calculate only expected hashes in methods

Methods get told which hashes are expected by the acquire system, which
means we can use this list to restrict what we calculate in the methods
as any extra we are calculating is wasted effort as we can't compare it
with anything anyway.

Adding support for a new hash algorithm is therefore 'free' now and if a
algorithm is no longer provided in a repository for a file, we
automatically stop calculating it.

In practice this results in a speed-up in Debian as we don't have SHA512
here (so far), so we practically stop calculating it.

1 files changed, 5 insertions, 5 deletions

diff --git a/methods/copy.cc b/methods/copy.cc
index f3cd84215..a8e289df5 100644
--- a/methods/copy.cc
+++ b/methods/copy.cc
@@ -28,16 +28,16 @@
 class CopyMethod : public pkgAcqMethod
 {
    virtual bool Fetch(FetchItem *Itm);
-   void CalculateHashes(FetchResult &Res);
+   void CalculateHashes(FetchItem const * const Itm, FetchResult &Res);
    
    public:
    
    CopyMethod() : pkgAcqMethod("1.0",SingleInstance | SendConfig) {};
 };
 
-void CopyMethod::CalculateHashes(FetchResult &Res)
+void CopyMethod::CalculateHashes(FetchItem const * const Itm, FetchResult &Res)
 {
-   Hashes Hash;
+   Hashes Hash(Itm->ExpectedHashes);
    FileFd::CompressMode CompressMode = FileFd::None;
    if (_config->FindB("Acquire::GzipIndexes", false) == true)
       CompressMode = FileFd::Extension;
@@ -71,7 +71,7 @@ bool CopyMethod::Fetch(FetchItem *Itm)
    // just calc the hashes if the source and destination are identical
    if (File == Itm->DestFile)
    {
-      CalculateHashes(Res);
+      CalculateHashes(Itm, Res);
       URIDone(Res);
       return true;
    }
@@ -104,7 +104,7 @@ bool CopyMethod::Fetch(FetchItem *Itm)
    if (utimes(Res.Filename.c_str(), times) != 0)
       return _error->Errno("utimes",_("Failed to set modification time"));
 
-   CalculateHashes(Res);
+   CalculateHashes(Itm, Res);
 
    URIDone(Res);
    return true;