zframe man page

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

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]>

Notes

1.

zeromq-dev@lists.zeromq.org

mailto:zeromq-dev@lists.zeromq.org

Referenced By

czmq(7).

11/11/2016 CZMQ 4.0.1 CZMQ Manual