eveything down. `pagetitle`, for instance, is called about 100 times
+everything down. `pagetitle`, for instance, is called about 100 times

 per page build. Whenever possible, you should tell ikiwiki to memoize
 injected functions.
 
 per page build. Whenever possible, you should tell ikiwiki to memoize
 injected functions.