Comments on: zlib – Looking the Gift Code in the Mouth http://marknelson.us/1997/01/01/zlib-engine/ Programming, mostly. Wed, 16 May 2012 08:30:05 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Mark Nelson http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-385304 Mark Nelson Wed, 05 Oct 2011 11:09:42 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-385304 @Skeeter: Unfortunately, what you see is what I have. I think the best bet for you is to use the Info-Zip DLLs with VB. This wasn't possible back in 2001, but it works just fine now: http://www.info-zip.org/ The Info-Zip DLLs are pretty well supported, and you will have an easier time keeping up with bug fixes and any future enhancements. - Mark @Skeeter:

Unfortunately, what you see is what I have.

I think the best bet for you is to use the Info-Zip DLLs with VB. This wasn’t possible back in 2001, but it works just fine now:

http://www.info-zip.org/

The Info-Zip DLLs are pretty well supported, and you will have an easier time keeping up with bug fixes and any future enhancements.

- Mark

]]> By: Skreener http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-385083 Skreener Tue, 04 Oct 2011 21:43:00 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-385083 Thanks for the reply Mark. The links seem to be for the ZlibTool.ocx but I can't see the code for ZlibOCX2.ocx. I think it was done in VC++5 back in 2001 to support VB5, or the the code essentially the same for both using the same ZlibEngine class? Just to say thanks for what you have contributed to the programming world! I know it has helped me. Thanks for the reply Mark. The links seem to be for the ZlibTool.ocx but I can’t see the code for ZlibOCX2.ocx. I think it was done in VC++5 back in 2001 to support VB5, or the the code essentially the same for both using the same ZlibEngine class?

Just to say thanks for what you have contributed to the programming world! I know it has helped me.

]]> By: Mark Nelson http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-385052 Mark Nelson Tue, 04 Oct 2011 20:12:21 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-385052 @Skreener: There are links to all the source code at the bottom of this article. Note that zlib has been through quite a few revisions since the code was first posted. - Mark @Skreener:

There are links to all the source code at the bottom of this article.

Note that zlib has been through quite a few revisions since the code was first posted.

- Mark

]]> By: Skreener http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-385050 Skreener Tue, 04 Oct 2011 20:07:32 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-385050 I have used your zlibocx2 dll (now only available at http://www.dogma.net/markn/ZlibOCX2.dll) for almost 10 years now in a VB6 project and have compressed and decompressed millions of files over that period without a problem. However now I have to port to C# 64bit and I have been trying some of the C# ports out there for zlib. While they seem to work in general but I am occasionally having problems with some of the files that were originally compressed with zlibocx2 that seem to be related to buffer problems on deflation. Could you make the source code for zlibocx2 avaibale so that I could try and figure out what the issue is or do you have any pointers as to what it could be? I have used your zlibocx2 dll (now only available at http://www.dogma.net/markn/ZlibOCX2.dll) for almost 10 years now in a VB6 project and have compressed and decompressed millions of files over that period without a problem. However now I have to port to C# 64bit and I have been trying some of the C# ports out there for zlib. While they seem to work in general but I am occasionally having problems with some of the files that were originally compressed with zlibocx2 that seem to be related to buffer problems on deflation. Could you make the source code for zlibocx2 avaibale so that I could try and figure out what the issue is or do you have any pointers as to what it could be?

]]> By: Mark Nelson http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-333653 Mark Nelson Fri, 08 Oct 2010 12:02:20 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-333653 @Srivatsan: Suggest you first make sure you can unzip the file using minigzip, which comes with the zlib distribution. If that works, compare its code to yours and see where the problem lies. - Mark @Srivatsan:

Suggest you first make sure you can unzip the file using minigzip, which comes with the zlib distribution. If that works, compare its code to yours and see where the problem lies.

- Mark

]]> By: Srivatsan http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-333644 Srivatsan Fri, 08 Oct 2010 09:08:56 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-333644 Hi, I have a file which is 5000000 bytes size and after gzip compression it is coming out to 5123 bytes. I tried to use zlib to uncompress the same file but it is not getting me the last 2880 bytes. Why is this ? I have followed the procedure as given in zlib manual. I am using the zlib version 1.2.3. [c] int inf(FILE *source, FILE *dest) { int ret; unsigned have; int have1; z_stream strm; unsigned char in[CHUNK]; unsigned char out[CHUNK]; int err; int total; /* allocate inflate state */ strm.zalloc = Z_NULL; strm.zfree = Z_NULL; strm.opaque = Z_NULL; strm.avail_out = (5*1024*1024); total = strm.avail_out; strm.next_out = out; strm.outcb = (cb_func)temp; /* decompress until deflate stream ends or end of file */ int i = fread(in, 1, CHUNK, source); if (ferror(source)) { (void)inflateEnd(&strm); } strm.avail_in = 5213; strm.next_in = in; ret = inflateInit2(&strm, 47); have = CHUNK; if (ret == Z_OK) { for (;;) { printf("value of total is %d\n",have); strm.next_out = out; /* discard the output */ strm.avail_out = have; err = inflate(&strm, Z_FINISH); if (err == Z_STREAM_END) { printf("stream end"); break; } i = fwrite(out, 1, have, dest); total = total - have; have1 = (total - CHUNK); if(have1 > CHUNK) have = CHUNK; else have = have1; } if ((err == Z_OK) || (err == Z_STREAM_END)) { printf("value of tota32 is %d\n",total); err = inflateEnd(&strm); } } printf("value of total2 is %d\n",total); return err; } [/c] Need some guidance on using the inflate function. Hi,

I have a file which is 5000000 bytes size and after gzip compression it is coming out to 5123 bytes. I tried to use zlib to uncompress the same file but it is not getting me the last 2880 bytes. Why is this ? I have followed the procedure as given in zlib manual. I am using the zlib version 1.2.3.

