Support for Portage's flat_hash cache format. Fixes: ticket:630

Use flat_hash for the write_cache, and drop flat_list support for
non-Gentoo EAPIs.

15 files changed, 751 insertions, 423 deletions

diff --git a/paludis/repositories/e/eapi.cc b/paludis/repositories/e/eapi.cc
index 44103df..b77af58 100644
--- a/paludis/repositories/e/eapi.cc
+++ b/paludis/repositories/e/eapi.cc
@@ -88,7 +88,7 @@ namespace
     {
         return make_named_values<EAPIMetadataVariable>(
                 value_for<n::description>(check_get(k, "description_" + s)),
-                value_for<n::flat_cache_index>(destringify_key<int>(k, "flat_cache_" + s)),
+                value_for<n::flat_list_index>(destringify_key<int>(k, "flat_list_" + s)),
                 value_for<n::name>(check_get(k, "metadata_" + s))
                 );
     }
@@ -106,7 +106,7 @@ namespace
             value_for<n::keywords>(make_metadata_variable(k, "keywords")),
             value_for<n::license>(make_metadata_variable(k, "license")),
             value_for<n::long_description>(make_metadata_variable(k, "long_description")),
-            value_for<n::minimum_flat_cache_size>(destringify_key<int>(k, "flat_cache_minimum_size")),
+            value_for<n::minimum_flat_list_size>(destringify_key<int>(k, "flat_list_minimum_size")),
             value_for<n::pdepend>(make_metadata_variable(k, "pdepend")),
             value_for<n::provide>(make_metadata_variable(k, "provide")),
             value_for<n::remote_ids>(make_metadata_variable(k, "remote_ids")),
diff --git a/paludis/repositories/e/eapi.hh b/paludis/repositories/e/eapi.hh
index e40382b..e26d444 100644
--- a/paludis/repositories/e/eapi.hh
+++ b/paludis/repositories/e/eapi.hh
@@ -82,7 +82,7 @@ namespace paludis
         struct exported_name;
         struct f_function_prefix;
         struct failure_is_fatal;
-        struct flat_cache_index;
+        struct flat_list_index;
         struct homepage;
         struct ignore_pivot_env_functions;
         struct ignore_pivot_env_variables;
@@ -95,7 +95,7 @@ namespace paludis
         struct long_description;
         struct merger_options;
         struct metadata_key;
-        struct minimum_flat_cache_size;
+        struct minimum_flat_list_size;
         struct must_not_change_variables;
         struct name;
         struct no_slot_or_repo;
@@ -237,7 +237,7 @@ namespace paludis
         struct EAPIMetadataVariable
         {
             NamedValue<n::description, std::string> description;
-            NamedValue<n::flat_cache_index, int> flat_cache_index;
+            NamedValue<n::flat_list_index, int> flat_list_index;
             NamedValue<n::name, std::string> name;
         };
 
@@ -253,7 +253,7 @@ namespace paludis
             NamedValue<n::keywords, EAPIMetadataVariable> keywords;
             NamedValue<n::license, EAPIMetadataVariable> license;
             NamedValue<n::long_description, EAPIMetadataVariable> long_description;
-            NamedValue<n::minimum_flat_cache_size, int> minimum_flat_cache_size;
+            NamedValue<n::minimum_flat_list_size, int> minimum_flat_list_size;
             NamedValue<n::pdepend, EAPIMetadataVariable> pdepend;
             NamedValue<n::provide, EAPIMetadataVariable> provide;
             NamedValue<n::remote_ids, EAPIMetadataVariable> remote_ids;
diff --git a/paludis/repositories/e/eapis/0.conf b/paludis/repositories/e/eapis/0.conf
index 97d3898..0440cc4 100644
--- a/paludis/repositories/e/eapis/0.conf
+++ b/paludis/repositories/e/eapis/0.conf
@@ -174,29 +174,29 @@ metadata_src_uri = SRC_URI
 metadata_use =
 metadata_dependencies =
 
-flat_cache_minimum_size = 15
-flat_cache_build_depend = 0
-flat_cache_short_description = 7
-flat_cache_long_description = -1
-flat_cache_eapi = 14
-flat_cache_dependencies = -1
-flat_cache_homepage = 5
-flat_cache_inherited = 9
-flat_cache_iuse = 10
-flat_cache_keywords = 8
-flat_cache_license = 6
-flat_cache_pdepend = 12
-flat_cache_provide = 13
-flat_cache_restrict = 4
-flat_cache_run_depend = 1
-flat_cache_slot = 2
-flat_cache_src_uri = 3
-flat_cache_use = -1
-flat_cache_bugs_to = -1
-flat_cache_remote_ids = -1
-flat_cache_upstream_changelog = -1
-flat_cache_upstream_release_notes = -1
-flat_cache_upstream_documentation = -1
+flat_list_minimum_size = 15
+flat_list_build_depend = 0
+flat_list_short_description = 7
+flat_list_long_description = -1
+flat_list_eapi = 14
+flat_list_dependencies = -1
+flat_list_homepage = 5
+flat_list_inherited = 9
+flat_list_iuse = 10
+flat_list_keywords = 8
+flat_list_license = 6
+flat_list_pdepend = 12
+flat_list_provide = 13
+flat_list_restrict = 4
+flat_list_run_depend = 1
+flat_list_slot = 2
+flat_list_src_uri = 3
+flat_list_use = -1
+flat_list_bugs_to = -1
+flat_list_remote_ids = -1
+flat_list_upstream_changelog = -1
+flat_list_upstream_release_notes = -1
+flat_list_upstream_documentation = -1
 
 env_use = USE
 env_use_expand = USE_EXPAND
diff --git a/paludis/repositories/e/eapis/exheres-0.conf b/paludis/repositories/e/eapis/exheres-0.conf
index cc2feca..d3639bb 100644
--- a/paludis/repositories/e/eapis/exheres-0.conf
+++ b/paludis/repositories/e/eapis/exheres-0.conf
@@ -193,29 +193,29 @@ description_upstream_changelog = Upstream changelog
 description_upstream_release_notes = Upstream release notes
 description_upstream_documentation = Upstream documentation
 
-flat_cache_minimum_size = 18
-flat_cache_build_depend = -1
-flat_cache_short_description = 7
-flat_cache_long_description = 11
-flat_cache_eapi = 14
-flat_cache_dependencies = 1
-flat_cache_homepage = 5
-flat_cache_inherited = 9
-flat_cache_iuse = 10
-flat_cache_keywords = 8
-flat_cache_license = 6
-flat_cache_pdepend = -1
-flat_cache_provide = -1
-flat_cache_restrict = 4
-flat_cache_run_depend = -1
-flat_cache_slot = 2
-flat_cache_src_uri = 3
-flat_cache_use = -1
-flat_cache_bugs_to = 12
-flat_cache_remote_ids = 13
-flat_cache_upstream_changelog = 15
-flat_cache_upstream_release_notes = 16
-flat_cache_upstream_documentation = 17
+flat_list_minimum_size = -1
+flat_list_build_depend = -1
+flat_list_short_description = -1
+flat_list_long_description = -1
+flat_list_eapi = -1
+flat_list_dependencies = -1
+flat_list_homepage = -1
+flat_list_inherited = -1
+flat_list_iuse = -1
+flat_list_keywords = -1
+flat_list_license = -1
+flat_list_pdepend = -1
+flat_list_provide = -1
+flat_list_restrict = -1
+flat_list_run_depend = -1
+flat_list_slot = -1
+flat_list_src_uri = -1
+flat_list_use = -1
+flat_list_bugs_to = -1
+flat_list_remote_ids = -1
+flat_list_upstream_changelog = -1
+flat_list_upstream_release_notes = -1
+flat_list_upstream_documentation = -1
 
 env_use = OPTIONS
 env_use_expand = SUBOPTIONS
diff --git a/paludis/repositories/e/eapis/kdebuild-1.conf b/paludis/repositories/e/eapis/kdebuild-1.conf
index f191379..fe4d0fe 100644
--- a/paludis/repositories/e/eapis/kdebuild-1.conf
+++ b/paludis/repositories/e/eapis/kdebuild-1.conf
@@ -20,7 +20,8 @@ ebuild_must_not_set_variables = ${ebuild_must_not_set_variables} PROVIDE
 must_not_change_variables = ${must_not_change_variables} EAPI
 description_provide =
 metadata_provide =
-flat_cache_provide = -1
+
+flat_list_minimum_size = -1
 
 ebuild_install = \
     : killold ; \
diff --git a/paludis/repositories/e/eapis/paludis-1.conf b/paludis/repositories/e/eapis/paludis-1.conf
index 799d2bc..28a6099 100644
--- a/paludis/repositories/e/eapis/paludis-1.conf
+++ b/paludis/repositories/e/eapis/paludis-1.conf
@@ -179,30 +179,30 @@ description_src_uri = Source URI
 description_use = Selected USE flags
 description_dependencies =
 
