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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<ctype.h>
+include	<syserr.h>
+include	<chars.h>
+include	<config.h>
+include	<knet.h>
+include	<fio.h>
+
+.help vfntrans
+.nf ___________________________________________________________________________
+VFNTRANS -- Procedures for translating VFN's to OSFN's and back again in
+memory.  These procedures are called by the VFNMAP procedures, but do not
+access the VFN database.  This package contains most of the knowledge of the
+characteristics of OS filenames.  The characteristics of OS filenames (max
+length, extensions, etc.) are defined in <config.h>.
+
+	    vfn_translate (vfn, osdir, lenosdir, root, lenroot, extn, lenextn)
+	  vfn_expand_ldir (vfn, outstr, maxch)
+	       vfn_encode (vfn, ip, root, lenroot, extn, lenextn)
+      nchars = vfn_decode (osfn, ip, vfn, maxch)
+        vfn_map_extension (iraf_extn, os_extn, maxch)
+      vfn_unmap_extension (iraf_extn, os_extn, maxch)
+    	      vfn_squeeze (root, outstr, maxch)
+ y/n = vfn_is_hidden_file (fname)
+
+The main vfn to osfn translation routine is VFN_TRANSLATE.  VFN_EXPAND_LDIR
+performs recursive logical directory expansion.  The encode and decode routines
+perform escape sequence encoding and its inverse.  Substitution of OS filename
+extensions for IRAF extensions, and vice versa, is performed by the map
+extension procedures.
+.endhelp ______________________________________________________________________
+
+# Size limiting definitions.
+
+define	MAX_PUSHBACK	16	# determines length of pushback stack
+define	SZ_PBBUF	255	# size of pushback buffer
+define	MAX_EXTENSIONS	20	# max filename extension pairs in EXTN_MAP
+define	MAX_RESERVEXTN	20	# max reserved filename extensions
+define	SZ_EXTNMAP	64	# storage for iraf/os extn pairs
+
+
+# VFN_TRANSLATE -- Translate a VFN into the OSDIR, ROOT, and EXTN fields.
+# If a logical directory prefix is given it will be recursively expanded.
+# Any number of subdirectories may be given; each is folded into the OSDIR.
+# The ROOT field is escape sequence encoded but not squeezed.  The EXTN
+# field is encoded and selected IRAF extensions are mapped into OS
+# extensions.
+
+procedure vfn_translate (rawvfn, osdir, lenosdir, root, lenroot, extn, lenextn)
+
+char	rawvfn[ARB]		# input virtual filename
+char	osdir[SZ_OSDIR]		# OS directory prefix		(output)
+int	lenosdir		# length of the osdir string	(output)
+char	root[SZ_VFNFN]		# OS root filename		(output)
+int	lenroot			# length of the root string	(output)
+char	extn[SZ_VFNFN]		# OS filename extension		(output)
+int	lenextn			# length of the extn string	(output)
+
+pointer	sp, ip, vfn, fname, sqroot
+int	gstrcpy(), nowhite()
+errchk	syserr
+
+begin
+	call smark (sp)
+	call salloc (vfn, SZ_PATHNAME, TY_CHAR)
+	call salloc (fname, SZ_PATHNAME, TY_CHAR)
+	call salloc (sqroot, MAX_ROOTLEN, TY_CHAR)
+
+	# Strip any whitespace at either end of the filename.
+	if (nowhite (rawvfn, Memc[vfn], SZ_PATHNAME) == 0)
+	    call syserr (SYS_FNOFNAME)
+
+	# If the VFN begins with a legal OS directory prefix it is assumed
+	# to be an OSFN and no mapping is performed.  Do not bother to break
+	# the filename into osdir, root, extn.
+
+	call zfxdir (Memc[vfn], osdir, SZ_OSDIR, lenosdir)
+
+	if (lenosdir > 0) {
+	    # VFN is actually an OSFN.  Return the OSFN as the osdir filename
+	    # to avoid the 32 char restriction.
