[PATCH 04/15] policycoreutils: Add new open_init_pty that doesn't waste CPU time

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From: Russell Coker <russell@xxxxxxxxxxxx>

---
 policycoreutils/run_init/Makefile          |    7 +-
 policycoreutils/run_init/open_init_pty.c   |  399 --------------------------
 policycoreutils/run_init/open_init_pty.cpp |  423 ++++++++++++++++++++++++++++
 3 files changed, 427 insertions(+), 402 deletions(-)
 delete mode 100644 policycoreutils/run_init/open_init_pty.c
 create mode 100644 policycoreutils/run_init/open_init_pty.cpp

diff --git a/policycoreutils/run_init/Makefile b/policycoreutils/run_init/Makefile
index 5815a08..e3c6e9d 100644
--- a/policycoreutils/run_init/Makefile
+++ b/policycoreutils/run_init/Makefile
@@ -10,6 +10,7 @@ AUDITH = $(shell ls /usr/include/libaudit.h 2>/dev/null)
 
 CFLAGS ?= -Werror -Wall -W
 override CFLAGS += -I$(PREFIX)/include -DUSE_NLS -DLOCALEDIR="\"$(LOCALEDIR)\"" -DPACKAGE="\"policycoreutils\""
+CPPFLAGS ?= $(CFLAGS)
 LDLIBS += -lselinux -L$(PREFIX)/lib
 ifeq ($(PAMH), /usr/include/security/pam_appl.h)
 	override CFLAGS += -DUSE_PAM
@@ -23,12 +24,12 @@ ifeq ($(AUDITH), /usr/include/libaudit.h)
 	LDLIBS += -laudit
 endif
 
-TARGETS=$(patsubst %.c,%,$(wildcard *.c))
+TARGETS=open_init_pty run_init
 
 all: $(TARGETS)
 
-open_init_pty: open_init_pty.c
-	$(LINK.c) $^ -ldl -lutil -o $@
+open_init_pty: open_init_pty.cpp
+	$(LINK.cpp) $^ -ldl -lutil -o $@
 
 
 install: all
diff --git a/policycoreutils/run_init/open_init_pty.c b/policycoreutils/run_init/open_init_pty.c
deleted file mode 100644
index 4f04e72..0000000
--- a/policycoreutils/run_init/open_init_pty.c
+++ /dev/null
@@ -1,399 +0,0 @@
-/*                               -*- Mode: C -*- 
- * open_init_pty.c --- 
- * Author           : Manoj Srivastava ( srivasta@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ) 
- * Created On       : Fri Jan 14 10:48:28 2005
- * Created On Node  : glaurung.internal.golden-gryphon.com
- * Last Modified By : Manoj Srivastava
- * Last Modified On : Thu Sep 15 00:57:00 2005
- * Last Machine Used: glaurung.internal.golden-gryphon.com
- * Update Count     : 92
- * Status           : Unknown, Use with caution!
- * HISTORY          : 
- * Description      : 
- *
- * Distributed under the terms of the GNU General Public License v2
- *
- * open_init_pty
- *
- * SYNOPSIS:
- *
- * This program allows a systems administrator to execute daemons
- * which need to work in the initrc domain, and which need to have
- * pty's as system_u:system_r:initrc_t
- *
- * USAGE:
- *
- * * arch-tag: a5583d39-72b9-4cdf-ba1b-5678ea4cbe20
- */
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <signal.h>
-#include <errno.h>
-
-#include <sysexits.h>
-
-#include <pty.h>		/* for openpty and forkpty */
-#include <utmp.h>		/* for login_tty */
-#include <termios.h>
-#include <fcntl.h>
-
-#include <sys/select.h>
-
-static struct termios saved_termios;
-static int saved_fd = -1;
-static enum { RESET, RAW, CBREAK } tty_state = RESET;
-
-static int tty_semi_raw(int fd)
-{
-	struct termios buf;
-
-	if (tty_state == RESET) {
-		if (tcgetattr(fd, &saved_termios) < 0) {
-			return -1;
-		}
-	}
-
-	buf = saved_termios;
-	/*
-	 * echo off, canonical mode off, extended input processing off,
-	 * signal chars off 
-	 */
-	buf.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
-	/*
-	 * no SIGINT on break, CR-to-NL off, input parity check off, do not
