ZFRAME(3)

NAME
zframe - working with single message frames

SYNOPSIS

//  This is a stable class, and may not change except for emergencies. It
//  is provided in stable builds.
//  This class has draft methods, which may change over time. They are not
//  in stable releases, by default. Use --enable-drafts to enable.
#define ZFRAME_MORE 1                       //
#define ZFRAME_REUSE 2                      //
#define ZFRAME_DONTWAIT 4                   //
//  Create a new frame. If size is not null, allocates the frame data
//  to the specified size. If additionally, data is not null, copies
//  size octets from the specified data into the frame body.
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);
//  Create a frame with a specified string content.
CZMQ_EXPORT zframe_t *
    zframe_from (const char *string);
//  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);
//  Destroy a frame
CZMQ_EXPORT void
    zframe_destroy (zframe_t **self_p);
//  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);
//  Return meta data property for frame
//  Caller must free string when finished with it.
CZMQ_EXPORT const char *
    zframe_meta (zframe_t *self, const char *property);
//  Create a new frame that duplicates an existing frame. If frame is null,
//  or memory was exhausted, returns null.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zframe_t *
    zframe_dup (zframe_t *self);
//  Return frame data encoded as printable hex string, useful for 0MQ UUIDs.
//  Caller must free string when finished with it.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT char *
    zframe_strhex (zframe_t *self);
//  Return frame data copied into freshly allocated string
//  Caller must free string when finished with it.
//  Caller owns return value and must destroy it when done.
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);
#ifdef CZMQ_BUILD_DRAFT_API
//  *** Draft method, for development use, may change without warning ***
//  Return frame routing ID, if the frame came from a ZMQ_SERVER socket.
//  Else returns zero.
CZMQ_EXPORT uint32_t
    zframe_routing_id (zframe_t *self);
//  *** Draft method, for development use, may change without warning ***
//  Set routing ID on frame. This is used if/when the frame is sent to a
//  ZMQ_SERVER socket.
CZMQ_EXPORT void
    zframe_set_routing_id (zframe_t *self, uint32_t routing_id);
//  *** Draft method, for development use, may change without warning ***
//  Return frame group of radio-dish pattern.
CZMQ_EXPORT const char *
    zframe_group (zframe_t *self);
//  *** Draft method, for development use, may change without warning ***
//  Set group on frame. This is used if/when the frame is sent to a
//  ZMQ_RADIO socket.
//  Return -1 on error, 0 on success.
CZMQ_EXPORT int
    zframe_set_group (zframe_t *self, const char *group);
#endif // CZMQ_BUILD_DRAFT_API
Please add '@interface' section in './../src/zframe.c'.

DESCRIPTION

The zframe class provides methods to send and receive single message frames across 0MQ 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.

Please add @discuss section in ./../src/zframe.c.

EXAMPLE

From zframe_test method.

    //  Create two PAIR sockets and connect over inproc
    zsock_t *output = zsock_new_pair ("@tcp://127.0.0.1:9001");
    assert (output);
    zsock_t *input = zsock_new_pair (">tcp://127.0.0.1:9001");
    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);
    #if (ZMQ_VERSION >= ZMQ_MAKE_VERSION (4, 1, 0))
    // Test zframe_meta
    frame = zframe_new ("Hello", 5);
    assert (frame);
    rc = zframe_send (&frame, output, 0);
    assert (rc == 0);
    frame = zframe_recv (input);
    const char *meta = zframe_meta (frame, "Socket-Type");
    assert (meta != NULL);
    assert (streq (meta, "PAIR"));
    assert (zframe_meta (frame, "nonexistent") == NULL);
    zframe_destroy (&frame);
    #endif
    zsock_destroy (&input);
    zsock_destroy (&output);
    #if defined (ZMQ_SERVER)
    //  Create server and client sockets and connect over inproc
    zsock_t *server = zsock_new_server ("inproc://zframe-test-routing");
    assert (server);
    zsock_t *client = zsock_new_client ("inproc://zframe-test-routing");
    assert (client);
    //  Send request from client to server
    zframe_t *request = zframe_new ("Hello", 5);
    assert (request);
    rc = zframe_send (&request, client, 0);
    assert (rc == 0);
    assert (!request);
    //  Read request and send reply
    request = zframe_recv (server);
    assert (request);
    assert (zframe_streq (request, "Hello"));
    assert (zframe_routing_id (request));
    zframe_t *reply = zframe_new ("World", 5);
    assert (reply);
    zframe_set_routing_id (reply, zframe_routing_id (request));
    rc = zframe_send (&reply, server, 0);
    assert (rc == 0);
    zframe_destroy (&request);
    //  Read reply
    reply = zframe_recv (client);
    assert (zframe_streq (reply, "World"));
    assert (zframe_routing_id (reply) == 0);
    zframe_destroy (&reply);
    //  Client and server disallow multipart
    frame = zframe_new ("Hello", 5);
    rc = zframe_send (&frame, client, ZFRAME_MORE);
    assert (rc == -1);
    rc = zframe_send (&frame, server, ZFRAME_MORE);
    assert (rc == -1);
    zframe_destroy (&frame);
    zsock_destroy (&client);
    zsock_destroy (&server);
    #endif
    #ifdef ZMQ_RADIO
    //  Create radio and dish sockets and connect over inproc
    zsock_t *radio = zsock_new_radio ("inproc://zframe-test-radio");
    assert (radio);
    zsock_t *dish = zsock_new_dish ("inproc://zframe-test-radio");
    assert (dish);
    //  Join the group
    rc = zsock_join (dish, "World");
    assert (rc == 0);
    //  Publish message from radio
    zframe_t *message = zframe_new ("Hello", 5);
    assert (message);
    rc = zframe_set_group (message, "World");
    assert (rc == 0);
    rc = zframe_send (&message, radio, 0);
    assert (rc == 0);
    assert (!message);
    //  Receive the message from dish
    message = zframe_recv (dish);
    assert (message);
    assert (zframe_streq (message, "Hello"));
    assert (strcmp("World", zframe_group (message)) == 0);
    zframe_destroy (&message);
    zsock_destroy (&dish);
    zsock_destroy (&radio);
    #endif

AUTHORS

The czmq manual was written by the authors in the AUTHORS file.

RESOURCES

Main web site:

Report bugs to the email <zeromq-dev@lists.zeromq.org[1]>

COPYRIGHT

Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: 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/. LICENSE included with the czmq distribution.

NOTES

1.  zeromq-dev@lists.zeromq.org
    mailto:zeromq-dev@lists.zeromq.org