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- /*
- *
- * Copyright (c) 2003 The Regents of the University of California. All
- * rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * - Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * - Neither the name of the University nor the names of its
- * contributors may be used to endorse or promote products derived
- * from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
- * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
- /*
- * FUSD - The Framework for UserSpace Devices - Example program
- *
- * Jeremy Elson <jelson@circlemud.org>
- *
- * echo.c: Example of how to use both the 'read' and 'write' callbacks.
- *
- * This example creates a single device, /dev/echo. If you write
- * something to /dev/echo (e.g., "echo HI THERE > /dev/echo"), it gets
- * stored. Then, when you read (e.g. "cat /dev/echo"), you get back
- * whatever you wrote most recently.
- *
- * $Id: echo.c 12351 2007-01-19 07:22:54Z xiphmont $
- */
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <errno.h>
- #include <unistd.h>
- #include "fusd.h"
- #define MIN(x, y) ((x) < (y) ? (x) : (y))
- /* EXAMPLE START echo.c */
- char *data = NULL;
- int data_length = 0;
- ssize_t echo_read(struct fusd_file_info *file, char *user_buffer,
- size_t user_length, loff_t *offset)
- {
- /* if the user has read past the end of the data, return EOF */
- if (*offset >= data_length)
- return 0;
- /* only return as much data as we have */
- user_length = MIN(user_length, data_length - *offset);
- /* copy data to user starting from the first byte they haven't seen */
- memcpy(user_buffer, data + *offset, user_length);
- *offset += user_length;
- /* tell them how much data they got */
- return user_length;
- }
- ssize_t echo_write(struct fusd_file_info *file, const char *user_buffer,
- size_t user_length, loff_t *offset)
- {
- /* free the old data, if any */
- if (data != NULL) {
- free(data);
- data = NULL;
- data_length = 0;
- }
- /* allocate space for new data; return error if that fails */
- if ((data = malloc(user_length)) == NULL)
- return -ENOMEM;
- /* make a copy of user's data; tell the user we copied everything */
- memcpy(data, user_buffer, user_length);
- data_length = user_length;
- return user_length;
- }
- /* EXAMPLE STOP */
- int do_open_or_close(struct fusd_file_info *file)
- {
- return 0; /* opens and closes always succeed */
- }
- struct fusd_file_operations echo_fops = {
- open: do_open_or_close,
- read: echo_read,
- write: echo_write,
- close: do_open_or_close
- };
- int main(int argc, char *argv[])
- {
- if (fusd_register("/dev/echo", "misc", "echo", 0666, NULL, &echo_fops) < 0) {
- perror("register of /dev/echo failed");
- exit(1);
- }
- fprintf(stderr, "calling fusd_run...\n");
- fusd_run();
- return 0;
- }
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