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, 7 insertions, 7 deletions

diff --git a/methods/http.cc b/methods/http.cc
index 947002cc6..e4773b0e2 100644
--- a/methods/http.cc
+++ b/methods/http.cc
@@ -64,8 +64,8 @@ const unsigned int CircleBuf::BW_HZ=10;
 // CircleBuf::CircleBuf - Circular input buffer				/*{{{*/
 // ---------------------------------------------------------------------
 /* */
-CircleBuf::CircleBuf(unsigned long long Size) 
-   : Size(Size), Hash(0), TotalWriten(0)
+CircleBuf::CircleBuf(unsigned long long Size)
+   : Size(Size), Hash(NULL), TotalWriten(0)
 {
    Buf = new unsigned char[Size];
    Reset();
@@ -84,10 +84,10 @@ void CircleBuf::Reset()
    TotalWriten = 0;
    MaxGet = (unsigned long long)-1;
    OutQueue = string();
-   if (Hash != 0)
+   if (Hash != NULL)
    {
       delete Hash;
-      Hash = new Hashes;
+      Hash = NULL;
    }
 }
 									/*}}}*/
@@ -222,7 +222,7 @@ bool CircleBuf::Write(int Fd)
 
       TotalWriten += Res;
       
-      if (Hash != 0)
+      if (Hash != NULL)
 	 Hash->Add(Buf + (OutP%Size),Res);
       
       OutP += Res;
@@ -484,10 +484,10 @@ APT_PURE bool HttpServerState::IsOpen()					/*{{{*/
    return (ServerFd != -1);
 }
 									/*}}}*/
-bool HttpServerState::InitHashes(FileFd &File)				/*{{{*/
+bool HttpServerState::InitHashes(FileFd &File, HashStringList const &ExpectedHashes)/*{{{*/
 {
    delete In.Hash;
-   In.Hash = new Hashes;
+   In.Hash = new Hashes(ExpectedHashes);
 
    // Set the expected size and read file for the hashes
    File.Truncate(StartPos);