-	 * strip 8th bit on input,output flow control off
-	 */
-	buf.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
-	/* Clear size bits, parity checking off */
-	buf.c_cflag &= ~(CSIZE | PARENB);
-	/* set 8 bits/char */
-	buf.c_cflag |= CS8;
-	/* Output processing off 
-	   buf.c_oflag    &= ~(OPOST); */
-
-	buf.c_cc[VMIN] = 1;	/* one byte at a time, no timer */
-	buf.c_cc[VTIME] = 0;
-	if (tcsetattr(fd, TCSANOW, &buf) < 0) {
-		return -1;
-	}			/* end of if(tcsetattr(fileno(stdin), TCSANOW, &buf) < 0) */
-	tty_state = RAW;
-	saved_fd = fd;
-	return 0;
-}
-
-void tty_atexit(void)
-{
-	if (tty_state != CBREAK && tty_state != RAW) {
-		return;
-	}
-
-	if (tcsetattr(saved_fd, TCSANOW, &saved_termios) < 0) {
-		return;
-	}			/* end of if(tcsetattr(fileno(stdin), TCSANOW, &buf) < 0) */
-	tty_state = RESET;
-	return;
-}
-
-int main(int argc, char *argv[])
-{
-	pid_t child_pid;
-	struct termios tty_attr;
-	struct winsize window_size;
-	int pty_master;
-	int retval = 0;
-
-	/* for select */
-	fd_set readfds;
-	fd_set writefds;
-	fd_set exceptfds;
-
-	int err_count = 0;
-
-	/* for sigtimedwait() */
-	struct timespec timeout;
-	char buf[16384];
-
-	if (argc == 1) {
-		printf("usage: %s PROGRAM [ARGS]...\n", argv[0]);
-		exit(1);
-	}
-
-	sigset_t signal_set;
-	siginfo_t signalinfo;
-
-	/* set up SIGCHLD */
-	sigemptyset(&signal_set);	/* no signals */
-	sigaddset(&signal_set, SIGCHLD);	/* Add sig child  */
-	sigprocmask(SIG_BLOCK, &signal_set, NULL);	/* Block the signal */
-
-	/* Set both to 0, so sigtimed wait just does a poll */
-	timeout.tv_sec = 0;
-	timeout.tv_nsec = 0;
-
-	if (isatty(fileno(stdin))) {
-		/* get terminal parameters associated with stdout */
-		if (tcgetattr(fileno(stdout), &tty_attr) < 0) {
-			perror("tcgetattr:");
-			exit(EX_OSERR);
-		}
-
-		/* end of if(tcsetattr(&tty_attr)) */
-		/* get window size */
-		if (ioctl(fileno(stdout), TIOCGWINSZ, &window_size) < 0) {
-			perror("ioctl stdout:");
-			exit(1);
-		}
-
-		child_pid = forkpty(&pty_master, NULL, &tty_attr, &window_size);
-	} /* end of if(isatty(fileno(stdin))) */
-	else {			/* not interactive */
-		child_pid = forkpty(&pty_master, NULL, NULL, NULL);
-	}
-
-	if (child_pid < 0) {
-		perror("forkpty():");
-		fflush(stdout);
-		fflush(stderr);
-		exit(EX_OSERR);
-	}			/* end of if(child_pid < 0) */
-	if (child_pid == 0) {
-		/* in the child */
-		struct termios s_tty_attr;
-		if (tcgetattr(fileno(stdin), &s_tty_attr)) {
-			perror("Child:");
-			fflush(stdout);
-			fflush(stderr);
-			exit(EXIT_FAILURE);
-		}
-		/* Turn off echo */
-		s_tty_attr.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
-		/* Also turn of NL to CR?LF on output */
-		s_tty_attr.c_oflag &= ~(ONLCR);
-		if (tcsetattr(fileno(stdin), TCSANOW, &s_tty_attr)) {
-			perror("Child:");
-			exit(EXIT_FAILURE);
-		}
-		{		/* There is no reason to block sigchild for the process we
-				   shall exec here */
-			sigset_t chld_signal_set;
-			/* release SIGCHLD */
-			sigemptyset(&chld_signal_set);	/* no signals */
-			sigaddset(&chld_signal_set, SIGCHLD);	/* Add sig child  */
-			sigprocmask(SIG_UNBLOCK, &chld_signal_set, NULL);	/* Unblock the signal */
-		}
-
-		if (execvp(argv[1], argv + 1)) {
-			perror("Exec:");
-			fflush(stdout);
-			fflush(stderr);
-			exit(EXIT_FAILURE);
-		}
-	}
-
-	/* end of if(child_pid == 0) */
-	/* 
-	 * OK. Prepare to handle IO from the child. We need to transfer
-	 * everything from the child's stdout to ours.
