16 Package XSLTVM APIs for C

Package XSLTVM implements the XSL Transformation (XSLT) language as specified in W3C Recommendation 16 November 1999. The XSLTVM package contains two interfaces.

This chapter contains the following sections:

Using XSLTVM
XSLTC Interface
XSLTVM Interface

See Also:

Using XSLTVM

XSLT Virtual Machine is the software implementation of a "CPU" designed to run compiled XSLT code. A concept of virtual machine assumes a compiler compiling XSLT stylesheets to a sequence of byte codes or machine instructions for the "XSLT CPU". The byte-code program is a platform-independent sequence of 2-byte units. It can be stored, cached and run on different XSLTVM. The XSLTVM uses the bytecode programs to transform instance XML documents. This approach clearly separates compile (design)-time from run-time computations and specifies a uniform way of exchanging data between instructions.

A typical scenario of using the package APIs has the following steps:

Create/Use an XML meta context object.

xctx = XmlCreate(,...);
Create/Use an XSLT Compiler object.

comp = XmlXvmCreateComp(xctx);
Compile an XSLT stylesheets and cache the result bytecode.

code = XmlXvmCompileFile(comp, xslFile, baseuri, flags, );
Create/Use an XSLTVM object. The explicit stack size setting are needed when XSLTVM terminates with "... Stack Overflow" message or when smaller memory footprints are required (see XmlXvmCreate).

vm = XmlXvmCreate(xctx, "StringStack", 32, "NodeStack", 24, NULL);
Set a stylesheet bytecode to the XSLTVM object.

len = XmlXvmGetBytecodeLength(code, ); err = XmlXvmSetBytecodeBuffer(vm, code, len);
Transform an instance XML document.

err = XmlXvmTransformFile(vm, xmlFile, baseuri);
Clean.

XmlXvmDestroy(vm);

XmlXvmDestroyComp(comp);

XmlDestroy(xctx);

XSLTC Interface

Table 16-1 summarizes the methods available through the XSLTVM Interface.

Table 16-1 Summary of XSLTC Methods; XSLTVM Package

Function	Summary
XmlXvmCompileBuffer()	Compile an XSLT stylesheet from buffer into bytecode.
XmlXvmCompileDom()	Compile an XSLT stylesheet from DOM into bytecode.
XmlXvmCompileFile()	Compile an XSLT stylesheet from file into bytecode.
XmlXvmCompileURI()	Compile XSLT stylesheet from URI into byte code.
XmlXvmCompileXPath()	Compile an XPath expression.
XmlXvmCreateComp()	Create an XSLT compiler.
XmlXvmDestroyComp()	Destroy an XSLT compiler object.
XmlXvmGetBytecodeLength()	Returns the bytecode length.

XmlXvmCompileBuffer()

Compile an XSLT stylesheet from buffer into bytecode. Compiler flags could be one or more of the following:

XMLXVM_DEBUG forces compiler to include debug information into the bytecode
XMLXVM_STRIPSPACE is equivalent to <xsl:strip-space elements="*"/>.

The generated bytecode resides in a compiler buffer which is freed when next stylesheet is compiled or when compiler object is deleted. Hence, if the bytecode is to be reused it should be copied into another location.

Syntax

ub2 *XmlXvmCompileBuffer(
   xmlxvmcomp *comp,
   oratext *buffer,
   ub4 length, 
   oratext *baseURI,
   xmlxvmflag flags,
   xmlerr *error);

Parameter	In/Out	Description
comp	IN	compiler object
buffer	IN	pointer to buffer containing stylesheet document
length	IN	length of the stylesheet document in bytes
baseuri	IN	base URI of the document
flags	IN	flags for the current compilation
error	OUT	returned error code

Returns

(ub2 *) bytecode or NULL on error

XmlXvmCompileDom()

Compile an XSLT stylesheet from DOM into bytecode. Compiler flags could be one or more of the following:

XMLXVM_DEBUG forces compiler to include debug information into the bytecode
XMLXVM_STRIPSPACE is equivalent to <xsl:strip-space elements="*"/>.

