older epoll impl

2026-01-11 20:11:25 +00:00
parent 7299f7bc4c
commit 4121154e21
3 changed files with 165 additions and 0 deletions
@@ -0,0 +1,152 @@
+#include <fcntl.h>
+#include <sys/epoll.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <cerrno>
+#include <cstring>
+#include <iostream>
+
+#define MAX_EVENTS 10
+#define BUFFER_SIZE 1024
+#define FIFO_PATH "/tmp/hello_epoll_fifo"
+
+int main() {
+    int epoll_fd, stdin_fd, fifo_fd;
+    struct epoll_event ev, events[MAX_EVENTS];
+    char buffer[BUFFER_SIZE];
+
+    // Create a named pipe (FIFO)
+    unlink(FIFO_PATH);  // Remove if it already exists
+    if (mkfifo(FIFO_PATH, 0666) == -1) {
+        std::cerr << "Error creating FIFO: " << strerror(errno) << std::endl;
+        return 1;
+    }
+    std::cout << "Created FIFO at: " << FIFO_PATH << std::endl;
+    std::cout << "From another terminal, run: echo 'Hello from FIFO' > " << FIFO_PATH << std::endl;
+    std::cout << "----------------------------------------" << std::endl;
+
+    // Create epoll instance
+    epoll_fd = epoll_create1(0);
+    if (epoll_fd == -1) {
+        std::cerr << "Error creating epoll: " << strerror(errno) << std::endl;
+        unlink(FIFO_PATH);
+        return 1;
+    }
+
+    // Set stdin to non-blocking mode
+    stdin_fd = STDIN_FILENO;
+    int flags = fcntl(stdin_fd, F_GETFL, 0);
+    fcntl(stdin_fd, F_SETFL, flags | O_NONBLOCK);
+
+    // Add stdin to epoll
+    ev.events = EPOLLIN;
+    ev.data.fd = stdin_fd;
+    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, stdin_fd, &ev) == -1) {
+        std::cerr << "Error adding stdin to epoll: " << strerror(errno) << std::endl;
+        close(epoll_fd);
+        unlink(FIFO_PATH);
+        return 1;
+    }
+    std::cout << "Added stdin (fd=" << stdin_fd << ") to epoll" << std::endl;
+
+    // Open FIFO in non-blocking mode for reading
+    fifo_fd = open(FIFO_PATH, O_RDONLY | O_NONBLOCK);
+    if (fifo_fd == -1) {
+        std::cerr << "Error opening FIFO: " << strerror(errno) << std::endl;
+        close(epoll_fd);
+        unlink(FIFO_PATH);
+        return 1;
+    }
+
+    // Add FIFO to epoll
+    ev.events = EPOLLIN;
+    ev.data.fd = fifo_fd;
+    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fifo_fd, &ev) == -1) {
+        std::cerr << "Error adding FIFO to epoll: " << strerror(errno) << std::endl;
+        close(fifo_fd);
+        close(epoll_fd);
+        unlink(FIFO_PATH);
+        return 1;
+    }
+    std::cout << "Added FIFO (fd=" << fifo_fd << ") to epoll" << std::endl;
+    std::cout << "----------------------------------------" << std::endl;
+    std::cout << "Waiting for events... (type 'quit' to exit)" << std::endl;
+    std::cout << std::endl;
+
+    // Event loop
+    bool running = true;
+    while (running) {
+        int nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
+        if (nfds == -1) {
+            std::cerr << "Error in epoll_wait: " << strerror(errno) << std::endl;
+            break;
+        }
+
+        // Process all ready file descriptors
+        for (int i = 0; i < nfds; i++) {
+            int fd = events[i].data.fd;
+
+            if (events[i].events & EPOLLIN) {
+                ssize_t bytes_read = read(fd, buffer, BUFFER_SIZE - 1);
+
+                if (bytes_read > 0) {
+                    buffer[bytes_read] = '\0';
+
+                    if (fd == stdin_fd) {
+                        std::cout << "[STDIN] Received: " << buffer;
+
+                        // Check for quit command
+                        if (strncmp(buffer, "quit", 4) == 0) {
+                            running = false;
+                            break;
+                        }
+                    } else if (fd == fifo_fd) {
+                        std::cout << "[FIFO] Received: " << buffer;
+                    }
+                } else if (bytes_read == 0) {
+                    // EOF - for FIFO, this happens when writer closes
+                    if (fd == fifo_fd) {
+                        std::cout << "[FIFO] Writer closed, reopening..." << std::endl;
+                        close(fifo_fd);
+
+                        // Reopen FIFO
+                        fifo_fd = open(FIFO_PATH, O_RDONLY | O_NONBLOCK);
+                        if (fifo_fd == -1) {
+                            std::cerr << "Error reopening FIFO: " << strerror(errno) << std::endl;
+                            running = false;
+                            break;
+                        }
+
+                        // Re-add to epoll
+                        ev.events = EPOLLIN;
+                        ev.data.fd = fifo_fd;
+                        if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fifo_fd, &ev) == -1) {
+                            std::cerr << "Error re-adding FIFO to epoll: " << strerror(errno) << std::endl;
+                            running = false;
+                            break;
+                        }
+                    }
+                } else {
+                    // Error reading
+                    if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                        std::cerr << "Error reading from fd " << fd << ": " << strerror(errno) << std::endl;
+                    }
+                }
+            }
+
+            if (events[i].events & (EPOLLERR | EPOLLHUP)) {
+                std::cerr << "Error/Hangup on fd " << fd << std::endl;
+            }
+        }
+    }
+
+    // Cleanup
+    std::cout << std::endl
+              << "Cleaning up..." << std::endl;
+    close(fifo_fd);
+    close(epoll_fd);
+    unlink(FIFO_PATH);
+
+    return 0;
+}