gpgme/gpgme/w32-io.c

/* w32-io.c - W32 API I/O functions
 *	Copyright (C) 2000 Werner Koch (dd9jn)
 *
 * This file is part of GPGME.
 *
 * GPGME 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.
 *
 * GPGME 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include <config.h>
#ifdef HAVE_DOSISH_SYSTEM

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/types.h>
#include <signal.h>
#include <fcntl.h>
#include <windows.h>
#include "syshdr.h"

#include "util.h"
#include "sema.h"
#include "io.h"


/* 
 * We assume that a HANDLE can be represented by an int which should be true   
 * for all i386 systems (HANDLE is defined as void *) and these are the only
 * systems for which Windows is available.
 * Further we assume that -1 denotes an invalid handle.
 */

#define fd_to_handle(a)  ((HANDLE)(a))
#define handle_to_fd(a)  ((int)(a))
#define pid_to_handle(a) ((HANDLE)(a))
#define handle_to_pid(a) ((int)(a))

#define READBUF_SIZE 4096

struct reader_context_s {
    HANDLE file_hd;
    HANDLE thread_hd;	
    DECLARE_LOCK (mutex);
    
    int eof;
    int eof_shortcut;
    int error;
    int error_code;

    HANDLE have_data_ev;  /* manually reset */
    HANDLE have_space_ev; /* auto reset */
    size_t readpos, writepos;
    char buffer[READBUF_SIZE];
};


#define MAX_READERS 20
static struct {
    volatile int used;
    int fd;
    struct reader_context_s *context;
} reader_table[MAX_READERS];
static int reader_table_size= MAX_READERS;
DEFINE_STATIC_LOCK (reader_table_lock);

static HANDLE
set_synchronize (HANDLE h)
{
    HANDLE tmp;
    
    /* For NT we have to set the sync flag.  It seems that the only
     * way to do it is by duplicating the handle.  Tsss.. */
    if (!DuplicateHandle( GetCurrentProcess(), h,
                          GetCurrentProcess(), &tmp,
                          EVENT_MODIFY_STATE|SYNCHRONIZE, FALSE, 0 ) ) {
        DEBUG1 ("** Set SYNCRONIZE failed: ec=%d\n", (int)GetLastError());
    }
    else {
        CloseHandle (h);
        h = tmp;
    }
    return h;
}



static DWORD CALLBACK 
reader (void *arg)
{
    struct reader_context_s *c = arg;
    int nbytes;
    DWORD nread;

    DEBUG2 ("reader thread %p for file %p started", c->thread_hd, c->file_hd );
    for (;;) {
        LOCK (c->mutex);
        /* leave a one byte gap so that we can see wheter it is empty or full*/
        if ((c->writepos + 1) % READBUF_SIZE == c->readpos) { 
            /* wait for space */
            if (!ResetEvent (c->have_space_ev) )
                DEBUG1 ("ResetEvent failed: ec=%d", (int)GetLastError ());
            UNLOCK (c->mutex);
            DEBUG1 ("reader thread %p: waiting for space ...", c->thread_hd );
            WaitForSingleObject (c->have_space_ev, INFINITE);
            DEBUG1 ("reader thread %p: got space", c->thread_hd );
            LOCK (c->mutex);
       	}
        nbytes = (c->readpos + READBUF_SIZE - c->writepos-1) % READBUF_SIZE;
        if ( nbytes > READBUF_SIZE - c->writepos )
            nbytes = READBUF_SIZE - c->writepos;
        UNLOCK (c->mutex);

        DEBUG2 ("reader thread %p: reading %d bytes", c->thread_hd, nbytes );
        if ( !ReadFile ( c->file_hd,
                         c->buffer+c->writepos, nbytes, &nread, NULL) ) {
            c->error_code = (int)GetLastError ();
            if (c->error_code == ERROR_BROKEN_PIPE ) {
                c->eof=1;
                DEBUG1 ("reader thread %p: got eof (broken pipe)",
                        c->thread_hd );
            }
            else {
                c->error = 1;
                DEBUG2 ("reader thread %p: read error: ec=%d",
                        c->thread_hd, c->error_code );
            }
            break;
        }
        if ( !nread ) {
            c->eof = 1;
            DEBUG1 ("reader thread %p: got eof", c->thread_hd );
            break;
        }
        DEBUG2 ("reader thread %p: got %d bytes", c->thread_hd, (int)nread );
      
