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/*
* (c) The GRASP/AQUA Project, Glasgow University, 1994-2002
*
* hWaitForInput Runtime Support
*/
/* select and supporting types is not Posix */
/* #include "PosixSource.h" */
#include "HsBase.h"
/*
* inputReady(fd) checks to see whether input is available on the file
* descriptor 'fd'. Input meaning 'can I safely read at least a
* *character* from this file object without blocking?'
*/
int
fdReady(int fd, int write, int msecs, int isSock)
{
if
#if defined(_WIN32)
( isSock ) {
#else
( 1 ) {
#endif
int maxfd, ready;
fd_set rfd, wfd;
struct timeval tv;
if ((fd >= (int)FD_SETSIZE) || (fd < 0)) {
/* avoid memory corruption on too large FDs */
errno = EINVAL;
return -1;
}
FD_ZERO(&rfd);
FD_ZERO(&wfd);
if (write) {
FD_SET(fd, &wfd);
} else {
FD_SET(fd, &rfd);
}
/* select() will consider the descriptor set in the range of 0 to
* (maxfd-1)
*/
maxfd = fd + 1;
tv.tv_sec = msecs / 1000;
tv.tv_usec = (msecs % 1000) * 1000;
while ((ready = select(maxfd, &rfd, &wfd, NULL, &tv)) < 0 ) {
if (errno != EINTR ) {
return -1;
}
}
/* 1 => Input ready, 0 => not ready, -1 => error */
return (ready);
}
#if defined(_WIN32)
else {
DWORD rc;
HANDLE hFile = (HANDLE)_get_osfhandle(fd);
DWORD avail;
switch (GetFileType(hFile)) {
case FILE_TYPE_CHAR:
{
INPUT_RECORD buf[1];
DWORD count;
// nightmare. A Console Handle will appear to be ready
// (WaitForSingleObject() returned WAIT_OBJECT_0) when
// it has events in its input buffer, but these events might
// not be keyboard events, so when we read from the Handle the
// read() will block. So here we try to discard non-keyboard
// events from a console handle's input buffer and then try
// the WaitForSingleObject() again.
while (1) // keep trying until we find a real key event
{
rc = WaitForSingleObject( hFile, msecs );
switch (rc) {
case WAIT_TIMEOUT: return 0;
case WAIT_OBJECT_0: break;
default: /* WAIT_FAILED */ maperrno(); return -1;
}
while (1) // discard non-key events
{
rc = PeekConsoleInput(hFile, buf, 1, &count);
// printf("peek, rc=%d, count=%d, type=%d\n", rc, count, buf[0].EventType);
if (rc == 0) {
rc = GetLastError();
if (rc == ERROR_INVALID_HANDLE || rc == ERROR_INVALID_FUNCTION) {
return 1;
} else {
maperrno();
return -1;
}
}
if (count == 0) break; // no more events => wait again
// discard console events that are not "key down", because
// these will also be discarded by ReadFile().
if (buf[0].EventType == KEY_EVENT &&
buf[0].Event.KeyEvent.bKeyDown &&
buf[0].Event.KeyEvent.uChar.AsciiChar != '\0')
{
// it's a proper keypress:
return 1;
}
else
{
// it's a non-key event, a key up event, or a
// non-character key (e.g. shift). discard it.
rc = ReadConsoleInput(hFile, buf, 1, &count);
if (rc == 0) {
rc = GetLastError();
if (rc == ERROR_INVALID_HANDLE || rc == ERROR_INVALID_FUNCTION) {
return 1;
} else {
maperrno();
return -1;
}
}
}
}
}
}
case FILE_TYPE_DISK:
// assume that disk files are always ready:
return 1;
case FILE_TYPE_PIPE:
// WaitForMultipleObjects() doesn't work for pipes (it
// always returns WAIT_OBJECT_0 even when no data is
// available). If the HANDLE is a pipe, therefore, we try
// PeekNamedPipe:
//
rc = PeekNamedPipe( hFile, NULL, 0, NULL, &avail, NULL );
if (rc != 0) {
if (avail != 0) {
return 1;
} else {
return 0;
}
} else {
rc = GetLastError();
if (rc == ERROR_BROKEN_PIPE) {
return 1; // this is probably what we want
}
if (rc != ERROR_INVALID_HANDLE && rc != ERROR_INVALID_FUNCTION) {
maperrno();
return -1;
}
}
/* PeekNamedPipe didn't work - fall through to the general case */
default:
rc = WaitForSingleObject( hFile, msecs );
/* 1 => Input ready, 0 => not ready, -1 => error */
switch (rc) {
case WAIT_TIMEOUT: return 0;
case WAIT_OBJECT_0: return 1;
default: /* WAIT_FAILED */ maperrno(); return -1;
}
}
}
#endif
}
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