scsh-0.6/c/unix/fd-io.c

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/* Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees.
See file COPYING. */
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/time.h>
#include <errno.h> /* for errno, (POSIX?/ANSI) */
#include "sysdep.h"
#include "c-mods.h"
#include "scheme48vm.h"
#include "event.h"
/* Non-blocking I/O on file descriptors.
There appear to be two ways to get non-blocking input and output. One
is to open files with the O_NONBLOCK flag (and to use fcntl() to do the
same to stdin and stdout), the other is to call select() on each file
descriptor before doing the I/O operation. O_NONBLOCK has the problem
of being a property of the file descriptor, and its use with stdin and
stdout can lead to horrible results.
We use a mixture of both. For input files we call select() before doing
a read(), because read() will return immediately if there are any bytes
available at all, and using O_NONBLOCK on stdin is a very bad idea.
Output files are opened using O_NONBLOCK and stdout is left alone.
*/
int
ps_open_fd(char *filename, bool is_input, long *status)
{
#define FILE_NAME_SIZE 1024
#define PERMISSION 0666 /* read and write for everyone */
char filename_temp[FILE_NAME_SIZE];
char *expanded;
extern char *s48_expand_file_name(char *, char *, int);
int flags;
mode_t mode;
expanded = s48_expand_file_name(filename, filename_temp, FILE_NAME_SIZE);
if (expanded == NULL)
return -1;
if (is_input) {
flags = O_RDONLY;
mode = 0; }
else {
flags = O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK;
mode = PERMISSION; }
/* keep trying if interrupted */
while(TRUE) {
int fd = open(expanded, flags, mode);
if (fd != -1) {
*status = NO_ERRORS;
return fd; }
else if (errno != EINTR) {
*status = errno;
return -1; }
}
}
int
ps_close_fd(long fd_as_long)
{
int fd = (int)fd_as_long;
/* keep retrying if interrupted */
while(TRUE) {
int status = close(fd);
if (status != -1) {
s48_remove_fd(fd);
return NO_ERRORS; }
else if (errno != EINTR)
return errno;
}
}
bool ps_check_fd(long fd_as_long, bool is_read, long *status)
{
int fd = (int)fd_as_long;
int ready;
struct timeval timeout;
fd_set fds;
FD_ZERO(&fds);
FD_SET(fd, &fds);
timerclear(&timeout);
*status = NO_ERRORS;
while(TRUE) {
ready = select(fd + 1,
is_read ? &fds : NULL,
is_read ? NULL : &fds,
&fds,
&timeout);
if (ready == 0)
return FALSE;
else if (ready == 1)
return TRUE;
else if (errno != EINTR) {
*status = errno;
return FALSE; } }
}
/*
* Return TRUE if successful, and FALSE otherwise.
*/
bool
ps_add_pending_fd(long fd_as_long, bool is_input)
{
return s48_add_pending_fd((int) fd_as_long, is_input);
}
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long
ps_read_fd(long fd_as_long, char *buffer, long max, bool waitp,
bool *eofp, bool *pending, long *status)
{
int got, ready;
void *buf = (void *)buffer;
int fd = (int)fd_as_long;
struct timeval timeout;
fd_set readfds;
FD_ZERO(&readfds);
FD_SET(fd, &readfds);
timerclear(&timeout);
/* for the normal return */
*eofp = FALSE;
*pending = FALSE;
*status = NO_ERRORS;
while(TRUE) {
ready = select(fd + 1, &readfds, NULL, &readfds, &timeout);
if (ready == 0) {
if (!waitp)
return 0;
else if (s48_add_pending_fd(fd, TRUE)) {
*pending = TRUE;
return 0; }
else {
*status = ENOMEM; /* as close as POSIX gets */
return 0; }}
else if (ready == -1) {
if (errno != EINTR) {
*status = errno;
return 0; } }
else { /* characters waiting */
got = read(fd, buf, max);
if (got > 0) { /* all is well */
return got; }
else if (got == 0) { /* end of file */
*eofp = TRUE;
return 0; }
else if (errno == EINTR) { /* HCC */
return 0; }
else if (errno == EAGAIN) { /* HCC */
if (!waitp)
return 0;
else if (s48_add_pending_fd(fd, TRUE)) {
*pending = TRUE;
return 0; }
else {
*status = ENOMEM; /* as close as POSIX gets */
return 0; } }
else {
*status = errno;
return 0; } } }
}
long
ps_write_fd(long fd_as_long, char *buffer, long max, bool *pending, long *status)
{
int sent;
int fd = (int)fd_as_long;
void *buf = (void *)buffer;
*pending = FALSE;
*status = NO_ERRORS;
sent = write(fd, buf, max);
if (sent > 0)
{}
else if (errno == EINTR || errno == EAGAIN) { /* HCC */
if (s48_add_pending_fd(fd, FALSE))
*pending = TRUE;
else
*status = ENOMEM; /* as close as POSIX gets */
sent = 0; }
else {
*status = errno;
sent = 0; }
return sent;
}
long
ps_abort_fd_op(long fd_as_long)
{
int fd = (int)fd_as_long;
fprintf(stderr, "aborting %d\n", fd);
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if (!s48_remove_fd(fd))
fprintf(stderr, "Error: ps_abort_fd_op, no pending operation on fd %d\n",
fd);
return 0; /* because we do not actually do any I/O in parallel the
status is always zero: no characters transfered. */
}