CODEWITHSUNDEEP
c#stringcompression
thar
thar

Reputation: 51

C# Compress a string of characters

Say 1 character is 1Byte, so i have 10 characters, and that is 10Bytes.

I have a sentence which contains of 20 characters and i need to upload this sentence to a server. and the limit is only 10 Bytes, how do i compress this sentence which is 20Bytes to 10Bytes.

Is there anyway i can do this via C# ?

EDIT

I have a 170 character sentence, i need to compress it in a way that it seems to be like 130characters. i am uploading this sentence to a 3rd party server, so i dont have any control over the server. Can this be done ?

Upvotes: 0

Views: 2191

Answers (5)

Tremmors
Tremmors

Reputation: 2966

What you want should be possible most of the time, but I can guarantee problems. If you wrote a method using the GZipStream class, it could take this 170 byte string you have and reduce it. Like most people have said, the compression ratio really depends on the content itself.

Just as a test: I took a string of "0123456789" repeating 17 times (for 170 characters), gzipped it and it reduced to 21 characters.
If I take a string of 170 zeros and gzip it, it gets reduced to 12 characters. I took 170 bytes of random code, and it gets reduced down to 79 characters.

So in these cases, it would compress it down to fit into your space requirements; but there's no way to predict when and how often it wouldn't. The compression ratio may end up being 1:1 and there is an inherent overhead in creating the block structure, so it could actually result in compressed length of slightly larger than the original. Then again, you may have to base64 encode the whole thing to make it store properly in the DB, so that would increase your overhead even more.

Upvotes: 1

jason
jason

Reputation: 241779

You have a serious problem here. Twenty bytes is 160 bits is 2^160 possible messages. Ten bytes is 80 bits is 2^80 possible messages. Unless you have some way to reduce your source message space to only containing 2^80 possible messages, you can not do this.

Upvotes: 1

Ghassen Hamrouni
Ghassen Hamrouni

Reputation: 3168

You can't, compression ratio depends on the content of the string itself. And even if you can compress the sequence, you must implement the decompression on the server too. But if you have access to the server you can simply divide the sequence in many parts.

Upvotes: 1

0x5f3759df
0x5f3759df

Reputation: 2359

If the messages are static, pass indices into an array containing the different messages it could be sending instead of passing the messages. If they're dynamic, then it's simply not possible unless you can limit yourself to a limited subset of ASCII and store multiple characters in one byte, or the string is extremely repetitive in which case you could consider Run-Length Encoding.

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1503409

Well you can't do it in a guaranteed way, no. There are far more possible sequences of 20 bytes than there are sequences of 10 bytes - so you can't possibly compress every sequence of 20 bytes reversibly into 10 bytes.

In general compression doesn't typically work very well with very small input lengths.

If you know that all your input will actually be (say) A-Z and space (i.e. 27 characters) then that's 5 bits... so you only need 100 bits in total. That's still a bit more than the 80 bits you have available, so you still couldn't guarantee to represent all sentences. You could make "common" characters shorter than "unusual" characters though, and get many sentences to work that way.

It's hard to be more specific without knowing what you really need to achieve, given the impossibility of the original requirement.

Upvotes: 2

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