Compression Decompression string with C

Question

I am newbie in  net  I am doing compression and decompression string in C   There is a XML and I am converting in string and after that I am doing compression and decompression There is no compilation error in my code except when I decompression my code and return my string  its returning only half of the XML   Below is my code  please correct me where I am wrong   Code   class Program       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               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  lt  rByte  i                          sB Append  char byteArray i                      sr Close            ms Close            sr Dispose            ms Dispose            return sB ToString               static void Main string   args                XDocument doc   XDocument Load   D  RSP xml            string val   doc ToString SaveOptions DisableFormatting           val   Zip val           val   UnZip val              My XML size is 63KB

User · Answer

For those who still getting The magic number in GZip header is not correct  Make sure you are passing in a GZip stream  ERROR and if your string was zipped using php you ll need to do something like          public static string decodeDecompress string originalReceivedSrc            byte   bytes   Convert FromBase64String originalReceivedSrc            using  var mem   new MemoryStream                    the trick is here             mem Write new byte     0x1f  0x8b  0x08  0x00  0x00  0x00  0x00  0x00    0  8               mem Write bytes  0  bytes Length                mem Position   0               using  var gzip   new GZipStream mem  CompressionMode Decompress               using  var reader   new StreamReader gzip                     return reader ReadToEnd

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I like  fubo s answer the best but I think this is much more elegant  This method is more compatible because it doesn t manually store the length up front  Also I ve exposed extensions to support compression for string to string  byte   to byte    and Stream to Stream  public static class ZipExtensions       public static string CompressToBase64 this string data                return Convert ToBase64String Encoding UTF8 GetBytes data  Compress                public static string DecompressFromBase64 this string data                return Encoding UTF8 GetString Convert FromBase64String data  Decompress                    public static byte   Compress this byte   data                using  var sourceStream   new MemoryStream data           using  var destinationStream   new MemoryStream                          sourceStream CompressTo destinationStream               return destinationStream ToArray                         public static byte   Decompress this byte   data                using  var sourceStream   new MemoryStream data           using  var destinationStream   new MemoryStream                          sourceStream DecompressTo destinationStream               return destinationStream ToArray                             public static void CompressTo this Stream stream  Stream outputStream                using  var gZipStream   new GZipStream outputStream  CompressionMode Compress                         stream CopyTo gZipStream               gZipStream Flush                         public static void DecompressTo this Stream stream  Stream outputStream                using  var gZipStream   new GZipStream stream  CompressionMode Decompress                         gZipStream CopyTo outputStream

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according to  this snippet  i use this code and it s working fine   using System  using System IO  using System IO Compression  using System Text   namespace CompressString       internal static class StringCompressor                    lt summary gt              Compresses the string               lt  summary gt               lt param name  text  gt The text  lt  param gt               lt returns gt  lt  returns gt          public static string CompressString string text                        byte   buffer   Encoding UTF8 GetBytes text               var memoryStream   new MemoryStream                using  var gZipStream   new GZipStream memoryStream  CompressionMode Compress  true                                 gZipStream Write buffer  0  buffer Length                              memoryStream Position   0               var compressedData   new byte memoryStream Length               memoryStream Read compressedData  0  compressedData Length                var gZipBuffer   new byte compressedData Length   4               Buffer BlockCopy compressedData  0  gZipBuffer  4  compressedData Length               Buffer BlockCopy BitConverter GetBytes buffer Length   0  gZipBuffer  0  4               return Convert ToBase64String gZipBuffer                           lt summary gt              Decompresses the string               lt  summary gt               lt param name  compressedText  gt The compressed text  lt  param gt               lt returns gt  lt  returns gt          public static string DecompressString string compressedText                        byte   gZipBuffer   Convert FromBase64String compressedText               using  var memoryStream   new MemoryStream                                  int dataLength   BitConverter ToInt32 gZipBuffer  0                   memoryStream Write gZipBuffer  4  gZipBuffer Length - 4                    var buffer   new byte dataLength                    memoryStream Position   0                  using  var gZipStream   new GZipStream memoryStream  CompressionMode Decompress                                         gZipStream Read buffer  0  buffer Length                                      return Encoding UTF8 GetString buffer

