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Last update Sun Apr 19 16:54:26 2009

# std.xml

Classes and functions for creating and parsing XML

The basic architecture of this module is that there are standalone functions, classes for constructing an XML document from scratch (Tag, Element and Document), and also classes for parsing a pre-existing XML file (ElementParser and DocumentParser). The parsing classes may be used to build a Document, but that is not their primary purpose. The handling capabilities of DocumentParser and ElementParser are sufficiently customizable that you can make them do pretty much whatever you want.

Authors:
Janice Caron

Date:
2008.02.12 - 2008.05.07

License:
Public Domain

Example:
This example creates a DOM (Document Object Model) tree from an XML file.

    import std.xml;
    import std.stdio;
    import std.string;

    // books.xml is used in various samples throughout the Microsoft XML Core
    // Services (MSXML) SDK.
    //
    // See http://msdn2.microsoft.com/en-us/library/ms762271(VS.85).aspx

    void main()
    {
        string s = cast(string)std.file.read("books.xml");

        // Check for well-formedness
        check(s);

        // Make a DOM tree
        auto doc = new Document(s);

        // Plain-print it
        writefln(doc);
    }

Example:
This example does much the same thing, except that the file is deconstructed and reconstructed by hand. This is more work, but the techniques involved offer vastly more power.

    import std.xml;
    import std.stdio;
    import std.string;

    struct Book
    {
        string id;
        string author;
        string title;
        string genre;
        string price;
        string pubDate;
        string description;
    }

    void main()
    {
        string s = cast(string)std.file.read("books.xml");

        // Check for well-formedness
        check(s);

        // Take it apart
        Book[] books;

        auto xml = new DocumentParser(s);
        xml.onStartTag["book"] = (ElementParser xml)
        {
            Book book;
            book.id = xml.tag.attr["id"];

            xml.onEndTag["author"]       = (in Element e) { book.author      = e.text; };
            xml.onEndTag["title"]        = (in Element e) { book.title       = e.text; };
            xml.onEndTag["genre"]        = (in Element e) { book.genre       = e.text; };
            xml.onEndTag["price"]        = (in Element e) { book.price       = e.text; };
            xml.onEndTag["publish-date"] = (in Element e) { book.pubDate     = e.text; };
            xml.onEndTag["description"]  = (in Element e) { book.description = e.text; };

            xml.parse();

            books ~= book;
        };
        xml.parse();

        // Put it back together again;
        auto doc = new Document(new Tag("catalog"));
        foreach(book;books)
        {
            auto element = new Element("book");
            element.tag.attr["id"] = book.id;

            element ~= new Element("author",      book.author);
            element ~= new Element("title",       book.title);
            element ~= new Element("genre",       book.genre);
            element ~= new Element("price",       book.price);
            element ~= new Element("publish-date",book.pubDate);
            element ~= new Element("description", book.description);

            doc ~= element;
        }

        // Pretty-print it
        writefln(join(doc.pretty(3),"\n"));
    }

bool isChar(dchar c);
  Returns true if the character is a character according to the XML standard

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

bool isSpace(dchar c);
  Returns true if the character is whitespace according to the XML standard

  Only the following characters are considered whitespace in XML - space, tab, carriage return and linefeed

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

bool isDigit(dchar c);
  Returns true if the character is a digit according to the XML standard

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

bool isLetter(dchar c);
  Returns true if the character is a letter according to the XML standard

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

bool isIdeographic(dchar c);
  Returns true if the character is an ideographic character according to the XML standard

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

bool isBaseChar(dchar c);
  Returns true if the character is a base character according to the XML standard

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

bool isCombiningChar(dchar c);
  Returns true if the character is a combining character according to the XML standard

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

bool isExtender(dchar c);
  Returns true if the character is an extender according to the XML standard

  Standards:
  XML 1.0

  Parameters:

  dchar c | the character to be tested

string encode(string s);
  Encodes a string by replacing all characters which need to be escaped with appropriate predefined XML entities.

  encode() escapes certain characters (ampersand, quote, apostrophe, less-than and greater-than), and similarly, decode() unescapes them. These functions are provided for convenience only. You do not need to use them when using the std.xml classes, because then all the encoding and decoding will be done for you automatically.