-flat_cache_minimum_size = 15
-flat_cache_build_depend = 0
-flat_cache_short_description = 7
-flat_cache_long_description = -1
-flat_cache_eapi = 14
-flat_cache_dependencies = -1
-flat_cache_homepage = 5
-flat_cache_inherited = 9
-flat_cache_iuse = 10
-flat_cache_keywords = 8
-flat_cache_license = 6
-flat_cache_pdepend = 12
-flat_cache_provide = 13
-flat_cache_restrict = 4
-flat_cache_run_depend = 1
-flat_cache_slot = 2
-flat_cache_src_uri = 3
-flat_cache_use = -1
-flat_cache_use = -1
-flat_cache_bugs_to = -1
-flat_cache_remote_ids = -1
-flat_cache_upstream_changelog = -1
-flat_cache_upstream_release_notes = -1
-flat_cache_upstream_documentation = -1
+flat_list_minimum_size = -1
+flat_list_build_depend = -1
+flat_list_short_description = -1
+flat_list_long_description = -1
+flat_list_eapi = -1
+flat_list_dependencies = -1
+flat_list_homepage = -1
+flat_list_inherited = -1
+flat_list_iuse = -1
+flat_list_keywords = -1
+flat_list_license = -1
+flat_list_pdepend = -1
+flat_list_provide = -1
+flat_list_restrict = -1
+flat_list_run_depend = -1
+flat_list_slot = -1
+flat_list_src_uri = -1
+flat_list_use = -1
+flat_list_use = -1
+flat_list_bugs_to = -1
+flat_list_remote_ids = -1
+flat_list_upstream_changelog = -1
+flat_list_upstream_release_notes = -1
+flat_list_upstream_documentation = -1
 
 env_use = USE
 env_use_expand = USE_EXPAND
diff --git a/paludis/repositories/e/eapis/pbin-1+0.conf b/paludis/repositories/e/eapis/pbin-1+0.conf
index accc132..fa035b6 100644
--- a/paludis/repositories/e/eapis/pbin-1+0.conf
+++ b/paludis/repositories/e/eapis/pbin-1+0.conf
@@ -36,6 +36,5 @@ metadata_keywords = BINARY_KEYWORDS
 metadata_src_uri = BINARY_URI
 metadata_use = USE
 
-flat_cache_minimum_size = 16
-flat_cache_use = 15
+flat_list_minimum_size = -1
 
diff --git a/paludis/repositories/e/eapis/pbin-1+1.conf b/paludis/repositories/e/eapis/pbin-1+1.conf
index 9864980..529a6e7 100644
--- a/paludis/repositories/e/eapis/pbin-1+1.conf
+++ b/paludis/repositories/e/eapis/pbin-1+1.conf
@@ -36,6 +36,5 @@ metadata_keywords = BINARY_KEYWORDS
 metadata_src_uri = BINARY_URI
 metadata_use = USE
 
-flat_cache_minimum_size = 16
-flat_cache_use = 15
+flat_list_minimum_size = -1
 
diff --git a/paludis/repositories/e/eapis/pbin-1+exheres-0.conf b/paludis/repositories/e/eapis/pbin-1+exheres-0.conf
index 60e0616..99272bb 100644
--- a/paludis/repositories/e/eapis/pbin-1+exheres-0.conf
+++ b/paludis/repositories/e/eapis/pbin-1+exheres-0.conf
@@ -36,5 +36,5 @@ metadata_keywords = BINARY_PLATFORMS
 metadata_src_uri = BINARY_URI
 metadata_use = OPTIONS
 
-flat_cache_use = 12
+flat_list_minimum_size = -1
 
diff --git a/paludis/repositories/e/eapis/pbin-1+paludis-1.conf b/paludis/repositories/e/eapis/pbin-1+paludis-1.conf
index 8b7335f..7e87c47 100644
--- a/paludis/repositories/e/eapis/pbin-1+paludis-1.conf
+++ b/paludis/repositories/e/eapis/pbin-1+paludis-1.conf
@@ -36,6 +36,5 @@ metadata_keywords = BINARY_KEYWORDS
 metadata_src_uri = BINARY_URI
 metadata_use = USE
 
-flat_cache_minimum_size = 16
-flat_cache_use = 15
+flat_list_minimum_size = -1
 
diff --git a/paludis/repositories/e/ebuild_entries.cc b/paludis/repositories/e/ebuild_entries.cc
index e8f9db6..82616f4 100644
--- a/paludis/repositories/e/ebuild_entries.cc
+++ b/paludis/repositories/e/ebuild_entries.cc
@@ -124,7 +124,7 @@ namespace paludis
             environment(e),
             e_repository(p),
             params(k),
-            eclass_mtimes(new EclassMtimes(k.eclassdirs)),
+            eclass_mtimes(new EclassMtimes(p, k.eclassdirs)),
             master_mtime(0)
         {
             FSEntry m(k.location / "metadata" / "timestamp");
diff --git a/paludis/repositories/e/ebuild_flat_metadata_cache.cc b/paludis/repositories/e/ebuild_flat_metadata_cache.cc
index 0ad3366..4d570ed 100644
--- a/paludis/repositories/e/ebuild_flat_metadata_cache.cc
+++ b/paludis/repositories/e/ebuild_flat_metadata_cache.cc
@@ -2,6 +2,7 @@
 
 /*
  * Copyright (c) 2006, 2007, 2008 Ciaran McCreesh
+ * Copyright (c) 2008 David Leverton
  *
  * This file is part of the Paludis package manager. Paludis is free software;
  * you can redistribute it and/or modify it under the terms of the GNU General
@@ -23,6 +24,7 @@
 #include <paludis/util/join.hh>
 #include <paludis/util/visitor-impl.hh>
 #include <paludis/util/set.hh>
+#include <paludis/util/destringify.hh>
 #include <paludis/repositories/e/dep_spec_pretty_printer.hh>
 #include <paludis/repositories/e/dep_parser.hh>
 #include <paludis/repositories/e/dependencies_rewriter.hh>
@@ -31,6 +33,7 @@
 #include <tr1/functional>
 #include <fstream>
 #include <set>
+#include <map>
 #include <list>
 #include <vector>
 #include <functional>
@@ -41,14 +44,230 @@
 using namespace paludis;
 using namespace paludis::erepository;
 
