16 Package XSLTVM APIs for C

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

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);

comp

IN

buffer

IN

length

IN

baseuri

IN

flags

IN

error

OUT

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="*"/>.

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);

comp

IN

rooot

IN

flags

IN

error

OUT

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="*"/>.

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);

comp

IN

path

IN

baseuri

IN

flags

IN

error

OUT

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="*"/>.

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);

comp

IN

uri

IN

flags

IN

error

OUT

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);

comp

IN

xpath

IN

pfxmap

IN

error

OUT

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);

xctx

IN

Returns

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

XmlXvmDestroyComp()

Destroys an XSLT compiler object

Syntax

void XmlXvmDestroyComp(
   xmlxvmcomp *comp);

comp

IN

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);

bytecode

IN

error

OUT

Returns

(ub4) The bytecode length in bytes.

XSLTVM Interface

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

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)

line

IN

file

IN

obj

IN

n

IN

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);

xctx

IN

list

IN

Returns

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

XmlXvmDestroy()

Destroys an XSLT virtual machine

Syntax

void XmlXvmDestroy(
   xmlxvm *vm);

vm

IN

XmlXvmEvaluateXPath()

Evaluate already-compiled XPath expression

Syntax

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

vm

IN

bytecode

IN

ctxpos

IN

ctxsize

IN

ctxnode

IN

Returns

(xvmobj *) XPath object

XmlXvmGetObjectBoolean()

Get boolean value of XPath object

Syntax

boolean XmlXvmGetObjectBoolean(
   xvmobj *obj);

obj

IN

Returns

(boolean) value of an XPath object

XmlXvmGetObjectNSetNode()

Get node from nodeset-type XPath object

Syntax

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

obj

IN

i

IN

Returns

(xmlnode *) The object type or values.

XmlXvmGetObjectNSetNum()

Get number of nodes in nodeset-type XPath object

Syntax

ub4 XmlXvmGetObjectNSetNum(
   xvmobj *obj);

obj

IN

Returns

(ub4) number of nodes in nodeset

XmlXvmGetObjectNumber()

Get number from XPath object.

Syntax

double XmlXvmGetObjectNumber(
   xvmobj *obj);

obj

IN

Returns

(double) number

XmlXvmGetObjectString()

Get string from XPath object.

Syntax

oratext *XmlXvmGetObjectString(
   xvmobj *obj);

obj

IN

Returns

(oratext *) string

XmlXvmGetObjectType()

Get XPath object type

Syntax

xmlxvmobjtype XmlXvmGetObjectType(
   xvmobj *obj);

obj

IN

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);

vm

IN

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);

vm

IN

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);

vm

IN

baseuri

IN

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);

vm

IN

buffer

IN

buflen

IN

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);

vm

IN

path

IN

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);

vm

IN

uri

IN

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));

vm

IN

func

IN

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);

vm

IN

doc

IN

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);

vm

IN

encoding

IN

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);

vm

IN

saxcb

IN

saxctx

IN

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);

vm

IN

ostream

IN

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);

vm

IN

name

IN

value

IN

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);

vm

IN

buffer

IN

length

IN

baseURI

IN

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);

vm

IN

root

IN

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);

vm

IN

path

IN

baseURI

IN

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);

vm

IN

uri

IN

Returns

(xmlerr) error code.