## xmlregexp

xmlregexp - regular expressions handling

basic API for libxml regular expressions handling used for XML Schemas and validation.

Author(s): Daniel Veillard

## Synopsis

    typedef struct _xmlExpCtxt xmlExpCtxt;
    typedef xmlExpCtxt * xmlExpCtxtPtr;
    typedef struct _xmlExpNode xmlExpNode;
    typedef xmlExpNode * xmlExpNodePtr;
    typedef enum xmlExpNodeType;
    typedef struct _xmlRegExecCtxt xmlRegExecCtxt;
    typedef xmlRegExecCtxt * xmlRegExecCtxtPtr;
    typedef struct _xmlRegexp xmlRegexp;
    typedef xmlRegexp * xmlRegexpPtr;
    int	xmlExpCtxtNbCons		(xmlExpCtxtPtr ctxt);
    int	xmlExpCtxtNbNodes		(xmlExpCtxtPtr ctxt);
    void	xmlExpDump			(xmlBufferPtr buf,
    					 xmlExpNodePtr expr);
    xmlExpNodePtr	xmlExpExpDerive		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 xmlExpNodePtr sub);
    void	xmlExpFree			(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp);
    void	xmlExpFreeCtxt			(xmlExpCtxtPtr ctxt);
    int	xmlExpGetLanguage		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 const xmlChar ** langList,
    					 int len);
    int	xmlExpGetStart			(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 const xmlChar ** tokList,
    					 int len);
    int	xmlExpIsNillable		(xmlExpNodePtr exp);
    int	xmlExpMaxToken			(xmlExpNodePtr expr);
    xmlExpNodePtr	xmlExpNewAtom		(xmlExpCtxtPtr ctxt,
    					 const xmlChar * name,
    					 int len);
    xmlExpCtxtPtr	xmlExpNewCtxt		(int maxNodes,
    					 xmlDictPtr dict);
    xmlExpNodePtr	xmlExpNewOr		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr left,
    					 xmlExpNodePtr right);
    xmlExpNodePtr	xmlExpNewRange		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr subset,
    					 int min,
    					 int max);
    xmlExpNodePtr	xmlExpNewSeq		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr left,
    					 xmlExpNodePtr right);
    xmlExpNodePtr	xmlExpParse		(xmlExpCtxtPtr ctxt,
    					 const char * expr);
    void	xmlExpRef			(xmlExpNodePtr exp);
    xmlExpNodePtr	xmlExpStringDerive	(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 const xmlChar * str,
    					 int len);
    int	xmlExpSubsume			(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 xmlExpNodePtr sub);
    typedef void xmlRegExecCallbacks		(xmlRegExecCtxtPtr exec,
    					 const xmlChar * token,
    					 void * transdata,
    					 void * inputdata);
    int	xmlRegExecErrInfo		(xmlRegExecCtxtPtr exec,
    					 const xmlChar ** string,
    					 int * nbval,
    					 int * nbneg,
    					 xmlChar ** values,
    					 int * terminal);
    int	xmlRegExecNextValues		(xmlRegExecCtxtPtr exec,
    					 int * nbval,
    					 int * nbneg,
    					 xmlChar ** values,
    					 int * terminal);
    int	xmlRegExecPushString		(xmlRegExecCtxtPtr exec,
    					 const xmlChar * value,
    					 void * data);
    int	xmlRegExecPushString2		(xmlRegExecCtxtPtr exec,
    					 const xmlChar * value,
    					 const xmlChar * value2,
    					 void * data);
    void	xmlRegFreeExecCtxt		(xmlRegExecCtxtPtr exec);
    void	xmlRegFreeRegexp		(xmlRegexpPtr regexp);
    xmlRegExecCtxtPtr	xmlRegNewExecCtxt	(xmlRegexpPtr comp,
    						 xmlRegExecCallbacks callback,
    						 void * data);
    xmlRegexpPtr	xmlRegexpCompile	(const xmlChar * regexp);
    int	xmlRegexpExec			(xmlRegexpPtr comp,
    					 const xmlChar * content);
    int	xmlRegexpIsDeterminist		(xmlRegexpPtr comp);
    void	xmlRegexpPrint			(FILE * output,
    					 xmlRegexpPtr regexp);

## Description

## Details

### Structure xmlExpCtxt

    struct _xmlExpCtxt {
    The content of this structure is not made public by the API.
    } xmlExpCtxt;

