File: psgml-api.info, Node: Top, Next: Types, Prev: (dir), Up: (dir)
PSGML Internals
***************
* Menu:
* Types:: Types and operations
* Hooks:: Hooks
* Implementation:: Implementation notes
* Index:: Index
--- The Detailed Node Listing ---
Types and operations
* element:: The element structure
* attribute:: Attribute Types
* parser state:: Parser state
* DTD:: DTD
* entities:: Entities
File: psgml-api.info, Node: Types, Next: Hooks, Prev: Top, Up: Top
Types and operations
********************
NOTE: Names of element types, attributes and entities should be
treated as far as possible as a real type. In versions prior to 1.0
names are represented by lisp symbols but in 1.0 they are strings.
Perhaps I should make a `psgml-api.el' that defines some functions
to deal with names. Then it would be possible to write code that works
in both 0.4 and 1.0.
* Menu:
* element:: The element structure
* attribute:: Attribute Types
* parser state:: Parser state
* DTD:: DTD
* entities:: Entities
File: psgml-api.info, Node: element, Next: attribute, Prev: Types, Up: Types
The element structure
=====================
- Data type: element
The basic data type representing the element structure is the
Element (this happens to be a node in the parse tree).
Mapping buffer positions to elements
------------------------------------
- Function: sgml-find-context-of pos
Return the element current at buffer position POS. If POS is in
markup, `sgml-markup-type' will be a symbol identifying the markup
type. It will be `nil' if POS is outside markup.
- Function: sgml-find-element-of pos
Return the element containing the character at buffer position POS.
Functions operating on elements
-------------------------------
- Function: sgml-element-name element
Returns the name of the element. (obsolete)
- Function: sgml-element-gi element
Return the general identifier (string) of ELEMENT.
- Function: sgml-element-level element
Returns the level of ELEMENT in the element structure. The
document element is level 1.
Structure
.........
- Function: sgml-top-element
Return the document element.
- Function: sgml-off-top-p element
True if ELEMENT is the pseudo element above the document element.
These functions return other related elements, or possibly `nil'.
- Function: sgml-element-content element
First element in content of ELEMENT, or nil.
- Function: sgml-element-next element
Next sibling of ELEMENT. To loop thru all sub elements of an
element, `el', You could do like this:
(let ((c (sgml-element-content el)))
(while c
<<Do something with c>>
(setq c (sgml-element-next c))))
- Function: sgml-element-parent element
Parent of ELEMENT.
Tags
....
- Function: sgml-element-stag-optional element
Return true if the start-tag of ELEMENT is omissible.
- Function: sgml-element-etag-optional element
Return true if the end-tag of ELEMENT is omissible.
- Function: sgml-element-stag-len element
Return the length of the start-tag of ELEMENT. If the start-tag
has been omitted the length is 0.
- Function: sgml-element-etag-len element
Return the length of the end-tag of ELEMENT. If the end-tag has
been omitted the length is 0.
- Function: sgml-element-net-enabled element
Return true, if ELEMENT or some parent of the element has null end
tag (NET) enabled. Return `t', if it is ELEMENT that has NET
enabled.
Positions
.........
These functions relates an element to positions in the buffer.
- Function: sgml-element-start element
Position of start of ELEMENT.
- Function: sgml-element-end element
Position after ELEMENT.
- Function: sgml-element-stag-end element
Position after start-tag of ELEMENT.
- Function: sgml-element-etag-start element
Position before end-tag of ELEMENT.
Attributes
..........
- Function: sgml-element-attlist element
Return the attribute declaration list for ELEMENT.
- Function: sgml-element-attribute-specification-list element
Return the attribute specification list for ELEMENT.
- Function: sgml-element-attval element attribute
Return the value of the ATTRIBUTE in ELEMENT, string or nil.
Misc technical
..............
- Function: sgml-element-data-p element
True if ELEMENT can contain data characters.
- Function: sgml-element-mixed element
True if ELEMENT has mixed content.
