Compress a string

[Hugh Janus]

Hi all,

I have several *long* strings (see bottom of post for an example) which
I will be sending across a network. Therefore, I want to compress them
for speed and because later they will be stored in a DB.
I found this code here http://abstractvb.com/code.asp?A=931 but it
doesn't seem to give me a particuarly good level of compression it
seems. As you can see in the article below, there is a lot of
repitition. So I was hoping that someone here could tell me that
either the code at the link is correct, what is wrong with it or of
another method I could use to compress my string(s).
TIA

AAAAA4fug4AtAnNIbgBTM0hVGhpcyBwcm9ncmFtIGNhbm5vdCB iZSBydW4gaW4gRE9TIG1vZGUuDQ0KJAAAAAAAAABQmnOxFPsd4 hT7HeIU+x3iEfdA4hb7HeIR9xLiFfsd4hH3QuIb+x3iB/NA4hb7HeKX80DiHfsd4hT7HOJY+x3iEfd94hD7HeIR90fiFfsd 4lJpY2gU+x3iAAAAAAAAAAAAAAAAAAAAAFBFAABMAQMAeaGCQQ AAAAAAAAAA4AAPAQsBBwoAEAAAABIAAAAAAADjGgAAABAAAAAg AAAAAEAAABAAAAACAAAEAAAAAAAAAAQAAAAAAAAAAEAAAAAEAA DXjAAAAwAAAAAAEAAAEAAAAAAQAAAQAAAAAAAAEAAAAAAAAAAA AAAAlCMAAIwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAEAhAAAcAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 4CIAAEgAAAAAAAAAAAAAAAAgAABAAQAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAALnRleHQAAAA0DgAAABAAAAAQAAAABAAAAAAA AAAAAAAAAAAAIAAAYC5yZGF0YQAAtAoAAAAgAAAADAAAABQAAA AAAAAAAAAAAAAAAEAAAEAuZGF0YQAAAEQFAAAAMAAAAAIAAAAg AAAAAAAAAAAAAAAAAABAAADAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAIPsJDPAiUQk DFaJRCQUjUwkDFGJRCQcaAEAAICJRCQkjVQkGIlEJChSUMdEJB gAAAAAx0QkFAAAAAAz9olEJDToPQcAAIXAD4WvAAAAi0wkDFeN RCQIUGoMUeg1BwAAhcB1PotEJAiLcCiLfCQwM9KF9g+VwoX/i/J0eoX2dHYPtwiLUARRUlf/FYggQACLRCQUD7cIZscETwAAi0QkFOtRi0QkEI1UJAxSagNQ6O IGAACFwHVFi0QkDItQCIt8JDAzyYXSD5XBhf+L8XQnhfZ0Iw+3 EItABFJQV/8ViCBAAItMJBgPtxFmxwRXAACLRCQYg8QMUOiTBgAAX4tEJAxQ 6IIGAACLxl6DxCTDzMzMg+wooRQwQACJRCQkM8CJRCQGiUQkCo lEJA5TiUQkFlWJRCQeVolEJCaNTCQQV4lEJC5RZsdEJBgAAGaJ RCQ26Kz+//+LfCRAalxXi9j/FZAgQACLLYwgQACL8IPEDIX2dCeLRCRAjVYCUlD/1Sv30f5WV4t8JFRX/xWIIEAAg8QUZscEdwAA6yWLTCRAV1H/1Yt8JEyDxAiF23QNjVQkFFJX/9WDxAjrBWbHBwAAi1wkSIXbD4SoAAAAaHAhQABoXCFAAP8VbCB AAFD/FXAgQABmxwMAAGaDPwCL8A+EgAAAAIX2dEKNRCQQUGgAAAEAag BqAFdqAP/WhcB0F41MJBBRaAAAAgBqAGoAV2oA/9aFwHVOi1QkEIsCUFP/1YtMJBiDxAhR6zVoIDBAAFdqAOg3BQAAhcB0EWggMEAAV2oA6C AFAACFwHUYixUgMEAAUlP/1aEgMEAAg8QIUOj+BAAAi0wkNF9eXTPAW+hUCAAAg8Qow8zMzM zMzMzMzMzMg+wYVsdEJAQEAAAA/xU0IUAAi/CF9nUFXoPEGMNX/xVkIEAAUP8VMCFAAIv4hf90SmoBjUQkEFD/FRwgQABqAGoAagGNTCQYUf8VICBAAI1UJAxSjUQkDFBWizU4IU AA/9aFwHUd/xVoIEAAUGiwIUAA/xWUIEAAg8QIXzPAXoPEGMONTCQMUY1UJAxSV//WhcB1Hf8VaCBAAFBogCFAAP8VlCBAAIPECF8zwF6DxBjDX7gBA AAAXoPEGMPMzMzMg+wYU1ZXavb/FVwgQACLNWAgQACL+LsBAAAA6wONSQCNRCQMUFONTCQYUVf/1oXAdO6LRCQMhcB25mY5XCQQdd+LRCQUhcB012aLRCQeZoXAdM 1fXluDxBjDzMzMzMzMUVNVVldq9v8VXCBAAItMJBiL6KGkIE

