INFORMIX-ESQL/C Programmer's Manual ESQL/C Function Library

The rtypalign() function returns the position of the next proper boundary for a variable of the specified data type.

mint rtypalign(pos,  type)

	mint  pos;

	mint  type;

mlong rtypalign(pos,  type)

	mlong  pos;

	mint  type;

 



pos

is the current position in a buffer. 


type  

is an integer that corresponds to the data type of a C or ESQL/C variable. This type can be any data type except var binary. For more information, see Data Type Constants. 

The rtypalign() and rtypmsize() functions are useful when you use an sqlda structure to dynamically fetch data into a buffer. On many hardware platforms, integer and other numeric data types must begin on a work boundary. The C language memory allocation routines allocate memory that is suitably aligned for any data type, including structures. However, these routines do not perform alignment for the constituent components of the structure. The programmer is responsible for performing that alignment with functions such as rtypalign() and rtypmsize(). These functions provide machine independence for storing column data.

After a DESCRIBE statement determines column information, ESQL/C stores the value of type in sqlda.sqlvar->sqltype.

You can see an application of the rtypalign() function in the unload.ec demonstration program.

This sample program is in the rtypalign.ec file in the demo directory.

/*
* rtypalign.ec *

The following program prepares a select on all columns of the orders
table and then calculates the proper alignment for each column in a buffer.
*/

#include <decimal.h>

EXEC SQL include sqltypes;

#define WARNNOTIFY 1
#define NOWARNNOTIFY 0

main()
{
mint i, pos;
int4 ret, exp_chk();
struct sqlda *sql_desc;
struct sqlvar_struct *col;

printf("RTYPALIGN Sample ESQL Program running.\n\n");

EXEC SQL connect to 'stores7'; /* open stores7 database */
exp_chk("Connect to", NOWARNNOTIFY);

EXEC SQL prepare query_1 from "select * from orders"; /* prepare select */
if(exp_chk("Prepare", WARNNOTIFY) == 1)
exit(1);

EXEC SQL describe query_1 into sql_desc; /* initialize sqlda */
if(exp_chk("Describe", WARNNOTIFY) == 1)
exit(1);

col = sql_desc->sqlvar;
printf("\n\ttype\t\tlen\tnext\taligned\n"); /* display column hdgs. */
printf("\t\t\t\tposn\tposn\n\n");
/*
* For each column in the orders table
*/
i = 0;
pos = 0;
while(i++ < sql_desc->sqld)
{
/* Modify sqllen if SQL type is DECIMAL or MONEY */
if(col->sqltype == SQLDECIMAL || col->sqltype == SQLMONEY)
{
col->sqllen = sizeof(dec_t);
}
/*
* display name of SQL type, length and un-aligned buffer position
*/

printf("\t%s\t\t%d\t%d", rtypname(col->sqltype), col->sqllen, pos);

pos = rtypalign(pos, col->sqltype); /* align pos. for type */
printf("\t%d\n", pos);

pos += col->sqllen; /* set next position */
++col; /* bump to next column */
}
printf("\nRTYPALIGN Sample Program over.\n\n");
}

/*
* The exp_chk() file contains the exception handling functions to
* check the SQLSTATE status variable to see if an error has occurred
* following an SQL statement. If a warning or an error has
* occurred, exp_chk() executes the GET DIAGNOSTICS statement and
* prints the detail for each exception that is returned.
*/

EXEC SQL include exp_chk.ec

For a complete listing of the exp_chk() function, see Guide to the exp_chk.ec File or refer to the exp_chk.ec file for a listing of this exception-handling function.

RTYPALIGN Sample ESQL Program running.

 


type
len
next

posn	
aligned

posn






serial
4
0
0

date
4
4
4

integer
4
8
8

char
40
12
12

char
1
52
52

char
10
53
53

date
4
63
64

decimal
22
68
68

money
22
90
90

date
4
112
112






RTYPALIGN Sample Program over.