+namespace paludis
+{
+    template <>
+    struct Implementation<EbuildFlatMetadataCache>
+    {
+        const Environment * const env;
+        const FSEntry & filename;
+        const FSEntry & ebuild;
+        time_t master_mtime;
+        std::tr1::shared_ptr<const EclassMtimes> eclass_mtimes;
+        bool silent;
+
+        Implementation(const Environment * const e, const FSEntry & f, const FSEntry & eb,
+                time_t m, const std::tr1::shared_ptr<const EclassMtimes> em, bool s) :
+            env(e),
+            filename(f),
+            ebuild(eb),
+            master_mtime(m),
+            eclass_mtimes(em),
+            silent(s)
+        {
+        }
+    };
+}
+
+namespace
+{
+    bool load_flat_list(
+        const std::tr1::shared_ptr<const EbuildID> & id, const std::vector<std::string> & lines, Implementation<EbuildFlatMetadataCache> * _imp)
+    {
+        Context ctx("When loading flat_list format cache file:");
+
+        if (lines.size() < 15)
+        {
+            Log::get_instance()->message("e.cache.flat_list.truncated", ll_warning, lc_no_context)
+                << "cache file has " << lines.size() << " lines, but expected at least 15";
+            return false;
+        }
+
+        id->set_eapi(lines[14]);
+
+        if (id->eapi()->supported())
+        {
+            const EAPIEbuildMetadataVariables & m(*id->eapi()->supported()->ebuild_metadata_variables());
+            if (-1 == m.minimum_flat_list_size())
+            {
+                Log::get_instance()->message("e.cache.flat_list.unsupported", ll_warning, lc_context)
+                    << "flat_list cache is not supported for EAPI '" << id->eapi()->name() << "'";
+                return false;
+            }
+
+            if (static_cast<int>(lines.size()) < m.minimum_flat_list_size())
+            {
+                Log::get_instance()->message("e.cache.flat_list.truncated", ll_warning, lc_context)
+                    << "cache file has " << lines.size() << " lines, but expected at least " << m.minimum_flat_list_size();
+                return false;
+            }
+
+            {
+                time_t cache_time(std::max(_imp->master_mtime, _imp->filename.mtime()));
+                bool ok(_imp->ebuild.mtime() <= cache_time);
+                if (! ok)
+                    Log::get_instance()->message("e.cache.flat_list.mtime", ll_debug, lc_context)
+                        << "ebuild has mtime " << _imp->ebuild.mtime() << ", but expected at most " << cache_time;
+
+                if (ok)
+                {
+                    std::set<std::string> tokens;
+                    tokenise_whitespace(lines[m.inherited().flat_list_index()], std::inserter(tokens, tokens.begin()));
+                    FSEntry eclassdir(id->repository()->location_key()->value() / "eclass");
+                    for (std::set<std::string>::const_iterator it(tokens.begin()),
+                             it_end(tokens.end()); it_end != it; ++it)
+                    {
+                        const FSEntry * eclass(_imp->eclass_mtimes->eclass(*it));
+                        if (! eclass)
+                        {
+                            Log::get_instance()->message("e.cache.flat_list.eclass.missing", ll_debug, lc_context)
+                                << "Can't find cache-requested eclass '" << *it << "'";
+                            ok = false;
+                        }
+
+                        else if (eclass->dirname() != eclassdir)
+                        {
+                            Log::get_instance()->message("e.cache.flat_list.eclass.wrong_location", ll_debug, lc_context)
+                                << "Cache-requested eclass '" << *it << "' was found at '"
+                                << eclass->dirname() << "', but expected '" << eclassdir << "'";
+                            ok = false;
+                        }
+
+                        else if (eclass->mtime() > cache_time)
+                        {
+                            Log::get_instance()->message("e.cache.flat_list.eclass.wrong_mtime", ll_debug, lc_context)
+                                << "Cache-requested eclass '" << *it << "' has mtime "
+                                << eclass->mtime() << ", but expected at most " << cache_time;
+                            ok = false;
+                        }
+
+                        if (! ok)
+                            break;
+                    }
+                }
+
+                if (! ok)
+                {
+                    Log::get_instance()->message("e.cache.stale", ll_warning, lc_no_context)
+                        << "Stale cache file at '" << _imp->filename << "'";
+                    return false;
+                }
+            }
+
+            if (-1 != m.dependencies().flat_list_index() && ! m.dependencies().name().empty())
+            {
+                DependenciesRewriter rewriter;
+                parse_depend(lines.at(m.dependencies().flat_list_index()), _imp->env, id, *id->eapi())->accept(rewriter);
+                id->load_build_depend(m.dependencies().name() + ".DEPEND", m.dependencies().description() + " (build)", rewriter.depend());
+                id->load_run_depend(m.dependencies().name() + ".RDEPEND", m.dependencies().description() + " (run)", rewriter.rdepend());
+                id->load_post_depend(m.dependencies().name() + ".PDEPEND", m.dependencies().description() + " (post)", rewriter.pdepend());
+            }
+
+            if (-1 != m.build_depend().flat_list_index() && ! m.build_depend().name().empty())
+                id->load_build_depend(m.build_depend().name(), m.build_depend().description(), lines.at(m.build_depend().flat_list_index()));
+
+            if (-1 != m.run_depend().flat_list_index() && ! m.run_depend().name().empty())
+                id->load_run_depend(m.run_depend().name(), m.run_depend().description(), lines.at(m.run_depend().flat_list_index()));
+
+            id->set_slot(SlotName(lines.at(m.slot().flat_list_index())));
+
+            if (-1 != m.src_uri().flat_list_index() && ! m.src_uri().name().empty())
+                id->load_src_uri(m.src_uri().name(), m.src_uri().description(), lines.at(m.src_uri().flat_list_index()));
+
+            if (-1 != m.restrictions().flat_list_index() && ! m.restrictions().name().empty())
+                id->load_restrict(m.restrictions().name(), m.restrictions().description(), lines.at(m.restrictions().flat_list_index()));
+
+            if (-1 != m.homepage().flat_list_index() && ! m.homepage().name().empty())
+                id->load_homepage(m.homepage().name(), m.homepage().description(), lines.at(m.homepage().flat_list_index()));
+
+            if (-1 != m.license().flat_list_index() && ! m.license().name().empty())
+                id->load_license(m.license().name(), m.license().description(), lines.at(m.license().flat_list_index()));
+
+            if (-1 != m.short_description().flat_list_index() && ! m.short_description().name().empty())
+                id->load_short_description(m.short_description().name(),
+                        m.short_description().description(),
+                        lines.at(m.short_description().flat_list_index()));
+
+            if (-1 != m.long_description().flat_list_index() && ! m.long_description().name().empty())
+            {
+                std::string value(lines.at(m.long_description().flat_list_index()));
+                if (! value.empty())
+                    id->load_long_description(m.long_description().name(),
+                            m.long_description().description(), value);
+            }
+
+            if (-1 != m.keywords().flat_list_index() && ! m.keywords().name().empty())
+                id->load_keywords(m.keywords().name(), m.keywords().description(), lines.at(m.keywords().flat_list_index()));
+
+            if (-1 != m.inherited().flat_list_index() && ! m.inherited().name().empty())
+                id->load_inherited(m.inherited().name(), m.inherited().description(), lines.at(m.inherited().flat_list_index()));
+
+            if (-1 != m.iuse().flat_list_index() && ! m.iuse().name().empty())
+                id->load_iuse(m.iuse().name(), m.iuse().description(), lines.at(m.iuse().flat_list_index()));
+
+            if (-1 != m.pdepend().flat_list_index() && ! m.pdepend().name().empty())
+                id->load_post_depend(m.pdepend().name(), m.pdepend().description(), lines.at(m.pdepend().flat_list_index()));
+
+            if (-1 != m.provide().flat_list_index() && ! m.provide().name().empty())
+                id->load_provide(m.provide().name(), m.provide().description(), lines.at(m.provide().flat_list_index()));
+
+            if (-1 != m.use().flat_list_index() && ! m.use().name().empty())
+                id->load_use(m.use().name(), m.use().description(), lines.at(m.use().flat_list_index()));
+
+            if (-1 != m.upstream_changelog().flat_list_index() && ! m.upstream_changelog().name().empty())
+            {
+                std::string value(lines.at(m.upstream_changelog().flat_list_index()));
+                if (! value.empty())
+                    id->load_upstream_changelog(m.upstream_changelog().name(),
+                            m.upstream_changelog().description(), value);
+            }
+
+            if (-1 != m.upstream_documentation().flat_list_index() && ! m.upstream_documentation().name().empty())
+            {
+                std::string value(lines.at(m.upstream_documentation().flat_list_index()));
+                if (! value.empty())
+                    id->load_upstream_documentation(m.upstream_documentation().name(),
+                            m.upstream_documentation().description(), value);
+            }
+
+            if (-1 != m.upstream_release_notes().flat_list_index() && ! m.upstream_release_notes().name().empty())
+            {
+                std::string value(lines.at(m.upstream_release_notes().flat_list_index()));
+                if (! value.empty())
+                    id->load_upstream_release_notes(m.upstream_release_notes().name(),
+                            m.upstream_release_notes().description(), value);
+            }
+
+            if (-1 != m.bugs_to().flat_list_index() && ! m.bugs_to().name().empty())
+            {
+                std::string value(lines.at(m.bugs_to().flat_list_index()));
+                if (! value.empty())
+                    id->load_bugs_to(m.bugs_to().name(),
+                            m.bugs_to().description(), value);
+            }
+
+            if (-1 != m.remote_ids().flat_list_index() && ! m.remote_ids().name().empty())
+            {
+                std::string value(lines.at(m.remote_ids().flat_list_index()));
+                if (! value.empty())
+                    id->load_remote_ids(m.remote_ids().name(),
+                            m.remote_ids().description(), value);
+            }
+        }
+        else
+            id->set_slot(SlotName("UNKNOWN"));
+
+        return true;
+    }
+}
+
 EbuildFlatMetadataCache::EbuildFlatMetadataCache(const Environment * const v, const FSEntry & f,
         const FSEntry & e, time_t t, std::tr1::shared_ptr<const EclassMtimes> m, bool s) :
-    _env(v),
-    _filename(f),
-    _ebuild(e),
-    _master_mtime(t),
-    _eclass_mtimes(m),
-    _silent(s)
+    PrivateImplementationPattern<EbuildFlatMetadataCache>(new Implementation<EbuildFlatMetadataCache>(v, f, e, t, m, s))
+{
+}
+
+EbuildFlatMetadataCache::~EbuildFlatMetadataCache()
 {
 }
 
