NAME¶

Embperl::Syntax - base class for defining custom syntaxes

SYNOPSIS¶

DESCRIPTION¶

Embperl::Syntax provides a base class from which all custom syntaxes should be derived. Currently Embperl comes with the following derived syntaxes:

EmbperlHTML

all the HTML tag that Embperl recognizes by default

EmbperlBlocks

all the [ ] blocks that Embperl supports

Embperl

The default syntax; is derived from "EmbperlHtml" and "EmbperlBlocks"

ASP

<% %> and <%= %>, see perldoc Embperl::Syntax::ASP

SSI

Server Side Includes, see perldoc Embperl::Syntax::SSI

Perl

File contains pure Perl (similar to Apache::Registry), but can be used inside EmbperlObject

Text

File contains only Text, no actions is taken on the Text

Mail

Defines the <mail:send> tag, for sending mail. This is an example for a taglib, which could be a base for writing your own taglib to extent the number of available tags

POD

Parses POD out of any file and creates a XML tree similar to pod2xml, which can be formatted by XSLT afterwards.

You can choose which syntax is used inside your page, either by the "EMBPERL_SYNTAX" configuration directive, the "syntax", parameter to "Execute" or the "[$ syntax $]" metacommand. You can also specify multiple syntaxes e.g.

    PerlSetEnv EMBPERL_SYNTAX "Embperl SSI"
    Execute ({inputfile => '*', syntax => 'Embperl ASP'}) ;

The syntax metacommand allows you to switch the syntax or to add or subtract syntaxes e.g.

    [$ syntax + Mail $]

will add the Mail taglib so the <mail:send> tag is available after this line.

    [$ syntax - Mail $]

now the <mail:send> tag is unknown again

    [$ syntax SSI $]

now you can only use SSI commands inside your page.

Defining your own Syntax¶

If you want to define your own syntax, you have to derive a new class from one of the existing ones and extent it with new tags/functionality. The best thing is to take a look at the syntax classes that comes with Embperl. (inside the directory Embperl/Syntax/). For example if you want to add new html tags, derive from Embperl::Syntax::HTML, if you want to add new metacommands derive from Embperl::Syntax::EmbperlBlocks. Some of the classes define addtionaly methods to easily add new tags. See the respective pod file, which methods are available for a certain class. Embperl::Syntax defines the basic methods to create a syntax:

Methods¶

Embperl::Syntax -> new / $self -> new¶

Create a new syntax class. This method should only be called inside a constructor of a derived class.

$self -> AddToRoot ($elements)¶

This adds a new element to the root of the parser tree. $elements must be a hashref. See Embperl::Syntax::ASP for an example.

$self -> AddInitCode ($compiletimecode, $initcode, $termcode, $procinfo)¶

This gives you the possibility to add some Perl code, that is always executed at the beginning of a document ($initcode), at the end of the document ($termcode) or at compile time ($compiletimecode). The three strings must be valid Perl code. See Embperl::Syntax::SSI for an example. $procinfo is a hashref that can consits of addtional processor infos (see below) for the document.

$self -> GetRoot¶

Returns the root of the parser tree.

Embperl::Syntax::GetSyntax ($name, $oldname)¶

Returns a syntax object which is build form the syntaxes named in $name. If $oldname is given, $name can start with a "+" or "-" to add or subtract a syntax. This is normally only needed by Embperl itself or to implement a syntax switch statement (see Embperl::Syntax::SSI for an example.)

$self -> CloneHash ($old, $replace)¶

Clones a hash which is given as hashref in $old, optional replace the tags given in the hashref $replace and return a hashref to the new hash.

Syntax Structure and Parameter¶

Internaly the syntax object builds a data structure which serve as base for the parser. This structure consists of a list of tokens and options, which starts with a dash:

Tokens¶

'-lsearch' => 1

Do an linear serach instead of a binary search. This is necessary if the tokens can't clearly separated.

'-defnodetype' => ntypText,

Defines the default type for text nodes. Without any specification the type is CDATA, which mean no escaping takes places. With "ntypText" all special characters are escaped.

'-rootnode'

Name for a root node to insert always.

<name> => \%tokendescription

All items which does not start with a slash are treated as names. The name of a token is only descriptive and is used in error messages. The item must contain a hashref which describes the token.

