Checking for Buffer Type

2.5 Checking for Buffer Type

The tptypes(3c) function returns the type and subtype (if one exists) of a buffer. The tptypes() function signature is as follows:

long
tptypes(char *ptr, char *type, char *subtype)

The following table describes the arguments to the tptypes() function.

Table 2-4 tptypes() Function Arguments

Argument	Description
`ptr`	Pointer to a data buffer. This pointer must have been originally allocated by a call to `tpalloc()` or `tprealloc()`, it may not be NULL, and it must be cast as a character type; otherwise, the `tptypes()` function reports an invalid argument error.
`type`	Pointer to the type of the data buffer. type is of character type.
`subtype`	Pointer to the subtype of the data buffer, if one exists. `subtype` is of character type. For all types other than `VIEW`, `VIEW32`, `RECORD`, `X_C_TYPE`, and `X_COMMON`, upon return the `subtype` parameter points to a character array containing the NULL string. Note: For RECORD typed buffer, the maximum length of record name `(subtype)` is 32 bytes. If the length of record name is greater than 16, `tptypes()` will populate the first 16 bytes of subtype, but `RECORD *` pointer will point to the beginning of full-length record name.

Upon success, the tptypes() function returns the length of the buffer in the form of a long integer.

In the event of an error, tptypes() returns a value of -1 and sets tperrno(5) to the appropriate error code. For a list of these error codes, refer to the “Introduction to the C Language Application-to-Transaction Monitor Interface” and tpalloc(3c) in the Oracle Tuxedo ATMI C Function Reference.

You can use the size value returned by tptypes() upon success to determine whether the default buffer size is large enough to hold your data, as shown in the following listing.

Listing Getting Buffer Size

. . .
iptr = (FBFR *)tpalloc("FML", NULL, 0);
ilen = tptypes(iptr, NULL, NULL);
. . .
if (ilen < mydatasize)
     iptr=tprealloc(iptr, mydatasize);