man pages section 3: Extended Library Functions, Volume 1

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Updated: July 2014
 
 

dat_ep_post_recv(3DAT)

Name

dat_ep_post_recv - receive data over the connection of the Endpoint

Synopsis

cc [ flag… ] file–ldat [ library… ] 
#include <dat/udat.h>

DAT_RETURN
    dat_ep_post_recv (
    IN    DAT_EP_HANDLE        ep_handle,
    IN    DAT_COUNT            num_segments,
    IN    DAT_LMR_TRIPLET      *local_iov,
    IN    DAT_DTO_COOKIE       user_cookie,
    IN    DAT_COMPLETION_FLAGS completion_flags
    )

Parameters

ep_handle

Handle for an instance of the Endpoint.

num_segments

Number of lmr_triplets in local_iov. Can be 0 for receiving a 0 size message.

local_iov

I/O Vector that specifies the local buffer to be filled. Can be NULL for receiving a 0 size message.

user_cookie:

User-provided cookie that is returned to the Consumer at the completion of the Receive DTO. Can be NULL.

completion_flags

Flags for posted Receive. The default DAT_COMPLETION_DEFAULT_FLAG is 0x00. Other values are as follows:

Notification of Completion

DAT_COMPLETION_UNSIGNALLED_FLAG

0x04

Non-notification completion. Local Endpoint must be configured for Unsignaled CompletionNotification Suppression.

Description

The dat_ep_post_recv() function requests the receive of the data over the connection of the ep_handle Endpoint of the incoming message into the local_iov.

The num_segments parameter specifies the number of segments in the local_iov. The local_iov segments are filled in the I/O Vector order until the whole message is received. This ensures that all the "front" segments of the local_iov I/O Vector are completely filled, only one segment is partially filled, if needed, and all segments that follow it are not filled at all.

The user_cookie allows Consumers to have unique identifiers for each DTO. These identifiers are completely under user control and are opaque to the Provider. There is no requirement on the Consumer that the value user_cookie should be unique for each DTO. The user_cookie is returned to the Consumer in the Completion event for the posted Receive.

The completion of the posted Receive is reported to the Consumer asynchronously through a DTO Completion event based on the configuration of the connection for Solicited Wait and the specified completion_flags value for the matching Send. The value of DAT_COMPLETION _UNSIGNALLED_FLAG is only valid if the Endpoint Recv Completion Flags DAT_COMPLETION_UNSIGNALLED_FLAG. Otherwise, DAT_INVALID_PARAMETER is returned.

A Consumer must not modify the local_iov or its content until the DTO is completed. When a Consumer does not adhere to this rule, the behavior of the Provider and the underlying Transport is not defined. Providers that allow Consumers to get ownership of the local_iov but not the memory it specified back after the dat_ep_post_recv() returns should document this behavior and also specify its support in Provider attributes. This behavior allows Consumer full control of the local_iov content after dat_ep_post_recv () returns. Because this behavior is not guaranteed by all Providers, portable Consumers should not rely on this behavior. Consumers shouldnot rely on the Provider copying local_iov information.

The DAT_SUCCESS return of the dat_ep_post_recv() is at least the equivalent of posting a Receive operation directly by native Transport. Providers should avoid resource allocation as part of dat_ep_post_recv() to ensure that this operation is nonblocking and thread safe for an UpCall.

If the size of an incoming message is larger than the size of the local_iov, the reported status of the posted Receive DTO in the corresponding Completion DTO event is DAT_DTO_LENGTH_ERROR. If the reported status of the Completion DTO event corresponding to the posted Receive DTO is not DAT_DTO_SUCCESS, the content of the local_iov is not defined.

The operation is valid for all states of the Endpoint. The actual data transfer does not take place until the Endpoint is in the DAT_EP_STATE_CONNECTED state. The operation on the Endpoint in DAT_EP_STATE_DISCONNECTED is allowed. If the operation returns successfully, the posted Recv is immediately flushed to recv_evd_handle.

Return Values

DAT_SUCCESS

The operation was successful.

DAT_INSUFFICIENT_RESOURCES

The operation failed due to resource limitations.

DAT_INVALID_PARAMETER

Invalid parameter. For example, one of the IOV segments pointed to a memory outside its LMR.

DAT_INVALID_HANDLE

The ep_handle parameter is invalid.

DAT_PROTECTION_VIOLATION

Protection violation for local or remote memory access. Protection Zone mismatch between an LMR of one of the local_iov segments and the local Endpoint.

DAT_PRIVILEGES_VIOLATION

Privileges violation for local or remote memory access. One of the LMRs used in local_iov was either invalid or did not have the local read privileges.

Usage

For best Recv operation performance, the Consumer should align each buffer segment of local_iov to the Optimal Buffer Alignment attribute of the Provider. For portable applications, the Consumer should align each buffer segment of local_iov to the DAT_OPTIMAL_ALIGNMENT.

Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
Unsafe
Standard
uDAPL, 1.1, 1.2

See Also

libdat(3LIB), attributes(5)