Section 3c - C Functions

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ATMI C Function Reference

tpcall(3c)

Name

tpcall()—Routine for sending service request and awaiting its reply.

Synopsis

int tpcall(char *svc, char *idata, long ilen, char **odata, long \ 
   *olen, long flags)

Description

tpcall() sends a request and synchronously awaits its reply. A call to this function is the same as calling tpacall() immediately followed by tpgetrply(). tpcall() sends a request to the service named by svc. The request is sent out at the priority defined for svc unless overridden by a previous call to tpspri(). The data portion of a request is pointed to by idata, a buffer previously allocated by tpalloc(). ilen specifies how much of idata to send. Note that if idata points to a buffer of a type that does not require a length to be specified, (for example, an FML fielded buffer), then ilen is ignored (and may be 0). Also, idata may be NULL, in which case ilen is ignored. The type and subtype of idata must match one of the types and subtypes recognized by svc.

odata is the address of a pointer to the buffer where a reply is read into, and olen points to the length of that reply. *odata must point to a buffer originally allocated by tpalloc(). If the same buffer is to be used for both sending and receiving, odata should be set to the address of idata. FML and FML32 buffers often assume a minimum size of 4096 bytes; if the reply is larger than 4096, the size of the buffer is increased to a size large enough to accommodate the data being returned. Also, if idata and *odata were equal when tpcall() was invoked, and *odata is changed, then idata no longer points to a valid address. Using the old address can lead to data corruption or process exceptions. As of release 6.4, the default allocation for buffers is 1024 bytes. Also, historical information is maintained on recently used buffers, allowing a buffer of optimal size to be reused as a return buffer.

Buffers on the sending side that may be only partially filled (for example, FML or STRING buffers) will have only the amount that is used send. The system may then enlarge the received data size by some arbitrary amount. This means that the receiver may receive a buffer that is smaller than what was originally allocated by the sender, yet larger than the data that was sent.

The receive buffer may grow, or it may shrink, and its address almost invariably changes, as the system swaps buffers around internally. To determine whether (and how much) a reply buffer changed in size, compare its total size before tpgetrply() was issued with *len. See Introduction to the C Language Application-to-Transaction Monitor Interface for more information about buffer management.

If *olen is 0 upon return, then the reply has no data portion and neither *odata nor the buffer it points to were modified. It is an error for *odata or olen to be NULL.

The following is a list of valid flags:

TPNOTRAN

If the caller is in transaction mode and this flag is set, then when svc is invoked, it is not performed on behalf of the caller's transaction. Note that svc may still be invoked in transaction mode but it will not be the same transaction: a svc may have as a configuration attribute that it is automatically invoked in transaction mode. A caller in transaction mode that sets this flag is still subject to the transaction timeout (and no other). If a service fails that was invoked with this flag, the caller's transaction is not affected.

TPNOCHANGE

By default, if a buffer is received that differs in type from the buffer pointed to by *odata, then *odata's buffer type changes to the received buffer's type so long as the receiver recognizes the incoming buffer type. When this flag is set, the type of the buffer pointed to by *odata is not allowed to change. That is, the type and subtype of the received buffer must match the type and subtype of the buffer pointed to by *odata.

TPNOBLOCK

The request is not sent if a blocking condition exists (for example, the internal buffers into which the message is transferred are full). Note that this flag applies only to the send portion of tpcall(): the function may block waiting for the reply. When TPNOBLOCK is not specified and a blocking condition exists, the caller blocks until the condition subsides or a timeout occurs (either transaction or blocking timeout).

TPNOTIME

This flag signifies that the caller is willing to block indefinitely and wants to be immune to blocking timeouts. However, if the caller is in transaction mode, this flag has no effect; it is subject to the transaction timeout limit. Transaction timeouts may still occur.

TPSIGRSTRT

If a signal interrupts any underlying system calls, then the interrupted system call is reissued.

In a multithreaded application, a thread in the TPINVALIDCONTEXT state is not allowed to issue a call to tpcall().

