--- a/PosStream.st	Mon Nov 08 03:29:58 1993 +0100
+++ b/PosStream.st	Mon Nov 08 03:32:43 1993 +0100
@@ -11,8 +11,8 @@
 "
 
 Stream subclass:#PositionableStream
-       instanceVariableNames:'collection position readLimit continueBlock abortBlock'
-       classVariableNames:''
+       instanceVariableNames:'collection position readLimit'
+       classVariableNames:'ErrorDuringFileInSignal'
        poolDictionaries:''
        category:'Streams'
 !
@@ -22,16 +22,22 @@
 COPYRIGHT (c) 1989 by Claus Gittinger
               All Rights Reserved
 
-Instances of myself allow positioning the read pointer.
-I also add methods for source-chunk reading and writing
+Instances of PositionableStream allow positioning the read pointer.
+PositionableStream also adds methods for source-chunk reading and writing
 and for filing-in/out of source code.
+This is an abstract class.
+
+$Header: /cvs/stx/stx/libbasic/Attic/PosStream.st,v 1.5 1993-11-08 02:31:29 claus Exp $
+'!
 
-$Header: /cvs/stx/stx/libbasic/Attic/PosStream.st,v 1.4 1993-10-13 02:13:11 claus Exp $
+!PositionableStream class methodsFor:'initialization'!
 
-TODO
-   change to use signals for error handling during fileIn
-   (get rid of continue/abort blocks)
-'!
+initialize
+    ErrorDuringFileInSignal isNil ifTrue:[
+        ErrorDuringFileInSignal := (Signal new) mayProceed:true.
+        ErrorDuringFileInSignal notifierString:'error during fileIn'.
+    ]
+! !
 
 !PositionableStream class methodsFor:'constants'!
 
@@ -91,17 +97,18 @@
     |peekObject|
 
     peekObject := self next.
-    self position:(self position - 1).
+    self backStep.
     ^ peekObject
 !
 
 peekFor:something
-    "return true and move past if next == something"
+    "return true and move past if next == something; 
+     otherwise stay and let position unchanged"
 
     self next == something ifTrue:[
         ^ true
     ].
-    self position:(self position - 1).
+    self backStep.
     ^ false
 !
 
@@ -135,7 +142,11 @@
     "return a collection of the elements up-to the end
      Return nil if the stream-end is reached before."
 
-    |newColl e|
+    |newColl|
+
+    "this implementation has stupid (o-square) runtime behavior -
+     should I add a query for resizability if collections and use
+     add: instead ?"
 
     newColl := collection species new.
     [self atEnd] whileFalse:[
@@ -189,10 +200,17 @@
 position:index
     "set the read position"
 
-    (index > (readLimit + 1)) ifTrue: [^ self positionError].
+    ((index > (readLimit + 1)) or:[position < 1]) ifTrue: [^ self positionError].
     position := index
 !
 
+backStep
+    "move backward read position by one"
+
+    position <= 1 ifTrue: [^ self positionError].
+    position := position - 1
+!
+    
 reset
     "set the read position to the beginning of the collection"
 
@@ -418,13 +436,37 @@
     |lastValue|
 
     self position:1.
-    abortBlock := [^ nil].
-    continueBlock := [].
     Smalltalk at:#ErrorHandler put:self.
-    [self atEnd] whileFalse:[
-        lastValue := self fileInNextChunkNotifying:someone
-    ].
-    Smalltalk at:#ErrorHandler put:nil.
+    [
+        ErrorDuringFileInSignal handle:[:ex |
+	    |action|
+
+	    "handle the case where no GUI has been built in,
+	     just abort with a notification"
+
+	    Display isNil ifTrue:[
+		self notify:(ex parameter).
+		ex return
+	    ].
+
+	    "otherwise ask what should be done now and either
+	     continue or abort the fileIn"
+
+	    action := self askForDebug:(ex parameter).
+	    action == #continue ifTrue:[
+                Smalltalk at:#ErrorHandler put:self.
+		ex proceed
+	    ].
+	    action == #abort ifTrue:[
+		ex return
+	    ].
+            ex reject
+        ] do:[
+            [self atEnd] whileFalse:[
+                lastValue := self fileInNextChunkNotifying:someone
+            ].
+        ].
+    ] valueNowOrOnUnwindDo:[Smalltalk at:#ErrorHandler put:nil].
     ^ lastValue
 !
 
@@ -452,9 +494,11 @@
      we dont want a debugger to come up but simply notify
      the error (also on the Transcript so you have a trace of it)"
 
-    |message action|
+    |message|
 
+    "switch back to regular error handling"
     Smalltalk at:#ErrorHandler put:nil.
+
     (aSymbol == #doesNotUnderstand:) ifTrue:[
         anObject isNil ifTrue:[
             "try to give a bit more detail on what went wrong"
@@ -480,20 +524,7 @@
     ].
     message := 'Error: ' , message.
     Transcript showCr:message.
-
-    YesNoBox notNil ifTrue:[
-        action := self askForDebug:message.
-        action == #debug ifTrue:[
-            Debugger enterWithMessage:message
-        ].
-        action == #continue ifTrue:[
-            continueBlock value
-        ].
-    ] ifFalse:[
-        self notify:message
-    ].
-
-    abortBlock value.
+    ErrorDuringFileInSignal raiseRequestWith:message.
     ^ nil
 !