Revert "Speed up 'read', fixing macOS hang"

This reverts commit ff385e5a89.
It broke Solaris and illumos. More testing is needed.

NEWS

@@ -3,11 +3,6 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
-2020-08-18:
-
-- Sped up the 'read' command on most systems by 15-25%. Fixed a hanging bug
-  on reading from a FIFO that could occur on macOS.
-
 2020-08-17:
 
 - 'command -p' incorrectly used the hash table entry (a.k.a. tracked alias)

src/cmd/ksh93/include/version.h

@@ -17,4 +17,4 @@
 *                  David Korn <dgk@research.att.com>                   *
 *                                                                      *
 ***********************************************************************/
-#define SH_RELEASE	"93u+m 2020-08-18"
+#define SH_RELEASE	"93u+m 2020-08-17"

src/cmd/ksh93/tests/io.sh

@@ -583,19 +583,5 @@ then	exec 3>&-
 	err_exit "Open file descriptor leaks out of subshell"
 fi
 
-# ======
-# On unpatched ksh on macOS, 'read' used to block when reading from a FIFO and there was no final newline.
-if	mkfifo "$tmp/fifo_no_lf"
-then	trap 'sleep_pid=0; kill "$ksh_pid"; err_exit "'\''read'\'' hangs on EOF without final linefeed when reading from FIFO"' TERM
-	(sleep 1; kill "$$") &
-	sleep_pid=$!
-	"$SHELL" -c 'print -n foo >$0 & while read f; do :; done <$0' "$tmp/fifo_no_lf" &
-	ksh_pid=$!
-	wait "$ksh_pid"
-	trap - TERM
-	((sleep_pid)) && kill "$sleep_pid"
-else	err_exit "mkfifo failed; cannot test reading from FIFO"
-fi
-
 # ======
 exit $((Errors<125?Errors:125))

src/lib/libast/sfio/sfpkrd.c

@@ -20,12 +20,11 @@
 *                                                                      *
 ***********************************************************************/
 #include	"sfhdr.h"
-
+#if !_PACKAGE_ast
-#if !_socket_peek
+#ifndef FIONREAD
-#if __APPLE__
+#if _sys_ioctl
-#error The socket_peek feature is required. (Hey Apple, revert your src__lib__libast__features__lib.diff patch; it caused multiple regressions, and the hanging bug it fixed is now fixed correctly. See <https://github.com/ksh93/ksh/issues/118>.)
+#include	<sys/ioctl.h>
-#else
+#endif
-#error The socket_peek feature is required.
 #endif
 #endif
 
@@ -34,6 +33,9 @@
 **	Written by Kiem-Phong Vo.
 */
 
+#define STREAM_PEEK	001
+#define SOCKET_PEEK	002
+
 #if __STD_C
 ssize_t sfpkrd(int fd, Void_t* argbuf, size_t n, int rc, long tm, int action)
 #else
@@ -50,28 +52,237 @@ int	action;	/* >0: peeking, if rc>=0, get action records,
 #endif
 {
 	reg ssize_t	r;
-	reg int		t;
+	reg int		ntry, t;
 	reg char	*buf = (char*)argbuf, *endbuf;
 
 	if(rc < 0 && tm < 0 && action <= 0)
 		return sysreadf(fd,buf,n);
 
