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#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
typedef struct {
char* filename; /* this file is the pipe (set by user) */
char is_server; /* this is set by open_control_file */
int fd; /* this is set by open_control_file */
} single_instance_struct;
/* returns fd, is_server is set to -1 if server, 0 if client */
int open_control_file(single_instance_struct* str)
{
struct stat buf;
if(stat(str->filename,&buf)) {
mkfifo(str->filename,128|256);
str->is_server=-1;
str->fd=open(str->filename,O_NONBLOCK|O_RDONLY);
} else {
str->fd=open(str->filename,O_NONBLOCK|O_WRONLY);
if(errno==ENXIO) {
str->is_server=-1;
str->fd=open(str->filename,O_NONBLOCK|O_RDONLY);
} else
str->is_server=0;
}
return(str->fd);
}
void delete_control_file(single_instance_struct* str)
{
remove(str->filename);
}
void close_control_file(single_instance_struct* str)
{
close(str->fd);
}
typedef void (*event_dispatcher)(char* message);
int get_next_message(char* buffer,int len,single_instance_struct* str,int usecs)
{
struct timeval tv;
fd_set fdset;
int num_fds;
FD_ZERO(&fdset);
FD_SET(str->fd,&fdset);
tv.tv_sec=0;
tv.tv_usec=usecs;
num_fds=select(str->fd+1,&fdset,NULL,NULL,&tv);
if(num_fds) {
int reallen;
reallen=read(str->fd,buffer,len);
if(reallen==0) {
close(str->fd);
str->fd=open(str->filename,O_NONBLOCK|O_RDONLY);
num_fds--;
}
buffer[reallen]=0;
#ifdef DEBUG_1INSTANCE
if(reallen!=0) fprintf(stderr,"message received: %s.\n",buffer);
#endif
}
return(num_fds);
}
int dispatch_event(single_instance_struct* str,event_dispatcher dispatcher,int usecs)
{
char buffer[1024];
int num_fds;
if((num_fds=get_next_message(buffer,1024,str,usecs)) && buffer[0])
dispatcher(buffer);
return(num_fds);
}
int loop_if_server(single_instance_struct* str,event_dispatcher dispatcher)
{
open_control_file(str);
if(str->is_server) {
while(1)
dispatch_event(str,dispatcher,50);
}
return(str->fd);
}
void send_message(single_instance_struct* str,char* message)
{
#ifdef DEBUG_1INSTANCE
int i=
#endif
write(str->fd,message,strlen(message));
#ifdef DEBUG_1INSTANCE
fprintf(stderr,"send: %s => %d(%d)\n",message,i,strlen(message));
#endif
}
#ifdef DEBUG_MAIN
#include <stdio.h>
#include <stdlib.h>
single_instance_struct str1 = { "/tmp/1instance" };
void my_dispatcher(char* message)
{
#ifdef DEBUG_1INSTANCE
fprintf(stderr,"Message arrived: %s.\n",message);
#endif
if(!strcmp(message,"quit")) {
delete_control_file(str1);
exit(0);
}
}
int main(int argc,char** argv)
{
int i;
loop_if_server(str1,my_dispatcher);
for(i=1;i<argc;i++)
send_event(str1,argv[i]);
return(0);
}
#endif
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