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#include "csapp.h"
typedef struct {
int read;
int write;
} pipe_t;
static inline pipe_t MakePipe(void) {
int fds[2];
Pipe(fds);
return (pipe_t){.read = fds[0], .write = fds[1]};
}
static inline void CloseReadEnd(pipe_t p) {
Close(p.read);
}
static inline void CloseWriteEnd(pipe_t p) {
Close(p.write);
}
static bool ReadNum(pipe_t p, long *valp) {
return Read(p.read, valp, sizeof(long)) == sizeof(long);
}
static bool WriteNum(pipe_t p, long val) {
return Write(p.write, &val, sizeof(long)) == sizeof(long);
}
static noreturn void generator(pipe_t out, long maxprime) {
for (long n = 2; n <= maxprime; n++)
WriteNum(out, n);
exit(EXIT_SUCCESS);
}
static void filter(pipe_t in, pipe_t out, long prime) {
long num;
while (ReadNum(in, &num)) {
if (num % prime != 0)
WriteNum(out, num);
}
}
static noreturn void filter_chain(pipe_t in) {
long prime;
/* TODO: Something is missing here! */
pipe_t out = MakePipe();
if (!ReadNum(in, &prime)) {
exit(EXIT_SUCCESS);
}
printf("%ld\n", prime);
if (Fork()) { /* parent */
close(out.read);
filter(in, out, prime);
close(out.write);
close(in.read);
Wait(NULL);
} else { /* child */
close(out.write);
close(in.read);
filter_chain(out);
}
exit(EXIT_SUCCESS);
}
int main(int argc, char *argv[]) {
if (argc != 2)
app_error("Usage: %s [MAXPRIME]", argv[0]);
long maxprime = atol(argv[1]);
if (maxprime < 2 || maxprime > 10000)
app_error("Give maximum prime number in range from 2 to 10000!");
/* Spawn generator. */
pipe_t gen_pipe = MakePipe();
if (Fork()) { /* parent */
CloseWriteEnd(gen_pipe);
} else { /* child */
CloseReadEnd(gen_pipe);
generator(gen_pipe, maxprime);
}
/* Spawn filter chain. */
if (Fork()) { /* parent */
CloseReadEnd(gen_pipe);
} else { /* child */
filter_chain(gen_pipe);
}
for (int i = 0; i < 2; i++)
Wait(NULL);
return 0;
}
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