        LOCK (c->mutex);
        c->writepos = (c->writepos + nread) % READBUF_SIZE;
        if ( !SetEvent (c->have_data_ev) )
            DEBUG1 ("SetEvent failed: ec=%d", (int)GetLastError ());
        UNLOCK (c->mutex);
    }
    /* indicate that we have an error or eof */
    if ( !SetEvent (c->have_data_ev) )
        DEBUG1 ("SetEvent failed: ec=%d", (int)GetLastError ());
    DEBUG1 ("reader thread %p ended", c->thread_hd );

    return 0;
}


static struct reader_context_s *
create_reader (HANDLE fd)
{
    struct reader_context_s *c;
    SECURITY_ATTRIBUTES sec_attr;
    DWORD tid;

    DEBUG1 ("creating new read thread for file handle %p", fd );
    memset (&sec_attr, 0, sizeof sec_attr );
    sec_attr.nLength = sizeof sec_attr;
    sec_attr.bInheritHandle = FALSE;

    c = xtrycalloc (1, sizeof *c );
    if (!c)
        return NULL;

    c->file_hd = fd;
    c->have_data_ev = CreateEvent (&sec_attr, TRUE, FALSE, NULL);
    c->have_space_ev = CreateEvent (&sec_attr, FALSE, TRUE, NULL);
    if (!c->have_data_ev || !c->have_space_ev) {
        DEBUG1 ("** CreateEvent failed: ec=%d\n", (int)GetLastError ());
        if (c->have_data_ev)
            CloseHandle (c->have_data_ev);
        if (c->have_space_ev)
            CloseHandle (c->have_space_ev);
        xfree (c);
        return NULL;
    }

    c->have_data_ev = set_synchronize (c->have_data_ev);
    INIT_LOCK (c->mutex);

    c->thread_hd = CreateThread (&sec_attr, 0, reader, c, 0, &tid );
    if (!c->thread_hd) {
        DEBUG1 ("** failed to create reader thread: ec=%d\n",
                 (int)GetLastError ());
        DESTROY_LOCK (c->mutex);
        if (c->have_data_ev)
            CloseHandle (c->have_data_ev);
        if (c->have_space_ev)
            CloseHandle (c->have_space_ev);
        xfree (c);
        return NULL;
    }    

    return c;
}


/* 
 * Find a reader context or create a new one 
 * Note that the reader context will last until a io_close.
 */
static struct reader_context_s *
find_reader (int fd, int start_it)
{
    int i;

    for (i=0; i < reader_table_size ; i++ ) {
        if ( reader_table[i].used && reader_table[i].fd == fd )
            return reader_table[i].context;
    }
    if (!start_it)
        return NULL;

    LOCK (reader_table_lock);
    for (i=0; i < reader_table_size; i++ ) {
        if (!reader_table[i].used) {
            reader_table[i].fd = fd;
            reader_table[i].context = create_reader (fd_to_handle (fd));
            reader_table[i].used = 1;
            UNLOCK (reader_table_lock);
            return reader_table[i].context;
        }
    }
    UNLOCK (reader_table_lock);
    return NULL;
}



int
_gpgme_io_read ( int fd, void *buffer, size_t count )
{
    int nread;
    struct reader_context_s *c = find_reader (fd,1);

    DEBUG2 ("fd %d: about to read %d bytes\n", fd, (int)count );
    if ( !c ) {
        DEBUG0 ( "no reader thread\n");
        return -1;
    }
    if (c->eof_shortcut) {
        DEBUG1 ("fd %d: EOF (again)", fd );
        return 0;
    }

    LOCK (c->mutex);
    if (c->readpos == c->writepos && !c->error) { /*no data avail*/
        UNLOCK (c->mutex);
        DEBUG2 ("fd %d: waiting for data from thread %p", fd, c->thread_hd);
        WaitForSingleObject (c->have_data_ev, INFINITE);
        DEBUG2 ("fd %d: data from thread %p available", fd, c->thread_hd);
        LOCK (c->mutex);
    }
    
    if (c->readpos == c->writepos || c->error) {
        UNLOCK (c->mutex);
        c->eof_shortcut = 1;
        if (c->eof) {
            DEBUG1 ("fd %d: EOF", fd );
            return 0;
        }
        if (!c->error) {
            DEBUG1 ("fd %d: EOF but eof flag not set", fd );
            return 0;
        }
        DEBUG1 ("fd %d: read error", fd );
        return -1;
    }
      
    nread = c->readpos < c->writepos? c->writepos - c->readpos
                                    : READBUF_SIZE - c->readpos;
    if (nread > count)
        nread = count;
    memcpy (buffer, c->buffer+c->readpos, nread);
    c->readpos = (c->readpos + nread) % READBUF_SIZE;
    if (c->readpos == c->writepos && !c->eof) {
        if ( !ResetEvent (c->have_data_ev) )
            DEBUG1 ("ResetEvent failed: ec=%d", (int)GetLastError ());
    }
    if (!SetEvent (c->have_space_ev))
        DEBUG1 ("SetEvent failed: ec=%d", (int)GetLastError ());
    UNLOCK (c->mutex);