  If the string is not modified, the original will be returned.

  Standards:
  XML 1.0

  Parameters:

  string s | The string to be encoded

  Returns:
  The encoded string

  Examples:

       writefln(encode("a > b")); // writes "a &gt; b"

enum DecodeMode;
  Mode to use for decoding.

  NONE
  Do not decode
  LOOSE
  Decode, but ignore errors
  STRICT
  Decode, and throw exception on error

string decode(string s, DecodeMode mode = (DecodeMode).LOOSE);
  Decodes a string by unescaping all predefined XML entities.

  encode() escapes certain characters (ampersand, quote, apostrophe, less-than and greater-than), and similarly, decode() unescapes them. These functions are provided for convenience only. You do not need to use them when using the std.xml classes, because then all the encoding and decoding will be done for you automatically.

  This function decodes the entities &amp;, &quot;, &apos;, &lt; and &gt, as well as decimal and hexadecimal entities such as &#x20AC;

  If the string does not contain an ampersand, the original will be returned.

  Note that the "mode" parameter can be one of DecodeMode.NONE (do not decode), DecodeMode.LOOSE (decode, but ignore errors), or DecodeMode.STRICT (decode, and throw a DecodeException in the event of an error).

  Standards:
  XML 1.0

  Parameters:

  string s | The string to be decoded
  DecodeMode mode | (optional) Mode to use for decoding. (Defaults to LOOSE).

  Throws:
  DecodeException if mode == DecodeMode.STRICT and decode fails

  Returns:
  The decoded string

  Examples:

       writefln(decode("a &gt; b")); // writes "a > b"

class Document: std.xml.Element;
  Class representing an XML document.

  Standards:
  XML 1.0

  string prolog;
    Contains all text which occurs before the root element. Defaults to <?xml version="1.0"?>

  string epilog;
    Contains all text which occurs after the root element. Defaults to the empty string

  this(string s);
    Constructs a Document by parsing XML text.

    This function creates a complete DOM (Document Object Model) tree.

    The input to this function MUST be valid XML. This is enforced by DocumentParser's in contract.

    Parameters:

    string s | the complete XML text.

  this(const(Tag) tag);
    Constructs a Document from a Tag.

    Parameters:

    const(Tag) tag | the start tag of the document.

  const bool opEquals(Object o);
    Compares two Documents for equality

    Examples:

         Document d1,d2;
         if (d1 == d2) { }

  const int opCmp(Object o);
    Compares two Documents

    You should rarely need to call this function. It exists so that Documents can be used as associative array keys.

    Examples:

         Document d1,d2;
         if (d1 < d2) { }

  const hash_t toHash();
    Returns the hash of a Document

    You should rarely need to call this function. It exists so that Documents can be used as associative array keys.

  const string toString();
    Returns the string representation of a Document. (That is, the complete XML of a document).

class Element: std.xml.Item;
  Class representing an XML element.

  Standards:
  XML 1.0

  Tag tag;
    The start tag of the element

  Item[] items;
    The element's items

  Text[] texts;
    The element's text items

  CData[] cdatas;
    The element's CData items

  Comment[] comments;
    The element's comments

  ProcessingInstruction[] pis;
    The element's processing instructions

  Element[] elements;
    The element's child elements

  this(string name, string interior = null);
    Constructs an Element given a name and a string to be used as a Text interior.

    Parameters:

    string name | the name of the element.
    string interior | (optional) the string interior.

    Examples:

         auto element = new Element("title","Serenity")
             // constructs the element <title>Serenity</title>

  this(const(Tag) tag_);
    Constructs an Element from a Tag.

    Parameters:

    tag | the start or empty tag of the element.

  void opCatAssign(Text item);
    Append a text item to the interior of this element

    Parameters:

    Text item | the item you wish to append.