+	    root[1] = EOS
+	    lenroot = 0
+	    extn[1] = EOS
+	    lenextn = 0
+
+	    lenosdir = gstrcpy (Memc[vfn], osdir, SZ_OSDIR)
+
+	    call sfree (sp)
+	    return
+	}
+
+	# The VFN is really a VFN.  Check for a logical directory prefix and
+	# recursively expand it into an OS directory prefix if found.  A VFN of
+	# the form "ldir$xxx" is converted to "osdir // xxx".  Additional
+	# subdirectories may be introduced in the expansion.
+
+	call vfn_expand_ldir (Memc[vfn], Memc[fname], SZ_PATHNAME)
+	call zfxdir (Memc[fname], osdir, SZ_OSDIR, lenosdir)
+	ip = fname + lenosdir
+
+	# Translate the VFN.  Each pass through the loop extracts and processes
+	# the next field of the VFN.  A field may be a subdirectory delimited
+	# by a /, a root filename, or an extension.  Subdirectory names are
+	# encoded and squeezed but not looked up in the mapping table, hence
+	# long directory names must be unique within a directory.
+
+	repeat {
+	    call vfn_encode (Memc, ip, root, lenroot, extn, lenextn)
+	    if (Memc[ip] == '/' ||
+		(root[1] == '.' && lenroot == 1) ||
+		(root[1] == '.' && root[2] == '.' && lenroot == 2)) {
+
+		if (lenroot > MAX_ROOTLEN) {
+		    call vfn_squeeze (root, Memc[sqroot], MAX_ROOTLEN)
+		    call zfsubd (osdir, SZ_OSDIR, Memc[sqroot], lenosdir)
+		} else
+		    call zfsubd (osdir, SZ_OSDIR, root, lenosdir)
+		root[1] = EOS
+		lenroot = 0
+		if (Memc[ip] == '/')
+		    ip = ip + 1
+	    }
+	} until (Memc[ip] == EOS)
+
+	# Map IRAF extension into OS extension.
+	if (lenextn > 0)
+	    call vfn_map_extension (extn, extn, SZ_VFNFN)
+	call sfree (sp)
+end
+
+
+# VFN_EXPAND_LDIR -- Copy the input VFN to the output string.  As the copy is
+# being performed we scan for the ldir delimiter.  If it is encountered, we
+# lookup the ldir in the environment and push the value back into the input,
+# resuming scanning on the new input.  Logical directories are thus expanded
+# recursively, i.e., one ldir may reference another in its definition.  If an
+# ldir references itself storage will overflow and an error message is printed.
+
+procedure vfn_expand_ldir (vfn, outstr, maxch)
+
+char	vfn[ARB]	# VFN possibly containing an ldir prefix
+char	outstr[maxch]	# output string
+int	maxch
+
+char	ch
+pointer	pbbuf					# pushback buffer
+pointer	pb_stack[MAX_PUSHBACK]			# pushback stack
+int	n, op, op_node, op_env, pbsp, in
+pointer	nextch, ip, sp
+
+int	envfind(), gstrcpy(), ki_localnode()
+define	input {$1=Memc[ip];ip=ip+1}
+define	output {outstr[op]=$1;op=op+1}
+errchk	syserrs, envfind
+
+begin
+	call smark (sp)
+	call salloc (pbbuf, SZ_PBBUF, TY_CHAR)
+
+	# Discard leading whitespace and copy the VFN into the input buffer.
+	for (in=1;  IS_WHITE (vfn[in]);  in=in+1)
+	    ;
+
+	nextch  = pbbuf + gstrcpy (vfn[in], Memc[pbbuf], SZ_PBBUF) + 1
+	ip      = pbbuf
+	op      = 1	
+	op_node = 1
+	pbsp    = 1
+
+	# Copy characters successively from the input buffer to the output
+	# buffer (outstr).  Expand logical names recursively (by rescanning
+	# the translation string returned by ENVGETS).
+
+	repeat {
+	    input (ch)
+	    if (IS_ALNUM (ch)) {			# --- regular chars
+		output (ch)
+
+	    } else if (ch == FNNODE_CHAR) {
+		# If CH is the node name delimiter, either the named node
+		# is the local node passed as a prefix to any ldir strings,
+		# or the node was referenced IN one of the logical directory
+		# replacement strings.
+
+		if (pbsp == 1) {
+		    # If no logical directory definitions have been pushed
+		    # back, the named node must be the local node.
