// -*- mode: cpp; mode: fold -*- // Description /*{{{*/ // $Id: extracttar.cc,v 1.8.2.1 2004/01/16 18:58:50 mdz Exp $ /* ###################################################################### Extract a Tar - Tar Extractor Some performance measurements showed that zlib performed quite poorly in comparision to a forked gzip process. This tar extractor makes use of the fact that dup'd file descriptors have the same seek pointer and that gzip will not read past the end of a compressed stream, even if there is more data. We use the dup property to track extraction progress and the gzip feature to just feed gzip a fd in the middle of an AR file. ##################################################################### */ /*}}}*/ // Include Files /*{{{*/ #include #include #include #include #include #include #include #include #include #include #include /*}}}*/ using namespace std; // The on disk header for a tar file. struct ExtractTar::TarHeader { char Name[100]; char Mode[8]; char UserID[8]; char GroupID[8]; char Size[12]; char MTime[12]; char Checksum[8]; char LinkFlag; char LinkName[100]; char MagicNumber[8]; char UserName[32]; char GroupName[32]; char Major[8]; char Minor[8]; }; // ExtractTar::ExtractTar - Constructor /*{{{*/ // --------------------------------------------------------------------- /* */ ExtractTar::ExtractTar(FileFd &Fd,unsigned long Max,string DecompressionProgram) : File(Fd), MaxInSize(Max), DecompressProg(DecompressionProgram) { GZPid = -1; InFd = -1; Eof = false; } /*}}}*/ // ExtractTar::ExtractTar - Destructor /*{{{*/ // --------------------------------------------------------------------- /* */ ExtractTar::~ExtractTar() { // Error close Done(true); } /*}}}*/ // ExtractTar::Done - Reap the gzip sub process /*{{{*/ // --------------------------------------------------------------------- /* If the force flag is given then error messages are suppressed - this means we hit the end of the tar file but there was still gzip data. */ bool ExtractTar::Done(bool Force) { InFd.Close(); if (GZPid <= 0) return true; /* If there is a pending error then we are cleaning up gzip and are not interested in it's failures */ if (_error->PendingError() == true) Force = true; // Make sure we clean it up! kill(GZPid,SIGINT); string confvar = string("dir::bin::") + DecompressProg; if (ExecWait(GZPid,_config->Find(confvar.c_str(),DecompressProg.c_str()).c_str(), Force) == false) { GZPid = -1; return Force; } GZPid = -1; return true; } /*}}}*/ // ExtractTar::StartGzip - Startup gzip /*{{{*/ // --------------------------------------------------------------------- /* This creates a gzip sub process that has its input as the file itself. If this tar file is embedded into something like an ar file then gzip will efficiently ignore the extra bits. */ bool ExtractTar::StartGzip() { int Pipes[2]; if (pipe(Pipes) != 0) return _error->Errno("pipe",_("Failed to create pipes")); // Fork off the process GZPid = ExecFork(); // Spawn the subprocess if (GZPid == 0) { // Setup the FDs dup2(Pipes[1],STDOUT_FILENO); dup2(File.Fd(),STDIN_FILENO); int Fd = open("/dev/null",O_RDWR); if (Fd == -1) _exit(101); dup2(Fd,STDERR_FILENO); close(Fd); SetCloseExec(STDOUT_FILENO,false); SetCloseExec(STDIN_FILENO,false); SetCloseExec(STDERR_FILENO,false); const char *Args[3]; string confvar = string("dir::bin::") + DecompressProg; string argv0 = _config->Find(confvar.c_str(),DecompressProg.c_str()); Args[0] = argv0.c_str(); Args[1] = "-d"; Args[2] = 0; execvp(Args[0],(char **)Args); cerr << _("Failed to exec gzip ") << Args[0] << endl; _exit(100); } // Fix up our FDs InFd.Fd(Pipes[0]); close(Pipes[1]); return true; } /*}}}*/ // ExtractTar::Go - Perform extraction /*{{{*/ // --------------------------------------------------------------------- /* This reads each 512 byte block from the archive and extracts the header information into the Item structure. Then it resolves the UID/GID and invokes the correct processing function. */ bool ExtractTar::Go(pkgDirStream &Stream) { if (StartGzip() == false) return