1.
2.
3.
4.
5.
6.
7.
BuilderVisitor
XMLMetadataVisitor
ProcessMetadataVisitor
FolderRenameVisitor
ComparerVisitor
SyncerVisitor
XMLWriterVisitor
1.
BuilderVisitor

2.
ComparerVisitor

3.
Builds the merged tree.
Compares and updates the state of each node.
SyncerVisitor

Takes the updated state of each node and
performs an action to keep them synchronized.
BuilderVisitor
Nothing else to build, so we
Since traverse
Now,
“A” is thethe
firstcontents
folder toofbe
Build FolderCompareObject
return
all the way back to
Traverse
build,
“School
Finally,
allwe
Work”
the
and
build
build
and
“Results.txt”
or
build
populate
new
with name “School Work”,
RootCompareObject.
Now, we
tree populate
FileCompareObjects
objects.
and
for In thisthe
case,
information
build
or
at
and populate
build
“CueSheet.docx”
information
and at
“C:\Users\Wysie\Desktop\A”
FolderCompareObjects
“Final.pdf”
index
0. and “Proposal.docx”
will be
index 0. information at index
populate
created.
and
populate index 0.
0.
RootCompareObject
string[] paths
paths[0] = “C:\Users\Wysie\Desktop\A”
paths[1] = “C:\Users\Wysie\Desktop\B”
paths[2] = “C:\Users\Wysie\Desktop\C”
Index 0: C:\Users\Wysie\Desktop\A
Index 1: C:\Users\Wysie\Desktop\B
Index 2: C:\Users\Wysie\Desktop\C
FolderCompareObject
FileCompareObject
FileCompareObject
name = “School Work”
name = “CueSheet.docx”
name = “Results.txt”
numOfPaths = 3
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
string[] hash;
hash[0] = “QWERTY”;
hash[1] = null;
hash[2] = null;
string[] hash;
hash[0] = “AAAAA”;
hash[1] = null;
hash[2] = null;
long[] lastModified;
long[0] = 99999;
long[1] = 0;
long[2] = 0;
long[] lastModified;
long[0] = 70000;
long[1] = 0;
long[2] = 0;
FileCompareObject
FileCompareObject
name = “Final.pdf”
name = “Proposal.docx”
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
string[] hash;
hash[0] = “ZXCVB”;
hash[1] = null;
hash[2] = null;
string[] hash;
hash[0] = “ASDFG”;
hash[1] = null;
hash[2] = null;
long[] lastModified;
long[0] = 30000;
long[1] = 0;
long[2] = 0;
long[] lastModified;
long[0] = 10000;
long[1] = 0;
long[2] = 0;
“CueSheet.docx” is found in
Traverse
Since
“Results.txt”
“School
andisbuild
Work”
alsoor
found
does
populate
not
in
“B”. We now populate index 1 of
treeWe
exist
“B”.
for
in “B”,
nowthe
populate
entire index
portion
1 of
“CueSheet.docx” with
“C:\Users\Wysie\Desktop\B”
remains
“Results.txt”
unchanged.
with information.
information.
RootCompareObject
string[] paths
paths[0] = “C:\Users\Wysie\Desktop\A”
paths[1] = “C:\Users\Wysie\Desktop\B”
paths[2] = “C:\Users\Wysie\Desktop\C”
Index 0: C:\Users\Wysie\Desktop\A
Index 1: C:\Users\Wysie\Desktop\B
Index 2: C:\Users\Wysie\Desktop\C
FolderCompareObject
FileCompareObject
FileCompareObject
FileCompareObject
name = “School Work”
name
name==“CueSheet.docx”
“CueSheet.docx”
name = “Results.txt”
numOfPaths = 3
numOfPaths
numOfPaths==33
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
bool[]
bool[]exists;
exists;
exists[0]
exists[0]==true
true
exists[1]
exists[1]==false
true
exists[2]
exists[2]==false
false
bool[] exists;
exists[0] = true
exists[1] = true
false
exists[2] = false
string[]
string[]hash;
hash;
hash[0]
hash[0]==“QWERTY”;
“QWERTY”;
hash[1]
hash[1]==null;
“MNBVC”;
hash[2]
hash[2]==null;
null;
string[] hash;
hash[0] = “AAAAA”;
hash[1] = “VVBBB”;
null;
hash[2] = null;
long[]
long[]lastModified;
lastModified;
long[0]
long[0]==99999;
99999;
long[1]
long[1]==0;
88888;
long[2]
long[2]==0;
0;
long[] lastModified;
long[0] = 70000;
long[1] = 90000;
0;
long[2] = 0;
FileCompareObject
FileCompareObject
name = “Final.pdf”
name = “Proposal.docx”
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
string[] hash;
hash[0] = “ZXCVB”;
hash[1] = null;
hash[2] = null;
string[] hash;
hash[0] = “ASDFG”;
hash[1] = null;
hash[2] = null;
long[] lastModified;
long[0] = 30000;
long[1] = 0;
long[2] = 0;
long[] lastModified;
long[0] = 10000;
long[1] = 0;
long[2] = 0;
RootCompareObject
“Final.pdf”
Traverse
and
does
build
notor
exist.
populate
“School Work” exists in “C”.
tree for “Proposal.docx”
However,
Populate index 2 in “C”.
“C:\Users\Wysie\Desktop\C”
exists.
Populate at index 2.
string[] paths
paths[0] = “C:\Users\Wysie\Desktop\A”
paths[1] = “C:\Users\Wysie\Desktop\B”
paths[2] = “C:\Users\Wysie\Desktop\C”
Index 0: C:\Users\Wysie\Desktop\A
Index 1: C:\Users\Wysie\Desktop\B
Index 2: C:\Users\Wysie\Desktop\C
FolderCompareObject
FileCompareObject
FileCompareObject
name = “School Work”
name = “CueSheet.docx”
name = “Results.txt”
numOfPaths = 3
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = true
false
bool[] exists;
exists[0] = true
exists[1] = true
exists[2] = false
bool[] exists;
exists[0] = true
exists[1] = true
exists[2] = false
string[] hash;
hash[0] = “QWERTY”;
hash[1] = “MNBVC”;
hash[2] = null;
string[] hash;
hash[0] = “AAAAA”;
hash[1] = “VVBBB”;
hash[2] = null;
long[] lastModified;
long[0] = 99999;
long[1] = 88888;
long[2] = 0;
long[] lastModified;
long[0] = 70000;
long[1] = 90000;
long[2] = 0;
FileCompareObject
FileCompareObject
name = “Final.pdf”
name = “Proposal.docx”
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = false
exists[2] = false
bool[] exists;
exists[0] = true
exists[1] = false
false
exists[2] = true
string[] hash;
hash[0] = “ZXCVB”;
hash[1] = null;
hash[2] = null;
string[] hash;
hash[0] = “ASDFG”;
hash[1] = null;
null;
hash[2] = “DFGHJK”;
long[] lastModified;
long[0] = 30000;
long[1] = 0;
long[2] = 0;
long[] lastModified;
long[0] = 10000;
long[1] = 0;
long[2] = 10000;
0;

