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newuser11 asked on

Zlib Compression

Hi,

Can someone help me with the following code. Basically my requirement is to create an archive (a zip file) with serveral files.

The following code opens the "testxml2.txt" file and tries to write it to the Test.Zip file. Test.zip file is getting created with 1KB but "write" operation is not working.


#define _WINDOWS
#define ZLIB_DLL

#include "zlib.h"
#include <fstream>
#include <iostream>

using namespace std;

int CompressFile(char type, char *filename, long startFilePos, char *outfilename, char fileAction);

enum {COMPRESS,UNCOMPRESS, NEWFILE, APPENDFILE};

int main(int argc, char *argv[])
{
      
      int error;

      error=CompressFile(COMPRESS, "c:\\testxml2.txt", 0, "Test.zip", NEWFILE);

      cout << "Error  " << error << endl;

      return 0;
}

int CompressFile(char type, char *filename, long startFilePos, char *outfilename, char fileAction)
{
      z_stream stream;
      int err;
      int level;
      ifstream inFile;
      ofstream outFile;
      bool done=false, atEOF=false;
      unsigned char *incData=NULL, *outData=NULL;
      int inSize, outSize, count;
      int BUFFER_SIZE=3000;

      level=3;
    stream.zalloc = Z_NULL;
    stream.zfree  = Z_NULL;
    stream.opaque = Z_NULL;

      // Initalize ZLIB
      if (type==COMPRESS)
            err = deflateInit(&stream, level);
      else
            err = inflateInit(&stream);

    if (err != Z_OK) return err;

      inSize=BUFFER_SIZE;
      outSize=inSize*(float)1.001+14;
      
      if ((incData=new unsigned char[inSize])==NULL)
      {err=Z_MEM_ERROR; goto cleanup;}
      
      if ((outData=new unsigned char[outSize])==NULL)
      {err=Z_MEM_ERROR; goto cleanup;}

      inFile.open(filename, ios::in);
      if (!inFile)
            goto cleanup;

      if (fileAction==NEWFILE)
            outFile.open(outfilename, ios::in | ios::app);
      else
            outFile.open(outfilename);
      if (!outFile)
            goto cleanup;

      if (startFilePos>0)
            inFile.seekg(startFilePos,ios::beg);
      
      stream.avail_in=0;
      stream.next_in=incData;
      stream.avail_out=outSize;
      stream.next_out=outData;
      //do
      //{
       while (stream.avail_in==0 && stream.avail_out==outSize && atEOF==false)
       {

            if (stream.avail_in==0)
            {
                  inFile.read((char *)incData,inSize);
                  cout << incData << endl;
                  stream.next_in=incData;
                  stream.avail_in=inFile.gcount();
                  atEOF=inFile.eof();
            }
              

            // Do some compressing
            if (type==COMPRESS)
                  err = deflate(&stream, Z_NO_FLUSH);
            else
                  err = inflate(&stream, Z_NO_FLUSH);

      
            if (err != Z_OK)
                  goto cleanup;
            
                  count=outSize-stream.avail_out;
                  if (count)
                     outFile.write((char *)outData,count);
                  stream.next_out=outData;
                  stream.avail_out=outSize;

}      

cleanup:

      inFile.close();
      outFile.close();

      if (err!=Z_OK)
            unlink(outfilename);

      if (type==COMPRESS)
            deflateEnd(&stream);
      else
            inflateEnd(&stream);
      
      if (incData!=NULL) delete incData;
      if (outData!=NULL) delete outData;

      return err;
}

Thanks.
C++

Avatar of undefined
Last Comment
Karl Heinz Kremer

8/22/2022 - Mon
Karl Heinz Kremer

Your problem is here;

    if (fileAction==NEWFILE)
          outFile.open(outfilename, ios::in | ios::app);

You are opening an ofstream with ios::in. This will not work. Change ios::in to ios::out, and you should be able to run your program (it works at least if I run it under Linux - I don't have zlib for Windows installed).
ASKER
newuser11

Hi khkremer,

When you said you were able to run it. Did it create a .zip file with the contents. For me it creates the zip file and it says it's not a valid archive file. When I try to uncompress it the file got created with 0 bytes.

Thanks.
ASKER CERTIFIED SOLUTION
Karl Heinz Kremer

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