    Examples:

         Element element;
         element ~= new Text("hello");

  void opCatAssign(CData item);
    Append a CData item to the interior of this element

    Parameters:

    CData item | the item you wish to append.

    Examples:

         Element element;
         element ~= new CData("hello");

  void opCatAssign(Comment item);
    Append a comment to the interior of this element

    Parameters:

    Comment item | the item you wish to append.

    Examples:

         Element element;
         element ~= new Comment("hello");

  void opCatAssign(ProcessingInstruction item);
    Append a processing instruction to the interior of this element

    Parameters:

    ProcessingInstruction item | the item you wish to append.

    Examples:

         Element element;
         element ~= new ProcessingInstruction("hello");

  void opCatAssign(Element item);
    Append a complete element to the interior of this element

    Parameters:

    Element item | the item you wish to append.

    Examples:

         Element element;
         Element other = new Element("br");
         element ~= other;
            // appends element representing <br />

  bool opEquals(Object o);
    Compares two Elements for equality

    Examples:

         Element e1,e2;
         if (e1 == e2) { }

  int opCmp(Object o);
    Compares two Elements

    You should rarely need to call this function. It exists so that Elements can be used as associative array keys.

    Examples:

         Element e1,e2;
         if (e1 < e2) { }

  hash_t toHash();
    Returns the hash of an Element

    You should rarely need to call this function. It exists so that Elements can be used as associative array keys.

  const string text(DecodeMode mode = (DecodeMode).LOOSE);
    Returns the decoded interior of an element.

    The element is assumed to containt text only. So, for example, given XML such as "<title>Good &amp; Bad</title>", will return "Good & Bad".

    Parameters:

    DecodeMode mode | (optional) Mode to use for decoding. (Defaults to LOOSE).

    Throws:
    DecodeException if decode fails

  const immutable(char)[][] pretty(uint indent = 2);
    Returns an indented string representation of this item

    Parameters:

    uint indent | (optional) number of spaces by which to indent this element. Defaults to 2.

  const string toString();
    Returns the string representation of an Element

    Examples:

         auto element = new Element("br");
         writefln(element.toString); // writes "<br />"

  const bool isEmptyXML();
    Returns false always

enum TagType;
  Tag types.

  START
  Used for start tags
  END
  Used for end tags
  EMPTY
  Used for empty tags

class Tag;
  Class representing an XML tag.

  Standards:
  XML 1.0

  The class invariant guarantees
  - that type is a valid enum TagType value
  - that name consists of valid characters
  - that each attribute name consists of valid characters

  TagType type;
    Type of tag

  string name;
    Tag name

  immutable(char)[][immutable(char)[]] attr;
    Associative array of attributes

  this(string name, TagType type = (TagType).START);
    Constructs an instance of Tag with a specified name and type

    The constructor does not initialize the attributes. To initialize the attributes, you access the attr member variable.

    Parameters:

    string name | the Tag's name
    TagType type | (optional) the Tag's type. If omitted, defaults to TagType.START.

    Examples:

         auto tag = new Tag("img",Tag.EMPTY);
         tag.attr["src"] = "http://example.com/example.jpg";

  const bool opEquals(Object o);
    Compares two Tags for equality

    You should rarely need to call this function. It exists so that Tags can be used as associative array keys.

    Examples:

         Tag tag1,tag2
         if (tag1 == tag2) { }

  const int opCmp(Object o);
    Compares two Tags

    Examples:

         Tag tag1,tag2
         if (tag1 < tag2) { }

  const hash_t toHash();
    Returns the hash of a Tag

    You should rarely need to call this function. It exists so that Tags can be used as associative array keys.

