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core/include/tt/Pipe.h

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+#pragma once
+#include <string>
+#include <iostream>
+#include <unistd.h>
+#include <fcntl.h> /* open() */
+#include <sys/stat.h> /* mkfifo() */
+#include <sys/select.h>
+
+namespace qing {
+
+/* 20260309(qing): 该类不会抛出异常 */
+class Pipe{  
+public:
+	static const int CREATOR = 1;
+        static const int USER =2;
+	static const ssize_t PIPE_MAX_LEN = 2048;
+	Pipe(const std::string& path, int mode)
+	: fd(-1), isCreator(mode == CREATOR) {
+		std::string real_path = "/tmp/pst-";
+		real_path += path;
+		fifo_path = real_path;
+		if (isCreator && mkfifo(fifo_path.c_str(), 0666) == -1 && errno != EEXIST)  /* wr_wr_wr */
+			perror("mkfifo");  /* 文件已存在是正常情况，其他错误才需要处理 */
+	}
+
+	~Pipe() {
+		/* 如果打开了文件，则关闭文件 */
+		if (fd != -1) close(fd);
+		/**********************/
+		/* 如果管道由该对象创建，就要负责清理 */
+		if (isCreator) unlink(fifo_path.c_str()); /* 创建者负责清理 */
+	}
+	Pipe(const Pipe&) = delete;
+	Pipe& operator=(const Pipe&) = delete;
+
+	/* 这里才是打开文件的指令 - 以读模式打开，可以非阻塞 */
+	bool openForRead(bool nonblock = false) {
+
+		/* 设置是否以非阻塞方式打开文件 */
+		int flags = O_RDONLY;
+		if (nonblock) {
+			flags |= O_NONBLOCK;
+		}
+
+		fd = open(fifo_path.c_str(), flags);
+
+		if (fd == -1) {
+			perror("open for read");
+			return false;
+		}
+
+		else {
+			FD_ZERO(&read_fds);
+			FD_SET(fd, &read_fds);
+			if (fd > max_fd) max_fd = fd;
+			return true;
+		}
+
+	}
+
+	/* 以写模式打开文件 */
+	bool openForWrite(/*bool nonblock = falsei*/) {
+
+		/* 写入管道是不需要阻塞/非阻塞的？ */
+		int flags = O_WRONLY;
+		//if (nonblock) {
+		//	flags |= O_NONBLOCK;
+		//}
+		fd = open(fifo_path.c_str(), flags);
+		if (fd == -1) {
+			perror("open for write");
+			return false;
+		}
+
+		else {
+			FD_ZERO(&write_fds);
+			FD_SET(fd, &write_fds);
+			if (fd > max_fd) max_fd = fd;
+			return true;
+		}
+
+	}
+
+	/* 写入管道，如果失败返回-1。成功返回写入的字符数。 */
+	ssize_t writePipe(const std::string &data) {
+		if (fd == -1) {
+			std::cerr << "Pipe not opened for writing" << std::endl;
+			return -1;
+		}
+		else {
+			return write(fd, data.c_str(), data.size());
+		}
+	}
+
+	/* 将探测与读取解耦，使用者可以自行决定要不要阻塞 */
+	bool waitForRead(int timeout_sec = 0, int timeout_usec = 0) {
+
+		/* 如果文件没打开，等待是失败的 */
+		if (fd == -1) return false;
+
+		fd_set temp_fds = read_fds;
+		struct timeval timeout = {timeout_sec, timeout_usec};
+
+		int ret = select(max_fd + 1, &temp_fds, nullptr, nullptr, &timeout);
+
+		if (ret == -1) {
+			perror("select");
+			return false;
+		}
+
+		else {
+			return ret > 0 && FD_ISSET(fd, &temp_fds);
+		}
+	}
+
+	/* 读取数据到字符串，返回实际读取的字节数 */
+	ssize_t readPipe(std::string *output) {
+
+		if (fd == -1) {
+			std::cerr << "Pipe not opened for reading" << std::endl;
+			return -1;
+		}
+
+		else
+		
+		{
+		
+			char buffer[PIPE_MAX_LEN];
+			ssize_t n = read(fd, buffer, sizeof(buffer) - 1);
+			if (n >0) {
+				buffer[n] = '\0';
+				*output = buffer;
+			}
+
+			else if (n == 0) {
+				/* 管道写入端关闭 */
+				*output = "";
+			}
+
+			else {
+				perror("read");
+			}
+
+			return n;
+		
+		}
+	}
+private:
+	std::string fifo_path;
+	int fd;
+	bool isCreator;
+	fd_set read_fds;
+	fd_set write_fds;
+	fd_set except_fds;
+	int max_fd;
+};
+}