Syntax

ub2 *XmlXvmCompileDom(
   xmlxvmcomp *comp,
   xmldocnode *root,
   xmlxvmflag flags,
   xmlerr *error);

Parameter	In/Out	Description
comp	IN	compiler object
rooot	IN	root element of the stylesheet DOM
flags	IN	flags for the current compilation
error	OUT	returned error code

Returns

(ub2 *) bytecode or NULL on error

XmlXvmCompileFile()

Compile XSLT stylesheet from file into bytecode. Compiler flags could be one or more of the following:

XMLXVM_DEBUG forces compiler to include debug information into the bytecode
XMLXVM_STRIPSPACE is equivalent to <xsl:strip-space elements="*"/>.

Syntax

ub2 *XmlXvmCompileFile(
   xmlxvmcomp *comp, 
   oratext *path,
   oratext *baseURI,
   xmlxvmflag flags,
   xmlerr *error);

Parameter	In/Out	Description
comp	IN	compiler object
path	IN	path of XSL stylesheet file
baseuri	IN	base URI of the document
flags	IN	flags for the current compilation
error	OUT	returned error code

Returns

(ub2 *) bytecode or NULL on error

XmlXvmCompileURI()

Compile XSLT stylesheet from URI into bytecode. Compiler flags could be one or more of the following:

XMLXVM_DEBUG forces compiler to include debug information into the bytecode
XMLXVM_STRIPSPACE is equivalent to <xsl:strip-space elements="*"/>.

Syntax

ub2 *XmlXvmCompileURI(
   xmlxvmcomp *comp, 
   oratext *uri, 
   xmlxvmflag flags, 
   xmlerr *error);

Parameter	In/Out	Description
comp	IN	compiler object
uri	IN	URI of the file that contains the XSL stylesheet
flags	IN	flags for the current compilation
error	OUT	returned error code

Returns

(ub2 *) bytecode or NULL on error

XmlXvmCompileXPath()

Compiles an XPath expression. The optional pfxmap is used to map namespace prefixes to URIs in the XPath expression. It is an array of prefix, URI values, ending in NULL, and so on.

Syntax

ub2 *XmlXvmCompileXPath(
   xmlxvmcomp *comp, 
   oratext *xpath,
   oratext **pfxmap,
   xmlerr *error);

Parameter	In/Out	Description
comp	IN	compiler object
xpath	IN	XPath expression
pfxmap	IN	array of prefix-URI mappings
error	OUT	returned error code

Returns

(ub2 *) XPath expression bytecode or NULL on error

XmlXvmCreateComp()

Create an XSLT compiler object. The XSLT compiler is used to compile XSLT stylesheets into bytecode.

Syntax

xmlxvmcomp *XmlXvmCreateComp(
   xmlctx *xctx);

Parameter	In/Out	Description
xctx	IN	XML context

Returns

(xmlxvmcomp *) XSLT compiler object, or NULL on error

See Also:

XmlXvmDestroyComp()

Destroys an XSLT compiler object

Syntax

void XmlXvmDestroyComp(
   xmlxvmcomp *comp);

Parameter	In/Out	Description
comp	IN	XSLT compiler object

See Also:

XmlXvmCreateComp()

XmlXvmGetBytecodeLength()

The bytecode length is needed when the bytecode is to be copied or when it is set into XSLTVM.

Syntax

ub4 XmlXvmGetBytecodeLength(
   ub2 *bytecode,
   xmlerr *error);

Parameter	In/Out	Description
bytecode	IN	bytecode buffer
error	OUT	returned error code

Returns

(ub4) The bytecode length in bytes.

XSLTVM Interface

Table 16-2 summarizes the methods available through the XSLTVM Interface.

