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.

2 files changed, 65 insertions, 19 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
diff --git a/apt-pkg/contrib/hashes.h b/apt-pkg/contrib/hashes.h
index 154862457..ac13c8ace 100644
--- a/apt-pkg/contrib/hashes.h
+++ b/apt-pkg/contrib/hashes.h
@@ -178,7 +178,8 @@ class Hashes
 
    static const int UntilEOF = 0;
 
-   bool Add(const unsigned char * const Data, unsigned long long const Size, unsigned int const Hashes = ~0);
+   bool Add(const unsigned char * const Data, unsigned long long const Size);
+   APT_DEPRECATED bool Add(const unsigned char * const Data, unsigned long long const Size, unsigned int const Hashes);
    inline bool Add(const char * const Data)
    {return Add((unsigned char const * const)Data,strlen(Data));};
    inline bool Add(const unsigned char * const Beg,const unsigned char * const End)
@@ -186,13 +187,24 @@ class Hashes
 
    enum SupportedHashes { MD5SUM = (1 << 0), SHA1SUM = (1 << 1), SHA256SUM = (1 << 2),
       SHA512SUM = (1 << 3) };
-   bool AddFD(int const Fd,unsigned long long Size = 0, unsigned int const Hashes = ~0);
-   bool AddFD(FileFd &Fd,unsigned long long Size = 0, unsigned int const Hashes = ~0);
+   bool AddFD(int const Fd,unsigned long long Size = 0);
+   APT_DEPRECATED bool AddFD(int const Fd,unsigned long long Size, unsigned int const Hashes);
+   bool AddFD(FileFd &Fd,unsigned long long Size = 0);
+   APT_DEPRECATED bool AddFD(FileFd &Fd,unsigned long long Size, unsigned int const Hashes);
 
    HashStringList GetHashStringList();
 
 APT_IGNORE_DEPRECATED_PUSH
+   /** create a Hashes object to calculate all supported hashes
+    *
+    * If ALL is too much, you can limit which Hashes are calculated
+    * with the following other constructors which mention explicitly
+    * which hashes to generate. */
    Hashes();
+   /** @param Hashes bitflag composed of #SupportedHashes */
+   Hashes(unsigned int const Hashes);
+   /** @param Hashes is a list of hashes */
+   Hashes(HashStringList const &Hashes);
    virtual ~Hashes();
 APT_IGNORE_DEPRECATED_POP
 
@@ -208,15 +220,16 @@ APT_IGNORE_DEPRECATED_POP
    }
 
    public:
+APT_IGNORE_DEPRECATED_PUSH
    APT_DEPRECATED bool AddFD(int const Fd, unsigned long long Size, bool const addMD5,
 	 bool const addSHA1, bool const addSHA256, bool const addSHA512) {
       return AddFD(Fd, Size, boolsToFlag(addMD5, addSHA1, addSHA256, addSHA512));
    };
-
    APT_DEPRECATED bool AddFD(FileFd &Fd, unsigned long long Size, bool const addMD5,
 	 bool const addSHA1, bool const addSHA256, bool const addSHA512) {
       return AddFD(Fd, Size, boolsToFlag(addMD5, addSHA1, addSHA256, addSHA512));
    };
+APT_IGNORE_DEPRECATED_POP
 };
 
 #endif