### Typedef xmlExpCtxtPtr

    xmlExpCtxt * xmlExpCtxtPtr;

### Structure xmlExpNode

    struct _xmlExpNode {
    The content of this structure is not made public by the API.
    } xmlExpNode;

### Typedef xmlExpNodePtr

    xmlExpNode * xmlExpNodePtr;

### Enum xmlExpNodeType

    enum xmlExpNodeType {
        XML_EXP_EMPTY = 0
        XML_EXP_FORBID = 1
        XML_EXP_ATOM = 2
        XML_EXP_SEQ = 3
        XML_EXP_OR = 4
        XML_EXP_COUNT = 5
    };

### Structure xmlRegExecCtxt

    struct _xmlRegExecCtxt {
    The content of this structure is not made public by the API.
    } xmlRegExecCtxt;

### Typedef xmlRegExecCtxtPtr

    xmlRegExecCtxt * xmlRegExecCtxtPtr;

A libxml progressive regular expression evaluation context

### Structure xmlRegexp

    struct _xmlRegexp {
    The content of this structure is not made public by the API.
    } xmlRegexp;

### Typedef xmlRegexpPtr

    xmlRegexp * xmlRegexpPtr;

A libxml regular expression, they can actually be far more complex thank the POSIX regex expressions.

### Function type xmlRegExecCallbacks

    void	xmlRegExecCallbacks		(xmlRegExecCtxtPtr exec,
    					 const xmlChar * token,
    					 void * transdata,
    					 void * inputdata)

Callback function when doing a transition in the automata

`exec`: | the regular expression context
`token`: | the current token string
`transdata`: | transition data
`inputdata`: | input data

### Variable emptyExp

    xmlExpNodePtr emptyExp;

### Variable forbiddenExp

    xmlExpNodePtr forbiddenExp;

### xmlExpCtxtNbCons ()

    int	xmlExpCtxtNbCons		(xmlExpCtxtPtr ctxt)

Debugging facility provides the number of allocated nodes over lifetime

`ctxt`: | an expression context
`Returns`: | the number of nodes ever allocated or -1 in case of error

### xmlExpCtxtNbNodes ()

    int	xmlExpCtxtNbNodes		(xmlExpCtxtPtr ctxt)

Debugging facility provides the number of allocated nodes at a that point

`ctxt`: | an expression context
`Returns`: | the number of nodes in use or -1 in case of error

### xmlExpDump ()

    void	xmlExpDump			(xmlBufferPtr buf,
    					 xmlExpNodePtr expr)

Serialize the expression as compiled to the buffer

`buf`: | a buffer to receive the output
`expr`: | the compiled expression

### xmlExpExpDerive ()

    xmlExpNodePtr	xmlExpExpDerive		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 xmlExpNodePtr sub)

Evaluates the expression resulting from @exp consuming a sub expression @sub Based on algebraic derivation and sometimes direct Brzozowski derivation it usually takes less than linear time and can handle expressions generating infinite languages.

`ctxt`: | the expressions context
`exp`: | the englobing expression
`sub`: | the subexpression
`Returns`: | the resulting expression or NULL in case of internal error, the result must be freed

### xmlExpFree ()

    void	xmlExpFree			(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp)

Dereference the expression

`ctxt`: | the expression context
`exp`: | the expression

### xmlExpFreeCtxt ()

    void	xmlExpFreeCtxt			(xmlExpCtxtPtr ctxt)

Free an expression context

`ctxt`: | an expression context

### xmlExpGetLanguage ()

    int	xmlExpGetLanguage		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 const xmlChar ** langList,
    					 int len)

Find all the strings used in @exp and store them in @list

`ctxt`: | the expression context
`exp`: | the expression
`langList`: | where to store the tokens
`len`: | the allocated length of @list
`Returns`: | the number of unique strings found, -1 in case of errors and -2 if there is more than @len strings

### xmlExpGetStart ()

    int	xmlExpGetStart			(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 const xmlChar ** tokList,
    					 int len)

Find all the strings that appears at the start of the languages accepted by @exp and store them in @list. E.g. for (a, b) | c it will return the list [a, c]

`ctxt`: | the expression context
`exp`: | the expression
`tokList`: | where to store the tokens
`len`: | the allocated length of @list
`Returns`: | the number of unique strings found, -1 in case of errors and -2 if there is more than @len strings

### xmlExpIsNillable ()

    int	xmlExpIsNillable		(xmlExpNodePtr exp)

