chore: allow access to thawed/unpacked metadata for rewriting

include/dwarfs/reader/filesystem_v2.h

@@ -60,6 +60,10 @@ class mmif;
 class os_access;
 class performance_monitor;
 
+namespace thrift::metadata {
+class metadata;
+}
+
 namespace reader {
 
 struct cache_tidy_config;
@@ -473,6 +477,9 @@ class filesystem_v2 final : public filesystem_v2_lite {
 
   history const& get_history() const;
 
+  std::unique_ptr<thrift::metadata::metadata> thawed_metadata() const;
+  std::unique_ptr<thrift::metadata::metadata> unpacked_metadata() const;
+
   class impl : public impl_lite {
    public:
     virtual int
@@ -484,6 +491,10 @@ class filesystem_v2 final : public filesystem_v2_lite {
     virtual std::string serialize_metadata_as_json(bool simple) const = 0;
     virtual std::optional<std::span<uint8_t const>> header() const = 0;
     virtual history const& get_history() const = 0;
+    virtual std::unique_ptr<thrift::metadata::metadata>
+    thawed_metadata() const = 0;
+    virtual std::unique_ptr<thrift::metadata::metadata>
+    unpacked_metadata() const = 0;
   };
 
  private:

include/dwarfs/reader/internal/metadata_v2.h

@@ -262,6 +262,10 @@ class metadata_v2_utils {
 
   std::string serialize_as_json(bool simple) const;
 
+  std::unique_ptr<thrift::metadata::metadata> thaw() const;
+
+  std::unique_ptr<thrift::metadata::metadata> unpack() const;
+
  private:
   metadata_v2_data const& data_;
 };

src/reader/filesystem_v2.cpp

@@ -332,6 +332,14 @@ class filesystem_ final {
     ir_.cache_blocks(block_numbers);
   }
 
+  std::unique_ptr<thrift::metadata::metadata> thawed_metadata() const {
+    return metadata_v2_utils(meta_).thaw();
+  }
+
+  std::unique_ptr<thrift::metadata::metadata> unpacked_metadata() const {
+    return metadata_v2_utils(meta_).unpack();
+  }
+
  private:
   filesystem_parser make_fs_parser() const {
     return filesystem_parser(mm_, image_offset_, options_.image_size);
@@ -1354,6 +1362,13 @@ class filesystem_full_
     return fs().header();
   }
   history const& get_history() const override { return history_; }
+  std::unique_ptr<thrift::metadata::metadata> thawed_metadata() const override {
+    return fs().thawed_metadata();
+  }
+  std::unique_ptr<thrift::metadata::metadata>
+  unpacked_metadata() const override {
+    return fs().unpacked_metadata();
+  }
 
  private:
   history history_;
@@ -1471,6 +1486,16 @@ history const& filesystem_v2::get_history() const {
   return full_().get_history();
 }
 
+std::unique_ptr<thrift::metadata::metadata>
+filesystem_v2::thawed_metadata() const {
+  return full_().thawed_metadata();
+}
+
+std::unique_ptr<thrift::metadata::metadata>
+filesystem_v2::unpacked_metadata() const {
+  return full_().unpacked_metadata();
+}
+
 auto filesystem_v2::full_() const -> impl const& { return this->as_<impl>(); }
 
 } // namespace dwarfs::reader

src/reader/internal/metadata_v2.cpp

@@ -634,6 +634,14 @@ class metadata_v2_data {
             filesystem_info const* fsinfo,
             std::function<void(std::string const&, uint32_t)> const& icb) const;
 
+  std::unique_ptr<thrift::metadata::metadata> unpack() const {
+    return std::make_unique<thrift::metadata::metadata>(unpack_metadata());
+  }
+
+  std::unique_ptr<thrift::metadata::metadata> thaw() const {
+    return std::make_unique<thrift::metadata::metadata>(meta_.thaw());
+  }
+
  private:
   template <typename K>
   using set_type = phmap::flat_hash_set<K>;
@@ -2426,6 +2434,14 @@ std::string metadata_v2_utils::serialize_as_json(bool simple) const {
   return data_.serialize_as_json(simple);
 }
 
+std::unique_ptr<thrift::metadata::metadata> metadata_v2_utils::thaw() const {
+  return data_.thaw();
+}
+
+std::unique_ptr<thrift::metadata::metadata> metadata_v2_utils::unpack() const {
+  return data_.unpack();
+}
+
 metadata_v2::metadata_v2(
     logger& lgr, std::span<uint8_t const> schema, std::span<uint8_t const> data,
     metadata_options const& options, int inode_offset,