+
+		    output (ch)
+		    op_node = op
+
+		} else {
+		    outstr[op] = EOS
+
+		    if (ki_localnode (outstr) == YES) {
+			# Same as above; ignore local node prefix.
+			output (ch)
+			op_node = op
+
+		    } else {
+			# A remote node has been referenced during logical
+			# directory expansion.  Filename translation must take
+			# place on the remote node, so exit immediately,
+			# returning the new filename "node!vfn".  This will
+			# repeat when filename translation resumes on the
+			# remote node, but over there the named node will be
+			# the local node and the if(yes) branch will be taken.
+
+			output (ch)
+			op = op + gstrcpy (vfn[in], outstr[op], maxch-op+1)
+			break
+		    }
+		}
+
+	    } else if (ch == FNLDIR_CHAR) {
+		# If CH is the logical name delimiter, look up the logical name
+		# in the environment table.  If found, push definition back into
+		# pbbuf, clear the output buffer, and scan pushed back string.
+		# If not found, pass the string on as a file name.  Delete the
+		# '$' character, so that OS directory specs like "osdir$"
+		# are passed on correctly.
+
+		output (EOS)
+		n = envfind (outstr[op_node], Memc[nextch],
+		    pbbuf + SZ_PBBUF - nextch)
+
+		if (n >= 0) {				# push back defn
+		    pb_stack[pbsp] = ip			# save ip on stk
+		    pbsp = pbsp + 1
+		    ip = nextch				# set ip to new input
+		    nextch = nextch + n + 1
+		    # Check for recursion (stack overflow).
+		    if (pbsp > MAX_PUSHBACK || nextch-pbbuf >= SZ_PBBUF)
+			call syserrs (SYS_FZMAPRECUR, Memc[pbbuf])
+		    op = op_node			# discard logical name
+		} else
+		    op = op - 1				# cancel EOS, delete $
+
+	    } else if (ch == '(') {
+		# Environment substitution.  Mark the position of the left
+		# paren for later replacement.
+
+		op_env = op
+		output (ch)
+
+	    } else if (ch == ')') {
+		# Complete an environment substitution.
+
+		outstr[op_env] = EOS
+		n = gstrcpy (outstr[op_node], Memc[nextch],
+		    pbbuf + SZ_PBBUF - nextch)
+
+		pb_stack[pbsp] = ip			# save ip on stk
+		pbsp = pbsp + 1
+		ip = nextch				# set ip to new input
+		nextch = nextch + n
+
+		# Check for recursion (stack overflow).
+		if (pbsp > MAX_PUSHBACK || nextch-pbbuf >= SZ_PBBUF)
+		    call syserrs (SYS_FZMAPRECUR, Memc[pbbuf])
+
+		# Get the envvar value string; use null string if not defined.
+		output (EOS)
+		n = envfind (outstr[op_env+1], Memc[nextch],
+		    pbbuf + SZ_PBBUF - nextch)
+		if (n <= 0) {
+		    Memc[nextch] = EOS
+		    n = 0
+		}
+
+		nextch = nextch + n + 1
+		op = op_node
+
+	    } else if (ch == EOS) {
+		# EOS may mean either the end of a pushed back string, or the
+		# end of the VFN string.  Pop old ip off stack, continue until
+		# the pushback stack is empty (end of VFN).
+
+		pbsp = pbsp - 1				# pop old ip off stk
+		ip = pb_stack[pbsp]
+		if (pbsp == 0)				# --- all done
+		    break
+
+	    } else if (ch == ESCAPE) {
+		# Escaped characters are passed straight to the output.
+		# Preserve the escape unless the escaped character is a
+		# metacharacter recognized by this procedure (i.e., $ or @).
+
+		input (ch)
+		if (ch == EOS)
+		    ip = ip - 1
+		else if (ch == FNLDIR_CHAR || ch == FNNODE_CHAR)
+		    output (ch)
+		else {
+		    output ('\\')
+		    output (ch)
+		}
+
+	    } else if (ch > BLANK) {
+		# Whitespace and control chars are deleted.