Finds if the expression is nillable, i.e. if it accepts the empty sequence

`exp`: | the expression
`Returns`: | 1 if nillable, 0 if not and -1 in case of error

### xmlExpMaxToken ()

    int	xmlExpMaxToken			(xmlExpNodePtr expr)

Indicate the maximum number of input a expression can accept

`expr`: | a compiled expression
`Returns`: | the maximum length or -1 in case of error

### xmlExpNewAtom ()

    xmlExpNodePtr	xmlExpNewAtom		(xmlExpCtxtPtr ctxt,
    					 const xmlChar * name,
    					 int len)

Get the atom associated to this name from that context

`ctxt`: | the expression context
`name`: | the atom name
`len`: | the atom name length in byte (or -1);
`Returns`: | the node or NULL in case of error

### xmlExpNewCtxt ()

    xmlExpCtxtPtr	xmlExpNewCtxt		(int maxNodes,
    					 xmlDictPtr dict)

Creates a new context for manipulating expressions

`maxNodes`: | the maximum number of nodes
`dict`: | optional dictionary to use internally
`Returns`: | the context or NULL in case of error

### xmlExpNewOr ()

    xmlExpNodePtr	xmlExpNewOr		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr left,
    					 xmlExpNodePtr right)

Get the atom associated to the choice @left | @right Note that @left and @right are consumed in the operation, to keep an handle on them use xmlExpRef() and use xmlExpFree() to release them, this is true even in case of failure (unless ctxt == NULL).

`ctxt`: | the expression context
`left`: | left expression
`right`: | right expression
`Returns`: | the node or NULL in case of error

### xmlExpNewRange ()

    xmlExpNodePtr	xmlExpNewRange		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr subset,
    					 int min,
    					 int max)

Get the atom associated to the range (@subset){@min, @max} Note that @subset is consumed in the operation, to keep an handle on it use xmlExpRef() and use xmlExpFree() to release it, this is true even in case of failure (unless ctxt == NULL).

`ctxt`: | the expression context
`subset`: | the expression to be repeated
`min`: | the lower bound for the repetition
`max`: | the upper bound for the repetition, -1 means infinite
`Returns`: | the node or NULL in case of error

### xmlExpNewSeq ()

    xmlExpNodePtr	xmlExpNewSeq		(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr left,
    					 xmlExpNodePtr right)

Get the atom associated to the sequence @left , @right Note that @left and @right are consumed in the operation, to keep an handle on them use xmlExpRef() and use xmlExpFree() to release them, this is true even in case of failure (unless ctxt == NULL).

`ctxt`: | the expression context
`left`: | left expression
`right`: | right expression
`Returns`: | the node or NULL in case of error

### xmlExpParse ()

    xmlExpNodePtr	xmlExpParse		(xmlExpCtxtPtr ctxt,
    					 const char * expr)

Minimal parser for regexps, it understand the following constructs - string terminals - choice operator | - sequence operator , - subexpressions (...) - usual cardinality operators + * and ? - finite sequences { min, max } - infinite sequences { min, * } There is minimal checkings made especially no checking on strings values

`ctxt`: | the expressions context
`expr`: | the 0 terminated string
`Returns`: | a new expression or NULL in case of failure

### xmlExpRef ()

    void	xmlExpRef			(xmlExpNodePtr exp)

Increase the reference count of the expression

`exp`: | the expression

### xmlExpStringDerive ()

    xmlExpNodePtr	xmlExpStringDerive	(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 const xmlChar * str,
    					 int len)

Do one step of Brzozowski derivation of the expression @exp with respect to the input string

`ctxt`: | the expression context
`exp`: | the expression
`str`: | the string
`len`: | the string len in bytes if available
`Returns`: | the resulting expression or NULL in case of internal error

### xmlExpSubsume ()

    int	xmlExpSubsume			(xmlExpCtxtPtr ctxt,
    					 xmlExpNodePtr exp,
    					 xmlExpNodePtr sub)

Check whether @exp accepts all the languages accepted by @sub the input being a subexpression.

`ctxt`: | the expressions context
`exp`: | the englobing expression
`sub`: | the subexpression
`Returns`: | 1 if true 0 if false and -1 in case of failure.