[Hugh Janus]

p.s. all the other examples i find are for compressing files. I want
to compress a string in memory, send it and then discard.

[Meelis Lilbok]

Maybe something like RLE compression?
Meelis
"Hugh Janus" <my*************@hotmail.com> wrote in message
news:11**********************@i40g2000cwc.googlegr oups.com...

Hi all,

I have several *long* strings (see bottom of post for an example) which
I will be sending across a network. Therefore, I want to compress them
for speed and because later they will be stored in a DB.
I found this code here http://abstractvb.com/code.asp?A=931 but it
doesn't seem to give me a particuarly good level of compression it
seems. As you can see in the article below, there is a lot of
repitition. So I was hoping that someone here could tell me that
either the code at the link is correct, what is wrong with it or of
another method I could use to compress my string(s).
TIA

AAAAA4fug4AtAnNIbgBTM0hVGhpcyBwcm9ncmFtIGNhbm5vdCB iZSBydW4gaW4gRE9TIG1vZGUuDQ0KJAAAAAAAAABQmnOxFPsd4 hT7HeIU+x3iEfdA4hb7HeIR9xLiFfsd4hH3QuIb+x3iB/NA4hb7HeKX80DiHfsd4hT7HOJY+x3iEfd94hD7HeIR90fiFfsd 4lJpY2gU+x3iAAAAAAAAAAAAAAAAAAAAAFBFAABMAQMAeaGCQQ AAAAAAAAAA4AAPAQsBBwoAEAAAABIAAAAAAADjGgAAABAAAAAg AAAAAEAAABAAAAACAAAEAAAAAAAAAAQAAAAAAAAAAEAAAAAEAA DXjAAAAwAAAAAAEAAAEAAAAAAQAAAQAAAAAAAAEAAAAAAAAAAA AAAAlCMAAIwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAEAhAAAcAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 4CIAAEgAAAAAAAAAAAAAAAAgAABAAQAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAALnRleHQAAAA0DgAAABAAAAAQAAAABAAAAAAA AAAAAAAAAAAAIAAAYC5yZGF0YQAAtAoAAAAgAAAADAAAABQAAA AAAAAAAAAAAAAAAEAAAEAuZGF0YQAAAEQFAAAAMAAAAAIAAAAg AAAAAAAAAAAAAAAAAABAAADAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAIPsJDPAiUQk DFaJRCQUjUwkDFGJRCQcaAEAAICJRCQkjVQkGIlEJChSUMdEJB gAAAAAx0QkFAAAAAAz9olEJDToPQcAAIXAD4WvAAAAi0wkDFeN RCQIUGoMUeg1BwAAhcB1PotEJAiLcCiLfCQwM9KF9g+VwoX/i/J0eoX2dHYPtwiLUARRUlf/FYggQACLRCQUD7cIZscETwAAi0QkFOtRi0QkEI1UJAxSagNQ6O IGAACFwHVFi0QkDItQCIt8JDAzyYXSD5XBhf+L8XQnhfZ0Iw+3 EItABFJQV/8ViCBAAItMJBgPtxFmxwRXAACLRCQYg8QMUOiTBgAAX4tEJAxQ 6IIGAACLxl6DxCTDzMzMg+wooRQwQACJRCQkM8CJRCQGiUQkCo lEJA5TiUQkFlWJRCQeVolEJCaNTCQQV4lEJC5RZsdEJBgAAGaJ RCQ26Kz+//+LfCRAalxXi9j/FZAgQACLLYwgQACL8IPEDIX2dCeLRCRAjVYCUlD/1Sv30f5WV4t8JFRX/xWIIEAAg8QUZscEdwAA6yWLTCRAV1H/1Yt8JEyDxAiF23QNjVQkFFJX/9WDxAjrBWbHBwAAi1wkSIXbD4SoAAAAaHAhQABoXCFAAP8VbCB AAFD/FXAgQABmxwMAAGaDPwCL8A+EgAAAAIX2dEKNRCQQUGgAAAEAag BqAFdqAP/WhcB0F41MJBBRaAAAAgBqAGoAV2oA/9aFwHVOi1QkEIsCUFP/1YtMJBiDxAhR6zVoIDBAAFdqAOg3BQAAhcB0EWggMEAAV2oA6C AFAACFwHUYixUgMEAAUlP/1aEgMEAAg8QIUOj+BAAAi0wkNF9eXTPAW+hUCAAAg8Qow8zMzM zMzMzMzMzMg+wYVsdEJAQEAAAA/xU0IUAAi/CF9nUFXoPEGMNX/xVkIEAAUP8VMCFAAIv4hf90SmoBjUQkEFD/FRwgQABqAGoAagGNTCQYUf8VICBAAI1UJAxSjUQkDFBWizU4IU AA/9aFwHUd/xVoIEAAUGiwIUAA/xWUIEAAg8QIXzPAXoPEGMONTCQMUY1UJAxSV//WhcB1Hf8VaCBAAFBogCFAAP8VlCBAAIPECF8zwF6DxBjDX7gBA AAAXoPEGMPMzMzMg+wYU1ZXavb/FVwgQACLNWAgQACL+LsBAAAA6wONSQCNRCQMUFONTCQYUVf/1oXAdO6LRCQMhcB25mY5XCQQdd+LRCQUhcB012aLRCQeZoXAdM 1fXluDxBjDzMzMzMzMUVNVVldq9v8VXCBAAItMJBiL6KGkIE