- Function: sgml-element-eltype element
- Function: sgml-element-empty element
True if ELEMENT is empty.
- Function: sgml-element-excludes element
- Function: sgml-element-includes element
- Function: sgml-element-model element
Declared content or content model of ELEMENT.
- Function: sgml-element-context-string element
Return string describing context of ELEMENT.
File: psgml-api.info, Node: attribute, Next: parser state, Prev: element, Up: Types
Attribute Types
===============
Basic types for attributes are names and values. (See note about
names in *Note Types::.) And attribute values (attval) by lisp strings.
Attribute Declaration List Type
-------------------------------
- Data type: attlist attdecl*
This is the result of the ATTLIST declarations in the DTD. All
attribute declarations for an element is the elements attlist.
- Function: sgml-lookup-attdecl name attlist
Return attribute declaration (attdecl) for attribute NAME in
attribute declaration list ATTLIST.
- Function: sgml-attribute-with-declared-value attlist declared-value
Find the first attribute in ATTLIST that has DECLARED-VALUE.
Attribute Declaration Type
--------------------------
- Data type: attdecl name declared-value default-value
This is the representation of an individual attribute declaration
contained in an ATTLIST declaration.
- Function: sgml-make-attdecl name declared-value default-value
Produces an attdecl.
- Function: sgml-attdecl-name attdecl
Returns the name of an attribute declaration.
- Function: sgml-attdecl-declared-value attdecl
Returns the declared-value of attribute declaration ATTDECL.
- Function: sgml-attdecl-default-value: attdecl
Returns the default-value of attribute declaration ATTDECL.
Declared Value Type
-------------------
- Data type: declared-value (token-group | notation | simple)
A declared value of an SGML attribute can be of different kinds.
If the declared value is a token group there is an associated list
of name tokens. For notation there is also a list of associated
names, the allowed notation names. The other declared values are
represented by the type name as a lisp symbol.
- Function: sgml-declared-value-token-group declared-value
Return the name token group for the DECLARED-VALUE. This applies
to name token groups. For other declared values nil is returned.
- Function: sgml-declared-value-notation declared-value
Return the list of notation names for the DECLARED-VALUE. This
applies to notation declared value. For other declared values nil
is returned.
Default Value Type
------------------
- Data type: default-value (required | implied | conref | specified )
There are several kinds of default values. The REQUIRED, IMPLIED,
and CONREF has no associated information. The SPECIFIED have an
associated attribute value and can be either `fixed' or `normal'.
- Function: sgml-make-default-value type &optional attval
- Function: sgml-default-value-attval default-value
Return the actual default value of the declared DEFAULT-VALUE.
The actual value is a string. Return `nil' if no actual value.
- Function: sgml-default-value-type-p type default-value
Return true if DEFAULT-VALUE is of TYPE. Where TYPE is a symbol,
one of `required', `implied', `conref', or `fixed'.
Attribute Specification Type
----------------------------
- Data type: attspec name attval
This is the result of parsing an attribute specification.
- Function: sgml-make-attspec name attval
Create an attspec from NAME and ATTVAL. Special case, if ATTVAL
is `nil' this is an implied attribute.
- Function: sgml-attspec-name attspec
Return the name of the attribute specified by ATTSPEC.
- Function: sgml-attspec-attval attspec
Return the value (attval) of attribute specification ATTSPEC. If
ATTSPEC is `nil', `nil' is returned.
Attribute Specification List Type
---------------------------------
- Data type: asl attspec*
This is the result of parsing an attribute specification list.
- Function: sgml-lookup-attspec name asl
Return the attribute specification for attribute with NAME in the
attribute specification list ASL. If the attribute is unspecified
`nil' is returned.
File: psgml-api.info, Node: parser state, Next: DTD, Prev: attribute, Up: Types
Parser state
============
The state of the parser that needs to be kept between commands are
stored in a buffer local variable. Some global variables are
initialised from this variable when parsing starts.
- Variable: sgml-buffer-parse-state
The state of the parser that is kept between commands. The value
of this variable is of type pstate.