    DEBUG2 ("fd %d: got %d bytes\n", fd, nread );

    return nread;
}


int
_gpgme_io_write ( int fd, const void *buffer, size_t count )
{
    DWORD nwritten;
    HANDLE h = fd_to_handle (fd);

    /* writing blocks for large counts, so we limit it here. */
    if (count > 1024)
        count = 1024;

    DEBUG2 ("fd %d: about to write %d bytes\n", fd, (int)count );
    if ( !WriteFile ( h, buffer, count, &nwritten, NULL) ) {
        DEBUG1 ("WriteFile failed: ec=%d\n", (int)GetLastError ());
        return -1;
    }
    DEBUG2 ("fd %d:          wrote %d bytes\n",
                   fd, (int)nwritten );

    return (int)nwritten;
}

int
_gpgme_io_pipe ( int filedes[2], int inherit_idx )
{
    HANDLE r, w;
    SECURITY_ATTRIBUTES sec_attr;

    memset (&sec_attr, 0, sizeof sec_attr );
    sec_attr.nLength = sizeof sec_attr;
    sec_attr.bInheritHandle = FALSE;
    
    if (!CreatePipe ( &r, &w, &sec_attr, 0))
        return -1;
    /* make one end inheritable */
    if ( inherit_idx == 0 ) {
        HANDLE h;
        if (!DuplicateHandle( GetCurrentProcess(), r,
                              GetCurrentProcess(), &h, 0,
                              TRUE, DUPLICATE_SAME_ACCESS ) ) {
            DEBUG1 ("DuplicateHandle failed: ec=%d\n", (int)GetLastError());
            CloseHandle (r);
            CloseHandle (w);
            return -1;
        }
        CloseHandle (r);
        r = h;
    }
    else if ( inherit_idx == 1 ) {
        HANDLE h;
        if (!DuplicateHandle( GetCurrentProcess(), w,
                              GetCurrentProcess(), &h, 0,
                              TRUE, DUPLICATE_SAME_ACCESS ) ) {
            DEBUG1 ("DuplicateHandle failed: ec=%d\n", (int)GetLastError());
            CloseHandle (r);
            CloseHandle (w);
            return -1;
        }
        CloseHandle (w);
        w = h;
    }

    filedes[0] = handle_to_fd (r);
    filedes[1] = handle_to_fd (w);
    DEBUG5 ("CreatePipe %p %p %d %d inherit=%d\n", r, w,
                   filedes[0], filedes[1], inherit_idx );
    return 0;
}

int
_gpgme_io_close ( int fd )
{
    if ( fd == -1 )
        return -1;

    DEBUG1 ("** closing handle for fd %d\n", fd);
    /* fixme: destroy thread */

    if ( !CloseHandle (fd_to_handle (fd)) ) { 
        DEBUG2 ("CloseHandle for fd %d failed: ec=%d\n",
                 fd, (int)GetLastError ());
        return -1;
    }

    return 0;
}


int
_gpgme_io_set_nonblocking ( int fd )
{
    return 0;
}


static char *
build_commandline ( char **argv )
{
    int i, n = 0;
    char *buf, *p;

    /* FIXME: we have to quote some things because under Windows the 
     * program parses the commandline and does some unquoting */
    for (i=0; argv[i]; i++)
        n += strlen (argv[i]) + 1;
    buf = p = xtrymalloc (n);
    if ( !buf )
        return NULL;
    *buf = 0;
    if ( argv[0] )
        p = stpcpy (p, argv[0]);
    for (i = 1; argv[i]; i++)
        p = stpcpy (stpcpy (p, " "), argv[i]);

