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fuse_kern_chan.c
/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU LGPLv2.
  See the file COPYING.LIB
*/

#include "fuse_lowlevel.h"
#include "fuse_kernel.h"
#include "fuse_i.h"

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <assert.h>

static int fuse_kern_chan_receive(struct fuse_chan **chp, char *buf,
                          size_t size)
{
      struct fuse_chan *ch = *chp;
      int err;
      ssize_t res;
      struct fuse_session *se = fuse_chan_session(ch);
      assert(se != NULL);

restart:
      res = read(fuse_chan_fd(ch), buf, size);
      err = errno;

      if (fuse_session_exited(se))
            return 0;
      if (res == -1) {
            /* ENOENT means the operation was interrupted, it's safe
               to restart */
            if (err == ENOENT)
                  goto restart;

            if (err == ENODEV) {
                  fuse_session_exit(se);
                  return 0;
            }
            /* Errors occuring during normal operation: EINTR (read
               interrupted), EAGAIN (nonblocking I/O), ENODEV (filesystem
               umounted) */
            if (err != EINTR && err != EAGAIN)
                  perror("fuse: reading device");
            return -err;
      }
      if ((size_t) res < sizeof(struct fuse_in_header)) {
            fprintf(stderr, "short read on fuse device\n");
            return -EIO;
      }
      return res;
}

static int fuse_kern_chan_send(struct fuse_chan *ch, const struct iovec iov[],
                         size_t count)
{
      if (iov) {
            ssize_t res = writev(fuse_chan_fd(ch), iov, count);
            int err = errno;

            if (res == -1) {
                  struct fuse_session *se = fuse_chan_session(ch);

                  assert(se != NULL);

                  /* ENOENT means the operation was interrupted */
                  if (!fuse_session_exited(se) && err != ENOENT)
                        perror("fuse: writing device");
                  return -err;
            }
      }
      return 0;
}

static void fuse_kern_chan_destroy(struct fuse_chan *ch)
{
      close(fuse_chan_fd(ch));
}

#define MIN_BUFSIZE 0x21000

struct fuse_chan *fuse_kern_chan_new(int fd)
{
      struct fuse_chan_ops op = {
            .receive = fuse_kern_chan_receive,
            .send = fuse_kern_chan_send,
            .destroy = fuse_kern_chan_destroy,
      };
      size_t bufsize = getpagesize() + 0x1000;
      bufsize = bufsize < MIN_BUFSIZE ? MIN_BUFSIZE : bufsize;
      return fuse_chan_new(&op, fd, bufsize, NULL);
}

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