- Data type: pstate
The parser state.
- Function: sgml-pstate-dtd pstate
The document type information (dtd) for the parser.
File: psgml-api.info, Node: DTD, Next: entities, Prev: parser state, Up: Types
DTD
===
- Data type: dtd
Represents what PSGML knows about the DTD.
- Function: sgml-dtd-doctype dtd
The document type name.
- Function: sgml-dtd-eltypes dtd
The table of element types.
- Function: sgml-dtd-entities dtd
The table of declared general entities (entity-table).
- Function: sgml-dtd-parameters dtd
The table of declared parameter entities (entity-table).
- Function: sgml-dtd-shortmaps dtd
The list of short reference maps.
- Function: sgml-dtd-notations dtd
Not yet implemented.
File: psgml-api.info, Node: entities, Prev: DTD, Up: Types
Entities
========
- Data type: entity
An entity has the following properties:
NAME
The name of the entity (a string). This is either the name
of a declared entity (general or parameter) or the doctype
name if it is the implicit entity referred to by the doctype
declaration.
TYPE
This is a symbol. It is `text' if it is a text entity, other
values are `cdata', `ndata', `sdata', `sgml' or `dtd'.
TEXT
This is the text of the entity, either a string or an external
identifier.
Operations on entities
- Function: sgml-make-entity name type text
Create an entity.
- Function: sgml-entity-name entity
The name of the entity.
- Function: sgml-entity-type entity
The type of the entity.
- Function: sgml-entity-text entity
The text of the entity.
- Function: sgml-entity-insert-text entity
Insert the text of the entity into the current buffer at point.
- Function: sgml-entity-data-p entity
True if ENTITY is a data entity, that is not of type `text'.
- Data type: entity-table
A table of entities that can be referenced by entity name.
- Function: sgml-lookup-entity name entity-table
The entity with named NAME in the table ENTITY-TABLE. If no such
entity exists, `nil' is returned.
- Function: sgml-entity-declare name entity-table type text
Create an entity from NAME, TYPE and TEXT; and enter the entity
into the table ENTITY-TABLE.
- Function: sgml-entity-completion-table entity-table
Make a completion table from the ENTITY-TABLE.
- Function: sgml-map-entities fn entity-table &optional collect
Apply the function FN to all entities in ENTITY-TABLE. If COLLECT
is `t', the results of the applications are collected in a list
and returned.
File: psgml-api.info, Node: Hooks, Next: Implementation, Prev: Types, Up: Top
Hooks
*****
- Variable: sgml-open-element-hook
The hook run by `sgml-open-element'. Theses functions are called
with two arguments, the first argument is the opened element and
the second argument is the attribute specification list. It is
probably best not to refer to the content or the end-tag of the
element.
- Variable: sgml-close-element-hook
The hook run by `sgml-close-element'. These functions are invoked
with `sgml-current-tree' bound to the element just parsed.
- Variable: sgml-doctype-parsed-hook
This hook is called after the doctype has been parsed. It can be
used to load any additional information into the DTD structure.
- Variable: sgml-sysid-resolve-functions
This variable should contain a list of functions. Each function
should take one argument, the system identifier of an entity. If
the function can handle that identifier, it should insert the text
of the entity into the current buffer at point and return t. If
the system identifier is not handled the function should return
nil.
- Variable: sgml-doctype-parsed-hook
This hook is caled after the doctype has been parsed. It can be
used to load any additional information into the DTD structure.
- Variable: sgml-close-element-hook
The hook run by `sgml-close-element'. These functions are invoked
with `sgml-current-tree' bound to the element just parsed.
*** sgml-new-attribute-list-function This hook is run when a new
element is inserted to construct the attribute specification list. The
default function prompts for the required attributes.
File: psgml-api.info, Node: Implementation, Next: Index, Prev: Hooks, Up: Top
Implementation notes
********************
Data Types and Operations
=========================
Element Type
------------
- Data type: eltype
Data type representing the information about an element type. An
`eltype' has information from `ELEMENT' and `ATTLIST'
declarations. It can also store data for the application.
