refactor(mkdwarfs): abstract out file creation

CMakeLists.txt

@@ -378,6 +378,7 @@ list(
   src/dwarfs/entry.cpp
   src/dwarfs/error.cpp
   src/dwarfs/features.cpp
+  src/dwarfs/file_access_generic.cpp
   src/dwarfs/file_scanner.cpp
   src/dwarfs/file_stat.cpp
   src/dwarfs/file_type.cpp

include/dwarfs/file_access.h

@@ -0,0 +1,49 @@
+/* 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.
+ *
+ * dwarfs is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * dwarfs is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with dwarfs.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <filesystem>
+#include <iosfwd>
+#include <memory>
+#include <system_error>
+
+namespace dwarfs {
+
+class output_stream {
+ public:
+  virtual ~output_stream() = default;
+
+  virtual std::ostream& os() = 0;
+  virtual void close(std::error_code& ec) = 0;
+};
+
+class file_access {
+ public:
+  virtual ~file_access() = default;
+
+  virtual bool exists(std::filesystem::path const& path) const = 0;
+  virtual std::unique_ptr<output_stream>
+  open_output_binary(std::filesystem::path const& path,
+                     std::error_code& ec) const = 0;
+};
+
+} // namespace dwarfs

include/dwarfs/file_access_generic.h

@@ -0,0 +1,32 @@
+/* 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.
+ *
+ * dwarfs is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * dwarfs is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with dwarfs.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <memory>
+
+namespace dwarfs {
+
+class file_access;
+
+std::unique_ptr<file_access const> create_file_access_generic();
+
+} // namespace dwarfs

include/dwarfs/iolayer.h

@@ -26,6 +26,7 @@
 
 namespace dwarfs {
 
+class file_access;
 class os_access;
 class terminal;
 
@@ -34,6 +35,7 @@ struct iolayer {
 
   std::shared_ptr<os_access const> os;
   std::shared_ptr<terminal const> term;
+  std::shared_ptr<file_access const> file;
   std::istream& in;
   std::ostream& out;
   std::ostream& err;

src/dwarfs/file_access_generic.cpp

@@ -0,0 +1,91 @@
+/* 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.
+ *
+ * dwarfs is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * dwarfs is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with dwarfs.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <cerrno>
+#include <filesystem>
+#include <fstream>
+
+#ifdef _WIN32
+#include <folly/portability/Windows.h>
+#endif
+
+#include "dwarfs/file_access.h"
+#include "dwarfs/file_access_generic.h"
+#include "dwarfs/util.h"
+
+namespace dwarfs {
+
+namespace {
+
+void assign_error_code(std::error_code& ec) {
+#ifdef _WIN32
+  ec.assign(::GetLastError(), std::system_category());
+#else
+  ec.assign(errno, std::generic_category());
+#endif
+}
+
+class file_output_stream : public output_stream {
+ public:
+  file_output_stream(std::filesystem::path const& path, std::error_code& ec)
+      : os_{path.string().c_str(), std::ios::binary | std::ios::trunc} {
+    if (os_.bad() || os_.fail() || !os_.is_open()) {
+      assign_error_code(ec);
+    }
+  }
+
+  std::ostream& os() override { return os_; }
+
+  void close(std::error_code& ec) override {
+    os_.close();
+    if (os_.bad()) {
+      assign_error_code(ec);
+    }
+  }
+
+ private:
+  std::ofstream os_;
+};
+
+class file_access_generic : public file_access {
+ public:
+  bool exists(std::filesystem::path const& path) const override {
+    return std::filesystem::exists(path);
+  }
+
+  std::unique_ptr<output_stream>
+  open_output_binary(std::filesystem::path const& path,
+                     std::error_code& ec) const override {
+    auto rv = std::make_unique<file_output_stream>(path, ec);
+    if (ec) {
+      rv.reset();
+    }
+    return rv;
+  }
+};
+
+} // namespace
+
+std::unique_ptr<file_access const> create_file_access_generic() {
+  return std::make_unique<file_access_generic>();
+}
+
+} // namespace dwarfs

src/dwarfs/iolayer.cpp

@@ -21,6 +21,8 @@
 
 #include <iostream>
 
+#include "dwarfs/file_access.h"
+#include "dwarfs/file_access_generic.h"
 #include "dwarfs/iolayer.h"
 #include "dwarfs/os_access_generic.h"
 #include "dwarfs/terminal.h"
@@ -31,6 +33,7 @@ iolayer const& iolayer::system_default() {
   static iolayer const iol{
       .os = std::make_shared<os_access_generic>(),
       .term = terminal::create(),
+      .file = create_file_access_generic(),
       .in = std::cin,
       .out = std::cout,
       .err = std::cerr,

src/mkdwarfs_main.cpp

@@ -37,6 +37,7 @@
 #include <string_view>
 #include <thread>
 #include <utility>
+#include <variant>
 #include <vector>
 
