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Xml Light

Xml Light is a minimal Xml parser & printer for OCaml. It provide few functions to parse a basic Xml document into an OCaml data structure and to print back the data structures to an Xml document.

Xml Light has also support for DTD (Document Type Definition).

(c)Copyright 2002-2003 Nicolas Cannasse

Xml Data Structure
type xml = Types.xml =
  1. | Element of string * (string * string) list * xml list
  2. | PCData of string

An Xml node is either Element (tag-name, attributes, children) or PCData text

Xml Parsing

For easily parsing an Xml data source into an xml data structure, you can use theses functions. But if you want advanced parsing usage, please look at the XmlParser module. All the parsing functions can raise some exceptions, see the Exceptions section for more informations.

val parse_file : string -> xml

Parse the named file into an Xml data structure.

val parse_in : Pervasives.in_channel -> xml

Read the content of the in_channel and parse it into an Xml data structure.

val parse_string : string -> xml

Parse the string containing an Xml document into an Xml data structure.

val parse_string_with : XmlParser.t -> string -> xml
Xml Exceptions

Several exceptions can be raised when parsing an Xml document :

  • Xml.Error is raised when an xml parsing error occurs. the Xml.error_msg tells you which error occured during parsing and the Xml.error_pos can be used to retreive the document location where the error occured at.
  • Xml.File_not_found is raised when and error occured while opening a file with the Xml.parse_file function or when a DTD file declared by the Xml document is not found (see the XmlParser module for more informations on how to handle the DTD file loading).

If the Xml document is containing a DTD, then some other exceptions can be raised, see the module Dtd for more informations.

type error_pos
type error_msg = Types.error_msg =
  1. | UnterminatedComment
  2. | UnterminatedString
  3. | UnterminatedEntity
  4. | IdentExpected
  5. | CloseExpected
  6. | NodeExpected
  7. | AttributeNameExpected
  8. | AttributeValueExpected
  9. | EndOfTagExpected of string
  10. | EOFExpected
type error = error_msg * error_pos
exception Error of error
exception File_not_found of string
val error : error -> string

Get a full error message from an Xml error.

val error_msg : error_msg -> string

Get the Xml error message as a string.

val line : error_pos -> int

Get the line the error occured at.

val range : error_pos -> int * int

Get the relative character range (in current line) the error occured at.

val abs_range : error_pos -> int * int

Get the absolute character range the error occured at.

Xml Functions
exception Not_element of xml
exception Not_pcdata of xml
exception No_attribute of string
val tag : xml -> string

tag xdata returns the tag value of the xml node. Raise Xml.Not_element if the xml is not an element

val pcdata : xml -> string

pcdata xdata returns the PCData value of the xml node. Raise Xml.Not_pcdata if the xml is not a PCData

val attribs : xml -> (string * string) list

attribs xdata returns the attribute list of the xml node. First string if the attribute name, second string is attribute value. Raise Xml.Not_element if the xml is not an element

val attrib : xml -> string -> string

attrib xdata "href" returns the value of the "href" attribute of the xml node (attribute matching is case-insensitive). Raise Xml.No_attribute if the attribute does not exists in the node's attribute list Raise Xml.Not_element if the xml is not an element

val children : xml -> xml list

children xdata returns the children list of the xml node Raise Xml.Not_element if the xml is not an element

val iter : (xml -> unit) -> xml -> unit

iter f xdata calls f on all children of the xml node. Raise Xml.Not_element if the xml is not an element

val map : (xml -> 'a) -> xml -> 'a list

map f xdata is equivalent to List.map f (Xml.children xdata) Raise Xml.Not_element if the xml is not an element

val fold : ('a -> xml -> 'a) -> 'a -> xml -> 'a

fold f init xdata is equivalent to List.fold_left f init (Xml.children xdata) Raise Xml.Not_element if the xml is not an element

Xml Printing
val to_string : xml -> string

Print the xml data structure into a compact xml string (without any user-readable formating ).

val to_string_fmt : xml -> string

Print the xml data structure into an user-readable string with tabs and lines break between different nodes.

val to_human_string : xml -> string
module type X = sig ... end
module Make (X : X) : sig ... end