+		output (ch)
+	    }
+
+	    if (op > maxch)				# check for overflow
+		call syserrs (SYS_FZMAPOVFL, vfn)
+	}
+
+	output (EOS)
+	call sfree (sp)
+end
+
+
+# VFN_ENCODE -- Extract and encode the next field of the input VFN.  The subdir
+# delimiter / or EOS will delimit the scan; the input pointer must be set to
+# the first character to be scanned upon input and is left pointing at the
+# delimiter character upon output.  If the field is a subdir no extension will
+# be returned.  If an extension is encountered but its length exceeds that
+# permitted by the OS or if another "." delimited field is encountered then
+# the "." is encoded and the extension is included in the root.  If the OS is
+# case insensitive the output string will be all lower case.
+
+procedure vfn_encode (vfn, ip, root, lenroot, extn, lenextn)
+
+char	vfn[ARB]		# virtual filename to be scanned
+int	ip			# offset of first char to be scanned (in/out)
+char	root[SZ_VFNFN]		# receives the encoded root filename
+int	lenroot			# nchars in root
+char	extn[SZ_VFNFN]		# receives the encoded filename extn
+int	lenextn			# nchars in extn
+
+int	out, i
+char	ch, nextch
+bool	uc_mode, processing_extension, escape_extension, subdir
+pointer	sp, field, op
+
+int	gstrcpy()
+define	putch {Memc[op]=$1;op=op+1}
+define	notextn_ 91
+
+begin
+	call smark (sp)
+	call salloc (field, SZ_FNAME, TY_CHAR)
+
+	# Skip leading whitespace and control chars.
+	while (vfn[ip] > 0 && vfn[ip] <= BLANK)
+	    ip = ip + 1
+
+	# Do something sensible if the null string is input.
+	if (vfn[ip] == EOS) {
+	    root[1] = EOS
+	    extn[1] = EOS
+	    lenroot = 0
+	    lenextn = 0
+	    call sfree (sp)
+	    return
+	}
+
+	out = 1
+	op = field
+	uc_mode = false
+	processing_extension = false
+	escape_extension = false
+
+	# If the first char is legal in an OSFN but is not a letter and only
+	# letters are permitted as the first char, then a no-op sequence (shift
+	# to lower) is output first.  
+
+	if (LEADING_ALPHA_ONLY)
+	    if (vfn[ip] != '.' && !IS_ALPHA(vfn[ip]))
+		call vvfn_escape (SHIFT_TO_LOWER, root, out, SZ_VFNFN)
+
+	# The main loop.  Examine each input character and output zero or
+	# more characters depending on the input character class and on what
+	# the host system permits.  Most characters are expected to be lower
+	# case alphas or digits, hence what we do after these first couple of
+	# IF's should not affect efficiency much.  NOTE: set the escape char
+	# to NUL to turn off escapes on a machine that allows any char in a
+	# a filename.
+
+	ch = vfn[ip]
+	do i = 1, ARB {
+	    if (ch == EOS) {
+		break
+	    } else if (IS_LOWER(ch)) {
+		if (uc_mode) {
+		    putch (VFN_ESCAPE_CHAR)
+		    putch (SHIFT_TO_LOWER)
+		    uc_mode = false
+		}
+		putch (ch)
+
+	    } else if (IS_DIGIT(ch)) {
+		putch (ch)
+		
+	    } else if (ch == '_') {
+		if (UNDERSCORE_PERMITTED)
+		    putch (ch)
+		else {
+		    putch (VFN_ESCAPE_CHAR)
+		    putch (UNDERSCORE_CODE)
+		}
+
+	    } else if (IS_UPPER(ch)) {
+		if (!CASE_INSENSITIVE)
+		    putch (ch)
+		else if (uc_mode)
+		    putch (TO_LOWER(ch))
+		else {
+		    # Determine whether to do a case shift or just escape
+		    # a single character.  The crossover point is at 2 chars.
+		    # If the next character is also upper case we shift up.
+
+		    putch (VFN_ESCAPE_CHAR)
+		    if (IS_UPPER (vfn[ip+1])) {
+			uc_mode = true
+			putch (SHIFT_TO_UPPER)
+		    } else
+			putch (SHIFT_NEXTCHAR)
+		    putch (TO_LOWER(ch))
+		}
+
+	    } else if (ch == '.') {
+		# Determine whether the "." marks an extension or is part of
+		# one of the two special subdirectories "." and "..".
