[Libguestfs] Re: factorization would be nice
Richard W.M. Jones
rjones at redhat.com
Wed Aug 12 10:16:02 UTC 2009
On Wed, Aug 12, 2009 at 12:09:25PM +0200, Jim Meyering wrote:
> Richard W.M. Jones wrote:
> > On Wed, Aug 12, 2009 at 09:15:31AM +0100, Richard W.M. Jones wrote:
> >> On Wed, Aug 12, 2009 at 10:07:16AM +0200, Jim Meyering wrote:
> >> > List.iter (
> >> > function
> >> > | Pathname n ->
> >> > pr " char *%s = args.%s;\n" n n;
> >> > pr " ABS_PATH (%s, goto done);\n" n;
> >> > | Device n ->
> >> > pr " char *%s = args.%s;\n" n n;
> >> > pr " RESOLVE_DEVICE (%s, goto done);" n;
> >> > | Dev_or_Path n ->
> >
> > On thing to add here:
> >
> > The 'n's in this code are all different bindings. So there's no way
> > to get a closure which captures the values of all 'n's.
> >
> > Thus in other code (but not in this case) you could have written:
> >
> > let pr_args () =
> > pr " char *%s = args.%s\n" n n
> > in
> >
> > where the value of 'n' would be captured in the closure 'pr_args', and
> > not have to be given explicitly each time.
>
> Thanks for the explanation.
> Here's what I have now:
>
> (match snd style with
> | [] -> ()
> | args ->
> pr " memset (&args, 0, sizeof args);\n";
> pr "\n";
> pr " if (!xdr_guestfs_%s_args (xdr_in, &args)) {\n" name;
> pr " reply_with_error (\"%%s: daemon failed to decode procedure arguments\", \"%s\");\n" name;
> pr " return;\n";
> pr " }\n";
> let pr_args n =
> pr " char *%s = args.%s;\n" n n
> in
> List.iter (
> function
> | Pathname n ->
> pr_args n;
> pr " ABS_PATH (%s, goto done);\n" n;
> | Device n ->
> pr_args n;
> pr " RESOLVE_DEVICE (%s, goto done);" n;
> | Dev_or_Path n ->
> pr_args n;
> pr " REQUIRE_ROOT_OR_RESOLVE_DEVICE (%s, goto done);" n;
> | String n -> pr_args n
> | OptString n -> pr " %s = args.%s ? *args.%s : NULL;\n" n n n
> | StringList n ->
> pr " %s = realloc (args.%s.%s_val,\n" n n n;
> pr " sizeof (char *) * (args.%s.%s_len+1));\n" n n;
> pr " if (%s == NULL) {\n" n;
> pr " reply_with_perror (\"realloc\");\n";
> pr " goto done;\n";
> pr " }\n";
> pr " %s[args.%s.%s_len] = NULL;\n" n n n;
> pr " args.%s.%s_val = %s;\n" n n n;
> | Bool n -> pr " %s = args.%s;\n" n n
> | Int n -> pr " %s = args.%s;\n" n n
> | FileIn _ | FileOut _ -> ()
> ) args;
> pr "\n"
> );
Looks fine. You're only saving a few characters by factoring out
that function though.
Rich.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
libguestfs lets you edit virtual machines. Supports shell scripting,
bindings from many languages. http://et.redhat.com/~rjones/libguestfs/
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