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, 48 insertions, 15 deletions

diff --git a/apt-pkg/contrib/hashes.cc b/apt-pkg/contrib/hashes.cc
index 6e7080bc9..953465091 100644
--- a/apt-pkg/contrib/hashes.cc
+++ b/apt-pkg/contrib/hashes.cc
@@ -250,28 +250,34 @@ bool HashStringList::operator!=(HashStringList const &other) const
 class PrivateHashes {
 public:
    unsigned long long FileSize;
+   unsigned int CalcHashes;
 
-   PrivateHashes() : FileSize(0) {}
+   PrivateHashes(unsigned int const CalcHashes) : FileSize(0), CalcHashes(CalcHashes) {}
 };
 									/*}}}*/
 // Hashes::Add* - Add the contents of data or FD			/*{{{*/
-bool Hashes::Add(const unsigned char * const Data,unsigned long long const Size, unsigned int const Hashes)
+bool Hashes::Add(const unsigned char * const Data, unsigned long long const Size)
 {
    bool Res = true;
 APT_IGNORE_DEPRECATED_PUSH
-   if ((Hashes & MD5SUM) == MD5SUM)
+   if ((d->CalcHashes & MD5SUM) == MD5SUM)
       Res &= MD5.Add(Data, Size);
-   if ((Hashes & SHA1SUM) == SHA1SUM)
+   if ((d->CalcHashes & SHA1SUM) == SHA1SUM)
       Res &= SHA1.Add(Data, Size);
-   if ((Hashes & SHA256SUM) == SHA256SUM)
+   if ((d->CalcHashes & SHA256SUM) == SHA256SUM)
       Res &= SHA256.Add(Data, Size);
-   if ((Hashes & SHA512SUM) == SHA512SUM)
+   if ((d->CalcHashes & SHA512SUM) == SHA512SUM)
       Res &= SHA512.Add(Data, Size);
 APT_IGNORE_DEPRECATED_POP
    d->FileSize += Size;
    return Res;
 }
-bool Hashes::AddFD(int const Fd,unsigned long long Size, unsigned int const Hashes)
+bool Hashes::Add(const unsigned char * const Data, unsigned long long const Size, unsigned int const Hashes)
+{
+   d->CalcHashes = Hashes;
+   return Add(Data, Size);
+}
+bool Hashes::AddFD(int const Fd,unsigned long long Size)
 {
    unsigned char Buf[64*64];
    bool const ToEOF = (Size == UntilEOF);
@@ -285,12 +291,17 @@ bool Hashes::AddFD(int const Fd,unsigned long long Size, unsigned int const Hash
       if (ToEOF && Res == 0) // EOF
 	 break;
       Size -= Res;
-      if (Add(Buf, Res, Hashes) == false)
+      if (Add(Buf, Res) == false)
 	 return false;
    }
    return true;
 }
-bool Hashes::AddFD(FileFd &Fd,unsigned long long Size, unsigned int const Hashes)
+bool Hashes::AddFD(int const Fd,unsigned long long Size, unsigned int const Hashes)
+{
+   d->CalcHashes = Hashes;
+   return AddFD(Fd, Size);
+}
+bool Hashes::AddFD(FileFd &Fd,unsigned long long Size)
 {
    unsigned char Buf[64*64];
    bool const ToEOF = (Size == 0);
@@ -309,20 +320,29 @@ bool Hashes::AddFD(FileFd &Fd,unsigned long long Size, unsigned int const Hashes
       else if (a == 0) // EOF
 	 break;
       Size -= a;
-      if (Add(Buf, a, Hashes) == false)
+      if (Add(Buf, a) == false)
 	 return false;
    }
    return true;
 }
+bool Hashes::AddFD(FileFd &Fd,unsigned long long Size, unsigned int const Hashes)
+{
+   d->CalcHashes = Hashes;
+   return AddFD(Fd, Size);
+}
 									/*}}}*/
 HashStringList Hashes::GetHashStringList()
 {
    HashStringList hashes;
 APT_IGNORE_DEPRECATED_PUSH
-   hashes.push_back(HashString("MD5Sum", MD5.Result().Value()));
-   hashes.push_back(HashString("SHA1", SHA1.Result().Value()));
-   hashes.push_back(HashString("SHA256", SHA256.Result().Value()));
-   hashes.push_back(HashString("SHA512", SHA512.Result().Value()));
+   if ((d->CalcHashes & MD5SUM) == MD5SUM)
+      hashes.push_back(HashString("MD5Sum", MD5.Result().Value()));
+   if ((d->CalcHashes & SHA1SUM) == SHA1SUM)
+      hashes.push_back(HashString("SHA1", SHA1.Result().Value()));
+   if ((d->CalcHashes & SHA256SUM) == SHA256SUM)
+      hashes.push_back(HashString("SHA256", SHA256.Result().Value()));
+   if ((d->CalcHashes & SHA512SUM) == SHA512SUM)
+      hashes.push_back(HashString("SHA512", SHA512.Result().Value()));
 APT_IGNORE_DEPRECATED_POP
    std::string SizeStr;
    strprintf(SizeStr, "%llu", d->FileSize);
@@ -330,6 +350,19 @@ APT_IGNORE_DEPRECATED_POP
    return hashes;
 }
 APT_IGNORE_DEPRECATED_PUSH
-Hashes::Hashes() { d = new PrivateHashes(); }
+Hashes::Hashes() { d = new PrivateHashes(~0); }
+Hashes::Hashes(unsigned int const Hashes) { d = new PrivateHashes(Hashes); }
+Hashes::Hashes(HashStringList const &Hashes) {
+   unsigned int calcHashes = Hashes.usable() ? 0 : ~0;
+   if (Hashes.find("MD5Sum") != NULL)
+      calcHashes |= MD5SUM;
+   if (Hashes.find("SHA1") != NULL)
+      calcHashes |= SHA1SUM;
+   if (Hashes.find("SHA256") != NULL)
+      calcHashes |= SHA256SUM;
+   if (Hashes.find("SHA512") != NULL)
+      calcHashes |= SHA512SUM;
+   d = new PrivateHashes(calcHashes);
+}
 Hashes::~Hashes() { delete d; }
 APT_IGNORE_DEPRECATED_POP