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15 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:

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:

  1. Create/Use an XML meta context object.

    xctx = XmlCreate(,...);

  2. Create/Use an XSLT Compiler object.

    comp = XmlXvmCreateComp(xctx);

  3. Compile an XSLT stylesheets and cache the result bytecode.

    code = XmlXvmCompileFile(comp, xslFile, baseuri, flags, );

  4. 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);

  5. Set a stylesheet bytecode to the XSLTVM object.

    len = XmlXvmGetBytecodeLength(code, ); err = XmlXvmSetBytecodeBuffer(vm, code, len);

  6. Transform an instance XML document.

    err = XmlXvmTransformFile(vm, xmlFile, baseuri);

  7. Clean.

    XmlXvmDestroy(vm);

    XmlXvmDestroyComp(comp);

    XmlDestroy(xctx);


XSLTC Interface

Table 15-1 summarizes the methods available through the XSLTVM Interface.

Table 15-1 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:

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:

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 *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:

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 *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:

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 *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


XmlXvmDestroyComp()

Destroys an XSLT compiler object

Syntax

void XmlXvmDestroyComp(
   xmlxvmcomp *comp);
Parameter In/Out Description
comp
IN
XSLT compiler object


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 15-2 summarizes the methods available through the XSLTVM Interface.

Table 15-2 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


XmlXvmCreate()

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

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()

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.


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.