use one 'store' method to rule all (de)compressors

Adding a new compressor method meant adding a new method as well – even
if that boilt down to just linking to our generalized decompressor with
a new name. That is unneeded busywork if we can instead just call the
generalized decompressor and let it figure out which compressor to use
based on the filenames rather than by program name.

For compatibility we ship still 'gzip', 'bzip2' and co, but they are
just links to our "new" 'store' method.

1 files changed, 22 insertions, 15 deletions

diff --git a/apt-pkg/acquire-item.cc b/apt-pkg/acquire-item.cc
index ffe5bd1c4..6b0debb44 100644
--- a/apt-pkg/acquire-item.cc
+++ b/apt-pkg/acquire-item.cc
@@ -422,7 +422,7 @@ bool pkgAcqIndex::TransactionState(TransactionStates const state)
 	 {
 	    // keep the compressed file, but drop the decompressed
 	    EraseFileName.clear();
-	    if (PartialFile.empty() == false && flExtension(PartialFile) == "decomp")
+	    if (PartialFile.empty() == false && flExtension(PartialFile) != CurrentCompressionExtension)
 	       RemoveFile("TransactionAbort", PartialFile);
 	 }
 	 break;
@@ -2681,7 +2681,8 @@ void pkgAcqIndex::StageDownloadDone(string const &Message, HashStringList const
    {
       Stage = STAGE_DECOMPRESS_AND_VERIFY;
       Local = true;
-      DestFile += ".decomp";
+      if (CurrentCompressionExtension != "uncompressed")
+	 DestFile.erase(DestFile.length() - (CurrentCompressionExtension.length() + 1));
       Desc.URI = "copy:" + FileName;
       QueueURI(Desc);
       SetActiveSubprocess("copy");
@@ -2703,6 +2704,18 @@ void pkgAcqIndex::StageDownloadDone(string const &Message, HashStringList const
 	 SetActiveSubprocess("copy");
 	 return;
       }
+      else
+      {
+	 // symlinking ensures that the filename can be used for compression detection
+	 // that is e.g. needed for by-hash over file
+	 if (symlink(FileName.c_str(),DestFile.c_str()) != 0)
+	    _error->WarningE("pkgAcqIndex::StageDownloadDone", "Symlinking file %s to %s failed", FileName.c_str(), DestFile.c_str());
+	 else
+	 {
+	    EraseFileName = DestFile;
+	    FileName = DestFile;
+	 }
+      }
    }
    else
       EraseFileName = FileName;
@@ -2717,25 +2730,19 @@ void pkgAcqIndex::StageDownloadDone(string const &Message, HashStringList const
       return;
    }
 
-   // get the binary name for your used compression type
-   string decompProg;
-   if(CurrentCompressionExtension == "uncompressed")
-      decompProg = "copy";
-   else
-      decompProg = _config->Find(string("Acquire::CompressionTypes::").append(CurrentCompressionExtension),"");
-   if(decompProg.empty() == true)
-   {
-      _error->Error("Unsupported extension: %s", CurrentCompressionExtension.c_str());
-      return;
-   }
-
+   string decompProg = "store";
    if (Target.KeepCompressed == true)
    {
       DestFile = "/dev/null";
       EraseFileName.clear();
    }
    else
-      DestFile += ".decomp";
+   {
+      if (CurrentCompressionExtension == "uncompressed")
+	 decompProg = "copy";
+      else
+	 DestFile.erase(DestFile.length() - (CurrentCompressionExtension.length() + 1));
+   }
 
    // queue uri for the next stage
    Stage = STAGE_DECOMPRESS_AND_VERIFY;