@@ -57,9 +276,9 @@ EbuildFlatMetadataCache::load(const std::tr1::shared_ptr<const EbuildID> & id)
 {
     using namespace std::tr1::placeholders;
 
-    Context context("When loading version metadata from '" + stringify(_filename) + "':");
+    Context context("When loading version metadata from '" + stringify(_imp->filename) + "':");
 
-    std::ifstream cache(stringify(_filename).c_str());
+    std::ifstream cache(stringify(_imp->filename).c_str());
 
     if (cache)
     {
@@ -70,167 +289,282 @@ EbuildFlatMetadataCache::load(const std::tr1::shared_ptr<const EbuildID> & id)
 
         try
         {
-            if (lines.size() >= 15)
+            std::map<std::string, std::string> keys;
+            std::string duplicate;
+            for (std::vector<std::string>::const_iterator it(lines.begin()),
+                     it_end(lines.end()); it_end != it; ++it)
             {
-                id->set_eapi(lines[14]);
-                bool ok(true);
-
-                if (id->eapi()->supported())
+                std::string::size_type equals(it->find('='));
+                if (std::string::npos == equals)
                 {
-                    const EAPIEbuildMetadataVariables & m(*id->eapi()->supported()->ebuild_metadata_variables());
-
-                    {
-                        time_t cache_time(std::max(_master_mtime, _filename.mtime()));
-                        std::set<std::string> tokens;
-                        tokenise_whitespace(lines[9], std::inserter(tokens, tokens.begin()));
-                        ok = _ebuild.mtime() <= cache_time;
-
-                        if (ok && ! tokens.empty())
-                            ok = tokens.end() == std::find_if(tokens.begin(), tokens.end(),
-                                    std::tr1::bind(std::greater<time_t>(), std::tr1::bind(
-                                            std::tr1::mem_fn(&EclassMtimes::mtime), _eclass_mtimes.get(), _1), cache_time));
-                    }
-
-                    if (ok)
-                        ok = static_cast<int>(lines.size()) >= m.minimum_flat_cache_size();
-
-                    if (ok)
-                    {
-                        if (-1 != m.dependencies().flat_cache_index())
-                            if (! m.dependencies().name().empty())
-                            {
-                                DependenciesRewriter rewriter;
-                                parse_depend(lines.at(m.dependencies().flat_cache_index()), _env, id, *id->eapi())->accept(rewriter);
-                                id->load_build_depend(m.dependencies().name() + ".DEPEND", m.dependencies().description() + " (build)", rewriter.depend());
-                                id->load_run_depend(m.dependencies().name() + ".RDEPEND", m.dependencies().description() + " (run)", rewriter.rdepend());
-                                id->load_post_depend(m.dependencies().name() + ".PDEPEND", m.dependencies().description() + " (post)", rewriter.pdepend());
-                            }
-
-                        if (-1 != m.build_depend().flat_cache_index())
-                            if (! m.build_depend().name().empty())
-                                id->load_build_depend(m.build_depend().name(), m.build_depend().description(), lines.at(m.build_depend().flat_cache_index()));
-
-                        if (-1 != m.run_depend().flat_cache_index())
-                            if (! m.run_depend().name().empty())
-                                id->load_run_depend(m.run_depend().name(), m.run_depend().description(), lines.at(m.run_depend().flat_cache_index()));
+                    Log::get_instance()->message("e.cache.flat_hash.not", ll_debug, lc_context)
+                        << "cache file lacks = on line " << ((it - lines.begin()) + 1) << ", assuming flat_list";
+                    return load_flat_list(id, lines, _imp.get());
+                }
 
-                        id->set_slot(SlotName(lines.at(m.slot().flat_cache_index())));
+                if (! keys.insert(std::make_pair(it->substr(0, equals), it->substr(equals + 1))).second)
+                    duplicate = it->substr(0, equals);
+            }
 
-                        if (-1 != m.src_uri().flat_cache_index())
-                            if (! m.src_uri().name().empty())
-                                id->load_src_uri(m.src_uri().name(), m.src_uri().description(), lines.at(m.src_uri().flat_cache_index()));
+            Context ctx("When loading flat_hash format cache file:");
 
-                        if (-1 != m.restrictions().flat_cache_index())
-                            if (! m.restrictions().name().empty())
-                                id->load_restrict(m.restrictions().name(), m.restrictions().description(), lines.at(m.restrictions().flat_cache_index()));
+            if (! duplicate.empty())
+            {
+                Log::get_instance()->message("e.cache.flat_hash.broken", ll_warning, lc_context)
+                    << "cache file contains duplicate key '" << duplicate << "'";
+                return false;
+            }
 
-                        if (-1 != m.homepage().flat_cache_index())
-                            if (! m.homepage().name().empty())
-                                id->load_homepage(m.homepage().name(), m.homepage().description(), lines.at(m.homepage().flat_cache_index()));
+            std::map<std::string, std::string>::const_iterator eapi(keys.find("EAPI"));
+            if (keys.end() == eapi)
+            {
+                Log::get_instance()->message("e.cache.flat_hash.broken", ll_warning, lc_context)
+                    << "cache file contains no 'EAPI' key";
+                return false;
+            }
+            id->set_eapi(eapi->second);
 
-                        if (-1 != m.license().flat_cache_index())
-                            if (! m.license().name().empty())
-                                id->load_license(m.license().name(), m.license().description(), lines.at(m.license().flat_cache_index()));
+            if (id->eapi()->supported())
+            {
+                const EAPIEbuildMetadataVariables & m(*id->eapi()->supported()->ebuild_metadata_variables());
 
-                        if (-1 != m.short_description().flat_cache_index())
-                            if (! m.short_description().name().empty())
-                                id->load_short_description(m.short_description().name(),
-                                        m.short_description().description(),
-                                        lines.at(m.short_description().flat_cache_index()));
+                {
+                    bool ok(_imp->ebuild.mtime() == destringify<std::time_t>(keys["_mtime_"]));
+                    if (! ok)
+                        Log::get_instance()->message("e.cache.flat_hash.mtime", ll_debug, lc_context)
+                            << "ebuild has mtime " << _imp->ebuild.mtime() << ", but expected " << keys["_mtime_"];
 
-                        if (-1 != m.long_description().flat_cache_index())
-                            if (! m.long_description().name().empty())
+                    if (ok && id->eapi()->supported()->ebuild_options()->support_eclasses())
+                    {
+                        std::vector<std::string> eclasses;
+                        tokenise<delim_kind::AnyOfTag, delim_mode::DelimiterTag>(keys["_eclasses_"], "\t", "", std::back_inserter(eclasses));
+                        FSEntry eclassdir(id->repository()->location_key()->value() / "eclass");
+                        for (std::vector<std::string>::const_iterator it(eclasses.begin()),
+                                 it_end(eclasses.end()); it_end != it; ++it)
+                        {
+                            std::string eclass_name(*it);
+                            if (eclasses.end() == ++it)
                             {
-                                std::string value(lines.at(m.long_description().flat_cache_index()));
-                                if (! value.empty())
-                                    id->load_long_description(m.long_description().name(),
-                                            m.long_description().description(), value);
+                                Log::get_instance()->message("e.cache.flat_hash.eclass.truncated", ll_warning, lc_context)
+                                    << "_eclasses_ entry is incomplete";
+                                return false;
                             }
+                            FSEntry eclass_dir(std::string::npos != it->find('/') ? *(it++) : eclassdir);
+                            if (eclasses.end() == it)
+                            {
+                                Log::get_instance()->message("e.cache.flat_hash.eclass.truncated", ll_warning, lc_context)
+                                    << "_eclasses_ entry is incomplete";
+                                return false;
+                            }
+                            std::time_t eclass_mtime(destringify<std::time_t>(*it));
 
