zframe(3)

zframe(3)

CZMQ Manual - CZMQ/3.0.1

Name

zframe - working with single message frames

Synopsis

#define ZFRAME_MORE     1
#define ZFRAME_REUSE    2
#define ZFRAME_DONTWAIT 4

//  Create a new frame with optional size, and optional data
CZMQ_EXPORT zframe_t *
    zframe_new (const void *data, size_t size);

//  Create an empty (zero-sized) frame
CZMQ_EXPORT zframe_t *
    zframe_new_empty (void);

//  Destroy a frame
CZMQ_EXPORT void
    zframe_destroy (zframe_t **self_p);

//  Receive frame from socket, returns zframe_t object or NULL if the recv
//  was interrupted. Does a blocking recv, if you want to not block then use
//  zpoller or zloop.
CZMQ_EXPORT zframe_t *
    zframe_recv (void *source);

// Send a frame to a socket, destroy frame after sending.
// Return -1 on error, 0 on success.
CZMQ_EXPORT int
    zframe_send (zframe_t **self_p, void *dest, int flags);

//  Return number of bytes in frame data
CZMQ_EXPORT size_t
    zframe_size (zframe_t *self);

//  Return address of frame data
CZMQ_EXPORT byte *
    zframe_data (zframe_t *self);

//  Create a new frame that duplicates an existing frame. If frame is null,
//  or memory was exhausted, returns null.
CZMQ_EXPORT zframe_t *
    zframe_dup (zframe_t *self);

//  Return frame data encoded as printable hex string, useful for ØMQ UUIDs.
//  Caller must free string when finished with it.
CZMQ_EXPORT char *
    zframe_strhex (zframe_t *self);

//  Return frame data copied into freshly allocated string
//  Caller must free string when finished with it.
CZMQ_EXPORT char *
    zframe_strdup (zframe_t *self);

//  Return TRUE if frame body is equal to string, excluding terminator
CZMQ_EXPORT bool
    zframe_streq (zframe_t *self, const char *string);

//  Return frame MORE indicator (1 or 0), set when reading frame from socket
//  or by the zframe_set_more() method
CZMQ_EXPORT int
    zframe_more (zframe_t *self);

//  Set frame MORE indicator (1 or 0). Note this is NOT used when sending
//  frame to socket, you have to specify flag explicitly.
CZMQ_EXPORT void
    zframe_set_more (zframe_t *self, int more);

//  Return TRUE if two frames have identical size and data
//  If either frame is NULL, equality is always false.
CZMQ_EXPORT bool
    zframe_eq (zframe_t *self, zframe_t *other);

//  Set new contents for frame
CZMQ_EXPORT void
    zframe_reset (zframe_t *self, const void *data, size_t size);

//  Send message to zsys log sink (may be stdout, or system facility as
//  configured by zsys_set_logstream). Prefix shows before frame, if not null.
CZMQ_EXPORT void
    zframe_print (zframe_t *self, const char *prefix);

//  Probe the supplied object, and report if it looks like a zframe_t.
CZMQ_EXPORT bool
    zframe_is (void *self);

//  Self test of this class
CZMQ_EXPORT void
    zframe_test (bool verbose);

Description

The zframe class provides methods to send and receive single message frames across ØMQ sockets. A frame corresponds to one zmq_msg_t. When you read a frame from a socket, the zframe_more() method indicates if the frame is part of an unfinished multipart message. The zframe_send method normally destroys the frame, but with the ZFRAME_REUSE flag, you can send the same frame many times. Frames are binary, and this class has no special support for text data.

Example

From zframe_test method

// Create two PAIR sockets and connect over inproc
zsock_t *output = zsock_new_pair ("@inproc://zframe.test");
assert (output);
zsock_t *input = zsock_new_pair (">inproc://zframe.test");
assert (input);

// Send five different frames, test ZFRAME_MORE
int frame_nbr;
for (frame_nbr = 0; frame_nbr < 5; frame_nbr++) {
 frame = zframe_new ("Hello", 5);
 assert (frame);
 rc = zframe_send (&frame, output, ZFRAME_MORE);
 assert (rc == 0);
}
// Send same frame five times, test ZFRAME_REUSE
frame = zframe_new ("Hello", 5);
assert (frame);
for (frame_nbr = 0; frame_nbr < 5; frame_nbr++) {
 rc = zframe_send (&frame, output, ZFRAME_MORE + ZFRAME_REUSE);
 assert (rc == 0);
}
assert (frame);
zframe_t *copy = zframe_dup (frame);
assert (zframe_eq (frame, copy));
zframe_destroy (&frame);
assert (!zframe_eq (frame, copy));
assert (zframe_size (copy) == 5);
zframe_destroy (&copy);
assert (!zframe_eq (frame, copy));

// Test zframe_new_empty
frame = zframe_new_empty ();
assert (frame);
assert (zframe_size (frame) == 0);
zframe_destroy (&frame);

// Send END frame
frame = zframe_new ("NOT", 3);
assert (frame);
zframe_reset (frame, "END", 3);
char *string = zframe_strhex (frame);
assert (streq (string, "454E44"));
free (string);
string = zframe_strdup (frame);
assert (streq (string, "END"));
free (string);
rc = zframe_send (&frame, output, 0);
assert (rc == 0);

// Read and count until we receive END
frame_nbr = 0;
for (frame_nbr = 0;; frame_nbr++) {
 zframe_t *frame = zframe_recv (input);
 if (zframe_streq (frame, "END")) {
 zframe_destroy (&frame);
 break;
 }
 assert (zframe_more (frame));
 zframe_set_more (frame, 0);
 assert (zframe_more (frame) == 0);
 zframe_destroy (&frame);
}
assert (frame_nbr == 10);

zsock_destroy (&input); zsock_destroy (&output);

See also

czmq(7)

Authors

The CZMQ manual was written by Pieter Hintjens<moc.xitami|hp#moc.xitami|hp>.

Resources

Main web site: http://czmq.zeromq.org/

Report bugs to the ØMQ development mailing list: <gro.qmorez.stsil|ved-qmorez#gro.qmorez.stsil|ved-qmorez>

Copyright

Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for ØMQ: http://czmq.zeromq.org. This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.