The following program demonstrates how you can send more than one message from the sender, but use asyncmsg_get() only once to get all these messages together. You must set the appropriate trigger number (3 in this example) in the attributes that you pass to asyncmsg_connect_attach() to trigger the copying of the messages. The trigger number defines the number of messages the sender predetermines to send together. This increases throughput.
#include <stdio.h> #include <process.h> #include <unistd.h> #include <string.h> #include <sys/asyncmsg.h> int callback(int err, void *cmsg, unsigned handle) { printf("Callback: err = %d, msg = %p, handle = %d\n", err, cmsg, handle); return 0; } /* * Multiple put, then see if get can get all of them. */ int main() { int chid, coid, i; struct _asyncmsg_connection_attr aca; struct _asyncmsg_get_header *agh, *agh1; char msg[3][80]; if ((chid = asyncmsg_channel_create(_NTO_CHF_SENDER_LEN, 0666, 2048, 5, NULL, NULL)) == -1) { perror("channel_create"); return -1; } memset(&aca, 0, sizeof(aca)); aca.buffer_size = 2048; aca.max_num_buffer = 5; aca.trigger_num_msg = 3; if ((coid = asyncmsg_connect_attach(0, 0, chid, 0, 0, &aca)) == -1) { perror("connect_attach"); return -1; } for (i = 0; i < 3; i++) { sprintf(msg[i], "Async Message Passing (msgid %d)\n", i); if ((asyncmsg_put(coid, msg[i], strlen(msg[i]) + 1, 1234, callback)) == -1) { perror("put"); return -1; } } if ((agh = asyncmsg_get(chid)) == NULL) { perror("get"); return -1; } printf("Got message(s): \n\n"); while ((agh1 = agh)) { agh = agh1->next; printf("from process: %d (%d)\n", agh1->info.pid, getpid()); printf("msglen: %d (%d)\n", agh1->info.msglen, strlen(*msg) + 1); printf("srclen: %d\n", agh1->info.srcmsglen); printf("err: %d\n", agh1->err); printf("parts: %d\n", agh1->parts); printf("msg: %s\n\n", (char *)agh1->iov->iov_base); asyncmsg_free(agh1); } sleep(1); if (asyncmsg_connect_detach(coid) == -1) { perror("connect_detach"); return -1; } if (asyncmsg_channel_destroy(chid) == -1) { perror("channel_detach"); return -1; } return 0; }