Zstr (3) Linux Manual Page

zstr – sending and receiving strings

Synopsis

// Receive C string from socket. Caller must free returned string using
// zstr_free(). Returns NULL if the context is being terminated or the
// process was interrupted.
CZMQ_EXPORT char *
 zstr_recv (void *source);
// Send a C string to a socket, as a frame. The string is sent without
// trailing null byte; to read this you can use zstr_recv, or a similar
// method that adds a null terminator on the received string. String
// may be NULL, which is sent as "".
CZMQ_EXPORT int
 zstr_send (void *dest, const char *string);
// Send a C string to a socket, as zstr_send(), with a MORE flag, so that
// you can send further strings in the same multi-part message.
CZMQ_EXPORT int
 zstr_sendm (void *dest, const char *string);
// Send a formatted string to a socket. Note that you should NOT use
// user-supplied strings in the format (they may contain '%' which
// will create security holes).
CZMQ_EXPORT int
 zstr_sendf (void *dest, const char *format, ...);
// Send a formatted string to a socket, as for zstr_sendf(), with a
// MORE flag, so that you can send further strings in the same multi-part
// message.
CZMQ_EXPORT int
 zstr_sendfm (void *dest, const char *format, ...);
// Send a series of strings (until NULL) as multipart data
// Returns 0 if the strings could be sent OK, or -1 on error.
CZMQ_EXPORT int
 zstr_sendx (void *dest, const char *string, ...);
// Receive a series of strings (until NULL) from multipart data.
// Each string is allocated and filled with string data; if there
// are not enough frames, unallocated strings are set to NULL.
// Returns -1 if the message could not be read, else returns the
// number of strings filled, zero or more. Free each returned string
// using zstr_free(). If not enough strings are provided, remaining
// multipart frames in the message are dropped.
CZMQ_EXPORT int
 zstr_recvx (void *source, char **string_p, ...);
// Free a provided string, and nullify the parent pointer. Safe to call on
// a null pointer.
CZMQ_EXPORT void
 zstr_free (char **string_p);
// Self test of this class
CZMQ_EXPORT void
 zstr_test (bool verbose);

Description

The zstr class provides utility functions for sending and receiving C strings across 0MQ sockets. It sends strings without a terminating null, and appends a null byte on received strings. This class is for simple message sending.

 Memory Wire
 +-------------+---+ +---+-------------+
Send | S t r i n g | 0 | ----> | 6 | S t r i n g |
 +-------------+---+ +---+-------------+

 Wire Heap
 +---+-------------+ +-------------+---+
Recv | 6 | S t r i n g | ----> | S t r i n g | 0 |
 +---+-------------+ +-------------+---+

Example

From zstr_test method.

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

//  Send ten strings, five strings with MORE flag and then END
int string_nbr;
for (string_nbr = 0; string_nbr < 10; string_nbr++)
    zstr_sendf(output, "this is string %d", string_nbr);
zstr_sendx(output, "This", "is", "almost", "the", "very", "END", NULL);

//  Read and count until we receive END
string_nbr = 0;
for (string_nbr = 0;; string_nbr++) {
    char *string = zstr_recv(input);
    assert(string);
    if (streq(string, "END")) {
        zstr_free(&string);
        break;
    }
    zstr_free(&string);
}
assert(string_nbr == 15);

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

Authors

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

Resources

Main web site: m[blue]m[]

Report bugs to the email <m[blue]zeromq-dev [at] lists.zeromq.orgm[][1]>

Copyright

Copyright (c) 1991-2012 iMatix Corporation — http://www.imatix.com Copyright other 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 [at] lists.zeromq.org

mailto:zeromq-dev [at] lists.zeromq.org

zstr (3) Linux Manual Page