There are many other attributes that are left
out, such as priority, new name, creation
time, among many others. For a more
detailed explanation, please take a look at
the source code comments.
ComparerVisitor
Finally,
Now,
For
It
Based
will
“Proposal.docx”,
it
first
now
on
“Results.txt”
will
the
visit
visit
traverse
last
“School
modified
the
isitvisited.
Work”.
exists in
Since
contents
0
“CueSheet.docx”.
date,
Again,
and the
it
2,itexists
but
exists
of
one
“School
not
at
ininin
index
index
Since
1.Work”.
Comparing
00is
and
itand
exists
more
For
1.
ComparerVisitor will now visit
index
“Final.pdf”,
the
in
updated
This
index
hash
time
2, 0but
then
of
round,
and
index
since
not
the
1 but
inthe
it
0one
index
and
only
not
one
at2
inexists
1,
index
at
shows
2,
the
the tree.
algorithm
in
that
comparison
1.
index
Thus,
index
they
1 issource
0,found
are
will
source
will
identical.
set
position
to
beposition
source
be
done
more
Thus,
willwill
be
position
again
source
between
set
updated.
to be
0.position
to
set
0Source
and
0.to 0.
1.
will
position
be setisto1.0.
RootCompareObject
string[] paths
paths[0] = “C:\Users\Wysie\Desktop\A”
paths[1] = “C:\Users\Wysie\Desktop\B”
paths[2] = “C:\Users\Wysie\Desktop\C”
Index 0: C:\Users\Wysie\Desktop\A
Index 1: C:\Users\Wysie\Desktop\B
Index 2: C:\Users\Wysie\Desktop\C
FolderCompareObject
FolderCompareObject
FileCompareObject
FileCompareObject
name
Work”
name==“School
“School
Work”
name = “CueSheet.docx”
name = “Results.txt”
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = true
exists[2] = false
bool[] exists;
exists[0] = true
exists[1] = true
exists[2] = false
string[] hash;
hash[0] = “QWERTY”;
hash[1] = “MNBVC”;
hash[2] = null;
string[] hash;
hash[0] = “AAAAA”;
hash[1] = “VVBBB”;
hash[2] = null;
long[] lastModified;
long[0] = 99999;
long[1] = 88888;
long[2] = 0;
long[] lastModified;
long[0] = 70000;
long[1] = 90000;
long[2] = 0;
srcPosition = 0
srcPosition = 1
numOfPaths = 3
numOfPaths = 3
bool[] exists;
bool[]
exists[0]exists;
= true
exists[0]
= true
exists[1] = false
exists[2] = =
true
exists[1]
false
exists[2]
srcPosition==true
0
FileCompareObject
FileCompareObject
FileCompareObject
FileCompareObject
name
name==“Final.pdf”
“Final.pdf”
name
name==“Proposal.docx”
“Proposal.docx”
numOfPaths
numOfPaths==3 3
numOfPaths
numOfPaths==3 3
bool[]
bool[]exists;
exists;
exists[0]
exists[0]==true
true
exists[1] = false
exists[1] = false
exists[2] = false
bool[]
bool[]exists;
exists;
exists[0] = true
exists[0] = true
exists[1] = false
exists[1] = false
exists[2] = true
string[] hash;
string[]
hash[0] =hash;
“ZXCVB”;
hash[0]
“ZXCVB”;
hash[1] ==null;
hash[1]
null;
hash[2] ==null;
string[] hash;
string[]
hash[0] =hash;
“ASDFG”;
hash[0]
“ASDFG”;
hash[1] ==null;
hash[1]
null;
hash[2] ==“ASDFG”;
hash[2] = null;
hash[2] = “DFGHJK”;
long[2]
= 0;= 0
srcPosition
long[2] = 10000;
srcPosition
=0
exists[2] = false
long[] lastModified;
long[0]lastModified;
= 30000;
long[]
long[1] ==0;30000;
long[0]
long[2]
long[1]==0;0;
exists[2] = true
long[] lastModified;
long[0]lastModified;
= 10000;
long[]
long[1] ==0;10000;
long[0]
long[2]
long[1]==10000;
0;



