Cartridge Services — Maintaining Context

Table 20-3 lists the maintaining context functions that are described in this section.

Table 20-3 Maintaining Context Functions

Function	Purpose
"OCIContextClearValue()"	Remove the value stored in the context
"OCIContextGenerateKey()"	Return a unique 4-byte value each time it is called
"OCIContextGetValue()"	Return the value stored in the context
"OCIContextSetValue()"	Save a value (or address) for a particular duration

OCIContextClearValue()

Purpose

Removes the value that is stored in the context associated with the given key (by calling OCIContextSetValue()).

Syntax

sword OCIContextClearValue( void     *hndl, 
                            OCIError *err, 
                            ub1      *key, 
                            ub1      keylen );

Parameters

hndl (IN): The OCI environment or user session handle.
err (IN): The error handle.
key (IN): Unique key value.
keylen (IN): Length of the key. Maximum is 64 bits.

Comments

An error is returned when a nonexistent key is passed.

Returns

If the operation succeeds, the function returns OCI_SUCCESS.
If the operation fails, the function returns OCI_ERROR.

OCIContextGenerateKey()

Purpose

Returns a unique, 4-byte value each time it is called.

Syntax

sword OCIContextGenerateKey( void     *hndl, 
                             OCIError *err, 
                             ub4      *key );

Parameters

hndl (IN): The OCI environment or user session handle.
err (IN): The error handle.
key (IN): Unique key value.

Comments

This value is unique for each session.

Returns

If the operation succeeds, the function returns OCI_SUCCESS.
If the operation fails, the function returns OCI_ERROR.

OCIContextGetValue()

Purpose

Returns the value that is stored in the context associated with the given key (by calling OCIContextSetValue()).

Syntax

sword OCIContextGetValue( void       *hndl, 
                          OCIError   *err, 
                          ub1        *key, 
                          ub1        keylen, 
                          void       **ctx_value );

Parameters

hndl (IN): The OCI environment or user session handle.
err (IN): The error handle.
key (IN): Unique key value.
keylen (IN): Length of the key. Maximum is 64 bits.
ctx_value (IN): Pointer to the value stored in the context (NULL if no value was stored).

Comments

For ctx_value, a pointer to a preallocated pointer for the stored context to be returned is required.

Returns

If the operation succeeds, the function returns OCI_SUCCESS.
If the operation fails, the function returns OCI_ERROR.

OCIContextSetValue()

Purpose

Saves a value (or address) for a particular duration.

Syntax

sword OCIContextSetValue( void        *hndl, 
                          OCIError    *err, 
                          OCIDuration duration, 
                          ub1         *key, 
                          ub1         keylen, 
                          void        *ctx_value );

Parameters

hndl (IN)

The OCI environment or user session handle.

err (IN)

The error handle.

duration (IN)

One of these values (a previously created user duration):

OCI_DURATION_STATEMENT

OCI_DURATION_SESSION

key (IN)

Unique key value.

keylen (IN)

Length of the key. Maximum is 64 bits.

ctx_value (IN)

Pointer that is saved in the context.

Comments

The context value being stored must be allocated out of memory of duration greater than or equal to the duration being passed in. The key being passed in should be unique in this session. Trying to save a context value under the same key and duration again results in overwriting the old context value with the new one. Typically, a client allocates a structure, stores its address in the context using this call, and gets this address in a separate call using OCIContextGetValue(). The (key, value) association can be explicitly removed by calling OCIContextClearValue(), or else it goes away at the end of the duration.

Returns

If the operation succeeds, the function returns OCI_SUCCESS.
If the operation fails, the function returns OCI_ERROR.