PLAIN TEXT
C:
  1. int inf(FILE *source, FILE *dest)
  2. {
  3. int ret;
  4. unsigned have;
  5. int have1;
  6. z_stream strm;
  7. unsigned char in[CHUNK];
  8. unsigned char out[CHUNK];
  9. int err;
  10. int total;
  11.  
  12.  
  13. /* allocate inflate state */
  14. strm.zalloc = Z_NULL;
  15. strm.zfree = Z_NULL;
  16. strm.opaque = Z_NULL;
  17. strm.avail_out = (5*1024*1024);
  18. total = strm.avail_out;
  19. strm.next_out = out;
  20. strm.outcb = (cb_func)temp;
  21.  
  22. /* decompress until deflate stream ends or end of file */
  23.  int i = fread(in, 1, CHUNK, source);
  24.  
  25. if (ferror(source)) {
  26. (void)inflateEnd(&strm);
  27. }
  28. strm.avail_in = 5213;
  29. strm.next_in = in;
  30.  
  31. ret = inflateInit2(&strm, 47);
  32. have = CHUNK;
  33.  
  34. if (ret == Z_OK)
  35.     {
  36.             for (;;) {
  37.  
  38.                 printf("value of total is %d\n",have);
  39.  
  40.                 strm.next_out = out;            /* discard the output */
  41.                 strm.avail_out = have;
  42.                 err = inflate(&strm, Z_FINISH);
  43.                 if (err == Z_STREAM_END)
  44.                 {
  45.                         printf("stream end");
  46.                         break;
  47.                 }
  48.                 i = fwrite(out, 1, have, dest);
  49.  
  50.                 total = total - have;
  51.                 have1 = (total - CHUNK);
  52.  
  53.                 if(have1> CHUNK)
  54.                         have = CHUNK;
  55.                 else
  56.                         have = have1;
  57.  
  58.             }
  59.                 if ((err == Z_OK) || (err == Z_STREAM_END)) {
  60.                         printf("value of tota32 is %d\n",total);
  61.                         err = inflateEnd(&strm);
  62.                 }
  63.         }
  64.  
  65.                 printf("value of total2 is %d\n",total);
  66.  
  67.                 return err;
  68. }

Need some guidance on using the inflate function.

]]> By: Asrar Ahmed http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-328166 Asrar Ahmed Mon, 28 Jun 2010 22:36:18 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-328166 This is very usefull zip ocx like ever This is very usefull zip ocx like ever

]]> By: Howard Winslow http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-324067 Howard Winslow Mon, 22 Mar 2010 22:03:12 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-324067 @Stephen Howe From the zlib FAQ: Well that's nice, but how do I make a gzip file in memory? Well that's nice, but how do I make a gzip file in memory? You can request that deflate write the gzip format instead of the zlib format using deflateInit2(). You can also request that inflate decode the gzip format using inflateInit2(). Read zlib.h for more details. http://zlib.net/zlib_faq.html#faq20 According to zlib.h: windowBits can also be greater than 15 for optional gzip decoding. Add 32 to windowBits to enable zlib and gzip decoding with automatic header detection, or add 16 to decode only the gzip format (the zlib format will return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is a crc32 instead of an adler32. @Stephen Howe

From the zlib FAQ:

Well that's nice, but how do I make a gzip file in memory?

Well that's nice, but how do I make a gzip file in memory?
You can request that deflate write the gzip format instead of the zlib format using deflateInit2(). You can also request that inflate decode the gzip format using inflateInit2(). Read zlib.h for more details.

http://zlib.net/zlib_faq.html#faq20

According to zlib.h:

windowBits can also be greater than 15 for optional gzip decoding. Add 32 to windowBits to enable zlib and gzip decoding with automatic header detection, or add 16 to decode only the gzip format (the zlib format will return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is a crc32 instead of an adler32.

]]> By: Mark Nelson http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-323567 Mark Nelson Fri, 05 Mar 2010 12:27:05 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-323567 @Zuffi: Not without some changes. It compresses files right now. @Zuffi:

Not without some changes. It compresses files right now.

]]> By: Zuffi http://marknelson.us/1997/01/01/zlib-engine/comment-page-1/#comment-323566 Zuffi Fri, 05 Mar 2010 12:25:52 +0000 /1997/01/01/zlib-looking-the-gift-code-in-the-mouth/#comment-323566 Hi All, If it possible for me to use this ocx to perform a compression of byte array in vb? Thanks and Best Regards, Boon Hui Hi All,

If it possible for me to use this ocx to perform a compression of byte array in vb?

Thanks and Best Regards,
Boon Hui

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