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+/*
+ Copyright (c) 2007-2010 iMatix Corporation
+
+ This file is part of 0MQ.
+
+ 0MQ is free software; you can redistribute it and/or modify it under
+ the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ 0MQ is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZMQ_SWAP_HPP_INCLUDED__
+#define __ZMQ_SWAP_HPP_INCLUDED__
+
+#include "../include/zmq.h"
+
+#include <string>
+#include "stdint.hpp"
+
+namespace zmq
+{
+
+ // This class implements a message swap. Messages are retrieved from
+ // the swap in the same order as they entered it.
+
+ class swap_t
+ {
+ public:
+
+ enum { default_block_size = 8192 };
+
+ // Creates the swap.
+ swap_t (int64_t filesize_);
+
+ ~swap_t ();
+
+ int init ();
+
+ // Stores the message into the swap. The function
+ // returns false if the swap is full; true otherwise.
+ bool store (zmq_msg_t *msg_);
+
+ // Fetches the oldest message from the swap. It is an error
+ // to call this function when the swap is empty.
+ void fetch (zmq_msg_t *msg_);
+
+ void commit ();
+
+ void rollback ();
+
+ // Returns true if the swap is empty; false otherwise.
+ bool empty ();
+
+ // Returns true if and only if the swap is full.
+ bool full ();
+
+ private:
+
+ // Copies data from a memory buffer to the backing file.
+ // Wraps around when reaching maximum file size.
+ void copy_from_file (void *buffer_, size_t count_);
+
+ // Copies data from the backing file to the memory buffer.
+ // Wraps around when reaching end-of-file.
+ void copy_to_file (const void *buffer_, size_t count_);
+
+ // Returns the buffer space available.
+ int64_t buffer_space ();
+
+ void fill_buf (char *buf, int64_t pos);
+
+ void save_write_buf ();
+
+ // File descriptor to the backing file.
+ int fd;
+
+ // Name of the backing file.
+ std::string filename;
+
+ // Maximum size of the backing file.
+ int64_t filesize;
+
+ // File offset associated with the fd file descriptor.
+ int64_t file_pos;
+
+ // File offset the next message will be stored at.
+ int64_t write_pos;
+
+ // File offset the next message will be read from.
+ int64_t read_pos;
+
+ int64_t commit_pos;
+
+ size_t block_size;
+
+ char *buf1;
+ char *buf2;
+ char *read_buf;
+ char *write_buf;
+
+ int64_t write_buf_start_addr;
+ };
+
+}
+
+#endif