    return buf;
}


int
_gpgme_io_spawn ( const char *path, char **argv,
                  struct spawn_fd_item_s *fd_child_list,
                  struct spawn_fd_item_s *fd_parent_list )
{
    SECURITY_ATTRIBUTES sec_attr;
    PROCESS_INFORMATION pi = {
        NULL,      /* returns process handle */
        0,         /* returns primary thread handle */
        0,         /* returns pid */
        0         /* returns tid */
    };
    STARTUPINFO si;
    char *envblock = NULL;
    int cr_flags = CREATE_DEFAULT_ERROR_MODE
                 | GetPriorityClass (GetCurrentProcess ());
    int i;
    char *arg_string;
    int duped_stdin = 0;
    int duped_stderr = 0;
    HANDLE hnul = INVALID_HANDLE_VALUE;
    int debug_me = !!getenv ("GPGME_DEBUG");

    memset (&sec_attr, 0, sizeof sec_attr );
    sec_attr.nLength = sizeof sec_attr;
    sec_attr.bInheritHandle = FALSE;

    arg_string = build_commandline ( argv );
    if (!arg_string )
        return -1; 

    memset (&si, 0, sizeof si);
    si.cb = sizeof (si);
    si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
    si.wShowWindow = debug_me? SW_SHOW : SW_MINIMIZE;
    si.hStdInput = GetStdHandle (STD_INPUT_HANDLE);
    si.hStdOutput = GetStdHandle (STD_OUTPUT_HANDLE);
    si.hStdError = GetStdHandle (STD_ERROR_HANDLE);

    for (i=0; fd_child_list[i].fd != -1; i++ ) {
        if (fd_child_list[i].dup_to == 0 ) {
            si.hStdInput = fd_to_handle (fd_child_list[i].fd);
            DEBUG1 ("using %d for stdin", fd_child_list[i].fd );
            duped_stdin=1;
        }
        else if (fd_child_list[i].dup_to == 1 ) {
            si.hStdOutput = fd_to_handle (fd_child_list[i].fd);
            DEBUG1 ("using %d for stdout", fd_child_list[i].fd );
        }
        else if (fd_child_list[i].dup_to == 2 ) {
            si.hStdError = fd_to_handle (fd_child_list[i].fd);
            DEBUG1 ("using %d for stderr", fd_child_list[i].fd );
            duped_stderr = 1;
        }
    }

    if( !duped_stdin || !duped_stderr ) {
        SECURITY_ATTRIBUTES sa;

        memset (&sa, 0, sizeof sa );
        sa.nLength = sizeof sa;
        sa.bInheritHandle = TRUE;
        hnul = CreateFile ( "nul",
                            GENERIC_READ|GENERIC_WRITE,
                            FILE_SHARE_READ|FILE_SHARE_WRITE,
                            &sa,
                            OPEN_EXISTING,
                            FILE_ATTRIBUTE_NORMAL,
                            NULL );
        if ( hnul == INVALID_HANDLE_VALUE ) {
            DEBUG1 ("can't open `nul': ec=%d\n", (int)GetLastError ());
            xfree (arg_string);
            return -1;
        }
        /* Make sure that the process has a connected stdin */
        if ( !duped_stdin ) {
            si.hStdInput = hnul;
            DEBUG1 ("using %d for dummy stdin", (int)hnul );
        }
        /* We normally don't want all the normal output */
        if ( !duped_stderr ) {
            si.hStdError = hnul;
            DEBUG1 ("using %d for dummy stderr", (int)hnul );
        }
    }

    DEBUG2 ("CreateProcess, path=`%s' args=`%s'", path, arg_string);
    cr_flags |= CREATE_SUSPENDED; 
    if ( !CreateProcessA (path,
                          arg_string,
                          &sec_attr,     /* process security attributes */
                          &sec_attr,     /* thread security attributes */
                          TRUE,          /* inherit handles */
                          cr_flags,      /* creation flags */
                          envblock,      /* environment */
                          NULL,          /* use current drive/directory */
                          &si,           /* startup information */
                          &pi            /* returns process information */
        ) ) {
        DEBUG1 ("CreateProcess failed: ec=%d\n", (int) GetLastError ());
        xfree (arg_string);
        return -1;
    }

    /* close the /dev/nul handle if used */
    if (hnul != INVALID_HANDLE_VALUE ) {
        if ( !CloseHandle ( hnul ) )
            DEBUG1 ("CloseHandle(hnul) failed: ec=%d\n", (int)GetLastError());
    }

    /* Close the other ends of the pipes */
    for (i=0; fd_parent_list[i].fd != -1; i++ ) {
        DEBUG1 ("Closing fd %d\n", fd_parent_list[i].fd );
        if ( !CloseHandle ( fd_to_handle (fd_parent_list[i].fd) ) )
            DEBUG1 ("CloseHandle failed: ec=%d", (int)GetLastError());
    }

