Cleanups in loading of jar files

jbmc/src/java_bytecode/jar_file.cpp

@@ -20,10 +20,7 @@ void jar_filet::initialize_file_index()
 {
   const size_t file_count=m_zip_archive.get_num_files();
   for(size_t index=0; index<file_count; index++)
-  {
-    const auto filename=m_zip_archive.get_filename(index);
-    m_name_to_index.emplace(filename, index);
-  }
+    m_name_to_index.emplace(m_zip_archive.get_filename(index), index);
 }
 
 /// This constructor creates a jar_file object whose contents

jbmc/src/java_bytecode/jar_file.h

@@ -31,7 +31,7 @@ class jar_filet final
   /// Open a JAR file of size \p size loaded in memory at address \p data.
   /// \param data: memory buffer with the contents of the jar file
   /// \param size: size  of the memory buffer
-  /// \throw Throws std::runtime_error if file cannot be opened
+  /// \throw Throws std::runtime_error if data is not in correct format
   jar_filet(const void *data, size_t size);
 
   jar_filet(const jar_filet &)=delete;

jbmc/src/java_bytecode/jar_pool.cpp

@@ -13,11 +13,7 @@ jar_filet &jar_poolt::operator()(const std::string &file_name)
 {
   const auto it = m_archives.find(file_name);
   if(it == m_archives.end())
-  {
-    // VS: Can't construct in place
-    auto file = jar_filet(file_name);
-    return m_archives.emplace(file_name, std::move(file)).first->second;
-  }
+    return m_archives.emplace(file_name, jar_filet(file_name)).first->second;
   else
     return it->second;
 }

jbmc/src/java_bytecode/mz_zip_archive.cpp

@@ -73,13 +73,17 @@ size_t mz_zip_archivet::get_num_files()
 
 std::string mz_zip_archivet::get_filename(const size_t index)
 {
-  const auto id=static_cast<mz_uint>(index);
-  std::vector<char> buffer;
-  buffer.resize(mz_zip_reader_get_filename(m_state.get(), id, nullptr, 0));
-  mz_zip_reader_get_filename(m_state.get(), id, buffer.data(), buffer.size());
-  // Buffer may contain junk returned after \0
-  const auto null_char_it=std::find(buffer.cbegin(), buffer.cend(), '\0');
-  return { buffer.cbegin(), null_char_it };
+  const auto id = static_cast<mz_uint>(index);
+  mz_uint name_size = mz_zip_reader_get_filename(m_state.get(), id, nullptr, 0);
+  if(name_size == 0)
+    return {}; // Failure
+  // It is valid to directly write to a string's buffer (see C++11 standard,
+  // basic_string general requirements [string.require], 21.4.1.5)
+  std::string buffer(name_size, '\0');
+  mz_zip_reader_get_filename(m_state.get(), id, &buffer[0], buffer.size());
+  // Buffer contains trailing \0
+  buffer.resize(name_size - 1);
+  return buffer;
 }
 
 std::string mz_zip_archivet::extract(const size_t index)
@@ -89,12 +93,26 @@ std::string mz_zip_archivet::extract(const size_t index)
   const mz_bool stat_ok=mz_zip_reader_file_stat(m_state.get(), id, &file_stat);
   if(stat_ok==MZ_TRUE)
   {
-    std::vector<char> buffer(file_stat.m_uncomp_size);
-    const mz_bool read_ok=mz_zip_reader_extract_to_mem(
-      m_state.get(), id, buffer.data(), buffer.size(), 0);
-    if(read_ok==MZ_TRUE)
-      return { buffer.cbegin(), buffer.cend() };
+    // It is valid to directly write to a string's buffer (see C++11 standard,
+    // basic_string general requirements [string.require], 21.4.1.5)
+    std::string buffer(file_stat.m_uncomp_size, '\0');
+    const mz_bool read_ok = mz_zip_reader_extract_to_mem(
+      m_state.get(), id, &buffer[0], buffer.size(), 0);
+    if(read_ok == MZ_TRUE)
+      return buffer;
   }
   throw std::runtime_error("Could not extract the file");
 }
 
+void mz_zip_archivet::extract_to_file(
+  const size_t index,
+  const std::string &path)
+{
+  const auto id = static_cast<mz_uint>(index);
+  if(
+    mz_zip_reader_extract_to_file(m_state.get(), id, path.c_str(), 0) !=
+    MZ_TRUE)
+  {
+    throw std::runtime_error("Could not extract the file");
+  }
+}

jbmc/src/java_bytecode/mz_zip_archive.h

@@ -28,7 +28,7 @@ class mz_zip_archivet final
   /// Loads a zip buffer
   /// \param data: pointer to the memory buffer
   /// \param size: size of the buffer
-  /// \throw Throws std::runtime_error if file cannot be opened
+  /// \throw Throws std::runtime_error if data is not in correct format
   mz_zip_archivet(const void *data, size_t size);
 
   mz_zip_archivet(const mz_zip_archivet &)=delete;
@@ -51,6 +51,12 @@ class mz_zip_archivet final
   /// \throw Throws std::runtime_error if file cannot be extracted
   /// \return Contents of the file in the archive
   std::string extract(size_t index);
+  /// Write contents of nth file in the archive to a file
+  /// \param index: id of the file in the archive
+  /// \param path:  path to which to write the contents of the file
+  /// \throw Throws std::runtime_error if file cannot be written
+  void extract_to_file(size_t index, const std::string &path);
+
 private:
   std::unique_ptr<mz_zip_archive_statet> m_state;
 };