add is_decodable to files (#453)

Author: andiwand

src/odr/exceptions.cpp

@@ -129,4 +129,10 @@ NotEncryptedError::NotEncryptedError()
 InvalidPath::InvalidPath(const std::string &message)
     : std::runtime_error("invalid path: " + message) {}
 
+UnsupportedFileEncoding::UnsupportedFileEncoding(const std::string &message)
+    : std::runtime_error("unsupported file encoding: " + message) {}
+
+FileEncryptedError::FileEncryptedError()
+    : std::runtime_error("file encrypted error") {}
+
 } // namespace odr

src/odr/exceptions.hpp

@@ -220,4 +220,14 @@ struct InvalidPath final : std::runtime_error {
   explicit InvalidPath(const std::string &message);
 };
 
+/// @brief Unsupported file encoding
+struct UnsupportedFileEncoding final : std::runtime_error {
+  explicit UnsupportedFileEncoding(const std::string &message);
+};
+
+/// @brief File is encrypted
+struct FileEncryptedError final : std::runtime_error {
+  explicit FileEncryptedError();
+};
+
 } // namespace odr

src/odr/file.cpp

@@ -125,6 +125,10 @@ DecodedFile DecodedFile::decrypt(const std::string &password) const {
   return DecodedFile(m_impl->decrypt(password));
 }
 
+bool DecodedFile::is_decodable() const noexcept {
+  return m_impl->is_decodable();
+}
+
 bool DecodedFile::is_text_file() const {
   return std::dynamic_pointer_cast<internal::abstract::TextFile>(m_impl) !=
          nullptr;

src/odr/file.hpp

@@ -200,6 +200,8 @@ class DecodedFile {
   [[nodiscard]] EncryptionState encryption_state() const;
   [[nodiscard]] DecodedFile decrypt(const std::string &password) const;
 
+  [[nodiscard]] bool is_decodable() const noexcept;
+
   [[nodiscard]] bool is_text_file() const;
   [[nodiscard]] bool is_image_file() const;
   [[nodiscard]] bool is_archive_file() const;

src/odr/internal/abstract/file.hpp

@@ -50,6 +50,8 @@ class DecodedFile {
     (void)password;
     return nullptr;
   }
+
+  [[nodiscard]] virtual bool is_decodable() const noexcept = 0;
 };
 
 class TextFile : public DecodedFile {

src/odr/internal/cfb/cfb_file.cpp

@@ -26,6 +26,8 @@ DecoderEngine CfbFile::decoder_engine() const noexcept {
   return DecoderEngine::odr;
 }
 
+bool CfbFile::is_decodable() const noexcept { return true; }
+
 std::shared_ptr<abstract::Archive> CfbFile::archive() const {
   return std::make_shared<CfbArchive>(m_cfb);
 }

src/odr/internal/cfb/cfb_file.hpp

@@ -27,6 +27,8 @@ class CfbFile final : public abstract::ArchiveFile {
   [[nodiscard]] FileMeta file_meta() const noexcept override;
   [[nodiscard]] DecoderEngine decoder_engine() const noexcept override;
 
+  [[nodiscard]] bool is_decodable() const noexcept override;
+
   [[nodiscard]] std::shared_ptr<abstract::Archive> archive() const override;
 
 private:

src/odr/internal/common/image_file.cpp

@@ -1,5 +1,7 @@
 #include <odr/internal/common/image_file.hpp>
 
+#include <odr/exceptions.hpp>
+
 namespace odr::internal {
 
 ImageFile::ImageFile(std::shared_ptr<abstract::File> file,
@@ -18,6 +20,10 @@ DecoderEngine ImageFile::decoder_engine() const noexcept {
   return DecoderEngine::odr;
 }
 
-std::shared_ptr<abstract::Image> ImageFile::image() const { return {}; }
+bool ImageFile::is_decodable() const noexcept { return false; }
+
+std::shared_ptr<abstract::Image> ImageFile::image() const {
+  throw UnsupportedFileEncoding("generally unsupported");
+}
 
 } // namespace odr::internal

src/odr/internal/common/image_file.hpp

@@ -14,6 +14,8 @@ class ImageFile final : public abstract::ImageFile {
   [[nodiscard]] FileMeta file_meta() const noexcept override;
   [[nodiscard]] DecoderEngine decoder_engine() const noexcept override;
 
+  [[nodiscard]] bool is_decodable() const noexcept override;
+
   [[nodiscard]] std::shared_ptr<abstract::Image> image() const override;
 
 private:

src/odr/internal/csv/csv_file.cpp

@@ -28,4 +28,6 @@ DecoderEngine CsvFile::decoder_engine() const noexcept {
   return DecoderEngine::odr;
 }
 
+bool CsvFile::is_decodable() const noexcept { return false; }
+
 } // namespace odr::internal::csv