  const string toString();
    Returns the string representation of a Tag

    Examples:

         auto tag = new Tag("book",TagType.START);
         writefln(tag.toString); // writes "<book>"

  const bool isStart();
    Returns true if the Tag is a start tag

    Examples:

         if (tag.isStart) { }

  const bool isEnd();
    Returns true if the Tag is an end tag

    Examples:

         if (tag.isEnd) { }

  const bool isEmpty();
    Returns true if the Tag is an empty tag

    Examples:

         if (tag.isEmpty) { }

class Comment: std.xml.Item;
  Class representing a comment

  this(string content);
    Construct a comment

    Parameters:

    string content | the body of the comment

    Throws:
    CommentException if the comment body is illegal (contains "--" or exactly equals "-")

    Examples:

         auto item = new Comment("This is a comment");
            // constructs <!--This is a comment-->

  bool opEquals(Object o);
    Compares two comments for equality

    Examples:

         Comment item1,item2;
         if (item1 == item2) { }

  int opCmp(Object o);
    Compares two comments

    You should rarely need to call this function. It exists so that Comments can be used as associative array keys.

    Examples:

         Comment item1,item2;
         if (item1 < item2) { }

  hash_t toHash();
    Returns the hash of a Comment

    You should rarely need to call this function. It exists so that Comments can be used as associative array keys.

  const string toString();
    Returns a string representation of this comment

  const bool isEmptyXML();
    Returns false always

class CData: std.xml.Item;
  Class representing a Character Data section

  this(string content);
    Construct a chraracter data section

    Parameters:

    string content | the body of the character data segment

    Throws:
    CDataException if the segment body is illegal (contains "]]>")

    Examples:

         auto item = new CData("<b>hello</b>");
            // constructs <![CDATA[<b>hello</b>]]>

  bool opEquals(Object o);
    Compares two CDatas for equality

    Examples:

         CData item1,item2;
         if (item1 == item2) { }

  int opCmp(Object o);
    Compares two CDatas

    You should rarely need to call this function. It exists so that CDatas can be used as associative array keys.

    Examples:

         CData item1,item2;
         if (item1 < item2) { }

  hash_t toHash();
    Returns the hash of a CData

    You should rarely need to call this function. It exists so that CDatas can be used as associative array keys.

  const string toString();
    Returns a string representation of this CData section

  const bool isEmptyXML();
    Returns false always

class Text: std.xml.Item;
  Class representing a text (aka Parsed Character Data) section

  this(string content);
    Construct a text (aka PCData) section

    Parameters:

    string content | the text. This function encodes the text before insertion, so it is safe to insert any text

    Examples:

         auto Text = new CData("a < b");
            // constructs a &lt; b

  bool opEquals(Object o);
    Compares two text sections for equality

    Examples:

         Text item1,item2;
         if (item1 == item2) { }

  int opCmp(Object o);
    Compares two text sections

    You should rarely need to call this function. It exists so that Texts can be used as associative array keys.

    Examples:

         Text item1,item2;
         if (item1 < item2) { }

  hash_t toHash();
    Returns the hash of a text section

    You should rarely need to call this function. It exists so that Texts can be used as associative array keys.

  const string toString();
    Returns a string representation of this Text section

  const bool isEmptyXML();
    Returns true if the content is the empty string

class XMLInstruction: std.xml.Item;
  Class representing an XML Instruction section

  this(string content);
    Construct an XML Instruction section

    Parameters:

    string content | the body of the instruction segment

    Throws:
    XIException if the segment body is illegal (contains ">")

    Examples:

         auto item = new XMLInstruction("ATTLIST");
            // constructs <!ATTLIST>

  bool opEquals(Object o);
    Compares two XML instructions for equality

    Examples:

         XMLInstruction item1,item2;
         if (item1 == item2) { }

  int opCmp(Object o);
    Compares two XML instructions

    You should rarely need to call this function. It exists so that XmlInstructions can be used as associative array keys.

