refactor: factor out fsst components

CMakeLists.txt

@@ -495,6 +495,7 @@ if(WITH_TESTS)
       test/filesystem_test.cpp
       test/filesystem_writer_test.cpp
       test/fragment_category_test.cpp
+      test/fsst_test.cpp
       test/glob_matcher_test.cpp
       test/global_metadata_test.cpp
       test/integral_value_parser_test.cpp

cmake/libdwarfs.cmake

@@ -51,6 +51,7 @@ add_library(
   src/internal/file_status_conv.cpp
   src/internal/fs_section.cpp
   src/internal/fs_section_checker.cpp
+  src/internal/fsst.cpp
   src/internal/glob_to_regex.cpp
   src/internal/malloc_buffer.cpp
   src/internal/metadata_utils.cpp

include/dwarfs/internal/fsst.h

@@ -0,0 +1,73 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/**
+ * \author     Marcus Holland-Moritz (github@mhxnet.de)
+ * \copyright  Copyright (c) Marcus Holland-Moritz
+ *
+ * This file is part of dwarfs.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the “Software”), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <memory>
+#include <optional>
+#include <span>
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace dwarfs::internal {
+
+class fsst_encoder {
+ public:
+  struct bulk_compression_result {
+    std::string dictionary;
+    std::string buffer;
+    std::vector<std::string_view> compressed_data;
+  };
+
+  static std::optional<bulk_compression_result>
+  compress(std::span<std::string_view const> data, bool force = false);
+  static std::optional<bulk_compression_result>
+  compress(std::span<std::string const> data, bool force = false);
+};
+
+class fsst_decoder {
+ public:
+  explicit fsst_decoder(std::string_view dictionary);
+
+  std::string decompress(std::string_view data) const {
+    return impl_->decompress(data);
+  }
+
+  class impl {
+   public:
+    virtual ~impl() = default;
+
+    virtual std::string decompress(std::string_view data) const = 0;
+  };
+
+ private:
+  std::unique_ptr<impl const> impl_;
+};
+
+} // namespace dwarfs::internal

src/internal/fsst.cpp

@@ -0,0 +1,174 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/**
+ * \author     Marcus Holland-Moritz (github@mhxnet.de)
+ * \copyright  Copyright (c) Marcus Holland-Moritz
+ *
+ * This file is part of dwarfs.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the “Software”), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <cassert>
+#include <numeric>
+#include <stdexcept>
+
+#include <dwarfs/internal/fsst.h>
+
+#include <fmt/format.h>
+
+#include <fsst.h>
+
+namespace dwarfs::internal {
+
+namespace {
+
+template <typename T>
+std::optional<fsst_encoder::bulk_compression_result>
+fsst_compress_(std::span<T const> input, bool force) {
+  std::optional<fsst_encoder::bulk_compression_result> output;
+
+  if (input.empty()) {
+    return output;
+  }
+
+  auto const size = input.size();
+  size_t total_input_size = 0;
+  std::vector<size_t> len_vec;
+  std::vector<unsigned char const*> ptr_vec;
+
+  len_vec.reserve(size);
+  ptr_vec.reserve(size);
+
+  for (auto const& s : input) {
+    ptr_vec.emplace_back(reinterpret_cast<unsigned char const*>(s.data()));
+    len_vec.emplace_back(s.size());
+    total_input_size += s.size();
+  }
+
+  std::unique_ptr<::fsst_encoder_t, decltype(&::fsst_destroy)> enc{
+      ::fsst_create(size, len_vec.data(), ptr_vec.data(), 0), &::fsst_destroy};
+
+  std::string symtab;
+
+  symtab.resize(sizeof(::fsst_decoder_t));
+
+  auto const symtab_size =
+      ::fsst_export(enc.get(), reinterpret_cast<unsigned char*>(symtab.data()));
+  symtab.resize(symtab_size);
+
+  std::vector<size_t> out_len_vec;
+  std::vector<unsigned char*> out_ptr_vec;
+  std::string buffer;
+
+  out_len_vec.resize(size);
+  out_ptr_vec.resize(size);
+
+  if (symtab_size >= total_input_size && !force) {
+    return output;
+  }
+
+  buffer.resize(total_input_size);
+
+  for (;;) {
+    auto const num_compressed = ::fsst_compress(
+        enc.get(), size, len_vec.data(), ptr_vec.data(), buffer.size(),
+        reinterpret_cast<unsigned char*>(buffer.data()), out_len_vec.data(),
+        out_ptr_vec.data());
+
+    if (num_compressed == size) {
+      break;
+    } else if (!force) {
+      return output;
+    }
+
+    buffer.resize(2 * buffer.size());
+  }
+
+  size_t const compressed_size =
+      (out_ptr_vec.back() - out_ptr_vec.front()) + out_len_vec.back();
+
+  if (symtab_size + compressed_size >= total_input_size && !force) {
+    return output;
+  }
+
+  assert(reinterpret_cast<char*>(out_ptr_vec.front()) == buffer.data());
+  assert(compressed_size == std::accumulate(out_len_vec.begin(),
+                                            out_len_vec.end(),
+                                            static_cast<size_t>(0)));
+
+  buffer.resize(compressed_size);
+
+  output.emplace();
+
+  output->dictionary = std::move(symtab);
+  output->buffer = std::move(buffer);
+  output->compressed_data.reserve(size);
+
+  for (size_t i = 0; i < size; ++i) {
+    output->compressed_data.emplace_back(std::string_view(
+        reinterpret_cast<char*>(out_ptr_vec[i]), out_len_vec[i]));
+  }
+
+  return output;
+}
+
+class fsst_decoder_ : public fsst_decoder::impl {
+ public:
+  explicit fsst_decoder_(std::string_view dictionary) {
+    auto const read = ::fsst_import(
+        &decoder_, reinterpret_cast<unsigned char const*>(dictionary.data()));
+    if (read != dictionary.size()) {
+      throw std::runtime_error(fmt::format(
+          "read {0} symtab bytes, expected {1}", read, dictionary.size()));
+    }
+  }
+
+  std::string decompress(std::string_view data) const override {
+    thread_local std::string out;
+    auto const size = data.size();
+    out.resize(8 * size);
+    auto outlen = ::fsst_decompress(
+        &decoder_, size, reinterpret_cast<unsigned char const*>(data.data()),
+        out.size(), reinterpret_cast<unsigned char*>(out.data()));
+    out.resize(outlen);
+    return out;
+  }
+
+ private:
+  ::fsst_decoder_t decoder_;
+};
+
+} // namespace
+
+auto fsst_encoder::compress(std::span<std::string_view const> data, bool force)
+    -> std::optional<bulk_compression_result> {
+  return fsst_compress_(data, force);
+}
+
+auto fsst_encoder::compress(std::span<std::string const> data, bool force)
+    -> std::optional<bulk_compression_result> {
+  return fsst_compress_(data, force);
+}
+
+fsst_decoder::fsst_decoder(std::string_view dictionary)
+    : impl_{std::make_unique<fsst_decoder_>(dictionary)} {}
+
+} // namespace dwarfs::internal