-	 */
-	FD_ZERO(&readfds);
-	FD_ZERO(&writefds);
-	FD_ZERO(&exceptfds);
-
-	/*
-	 * Read current file descriptor flags, preparing to do non blocking reads
-	 */
-	retval = fcntl(pty_master, F_GETFL);
-	if (retval < 0) {
-		perror("fcntl_get");
-		fflush(stdout);
-		fflush(stderr);
-		exit(EX_IOERR);
-	}
-
-	/* Set the connection to be non-blocking */
-	if (fcntl(pty_master, F_SETFL, retval | O_NONBLOCK) < 0) {
-		perror("fcnt_setFlag_nonblock:");
-		fflush(stdout);
-		fflush(stderr);
-		exit(1);
-	}
-
-	FD_SET(pty_master, &readfds);
-	FD_SET(pty_master, &writefds);
-	FD_SET(fileno(stdin), &readfds);
-	if (isatty(fileno(stdin))) {
-		if (tty_semi_raw(fileno(stdin)) < 0) {
-			perror("Error: settingraw mode:");
-			fflush(stdout);
-			fflush(stderr);
-		}		/* end of if(tty_raw(fileno(stdin)) < 0) */
-		if (atexit(tty_atexit) < 0) {
-			perror("Atexit setup:");
-			fflush(stdout);
-			fflush(stderr);
-		}		/* end of if(atexit(tty_atexit) < 0) */
-	}
-
-	/* ignore return from nice, but lower our priority */
-	int ignore __attribute__ ((unused)) = nice(19);
-
-	/* while no signal, we loop around */
-	int done = 0;
-	while (!done) {
-		struct timeval interval;
-		fd_set t_readfds;
-		fd_set t_writefds;
-		fd_set t_exceptfds;
-		/*
-		 * We still use a blocked signal, and check for SIGCHLD every
-		 * loop, since waiting infinitely did not really help the load
-		 * when running, say, top. 
-		 */
-		interval.tv_sec = 0;
-		interval.tv_usec = 200000;	/* so, check for signals every 200 milli
-						   seconds */
-
-		t_readfds = readfds;
-		t_writefds = writefds;
-		t_exceptfds = exceptfds;
-
-		/* check for the signal */
-		retval = sigtimedwait(&signal_set, &signalinfo, &timeout);
-
-		if (retval == SIGCHLD) {
-			/* child terminated */
-			done = 1;	/* in case they do not close off their
-					   file descriptors */
-		} else {
-			if (retval < 0) {
-				if (errno != EAGAIN) {
-					perror("sigtimedwait");
-					fflush(stdout);
-					fflush(stderr);
-					exit(EX_IOERR);
-				} else {
-					/* No signal in set was delivered within the timeout period specified */
-				}
-			}
-		}		/* end of else */
-
-		if (select
-		    (pty_master + 1, &t_readfds, &t_writefds, &t_exceptfds,
-		     &interval) < 0) {
-			perror("Select:");
-			fflush(stdout);
-			fflush(stderr);
-			exit(EX_IOERR);
-		}
-
-		if (FD_ISSET(pty_master, &t_readfds)) {
-			retval = read(pty_master, buf, (unsigned int)16384);
-			if (retval < 0) {
-				if (errno != EINTR && errno != EAGAIN) {	/* Nothing left to read?  */
-					fflush(stdout);
-					fflush(stderr);
-					/* fprintf(stderr, "DEBUG: %d: Nothing left to read?\n", __LINE__); */
-					exit(EXIT_SUCCESS);
-				}	/* end of else */
-			} /* end of if(retval < 0) */
-			else {
-				if (retval == 0) {
-					if (++err_count > 5) {	/* child closed connection */
-						fflush(stdout);
-						fflush(stderr);
-						/*fprintf(stderr, "DEBUG: %d: child closed connection?\n", __LINE__); */
-						exit(EXIT_SUCCESS);
-					}
-				} /* end of if(retval == 0) */
-				else {
-					ssize_t nleft = retval;
-					ssize_t nwritten = 0;