The element types are symbols in a special oblist. The oblist is the
table of element types. The symbols name is the GI, its value is used
to store three flags and the function definition holds the content
model. Other information about the element type is stored on the
property list.
- Function: sgml-eltype-name et
The name (a string) of the element type ET.
- Function: sgml-eltype-appdata et prop
Get application data from element type ET with name PROP. PROP
should be a symbol, reserved names are: flags, model, attlist,
includes, excludes, conref-regexp, mixed, stag-optional,
etag-optional.
This function can be used as a place in `setf', `push' and other
functions from the CL library.
- Function: sgml-eltype-all-miscdata eltype
A list of all data properties for eltype except for flags, model,
includes and excludes. This function filters the property list of
ELTYPE. Used when saving the parsed DTD.
- Function: sgml-eltype-set-all-miscdata eltype miscdata
Append the MISCDATA data properties to the properties of ELTYPE.
- Function: sgml-eltype-attlist et
The attribute specification list for the element type ET.
- Function: sgml-eltype-completion-table eltypes
Make a completion table from a list, ELTYPES, of element types.
- Function: sgml-eltype-stag-optional et
True if the element type ET has optional start-tag.
- Function: sgml-eltype-etag-optional et
True if the element type ET has optional end-tag.
- Function: sgml-eltype-excludes et
The list of excluded element types for element type ET.
- Function: sgml-eltype-includes et
The list of included element types for element type ET.
- Function: sgml-eltype-flags et
Contains three flags as a number. The flags are stag-optional,
etag-optional and mixed.
- Function: sgml-eltype-mixed et
True if element type ET has mixed content.
- Function: sgml-eltype-model et
The content model of element type ET. The content model is either
the start state in the DFA for the content model or a symbol
identifying a declared content.
- Function: sgml-eltype-shortmap et
The name of the shortmap associated with element type ET. This
can also be the symbol `empty' (if declared with a `<!USEMAP gi
#EMPTY>' or `nil' (if no associated map).
- Function: sgml-eltype-token et
Return a token for the element type ET.
- Function: sgml-eltypes-in-state state tree
List of element types valid in STATE and TREE.
DTD
---
The DTD data type is realised as a lisp vector using `defstruct'.
There are two additional fields for internal use: dependencies and
merged.
- Function: sgml-dtd-dependencies dtd
The list of files used to create this DTD.
- Function: sgml-dtd-merged dtd
The pair (FILE . MERGED-DTD), if the DTD has had a precompiled dtd
merged into it. FILE is the file containing the compiled DTD and
MERGED-DTD is the DTD loaded from that file.
Element and Tree
----------------
- Data Type: tree
This is the data type for the nodes in the tree build by the
parser.
The tree nodes are represented as lisp vectors, using `defstruct' to
define basic operations.
The Element data type is a view of the tree built by the parser.
Parsing model
=============
PSGML uses finite state machines and a stack to parse SGML. Every
element type has an associated DFA (deterministic finite automaton).
This DFA is constructed from the content model.
SGML restricts the allowed content models in such a way that it is
easy to directly construct a DFA.
To be able to determine when a start-tag can be omitted the DFA need
to contain some more information than the traditional DFA. In PSGML a
DFA has a set of states and two sets of edges. The edges are associated
with tokens (corresponding to SGML's primitive content tokens). I call
these moves. One set of moves, the "optional moves", represents
optional tokens. I call the other set "required moves". The
correspondence to SGML definitions are: if there is precisely one
required move from one state, then the associated token is required. A
state is final if there is not required move from that state.
The SGML construct `(...&...&...)' ("AND-group") is another problem.
There is a simple translation to sequence- and or-connectors. For
example `(a & b & c)' is can be translated to:
((a, ((c, b) | (b, c))) |
(b, ((a, c) | (c, a))) |
(c, ((a, b) | (b, a))) )
But this grows too fast to be of direct practical use. PSGML
represents an AND-group with one DFA for every (SGML) token in the
group. During parsing of an AND-group there is a pointer to a state in
one of the group's DFAs, and a list of the DFAs for the tokens not yet
satisfied. Most of this is hidden by the primitives for the state
type. The parser only sees states in a DFA and moves.