Return Values

Upon successful return from tpcall() or upon return where tperrno is set to TPESVCFAIL, tpurcode() contains an application defined value that was sent as part of tpreturn().

Upon failure, tpcall() returns -1 and sets tperrno to indicate the error condition. If a call fails with a particular tperrno value, a subsequent call to tperrordetail(), with no intermediate ATMI calls, may provide more detailed information about the generated error. Refer to the tperrordetail(3c) reference page for more information.

Errors

Upon failure, tpcall() sets tperrno to one of the following values. (Unless otherwise noted, failure does not affect the caller's transaction, if one exists.)

[TPEINVAL]

Invalid arguments were given (for example, svc is NULL or flags are invalid).

[TPENOENT]

Cannot send to svc because it does not exist, or it is a conversational service, or the name provided begins with a dot (.).

[TPEITYPE]

The type and subtype of idata is not one of the allowed types and subtypes that svc accepts.

[TPEOTYPE]

Either the type and subtype of the reply are not known to the caller; or, TPNOCHANGE was set in flags and the type and subtype of *odata do not match the type and subtype of the reply sent by the service. Neither *odata, its contents, nor *olen is changed. If the service request was made on behalf of the caller's current transaction, then the transaction is marked abort-only since the reply is discarded.

[TPETRAN]

svc belongs to a server that does not support transactions and TPNOTRAN was not set.

[TPETIME]

This error code indicates that either a timeout has occurred or tpcall() has been attempted, in spite of the fact that the current transaction is already marked rollback only.

If the caller is in transaction mode, then either the transaction is already rollback only or a transaction timeout has occurred. The transaction is marked abort-only. If the caller is not in transaction mode, a blocking timeout has occurred. (A blocking timeout cannot occur if TPNOBLOCK and/or TPNOTIME is specified.) In either case, no changes are made to *odata, its contents, or *olen.

If a transaction timeout has occurred, then, with one exception, any attempts to send new requests or receive outstanding replies will fail with TPETIME until the transaction has been aborted. The exception is a request that does not block, expects no reply, and is not sent on behalf of the caller's transaction (that is, tpacall() with TPNOTRAN, TPNOBLOCK, and TPNOREPLY set).

When a service fails inside a transaction, the transaction is put into the TX_ROLLBACK_ONLY state. This state is treated, for most purposes, as though it were equivalent to a timeout. All further ATMI calls for this transaction (with the exception of those issued in the circumstances described in the previous paragraph) will fail with TPETIME.

[TPESVCFAIL]

The service routine sending the caller's reply called tpreturn() with TPFAIL. This is an application-level failure. The contents of the service's reply, if one was sent, is available in the buffer pointed to by *odata. If the service request was made on behalf of the caller's current transaction, then the transaction is marked abort-only. Note that regardless of whether the transaction has timed out, the only valid communications before the transaction is aborted are calls to tpacall() with TPNOREPLY, TPNOTRAN, and TPNOBLOCK set.

[TPESVCERR]

A service routine encountered an error either in tpreturn(3c) or tpforward(3c) (for example, bad arguments were passed). No reply data is returned when this error occurs (that is, neither *odata, its contents, nor *olen is changed). If the service request was made on behalf of the caller's transaction (that is, TPNOTRAN was not set), then the transaction is marked abort-only. Note that regardless of whether the transaction has timed out, the only valid communications before the transaction is aborted are calls to tpacall() with TPNOREPLY, TPNOTRAN, and TPNOBLOCK set. If either SVCTIMEOUT in the UBBCONFIG file or TA_SVCTIMEOUT in the TM_MIB is non-zero, TPESVCERR is returned when a service timeout occurs.

[TPEBLOCK]

A blocking condition was found on the send call and TPNOBLOCK was specified.

[TPGOTSIG]

A signal was received and TPSIGRSTRT was not specified.

[TPEPROTO]

tpcall() was called improperly.

[TPESYSTEM]

A BEA Tuxedo system error has occurred. The exact nature of the error is written to a log file.

[TPEOS]

An operating system error has occurred. If a message queue on a remote location is filled, TPEOS may be returned even if tpcall() returned successfully.