+
+		subdir = false
+		if (op == field && !processing_extension) {
+		    nextch = vfn[ip+1]
+		    if (nextch == '/' || nextch == EOS) {
+			subdir = true
+		    } else if (nextch == '.' &&
+		    	      (vfn[ip+2] == '/' || vfn[ip+2] == EOS)) {
+			subdir = true
+			putch (ch)
+			ip = ip + 1
+		    }
+		}
+		    
+		if (subdir) {
+		    putch (ch)
+
+		} else if (processing_extension) {
+		    # We are already processing an extension and have just
+		    # encountered another one (e.g., "file.x.old").  Escape
+		    # the dot and include it and the old extension in the
+		    # root.  Start a new extension.
+
+		    putch (EOS)
+		    if (PERIOD_PERMITTED) {
+			root[out] = '.'
+			out = out + 1
+		    } else
+			call vvfn_escape (PERIOD_CODE, root, out, SZ_VFNFN)
+		    out = out + gstrcpy (Memc[field], root[out], SZ_VFNFN-out+1)
+		    op = field
+		    escape_extension = false
+		
+		} else {
+		    # This is the first extension to be encountered.  Move the
+		    # contents of the field buffer to root and clear the buffer.
+
+		    putch (EOS)
+		    out = out + gstrcpy (Memc[field], root[out], SZ_VFNFN-out+1)
+		    op = field
+		    processing_extension = true
+		    escape_extension = false
+		}
+
+	    } else if (ch == '\\' && vfn[ip+1] != EOS) {
+		# Escaped characters are passed unconditionally, stripping the
+		# escape character itself unless used to escape the first char
+		# of an extension, in which case the \ must be retained in the
+		# output extension to defeat extension mapping.
+
+		if (processing_extension && op == field)
+		    escape_extension = true
+		ip = ip + 1
+		putch (vfn[ip])
+
+	    } else if (ch == '/') {
+		# End of subdirectory name terminates scan.  Extensions are
+		# not recognized within subdirectory names; include as part
+		# of root name.
+
+		if (processing_extension)
+		    goto notextn_
+		else
+		    break
+
+	    } else if (ch <= BLANK) {
+		# Strip whitespace and control chars.
+	    } else {
+		# Unknown characters are not mapped; user's discretion.
+		putch (ch)
+	    }
+
+	    # If we are processing an extension and the max length of an OS
+	    # extension has been exceeded, the extension is considered part of
+	    # the root and we are no longer processing an extension.
+
+	    if (processing_extension)
+		if (op - field > MAX_EXTNLEN) {
+notextn_	    if (PERIOD_PERMITTED) {
+			root[out] = '.'
+			out = out + 1
+		    } else
+			call vvfn_escape (PERIOD_CODE, root, out, SZ_VFNFN)
+		    processing_extension = false
+		    escape_extension = false
+		    if (ch == '/')
+			break
+		}
+
+	    ip = ip + 1
+	    ch = vfn[ip]
+	}
+
+	putch (EOS)
+	if (processing_extension) {
+	    # Move extension to the extn output buffer.  Add the escape
+	    # character if the extension was escaped.
+	    if (escape_extension) {
+		extn[1] = '\\'
+		lenextn = gstrcpy (Memc[field], extn[2], SZ_VFNFN-1) + 1
+	    } else
+		lenextn = gstrcpy (Memc[field], extn, SZ_VFNFN)
+
+	    # If extn is the null string then root ended in a period; include
+	    # the period in the root.
+	    if (lenextn == 0)
+		if (PERIOD_PERMITTED) {
+		    root[out] = '.'
+		    out = out + 1
+		} else
+		    call vvfn_escape (PERIOD_CODE, root, out, SZ_VFNFN)
+
+	    root[out] = EOS
+	    lenroot = out - 1
+
+	} else {
+	    extn[1] = EOS
+	    lenextn = 0
+	    lenroot = out + gstrcpy (Memc[field], root[out], SZ_VFNFN-out+1) - 1
+	}
+
+	call sfree (sp)
+end
+
+
+# VVFN_ESCAPE -- Deposit a character in the output buffer preceded by the
+# escape character.  Ensure that the output buffer does not overflow.