Entity manager
==============
- Function: sgml-push-to-entity entity &optional ref-start type
Set current buffer to a buffer containing the entity ENTITY.
ENTITY can also be a file name. Optional argument REF-START should
be the start point of the entity reference. Optional argument
TYPE, overrides the entity type in entity look up.
- Function: sgml-pop-entity
Should be called after a `sgml-push-to-entity' (or similar).
Restore the current buffer to the buffer that was current when the
push to this buffer was made.
- Function: sgml-push-to-string string
Create an entity from STRING and push it on the top of the entity
stack. After this the current buffer will be a scratch buffer
containing the text of the new entity with point at the first
character.
Use `sgml-pop-entity' to exit from this buffer.
Parser functions
================
- Function: sgml-need-dtd
This makes sure that the buffer has a DTD and set global variables
needed by parsing routines. One global variable is `sgml-dtd-info'
which contain the DTD (type dtd).
- Function: sgml-parse-to goal &optional extra-cond quiet
This is the low level interface to the parser.
Parse until (at least) GOAL, a buffer position. Optional argument
EXTRA-COND should be a function. This function is called in the
parser loop, and the loop is exited if the function returns t. If
third argument QUIT is non-`nil', no "`Parsing...'" message will
be displayed.
- Function: sgml-reparse-buffer shortref-fun
Reparse the buffer and let SHORTREF-FUN take care of short
references. SHORTREF-FUN is called with the entity as argument
and `sgml-markup-start' pointing to start of short reference and
point pointing to the end.
Saved DTD Format
================
File = Comment,
File version,
S-expression --dependencies--,
Parameter entites,
Document type name,
Elements,
General entities,
S-expression --shortref maps--,
S-expression --notations--
Elements = Counted Sequence of S-expression --element type name--,
Counted Sequence of Element type description
File version = "(sgml-saved-dtd-version 5)
"
Comment = (";",
(CASE
OF [0-9]
OF [11-255])*,
[10] --end of line marker--)*
Element type description = S-expression --Misc info--,
CASE
OF [0-7] --Flags 1:stag-opt, 2:etag-opt, 4:mixed--,
Content specification,
Token list --includes--,
Token list --excludes--
OF [128] --Flag undefined element--
Content specification = CASE
OF [0] --cdata--
OF [1] --rcdata--
OF [2] --empty--
OF [3] --any--
OF [4] --undefined--
OF [128] --model follows--,
Model --nodes in the finite state automaton--
Model = Counted Sequence of Node
Node = CASE
OF Normal State
OF And Node
Normal State = Moves --moves for optional tokens--,
Moves --moves for required tokens--
Moves = Counted Sequence of (Token,
OCTET --state #--)
And Node = [255] --signals an AND node--,
Number --next state (node number)--,
Counted Sequence of Model --set of models--
Token = Number --index in list of elements--
Number = CASE
OF [0-250] --Small number 0--250--
OF [251-255] --Big number, first octet--,
OCTET --Big number, second octet--
Token list = Counted Sequence of Token
Parameter entites = S-expression --internal representation of parameter entities--
General entities = S-expression --internal representation of general entities--
Document type name = S-expression --name of document type as a string--
S-expression = OTHER
Counted Sequence = Number_a --length of sequence--,
(ARG_1)^a
File: psgml-api.info, Node: Index, Prev: Implementation, Up: Top
Index
*****
Types
* Menu:
* asl: attribute.
* attdecl: attribute.
* attlist: attribute.
* attspec: attribute.
* declared-value: attribute.
* default-value: attribute.
* dtd: DTD.
* element: element.
* eltype: Implementation.
* entity: entities.
* entity-table: entities.
* pstate: parser state.
* tree: Implementation.
|