Table 16-2 Summary of XSLTVM Methods; Package XSLTVM

Function	Summary
XMLXVM_DEBUG_F()	XMLXSLTVM debug function.
XmlXvmCreate()	Create an XSLT virtual machine.
XmlXvmDestroy()	Destroys an XSLT virtual machine.
XmlXvmEvaluateXPath()	Evaluate already-compiled XPath expression.
XmlXvmGetObjectBoolean()	Get boolean value of XPath object.
XmlXvmGetObjectNSetNode()	Get node from nodeset type XPathobject.
XmlXvmGetObjectNSetNum()	Get number of nodes in nodeset type XPathobject.
XmlXvmGetObjectNumber()	Get number from XPath object.
XmlXvmGetObjectString()	Get string from XPath object.
XmlXvmGetObjectType()	Get XPath object type.
XmlXvmGetOutputDom()	Returns the output DOM.
XmlXvmResetParams()	Resets the stylesheet top level text parameters.
XmlXvmSetBaseURI()	Sets the base URI for the XLTVM.
XmlXvmSetBytecodeBuffer()	Set the compiled bytecode.
XmlXvmSetBytecodeFile()	Set the compiled byte code from file.
XmlXvmSetBytecodeURI()	Set the compiled bytecode.
XmlXvmSetDebugFunc()	Set a callback function for debugging.
XmlXvmSetOutputDom()	Sets the XSLTVM to output document node.
XmlXvmSetOutputEncoding()	Sets the encoding for the XSLTVM output.
XmlXvmSetOutputSax()	Sets XSLTVM to output SAX.
XmlXvmSetOutputStream()	Set the XSLTVM output to a user-defined stream.
XmlXvmSetTextParam()	Set the stylesheet top-level text parameter.
XmlXvmTransformBuffer()	Run compiled XSLT stylesheet on XML document in memory.
XmlXvmTransformDom()	Run compiled XSLT stylesheet on XML document as DOM.
XmlXvmTransformFile()	Run compiled XSLT stylesheet on XML document in file.
XmlXvmTransformURI()	Run compiled XSLT stylesheet on XML document from URI.

XMLXVM_DEBUG_F()

Debug callback function for XSLT VM.

Syntax

#define XMLXVM_DEBUG_F(func, line, file, obj, n)
void func(
   ub2 line,
   oratext *file,
   xvmobj *obj,
   ub4 n)

Parameter	In/Out	Description
line	IN	source stylesheet line number
file	IN	stylesheet filename
obj	IN	current VM object
n	IN	index of current node

See Also:

XmlXvmSetDebugFunc()

XmlXvmCreate()

Create an XSLT virtual machine. Zero or more of the following XSLTVM properties could be set by using this API:

"VMStack", size sets the size[Kbyte] of the main VM stack; default size is 4K.
"NodeStack", size sets the size[Kbyte] of the node-stack; default size is 16K.
"StringStack", size sets the size[Kbyte] of the string-stack; default size is 64K.

If the stack size is not specified the default size is used. The explicit stack size setting is needed when XSLTVM terminates with "Stack Overflow" message or when smaller memory footprints are required.

Syntax

xmlxvm *XmlXvmCreate(
   xmlctx *xctx, 
   list);

Parameter	In/Out	Description
xctx	IN	XML context
list	IN	`NULL`-terminated list of properties to set; can be empty

Returns

(xmlxvm *) XSLT virtual machine object, or NULL on error

See Also:

XmlXvmDestroy()

Destroys an XSLT virtual machine

Syntax

void XmlXvmDestroy(
   xmlxvm *vm);

Parameter	In/Out	Description
vm	IN	VM object

See Also:

XmlXvmCreate()

XmlXvmEvaluateXPath()

Evaluate already-compiled XPath expression

Syntax

xvmobj *XmlXvmEvaluateXPath(
   xmlxvm *vm, 
   ub2 *bytecode, 
   ub4 ctxpos,
   ub4 ctxsize,
   xmlnode *ctxnode);

Parameter	In/Out	Description
vm	IN	XSLTVM object
bytecode	IN	XPath expression bytecode
ctxpos	IN	current context position
ctxsize	IN	current context size
ctxnode	IN	current context node

Returns

(xvmobj *) XPath object

XmlXvmGetObjectBoolean()

Get boolean value of XPath object

Syntax

boolean XmlXvmGetObjectBoolean(
   xvmobj *obj);

Parameter	In/Out	Description
obj	IN	object

Returns

(boolean) value of an XPath object

XmlXvmGetObjectNSetNode()

Get node from nodeset-type XPath object

Syntax

xmlnode *XmlXvmGetObjectNSetNode(
   xvmobj *obj,
   ub4 i);

Parameter	In/Out	Description
obj	IN	object
i	IN	node index in nodeset

Returns

(xmlnode *) The object type or values.

XmlXvmGetObjectNSetNum()

Get number of nodes in nodeset-type XPath object

Syntax

ub4 XmlXvmGetObjectNSetNum(
   xvmobj *obj);

Parameter	In/Out	Description
obj	IN	object

Returns

(ub4) number of nodes in nodeset

XmlXvmGetObjectNumber()

Get number from XPath object.

Syntax

double XmlXvmGetObjectNumber(
   xvmobj *obj);

Parameter	In/Out	Description
obj	IN	object

Returns

(double) number

XmlXvmGetObjectString()

Get string from XPath object.