-	r = -1;
+	t = (action > 0 || rc >= 0) ? (STREAM_PEEK|SOCKET_PEEK) : 0;
-	t = action > 0 || rc >= 0;	/* socket peek using recv(2)? */
+#if !_stream_peek
-	if(t)
+	t &= ~STREAM_PEEK;
-	{	while(t && (r = recv(fd,(char*)buf,n,MSG_PEEK)) < 0)
+#endif
-		{	if(errno == EINTR)
+#if !_socket_peek
+	t &= ~SOCKET_PEEK;
+#endif
+
+	for(ntry = 0; ntry < 2; ++ntry)
+	{
+		r = -1;
+#if _stream_peek
+		if((t&STREAM_PEEK) && (ntry == 1 || tm < 0) )
+		{
+#ifdef __sun
+			/*
+			 * I_PEEK on stdin can hang rsh+ksh on solaris
+			 * this kludge will have to do until sun^H^H^Horacle fixes I_PEEK/rsh
+			 */
+			static int	stream_peek;
+			if (stream_peek == 0) /* this will be done just once */
+			{	char	*e;
+				stream_peek = (
+					getenv("LOGNAME") == 0 &&
+					getenv("MAIL") == 0 &&
+					((e = getenv("LANG")) == 0 || strcmp(e, "C") == 0) &&
+					((e = getenv("PATH")) == 0 || strncmp(e, "/usr/bin:", 9) == 0)
+					) ? -1 : 1;
+			}
+			if(stream_peek < 0)
+				t &= ~STREAM_PEEK;
+			else
+#endif
+			{	struct strpeek	pbuf;
+				pbuf.flags = 0;
+				pbuf.ctlbuf.maxlen = -1;
+				pbuf.ctlbuf.len = 0;
+				pbuf.ctlbuf.buf = NIL(char*);
+				pbuf.databuf.maxlen = n;
+				pbuf.databuf.buf = buf;
+				pbuf.databuf.len = 0;
+
+				if((r = ioctl(fd,I_PEEK,&pbuf)) < 0)
+				{	if(errno == EINTR)
+						return -1;
+					t &= ~STREAM_PEEK;
+				}
+				else
+				{	t &= ~SOCKET_PEEK;
+					if(r > 0 && (r = pbuf.databuf.len) <= 0)
+					{	if(action <= 0)	/* read past eof */
+							r = sysreadf(fd,buf,1);
+						return r;
+					}
+					if(r == 0)
+						r = -1;
+					else if(r > 0)
+						break;
+				}
+			}
+		}
+#endif /* stream_peek */
+
+		if(ntry == 1)
+			break;
+
+		/* poll or select to see if data is present.  */
+		while(tm >= 0 || action > 0 ||
+			/* block until there is data before peeking again */
+			((t&STREAM_PEEK) && rc >= 0) ||
+			/* let select be interrupted instead of recv which autoresumes */
+			(t&SOCKET_PEEK) )
+		{	r = -2;
+#if _lib_poll
+			if(r == -2)
+			{
+				struct pollfd	po;
+				po.fd = fd;
+				po.events = POLLIN;
+				po.revents = 0;
+
+				if((r = SFPOLL(&po,1,tm)) < 0)
+				{	if(errno == EINTR)
+						return -1;
+					else if(errno == EAGAIN)
+					{	errno = 0;
+						continue;
+					}
+					else	r = -2;
+				}
+				else	r = (po.revents&POLLIN) ? 1 : -1;
+			}
+#endif /*_lib_poll*/
+#if _lib_select
+			if(r == -2)
+			{
+#if _hpux_threads && vt_threaded
+#define fd_set	int
+#endif
+				fd_set		rd;
+				struct timeval	tmb, *tmp;
+				FD_ZERO(&rd);
+				FD_SET(fd,&rd);
+				if(tm < 0)
+					tmp = NIL(struct timeval*);
+				else
+				{	tmp = &tmb;
+					tmb.tv_sec = tm/SECOND;
+					tmb.tv_usec = (tm%SECOND)*SECOND;
+				}
+				r = select(fd+1,&rd,NIL(fd_set*),NIL(fd_set*),tmp);
+				if(r < 0)
+				{	if(errno == EINTR)
+						return -1;
+					else if(errno == EAGAIN)
+					{	errno = 0;
