7 Package Schema APIs for C

This C implementation of the XML schema validator follows the W3C XML Schema specification, rev REC-xmlschema-1-20010502. It implements the required behavior of a schema validator for multiple schema documents to be assembled into a schema. This resulting schema can be used to validate a specific instance document.

For event-based schema validation, see the methods documented in Chapter 4, "Package Event APIs for C".

This chapter contains the following section:


Schema Interface

Table 7-1 summarizes the methods available through the Schema interface.

Table 7-1 Summary of Schema Methods

Function Summary

XmlSchemaClean()

Clean up loaded schemas in a schema context and recycle the schema context.

XmlSchemaCreate()

Create and return a schema context.

XmlSchemaDestroy()

Destroy a schema context.

XmlSchemaErrorWhere()

Returns the location where an error occurred.

XmlSchemaLoad()

Load a schema document.

XmlSchemaLoadedList()

Return the size and/or list of loaded schema documents.

XmlSchemaSetErrorHandler()

Sets an error message handler and its associated context in a schema context

XmlSchemaSetValidateOptions()

Set option(s) to be used in the next validation session.

XmlSchemaTargetNamespace()

Return target namespace of a given schema document.

XmlSchemaUnload()

Unload a schema document.

XmlSchemaValidate()

Validate an element node against a schema.

XmlSchemaVersion()

Return the version of this schema implementation.



XmlSchemaClean()

Clean up loaded schemas in a schema context and recycle the schema context.

Syntax

void XmlSchemaClean(
   xsdctx *sctx);
Parameter In/Out Description
sctx
IN
schema context to be cleaned


XmlSchemaCreate()

Return a schema context to be used in other validator APIs. This needs to be paired with an XmlSchemaDestroy.

Syntax

xsdctx *XmlSchemaCreate(
   xmlctx *xctx, 
   xmlerr *err, 
   list);
Parameter In/Out Description
xctx
IN
XML context
err
OUT
returned error code
list
IN
NULL-terminated list of variable arguments

Returns

(xsdctx *) schema context


XmlSchemaDestroy()

Destroy a schema context and free up all its resources.

Syntax

void XmlSchemaDestroy(
   xsdctx *sctx);
Parameter In/Out Description
sctx
IN
schema context to be freed


XmlSchemaErrorWhere()

Returns the location (line#, path) where an error occurred.

Syntax

xmlerr XmlSchemaErrorWhere(
   xsdctx *sctx, 
   ub4 *line, 
   oratext **path);
Parameter In/Out Description
sctx
IN
schema context
line
IN/OUT
line number where error occurred
path
IN/OUT
URL or filespace where error occurred

Returns

(xmlerr) error code


XmlSchemaLoad()

Load up a schema document to be used in the next validation session. Schema documents can be incrementally loaded into a schema context as long as every loaded schema document is valid. When the last loaded schema turns out to be invalid, you need to clean up the schema context by calling XmlSchemaClean() and reload everything all over again including the last schema with appropriate correction.

Given a schema document, this function converts the DOM representation into an internal schema representation. The schema document can be provided as a URI or directly a DOM representation. In the URI case, this function reads the input stream and builds a DOM representation of the schema before converting it into internal representation. In the DOM case, the application can provide a DOM representation of the schema, which will be used to create the internal schema representation.

Syntax

xmlerr XmlSchemaLoad(
   xsdctx *sctx, 
   oratext *uri, 
   list);
Parameter In/Out Description
sxctx
IN
schema context
uri
IN
URL of schema document; compiler encoding
list
IN
NULL-terminated list of variable arguments

Returns

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


XmlSchemaLoadedList()

Return only the size of loaded schema documents if list is NULL. If list is not NULL, a list of URL pointers are returned in the user-provided pointer buffer. Note that its user's responsibility to provide a buffer with big enough size.

Syntax

ub4 XmlSchemaLoadedList(
   xsdctx *sctx, 
   oratext **list);
Parameter In/Out Description
sctx
IN
schema context
list
IN
address of pointer buffer

Returns

(ub4) list size


XmlSchemaSetErrorHandler()

Sets an error message handler and its associated context in a schema context. To retrieve useful location information on errors, the address of the schema context must be provided in the error handler context.

Syntax

xmlerr XmlSchemaSetErrorHandler(
   xsdctx *sctx, 
   XML_ERRMSG_F(
      (*errhdl), 
      ectx, 
      msg, 
      err), 
   void *errctx);
Parameter In/Out Description
sctx
IN
schema context
errhdl
IN
error message handler
errctx
IN
error handler context

Returns

(xmlerr) error code


XmlSchemaSetValidateOptions()

Set options to be used in the next validation session. Previously set options will remain effective until they are overwritten or reset.

Syntax

xmlerr XmlSchemaSetValidateOptions(
   xsdctx *sctx, 
   list);
Parameter In/Out Description
sctx
IN
schema context
list
IN
NULL-terminated list of variable argument

Returns

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


XmlSchemaTargetNamespace()

Return target namespace of a given schema document identified by its URI. All currently loaded schema documents can be queried. Currently loaded schema documents include the ones loaded through XmlSchemaLoads and the ones loaded through schemaLocation or noNamespaceSchemaLocation hints.

Syntax

oratext *XmlSchemaTargetNamespace(
   xsdctx *sctx, 
   oratext *uri);
Parameter In/Out Description
sctx
IN
XML context
uri
IN
URL of the schema document to be queried

Returns

(oratext *) target namespace string; NULL if given document not


XmlSchemaUnload()

Unload a schema document from the validator. All previously loaded schema documents will remain loaded until they are unloaded. To unload all loaded schema documents, set URI to be NULL (this is equivalent to XmlSchemaClean). Note that all children schemas associated with the given schema are also unloaded. In this implementation, it only support the following scenarios:

  • load, load, ...

  • load, load, load, unload, unload, unload, clean, and then repeat.

It doesn't not support: load, load, unload, load, ....

Syntax

xmlerr XmlSchemaUnload(
   xsdctx *sctx, 
   oratext *uri, 
   list);
Parameter In/Out Description
sctx
IN
schema context
uri
IN
URL of the schema document; compiler encoding
list
IN
NULL-terminated list of variable argument

Returns

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


XmlSchemaValidate()

Validates an element node against a schema. Schemas used in current session consists of all schema documents specified through XmlSchemaLoad and provided as hint(s) through schemaLocation or noNamespaceSchemaLocation in the instance document. After the invocation of this routine, all loaded schema documents remain loaded and can be queried by XmlSchemaLoadedList. However, they will remain inactive. In the next validation session, inactive schema documents can be activated by specifying them through XmlSchemaLoad or providing them as hint(s) through schemaLocation or noNamespaceSchemaLocation in the new instance document. To unload a schema document and all its descendants (documents included or imported in a nested manner), use XmlSchemaUnload.

Syntax

xmlerr XmlSchemaValidate(
   xsdctx *sctx,
   xmlctx *xctx, 
   xmlelemnode *elem);
Parameter In/Out Description
sctx
IN
schema context
xctx
IN
XML top-level context
elem
IN
element node in the doc, to be validated

Returns

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


XmlSchemaVersion()

Return the version of this schema implementation.

Syntax

oratext *XmlSchemaVersion();

Returns

(oratext *) version string [compiler encoding]