src/internal/string_table.cpp

@@ -31,11 +31,10 @@
 
 #include <fmt/format.h>
 
-#include <fsst.h>
-
 #include <dwarfs/error.h>
 #include <dwarfs/logger.h>
 
+#include <dwarfs/internal/fsst.h>
 #include <dwarfs/internal/string_table.h>
 
 namespace dwarfs::internal {
@@ -78,16 +77,8 @@ class packed_string_table : public string_table::impl {
 
       auto st = v_.symtab();
       DWARFS_CHECK(st, "symtab unexpectedly unset");
-      dec_ = std::make_unique<fsst_decoder_t>();
 
-      auto read = fsst_import(
-          dec_.get(), reinterpret_cast<unsigned char const*>(st->data()));
-
-      if (read != st->size()) {
-        DWARFS_THROW(runtime_error,
-                     fmt::format("read {0} symtab bytes, expected {1}", read,
-                                 st->size()));
-      }
+      dec_.emplace(st.value());
 
       ti << "imported dictionary for " << name << " string table";
     }
@@ -118,14 +109,7 @@ class packed_string_table : public string_table::impl {
     }
 
     if constexpr (PackedData) {
-      thread_local std::string out;
-      size_t size = end - beg;
-      out.resize(8 * size);
-      auto outlen = fsst_decompress(
-          dec_.get(), size, reinterpret_cast<unsigned char const*>(beg),
-          out.size(), reinterpret_cast<unsigned char*>(out.data()));
-      out.resize(outlen);
-      return out;
+      return dec_->decompress(std::string_view{beg, end});
     }
 
     return {beg, end};
@@ -158,7 +142,7 @@ class packed_string_table : public string_table::impl {
   string_table::PackedTableView v_;
   char const* const buffer_;
   std::vector<uint32_t> index_;
-  std::unique_ptr<fsst_decoder_t> dec_;
+  std::optional<fsst_decoder> dec_;
 };
 
 string_table::string_table(LegacyTableView v)
@@ -191,94 +175,28 @@ template <typename T>
 thrift::metadata::string_table
 string_table::pack_generic(std::span<T const> input,
                            pack_options const& options) {
-  auto size = input.size();
-  bool pack_data = options.pack_data;
-  size_t total_input_size = 0;
-  std::string buffer;
-  std::string symtab;
-  std::vector<size_t> out_len_vec;
-  std::vector<unsigned char*> out_ptr_vec;
+  auto const size = input.size();
+  std::optional<fsst_encoder::bulk_compression_result> res;
 
