Package Ctx APIs for C++

2 Package Ctx APIs for C++

The XML context-related types and interfaces are represented in the Ctx namespace. These include Ctxdatatypes, MemAllocatormethods, and TCtx methods.

Ctx Datatypes

Table 2-1 summarizes the datatypes of the Ctx package.

Table 2-1 Summary of Datatypes; Ctx Package

Datatype	Description
encoding	A single supported encoding.
encodings	An array of encodings.

encoding

A single supported encoding.

Definition

typedef struct encoding {
   oratext *encname;
   oratext *encvalue;
} encoding;

encodings

An array of encodings.

Definition

typedef struct encodings {
   unsigned num;
   encoding *enc; 
} encodings;

MemAllocator Interface

Table 2-2 summarizes the methods available through the MemAllocator interface.

Table 2-2 Summary of MemAllocator Methods; Ctx Package

Function	Summary
alloc()	Allocates memory of given size.
dealloc()	Deallocate memory pointed to by the argument.
~MemAllocator()	Virtual destructor - interface level handle to actual destructors.

alloc()

This is a virtual member function that defines a prototype for user defined allocator functions

Syntax

virtual void* alloc(
   ub4 size) = 0;

Parameter	Description
size	memory size

dealloc()

This is a virtual member function that defines a prototype for user defined deallocator functions. Such deallocators are supposed to deallocate memory allocated by the alloc member functions

Syntax

virtual void dealloc(
   void* ptr) = 0;

Parameter	Description
ptr	pointer to previously allocated memory

~MemAllocator()

It provides an interface level handle to actual destructors that can be invoked without knowing their names or implementations

Syntax

virtual ~MemAllocator() {}

TCtx Interface

Table 2-3 summarizes the methods available through the TCtx interface.

Table 2-3 Summary of TCtx Methods; Ctx Package

Function	Summary
TCtx()	Class constructor.
getEncoding()	Get data encoding in use by XML context.
getErrHandler()	Get Error Handler provided by the user.
getMemAllocator()	Get memory allocator.
isSimple()	Get a flag that indicates if data encoding is simple.
isUnicode()	Get a flag indicating if data encoding is Unicode.
~TCtx()	Destructor - clears space and destroys the implementation.

TCtx()

TCtx constructor. It throws XmlException if it fails to create a context object.

Syntax	Description
TCtx() throw (XMLException)	This constructor creates the context object and initializes it with default values of parameters.
TCtx( oratext* name, ErrorHandler* errh = NULL, MemAllocator* memalloc = NULL, encodings* encs = NULL) throw (XMLException)	This constructor creates the context object and initializes it with parameter values provided by the user.
TCtx( oratext* name, up4 inpblksize, ErrorIfs* errh = NULL, MemAllocator* memalloc = NULL, encodings* encs = NULL) throw (XMLException)	This constructor creates the context object and initializes it with parameter values provided by the user. Takes an additional parameter for memory block size from input source.

Parameter	Description
name	user defined name of the context
errh	user defined error handler
memalloc	user defined memory allocator
encs	user specified encodings
inpblksize	memory block size for input source

Returns

(TCtx) Context object

getEncoding()

Returns data encoding in use by XML context. Ordinarily, the data encoding is chosen by the user, so this function is not needed. However, if the data encoding is not specified, and allowed to default, this function can be used to return the name of that default encoding.

Syntax

oratext* getEncoding() const;

Returns

(oratext *) name of data encoding

getErrHandler()

This member functions returns Error Handler provided by the user when the context was created, or NULL if none were provided.

Syntax

ErrorHandler* getErrHandler() const;

Returns

(ErrorHandler *) Pointer to the Error Handler object, or NULL

getMemAllocator()

This member function returns memory allocator provided by the user when the context was created, or default memory allocator. It is important that this memory allocator is used for all C level memory allocations

Syntax

MemAllocator* getMemAllocator() const;

Returns

(MemAllocator*) Pointer to the memory allocator object

isSimple()

Returns a flag saying whether the context's data encoding is "simple", single-byte for each character, like ASCII or EBCDIC.

Syntax

boolean isSimple() const;

Returns

(boolean) TRUE of data encoding is "simple", FALSE otherwise

isUnicode()

Returns a flag saying whether the context's data encoding is Unicode, UTF-16, with two-byte for each character.

Syntax

boolean isUnicode() const;

Returns

(boolean) TRUE if data encoding is Unicode, FALSE otherwise

~TCtx()

Destructor - should be called by the user the context object is no longer needed

Syntax

~Tctx();