+
+procedure vvfn_escape (ch, outbuf, op, maxch)
+
+int	ch		# character to be output (passed as an INT)
+char	outbuf[maxch]	# output buffer
+int	op		# output pointer (in/out)
+int	maxch
+
+begin
+	outbuf[op] = VFN_ESCAPE_CHAR
+	op = min (maxch, op + 1)
+	outbuf[op] = ch
+	op = min (maxch, op + 1)
+end
+
+
+# VFN_DECODE -- Decode an escape sequence encoded field of a filename.  This is
+# easier than encoding because we have fewer decisions to make.
+#
+# NOTE: set the escape char to NUL on a machine which allows any character in a
+# filename.  Since such a character will never be encountered in filenames this
+# effectively turns off decoding and will prevent misinterpretation of OS
+# filenames not written by IRAF.
+
+int procedure vfn_decode (osfn, ip, outstr, maxch)
+
+char	osfn[ARB]	# escape sequence encoded filename
+int	ip		# input pointer (in/out)
+char	outstr[maxch]	# output string
+int	maxch
+
+int	ch, op
+bool	convert_to_upper
+define	putback_ 91
+
+begin
+	convert_to_upper = false
+
+	# Optimization: most filenames start with a simple sequence of letters.
+	# Dispense with these as a special case, and fall into the more general
+	# code when some other character is encountered.
+
+	do op = 1, maxch {
+	    ch = osfn[ip+op-1]
+	    if (ch != VFN_ESCAPE_CHAR && IS_LOWER (ch))
+		outstr[op] = ch
+	    else {
+		ip = ip + op - 1
+		break
+	    }
+	}
+
+	for (ch=osfn[ip];  ch != EOS && op <= maxch;  ch=osfn[ip]) {
+	    # Process escapes.
+
+	    if (ch == VFN_ESCAPE_CHAR && osfn[ip+1] != EOS) {
+		ip = ip + 1
+		ch = osfn[ip]
+
+		switch (ch) {
+		case SHIFT_NEXTCHAR:
+		    if (IS_LOWER (osfn[ip+1])) {
+			ip = ip + 1
+			outstr[op] = TO_UPPER (osfn[ip])
+			op = op + 1
+		    } else
+			goto putback_
+
+		case SHIFT_TO_LOWER, SHIFT_TO_UPPER:
+		    if (IS_LOWER (osfn[ip+1]))
+			convert_to_upper = (ch == SHIFT_TO_UPPER)
+		    else
+			goto putback_
+
+		case UNDERSCORE_CODE:
+		    outstr[op] = '_'
+		    op = op + 1
+
+		case PERIOD_CODE:
+		    outstr[op] = '.'
+		    op = op + 1
+
+		default:
+		    # Not a recognized escape.  Output the escape char
+		    # and put the next char back into the input.
+putback_
+		    outstr[op] = VFN_ESCAPE_CHAR
+		    op = op + 1
+		    ip = ip - 1
+		}
+	    
+	    } else if (IS_LOWER (ch)) {
+		if (convert_to_upper)
+		    outstr[op] = TO_UPPER(ch)
+		else
+		    outstr[op] = ch
+		op = op + 1
+
+	    } else if (ch == EXTN_DELIMITER) {
+		break
+
+	    } else if (ch == FNLDIR_CHAR) {
+		outstr[op] = '\\'
+		op = op + 1
+		outstr[op] = ch
+		op = op + 1
+
+	    } else {
+		outstr[op] = ch
+		op = op + 1
+	    }
+
+	    ip = ip + 1
+	}
+
+	outstr[op] = EOS
+	return (op - 1)
+end
+
+
+# VFN_MAP_EXTENSION -- Map an IRAF filename extension to a host OS filename
+# extension.  Unrecognized extensions are merely copied.  The set of
+# extensions to be mapped is defined in <config.h>
+
+procedure vfn_map_extension (iraf_extn, os_extn, maxch)
+
+char	iraf_extn[ARB]		# IRAF filename extension
+char	os_extn[maxch]		# OS filename extension
+int	maxch
+
+bool	first_time
+char	first_char
+int	extn
+bool	streq()
+data	first_time /true/
+
+int	nextn			# number of extensions in map
+short	iraf[MAX_EXTENSIONS]	# indices of IRAF extensions
+short	os[MAX_EXTENSIONS]	# indices of OS extensions
+char	map[SZ_EXTNMAP]		# iraf to os mappings, e.g. "|iraf,os|.."