    DEBUG4 ("CreateProcess ready\n"
            "-   hProcess=%p  hThread=%p\n"
            "-   dwProcessID=%d dwThreadId=%d\n",
            pi.hProcess, pi.hThread, 
            (int) pi.dwProcessId, (int) pi.dwThreadId);

    if ( ResumeThread ( pi.hThread ) < 0 ) {
        DEBUG1 ("ResumeThread failed: ec=%d\n", (int)GetLastError ());
    }

    if ( !CloseHandle (pi.hThread) ) { 
        DEBUG1 ("CloseHandle of thread failed: ec=%d\n",
                 (int)GetLastError ());
    }

    return handle_to_pid (pi.hProcess);
}




int
_gpgme_io_waitpid ( int pid, int hang, int *r_status, int *r_signal )
{
    HANDLE proc = fd_to_handle (pid);
    int code, exc, ret = 0;

    *r_status = 0;
    *r_signal = 0;
    code = WaitForSingleObject ( proc, hang? INFINITE : 0 );
    switch (code) {
      case WAIT_FAILED:
        DEBUG2 ("WFSO pid=%d failed: %d\n", (int)pid, (int)GetLastError () );
        break;

      case WAIT_OBJECT_0:
        if (!GetExitCodeProcess (proc, &exc)) {
            DEBUG2 ("** GECP pid=%d failed: ec=%d\n",
                    (int)pid, (int)GetLastError () );
            *r_status = 4; 
        }
        else {
            DEBUG2 ("GECP pid=%d exit code=%d\n", (int)pid,  exc);
            *r_status = exc;
        }
        ret = 1;
        break;

      case WAIT_TIMEOUT:
        if (hang)
            DEBUG1 ("WFSO pid=%d timed out\n", (int)pid);
        break;

      default:
        DEBUG2 ("WFSO pid=%d returned %d\n", (int)pid, code );
        break;
    }
    return ret;
}

int
_gpgme_io_kill ( int pid, int hard )
{
    HANDLE proc = fd_to_handle (pid);

    #warning I am not sure how to kill a process
    /* fixme: figure out how this can be done */
    return 0;
}



/*
 * Select on the list of fds.
 * Returns: -1 = error
 *           0 = timeout or nothing to select
 *          >0 = number of signaled fds
 */
int
_gpgme_io_select ( struct io_select_fd_s *fds, size_t nfds )
{
#if 1
    HANDLE waitbuf[MAXIMUM_WAIT_OBJECTS];
    int    waitidx[MAXIMUM_WAIT_OBJECTS];
    int code, nwait;
    int i, any, any_write;
    int count;
    void *dbg_help;

 restart:
    DEBUG_BEGIN (dbg_help, "select on [ ");
    any = any_write = 0;
    nwait = 0;
    for ( i=0; i < nfds; i++ ) {
        if ( fds[i].fd == -1 ) 
            continue;
        if ( fds[i].for_read || fds[i].for_write ) {
            if ( fds[i].for_read ) {
                struct reader_context_s *c = find_reader (fds[i].fd,1);
                
                if (!c) { 
                    DEBUG1 ("oops: no reader thread for fd %d", fds[i].fd);
                }
                else {
                    if ( nwait >= DIM (waitbuf) ) {
                        DEBUG_END (dbg_help, "oops ]");
                        DEBUG0 ("Too many objects for WFMO!" );
                        return -1;
                    }
                    waitidx[nwait]   = i;
                    waitbuf[nwait++] = c->have_data_ev;
                }
            }
            DEBUG_ADD2 (dbg_help, "%c%d ",
                        fds[i].for_read? 'r':'w',fds[i].fd );
            any = 1;
        }
        fds[i].signaled = 0;
    }
    DEBUG_END (dbg_help, "]");
    if (!any) 
        return 0;

