an_extfn_value structure

Used to access parameter data from the calling SQL environment.

Syntax

typedef struct an_extfn_value {
    void *           data;
    a_sql_uint32     piece_len;
    union {
        a_sql_uint32 total_len;
        a_sql_uint32 remain_len;
    } len;
    a_sql_data_type  type;
} an_extfn_value;

Properties

data A pointer to the data for this parameter.
piece_len The length of this segment of the parameter. This is less than or equal to total_len.
total_len The total length of the parameter. For strings, this represents the length of the string and does not include a null terminator. This property is set after a call to the get_value callback function. This property is no longer valid after a call to the get_piece callback function.
remain_len When the parameter is obtained in segments, this is the length of the part that has not yet been obtained. This property is set after each call to the get_piece callback function.
type Indicates the type of the parameter. This is one of the Embedded SQL data types such as DT_INT, DT_FIXCHAR, or DT_BINARY. See Embedded SQL data types.

Remarks

Suppose that your external function interface was described using the following SQL statement.

CREATE FUNCTION mystring( IN instr LONG VARCHAR )
RETURNS LONG VARCHAR
EXTERNAL NAME 'mystring@c:\\project\\mystring.dll';

The following code fragment shows how to access the properties for objects of type an_extfn_value. In the example, the input parameter 1 (instr) to this function (mystring) is expected to be a SQL LONGVARCHAR string.

an_extfn_value      arg;

result = extapi->get_value( arg_handle, 1, &arg );
if( result == 0 || arg.data == NULL )
{
    return; // no parameter or parameter is NULL
}

if( arg.type != DT_LONGVARCHAR )
{
    return; // unexpected type of parameter
}

cmd = (char *)malloc( arg.len.total_len + 1 );
offset = 0;
for( ; result != 0; )
{
     if( arg.data == NULL ) break;
     memcpy( &cmd[offset], arg.data, arg.piece_len );
     offset += arg.piece_len;
     cmd[offset] = '\0';
     if( arg.piece_len == 0 ) break;
     result = extapi->get_piece( arg_handle, 1, &arg, offset );
}

an_extfn_value structure

Syntax

Properties

Remarks

See also