-					char *ptr = buf;
-					while (nleft > 0) {
-						if ((nwritten =
-						     write(fileno(stdout), ptr,
-							   (unsigned int)nleft))
-						    <= 0) {
-							if (errno == EINTR) {
-								nwritten = 0;
-							} /* end of if(errno == EINTR) */
-							else {
-								perror("write");
-								fflush(stdout);
-								fflush(stderr);
-								exit(EXIT_SUCCESS);
-							}	/* end of else */
-						}	/* end of if((nwritten = write(sockfd, ptr, nleft)) <= 0) */
-						nleft -= nwritten;
-						ptr += nwritten;
-					}	/* end of while(nleft > 0) */
-
-					/* fprintf(stderr, "DEBUG: %d: wrote %d\n", __LINE__, retval); */
-					fflush(stdout);
-				}	/* end of else */
-			}	/* end of else */
-		}
-		if (FD_ISSET(fileno(stdin), &t_readfds)) {
-			if (FD_ISSET(pty_master, &t_writefds)) {
-				retval =
-				    read(fileno(stdin), buf,
-					 (unsigned int)16384);
-				if (retval < 0) {
-					if (errno != EINTR && errno != EAGAIN) {	/* Nothing left to read?  */
-						fflush(stdout);
-						fflush(stderr);
-						exit(EXIT_SUCCESS);
-					}	/* end of else */
-				} /* end of if(retval < 0) */
-				else {
-					if (retval == 0) {
-						if (++err_count > 5) {	/* lost controlling tty */
-							fflush(stdout);
-							fflush(stderr);
-							exit(EXIT_SUCCESS);
-						}
-					} /* end of if(retval == 0) */
-					else {
-						ssize_t nleft = retval;
-						ssize_t nwritten = 0;
-						char *ptr = buf;
-						while (nleft > 0) {
-							if ((nwritten =
-							     write(pty_master,
-								   ptr,
-								   (unsigned
-								    int)nleft))
-							    <= 0) {
-								if (errno ==
-								    EINTR) {
-									nwritten
-									    = 0;
-								} /* end of if(errno == EINTR) */
-								else {
-									perror
-									    ("write");
-									fflush
-									    (stdout);
-									fflush
-									    (stderr);
-									exit(EXIT_SUCCESS);
-								}	/* end of else */
-							}	/* end of if((nwritten = write(sockfd, ptr, nleft)) <= 0) */
-							nleft -= nwritten;
-							ptr += nwritten;
-						}	/* end of while(nleft > 0) */
-
-						fflush(stdout);
-					}	/* end of else */
-				}	/* end of else */
-			}	/* end of if(FD_ISSET(pty_master, &writefds)) */
-		}		/* something to read on stdin */
-	}			/* Loop */
-
-	fflush(stdout);
-	fflush(stderr);
-
-	exit(EXIT_SUCCESS);
-}				/* end of main() */
diff --git a/policycoreutils/run_init/open_init_pty.cpp b/policycoreutils/run_init/open_init_pty.cpp
new file mode 100644
index 0000000..b82f7f5
--- /dev/null
+++ b/policycoreutils/run_init/open_init_pty.cpp
@@ -0,0 +1,423 @@
+/*                               -*- Mode: C -*-
+ * open_init_pty.c ---
+ * Author           : Manoj Srivastava ( srivasta@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx )
+ * Created On       : Fri Jan 14 10:48:28 2005
+ * Created On Node  : glaurung.internal.golden-gryphon.com
+ * Last Modified By : Manoj Srivastava
+ * Last Modified On : Thu Sep 15 00:57:00 2005
+ * Last Machine Used: glaurung.internal.golden-gryphon.com
+ * Update Count     : 92
+ * Status           : Unknown, Use with caution!