    count = 0;
    /* no way to see whether a handle is ready for writing, signal all */
    for ( i=0; i < nfds; i++ ) {
        if ( fds[i].fd == -1 ) 
            continue;
        if ( fds[i].for_write ) {
            fds[i].signaled = 1;
            any_write =1;
            count++;
        }
    }
    code = WaitForMultipleObjects ( nwait, waitbuf, 0, any_write? 200:1000);
    if ( code >= WAIT_OBJECT_0 && code < WAIT_OBJECT_0 + nwait ) {
        /* This WFMO is a really silly function:  It does return either
         * the index of the signaled object or if 2 objects have been
         * signalled at the same time, the index of the object with the
         * lowest object is returned - so and how do we find out
         * how many objects have been signaled???.
         * The only solution I can imagine is to test each object starting
         * with the returned index individually - how dull.
         */
        any = 0;
        for (i=code - WAIT_OBJECT_0; i < nwait; i++ ) {
            if (WaitForSingleObject ( waitbuf[i], NULL ) == WAIT_OBJECT_0) {
                assert (waitidx[i] >=0 && waitidx[i] < nfds);
                fds[waitidx[i]].signaled = 1;
                any = 1;
                count++;
            }
        }
        if (!any) {
            DEBUG0 ("Oops: No signaled objects found after WFMO");
            count = -1;
        }
    }
    else if ( code == WAIT_TIMEOUT ) {
        DEBUG0 ("WFMO timed out\n" );
    }  
    else if (code == WAIT_FAILED ) {
        int le = (int)GetLastError ();
        if ( le == ERROR_INVALID_HANDLE ) {
            int k, j = handle_to_fd (waitbuf[i]);
                    
            DEBUG1 ("WFMO invalid handle %d removed\n", j);
            for (k=0 ; k < nfds; i++ ) {
                if ( fds[k].fd == j ) {
                    fds[k].for_read = fds[k].for_write = 0;
                    goto restart;
                }
            }
            DEBUG0 (" oops, or not???\n");
        }
        DEBUG1 ("WFMO failed: %d\n", le );
        count = -1;
    }
    else {
        DEBUG1 ("WFMO returned %d\n", code );
        count = -1;
    }

    if ( count ) {
        DEBUG_BEGIN (dbg_help, " signaled [ ");
        for ( i=0; i < nfds; i++ ) {
            if ( fds[i].fd == -1 ) 
                continue;
            if ( (fds[i].for_read || fds[i].for_write) && fds[i].signaled ) {
                DEBUG_ADD2 (dbg_help, "%c%d ",
                            fds[i].for_read? 'r':'w',fds[i].fd );
            }
        }
        DEBUG_END (dbg_help, "]");
    }
    
    return count;
#else  /* This is the code we use */
    int i, any, count;
    int once_more = 0;

    DEBUG_SELECT ((stderr, "gpgme:fakedselect on [ "));
    any = 0;
    for ( i=0; i < nfds; i++ ) {
        if ( fds[i].fd == -1 ) 
            continue;
        if ( fds[i].for_read || fds[i].for_write ) {
            DEBUG_SELECT ((stderr, "%c%d ",
                           fds[i].for_read? 'r':'w',fds[i].fd ));
            any = 1;
        }
        fds[i].signaled = 0;
    }
    DEBUG_SELECT ((stderr, "]\n" ));
    if (!any) 
        return 0;

 restart:
    count = 0;
    /* no way to see whether a handle is ready fro writing, signal all */
    for ( i=0; i < nfds; i++ ) {
        if ( fds[i].fd == -1 ) 
            continue;
        if ( fds[i].for_write ) {
            fds[i].signaled = 1;
            count++;
        }
    }

    /* now peek on all read handles */
    for ( i=0; i < nfds; i++ ) {
        if ( fds[i].fd == -1 ) 
            continue;
        if ( fds[i].for_read ) {
            int navail;
            
            if ( !PeekNamedPipe (fd_to_handle (fds[i].fd),
                                 NULL, 0, NULL, &navail, NULL) ) {
                DEBUG1 ("select: PeekFile failed: ec=%d\n",
                        (int)GetLastError ());
            }
            else if ( navail ) {
                DEBUG2 ("fd %d has %d bytes to read\n",  fds[i].fd, navail );
                fds[i].signaled = 1;
                count++;
            }
        }
    }
    if ( !once_more && !count ) {
        /* once more but after relinquishing our timeslot */
        once_more = 1;
        Sleep (0);
        goto restart;
    }

    if ( count ) {
        DEBUG_SELECT ((stderr, "gpgme:      signaled [ "));
        for ( i=0; i < nfds; i++ ) {
            if ( fds[i].fd == -1 ) 
                continue;
            if ( (fds[i].for_read || fds[i].for_write) && fds[i].signaled ) {
                DEBUG_SELECT ((stderr, "%c%d ",
                               fds[i].for_read? 'r':'w',fds[i].fd ));
            }
        }
        DEBUG_SELECT ((stderr, "]\n" ));
    }
    
    return count;
#endif
}

#endif /*HAVE_DOSISH_SYSTEM*/