+common	/vfnxtn/ nextn, iraf, os, map
+
+begin
+	# Init the iraf and os index arrays and count the number of extension
+	# in the map.
+
+	if (first_time) {
+	    call vvfn_init_extnmap (map, iraf, os, nextn, MAX_EXTENSIONS)
+	    first_time = false
+	}
+
+	first_char = iraf_extn[1]
+
+	# Escaped extensions, i.e., "root.\extn", are passed on unmodified but
+	# with the escape character deleted.
+
+	if (first_char == '\\') {
+	    call strcpy (iraf_extn[2], os_extn, maxch)
+	    return
+	}
+	    
+	# Search map for the IRAF extension and of found return OS extension,
+	# else return IRAF extension.
+
+	if (first_char != EOS)
+	    for (extn=1;  extn <= nextn;  extn=extn+1)
+		if (map[iraf[extn]] == first_char)
+		    if (streq (iraf_extn, map[iraf[extn]])) {
+			call strcpy (map[os[extn]], os_extn, maxch)
+			return
+		    }
+
+	call strcpy (iraf_extn, os_extn, maxch)
+end
+
+
+# VFN_UNMAP_EXTENSION -- Convert OS extension to IRAF extension by table lookup
+# in the MAP array of extn pairs.
+
+procedure vfn_unmap_extension (os_extn, iraf_extn, maxch)
+
+char	os_extn[maxch]		# OS filename extension
+char	iraf_extn[ARB]		# IRAF filename extension
+int	maxch
+
+int	extn
+char	first_char
+bool	first_time
+bool	streq()
+data	first_time /true/
+
+int	nextn			# number of extensions in map
+short	iraf[MAX_EXTENSIONS]	# indices of IRAF extensions
+short	os[MAX_EXTENSIONS]	# indices of OS extensions
+char	map[SZ_EXTNMAP]		# iraf to os mappings, e.g. "|iraf,os|.."
+common	/vfnxtn/ nextn, iraf, os, map
+
+begin
+	# Init the iraf and os index arrays and count the number of extension
+	# in the map.
+
+	if (first_time) {
+	    call vvfn_init_extnmap (map, iraf, os, nextn, MAX_EXTENSIONS)
+	    first_time = false
+	}
+
+	# Search map for the OS extension and if found return IRAF extension.
+	# If the OS extension matches an IRAF extension then escape the first
+	# char of the extension to avoid interpretation as an IRAF extension.
+
+	first_char = os_extn[1]
+	if (first_char != EOS)
+	    for (extn=1;  extn <= nextn;  extn=extn+1) {
+		if (map[os[extn]] == first_char) {
+		    if (streq (os_extn, map[os[extn]])) {
+			call strcpy (map[iraf[extn]], iraf_extn, maxch)
+			return
+		    }
+		}
+		if (map[iraf[extn]] == first_char) {
+		    if (streq (os_extn, map[iraf[extn]])) {
+			iraf_extn[1] = '\\'
+			call strcpy (map[iraf[extn]], iraf_extn[2], maxch-1)
+			return
+		    }
+		}
+	    }
+
+	call strcpy (os_extn, iraf_extn, maxch)
+end
+
+
+# VVFN_INIT_EXTNMAP -- Scan the map and initialize the indices of the
+# extension strings the first time we are called.  Replace the field
+# delimiters with EOS to ease string comparisons.  The format of the map
+# string is "Airaf,osA...", where A is any field delimiter character and
+# a comma must be given between fields.  Embedded whitespace is not
+# permitted.  For example:  map = "|a,olb|e,exe|"
+
+procedure vvfn_init_extnmap (map, iraf, os, nextn, max_extn)
+
+char	map[ARB]		# set of extns to be mapped
+short	iraf[max_extn]		# indices of IRAF extensions
+short	os[max_extn]		# indices of OS extensions
+int	nextn			# number of extensions in map
+int	max_extn
+
+int	ip
+char	delim
+bool	first_time
+data	first_time /true/
+
+begin
+	if (!first_time)
+	    return
+
+	call strcpy (EXTN_MAP, map, SZ_EXTNMAP)
+	nextn = 0
+	delim = map[1]
+	if (delim == EOS)
+	    return
+
+	for (ip=2;  map[ip] != EOS && nextn < max_extn;  ip=ip+1) {
+	    nextn = nextn + 1
+
+	    iraf[nextn] = ip
+	    while (map[ip] != ',' && map[ip] != EOS)
+		ip = ip + 1
+	    map[ip] = EOS
+	    ip = ip + 1
+
+	    os[nextn] = ip
+	    while (map[ip] != delim && map[ip] != EOS)
+		ip = ip + 1
+	    map[ip] = EOS
+	}
+
+	if (nextn > max_extn)
+	    call fatal (1, "fio$vfntrans.x: too many extensions")
+
+	first_time = false
+end
+
+
+# VFN_SQUEEZE -- Squeeze the root filename (or any string) to fit into the
+# output string.  Squeezing preserves the first N-1 and final characters of
+# the input string, e.g., if N=6 "concatenate" is squeezed to "concae".
