use pkgTagFile to parse "header" of Release files

The handwritten parsing here was mostly done as we couldn't trust the
Release file we got, but nowadays we are sure that the Release file is
valid and contains just a single section we want it to include.

Beside reducing code it also fixes a bug: Fieldnames in deb822 formatted
files are case-insensitive and pkgTagFile does it correctly, but this
selfbuilt stuff here didn't.

apt-pkg/deb/deblistparser.cc

@@ -805,94 +805,28 @@ bool debListParser::LoadReleaseInfo(pkgCache::PkgFileIterator &FileI,
    map_ptrloc const storage = WriteUniqString(component);
    FileI->Component = storage;
 
-   // FIXME: should use FileFd and TagSection
-   FILE* release = fdopen(dup(File.Fd()), "r");
-   if (release == NULL)
+   pkgTagFile TagFile(&File);
+   pkgTagSection Section;
+   if (_error->PendingError() == true || TagFile.Step(Section) == false)
       return false;
 
-   char buffer[101];
-   while (fgets(buffer, sizeof(buffer), release) != NULL)
-   {
-      size_t len = 0;
-
-      // Skip empty lines
-      for (; buffer[len] == '\r' && buffer[len] == '\n'; ++len)
-         /* nothing */
-         ;
-      if (buffer[len] == '\0')
-	 continue;
-
-      // seperate the tag from the data
-      const char* dataStart = strchr(buffer + len, ':');
-      if (dataStart == NULL)
-	 continue;
-      len = dataStart - buffer;
-      for (++dataStart; *dataStart == ' '; ++dataStart)
-         /* nothing */
-         ;
-      const char* dataEnd = (const char*)rawmemchr(dataStart, '\0');
-      // The last char should be a newline, but we can never be sure: #633350
-      const char* lineEnd = dataEnd;
-      for (--lineEnd; *lineEnd == '\r' || *lineEnd == '\n'; --lineEnd)
-         /* nothing */
-         ;
-      ++lineEnd;
-
-      // which datastorage need to be updated
-      enum { Suite, Component, Version, Origin, Codename, Label, None } writeTo = None;
-      if (buffer[0] == ' ')
-	 ;
-      #define APT_PARSER_WRITETO(X) else if (strncmp(#X, buffer, len) == 0) writeTo = X;
-      APT_PARSER_WRITETO(Suite)
-      APT_PARSER_WRITETO(Component)
-      APT_PARSER_WRITETO(Version)
-      APT_PARSER_WRITETO(Origin)
-      APT_PARSER_WRITETO(Codename)
-      APT_PARSER_WRITETO(Label)
-      #undef APT_PARSER_WRITETO
-      #define APT_PARSER_FLAGIT(X) else if (strncmp(#X, buffer, len) == 0) \
-	 pkgTagSection::FindFlag(FileI->Flags, pkgCache::Flag:: X, dataStart, lineEnd);
-      APT_PARSER_FLAGIT(NotAutomatic)
-      APT_PARSER_FLAGIT(ButAutomaticUpgrades)
-      #undef APT_PARSER_FLAGIT
-
-      // load all data from the line and save it
-      string data;
-      if (writeTo != None)
-	 data.append(dataStart, dataEnd);
-      if (sizeof(buffer) - 1 == (dataEnd - buffer))
-      {
-	 while (fgets(buffer, sizeof(buffer), release) != NULL)
-	 {
-	    if (writeTo != None)
-	       data.append(buffer);
-	    if (strlen(buffer) != sizeof(buffer) - 1)
-	       break;
-	 }
-      }
-      if (writeTo != None)
-      {
-	 // remove spaces and stuff from the end of the data line
-	 for (std::string::reverse_iterator s = data.rbegin();
-	      s != data.rend(); ++s)
-	 {
-	    if (*s != '\r' && *s != '\n' && *s != ' ')
-	       break;
-	    *s = '\0';
-	 }
-	 map_ptrloc const storage = WriteUniqString(data);
-	 switch (writeTo) {
-	 case Suite: FileI->Archive = storage; break;
-	 case Component: FileI->Component = storage; break;
-	 case Version: FileI->Version = storage; break;
-	 case Origin: FileI->Origin = storage; break;
-	 case Codename: FileI->Codename = storage; break;
-	 case Label: FileI->Label = storage; break;
-	 case None: break;
-	 }
-      }
+   std::string data;
+   #define APT_INRELEASE(TAG, STORE) \
+   data = Section.FindS(TAG); \
+   if (data.empty() == false) \
+   { \
+      map_ptrloc const storage = WriteUniqString(data); \
+      STORE = storage; \
    }
-   fclose(release);
+   APT_INRELEASE("Suite", FileI->Archive)
+   APT_INRELEASE("Component", FileI->Component)
+   APT_INRELEASE("Version", FileI->Version)
+   APT_INRELEASE("Origin", FileI->Origin)
+   APT_INRELEASE("Codename", FileI->Codename)
+   APT_INRELEASE("Label", FileI->Label)
+   #undef APT_INRELEASE
+   Section.FindFlag("NotAutomatic", FileI->Flags, pkgCache::Flag::NotAutomatic);
+   Section.FindFlag("ButAutomaticUpgrades", FileI->Flags, pkgCache::Flag::ButAutomaticUpgrades);
 
    return !_error->PendingError();
 }