 #ifdef _WIN32
@@ -63,6 +64,7 @@
 #include "dwarfs/console_writer.h"
 #include "dwarfs/entry.h"
 #include "dwarfs/error.h"
+#include "dwarfs/file_access.h"
 #include "dwarfs/filesystem_block_category_resolver.h"
 #include "dwarfs/filesystem_v2.h"
 #include "dwarfs/filesystem_writer.h"
@@ -74,6 +76,7 @@
 #include "dwarfs/mmap.h"
 #include "dwarfs/options.h"
 #include "dwarfs/options_interface.h"
+#include "dwarfs/overloaded.h"
 #include "dwarfs/program_options_helpers.h"
 #include "dwarfs/progress.h"
 #include "dwarfs/scanner.h"
@@ -1035,33 +1038,37 @@ int mkdwarfs_main(int argc, sys_char** argv, iolayer const& iol) {
 
   std::filesystem::path output(output_str);
 
-  std::unique_ptr<std::ostream> os;
+  std::variant<std::monostate, std::unique_ptr<output_stream>,
+               std::ostringstream>
+      os;
 
   if (!options.debug_filter_function) {
     if (output != "-") {
-      if (std::filesystem::exists(output) && !force_overwrite) {
+      if (iol.file->exists(output) && !force_overwrite) {
         iol.err
             << "error: output file already exists, use --force to overwrite\n";
         return 1;
       }
 
-      auto ofs = std::make_unique<std::ofstream>(output, std::ios::binary |
-                                                             std::ios::trunc);
+      std::error_code ec;
+      auto stream = iol.file->open_output_binary(output, ec);
 
-      if (ofs->bad() || !ofs->is_open()) {
+      if (ec) {
         iol.err << "error: cannot open output file '" << output
-                << "': " << ::strerror(errno) << "\n";
+                << "': " << ec.message() << "\n";
         return 1;
       }
 
-      os = std::move(ofs);
+      assert(stream);
+
+      os.emplace<std::unique_ptr<output_stream>>(std::move(stream));
     } else {
 #ifdef _WIN32
       ::_setmode(::_fileno(stdout), _O_BINARY);
 #endif
     }
   } else {
-    os = std::make_unique<std::ostringstream>();
+    os.emplace<std::ostringstream>();
   }
 
   options.enable_history = !no_history;
@@ -1173,9 +1180,18 @@ int mkdwarfs_main(int argc, sys_char** argv, iolayer const& iol) {
   std::unique_ptr<filesystem_writer> fsw;
 
   try {
+    std::ostream& fsw_os = std::visit(
+        overloaded(
+            [&](std::monostate) -> std::ostream& { return iol.out; },
+            [&](std::unique_ptr<output_stream>& os) -> std::ostream& {
+              return os->os();
+            },
+            [&](std::ostringstream& oss) -> std::ostream& { return oss; }),
+        os);
+
     fsw = std::make_unique<filesystem_writer>(
-        os ? *os : iol.out, lgr, wg_compress, prog, schema_bc, metadata_bc,
-        history_bc, fswopts, header_ifs.get());
+        fsw_os, lgr, wg_compress, prog, schema_bc, metadata_bc, history_bc,
+        fswopts, header_ifs.get());
 
     categorized_option<block_compressor> compression_opt;
     contextual_option_parser cop("--compression", compression_opt, cp,
@@ -1245,21 +1261,34 @@ int mkdwarfs_main(int argc, sys_char** argv, iolayer const& iol) {
   if (!options.debug_filter_function) {
     LOG_INFO << "compression CPU time: "
              << time_with_unit(wg_compress.get_cpu_time());
+  }
 
-    if (os) {
-      if (auto ofs = dynamic_cast<std::ofstream*>(os.get())) {
-        ofs->close();
-      }
+  {
+    auto ec = std::visit(
+        overloaded([](std::monostate) -> int { return 0; },
+                   [&](std::unique_ptr<output_stream>& os) -> int {
+                     std::error_code ec;
+                     os->close(ec);
+                     if (ec) {
+                       LOG_ERROR << "failed to close output file '" << output
+                                 << "': " << ec.message();
+                       return 1;
+                     }
+                     os.reset();
+                     return 0;
+                   },
+                   [](std::ostringstream& oss [[maybe_unused]]) -> int {
+                     assert(oss.str().empty());
+                     return 0;
+                   }),
+        os);
 
-      if (os->bad()) {
-        LOG_ERROR << "failed to close output file '" << output
-                  << "': " << strerror(errno);
-        return 1;
-      }
-
-      os.reset();
+    if (ec != 0) {
+      return ec;
     }
+  }
 
+  if (!options.debug_filter_function) {
     std::ostringstream err;
 
     if (prog.errors) {
@@ -1273,11 +1302,6 @@ int mkdwarfs_main(int argc, sys_char** argv, iolayer const& iol) {
 
     ti << "filesystem " << (recompress ? "rewritten " : "created ")
        << err.str();
-  } else {
-    assert(os);
-    auto oss [[maybe_unused]] = dynamic_cast<std::ostringstream*>(os.get());
-    assert(oss);
-    assert(oss->str().empty());
   }
 
   return prog.errors > 0;