[Hugh Janus]

Meelis Lilbok wrote:

Maybe something like RLE compression?

errrr.... sounds good. but no idea what it is! Could you expand on
that?
Hugh

[Meelis Lilbok]

http://www.prepressure.com/techno/compressionrle.htm
I try to find a class writen by me, i used it befgore for something :))
Meelis

"Hugh Janus" <my*************@hotmail.com> wrote in message
news:11*********************@f6g2000cwb.googlegrou ps.com...

Meelis Lilbok wrote:

Maybe something like RLE compression?

errrr.... sounds good. but no idea what it is! Could you expand on
that?
Hugh

[Hugh Janus]

Meelis Lilbok wrote:

http://www.prepressure.com/techno/compressionrle.htm
I try to find a class writen by me, i used it befgore for something :))
Meelis

Thanks Meelis, I have a feeling that that is what the code in the link
i posted does, or so it looks to me. What do you think? Either ways,
I would be interested in trying your class to see which one works
better!

[Meelis Lilbok]

Here, i found my class.

It works, when in your text are 4-255 repeated characters, if there are more
chars then 255 repated, you must modify my code

Works like this

a) Searches repated charactes and counts them
b) If character changes, saves control character, count of repated
charaters(as byte) and character to result string
Hope this helps a little bit ;)
meelis

"Hugh Janus" <my*************@hotmail.com> wrote in message
news:11**********************@u72g2000cwu.googlegr oups.com...

Meelis Lilbok wrote:

http://www.prepressure.com/techno/compressionrle.htm
I try to find a class writen by me, i used it befgore for something :))
Meelis

Thanks Meelis, I have a feeling that that is what the code in the link
i posted does, or so it looks to me. What do you think? Either ways,
I would be interested in trying your class to see which one works
better!

[Meelis Lilbok]

ooops sry, there was a bug in my first code

rle2.zip is correc one :)

Meelis

"Meelis Lilbok" <me***********@deltmar.ee> wrote in message
news:ei**************@TK2MSFTNGP05.phx.gbl...

Here, i found my class.

It works, when in your text are 4-255 repeated characters, if there are
more
chars then 255 repated, you must modify my code

Works like this

a) Searches repated charactes and counts them
b) If character changes, saves control character, count of repated
charaters(as byte) and character to result string
Hope this helps a little bit ;)
meelis

"Hugh Janus" <my*************@hotmail.com> wrote in message
news:11**********************@u72g2000cwu.googlegr oups.com...

Meelis Lilbok wrote:

http://www.prepressure.com/techno/compressionrle.htm
I try to find a class writen by me, i used it befgore for something :))
Meelis

Thanks Meelis, I have a feeling that that is what the code in the link
i posted does, or so it looks to me. What do you think? Either ways,
I would be interested in trying your class to see which one works
better!

