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([Encoder -_encodeObject:withName:isBycopy:isForwardReference:]): See

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if object satisfies a forward reference *after* encoding it.  This is
necessary because the encoding of subobjects may generate forward
references.  (In a sense, this undoes the last change, but it is
significantly different in that we test whether the object is in the
object_2_fref table *after* encoding the object; before we looked in
the table before encoding the object.)  As a consequence,
the CODER_OBJECT_FORWARD_SATISFIER tag is no longer necessary; this
was used to tag an object before it was encoded, but now we understand
that we cannot know whether this object satisfies a forward reference
until after it has been encoded.  Thus, for all objects we encode an
unsigned int after encoding the object itself.  This unsigned int is
either the forward reference number of zero, depending on whether this
object satisfies any forward references.


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@1358 72102866-910b-0410-8b05-ffd578937521
This commit is contained in:
Andrew McCallum 1996-04-13 19:27:23 +00:00
parent 919f4e6955
commit 5b21ec95f4
1 changed files with 35 additions and 25 deletions
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60
Source/Encoder.m
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@ -645,38 +645,48 @@ my_object_is_class(id object)
NSIntMapValueCallBacks, 0);
NSMapInsert (in_progress_table, anObj, (void*)1);
/* Find out if this object satisfies any previous forward
references. */
fref = [self _coderForwardReferenceForObject: anObj];
if (fref)
{
/* It does satisfy a forward reference; write the forward
reference number, so the decoder can know. */
[self encodeTag: CODER_OBJECT_FORWARD_SATISFIER];
[self encodeValueOfCType: @encode(unsigned)
at: &fref
withName: @"Object forward cross-reference number"];
/* xxx This code used to be below at the place marked `1234' */
/* Remove it from the forward reference table, since we'll never
have another forward reference for this object. */
[self _coderRemoveForwardReferenceForObject: anObj];
}
else
{
/* It does not satisfy a forward reference. Note: in future
encoding we may have backward references to this object,
but we will never need forward references to this object. */
[self encodeTag: CODER_OBJECT];
}
/* Encode the object. */
[self encodeTag: CODER_OBJECT];
[self encodeIndent];
if (bycopy_flag)
[self _doEncodeBycopyObject:anObj];
else
[self _doEncodeObject:anObj];
[self encodeUnindent];
/* The code above marked `1234' used to be here. */
/* Find out if this object satisfies any forward references,
and encode either the forward reference number, or a
zero. NOTE: This test is here, and not before the
_doEncode.., because the encoding of this object may,
itself, generate a "forward reference" to this object,
(ala the in_progress_table). That is, we cannot know
whether this object satisfies a forward reference until
after it has been encoded. */
fref = [self _coderForwardReferenceForObject: anObj];
if (fref)
{
/* It does satisfy a forward reference; write the forward
reference number, so the decoder can know. */
[self encodeValueOfCType: @encode(unsigned)
at: &fref
withName: @"Object forward cross-reference number"];
/* Remove it from the forward reference table, since we'll never
have another forward reference for this object. */
[self _coderRemoveForwardReferenceForObject: anObj];
}
else
{
/* It does not satisfy any forward references. Let the
decoder know this by encoding NULL. Note: in future
encoding we may have backward references to this
object, but we will never need forward references to
this object. */
unsigned null_fref = 0;
[self encodeValueOfCType: @encode(unsigned)
at: &null_fref
withName: @"Object forward cross-reference number"];
}
/* Register that we have encoded it so that future encoding can
do backward references properly. */
[self _coderInternalCreateReferenceForObject: anObj];