这个想法是创建一个二叉进程树，将信息沿树发送，然后将值发送回树，在信息上升时聚合信息。
我遇到的问题是使用select()来确定何时准备好读取管道。在我到目前为止所写的内容中，第一个管道（第一个左孩子）能够接收信息并打印出来；但是第二个管道（第一个右孩子）在收到任何信息之前超时。我不知道为什么，因为第一个管道工作得很好。
每个孩子最终都会创造出自己的孩子，如果没有更好的处理方法，我什至无法开始这部分过程select()。
int bit_count(char *passed, int len){
//initialize file descriptors
int fd1[2] = {1, 2};
int fd2[2] = {3, 4};
fd_set read_set;
fd_set write_set;
//set timeval structure for timeout
struct timeval tv;
tv.tv_sec = 10;
tv.tv_usec = 0;
FD_ZERO(&read_set); //clear the set
FD_SET(fd1[0], &read_set); //add first file descriptor to set
FD_SET(fd2[0], &read_set); //add second file descriptor to set
//open the pipes
pipe(fd1);
pipe(fd2);
//fork a child process
pid_t kid = fork();
if(kid == -1) printf("forking failed.");
if (kid == 0){ //first child process
int status = 1;
while(status){
int retval = select(fd1[0]+1, &read_set, NULL, NULL, &tv);
switch(retval) {
case -1:
printf("Select Error.\n");
exit (-1);
status = 0;
break;
case 0:
printf("Timeout...");
status = 0;
break;
default:
if (FD_ISSET(fd1[0], &read_set)) {
char *lstring = malloc(sizeof(char)*(len/2));
read(fd1[0], lstring, len);
printf("Child Left: %s\n", lstring);
close(fd1);
//execl("child.c", parent);
status = 0;
}
}
}
}
else{ //parent process
//fork a second child process
pid_t kid2 = fork();
if (kid2 == 0) { //second child process
int status = 1;
while(status){
int retval = select(fd2[0]+1, &read_set, NULL, NULL, &tv);
switch(retval) {
case -1:
printf("Select Error.\n");
exit (-1);
status = 0;
break;
case 0:
printf("Timeout...");
status = 0;
break;
default:
if (FD_ISSET(fd2[0], &read_set)) {
char *rstring = malloc(sizeof(char)*((len/2)+(len%2)));
read(fd2[0], rstring, len);
printf("Child Right: %s\n", rstring);
//execl("child.c", parent);
status = 0;
}
}
}
}
else{
int status;
//create character arrays for
printf("\n\nParent Original String: %s\n", passed);
printf("Measured Length: %d\n", len);
int left = (len/2);
int right =(len/2)+(len % 2);
char *lstring = malloc(sizeof(char)*(left+1));
char *rstring = malloc(sizeof(char)*(right+1));
memcpy(lstring, passed, left);
lstring[left] = '\0';
memcpy(rstring, passed+left, right);
rstring[right] = '\0';
printf("Parent Left: %s\n", lstring);
printf("Parent Right: %s\n", rstring);
write(fd1[1], lstring, sizeof(char)*(left+1));
write(fd2[1], rstring, sizeof(char)*(right+1));
waitpid(kid, &status, NULL);
waitpid(kid2, &status, NULL);
}
return 0;
}
return 0;
}