Syntax

oratext *XmlXvmGetObjectString(
   xvmobj *obj);

Parameter	In/Out	Description
obj	IN	object

Returns

(oratext *) string

XmlXvmGetObjectType()

Get XPath object type

Syntax

xmlxvmobjtype XmlXvmGetObjectType(
   xvmobj *obj);

Parameter	In/Out	Description
obj	IN	object

Returns

(xmlxvmobjtype) type-code for object

XmlXvmGetOutputDom()

Returns the root node of the result DOM tree (if any). XmlXvmSetOutputDom has to be used before transformation to set the VM to output a DOM tree (the default VM output is a stream).

Syntax

xmlfragnode *XmlXvmGetOutputDom(
   xmlxvm *vm);

Parameter	In/Out	Description
vm	IN	VM object

Returns

(xmlfragnode *) output DOM, or NULL in a case of SAX or Stream output.

See Also:

XmlXvmSetOutputDom()

XmlXvmResetParams()

Resets the stylesheet top-level parameters with their default values.

Syntax

void XmlXvmResetParams(
   xmlxvm *vm);

Parameter	In/Out	Description
vm	IN	VM object

XmlXvmSetBaseURI()

Sets the base URI for the XSLTVM. The baseuri is used by VM to the compose the path XML documents to be loaded for transformation using document or XmlXvmTransformFile.

Syntax

xmlerr XmlXvmSetBaseURI(
   xmlxvm *vm, 
   oratext *baseuri);

Parameter	In/Out	Description
vm	IN	VM object
baseuri	IN	VM base URI for reading and writing documents

Returns

(xmlerr) error code.

XmlXvmSetBytecodeBuffer()

Set the compiled bytecode from buffer. Any previously set bytecode is replaced. An XML transformation can't be performed if the stylesheet bytecode is not set. The VM doesn't copy the bytecode into internal buffer, hence the it shouldn't be freed before VM finishes using it.

Syntax

xmlerr XmlXvmSetBytecodeBuffer(
   xmlxvm *vm, 
   ub2 *buffer, 
   size_t buflen);

Parameter	In/Out	Description
vm	IN	XSLT VM context
buffer	IN	user's buffer
buflen	IN	size of buffer, in bytes

Returns

(xmlerr) numeric error code, XMLERR_OK [0] on success

XmlXvmSetBytecodeFile()

Set the compiled bytecode from file. Any previously set bytecode is replaced. An XML transformation can't be performed if the stylesheet bytecode is not set.

Syntax

xmlerr XmlXvmSetBytecodeFile(
   xmlxvm *vm,
   oratext *path);

Parameter	In/Out	Description
vm	IN	XSLT VM context
path	IN	path of bytecode file

Returns

(xmlerr) numeric error code, XMLERR_OK [0] on success

XmlXvmSetBytecodeURI()

Set the compiled bytecode from URI. Any previously set bytecode is replaced. An XML transformation can't be performed if the stylesheet bytecode is not set.

Syntax

xmlerr XmlXvmSetBytecodeURI(
   xmlxvm *vm,
   oratext *uri);

Parameter	In/Out	Description
vm	IN	XSLT VM context
uri	IN	path of bytecode file

Returns

(xmlerr) numeric error code, XMLERR_OK [0] on success

XmlXvmSetDebugFunc()

The user callback function is invoked by VM every time the execution reaches a new line in the XSLT stylesheet. The VM passes to the user the stylesheet file name, the line number, the current context nodes-set and the current node index in the node-set. IMPORTANT - the stylesheet has to be compiled with flag XMLXVM_DEBUG.

Syntax

#define XMLXVM_DEBUG_FUNC(func)
void func (ub2 line, oratext *filename, xvmobj *obj, ub4 n)
xmlerr XmlXvmSetDebugFunc(
   xmlxvm *vm,
   XMLXVM_DEBUG_FUNC(debugcallback));

Parameter	In/Out	Description
vm	IN	XSLT VM context
func	IN	callback function

Returns

(xmlerr) numeric error code, XMLERR_OK [0] on success

XmlXvmSetOutputDom()

Sets the XSLTVM to output DOM. If xmldocnode==NULL, then the result DOM tree belongs to the VM object and is deleted when a new transformation is performed or when the VM object is deleted. If the result DOM tree is to be used for longer period of time then an xmldocnode has to be created and set to the VM object.