-                        if (-1 != m.keywords().flat_cache_index())
-                            if (! m.keywords().name().empty())
-                                id->load_keywords(m.keywords().name(), m.keywords().description(), lines.at(m.keywords().flat_cache_index()));
-
-                        if (-1 != m.inherited().flat_cache_index())
-                            if (! m.inherited().name().empty())
-                                id->load_inherited(m.inherited().name(), m.inherited().description(), lines.at(m.inherited().flat_cache_index()));
-
-                        if (-1 != m.iuse().flat_cache_index())
-                            if (! m.iuse().name().empty())
-                                id->load_iuse(m.iuse().name(), m.iuse().description(), lines.at(m.iuse().flat_cache_index()));
+                            const FSEntry * eclass(_imp->eclass_mtimes->eclass(eclass_name));
+                            if (! eclass)
+                            {
+                                Log::get_instance()->message("e.cache.flat_hash.eclass.missing", ll_debug, lc_context)
+                                    << "Can't find cache-requested eclass '" << eclass_name << "'";
+                                ok = false;
+                            }
 
-                        if (-1 != m.pdepend().flat_cache_index())
-                            if (! m.pdepend().name().empty())
-                                id->load_post_depend(m.pdepend().name(), m.pdepend().description(), lines.at(m.pdepend().flat_cache_index()));
+                            else if (eclass->dirname() != eclass_dir)
+                            {
+                                Log::get_instance()->message("e.cache.flat_hash.eclass.wrong_location", ll_debug, lc_context)
+                                    << "Cache-requested eclass '" << eclass_name << "' was found at '"
+                                    << eclass->dirname() << "', but expected '" << eclass_dir << "'";
+                                ok = false;
+                            }
 
-                        if (-1 != m.provide().flat_cache_index())
-                            if (! m.provide().name().empty())
-                                id->load_provide(m.provide().name(), m.provide().description(), lines.at(m.provide().flat_cache_index()));
+                            else if (eclass->mtime() != eclass_mtime)
+                            {
+                                Log::get_instance()->message("e.cache.flat_hash.eclass.wrong_mtime", ll_debug, lc_context)
+                                    << "Cache-requested eclass '" << eclass_name << "' has mtime "
+                                    << eclass->mtime() << ", but expected " << eclass_mtime;
+                                ok = false;
+                            }
 
-                        if (-1 != m.use().flat_cache_index())
-                            if (! m.use().name().empty())
-                                id->load_use(m.use().name(), m.use().description(), lines.at(m.use().flat_cache_index()));
+                            if (! ok)
+                                break;
+                        }
+                    }
 
-                        if (-1 != m.upstream_changelog().flat_cache_index())
-                            if (! m.upstream_changelog().name().empty())
+                    else if (ok && id->eapi()->supported()->ebuild_options()->support_exlibs())
+                    {
+                        std::vector<std::string> exlibs;
+                        tokenise<delim_kind::AnyOfTag, delim_mode::DelimiterTag>(keys["_exlibs_"], "\t", "", std::back_inserter(exlibs));
+                        for (std::vector<std::string>::const_iterator it(exlibs.begin()),
+                                 it_end(exlibs.end()); it_end != it; ++it)
+                        {
+                            std::string exlib_name(*it);
+                            if (exlibs.end() == ++it)
                             {
-                                std::string value(lines.at(m.upstream_changelog().flat_cache_index()));
-                                if (! value.empty())
-                                    id->load_upstream_changelog(m.upstream_changelog().name(),
-                                            m.upstream_changelog().description(), value);
+                                Log::get_instance()->message("e.cache.flat_hash.exlib.truncated", ll_warning, lc_context)
+                                    << "_exlibs_ entry is incomplete";
+                                return false;
                             }
-
-                        if (-1 != m.upstream_documentation().flat_cache_index())
-                            if (! m.upstream_documentation().name().empty())
+                            FSEntry exlib_dir(*it);
+                            if (exlibs.end() == ++it)
                             {
-                                std::string value(lines.at(m.upstream_documentation().flat_cache_index()));
-                                if (! value.empty())
-                                    id->load_upstream_documentation(m.upstream_documentation().name(),
-                                            m.upstream_documentation().description(), value);
+                                Log::get_instance()->message("e.cache.flat_hash.exlibs.truncated", ll_warning, lc_context)
+                                    << "_exlibs_ entry is incomplete";
+                                return false;
                             }
+                            std::time_t exlib_mtime(destringify<std::time_t>(*it));
 
-                        if (-1 != m.upstream_release_notes().flat_cache_index())
-                            if (! m.upstream_release_notes().name().empty())
+                            const FSEntry * exlib(_imp->eclass_mtimes->exlib(exlib_name, id->name()));
+                            if (! exlib)
                             {
-                                std::string value(lines.at(m.upstream_release_notes().flat_cache_index()));
-                                if (! value.empty())
-                                    id->load_upstream_release_notes(m.upstream_release_notes().name(),
-                                            m.upstream_release_notes().description(), value);
+                                Log::get_instance()->message("e.cache.flat_hash.exlib.missing", ll_debug, lc_context)
+                                    << "Can't find cache-requested exlib '" << exlib_name << "'";
+                                ok = false;
                             }
 
-                        if (-1 != m.bugs_to().flat_cache_index())
-                            if (! m.bugs_to().name().empty())
+                            else if (exlib->dirname() != exlib_dir)
                             {
-                                std::string value(lines.at(m.bugs_to().flat_cache_index()));
-                                if (! value.empty())
-                                    id->load_bugs_to(m.bugs_to().name(),
-                                            m.bugs_to().description(), value);
+                                Log::get_instance()->message("e.cache.flat_hash.exlib.wrong_location", ll_debug, lc_context)
+                                    << "Cache-requested exlib '" << exlib_name << "' was found at '"
+                                    << exlib->dirname() << "', but expected '" << exlib_dir << "'";
+                                ok = false;
                             }
 
-                        if (-1 != m.remote_ids().flat_cache_index())
-                            if (! m.remote_ids().name().empty())
+                            else if (exlib->mtime() != exlib_mtime)
                             {
-                                std::string value(lines.at(m.remote_ids().flat_cache_index()));
-                                if (! value.empty())
-                                    id->load_remote_ids(m.remote_ids().name(),
-                                            m.remote_ids().description(), value);
+                                Log::get_instance()->message("e.cache.flat_hash.exlib.wrong_mtime", ll_debug, lc_context)
+                                    << "Cache-requested exlib '" << exlib_name << "' has mtime "
+                                    << exlib->mtime() << ", but expected " << exlib_mtime;
+                                ok = false;
                             }
+
+                            if (! ok)
+                                break;
+                        }
+                    }
+
+                    if (! ok)
+                    {
+                        Log::get_instance()->message("e.cache.stale", ll_warning, lc_no_context)
+                            << "Stale cache file at '" << _imp->filename << "'";
+                        return false;
                     }
                 }
-                else
-                    id->set_slot(SlotName("UNKNOWN"));
 