+						continue;
+					}
+					else	r = -2;
+				}
+				else	r = FD_ISSET(fd,&rd) ? 1 : -1;
+			}
+#endif /*_lib_select*/
+			if(r == -2)
+			{
+#if !_lib_poll && !_lib_select	/* both poll and select can't be used */
+#ifdef FIONREAD			/* quick and dirty check for availability */
+				long	nsec = tm < 0 ? 0 : (tm+999)/1000;
+				while(nsec > 0 && r < 0)
+				{	long	avail = -1;
+					if((r = ioctl(fd,FIONREAD,&avail)) < 0)
+					{	if(errno == EINTR)
+							return -1;
+						else if(errno == EAGAIN)
+						{	errno = 0;
+							continue;
+						}
+						else	/* ioctl failed completely */
+						{	r = -2;
+							break;
+						}
+					}
+					else	r = avail <= 0 ? -1 : (ssize_t)avail;
+
+					if(r < 0 && nsec-- > 0)
+						sleep(1);
+				}
+#endif
+#endif
+			}
+
+			if(r > 0)		/* there is data now */
+			{	if(action <= 0 && rc < 0)
+					return sysreadf(fd,buf,n);
+				else	r = -1;
+			}
+			else if(tm >= 0)	/* timeout exceeded */
 				return -1;
-			else if(errno == EAGAIN)
+			else	r = -1;
-				errno = 0;
+			break;
-			else	t = 0;
 		}
-		if(r == 0)
+
-		{	/* read past eof */
+#if _socket_peek
-			if(action <= 0)
+		if(t&SOCKET_PEEK)
-				r = sysreadf(fd,buf,1);
+		{
-			return r;
+#if __MACH__ && __APPLE__ /* check 10.4 recv(MSG_PEEK) bug that consumes pipe data */
+			static int	recv_peek_pipe;
+			if (recv_peek_pipe == 0) /* this will be done just once */
+			{	int	fds[2], r;
+				char	tst[2];
+
+				tst[0] = 'a'; tst[1] = 'z';
+
+				/* open a pipe and write to it */
+				recv_peek_pipe = 1;
+				if(recv_peek_pipe == 1 && pipe(fds) < 0)
+					recv_peek_pipe = -1;
+				if(recv_peek_pipe == 1 && write(fds[1], tst, 2) != 2)
+					recv_peek_pipe = -1;
+
+				/* try recv() to see if it gets anything */
+				tst[0] = tst[1] = 0;
+				if(recv_peek_pipe == 1 && (r = recv(fds[0], tst, 1, MSG_PEEK)) != 1)
+					recv_peek_pipe = -1;
+				if(recv_peek_pipe == 1 && tst[0] != 'a')
+					recv_peek_pipe = -1;
+
+				/* make sure that recv() did not consume data */
+				tst[0] = tst[1] = 0;
+				if(recv_peek_pipe == 1 && (r = recv(fds[0], tst, 2, MSG_PEEK)) != 2)
+					recv_peek_pipe = -1;
+				if(recv_peek_pipe == 1 && (tst[0] != 'a' || tst[1] != 'z') )
+					recv_peek_pipe = -1;
+
+				close(fds[0]);
+				close(fds[1]);
+			}
+
+			if(recv_peek_pipe < 0)
+			{	struct stat st; /* recv should work on sockets */
+				if(fstat(fd, &st) < 0 || !S_ISSOCK(st.st_mode) )
+				{	r = -1;
+					t &= ~SOCKET_PEEK;
+				}
+			}
+#endif
+			while((t&SOCKET_PEEK) && (r = recv(fd,(char*)buf,n,MSG_PEEK)) < 0)
+			{	if(errno == EINTR)
+					return -1;
+				else if(errno == EAGAIN)
+					errno = 0;
+				else	t &= ~SOCKET_PEEK;
+			}
+			if(r >= 0)
+			{	t &= ~STREAM_PEEK;
+				if(r > 0)
+					break;
+				else	/* read past eof */
+				{	if(action <= 0)
+						r = sysreadf(fd,buf,1);
+					return r;
+				}
+			}
 		}
+#endif
 	}
 
 	if(r < 0)