8 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

See Also:

Schema Interface

Table 8-1 summarizes the methods available through the Schema interface.

Table 8-1 Summary of Schema Methods

Function	Summary
XmlSchemaClean()	Cleans up loaded schemas in a schema context and recycle the schema context.
XmlSchemaCreate()	Creates and returns a schema context.
XmlSchemaDestroy()	Destroys a schema context.
XmlSchemaErrorWhere()	Returns the location where an error occurred.
XmlSchemaLoad()	Loads a schema document.
XmlSchemaLoadedList()	Returns the size and/or list of loaded schema documents.
XmlSchemaSetErrorHandler()	Sets an error message handler and its associated context in a schema context
XmlSchemaSetValidateOptions()	Sets option(s) to be used in the next validation session.
XmlSchemaTargetNamespace()	Returns target namespace of a given schema document.
XmlSchemaUnload()	Unloads a schema document.
XmlSchemaValidate()	Validates an element node against a schema.
XmlSchemaVersion()	Returns 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

See Also:

XmlSchemaCreate(), XmlSchemaDestroy()

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

See Also:

XmlSchemaCreate()

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

See Also:

XmlSchemaSetErrorHandler()

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

See Also:

XmlSchemaLoad(), XmlSchemaUnload()

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

See Also:

XmlSchemaValidate()

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

See Also:

XmlSchemaLoadedList()

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

See Also:

XmlSchemaLoad(), XmlSchemaLoadedList()

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

See Also:

XmlSchemaSetValidateOptions()

XmlSchemaVersion()

Return the version of this schema implementation.

Syntax

oratext *XmlSchemaVersion();

Returns

(oratext *) version string [compiler encoding]