Tokendescription¶

Each token can have the following members:

'text' => '<'

Start text

'end' => '>'

End text

'matchall'

when set to 1 new token starts at next character, when set to -1 new token starts at next character, but only if it is the first token inside another one.

'nodename'

Text that should be outputed when node is stringifyed. Defaults to text. If the first character is a ':' you can specify the sourounding delimiters for this tag with :<start>:<end>:<text>:<endtag>. Example: ':{:}:NAME' . If the nodename starts with a '!' a unique internal id is generated, so two or more nodename of the same text, can have different meaning in different contexts.

'contains' => 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789'

Token consists of the following characters. Either "start" and "end" or "contains" could be specified.

 

NOTE: If a item that only specfifies contains but no text should be compiled, you must specfify a nodname.

'unescape' => 1

If "optRawInput" isn't set unescape the data of the inside the node

'nodetype' => ntypEndTag

Type of the node

'cdatatype' => ntypAttrValue

Type of nodes for data (which is not matched by 'inside' definitions) inside this node. Set to zero to not generate any nodes for text inside of this node, other then these that are matched by a 'inside' definition.

'endtag'

Name of the tag that marks the end of a block. This is used by the parser to track correct nesting.

'follow' => \%tokenlist

Hashref that specifices one or more tokens that must follow this token.

'inside' => \%tokenlist

Hashref that specifices one or more tokens that could occur inside a node that is started with this token.

exitinside

when the token found, the parser stop searching in the current level and continues with the tokens that are defined in the hash from there the current one was "called" via inside

donteat

set to 1 to don't eat the start text, so it will be matched again, by any tokens set under "inside". Set 2 to don't the end text. Set to 3 for both.

'procinfo' =>

Processor info. Hashref with information how to process this token.

Processor info¶

The processor info gives information how to compile this token to valid code that can be executed later on by the processor. There could be information for multiple processors. At the moment only the embperl processor is defined. Normaly you must not worry about different processor, because the syntax object knows inside that all procinfo is for the embperl processor. procinfo is a parameter to many methods, it is a hashref and can take the following items:

perlcode => <string> or <arrayref>

Code to generate. You can also specify a arrayref of strings. The first string which contains matching attributes are used. The following special strings are replaced:

perlcodeend => <string>

Code to generate at the end of the block.

compiletimeperlcode => <string> or <arrayref>

Code that is executed at compile time. You can also specify a arrayref of string. The first string which contains matching attributes are used. The same special strings are replaced as in "perlcode".

 

$_[0] contains the Embperl request object. The method "Code" can be used to get or set the perl code that should be generated by this node.

 

If the code begins with #!- all newlines are removed in the code. This is basically useful to keep all code on the same line, so the line number in error reporting matches the line in the source.

compiletimeperlcodeend => <string>

Code that is executed at compile time, but at the end of the tag. The same special strings are replaced as in "perlcode".

 

$_[0] contains the Embperl request object. The method "Code" can be used to get or set the perl code that should be generated by this node.

 

If the code begins with #!- all newlines are removed in the code. This is basically useful to keep all code on the same line, so the linenumber in error reporting matches the line in the source.

perlcoderemove => 0/1

Remove perlcode if perlcodeend condition is not met.

removenode => <removelevel>

Remove node after compiling. <removelevel> could be one of the following, values could be added:

removespaces => <removeflags>

Remove spaces before or after tag.

mayjump => 0/1

If set, tells the compiler that this code may jump to another program location. (e.g. if, while, goto etc.). Could also be a condition as described under perlcode.

compilechilds => 0/1

Compile child nodes. Default: 1

stackname => <name>

Name of stack for "push", "stackmatch"

stackname2 => <name>

Name of stack for "push2"

push => <value>

Push value on stack which name is given with "stackname". Value could include the same specical values as "perlcode"

push2 => <value>

Push value on stack which name is given with "stackname2". Value could include the same specical values as "perlcode"

stackmatch => <value>

Check if value on stack which name is given with "stackname" is the same as the given value. If not give a error message about tag mismatch. Value could include the same specical values as "perlcode"

switchcodetype => <1/2>

1 means put the following code into normal code which is executed everytime the page is requested

 

2 means put the following code put into code which is executed direct after compilation. This is mainly for defining subs, or using modules etc.

addflags

cdatatype

forcetype

insidemustexist

matchall

exitinside

addfirstchild

starttag

endtag

parsetimeperlcode

contains