    Examples:

         XMLInstruction item1,item2;
         if (item1 < item2) { }

  hash_t toHash();
    Returns the hash of an XMLInstruction

    You should rarely need to call this function. It exists so that XmlInstructions can be used as associative array keys.

  const string toString();
    Returns a string representation of this XmlInstruction

  const bool isEmptyXML();
    Returns false always

class ProcessingInstruction: std.xml.Item;
  Class representing a Processing Instruction section

  this(string content);
    Construct a Processing Instruction section

    Parameters:

    string content | the body of the instruction segment

    Throws:
    PIException if the segment body is illegal (contains "?>")

    Examples:

         auto item = new ProcessingInstruction("php");
            // constructs <?php?>

  bool opEquals(Object o);
    Compares two processing instructions for equality

    Examples:

         ProcessingInstruction item1,item2;
         if (item1 == item2) { }

  int opCmp(Object o);
    Compares two processing instructions

    You should rarely need to call this function. It exists so that ProcessingInstructions can be used as associative array keys.

    Examples:

         ProcessingInstruction item1,item2;
         if (item1 < item2) { }

  hash_t toHash();
    Returns the hash of a ProcessingInstruction

    You should rarely need to call this function. It exists so that ProcessingInstructions can be used as associative array keys.

  const string toString();
    Returns a string representation of this ProcessingInstruction

  const bool isEmptyXML();
    Returns false always

abstract class Item;
  Abstract base class for XML items

  abstract bool opEquals(Object o);
    Compares with another Item of same type for equality

  abstract int opCmp(Object o);
    Compares with another Item of same type

  abstract hash_t toHash();
    Returns the hash of this item

  abstract const string toString();
    Returns a string representation of this item

  const immutable(char)[][] pretty(uint indent);
    Returns an indented string representation of this item

    Parameters:

    uint indent | number of spaces by which to indent child elements

  abstract const bool isEmptyXML();
    Returns true if the item represents empty XML text

class DocumentParser: std.xml.ElementParser;
  Class for parsing an XML Document.

  This is a subclass of ElementParser. Most of the useful functions are documented there.

  Standards:
  XML 1.0

  BUGS:
  Currently only supports UTF documents.

  If there is an encoding attribute in the prolog, it is ignored.

  this(string xmlText_);
    Constructs a DocumentParser.

    The input to this function MUST be valid XML. This is enforced by the function's in contract.

    Parameters:

    xmltext | the entire XML document as text

class ElementParser;
  Class for parsing an XML element.

  Standards:
  XML 1.0

  Note that you cannot construct instances of this class directly. You can construct a DocumentParser (which is a subclass of ElementParser), but otherwise, Instances of ElementParser will be created for you by the library, and passed your way via onStartTag handlers.

  const const(Tag) tag();
    The Tag at the start of the element being parsed. You can read this to determine the tag's name and attributes.

  void delegate(ElementParser parser)[immutable(char)[]] onStartTag;
    Register a handler which will be called whenever a start tag is encountered which matches the specified name. You can also pass null as the name, in which case the handler will be called for any unmatched start tag.

    Examples:

         // Call this function whenever a <podcast> start tag is encountered
         onStartTag["podcast"] = (ElementParser xml)
         {
             // Your code here
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

         // call myEpisodeStartHandler (defined elsewhere) whenever an <episode>
         // start tag is encountered
         onStartTag["episode"] = &myEpisodeStartHandler;

         // call delegate dg for all other start tags
         onStartTag[null] = dg;

    This library will supply your function with a new instance of ElementHandler, which may be used to parse inside the element whose start tag was just found, or to identify the tag attributes of the element, etc.

    Note that your function will be called for both start tags and empty tags. That is, we make no distinction between <br></br> and <br/>.

  void delegate(in const(Element) element)[immutable(char)[]] onEndTag;
    Register a handler which will be called whenever an end tag is encountered which matches the specified name. You can also pass null as the name, in which case the handler will be called for any unmatched end tag.

