XmlReader Class Reference

#include <XmlReader.hpp>

Classes
struct	ElementInfo

Public Member Functions
	XmlReader (const XmlReader &)=delete
	XmlReader (std::istream &inputStream, string streamName)
	XmlReader (string filePath)
vector< string >	attributeNames () const
string	attributeValue (string name) const
string	elementName () const
XmlReader &	operator= (const XmlReader &)=delete
bool	readNextStartElement ()
void	skipCurrentElement ()
void	throwError (string message)

Private Member Functions
char	get ()
string	getName ()
string	getValue ()
char	peek ()
void	skip ()
void	skipBOM ()
void	skipUpTo (string match)
void	skipWhiteSpace ()

Private Attributes
bool	_elementIsEmpty
vector< ElementInfo >	_elementStack
std::istream &	_in
std::ifstream	_infile
uint64_t	_lineNumber
string	_streamName

Detailed Description

The XmlReader class implements a parser for the subset of XML that is sufficient to represent SMILE schemas and datasets. Specifically, the input stream must be a well-formed XML 1.0 document with the following additional limitations and caveats.

• The text must be UTF-8 encoded (upwards compatible with 7-bit ASCII). Byte sequences that are not valid UTF-8 result in an error.
• The presence of a document type definition (DTD) is not supported and results in an error.
• Only (nested) elements and element attributes are supported. Comments and processing instructions (including the XML prolog declaration on the first line) are ignored. CDATA sections or text other than white space between elements result in an error.
• Element and attribute names must start with a 7-bit ASCII letter [a-zA-Z] and can further contain letters [a-zA-Z], digits [0-9], and dashes (-). Any other characters are prohibited and will result in an error (note that this is a lot more restrictive than standard XML).
• There is no support for namespaces; a colon in a name results in an error (per the above).
• Attribute value strings may be surrounded by single or double quotes. To allow attribute values to contain both single and double quotes, the single-quote character (') may be represented as "&apos;", and the double-quote character (") as "&quot;". - The ampersand character (\&) and the angle brackets (<,>) in attribute values should be represented as "&", "<", and ">" respectively. Other than these, entity and character references (starting with an &) are not supported and result in an error.
• Newline characters are not allowed in attribute values, and a tab is interpreted as a space.

When an error occurs while opening or parsing the XML data stream, the constructor and methods of this class throw a FatalError with an appropriate error message.

Constructor & Destructor Documentation

XmlReader() [1/3]

XmlReader::XmlReader	(	std::istream &	inputStream,
		string	streamName )

This constructor accepts and retains a reference to the input stream to be parsed and initializes the XML parser. It verifies that the stream is ready for reading and consumes the UTF-8 BOM if it is present at the beginning of the stream. The second argument provides a human readable string to identify the stream in error messages.

XmlReader() [2/3]

XmlReader::XmlReader

(

string

filePath

)

This constructor opens the file with the specified path as the input stream to be parsed and initializes the XML parser. It verifies that the file is ready for reading and consumes the UTF-8 BOM if it is present at the beginning of the file. The file path is used to identify the stream in error messages.

XmlReader() [3/3]

XmlReader::XmlReader ( const XmlReader & )

delete

The copy constructor is deleted because instances of this class should never be copied or moved.

Member Function Documentation

attributeNames()

vector< string > XmlReader::attributeNames

(

)

const

Returns a list with the names of the attributes of the current element. The list is empty if there is no current element or if the current element has no attributes.

attributeValue()

string XmlReader::attributeValue

(

string

name

)

const

Returns the value of the current element's attribute with the specified name. If there is no current element or if the current element has no attribute with the given name, an empty string is returned.

elementName()

string XmlReader::elementName

(

)

const

Returns the name of the current element, or the empty string if there is none.

get()

char XmlReader::get ( )

private

Gets exactly one character.

getName()

string XmlReader::getName ( )

private

Gets and returns a name token starting with a letter and further consisting of letters and digits. The name token can be terminated by whitespace or by the '=' sign; the terminating character is not consumed. If any other characters are encountered, the function throws an error.

getValue()

string XmlReader::getValue ( )

private

Gets and returns an attribute value string surrounded by single or double quotes. Quotes of the other type may occur in the string, as well as the escape sequences "&apos;", "\&quot;", "&amp;", "&lt;", and "&gt;". If any newline or control characters are encountered in the value string, the function throws an error.

operator=()

XmlReader & XmlReader::operator= ( const XmlReader & )

delete

The assignment operator is deleted because instances of this class should never be copied or moved.

peek()

char XmlReader::peek ( )

private

Peeks at the next character without consuming it. The character is returned as type char (which may be signed or unsigned). If there are no more characters in the input stream, the function returns a system-dependent value that should differ from regular characters (probably 0xFF).

readNextStartElement()

bool XmlReader::readNextStartElement

(

)

Reads until the next start element within the current element. Returns true when a start element was reached, and false when the end element for the current element was reached. The current element is the element matching the most recently parsed start element of which a matching end element has not yet been reached. When the parser has reached the end element, the parent element becomes the current element.

skip()

void XmlReader::skip ( )

private

Skips exactly one character.

skipBOM()

void XmlReader::skipBOM ( )

private

Skips (a portion of) the UTF-8 byte order marker, if present.

skipCurrentElement()

void XmlReader::skipCurrentElement

(

)

Reads and ignores any remaining contents of the current element, i.e. any (nested) child elements, including the element's end tag, causing the current element's parent element to become current.

skipUpTo()

void XmlReader::skipUpTo ( string match )

private

Skips anything up to and including the given string, while counting lines. The given string should not be empty and should not contain newline characters.

skipWhiteSpace()

void XmlReader::skipWhiteSpace ( )

private

Skips consecutive white space (space, tab, newline), if any, while counting lines.

throwError()

void XmlReader::throwError

(

string

message

)

Throws an error with the specified error message, augmented with information about the current line number in the input stream. This function is used by the XML reader when an error occurs, and it may also be used by a client to raise a custom error.

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The documentation for this class was generated from the following file:

• XmlReader.hpp