+ * HISTORY          :
+ * Description      :
+ *
+ * Distributed under the terms of the GNU General Public License v2
+ *
+ * open_init_pty
+ *
+ * SYNOPSIS:
+ *
+ * This program allows a systems administrator to execute daemons
+ * which need to work in the initrc domain, and which need to have
+ * pty's as system_u:system_r:initrc_t
+ *
+ * USAGE:
+ *
+ * * arch-tag: a5583d39-72b9-4cdf-ba1b-5678ea4cbe20
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <signal.h>
+#include <errno.h>
+
+#include <sysexits.h>
+
+#include <pty.h>    /* for openpty and forkpty */
+#include <utmp.h>    /* for login_tty */
+#include <termios.h>
+#include <fcntl.h>
+
+#include <sys/select.h>
+#include <sys/wait.h>
+
+
+#define MAXRETR 3    /* The max number of IO retries on a fd */
+#define BUFSIZE 2048  /* The ring buffer size */
+
+static struct termios saved_termios;
+static int saved_fd = -1;
+static enum { RESET, RAW, CBREAK } tty_state = RESET;
+
+static int tty_semi_raw(int fd)
+{
+  struct termios buf;
+
+  if (tty_state == RESET) {
+    if (tcgetattr(fd, &saved_termios) < 0) {
+      return -1;
+    }
+  }
+
+  buf = saved_termios;
+  /*
+   * echo off, canonical mode off, extended input processing off,
+   * signal chars off
+   */
+  buf.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
+  /*
+   * no SIGINT on break, CR-to-NL off, input parity check off, do not
+   * strip 8th bit on input,output flow control off
+   */
+  buf.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
+  /* Clear size bits, parity checking off */
+  buf.c_cflag &= ~(CSIZE | PARENB);
+  /* set 8 bits/char */
+  buf.c_cflag |= CS8;
+  /* Output processing off
+     buf.c_oflag    &= ~(OPOST); */
+
+  buf.c_cc[VMIN] = 1;  /* one byte at a time, no timer */
+  buf.c_cc[VTIME] = 0;
+  if (tcsetattr(fd, TCSANOW, &buf) < 0) {
+    return -1;
+  }
+  tty_state = RAW;
+  saved_fd = fd;
+  return 0;
+}
+
+static void tty_atexit(void)
+{
+  if (tty_state != CBREAK && tty_state != RAW) {
+    return;
+  }
+
+  if (tcsetattr(saved_fd, TCSANOW, &saved_termios) < 0) {
+    return;
+  }
+  tty_state = RESET;
+  return;
+}
+
+
+/* The simple ring buffer */
+class ring_buffer
+{
+public:
+  ring_buffer(char *buf, size_t size)
+  {
+    m_buf = m_wptr = m_rptr = buf;
+    m_size = size;
+    m_count = 0;
+  }
+
+  size_t get_count() { return m_count; }
+  int isempty() { return m_count == 0; }
+
+  // return the unused space size in the buffer
+  size_t space()
+  {
+    if(m_rptr > m_wptr)
+      return m_rptr - m_wptr;
+    if(m_rptr < m_wptr || m_count == 0)
+      return m_buf + m_size - m_wptr;
+    return 0; // should not hit this
+  }
+
+  // return the used space in the buffer
+  size_t chunk_size()
+  {
+    if(m_rptr < m_wptr)
+      return m_wptr - m_rptr;
+    if(m_rptr > m_wptr || m_count > 0)
+      return m_buf + m_size - m_rptr;
+    return 0; // should not hit this
+  }
+
+  // read from fd and write to buffer memory
+  ssize_t rb_read(int fd)
+  {
+    ssize_t n = read(fd, m_wptr, space());
+    if(n <= 0)
+      return n;
+    m_wptr += n;
+    m_count += n;
+    if(m_buf + m_size <= m_wptr)
+      m_wptr = m_buf;
+    return n;
+  }
+
+  ssize_t rb_write(int fd)
+  {
+    ssize_t n = write(fd, m_rptr, chunk_size());
+    if(n <= 0)
+      return n;
+    m_rptr += n;
+    m_count -= n;
+    if(m_buf + m_size <= m_rptr)
+      m_rptr = m_buf;
+    return n;
+  }
+
+private:
+    char *m_buf; /* pointer to buffer memory */
+    char *m_wptr;