    Examples:

         // Call this function whenever a </podcast> end tag is encountered
         onEndTag["podcast"] = (in Element e)
         {
             // Your code here
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

         // call myEpisodeEndHandler (defined elsewhere) whenever an </episode>
         // end tag is encountered
         onEndTag["episode"] = &myEpisodeEndHandler;

         // call delegate dg for all other end tags
         onEndTag[null] = dg;

    Note that your function will be called for both start tags and empty tags. That is, we make no distinction between <br></br> and <br/>.

  void onText(Handler handler);
    Register a handler which will be called whenever text is encountered.

    Examples:

         // Call this function whenever text is encountered
         onText = (string s)
         {
             // Your code here

             // The passed parameter s will have been decoded by the time you see
             // it, and so may contain any character.
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

  void onTextRaw(Handler handler);
    Register an alternative handler which will be called whenever text is encountered. This differs from onText in that onText will decode the text, wheras onTextRaw will not. This allows you to make design choices, since onText will be more accurate, but slower, while onTextRaw will be faster, but less accurate. Of course, you can still call decode() within your handler, if you want, but you'd probably want to use onTextRaw only in circumstances where you know that decoding is unnecessary.

    Examples:

         // Call this function whenever text is encountered
         onText = (string s)
         {
             // Your code here

             // The passed parameter s will NOT have been decoded.
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

  void onCData(Handler handler);
    Register a handler which will be called whenever a character data segement is encountered.

    Examples:

         // Call this function whenever a CData section is encountered
         onCData = (string s)
         {
             // Your code here

             // The passed parameter s does not include the opening <![CDATA[
             // nor closing ]]>
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

  void onComment(Handler handler);
    Register a handler which will be called whenever a comment is encountered.

    Examples:

         // Call this function whenever a comment is encountered
         onComment = (string s)
         {
             // Your code here

             // The passed parameter s does not include the opening <!-- nor
             // closing -->
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

  void onPI(Handler handler);
    Register a handler which will be called whenever a processing instruction is encountered.

    Examples:

         // Call this function whenever a processing instruction is encountered
         onPI = (string s)
         {
             // Your code here

             // The passed parameter s does not include the opening <? nor
             // closing ?>
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

  void onXI(Handler handler);
    Register a handler which will be called whenever an XML instruction is encountered.

    Examples:

         // Call this function whenever an XML instruction is encountered
         // (Note: XML instructions may only occur preceeding the root tag of a
        ) // document.
         onPI = (string s)
         {
             // Your code here

             // The passed parameter s does not include the opening <! nor
             // closing >
             //
             // This is a a closure, so code here may reference
             // variables which are outside of this scope
         };

  void parse();
    Parse an XML element.

    Parsing will continue until the end of the current element. Any items encountered for which a handler has been registered will invoke that handler.

    Throws:
    various kinds of XMLException

  const string toString();
    Returns that part of the element which has already been parsed

void check(string s);
  Check an entire XML document for well-formedness

  Parameters:

  string s | the document to be checked, passed as a string

  Throws:
  CheckException if the document is not well formed

  CheckException's toString() method will yield the complete heirarchy of parse failure (the XML equivalent of a stack trace), giving the line and column number of every failure at every level.

class XMLException: object.Exception;
  The base class for exceptions thrown by this module

class CommentException: std.xml.XMLException;
  Thrown during Comment constructor

class CDataException: std.xml.XMLException;
  Thrown during CData constructor

class XIException: std.xml.XMLException;
  Thrown during XMLInstruction constructor

class PIException: std.xml.XMLException;
  Thrown during ProcessingInstruction constructor

class TextException: std.xml.XMLException;
  Thrown during Text constructor

class DecodeException: std.xml.XMLException;
  Thrown during decode()

class InvalidTypeException: std.xml.XMLException;
  Thrown if comparing with wrong type

class TagException: std.xml.XMLException;
  Thrown when parsing for Tags

class CheckException: std.xml.XMLException;
  Thrown during check()

  CheckException err;
    Parent in heirarchy

  string msg;
    Name of production rule which failed to parse, or specific error message

  uint line;
    Line number at which parse failure occurred

  uint column;
    Column number at which parse failure occurred

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