Archived:Getting trailer and header info from GZIP files using Symbian C++
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|keywords=RFile, EZGZipFile, TEZGZipHeader, TEZGZipTrailer, RFile::Open(),EZGZipFile::IsGzipFileL(), EZGZipFile::LocateAndReadTrailerL(), EZGZipFile::ReadHeaderL(),EZGZipFile::EFText,EZGZipFile::EFHcrc, EZGZipFile::EFExtra,EZGZipFile::EFName,EZGZipFile::EFComment | |keywords=RFile, EZGZipFile, TEZGZipHeader, TEZGZipTrailer, RFile::Open(),EZGZipFile::IsGzipFileL(), EZGZipFile::LocateAndReadTrailerL(), EZGZipFile::ReadHeaderL(),EZGZipFile::EFText,EZGZipFile::EFHcrc, EZGZipFile::EFExtra,EZGZipFile::EFName,EZGZipFile::EFComment | ||
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| + | |sourcecode= <!-- Link to example source code (e.g. [[Media:The Code Example ZIP.zip]]) --> | ||
| + | |installfile= <!-- Link to installation file (e.g. [[Media:The Installation File.sis]]) --> | ||
| + | |sdk=<!-- SDK(s) built and tested against (e.g. [http://linktosdkdownload/ Nokia Qt SDK 1.1]) --> | ||
| + | |devicecompatability=<!-- Compatible devices (e.g.: All* (must have GPS) ) --> | ||
| + | |signing=<!-- Empty or one of Self-Signed, DevCert, Manufacturer --> | ||
| + | |capabilities=<!-- Capabilities required (e.g. Location, NetworkServices. -->) | ||
| + | |author=[[User:Aknyman]] | ||
}} | }} | ||
Revision as of 11:25, 24 June 2011
Article Metadata
Tested with
Devices(s): Nokia N93
Compatibility
Platform(s): S60 3rd Edition, FP1
Platform Security
Capabilities: )
Article
Keywords: RFile, EZGZipFile, TEZGZipHeader, TEZGZipTrailer, RFile::Open(),EZGZipFile::IsGzipFileL(), EZGZipFile::LocateAndReadTrailerL(), EZGZipFile::ReadHeaderL(),EZGZipFile::EFText,EZGZipFile::EFHcrc, EZGZipFile::EFExtra,EZGZipFile::EFName,EZGZipFile::EFComment
Created: aknyman
(14 May 2008)
Last edited: hamishwillee
(24 Jun 2011)
Overview
This snippet shows how to get the trailer and the header info from GZIP files.
The trailer part of GZIP file should contain the following data:
- CRC32
- Input size (calculated from the original uncompressed data)
The actual GZIP header is defined to contain the following fields:
- Fixed value for ID1 = 31
- Fixed value for ID2 = 139
- Compression method (8 is the standard)
- Flags (0 = no flags are set)
- Modification time (time stamp in Unix format)
- Extra flags (maximum compression - fastest algorithm)
- Operating System
This snippet can be self-signed.
MMP file
The following libraries are required:
LIBRARY efsrv.lib
LIBRARY ezlib.lib
Header file
Source file
#include <ezgzip.h>
#include <f32file.h>
void GetGZipFileTrailerAndHeaderInfoL(RFs& aRfs, const TDesC& aFileName)
{
RFile file;
TEZGZipHeader header;
TEZGZipTrailer trailer;
if (!EZGZipFile::IsGzipFileL(aRfs,aFileName))
{
_LIT(KIsNotGZipFile,"File:%S is not in GZip format\n");
console->Printf(KIsNotGZipFile,&aFileName);
console->Getch();
User::Leave(KErrGeneral);
}
EZGZipFile::LocateAndReadTrailerL(aRfs, aFileName, trailer);
_LIT(KTrailer,"CRC32 = %d size = %d\n");
console->Printf(KTrailer,trailer.iCrc32,trailer.iSize);
User::LeaveIfError(file.Open(aRfs,aFileName,EFileStream | EFileRead | EFileShareAny));
EZGZipFile::ReadHeaderL(file, header);
_LIT(KFileId1,"ID1 = %d\n");
console->Printf(KFileId1,header.iId1);
_LIT(KFileId2,"ID2 = %d\n");
console->Printf(KFileId2,header.iId2);
_LIT(KCompressionMethod,"compression method = %d\n");
console->Printf(KCompressionMethod,header.iCompressionMethod);
_LIT(KFlags,"flags = %d\n");
console->Printf(KFlags,header.iFlags);
_LIT(KTimeStamp,"time stamp = %d\n");
console->Printf(KTimeStamp,header.iTime);
_LIT(KExtraFlags,"extra flags %d\n");
console->Printf(KExtraFlags,header.iExtraFlags);
_LIT(KOS,"OS %d\n");
console->Printf(KOS,header.iOs);
if (header.iFlags & EZGZipFile::EFText)
{
_LIT(KText,"text flag set\n");
console->Printf(KText);
}
if (header.iFlags & EZGZipFile::EFHcrc)
{
_LIT(KCrc16,"CRC16 = %d\n");
console->Printf(KCrc16,header.iCrc);
}
if (header.iFlags & EZGZipFile::EFExtra)
{
_LIT(KExtraLength,"extra length %d\n");
console->Printf(KExtraLength,header.iXlen);
HBufC *buf = HBufC::NewLC(header.iExtra->Length());
buf->Des().Copy(*header.iExtra);
console->Printf(*buf);
CleanupStack::PopAndDestroy(); //buf
}
if (header.iFlags & EZGZipFile::EFName)
{
_LIT(KFName,"fname: %S\n");
HBufC *buf = HBufC::NewLC(header.iFname->Length());
buf->Des().Copy(*header.iFname);
console->Printf(KFName,buf);
CleanupStack::PopAndDestroy(); //buf
}
if (header.iFlags & EZGZipFile::EFComment)
{
_LIT(KComment,"comment: %S\n");
HBufC *buf = HBufC::NewLC(header.iComment->Length());
buf->Des().Copy(*header.iComment);
console->Printf(KComment,buf);
CleanupStack::PopAndDestroy(); //buf
}
}
Postconditions
The trailer and header info from the given GZIP file is printed to the console.
See also
CS000949 - Compressing and decompressing GZIP files
The GZIP format is specified in http://www.faqs.org/rfcs/rfc1952.html.