-                if (! ok)
-                    Log::get_instance()->message("e.cache.stale", ll_warning, lc_no_context) << "Stale cache file at '"
-                        << _filename << "'";
-                return ok;
+                if (! m.dependencies().name().empty())
+                {
+                    DependenciesRewriter rewriter;
+                    parse_depend(keys[m.dependencies().name()], _imp->env, id, *id->eapi())->accept(rewriter);
+                    id->load_build_depend(m.dependencies().name() + ".DEPEND", m.dependencies().description() + " (build)", rewriter.depend());
+                    id->load_run_depend(m.dependencies().name() + ".RDEPEND", m.dependencies().description() + " (run)", rewriter.rdepend());
+                    id->load_post_depend(m.dependencies().name() + ".PDEPEND", m.dependencies().description() + " (post)", rewriter.pdepend());
+                }
+
+                if (! m.build_depend().name().empty())
+                    id->load_build_depend(m.build_depend().name(), m.build_depend().description(), keys[m.build_depend().name()]);
+
+                if (! m.run_depend().name().empty())
+                    id->load_run_depend(m.run_depend().name(), m.run_depend().description(), keys[m.run_depend().name()]);
+
+                id->set_slot(SlotName(keys[m.slot().name()]));
+
+                if (! m.src_uri().name().empty())
+                    id->load_src_uri(m.src_uri().name(), m.src_uri().description(), keys[m.src_uri().name()]);
+
+                if (! m.restrictions().name().empty())
+                    id->load_restrict(m.restrictions().name(), m.restrictions().description(), keys[m.restrictions().name()]);
+
+                if (! m.homepage().name().empty())
+                    id->load_homepage(m.homepage().name(), m.homepage().description(), keys[m.homepage().name()]);
+
+                if (! m.license().name().empty())
+                    id->load_license(m.license().name(), m.license().description(), keys[m.license().name()]);
+
+                if (! m.short_description().name().empty())
+                        id->load_short_description(m.short_description().name(),
+                                m.short_description().description(),
+                                keys[m.short_description().name()]);
+
+                if (! m.long_description().name().empty())
+                {
+                    std::string value(keys[m.long_description().name()]);
+                    if (! value.empty())
+                        id->load_long_description(m.long_description().name(),
+                                m.long_description().description(), value);
+                }
+
+                if (! m.keywords().name().empty())
+                    id->load_keywords(m.keywords().name(), m.keywords().description(), keys[m.keywords().name()]);
+
+                if (! m.inherited().name().empty())
+                {
+                    std::vector<std::string> full, brief;
+                    if (id->eapi()->supported()->ebuild_options()->support_eclasses())
+                        tokenise<delim_kind::AnyOfTag, delim_mode::DelimiterTag>(keys["_eclasses_"], "\t", "", std::back_inserter(full));
+                    else if (id->eapi()->supported()->ebuild_options()->support_exlibs())
+                        tokenise<delim_kind::AnyOfTag, delim_mode::DelimiterTag>(keys["_exlibs_"], "\t", "", std::back_inserter(full));
+                    for (std::vector<std::string>::const_iterator it(full.begin()),
+                             it_end(full.end()); it_end != it; ++it)
+                    {
+                        brief.push_back(*it);
+                        if (std::string::npos != (++it)->find('/'))
+                            ++it;
+                    }
+                    id->load_inherited(m.inherited().name(), m.inherited().description(), join(brief.begin(), brief.end(), " "));
+                }
+
+                if (! m.iuse().name().empty())
+                    id->load_iuse(m.iuse().name(), m.iuse().description(), keys[m.iuse().name()]);
+
+                if (! m.pdepend().name().empty())
+                    id->load_post_depend(m.pdepend().name(), m.pdepend().description(), keys[m.pdepend().name()]);
+
+                if (! m.provide().name().empty())
+                    id->load_provide(m.provide().name(), m.provide().description(), keys[m.provide().name()]);
+
+                if (! m.use().name().empty())
+                    id->load_use(m.use().name(), m.use().description(), keys[m.use().name()]);
+
+                if (! m.upstream_changelog().name().empty())
+                {
+                    std::string value(keys[m.upstream_changelog().name()]);
+                    if (! value.empty())
+                        id->load_upstream_changelog(m.upstream_changelog().name(),
+                                m.upstream_changelog().description(), value);
+                }
+
+                if (! m.upstream_documentation().name().empty())
+                {
+                    std::string value(keys[m.upstream_documentation().name()]);
+                    if (! value.empty())
+                        id->load_upstream_documentation(m.upstream_documentation().name(),
+                                m.upstream_documentation().description(), value);
+                }
+
+                if (! m.upstream_release_notes().name().empty())
+                {
+                    std::string value(keys[m.upstream_release_notes().name()]);
+                    if (! value.empty())
+                        id->load_upstream_release_notes(m.upstream_release_notes().name(),
+                                m.upstream_release_notes().description(), value);
+                }
+
+                if (! m.bugs_to().name().empty())
+                {
+                    std::string value(keys[m.bugs_to().name()]);
+                    if (! value.empty())
+                        id->load_bugs_to(m.bugs_to().name(),
+                                m.bugs_to().description(), value);
+                }
+
+                if (! m.remote_ids().name().empty())
+                {
+                    std::string value(keys[m.remote_ids().name()]);
+                    if (! value.empty())
+                        id->load_remote_ids(m.remote_ids().name(),
+                                m.remote_ids().description(), value);
+                }
             }
             else
-            {
-                Log::get_instance()->message("e.cache.incomplete", ll_warning, lc_no_context) << "Incomplete cache file at '"
-                    << _filename << "'";
-                return false;
-            }
+                id->set_slot(SlotName("UNKNOWN"));
+
+            return true;
         }
         catch (const InternalError &)
         {
@@ -239,14 +573,14 @@ EbuildFlatMetadataCache::load(const std::tr1::shared_ptr<const EbuildID> & id)
         catch (const Exception & e)
         {
             Log::get_instance()->message("e.cache.failure", ll_warning, lc_no_context) << "Not using cache file at '"
-                << _filename << "' due to exception '" << e.message() << "' (" << e.what() << ")";
+                << _imp->filename << "' due to exception '" << e.message() << "' (" << e.what() << ")";
             return false;
         }
     }
     else
     {
-        Log::get_instance()->message("e.cache.failure", _silent ? ll_debug : ll_warning, lc_no_context)
-                << "Couldn't use the cache file at '" << _filename << "'";
+        Log::get_instance()->message("e.cache.failure", _imp->silent ? ll_debug : ll_warning, lc_no_context)
+                << "Couldn't use the cache file at '" << _imp->filename << "': " << std::strerror(errno);
         return false;
     }
 }
@@ -269,17 +603,25 @@ namespace
         d->accept(p);
         return stringify(p);
     }
+
+    template <typename T_>
+    void write_kv(std::ostream & stream, const std::string & key, const T_ & value)
+    {
+        std::string str_value(stringify(value));
+        if (! str_value.empty())
+            stream << key << "=" << str_value << std::endl;
+    }
 }
 
 void
 EbuildFlatMetadataCache::save(const std::tr1::shared_ptr<const EbuildID> & id)
 {
-    Context context("When saving version metadata to '" + stringify(_filename) + "':");
+    Context context("When saving version metadata to '" + stringify(_imp->filename) + "':");
 
     try
     {
-        _filename.dirname().dirname().mkdir();
-        _filename.dirname().mkdir();
+        _imp->filename.dirname().dirname().mkdir();
+        _imp->filename.dirname().mkdir();
     }
     catch (const FSError & e)
     {
@@ -290,174 +632,120 @@ EbuildFlatMetadataCache::save(const std::tr1::shared_ptr<const EbuildID> & id)
     if (! id->eapi()->supported())
     {
         Log::get_instance()->message("e.cache.save.eapi_unsupoprted", ll_warning, lc_no_context) << "Not writing cache file to '"
-            << _filename << "' because EAPI '" << id->eapi()->name() << "' is not supported";
+            << _imp->filename << "' because EAPI '" << id->eapi()->name() << "' is not supported";
         return;
     }
 
     std::ostringstream cache;
+    write_kv(cache, "_mtime_", _imp->ebuild.mtime());
+
+    if (id->eapi()->supported()->ebuild_options()->support_eclasses() && id->inherited_key())
+    {
+        std::vector<std::string> eclasses;
+        for (Set<std::string>::ConstIterator it(id->inherited_key()->value()->begin()),
+                 it_end(id->inherited_key()->value()->end()); it_end != it; ++it)
+        {
+            const FSEntry * eclass(_imp->eclass_mtimes->eclass(*it));
+            if (! eclass)
+                throw InternalError(PALUDIS_HERE, "eclass '" + *it + "' disappeared?");
+            eclasses.push_back(*it);
+            eclasses.push_back(stringify(eclass->dirname()));
+            eclasses.push_back(stringify(eclass->mtime()));
+        }
+        write_kv(cache, "_eclasses_", join(eclasses.begin(), eclasses.end(), "\t"));
+    }
+
+    else if (id->eapi()->supported()->ebuild_options()->support_exlibs() && id->inherited_key())
+    {
+        std::vector<std::string> exlibs;
+        for (Set<std::string>::ConstIterator it(id->inherited_key()->value()->begin()),
+                 it_end(id->inherited_key()->value()->end()); it_end != it; ++it)
+        {
+            const FSEntry * exlib(_imp->eclass_mtimes->exlib(*it, id->name()));
+            if (! exlib)
+                throw InternalError(PALUDIS_HERE, "exlib '" + *it + "' for '" + stringify(id->name()) + "' disappeared?");
+            exlibs.push_back(*it);
+            exlibs.push_back(stringify(exlib->dirname()));
+            exlibs.push_back(stringify(exlib->mtime()));
+        }
+        write_kv(cache, "_exlibs_", join(exlibs.begin(), exlibs.end(), "\t"));
+    }
 
     try
     {
         const EAPIEbuildMetadataVariables & m(*id->eapi()->supported()->ebuild_metadata_variables());
-        for (int x(0), x_end(m.minimum_flat_cache_size()) ; x != x_end ; ++x)
+
+        if (! m.dependencies().name().empty())
         {
-            if (x == m.dependencies().flat_cache_index())
-            {
-                std::string s;
+            std::string s;
 
