Patch: preferences fixes

[Tom Tromey <tromey at cygnus dot com>]

This patch fixes a couple of Insight PRs which I submitted.

First, it makes the encoding of .gdbtkinit smarter.  It now uses URL
encoding instead of the previous ad-hoc encoding.  The new encoding
has the nice property of being round-trip capable -- no matter what
you feed into it, the result you get back from decoding should be the
same.  The old encoding failed with certain (unlikely, admittedly)
strings.

Second, this patch adds versioning to .gdbtkinit.  A version string is
written to the file and recognized when the file is read back in.
This lets us change the encoding or the file format in the future and
still be able to read existing .gdbtkinit files.

Third, this patch allows keys with more `/'s than the old code
allowed.

The new code can read old .gdbtkinit files correctly.

This patch does include a minor change in preparation for my session
patch (it adds the `session' key).  This doesn't hurt but I can remove
it before committing if you really want.

Ok to commit?

2000-11-30  Tom Tromey  <tromey@cygnus.com>

	* prefs.tcl (pref_save): Put version number into file.  Added
	`session' to list of top-level keys.  Allow keys with many `/'s.
	(pref_read): Recognize version number.
	(escape_value): Generate URL-style encoding.
	(unescape_value): Added `version' argument.  Handle URL decoding.

Tom

Index: prefs.tcl
===================================================================
RCS file: /cvs/src/src/gdb/gdbtk/library/prefs.tcl,v
retrieving revision 1.3
diff -u -r1.3 prefs.tcl
--- prefs.tcl	2000/04/04 00:17:47	1.3
+++ prefs.tcl	2000/11/30 19:05:28
@@ -72,10 +72,15 @@
 
     if {$file_opened == "1"} {
       set section gdb
+      set version 0
       while {[gets $fd line] >= 0} {
 	switch -regexp -- $line {
 	  {^[ \t\n]*#.*} {
-	    ;# comment; ignore it
+	    # Comment.  We recognize one magic comment that includes
+	    # the version number.
+	    if {[regexp -- "^GDBtkInitVersion: (\[0-9\]+)\$" $line v]} {
+	      set version $v
+	    }
 	  }
 
 	  {^[ \t\n]*$} {
@@ -94,7 +99,7 @@
 	  default {
 	    regexp "\[ \t\n\]*\(.+\)=\(.+\)" $line a name val
 	    # Must unescape equal signs in val
-	    set val [unescape_value $val]
+	    set val [unescape_value $val $version]
 	    if {$section == "gdb"} {
 	      pref setd gdb/$name $val
 	    } elseif {$section == "global" && [regexp "^font/" $name]} {
@@ -141,6 +146,7 @@
     }
   
     puts $fd "\# GDBtk Init file"
+    puts $fd "\# GDBtkInitVersion: 1"
 
     set plist [pref list]
     # write out global options
@@ -170,16 +176,18 @@
       }
     }
 
-    #now loop through all sections writing out values
+    # now loop through all sections writing out values
+    # FIXME: this is broken.  We should discover the list
+    # dynamically.
     lappend secs load console src reg stack locals watch bp search \
-      process geometry help browser kod window
+      process geometry help browser kod window session
 
     foreach section $secs {
       puts $fd "\[$section\]"
       foreach var $plist {
 	set t [split $var /]
 	if {[lindex $t 0] == "gdb" && [lindex $t 1] == $section} {
-	set x [lindex $t 2]
+	  set x [join [lrange $t 2 end] /]
 	  set v [escape_value [pref get $var]]
 	  if {$x != "" && $v != ""} {
 	    puts $fd "\t$x=$v"
@@ -200,22 +208,40 @@
 #         prefs to a file
 # -------------------------------------------------------
 proc escape_value {val} {
-
-  if {[regsub -all -- = $val {!%} newval]} {
-    return $newval
-  }
-
-  return $val
+  # We use a URL-style quoting.  We encode `=', `%', the `[]'
+  # characters and newlines.  We use a cute trick here: we regsub in
+  # command expressions which we then expand using subst.
+  regsub -all -- "(\[\]\[=%\n\])" $val \
+    {[format "%%%02x" [scan {\1} %c x; set x]]} newval
+  return [subst -nobackslashes -novariables $newval]
 }
 
 # -------------------------------------------------------
 #  PROC: unescape_value - unescape all equal signs for
-#         reading prefs from a file
+#         reading prefs from a file.  VERSION is the version
+#         number of the encoding.
+#  version 0 only encoded `='.
+#  version 1 correctly encoded more values
 # -------------------------------------------------------
-proc unescape_value {val} {
+proc unescape_value {val version} {
+  switch -exact -- $version {
+    0 {
+      # Old-style encoding.
+      if {[regsub -all -- {!%} $val = newval]} {
+	return $newval
+      }
+    }
+
+    1 {
+      # Version 1 uses URL encoding.
+      regsub -all -- "%(..)" $val \
+	{[format %c 0x\1]} newval
+      return [subst -nobackslashes -novariables $newval]
+    }
 
-  if {[regsub -all -- {!%} $val = newval]} {
-    return $newval
+    default {
+      error "Unknown encoding version $version"
+    }
   }
 
   return $val