false; // Loop over all blocks string LastLongLink; string LastLongName; while (1) { bool BadRecord = false; unsigned char Block[512]; if (InFd.Read(Block,sizeof(Block),true) == false) return false; if (InFd.Eof() == true) break; // Get the checksum TarHeader *Tar = (TarHeader *)Block; unsigned long CheckSum; if (StrToNum(Tar->Checksum,CheckSum,sizeof(Tar->Checksum),8) == false) return _error->Error(_("Corrupted archive")); /* Compute the checksum field. The actual checksum is blanked out with spaces so it is not included in the computation */ unsigned long NewSum = 0; memset(Tar->Checksum,' ',sizeof(Tar->Checksum)); for (int I = 0; I != sizeof(Block); I++) NewSum += Block[I]; /* Check for a block of nulls - in this case we kill gzip, GNU tar does this.. */ if (NewSum == ' '*sizeof(Tar->Checksum)) return Done(true); if (NewSum != CheckSum) return _error->Error(_("Tar checksum failed, archive corrupted")); // Decode all of the fields pkgDirStream::Item Itm; if (StrToNum(Tar->Mode,Itm.Mode,sizeof(Tar->Mode),8) == false || StrToNum(Tar->UserID,Itm.UID,sizeof(Tar->UserID),8) == false || StrToNum(Tar->GroupID,Itm.GID,sizeof(Tar->GroupID),8) == false || StrToNum(Tar->Size,Itm.Size,sizeof(Tar->Size),8) == false || StrToNum(Tar->MTime,Itm.MTime,sizeof(Tar->MTime),8) == false || StrToNum(Tar->Major,Itm.Major,sizeof(Tar->Major),8) == false || StrToNum(Tar->Minor,Itm.Minor,sizeof(Tar->Minor),8) == false) return _error->Error(_("Corrupted archive")); // Grab the filename if (LastLongName.empty() == false) Itm.Name = (char *)LastLongName.c_str(); else { Tar->Name[sizeof(Tar->Name)] = 0; Itm.Name = Tar->Name; } if (Itm.Name[0] == '.' && Itm.Name[1] == '/' && Itm.Name[2] != 0) Itm.Name += 2; // Grab the link target Tar->Name[sizeof(Tar->LinkName)] = 0; Itm.LinkTarget = Tar->LinkName; if (LastLongLink.empty() == false) Itm.LinkTarget = (char *)LastLongLink.c_str(); // Convert the type over switch (Tar->LinkFlag) { case NormalFile0: case NormalFile: Itm.Type = pkgDirStream::Item::File; break; case HardLink: Itm.Type = pkgDirStream::Item::HardLink; break; case SymbolicLink: Itm.Type = pkgDirStream::Item::SymbolicLink; break; case CharacterDevice: Itm.Type = pkgDirStream::Item::CharDevice; break; case BlockDevice: Itm.Type = pkgDirStream::Item::BlockDevice; break; case Directory: Itm.Type = pkgDirStream::Item::Directory; break; case FIFO: Itm.Type = pkgDirStream::Item::FIFO; break; case GNU_LongLink: { unsigned long Length = Itm.Size; unsigned char Block[512]; while (Length > 0) { if (InFd.Read(Block,sizeof(Block),true) == false) return false; if (Length <= sizeof(Block)) { LastLongLink.append(Block,Block+sizeof(Block)); break; } LastLongLink.append(Block,Block+sizeof(Block)); Length -= sizeof(Block); } continue; } case GNU_LongName: { unsigned long Length = Itm.Size; unsigned char Block[512]; while (Length > 0) { if (InFd.Read(Block,sizeof(Block),true) == false) return false; if (Length < sizeof(Block)) { LastLongName.append(Block,Block+sizeof(Block)); break; } LastLongName.append(Block,Block+sizeof(Block)); Length -= sizeof(Block); } continue; } default: BadRecord = true; _error->Warning(_("Unknown TAR header type %u, member %s"),(unsigned)Tar->LinkFlag,Tar->Name); break; } int Fd = -1; if (BadRecord == false) if (Stream.DoItem(Itm,Fd) == false) return false; // Copy the file over the FD unsigned long Size = Itm.Size; while (Size != 0) { unsigned char Junk[32*1024]; unsigned long Read = min(Size,(unsigned long)sizeof(Junk)); if (InFd.Read(Junk,((Read+511)/512)*512) == false) return false; if (BadRecord == false) { if (Fd > 0) { if (write(Fd,Junk,Read) != (signed)Read) return Stream.Fail(Itm,Fd); } else { /* An Fd of -2 means to send to a special processing function */ if (Fd == -2) if (Stream.Process(Itm,Junk,Read,Itm.Size - Size) == false) return Stream.Fail(Itm,Fd); } } Size -= Read; } // And finish up if (Itm.Size >= 0 && BadRecord == false) if (Stream.FinishedFile(Itm,Fd) == false) return false; LastLongName.erase(); LastLongLink.erase(); } return Done(false); } /*}}}*/