+    char *m_rptr;
+    size_t m_size; /* the number of bytes allocated for buf */
+    size_t m_count;
+};
+
+static void setfd_nonblock(int fd)
+{
+  int fsflags = fcntl(fd, F_GETFL);
+
+  if (fsflags < 0) {
+    fprintf(stderr, "fcntl(%d, F_GETFL): %s\n",
+        fd, strerror(errno));
+    exit(EX_IOERR);
+  }
+
+  if (fcntl(STDIN_FILENO, F_SETFL, fsflags | O_NONBLOCK) < 0) {
+    fprintf(stderr, "fcntl(%d, F_SETFL, ... | O_NONBLOCK): %s\n",
+        fd, strerror(errno));
+    exit(EX_IOERR);
+  }
+}
+
+static void sigchld_handler(int asig __attribute__ ((unused)))
+{
+}
+
+int main(int argc, char *argv[])
+{
+  pid_t child_pid;
+  int child_exit_status;
+  struct termios tty_attr;
+  struct winsize window_size;
+  int pty_master;
+  char inbuf_mem[BUFSIZE];
+  char outbuf_mem[BUFSIZE];
+  ring_buffer inbuf(inbuf_mem, sizeof(inbuf_mem));
+  ring_buffer outbuf(outbuf_mem, sizeof(outbuf_mem));
+
+  if (argc == 1) {
+    printf("usage: %s PROGRAM [ARGS]...\n", argv[0]);
+    exit(1);
+  }
+
+  /* Wee need I/O calls to fail with EINTR on SIGCHLD... */
+  if ( signal(SIGCHLD, sigchld_handler) == SIG_ERR ) {
+    perror("signal(SIGCHLD,...)");
+    exit(EX_OSERR);
+  }
+
+  if (isatty(STDIN_FILENO)) {
+    /* get terminal parameters associated with stdout */
+    if (tcgetattr(STDOUT_FILENO, &tty_attr) < 0) {
+      perror("tcgetattr(stdout,...)");
+      exit(EX_OSERR);
+    }
+
+    /* end of if(tcsetattr(&tty_attr)) */
+    /* get window size */
+    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &window_size) < 0) {
+      perror("ioctl(stdout,...)");
+      exit(1);
+    }
+
+    child_pid = forkpty(&pty_master, NULL, &tty_attr, &window_size);
+  } /* end of if(isatty(STDIN_FILENO)) */
+  else {      /* not interactive */
+    child_pid = forkpty(&pty_master, NULL, NULL, NULL);
+  }
+
+  if (child_pid < 0) {
+    perror("forkpty()");
+    fflush(stdout);
+    fflush(stderr);
+    exit(EX_OSERR);
+  }      /* end of if(child_pid < 0) */
+  if (child_pid == 0) {
+    /* in the child */
+    struct termios s_tty_attr;
+    if (tcgetattr(STDIN_FILENO, &s_tty_attr)) {
+      perror("tcgetattr(stdin,...)");
+      exit(EXIT_FAILURE);
+    }
+    /* Turn off echo */
+    s_tty_attr.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
+    /* Also turn of NL to CR?LF on output */
+    s_tty_attr.c_oflag &= ~(ONLCR);
+    if (tcsetattr(STDIN_FILENO, TCSANOW, &s_tty_attr)) {
+      perror("tcsetattr(stdin,...)");
+      exit(EXIT_FAILURE);
+    }
+
+    if (execvp(argv[1], argv + 1)) {
+      perror("execvp()");
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  /*
+   * Non blocking mode for all file descriptors.
+   */
+  setfd_nonblock(pty_master);
+  setfd_nonblock(STDIN_FILENO);
+  setfd_nonblock(STDOUT_FILENO);
+
+  if (isatty(STDIN_FILENO)) {
+    if (tty_semi_raw(STDIN_FILENO) < 0) {
+      perror("tty_semi_raw(stdin)");
+    }
+    if (atexit(tty_atexit) < 0) {
+      perror("atexit()");
+    }
+  }
+
+  /* for select()... */
+  fd_set readfds;
+  fd_set writefds;
+  fd_set exceptfds;
+  FD_ZERO(&readfds);
+  FD_ZERO(&writefds);
+  FD_ZERO(&exceptfds);
+
+  unsigned err_n_rpty = 0;
+  unsigned err_n_wpty = 0;
+  unsigned err_n_stdin = 0;
+  unsigned err_n_stdout = 0;
+
+  int done = 0;
+
+  do {
+    /* Accept events only on fds, that we can handle now. */
+    int do_select = 0;
+
+    if ( outbuf.space() > 0  &&  err_n_rpty < MAXRETR ) {
+      FD_SET(pty_master, &readfds);
+      do_select = 1;
+    } else
+      FD_CLR(pty_master, &readfds);
+
+    if ( ! inbuf.isempty()  &&  err_n_wpty < MAXRETR ) {
+      FD_SET(pty_master, &writefds);
+      do_select = 1;
+    } else
+      FD_CLR(pty_master, &writefds);
+
+    if ( inbuf.space() > 0  &&  err_n_stdin < MAXRETR ) {
+      FD_SET(STDIN_FILENO, &readfds);
+      do_select = 1;
+    } else
+      FD_CLR(STDIN_FILENO, &readfds);
+
+    if ( ! outbuf.isempty()  &&  err_n_stdout < MAXRETR ) {
+      FD_SET(STDOUT_FILENO, &writefds);
+      do_select = 1;
+    } else
+      FD_CLR(STDOUT_FILENO, &writefds);
+
+    if ( ! do_select )
+    {
+#ifdef DEBUG
+      fprintf(stderr, "No I/O job for us, calling waitpid()...\n");
+#endif
+        while ( waitpid(child_pid, &child_exit_status, 0) < 0 )
+        ;
+      break;
+    }
+
+    int select_rc = select(pty_master + 1,
+        &readfds, &writefds, &exceptfds, NULL);
+    if ( select_rc < 0 ) {
+      perror("select()");
+      exit(EX_IOERR);
+    }
+#ifdef DEBUG
+    fprintf(stderr, "select() returned %d\n", select_rc);
+#endif
+
+    if (FD_ISSET(STDOUT_FILENO, &writefds)) {
+#ifdef DEBUG
+        fprintf(stderr, "stdout can be written\n");
+#endif
+        ssize_t n = outbuf.rb_write(STDOUT_FILENO);
+        if ( n <= 0 && n != EINTR && n != EAGAIN )
+        err_n_stdout++;
+#ifdef DEBUG
+        if ( n >= 0 )
+        fprintf(stderr, "%d bytes written into stdout\n", n);
+        else
+        perror("write(stdout,...)");
+#endif
+    }
+    if (FD_ISSET(pty_master, &writefds)) {
+#ifdef DEBUG
+        fprintf(stderr, "pty_master can be written\n");
+#endif
+        ssize_t n = inbuf.rb_write(pty_master);
+        if ( n <= 0 && n != EINTR && n != EAGAIN )
+        err_n_wpty++;
+#ifdef DEBUG
+        if ( n >= 0 )
+        fprintf(stderr, "%d bytes written into pty_master\n", n);
+        else
+        perror("write(pty_master,...)");
+#endif
+    }
+    if (FD_ISSET(STDIN_FILENO, &readfds)) {
+#ifdef DEBUG
+        fprintf(stderr, "stdin can be read\n");
+#endif
+        ssize_t n = inbuf.rb_read(STDIN_FILENO);
+        if ( n <= 0 && n != EINTR && n != EAGAIN )
+        err_n_stdin++;
+#ifdef DEBUG
+        if ( n >= 0 )
+        fprintf(stderr, "%d bytes read from stdin\n", n);
+        else
+        perror("read(stdin,...)");
+#endif
+    }
+    if (FD_ISSET(pty_master, &readfds)) {
+#ifdef DEBUG
+        fprintf(stderr, "pty_master can be read\n");
+#endif
+        ssize_t n = outbuf.rb_read(pty_master);
+        if ( n <= 0 && n != EINTR && n != EAGAIN )
+        err_n_rpty++;
+#ifdef DEBUG
+        if ( n >= 0 )
+        fprintf(stderr, "%d bytes read from pty_master\n", n);
+        else
+        perror("read(pty_master,...)");
+#endif
+    }
+
+    if ( ! done )
+        if ( waitpid(child_pid, &child_exit_status, WNOHANG) > 0 )
+        done = 1;
+
+  } while ( !done
+      || !(inbuf.isempty() || err_n_wpty >= MAXRETR)
+        || !(outbuf.isempty() || err_n_stdout >= MAXRETR) );
+
+#ifdef DEBUG
+  fprintf(stderr, "inbuf: %u bytes left, outbuf: %u bytes left\n",
+      inbuf.get_count(), outbuf.get_count());
+  fprintf(stderr, "err_n_rpty=%u, err_n_wpty=%u, "
+      "err_n_stdin=%u, err_n_stdout=%u\n",
+      err_n_rpty, err_n_wpty, err_n_stdin, err_n_stdout);
+#endif
+  if ( WIFEXITED(child_exit_status) )
+    exit(WEXITSTATUS(child_exit_status));
+  exit(EXIT_FAILURE);
+}        /* end of main() */
+
+/*
+ * vim:ts=4:
+ */
-- 
1.7.10.4


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