implement generic config fallback for methods

The https method implemented for a long while now a hardcoded fallback
to the same options in http, which, while it works, is rather inflexible
if we want to allow the methods to use another name to change their
behavior slightly, like apt-transport-tor does to https – most of the
diff being s#https#tor#g which then fails to do the full circle
fallthrough tor -> https -> http for https sources. With this config
infrastructure this could be implemented now.

1 files changed, 67 insertions, 5 deletions

diff --git a/methods/aptmethod.h b/methods/aptmethod.h
index 0963ea21e..38f451708 100644
--- a/methods/aptmethod.h
+++ b/methods/aptmethod.h
@@ -5,8 +5,10 @@
 #include <apt-pkg/configuration.h>
 #include <apt-pkg/error.h>
 
+#include <algorithm>
 #include <locale>
 #include <string>
+#include <vector>
 
 #include <sys/time.h>
 #include <sys/types.h>
@@ -15,10 +17,15 @@
 
 #include <apti18n.h>
 
+static bool hasDoubleColon(std::string const &n)
+{
+   return n.find("::") != std::string::npos;
+}
+
 class aptMethod : public pkgAcqMethod
 {
 protected:
-   std::string Binary;
+   std::string const Binary;
 
 public:
    virtual bool Configuration(std::string Message) APT_OVERRIDE
@@ -34,7 +41,7 @@ public:
       return true;
    }
 
-   bool CalculateHashes(FetchItem const * const Itm, FetchResult &Res) const
+   bool CalculateHashes(FetchItem const * const Itm, FetchResult &Res) const APT_NONNULL(2)
    {
       Hashes Hash(Itm->ExpectedHashes);
       FileFd Fd;
@@ -52,7 +59,62 @@ public:
       va_end(args);
    }
 
-   bool TransferModificationTimes(char const * const From, char const * const To, time_t &LastModified)
+   std::vector<std::string> methodNames;
+   void setPostfixForMethodNames(char const * const postfix) APT_NONNULL(2)
+   {
+      methodNames.erase(std::remove_if(methodNames.begin(), methodNames.end(), hasDoubleColon), methodNames.end());
+      decltype(methodNames) toAdd;
+      for (auto && name: methodNames)
+	 toAdd.emplace_back(name + "::" + postfix);
+      std::move(toAdd.begin(), toAdd.end(), std::back_inserter(methodNames));
+   }
+   bool DebugEnabled() const
+   {
+      if (methodNames.empty())
+	 return false;
+      auto const sni = std::find_if_not(methodNames.crbegin(), methodNames.crend(), hasDoubleColon);
+      if (unlikely(sni == methodNames.crend()))
+	 return false;
+      auto const ln = methodNames[methodNames.size() - 1];
+      // worst case: all three are the same
+      std::string confln, confsn, confpn;
+      strprintf(confln, "Debug::Acquire::%s", ln.c_str());
+      strprintf(confsn, "Debug::Acquire::%s", sni->c_str());
+      auto const pni = sni->substr(0, sni->find('+'));
+      strprintf(confpn, "Debug::Acquire::%s", pni.c_str());
+      return _config->FindB(confln,_config->FindB(confsn, _config->FindB(confpn, false)));
+   }
+   std::string ConfigFind(char const * const postfix, std::string const &defValue) const APT_NONNULL(2)
+   {
+      for (auto && name: methodNames)
+      {
+	 std::string conf;
+	 strprintf(conf, "Acquire::%s::%s", name.c_str(), postfix);
+	 auto const value = _config->Find(conf);
+	 if (value.empty() == false)
+	    return value;
+      }
+      return defValue;
+   }
+   std::string ConfigFind(std::string const &postfix, std::string const &defValue) const
+   {
+      return ConfigFind(postfix.c_str(), defValue);
+   }
+   bool ConfigFindB(char const * const postfix, bool const defValue) const APT_NONNULL(2)
+   {
+      return StringToBool(ConfigFind(postfix, defValue ? "yes" : "no"), defValue);
+   }
+   int ConfigFindI(char const * const postfix, int const defValue) const APT_NONNULL(2)
+   {
+      char *End;
+      std::string const value = ConfigFind(postfix, "");
+      auto const Res = strtol(value.c_str(), &End, 0);
+      if (value.c_str() == End)
+	 return defValue;
+      return Res;
+   }
+
+   bool TransferModificationTimes(char const * const From, char const * const To, time_t &LastModified) APT_NONNULL(2, 3)
    {
       if (strcmp(To, "/dev/null") == 0)
 	 return true;
@@ -75,8 +137,8 @@ public:
       return true;
    }
 
-   aptMethod(char const * const Binary, char const * const Ver, unsigned long const Flags) :
-      pkgAcqMethod(Ver, Flags), Binary(Binary)
+   aptMethod(std::string &&Binary, char const * const Ver, unsigned long const Flags) APT_NONNULL(3) :
+      pkgAcqMethod(Ver, Flags), Binary(Binary), methodNames({Binary})
    {
       try {
 	 std::locale::global(std::locale(""));