Syntax

xmlerr XmlXvmSetOutputDom(
   xmlxvm *vm,
   xmldocnode *doc);

Parameter	In/Out	Description
vm	IN	VM object
doc	IN	empty document

Returns

(xmlerr) error code

XmlXvmSetOutputEncoding()

Sets the encoding for the XSLTVM stream output. If the input (data) encoding is different from the one set by this APIs then encoding conversion is performed. This APIs overrides the encoding set in the XSLT stylesheet (if any).

Syntax

xmlerr XmlXvmSetOutputEncoding(
   xmlxvm *vm, 
   oratext *encoding);

Parameter	In/Out	Description
vm	IN	VM object
encoding	IN	output encoding

Returns

(xmlerr) error code.

XmlXvmSetOutputSax()

Set XSLTVM to output SAX. If the SAX callback interface object is provided the VM outputs the result document in a form of SAX events using the user specified callback functions.

Syntax

xmlerr XmlXvmSetOutputSax(
   xmlxvm *vm,
   xmlsaxcb *saxcb, 
   void *saxctx);

Parameter	In/Out	Description
vm	IN	VM object
saxcb	IN	SAX callback object
saxctx	IN	SAX context

Returns

(xmlerr) error code

XmlXvmSetOutputStream()

Set the XSLTVM output to a user-defined stream. The default XSLTVM output is a stream. This APIs overrides the default stream with user specified APIs for writing.

Syntax

xmlerr XmlXvmSetOutputStream(
   xmlxvm *vm,
   xmlostream *ostream);

Parameter	In/Out	Description
vm	IN	VM object
ostream	IN	stream object

Returns

(xmlerr) error code.

XmlXvmSetTextParam()

Set the stylesheet top-level text parameter. The parameter value set in the XSLT stylesheet is overwritten. Since the top-level parameters are reset with stylesheet values after each transformation, this APIs has to be called again.

Syntax

xmlerr XmlXvmSetTextParam(
   xmlxvm *vm,
   oratext *name,
   oratext *value);

Parameter	In/Out	Description
vm	IN	VM object
name	IN	name of top-level parameter
value	IN	value of top-level parameter

Returns

(xmlerr) error code, XMLERR_SUCC [0] on success.

XmlXvmTransformBuffer()

Run compiled XSLT stylesheet on XML document in memory. The compiled XSLT stylesheet (bytecode) should be set using XmlXvmSetBytecodeXXX prior to this call.

Syntax

xmlerr XmlXvmTransformBuffer(
   xmlxvm *vm,
   oratext *buffer,
   ub4 length,
   oratext *baseURI);

Parameter	In/Out	Description
vm	IN	VM object
buffer	IN	`NULL`-terminated buffer that contains the XML document
length	IN	length of the XML document
baseURI	IN	base URI of XML document

Returns

(xmlerr) error code.

XmlXvmTransformDom()

Run compiled XSLT stylesheet on XML document as DOM. The compiled XSLT stylesheet (bytecode) should be set using XmlXvmSetBytecodeXXX prior to this call.

Syntax

xmlerr XmlXvmTransformDom(
   xmlxvm *vm,
   xmldocnode *root);

Parameter	In/Out	Description
vm	IN	VM object
root	IN	root element of XML document's DOM

Returns

(xmlerr) error code.

XmlXvmTransformFile()

Run compiled XSLT stylesheet on XML document in file. The compiled XSLT stylesheet (bytecode) should be set using XmlXvmSetBytecodeXXX prior to this call.

Syntax

xmlerr XmlXvmTransformFile(
   xmlxvm *vm,
   oratext *path,
   oratext *baseURI);

Parameter	In/Out	Description
vm	IN	VM object
path	IN	path of XML document to transform
baseURI	IN	base URI of XML document

Returns

(xmlerr) error code

XmlXvmTransformURI()

Run compiled XSLT stylesheet on XML document from URI. The compiled XSLT stylesheet (bytecode) should be set using XmlXvmSetBytecodeXXX prior to this call.

Syntax

xmlerr XmlXvmTransformURI(
   xmlxvm *vm, 
   oratext *uri);

Parameter	In/Out	Description
vm	IN	VM object
uri	IN	URI of XML document to transform

Returns

(xmlerr) error code.