magic: refactor construction

3 files changed, 73 insertions, 6 deletions

diff --git a/cabinet/magic.cpp b/cabinet/magic.cpp
index f8d7337..96e212f 100644
--- a/cabinet/magic.cpp
+++ b/cabinet/magic.cpp
@@ -2,18 +2,60 @@
 
 #include <magic.h>
 
+#include <cerrno>
+#include <expected>
+#include <string_view>
+#include <system_error>
 #include <utility>
 
 namespace cab
 {
 
-  magic::magic(magic::flags flags)
-      : m_cookie{magic_open(std::to_underlying(flags))}
+  auto magic::open(magic::flags flags, std::string_view database) noexcept -> std::expected<magic, std::error_code>
+  {
+    auto cookie = magic_open(std::to_underlying(flags));
+    if (!cookie)
+    {
+      return std::unexpected{
+        std::error_code{errno, std::system_category()}
+      };
+    }
+
+    if (auto success = magic_load(cookie, database.data()); success < 0)
+    {
+      return std::unexpected{std::make_error_code(std::errc::invalid_argument)};
+    }
+
+    return magic{cookie};
+  }
+
+  magic::magic(::magic_t cookie) noexcept
+      : m_cookie{cookie}
+  {}
+
+  magic::magic(magic && other) noexcept
+      : m_cookie{std::exchange(other.m_cookie, nullptr)}
   {}
 
   magic::~magic()
   {
-    magic_close(m_cookie);
+    if (m_cookie)
+    {
+      magic_close(m_cookie);
+    }
+  }
+
+  auto magic::operator=(magic && other) noexcept -> magic &
+  {
+    std::swap(m_cookie, other.m_cookie);
+    return *this;
+  }
+
+  auto swap(magic & lhs, magic & rhs) noexcept -> void
+  {
+    auto temp = std::move(lhs);
+    lhs = std::move(rhs);
+    rhs = std::move(lhs);
   }
 
 }  // namespace cab
diff --git a/cabinet/magic.hpp b/cabinet/magic.hpp
index 02af9c2..25cf60b 100644
--- a/cabinet/magic.hpp
+++ b/cabinet/magic.hpp
@@ -3,6 +3,9 @@
 
 #include <magic.h>
 
+#include <expected>
+#include <string_view>
+#include <system_error>
 #include <utility>
 
 namespace cab
@@ -40,13 +43,23 @@ namespace cab
       no_simh = MAGIC_NO_CHECK_SIMH,
     };
 
-    magic(flags flags);
+    auto static open(flags flags, std::string_view database = {}) noexcept -> std::expected<magic, std::error_code>;
+
     ~magic();
+    magic(magic const &) = delete;
+    magic(magic && other) noexcept;
+
+    auto operator=(magic const &) -> magic & = delete;
+    auto operator=(magic && other) noexcept -> magic &;
 
   private:
-    magic_t m_cookie{};
+    explicit magic(::magic_t cookie) noexcept;
+
+    ::magic_t m_cookie{};
   };
 
+  auto swap(magic & lhs, magic & rhs) noexcept -> void;
+
   constexpr auto operator|(magic::flags lhs, magic::flags rhs) noexcept -> magic::flags
   {
     return static_cast<magic::flags>(std::to_underlying(lhs) | std::to_underlying(rhs));
diff --git a/cabinet/main.cpp b/cabinet/main.cpp
index 26dd690..bec0a5c 100644
--- a/cabinet/main.cpp
+++ b/cabinet/main.cpp
@@ -1,6 +1,18 @@
 #include <cabinet/magic.hpp>
 
+#include <cstdlib>
+#include <iostream>
+#include <print>
+
 auto main() -> int
 {
-  [[maybe_unused]] auto magic = cab::magic{cab::magic::flags::print_debug | cab::magic::flags::follow_symlinks};
+  auto magic = cab::magic::open(cab::magic::flags::print_debug |      //
+                                cab::magic::flags::follow_symlinks |  //
+                                cab::magic::flags::mime);
+
+  if (!magic)
+  {
+    std::println(std::cerr, "Failed to initialize libmagic: {}", magic.error().message());
+    return EXIT_FAILURE;
+  }
 }