The purpose of source position is for
SyncerVisitor to find out which file to propagate.
In actual fact, there is another array called
priority. All files which are determined to be
equal (same hash if create/update, same new
name if rename, or file does not exist if delete)
are given equal priority.
During actual synchronization, only lower
priority indexes than that of the source position
will be affected. This is to prevent redundant file
or folder changes.
SyncerVisitor
Finally,
It
Next
Then,
The
willnext
itfirst
itwill
“Results.txt”
will
node
visit
visit
visit
to
“School
“Final.pdf”.
be visited
willWork”,
be is
determine
Since
“Proposal.docx”.
“CueSheet.docx”.
visited.
source
Since
the
position
the
source
Since
source
Since
is
position,
source
0,
the
it will
SyncerVisitor
With
that, all the
willfiles
now
and
visit the
andcopied
be
source
position
then
position
iscreate
over
0, and
1,
but
to
isaindex
it0,
the
folder
isand
more
other
2 when
it
is is the
tree. are now synchronized.
folders
necessary.
positions,
determined
most
updated
updated,
then
and
The
tothe
the
be
state
it will
rest,
equal,
state
of
propagate
itthe
of
only
will
the1
node
will
to
propagate
the
bewill
other
updated.
then
to2the
locations.
be other
updated.
nodes.
RootCompareObject
string[] paths
paths[0] = “C:\Users\Wysie\Desktop\A”
paths[1] = “C:\Users\Wysie\Desktop\B”
paths[2] = “C:\Users\Wysie\Desktop\C”
Index 0: C:\Users\Wysie\Desktop\A
Index 1: C:\Users\Wysie\Desktop\B
Index 2: C:\Users\Wysie\Desktop\C
FolderCompareObject
FileCompareObject
FileCompareObject
name = “School Work”
name = “CueSheet.docx”
name = “Results.txt”
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = true
exists[2] = true
false
bool[] exists;
exists[0] = true
exists[1] = true
exists[2] = true
false
string[] hash;
hash[0] = “QWERTY”;
hash[1] = “QWERTY”;
“MNBVC”;
hash[2] = “QWERTY”;
null;
string[] hash;
hash[0] = “VVBBB”;
“AAAAA”;
hash[1] = “VVBBB”;
hash[2] = “VVBBB”;
null;
long[] lastModified;
long[0] = 99999;
long[1] = 99999;
88888;
long[2] = 99999;
0;
long[] lastModified;
long[0] = 90000;
70000;
long[1] = 90000;
long[2] = 90000;
0;
srcPosition = 0
srcPosition = 1
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = true
false
exists[2] = true
srcPosition = 0
FileCompareObject
FileCompareObject
name = “Final.pdf”
name = “Proposal.docx”
numOfPaths = 3
numOfPaths = 3
bool[] exists;
exists[0] = true
exists[1] = true
false
exists[2] = true
false
bool[] exists;
exists[0] = true
exists[1] = true
false
exists[2] = true
string[] hash;
hash[0] = “ZXCVB”;
hash[1] = “ZXCVB”;;
null;
hash[2] = “ZXCVB”;;
null;
string[] hash;
hash[0] = “ASDFG”;
hash[1] = “ASDFG”;
null;
hash[2] = “ASDFG”;
long[] lastModified;
long[0] = 30000;
long[1] = 30000;
0;
long[2] = 30000;
0;
long[] lastModified;
long[0] = 10000;
long[1] = 10000;
0;
long[2] = 10000;
srcPosition = 0
srcPosition = 0

As stated earlier, a priority array in each node
is used to determine if a file is actually copied
over.
We hope this simple presentation will give you a
good overview of how the visitor pattern, and in
particular, how our merged tree, works.
 Many other functions and visitors were not
explained, please look at the detailed comments
in the source code, as well as the developer
guide, if you are interested.
 Traversing the tree can be pre, post, or levelorder traversal, depending on what is needed.
