feat(forward-compat): add support for metadata feature set (gh #158)

mhx · Dec 5, 2023 · 576e15c · 576e15c
1 parent 829c7b1
commit 576e15c
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Showing 2 changed files with 30 additions and 2 deletions.
diff --git a/src/dwarfs/metadata_v2.cpp b/src/dwarfs/metadata_v2.cpp
@@ -136,6 +136,20 @@ map_frozen(std::span<uint8_t const> schema, std::span<uint8_t const> data) {
   return ret;
 }
 
+MappedFrozen<thrift::metadata::metadata>
+check_frozen(MappedFrozen<thrift::metadata::metadata> meta) {
+  if (meta.features()) {
+    auto unsupported = meta.features()->thaw();
+    if (!unsupported.empty()) {
+      DWARFS_THROW(runtime_error,
+                   fmt::format("file system uses the following features "
+                               "unsupported by this build: {}",
+                               boost::join(unsupported, ", ")));
+    }
+  }
+  return meta;
+}
+
 void analyze_frozen(std::ostream& os,
                     MappedFrozen<thrift::metadata::metadata> const& meta,
                     size_t total_size, int detail) {
@@ -302,7 +316,8 @@ class metadata_ final : public metadata_v2::impl {
             std::span<uint8_t const> data, metadata_options const& options,
             int inode_offset, bool force_consistency_check)
       : data_(data)
-      , meta_(map_frozen<thrift::metadata::metadata>(schema, data_))
+      , meta_(
+            check_frozen(map_frozen<thrift::metadata::metadata>(schema, data_)))
       , global_(lgr, &meta_,
                 options.check_consistency || force_consistency_check)
       , root_(dir_entry_view::from_dir_entry_index(0, &global_))

diff --git a/thrift/metadata.thrift b/thrift/metadata.thrift
@@ -345,6 +345,19 @@ struct metadata {
 
   25: optional string_table     compact_symlinks,
 
+  //=========================================================//
+  // fields added with dwarfs-0.7.0, file system version 2.5 //
+  //=========================================================//
+
    // preferred path separator of original file system
-  26: optional UInt32           preferred_path_separator,
+  26: optional UInt32           preferred_path_separator
+
+  //=========================================================//
+  // fields added with dwarfs-0.7.3, file system version 2.5 //
+  //=========================================================//
+
+  // The set of features used in this file system image. As long
+  // as an older binary supports all features, it will be able
+  // to use images created with newer versions.
+  27: optional set<string>      features,
 }