+
+procedure vfn_squeeze (root, outstr, maxch)
+
+char	root[ARB]		# input string to be squeezed
+char	outstr[maxch]		# output, squeezed string
+int	maxch			# length of squeezed string
+
+int	ip, op
+
+begin
+	# Omit leading whitespace.
+	for (ip=1;  IS_WHITE (root[ip]);  ip=ip+1)
+	    ;
+
+	# Squeeze root to outstr.
+	for (op=0;  root[ip] != EOS;  ip=ip+1) {
+	    op = min (maxch, op + 1)
+	    outstr[op] = root[ip]
+	}
+	outstr[op+1] = EOS
+end
+
+
+# VFN_IS_HIDDEN_FILE -- Determine if the named file is a hidden file.
+# Hidden files are files with reserved extensions.  The set of reserved
+# extensions is given by a list of the form "|.ex1|.ext|...|".
+
+int procedure vfn_is_hidden_file (fname)
+
+char	fname[ARB]		# unpacked filename
+char	ch
+short	extn[MAX_RESERVEXTN]
+bool	first_time
+int	nextn, first_char, off, i
+bool	streq()
+int	strldx()
+string	reserved RESERVED_EXTNS
+data	first_time /true/
+
+begin
+	if (first_time) {
+	    call vvfn_init_reserved_extns (reserved, extn,MAX_RESERVEXTN, nextn)
+	    first_time = false
+	}
+
+	if (nextn > 0) {
+	    ch = EXTN_DELIMITER
+	    off = strldx (ch, fname) + 1
+	    first_char = fname[off]
+
+	    if (off > 0 && first_char != EOS)
+		do i = 1, nextn
+		    if (reserved[extn[i]] == first_char)
+			if (streq (reserved[extn[i]], fname[off]))
+			    return (YES)
+	}
+	
+	return (NO)
+end
+
+
+# VVFN_INIT_RESERVED_EXTNS -- Inde the list of reserved extensions.  Overwrite
+# the delimiter character with EOS, set the indices of the extension strings
+# in the EXTN array, and count the number of extensions.  The format of the
+# reserved extension array is "|str1|str2|str3|...|strN|", where the first
+# char is taken to be the delimiter character.
+
+procedure vvfn_init_reserved_extns (ex, extn, max_extn, nextn)
+
+char	ex[ARB]			# list of reserved extensions
+short	extn[max_extn]		# indices of substrings
+int	max_extn		# max extensions
+int	nextn			# number of extensions (output)
+
+char	delim
+int	ip
+
+begin
+	nextn = 0
+	delim = ex[1]
+	if (delim == EOS)
+	    return
+	ip = 2
+
+	while (ex[ip] != EOS && nextn < max_extn) {
+	    nextn = nextn + 1
+	    extn[nextn] = ip
+
+	    while (ex[ip] != delim && ex[ip] != EOS)
+		ip = ip + 1
+
+	    if (ex[ip] == delim) {
+		ex[ip] = EOS
+		ip = ip + 1
+	    }
+	}
+end