### xmlRegExecErrInfo ()

    int	xmlRegExecErrInfo		(xmlRegExecCtxtPtr exec,
    					 const xmlChar ** string,
    					 int * nbval,
    					 int * nbneg,
    					 xmlChar ** values,
    					 int * terminal)

Extract error information from the regexp execution, the parameter @string will be updated with the value pushed and not accepted, the parameter @values must point to an array of @nbval string pointers on return nbval will contain the number of possible strings in that state and the @values array will be updated with them. The string values

`exec`: | a regexp execution context generating an error
`string`: | return value for the error string
`nbval`: | pointer to the number of accepted values IN/OUT
`nbneg`: | return number of negative transitions
`values`: | pointer to the array of acceptable values
`terminal`: | return value if this was a terminal state
`Returns`: | will be freed with the @exec context and don't need to be deallocated. Returns: 0 in case of success or -1 in case of error.

### xmlRegExecNextValues ()

    int	xmlRegExecNextValues		(xmlRegExecCtxtPtr exec,
    					 int * nbval,
    					 int * nbneg,
    					 xmlChar ** values,
    					 int * terminal)

Extract information from the regexp execution, the parameter @values must point to an array of @nbval string pointers on return nbval will contain the number of possible strings in that state and the @values array will be updated with them. The string values

`exec`: | a regexp execution context
`nbval`: | pointer to the number of accepted values IN/OUT
`nbneg`: | return number of negative transitions
`values`: | pointer to the array of acceptable values
`terminal`: | return value if this was a terminal state
`Returns`: | will be freed with the @exec context and don't need to be deallocated. Returns: 0 in case of success or -1 in case of error.

### xmlRegExecPushString ()

    int	xmlRegExecPushString		(xmlRegExecCtxtPtr exec,
    					 const xmlChar * value,
    					 void * data)

Push one input token in the execution context

`exec`: | a regexp execution context or NULL to indicate the end
`value`: | a string token input
`data`: | data associated to the token to reuse in callbacks
`Returns`: | 1 if the regexp reached a final state, 0 if non-final, and a negative value in case of error.

### xmlRegExecPushString2 ()

    int	xmlRegExecPushString2		(xmlRegExecCtxtPtr exec,
    					 const xmlChar * value,
    					 const xmlChar * value2,
    					 void * data)

Push one input token in the execution context

`exec`: | a regexp execution context or NULL to indicate the end
`value`: | the first string token input
`value2`: | the second string token input
`data`: | data associated to the token to reuse in callbacks
`Returns`: | 1 if the regexp reached a final state, 0 if non-final, and a negative value in case of error.

### xmlRegFreeExecCtxt ()

    void	xmlRegFreeExecCtxt		(xmlRegExecCtxtPtr exec)

Free the structures associated to a regular expression evaluation context.

`exec`: | a regular expression evaluation context

### xmlRegFreeRegexp ()

    void	xmlRegFreeRegexp		(xmlRegexpPtr regexp)

Free a regexp

`regexp`: | the regexp

### xmlRegNewExecCtxt ()

    xmlRegExecCtxtPtr	xmlRegNewExecCtxt	(xmlRegexpPtr comp,
    						 xmlRegExecCallbacks callback,
    						 void * data)

Build a context used for progressive evaluation of a regexp.

`comp`: | a precompiled regular expression
`callback`: | a callback function used for handling progresses in the automata matching phase
`data`: | the context data associated to the callback in this context
`Returns`: | the new context

### xmlRegexpCompile ()

    xmlRegexpPtr	xmlRegexpCompile	(const xmlChar * regexp)

Parses a regular expression conforming to XML Schemas Part 2 Datatype Appendix F and builds an automata suitable for testing strings against that regular expression

`regexp`: | a regular expression string
`Returns`: | the compiled expression or NULL in case of error

### xmlRegexpExec ()

    int	xmlRegexpExec			(xmlRegexpPtr comp,
    					 const xmlChar * content)

Check if the regular expression generates the value

`comp`: | the compiled regular expression
`content`: | the value to check against the regular expression
`Returns`: | 1 if it matches, 0 if not and a negative value in case of error

### xmlRegexpIsDeterminist ()

    int	xmlRegexpIsDeterminist		(xmlRegexpPtr comp)

Check if the regular expression is determinist

`comp`: | the compiled regular expression
`Returns`: | 1 if it yes, 0 if not and a negative value in case of error

### xmlRegexpPrint ()

    void	xmlRegexpPrint			(FILE * output,
    					 xmlRegexpPtr regexp)

Print the content of the compiled regular expression

`output`: | the file for the output debug
`regexp`: | the compiled regexp