Paolo Bonzini wrote:
> On 07/22/2009 12:27 AM, Paolo Bonzini wrote:
>>> Your proposal is more general, but still assumes that
>>> - the control structure of the reader is simple.
>>
>> This is what Bison requires. Actually Bison's reader is complex, but
>> the output is fed to a Flex scanner, which takes care of the complexity.
>
> Here is some code with an example, the Win32 part I'll do in the next
> few days. If I had to choose one of the three cases you mentioned, I'd
> include this one in gnulib. It shouldn't be too bad to adapt msgfilter
> to this API; for Bison it is overkill.
>
> Paolo
Hi Guys,
I was going to chime in with my patch for chaining filters.
The interfaces seemed easy enough:
/* Open a pipe for input from a child process.
* The child's stdin comes from the file descriptor in fd[0].
* This descriptor is closed for the calling process.
*
* read system write read
* parent <- out_fd[0] <- STDOUT_FILENO <- child <- in_fd[0]
*
*/
extern pid_t create_pipe_fdin (const char *progname,
const char *prog_path, char **prog_argv,
bool null_stderr,
bool slave_process, bool exit_on_error,
int fd[1]);
/* Start or continue a chain of filter processes.
Arguments are as above, except that "prev_filter" must be the returned
result of a previous call to filter_create() or chain_filter_create().
*/
extern struct filter *
chain_filter_create (const char *progname,
const char *prog_path,
const char **prog_argv,
bool null_stderr, bool exit_on_error,
char *read_buf, size_t read_bufsize,
done_read_fn done_read,
void *private_data,
struct filter * prev_filter);
but when I got to the underlying pipe code, I found it too obtuse to disentangle
easliy:
if (slave_process)
{
sigprocmask (SIG_SETMASK, NULL, &blocked_signals);
block_fatal_signals ();
}
actions_allocated = false;
attrs_allocated = false;
if ((err = posix_spawn_file_actions_init (&actions)) != 0
|| (actions_allocated = true,
(pipe_stdin
&& (err = posix_spawn_file_actions_adddup2 (&actions,
ofd[0], STDIN_FILENO))
!= 0)
|| (pipe_stdout
&& (err = posix_spawn_file_actions_adddup2 (&actions,
ifd[1],
STDOUT_FILENO))
!= 0)
|| (pipe_stdin
&& (err = posix_spawn_file_actions_addclose (&actions, ofd[0]))
!= 0)
|| (pipe_stdout
&& (err = posix_spawn_file_actions_addclose (&actions, ifd[1]))
!= 0)
|| (pipe_stdin
&& (err = posix_spawn_file_actions_addclose (&actions, ofd[1]))
!= 0)
|| (pipe_stdout
&& (err = posix_spawn_file_actions_addclose (&actions, ifd[0]))
!= 0)
|| (null_stderr
&& (err = posix_spawn_file_actions_addopen (&actions,
STDERR_FILENO,
"/dev/null", O_RDWR,
0))
!= 0)
|| (!pipe_stdin
&& prog_stdin != NULL
&& (err = posix_spawn_file_actions_addopen (&actions,
STDIN_FILENO,
prog_stdin, O_RDONLY,
0))
!= 0)
|| (!pipe_stdout
&& prog_stdout != NULL
&& (err = posix_spawn_file_actions_addopen (&actions,
STDOUT_FILENO,
prog_stdout, O_WRONLY,
0))
!= 0)
|| (slave_process
&& ((err = posix_spawnattr_init (&attrs)) != 0
|| (attrs_allocated = true,
(err = posix_spawnattr_setsigmask (&attrs,
&blocked_signals))
!= 0
|| (err = posix_spawnattr_setflags (&attrs,
POSIX_SPAWN_SETSIGMASK))
!= 0)))
|| (err = posix_spawnp (&child, prog_path, &actions,
attrs_allocated ? &attrs : NULL, prog_argv,
environ))
!= 0))
{