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The code to compress decompress a string  public static void CopyTo Stream src  Stream dest        byte   bytes   new byte 4096        int cnt       while   cnt   src Read bytes  0  bytes Length      0            dest Write bytes  0  cnt            public static byte   Zip string str        var bytes   Encoding UTF8 GetBytes str        using  var msi   new MemoryStream bytes       using  var mso   new MemoryStream              using  var gs   new GZipStream mso  CompressionMode Compress                   msi CopyTo gs               CopyTo msi  gs                      return mso ToArray             public static string Unzip byte   bytes        using  var msi   new MemoryStream bytes       using  var mso   new MemoryStream              using  var gs   new GZipStream msi  CompressionMode Decompress                   gs CopyTo mso               CopyTo gs  mso                      return Encoding UTF8 GetString mso ToArray              static void Main string   args        byte   r1   Zip  StringStringStringStringStringStringStringStringStringStringStringStringStringString        string r2   Unzip r1       Remember that Zip returns a byte    while Unzip returns a string  If you want a string from Zip you can Base64 encode it  for example by using Convert ToBase64String r1    the result of Zip is VERY binary  It isn t something you can print to the screen or write directly in an XML   The version suggested is for  NET 2 0  for  NET 4 0 use the MemoryStream CopyTo   IMPORTANT  The compressed contents cannot be written to the output stream until the GZipStream knows that it has all of the input  i e   to effectively compress it needs all of the data   You need to make sure that you Dispose   of the GZipStream before inspecting the output stream  e g   mso ToArray     This is done with the using       block above  Note that the GZipStream is the innermost block and the contents are accessed outside of it  The same goes for decompressing  Dispose   of the GZipStream before attempting to access the data

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This is an updated version for  NET 4 5 and newer using async await and IEnumerables   public static class CompressionExtensions       public static async Task lt IEnumerable lt byte gt  gt  Zip this object obj                byte   bytes   obj Serialize             using  MemoryStream msi   new MemoryStream bytes           using  MemoryStream mso   new MemoryStream                          using  var gs   new GZipStream mso  CompressionMode Compress                   await msi CopyToAsync gs                return mso ToArray   AsEnumerable                         public static async Task lt object gt  Unzip this byte   bytes                using  MemoryStream msi   new MemoryStream bytes           using  MemoryStream mso   new MemoryStream                          using  var gs   new GZipStream msi  CompressionMode Decompress                                    Sync example                    gs CopyTo mso                       Async way  take care of using async keyword on the method definition                  await gs CopyToAsync mso                              return mso ToArray   Deserialize                       public static class SerializerExtensions       public static byte   Serialize lt T gt  this T objectToWrite                using  MemoryStream stream   new MemoryStream                          BinaryFormatter binaryFormatter   new BinaryFormatter                binaryFormatter Serialize stream  objectToWrite                return stream GetBuffer                         public static async Task lt T gt   Deserialize lt T gt  this byte   arr                using  MemoryStream stream   new MemoryStream                          BinaryFormatter binaryFormatter   new BinaryFormatter                await stream WriteAsync arr  0  arr Length               stream Position   0               return  T binaryFormatter Deserialize stream                        public static async Task lt object gt  Deserialize this byte   arr                object obj   await arr  Deserialize lt object gt             return obj            With this you can serialize everything BinaryFormatter supports  instead only of strings   Edit   In case  you need take care of Encoding  you could just use Convert ToBase64String byte        Take a look at this answer if you need an example

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We can reduce code complexity by using StreamReader and StreamWriter rather than manually converting strings to byte arrays   Three streams is all you need      public static byte   Zip string uncompressed                byte   ret          using  var outputMemory   new MemoryStream                          using  var gz   new GZipStream outputMemory  CompressionLevel Optimal                                 using  var sw   new StreamWriter gz  Encoding UTF8                                         sw Write uncompressed                                               ret   outputMemory ToArray                      return ret             public static string Unzip byte   compressed                string ret   null          using  var inputMemory   new MemoryStream compressed                         using  var gz   new GZipStream inputMemory  CompressionMode Decompress                                 using  var sr   new StreamReader gz  Encoding UTF8                                         ret   sr ReadToEnd                                                      return ret