-                if (id->build_dependencies_key())
-                    s.append(flatten(id->build_dependencies_key()->value()) + " ");
-                if (id->run_dependencies_key())
-                    s.append(flatten(id->run_dependencies_key()->value()) + " ");
-                if (id->post_dependencies_key())
-                    s.append(flatten(id->post_dependencies_key()->value()) + " ");
+            if (id->build_dependencies_key())
+                s.append(flatten(id->build_dependencies_key()->value()) + " ");
+            if (id->run_dependencies_key())
+                s.append(flatten(id->run_dependencies_key()->value()) + " ");
+            if (id->post_dependencies_key())
+                s.append(flatten(id->post_dependencies_key()->value()) + " ");
 
-                cache << s << std::endl;
-            }
-            else if (x == m.use().flat_cache_index())
-            {
-                if (id->use_key())
-                    cache << join(id->use_key()->value()->begin(), id->use_key()->value()->end(), " ") << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.build_depend().flat_cache_index())
-            {
-                if (id->build_dependencies_key())
-                    cache << flatten(id->build_dependencies_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.run_depend().flat_cache_index())
-            {
-                if (id->run_dependencies_key())
-                    cache << flatten(id->run_dependencies_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.slot().flat_cache_index())
-            {
-                cache << normalise(id->slot()) << std::endl;
-            }
-            else if (x == m.src_uri().flat_cache_index())
-            {
-                if (id->fetches_key())
-                    cache << flatten(id->fetches_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.restrictions().flat_cache_index())
-            {
-                if (id->restrict_key())
-                    cache << flatten(id->restrict_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.homepage().flat_cache_index())
-            {
-                if (id->homepage_key())
-                    cache << flatten(id->homepage_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.license().flat_cache_index())
-            {
-                if (id->license_key())
-                    cache << flatten(id->license_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.short_description().flat_cache_index())
-            {
-                if (id->short_description_key())
-                    cache << normalise(id->short_description_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.keywords().flat_cache_index())
-            {
-                if (id->keywords_key())
-                    cache << join(id->keywords_key()->value()->begin(), id->keywords_key()->value()->end(), " ") << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.inherited().flat_cache_index())
-            {
-                if (id->inherited_key())
-                    cache << join(id->inherited_key()->value()->begin(), id->inherited_key()->value()->end(), " ") << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.iuse().flat_cache_index())
-            {
-                if (id->iuse_key())
-                    cache << join(id->iuse_key()->value()->begin(), id->iuse_key()->value()->end(), " ") << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.pdepend().flat_cache_index())
-            {
-                if (id->post_dependencies_key())
-                    cache << flatten(id->post_dependencies_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.provide().flat_cache_index())
-            {
-                if (id->provide_key())
-                    cache << flatten(id->provide_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.eapi().flat_cache_index())
-            {
-                cache << normalise(id->eapi()->name()) << std::endl;
-            }
-            else if (x == m.long_description().flat_cache_index())
-            {
-                if (id->long_description_key())
-                    cache << normalise(id->long_description_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.bugs_to().flat_cache_index())
-            {
-                if (id->bugs_to_key())
-                    cache << flatten(id->bugs_to_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.remote_ids().flat_cache_index())
-            {
-                if (id->remote_ids_key())
-                    cache << flatten(id->remote_ids_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.upstream_changelog().flat_cache_index())
-            {
-                if (id->upstream_changelog_key())
-                    cache << flatten(id->upstream_changelog_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.upstream_documentation().flat_cache_index())
-            {
-                if (id->upstream_documentation_key())
-                    cache << flatten(id->upstream_documentation_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else if (x == m.upstream_release_notes().flat_cache_index())
-            {
-                if (id->upstream_release_notes_key())
-                    cache << flatten(id->upstream_release_notes_key()->value()) << std::endl;
-                else
-                    cache << std::endl;
-            }
-            else
-                cache << std::endl;
+            write_kv(cache, m.dependencies().name(), s);
         }
+
+        if (! m.use().name().empty() && id->use_key())
+            write_kv(cache, m.use().name(), join(id->use_key()->value()->begin(), id->use_key()->value()->end(), " "));
+
+        if (! m.build_depend().name().empty() && id->build_dependencies_key())
+            write_kv(cache, m.build_depend().name(), flatten(id->build_dependencies_key()->value()));
+
+        if (! m.run_depend().name().empty() && id->run_dependencies_key())
+            write_kv(cache, m.run_depend().name(), flatten(id->run_dependencies_key()->value()));
+
+        write_kv(cache, m.slot().name(), normalise(id->slot()));
+
+        if (! m.src_uri().name().empty() && id->fetches_key())
+            write_kv(cache, m.src_uri().name(), flatten(id->fetches_key()->value()));
+
+        if (! m.restrictions().name().empty() && id->restrict_key())
+            write_kv(cache, m.restrictions().name(), flatten(id->restrict_key()->value()));
+
+        if (! m.homepage().name().empty() && id->homepage_key())
+            write_kv(cache, m.homepage().name(), flatten(id->homepage_key()->value()));
+
+        if (! m.license().name().empty() && id->license_key())
+            write_kv(cache, m.license().name(), flatten(id->license_key()->value()));
+
+        if (! m.short_description().name().empty() && id->short_description_key())
+            write_kv(cache, m.short_description().name(), normalise(id->short_description_key()->value()));
+
+        if (! m.keywords().name().empty() && id->keywords_key())
+            write_kv(cache, m.keywords().name(), join(id->keywords_key()->value()->begin(), id->keywords_key()->value()->end(), " "));
+
+        if (! m.iuse().name().empty() && id->iuse_key())
+            write_kv(cache, m.iuse().name(), join(id->iuse_key()->value()->begin(), id->iuse_key()->value()->end(), " "));
+
+        if (! m.pdepend().name().empty() && id->post_dependencies_key())
+            write_kv(cache, m.pdepend().name(), flatten(id->post_dependencies_key()->value()));
+
+        if (! m.provide().name().empty() && id->provide_key())
+            write_kv(cache, m.provide().name(), flatten(id->provide_key()->value()));
+
+        write_kv(cache, "EAPI", normalise(id->eapi()->name()));
+
+        if (! m.long_description().name().empty() && id->long_description_key())
+            write_kv(cache, m.long_description().name(), normalise(id->long_description_key()->value()));
+
+        if (! m.bugs_to().name().empty() && id->bugs_to_key())
+            write_kv(cache, m.bugs_to().name(), flatten(id->bugs_to_key()->value()));
+
+        if (! m.remote_ids().name().empty() && id->remote_ids_key())
+            write_kv(cache, m.remote_ids().name(), flatten(id->remote_ids_key()->value()));
+
+        if (! m.upstream_changelog().name().empty() && id->upstream_changelog_key())
+            write_kv(cache, m.upstream_changelog().name(), flatten(id->upstream_changelog_key()->value()));
+
+        if (! m.upstream_documentation().name().empty() && id->upstream_documentation_key())
+            write_kv(cache, m.upstream_documentation().name(), flatten(id->upstream_documentation_key()->value()));
+
+        if (! m.upstream_release_notes().name().empty() && id->upstream_release_notes_key())
+            write_kv(cache, m.upstream_release_notes().name(), flatten(id->upstream_release_notes_key()->value()));
     }
     catch (const InternalError &)
     {
@@ -466,18 +754,20 @@ EbuildFlatMetadataCache::save(const std::tr1::shared_ptr<const EbuildID> & id)
     catch (const Exception & e)
     {
         Log::get_instance()->message("e.cache.save.failure", ll_warning, lc_no_context) << "Not writing cache file to '"
-            << _filename << "' due to exception '" << e.message() << "' (" << e.what() << ")";
+            << _imp->filename << "' due to exception '" << e.message() << "' (" << e.what() << ")";
         return;
     }
 
-    std::ofstream cache_file(stringify(_filename).c_str());
+    std::ofstream cache_file(stringify(_imp->filename).c_str());
 
     if (cache_file)
         cache_file << cache.str();
     else
     {
         Log::get_instance()->message("e.cache.save.failure", ll_warning, lc_no_context) << "Couldn't write cache file to '"
-            << _filename << "': " << std::strerror(errno);
+            << _imp->filename << "': " << std::strerror(errno);
     }
 }
 
