Click here to Skip to main content
11,704,315 members (51,056 online)
Click here to Skip to main content

GZipStream - Compress/Decompress a string

, 23 Jun 2008 CPOL 143.4K 37
Rate this:
Please Sign up or sign in to vote.
An article on how use GZipStream with string as input parameter.

Introduction

This article presents two methods to compress and decompress strings using System.IO.Compression.GZipStream.

Context/Problem

After converting code from VB.NET 1.1 to C#.NET 3.5, I needed to change some code using a third party zip class to GZipStream. Code samples found on the web or on VS help where presenting solutions dealing with FileStream but in this case, a string is given as an input parameter.

So the little challenge was to go from a string to a byte array (byte[]) and vice versa without losing a char nor changing its encoding because I ended up finding that System.Text.Encoding.Unicode.GetBytes()/GetString() previously used in the VB code was not acting properly, resulting in a loss of characters. Plus the Flush() method on GZipStream with the compression option doesn't flush everything...

Tips

So as I found no method transforming a string into a byte[] and vice versa without involving encoding specifications, I ended up with a loop and a cast. If you have a better idea, please tell me so.

And I found out, if you only flush a GZipStream instance and retrieve the data from the underlying stream without closing this GZipStream instance, you miss part of the data.

The Code

Compress/Zip a string:

public static string Zip(string value)
{
    //Transform string into byte[]  
    byte[] byteArray = new byte[value.Length];
    int indexBA = 0;
    foreach (char item in value.ToCharArray())
    {
        byteArray[indexBA++] = (byte)item;
    }

    //Prepare for compress
    System.IO.MemoryStream ms = new System.IO.MemoryStream();
    System.IO.Compression.GZipStream sw = new System.IO.Compression.GZipStream(ms,
        System.IO.Compression.CompressionMode.Compress);

    //Compress
    sw.Write(byteArray, 0, byteArray.Length);
    //Close, DO NOT FLUSH cause bytes will go missing...
    sw.Close();

    //Transform byte[] zip data to string
    byteArray = ms.ToArray();
    System.Text.StringBuilder sB = new System.Text.StringBuilder(byteArray.Length);
    foreach (byte item in byteArray)
    {
        sB.Append((char)item);
    }
    ms.Close();
    sw.Dispose();
    ms.Dispose();
    return sB.ToString();
}

Decompress/Unzip a string: input value has been previously compressed with GZipStream.

public static string UnZip(string value)
{
    //Transform string into byte[]
    byte[] byteArray = new byte[value.Length];
    int indexBA = 0;
    foreach (char item in value.ToCharArray())
    {
        byteArray[indexBA++] = (byte)item;
    }

    //Prepare for decompress
    System.IO.MemoryStream ms = new System.IO.MemoryStream(byteArray);
    System.IO.Compression.GZipStream sr = new System.IO.Compression.GZipStream(ms,
        System.IO.Compression.CompressionMode.Decompress);

    //Reset variable to collect uncompressed result
    byteArray = new byte[byteArray.Length];

    //Decompress
    int rByte = sr.Read(byteArray, 0, byteArray.Length);

    //Transform byte[] unzip data to string
    System.Text.StringBuilder sB = new System.Text.StringBuilder(rByte);
    //Read the number of bytes GZipStream red and do not a for each bytes in
    //resultByteArray;
    for (int i = 0; i < rByte; i++)
    {
        sB.Append((char)byteArray[i]);
    }
    sr.Close();
    ms.Close();
    sr.Dispose();
    ms.Dispose();
    return sB.ToString();
}

Points of Interest

Well, if you haven't dealt with a lot of streams like me, hopefully this will avoid loss of time!

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Frankidoze
Systems Engineer
United States United States
No Biography provided

You may also be interested in...

Comments and Discussions

 
QuestionUse this code instead Pin
Jason Jakob17-Dec-14 12:28
memberJason Jakob17-Dec-14 12:28 
SuggestionThanks & a small correction! Pin
amitthk29-Sep-14 7:28
memberamitthk29-Sep-14 7:28 
GeneralMy vote of 1 Pin
Yclkvnc8-May-13 6:28
memberYclkvnc8-May-13 6:28 
GeneralMy vote of 4 Pin
Nasenbaaer12-Apr-13 6:24
memberNasenbaaer12-Apr-13 6:24 
SuggestionSharing my code Pin
SamNaseri16-Nov-11 18:38
memberSamNaseri16-Nov-11 18:38 
GeneralRe: Sharing my code Pin
Thymine20-Mar-12 11:40
memberThymine20-Mar-12 11:40 
GeneralRe: Sharing my code Pin
SamNaseri20-Mar-12 12:53
memberSamNaseri20-Mar-12 12:53 
GeneralRe: Sharing my code Pin
Frankidoze21-Mar-12 6:00
memberFrankidoze21-Mar-12 6:00 
GeneralThis code will work properly if Pin
Member 28508507-Jun-11 19:16
memberMember 28508507-Jun-11 19:16 
GeneralThis article is full of bugs, don't use it! Pin
xxbbcc28-May-11 16:51
memberxxbbcc28-May-11 16:51 
GeneralMy vote of 1 Pin
xxbbcc28-May-11 16:42
memberxxbbcc28-May-11 16:42 
GeneralMy vote of 1 Pin
djpitagora27-Sep-10 7:04
memberdjpitagora27-Sep-10 7:04 
GeneralRe: My vote of 1 Pin
Frankidoze21-Mar-12 5:50
memberFrankidoze21-Mar-12 5:50 
GeneralDecompress bug fix Pin
filoteanuadrian9-Apr-10 4:10
memberfiloteanuadrian9-Apr-10 4:10 
GeneralRe: Decompress bug fix Pin
TEST ME26-Apr-11 16:37
memberTEST ME26-Apr-11 16:37 
GeneralDoesn't work at all Pin
Vikcia26-Mar-10 7:49
memberVikcia26-Mar-10 7:49 
GeneralPublic Class CZip .... Pin
Erfan2-Feb-10 19:45
memberErfan2-Feb-10 19:45 
GeneralRe: Public Class CZip .... Pin
Nasenbaaer12-Apr-13 6:23
memberNasenbaaer12-Apr-13 6:23 
GeneralobjCompressedStream.Length not supported Pin
oops.uvj26-Aug-09 20:17
memberoops.uvj26-Aug-09 20:17 
GeneralPerformance Improvement/Cleanup Pin
matthias Weiser10-Dec-08 3:34
membermatthias Weiser10-Dec-08 3:34 
GeneralRe: Performance Improvement/Cleanup Pin
matthias Weiser10-Dec-08 3:48
membermatthias Weiser10-Dec-08 3:48 
GeneralIn the decompression to string the buffer size is wrong. A decompressed string may be larger than the original data. Pin
elinder91225-Sep-08 10:59
memberelinder91225-Sep-08 10:59 
GeneralFlush doesn't flush Pin
Richard Birkby8-Sep-08 3:16
memberRichard Birkby8-Sep-08 3:16 
Questiondecompressing binary concatenated files Pin
Robin Debnath25-Jul-08 3:27
memberRobin Debnath25-Jul-08 3:27 
AnswerRe: decompressing binary concatenated files Pin
Frankidoze2-Sep-08 5:11
memberFrankidoze2-Sep-08 5:11 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web01 | 2.8.150819.1 | Last Updated 23 Jun 2008
Article Copyright 2008 by Frankidoze
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid