Re: binary data type in Pro*C...

From: Thomas Kyte <tkyte_at_us.oracle.com>
Date: 1998/03/17
Message-ID: <350face6.10353978_at_192.86.155.100>#1/1

A copy of this was sent to kwtse_at_cs.hku.hk (Tse Ka Wai (CS)) (if that email address didn't require changing) On 17 Mar 1998 04:48:03 GMT, you wrote:

>
>in Oracle database there is a data type to hold binary data called "raw".
>in Pro*C, what kind of C datatype should i use to hold that kind of data
>returned in a SQL statement such that minimum conversion is needed?
>
>thanks in advance.
>
>
>tse ka wai CS3 --> ?

Here is an example, there is no conversion with this datatype:

static void process()
{

/*
 * This is the data structure we will use with our LONG RAWs.  We will
 * always use pointers to this structure as we don't know how big we need
 * until runtime.  Will use malloc to allocate storage on the fly.
 */
 

typedef struct TAGmy_raw
{

	long			len;
	unsigned char	arr[1];
}
	my_raw;

/*
 * Use type equivalencing to tell Oracle that the C type "my_raw" is
 * equivalent to the Oracle type LONG VARRAW and can hold upto 100k
 * bytes of data (we will never allocate that much here, just an upper

• bound, could be MUCH higher (eg: 10,000,000,000) */

EXEC SQL BEGIN DECLARE SECTION;
EXEC SQL TYPE my_raw IS LONG VARRAW(100000) REFERENCE; my_raw * buffer;
EXEC SQL END DECLARE SECTION;

long	size = 100000;
int		i;

	EXEC SQL WHENEVER SQLERROR DO sqlerror_hard();

	printf( "EXEC SQL CREATE TABLE TEST_BLOB ( X LONG RAW );\n" );
	EXEC SQL CREATE TABLE TEST_BLOB ( X LONG RAW );

	/*
	 * we will allocate a little over 99k of space
	 */
	buffer = (my_raw *)malloc( size+sizeof(my_raw) );

	/*
	 * fill it up with every possible byte value from 0..254
	 */
	for( i = 0; i < size; i++ )
		buffer->arr[i] = i % 255;

	/*
	 * Just like a varchar, set the length field
	 */
	buffer->len = size;

	printf( "INSERT INTO TEST_BLOB\n" );
	EXEC SQL INSERT INTO TEST_BLOB ( X ) values ( :buffer );

	/*
	 * commit the changes
	 */
	printf("EXEC SQL COMMIT WORK;\n" );
	EXEC SQL COMMIT WORK;

	/*
	 * Now, ZERO out the buffer so when we fetch, we know that the buffer
	 * was NOT equal to what it was on the insert.  Just to *prove* that
	 * the fetch got back the data we inserted
	 */
	memset( buffer->arr, 0, size );

	/*
	 * Select out the data
	 */
	printf( " SELECT X INTO :buffer FROM TEST_BLOB;\n" );
	EXEC SQL SELECT X
			 INTO :buffer
			 FROM TEST_BLOB;

	/* 
	 * show what size we got 
	 */
	printf( "The Length = %ld\n", buffer->len );

	/*
	 * Check each character to make sure it is what we inserted
	 */
	for( i = 0; i < size; i++ )
		if ( buffer->arr[i] != i % 255 ) 
		{
			printf( "Error! %d != %d\n", buffer->arr[i], i%255 );
			break;
		}

	/*
	 * drop that table
	 */
	printf( "EXEC SQL DROP TABLE TEST_BLOB;\n" );
	EXEC SQL DROP TABLE TEST_BLOB;

}  

Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Herndon VA  

http://govt.us.oracle.com/ -- downloadable utilities  

---

Opinions are mine and do not necessarily reflect those of Oracle Corporation  

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