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Re: [Libguestfs] [PATCH] Add echo_daemon command



On Fri, Sep 11, 2009 at 02:39:24PM +0100, Matthew Booth wrote:
> echo_daemon is a simple echo which can be used to test connectivity between the
> client and daemon.
> ---
>  daemon/Makefile.am   |    1 +
>  daemon/echo_daemon.c |   66 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  po/POTFILES.in       |    1 +
>  src/MAX_PROC_NR      |    2 +-
>  src/generator.ml     |    7 +++++
>  5 files changed, 76 insertions(+), 1 deletions(-)
>  create mode 100644 daemon/echo_daemon.c
> 
> diff --git a/daemon/Makefile.am b/daemon/Makefile.am
> index 83ee408..ae74699 100644
> --- a/daemon/Makefile.am
> +++ b/daemon/Makefile.am
> @@ -36,6 +36,7 @@ guestfsd_SOURCES = \
>  	dmesg.c \
>  	dropcaches.c \
>  	du.c \
> +	echo_daemon.c \
>  	ext2.c \
>  	fallocate.c \
>  	file.c \
> diff --git a/daemon/echo_daemon.c b/daemon/echo_daemon.c
> new file mode 100644
> index 0000000..dbede2f
> --- /dev/null
> +++ b/daemon/echo_daemon.c
> @@ -0,0 +1,66 @@
> +/* libguestfs - the guestfsd daemon
> + * Copyright (C) 2009 Red Hat Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program 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 General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + */
> +
> +#include <config.h>
> +
> +#include <string.h>
> +
> +#include "actions.h"
> +
> +char *
> +do_echo_daemon (char *const *argv)
> +{
> +  char *out = NULL;
> +  size_t out_len = 0;
> +
> +  /* Iterate over argv entries until reaching the NULL terminator */
> +  while (*argv) {
> +    char add_space = 0;
> +
> +    /* Store the end of current output */
> +    size_t out_end = out_len;
> +
> +    /* Calculate the new output size */
> +    size_t arg_len = strlen(*argv);
> +    out_len += arg_len;
> +
> +    /* We will prepend a space if this isn't the first argument added */
> +    if (NULL != out) {
> +      out_len++;
> +      add_space = 1;
> +    }
> +
> +    /* Make the output buffer big enough for the string and its terminator */
> +    out = realloc (out, out_len + 1);

In the daemon we have to check the return value from malloc/realloc
very carefully.  The reason is that the daemon runs in limited space.

> +    /* Prepend a space if required */
> +    if (add_space) {
> +      out[out_end++] = ' ';
> +    }
> +
> +    /* Copy the argument to the output */
> +    memcpy(&out[out_end], *argv, arg_len);
> +
> +    argv++;
> +  }
> +
> +  /* NULL terminate the output */
> +  out[out_len] = '\0';
> +
> +  return out;
> +}
> diff --git a/po/POTFILES.in b/po/POTFILES.in
> index 1b2f82a..44e472b 100644
> --- a/po/POTFILES.in
> +++ b/po/POTFILES.in
> @@ -12,6 +12,7 @@ daemon/dir.c
>  daemon/dmesg.c
>  daemon/dropcaches.c
>  daemon/du.c
> +daemon/echo_daemon.c
>  daemon/ext2.c
>  daemon/fallocate.c
>  daemon/file.c
> diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
> index 205a12b..6bb2f98 100644
> --- a/src/MAX_PROC_NR
> +++ b/src/MAX_PROC_NR
> @@ -1 +1 @@
> -194
> +195
> diff --git a/src/generator.ml b/src/generator.ml
> index 439c9c4..f820e1f 100755
> --- a/src/generator.ml
> +++ b/src/generator.ml
> @@ -3595,6 +3595,13 @@ This loads a kernel module in the appliance.
>  The kernel module must have been whitelisted when libguestfs
>  was built (see C<appliance/kmod.whitelist.in> in the source).");
>  
> +  ("echo_daemon", (RString "output", [StringList "words"]), 195, [],
> +   [InitNone, Always, TestRun [["echo_daemon"; "\"This is a test\""]]],

This should test the return value using TestOutput.  Also note that
this is passing a list of length four.  (Handling of lists in the test
code is very hairy).

> +   "echo arguments back to the client",
> +   "\
> +This commands works much like the unix echo command. It returns its arguments as
> +a string.");

A better description:

  This command concatenates the list of C<words> passed with
  single spaces between them and returns the resulting string.
  
  You can use this to test the connection through to the daemon.
  
  See also C<guestfs_ping_daemon>.

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/


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