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With the advent of  NET 4 0  and higher  with the Stream CopyTo   methods  I thought I would post an updated approach   I also think the below version is useful as a clear example of a self-contained class for compressing regular strings to Base64 encoded strings  and vice versa   public static class StringCompression            lt summary gt          Compresses a string and returns a deflate compressed  Base64 encoded string           lt  summary gt           lt param name  uncompressedString  gt String to compress lt  param gt      public static string Compress string uncompressedString                byte   compressedBytes           using  var uncompressedStream   new MemoryStream Encoding UTF8 GetBytes uncompressedString                          using  var compressedStream   new MemoryStream                                      setting the leaveOpen parameter to true to ensure that compressedStream will not be closed when compressorStream is disposed                    this allows compressorStream to close and flush its buffers to compressedStream and guarantees that compressedStream ToArray   can be called afterward                    although MSDN documentation states that ToArray   can be called on a closed MemoryStream  I don t want to rely on that very odd behavior should it ever change                 using  var compressorStream   new DeflateStream compressedStream  CompressionLevel Fastest  true                                         uncompressedStream CopyTo compressorStream                                         call compressedStream ToArray   after the enclosing DeflateStream has closed and flushed its buffer to compressedStream                 compressedBytes   compressedStream ToArray                                     return Convert ToBase64String compressedBytes                   lt summary gt          Decompresses a deflate compressed  Base64 encoded string and returns an uncompressed string           lt  summary gt           lt param name  compressedString  gt String to decompress  lt  param gt      public static string Decompress string compressedString                byte   decompressedBytes           var compressedStream   new MemoryStream Convert FromBase64String compressedString             using  var decompressorStream   new DeflateStream compressedStream  CompressionMode Decompress                         using  var decompressedStream   new MemoryStream                                  decompressorStream CopyTo decompressedStream                    decompressedBytes   decompressedStream ToArray                                     return Encoding UTF8 GetString decompressedBytes           Here   s another approach using the extension methods technique to extend the String class to add string compression and decompression  You can drop the class below into an existing project and then use thusly   var uncompressedString    Hello World    var compressedString   uncompressedString Compress      and  var decompressedString   compressedString Decompress      To wit   public static class Extensions            lt summary gt          Compresses a string and returns a deflate compressed  Base64 encoded string           lt  summary gt           lt param name  uncompressedString  gt String to compress lt  param gt      public static string Compress this string uncompressedString                byte   compressedBytes           using  var uncompressedStream   new MemoryStream Encoding UTF8 GetBytes uncompressedString                          using  var compressedStream   new MemoryStream                                      setting the leaveOpen parameter to true to ensure that compressedStream will not be closed when compressorStream is disposed                    this allows compressorStream to close and flush its buffers to compressedStream and guarantees that compressedStream ToArray   can be called afterward                    although MSDN documentation states that ToArray   can be called on a closed MemoryStream  I don t want to rely on that very odd behavior should it ever change                 using  var compressorStream   new DeflateStream compressedStream  CompressionLevel Fastest  true                                         uncompressedStream CopyTo compressorStream                                         call compressedStream ToArray   after the enclosing DeflateStream has closed and flushed its buffer to compressedStream                 compressedBytes   compressedStream ToArray                                     return Convert ToBase64String compressedBytes                   lt summary gt          Decompresses a deflate compressed  Base64 encoded string and returns an uncompressed string           lt  summary gt           lt param name  compressedString  gt String to decompress  lt  param gt      public static string Decompress this string compressedString                byte   decompressedBytes           var compressedStream   new MemoryStream Convert FromBase64String compressedString             using  var decompressorStream   new DeflateStream compressedStream  CompressionMode Decompress                         using  var decompressedStream   new MemoryStream                                  decompressorStream CopyTo decompressedStream                    decompressedBytes   decompressedStream ToArray                                     return Encoding UTF8 GetString decompressedBytes

[c#] Compression/Decompression string with C#

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