How to convert data buffer of type "oracle::occi::OCCI_SQLT_NUM" to double

Question

Hello All,
I am using bulk reading by utilizing 'setDataBuffer()' method call and fetching N records at a time.
It works well for fields of Oracle type VARCHAR, when I set
h5. rs->setDataBuffer(col, buff, oracle::occi::OCCI_SQLT_CHR, size, lens, inds);
and later iterating and interpreting data within 'buff' like this:
h5. char* text = ((char*)buff) + size*i; <-- length is in lens array
When the column's data type is NUMBER however, I am stuck.
Indicating that data type to data buffer works well:
h5. rs->setDataBuffer(col, buff, oracle::occi::OCCI_SQLT_NUM, size, lens, inds);
I would like now to extract a value of c++ double type from that buffer.
But I do not have an idea how to handle data within buff. I suppose it should have NUMBER stored inside in some internal format (just as described in Oracle® C++ Call Interface Programmer's Guide, section 'Description of External Datatypes', NUMBER)
Gestures like casting to double or trying to interpet the buffer's inner as oracle::occi::Number do not produce sensible results.
Could you help me to understand how can I obtain the double value from that buffer in a bulk read?

Answer 1

I have the following code which has been working for me.
showln ("Array Fetch");
sql = "SELECT c1, c2, c3, c4 FROM nd17_otab";
stmt->setSQL ( sql );
OCCIResultSet *rs = stmt->executeQuery();
rs->setDataBuffer (1, num, OCCIINT, sizeof(ub4), lenC1);
rs->setDataBuffer (2, flt, OCCIBFLOAT, sizeof(float), lenC2);
rs->setDataBuffer (3, dbl, OCCIBDOUBLE, sizeof(double), lenC3);
rs->setDataBuffer (4, str, OCCI_SQLT_CHR, CHRS, lenC4);
if ( rs->next(ROWS) )
show ("Number of Rows Fetched: ") << rs->getNumArrayRows () << endl;
showln ("Fetched Records");
for (int j = 0; j < ROWS; j++ )
show ("C1: ") << num[j] << endl;
show ("C2: ") << flt[j] << endl;
show ("C3: ") << dbl[j] << endl;
show ("C4: ") << str[j] << endl;
stmt->closeResultSet(rs);
c1, c2, c3, c4 columns in table nd17_otab are of type NUMBER, BINARY_FLOAT, BINARY_DOUBLE & VARCHAR2