+template class PrivateImplementationPattern<EbuildFlatMetadataCache>;
+
diff --git a/paludis/repositories/e/ebuild_flat_metadata_cache.hh b/paludis/repositories/e/ebuild_flat_metadata_cache.hh
index 85ebf9f..88f6b52 100644
--- a/paludis/repositories/e/ebuild_flat_metadata_cache.hh
+++ b/paludis/repositories/e/ebuild_flat_metadata_cache.hh
@@ -24,36 +24,31 @@
 #include <paludis/repositories/e/ebuild_id.hh>
 #include <paludis/util/fs_entry.hh>
 #include <paludis/repositories/e/eclass_mtimes.hh>
+#include <paludis/util/private_implementation_pattern.hh>
 
 namespace paludis
 {
     namespace erepository
     {
         /**
-         * Implements flat file metadata cache handling for a ERepository
-         * using EbuildEntries.
+         * Implements metadata cache handling for a ERepository using
+         * EbuildEntries.
          *
          * \see EbuildEntries
          * \see ERepository
          * \ingroup grperepository
          * \nosubgrouping
          */
-        class EbuildFlatMetadataCache
+        class EbuildFlatMetadataCache :
+            private PrivateImplementationPattern<EbuildFlatMetadataCache>
         {
-            private:
-                const Environment * const _env;
-                const FSEntry & _filename;
-                const FSEntry & _ebuild;
-                time_t _master_mtime;
-                std::tr1::shared_ptr<const EclassMtimes> _eclass_mtimes;
-                bool _silent;
-
             public:
                 ///\name Basic operations
                 ///\{
 
                 EbuildFlatMetadataCache(const Environment * const, const FSEntry & filename, const FSEntry & ebuild,
                         time_t master_mtime, std::tr1::shared_ptr<const EclassMtimes> eclass_mtimes, bool silent);
+                ~EbuildFlatMetadataCache();
 
                 ///\}
 
@@ -66,6 +61,10 @@ namespace paludis
                 ///\}
         };
     }
+
+#ifdef PALUDIS_HAVE_EXTERN_TEMPLATE
+    extern template class PrivateImplementationPattern<erepository::EbuildFlatMetadataCache>;
+#endif
 }
 
 #endif
diff --git a/paludis/repositories/e/eclass_mtimes.cc b/paludis/repositories/e/eclass_mtimes.cc
index 428dc0b..e8136c7 100644
--- a/paludis/repositories/e/eclass_mtimes.cc
+++ b/paludis/repositories/e/eclass_mtimes.cc
@@ -2,6 +2,7 @@
 
 /*
  * Copyright (c) 2006, 2007, 2008 Ciaran McCreesh
+ * Copyright (c) 2008 David Leverton
  *
  * This file is part of the Paludis package manager. Paludis is free software;
  * you can redistribute it and/or modify it under the terms of the GNU General
@@ -18,6 +19,9 @@
  */
 
 #include "eclass_mtimes.hh"
+#include <paludis/repositories/e/e_repository.hh>
+#include <paludis/repositories/e/layout.hh>
+#include <paludis/name.hh>
 #include <paludis/util/private_implementation_pattern-impl.hh>
 #include <paludis/util/sequence.hh>
 #include <paludis/util/fs_entry.hh>
@@ -28,24 +32,58 @@
 
 using namespace paludis;
 
+namespace
+{
+    struct Cache
+    {
+        std::tr1::shared_ptr<const FSEntrySequence> dirs;
+        std::tr1::unordered_map<std::string, FSEntry, Hash<std::string> > files;
+
+        Cache(const std::tr1::shared_ptr<const FSEntrySequence> & d) :
+            dirs(d)
+        {
+        }
+    };
+
+    const FSEntry *
+    lookup(const std::string & e, Cache & c)
+    {
+        std::tr1::unordered_map<std::string, FSEntry, Hash<std::string> >::const_iterator i(c.files.find(e));
+        if (i != c.files.end())
+            return & i->second;
+
+        for (FSEntrySequence::ReverseConstIterator d(c.dirs->rbegin()),
+                 d_end(c.dirs->rend()) ; d != d_end ; ++d)
+        {
+            FSEntry f(*d / e);
+            if (f.exists())
+                return & c.files.insert(std::make_pair(e, f)).first->second;
+        }
+
+        return 0;
+    }
+}
+
 namespace paludis
 {
     template<>
     struct Implementation<EclassMtimes>
     {
-        std::tr1::shared_ptr<const FSEntrySequence> eclass_dirs;
+        const ERepository * repo;
+        mutable Cache eclasses;
+        mutable std::tr1::unordered_map<QualifiedPackageName, Cache, Hash<QualifiedPackageName> > exlibs;
         mutable Mutex mutex;
-        mutable std::tr1::unordered_map<std::string, time_t, Hash<std::string> > eclass_mtimes;
 
-        Implementation(std::tr1::shared_ptr<const FSEntrySequence> d) :
-            eclass_dirs(d)
+        Implementation(const ERepository * r, const std::tr1::shared_ptr<const FSEntrySequence> & d) :
+            repo(r),
+            eclasses(d)
         {
         }
     };
 }
 
-EclassMtimes::EclassMtimes(std::tr1::shared_ptr<const FSEntrySequence> d) :
-    PrivateImplementationPattern<EclassMtimes>(new Implementation<EclassMtimes>(d))
+EclassMtimes::EclassMtimes(const ERepository * r, const std::tr1::shared_ptr<const FSEntrySequence> & d) :
+    PrivateImplementationPattern<EclassMtimes>(new Implementation<EclassMtimes>(r, d))
 {
 }
 
@@ -53,25 +91,20 @@ EclassMtimes::~EclassMtimes()
 {
 }
 
-time_t
-EclassMtimes::mtime(const std::string & e) const
+const FSEntry *
+EclassMtimes::eclass(const std::string & e) const
 {
     Lock l(_imp->mutex);
+    return lookup(e + ".eclass", _imp->eclasses);
+}
 
-    std::tr1::unordered_map<std::string, time_t, Hash<std::string> >::const_iterator i(_imp->eclass_mtimes.find(e));
-    if (i != _imp->eclass_mtimes.end())
-        return i->second;
-
-    time_t r(0);
-    for (FSEntrySequence::ConstIterator d(_imp->eclass_dirs->begin()),
-            d_end(_imp->eclass_dirs->end()) ; d != d_end ; ++d)
-    {
-        FSEntry f(*d / (e + ".eclass"));
-        if (f.exists())
-            r = std::max(r, f.mtime());
-    }
-
-    _imp->eclass_mtimes.insert(std::make_pair(e, r));
-    return r;
+const FSEntry *
+EclassMtimes::exlib(const std::string & e, const QualifiedPackageName & qpn) const
+{
+    Lock l(_imp->mutex);
+    std::tr1::unordered_map<QualifiedPackageName, Cache, Hash<QualifiedPackageName> >::iterator cache(_imp->exlibs.find(qpn));
+    if (_imp->exlibs.end() == cache)
+        cache = _imp->exlibs.insert(std::make_pair(qpn, Cache(_imp->repo->layout()->exlibsdirs(qpn)))).first;
+    return lookup(e + ".exlib", cache->second);
 }
 
diff --git a/paludis/repositories/e/eclass_mtimes.hh b/paludis/repositories/e/eclass_mtimes.hh
index 891f29e..40ca5cb 100644
--- a/paludis/repositories/e/eclass_mtimes.hh
+++ b/paludis/repositories/e/eclass_mtimes.hh
@@ -20,14 +20,17 @@
 #ifndef PALUDIS_GUARD_PALUDIS_REPOSITORIES_E_ECLASS_MTIMES_HH
 #define PALUDIS_GUARD_PALUDIS_REPOSITORIES_E_ECLASS_MTIMES_HH 1
 
+#include <paludis/name-fwd.hh>
 #include <paludis/util/private_implementation_pattern.hh>
 #include <paludis/util/fs_entry-fwd.hh>
 #include <tr1/memory>
 
 namespace paludis
 {
+    class ERepository;
+
     /**
-     * Holds an eclass mtimes cache for a ERepository.
+     * Holds an eclass mtimes cache for an ERepository.
      *
      * \see ERepository
      * \ingroup grperepository
@@ -40,15 +43,20 @@ namespace paludis
             ///\name Basic operations
             ///\{
 
-            EclassMtimes(std::tr1::shared_ptr<const FSEntrySequence>);
+            EclassMtimes(const ERepository *, const std::tr1::shared_ptr<const FSEntrySequence> &);
             ~EclassMtimes();
 
             ///\}
 
             /**
-             * Fetch the mtime for a given eclass.
+             * Fetch the full path of a given eclass.
+             */
+            const FSEntry * eclass(const std::string &) const;
+
+            /**
+             * Fetch the full path of a given exlib, on the path of a given package.
              */
-            time_t mtime(const std::string &) const;
+            const FSEntry * exlib(const std::string &, const QualifiedPackageName &) const;
     };
 }