-  if (input.empty()) {
-    pack_data = false;
-  }
-
-  if (pack_data) {
-    std::vector<size_t> len_vec;
-    std::vector<unsigned char const*> ptr_vec;
-
-    len_vec.reserve(size);
-    ptr_vec.reserve(size);
-
-    for (auto const& s : input) {
-      ptr_vec.emplace_back(reinterpret_cast<unsigned char const*>(s.data()));
-      len_vec.emplace_back(s.size());
-      total_input_size += s.size();
-    }
-
-    std::unique_ptr<::fsst_encoder_t, decltype(&::fsst_destroy)> enc{
-        ::fsst_create(size, len_vec.data(), ptr_vec.data(), 0),
-        &::fsst_destroy};
-
-    symtab.resize(sizeof(::fsst_decoder_t));
-
-    auto symtab_size = ::fsst_export(
-        enc.get(), reinterpret_cast<unsigned char*>(symtab.data()));
-    symtab.resize(symtab_size);
-
-    if (symtab.size() < total_input_size or options.force_pack_data) {
-      out_len_vec.resize(size);
-      out_ptr_vec.resize(size);
-
-      buffer.resize(options.force_pack_data ? total_input_size
-                                            : total_input_size - symtab.size());
-      size_t num_compressed = 0;
-
-      for (;;) {
-        num_compressed = ::fsst_compress(
-            enc.get(), size, len_vec.data(), ptr_vec.data(), buffer.size(),
-            reinterpret_cast<unsigned char*>(buffer.data()), out_len_vec.data(),
-            out_ptr_vec.data());
-
-        if (num_compressed == size || !options.force_pack_data) {
-          break;
-        }
-
-        buffer.resize(2 * buffer.size());
-      }
-
-      pack_data = num_compressed == size;
-    } else {
-      pack_data = false;
-    }
-  } else {
-    for (auto const& s : input) {
-      total_input_size += s.size();
-    }
+  if (options.pack_data) {
+    res = fsst_encoder::compress(input, options.force_pack_data);
   }
 
   thrift::metadata::string_table output;
 
-  if (pack_data) {
+  if (res.has_value()) {
     // store compressed
-    size_t compressed_size =
-        (out_ptr_vec.back() - out_ptr_vec.front()) + out_len_vec.back();
-
-    DWARFS_CHECK(reinterpret_cast<char*>(out_ptr_vec.front()) == buffer.data(),
-                 "string table compression pointer mismatch");
-    // TODO: only enable this in debug mode
-    DWARFS_CHECK(compressed_size == std::accumulate(out_len_vec.begin(),
-                                                    out_len_vec.end(),
-                                                    static_cast<size_t>(0)),
-                 "string table compression pointer mismatch");
-
-    buffer.resize(compressed_size);
-    output.buffer()->swap(buffer);
-    output.symtab() = std::move(symtab);
+    output.buffer() = std::move(res->buffer);
+    output.symtab() = std::move(res->dictionary);
     output.index()->resize(size);
-    std::ranges::copy(out_len_vec, output.index()->begin());
+    for (size_t i = 0; i < size; ++i) {
+      output.index()[i] = res->compressed_data[i].size();
+    }
   } else {
     // store uncompressed
+    auto const total_input_size =
+        std::accumulate(input.begin(), input.end(), size_t{0},
+                        [](size_t n, auto const& s) { return n + s.size(); });
     output.buffer()->reserve(total_input_size);
     output.index()->reserve(size);
     for (auto const& s : input) {

test/tool_main_test.cpp

@@ -2114,11 +2114,9 @@ TEST(mkdwarfs_test, pack_mode_all) {
   auto fs = t.fs_from_stdout();
   auto info =
       fs.info_as_json({.features = reader::fsinfo_features::for_level(2)});
-  std::set<std::string> expected = {"packed_chunk_table",
-                                    "packed_directories",
-                                    "packed_names",
-                                    "packed_names_index",
-                                    "packed_shared_files_table",
+  std::set<std::string> expected = {
+      "packed_chunk_table",   "packed_directories",        "packed_names",
+      "packed_names_index",   "packed_shared_files_table", "packed_symlinks",
       "packed_symlinks_index"};
   std::set<std::string> fsopt;
   for (auto const& opt : info["options"]) {