[Hugh Janus]

Meelis Lilbok wrote:

Here, i found my class.

It works, when in your text are 4-255 repeated characters, if there are more
chars then 255 repated, you must modify my code

Works like this

a) Searches repated charactes and counts them
b) If character changes, saves control character, count of repated
charaters(as byte) and character to result string
Hope this helps a little bit ;)

Thanks! But your file is not attached. Could you paste the class file
here as text?

Also, what if I do not know how many repeated characters there are in
my string? You say that yours works for 4-255 repeated characters, but
what if the number is unknown?

Hugh

[Meelis Lilbok]

Public Class clsCompress
Public Function CompressString(ByVal controlchar As String, ByVal text As
String) As String
Dim iPos As Integer, iLen As Integer, iCharCnt As Integer = 1, sChar As
String
Dim sResult As New System.Text.StringBuilder
'Get string length
iLen = text.Length
'Get first char
sChar = Left$(text, 1)
'Loop trough string
For iPos = 2 To iLen
'If char has changed
If sChar <> Mid$(text, iPos, 1) Then
'If CharCount is bigger then 3, add countrol char, count of chars as
Chrw(count) and char
If iCharCnt > 3 Then
sResult.Append(controlchar & ChrW(iCharCnt) & sChar)
iCharCnt = 1
Else
'Add just char
sResult.Append(sChar, iCharCnt)
iCharCnt = 1
End If
Else
'Get next char
sChar = Mid$(text, iPos, 1)
iCharCnt = iCharCnt + 1
End If
'Get next char
sChar = Mid$(text, iPos, 1)
Next
If iCharCnt > 3 Then
sResult.Append(controlchar & ChrW(iCharCnt) & sChar)
iCharCnt = 1
Else
'Add just char
sResult.Append(sChar, iCharCnt)
End If
Return sResult.ToString
End Function
End Class

[Meelis Lilbok]

This wersion works like this

lets say your string is abcdeeeeefg and control char is *
after compressing abcd*efg

now when there are more then 255 e-chars, my function does not work anymore.
then its must be modified to store length with 2 bytes
Sry, englis is not my native language ;)
Meelis



"Hugh Janus" <my*************@hotmail.com> wrote in message
news:11**********************@i40g2000cwc.googlegr oups.com...

Meelis Lilbok wrote:

Here, i found my class.

It works, when in your text are 4-255 repeated characters, if there are
more
chars then 255 repated, you must modify my code

Works like this

a) Searches repated charactes and counts them
b) If character changes, saves control character, count of repated
charaters(as byte) and character to result string
Hope this helps a little bit ;)

Thanks! But your file is not attached. Could you paste the class file
here as text?

Also, what if I do not know how many repeated characters there are in
my string? You say that yours works for 4-255 repeated characters, but
what if the number is unknown?

Hugh

[Hugh Janus]

Meelis Lilbok wrote:

This wersion works like this

lets say your string is abcdeeeeefg and control char is *
after compressing abcd*efg

now when there are more then 255 e-chars, my function does not work anymore.
then its must be modified to store length with 2 bytes
Sry, englis is not my native language ;)
Meelis

Ahhh, now I understand perfectly! thanks for your help. I think i'll
need to modify the code because I don't know if i will find more than
255 characters repeated, it is very possible. Do you know what changes
are required for your class to work with 2 bytes instead?

[Meelis Lilbok]

One solution is to use 255 length blocks :)
if count is 255 then counting starts again from 1
Meelis


"Hugh Janus" <my*************@hotmail.com> wrote in message
news:11*********************@c74g2000cwc.googlegro ups.com...

Meelis Lilbok wrote:

This wersion works like this

lets say your string is abcdeeeeefg and control char is *
after compressing abcd*efg

now when there are more then 255 e-chars, my function does not work
anymore.
then its must be modified to store length with 2 bytes
Sry, englis is not my native language ;)
Meelis

Ahhh, now I understand perfectly! thanks for your help. I think i'll
need to modify the code because I don't know if i will find more than
255 characters repeated, it is very possible. Do you know what changes
are required for your class to work with 2 bytes instead?

[sam.m.gardiner]

Do you have to write this code? or would it be acceptable to use a free
third-party open source .net library?

http://www.icsharpcode.com/OpenSourc...b/Default.aspx

I have used this library and whilst I can't give yuo any stats on speed
or compression I can at least say that it hasn't ever crashed ;-)

[Hugh Janus]

Meelis, your function works very well for me. Could you please post
the Uncompress function as well?