From 81fa478a642b25715adecf27c283e6f15334d705 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Fri, 5 Jun 2026 08:55:54 +0200
Subject: magic: implement file descriptor support

---
 cabinet/magic.cpp | 10 ++++++++++
 cabinet/magic.hpp |  1 +
 cabinet/main.cpp  |  9 +++++----
 3 files changed, 16 insertions(+), 4 deletions(-)

(limited to 'cabinet')

diff --git a/cabinet/magic.cpp b/cabinet/magic.cpp
index b5c1aaa..08b3046 100644
--- a/cabinet/magic.cpp
+++ b/cabinet/magic.cpp
@@ -63,6 +63,16 @@ namespace cab
     return result;
   }
 
+  auto magic::process(int file_descriptor) -> std::expected<std::string, std::string>
+  {
+    auto result = ::magic_descriptor(m_cookie, file_descriptor);
+    if (!result)
+    {
+      return std::unexpected{std::string{::magic_error(m_cookie)}};
+    }
+    return result;
+  }
+
   auto swap(magic & lhs, magic & rhs) noexcept -> void
   {
     auto temp = std::move(lhs);
diff --git a/cabinet/magic.hpp b/cabinet/magic.hpp
index 222d488..96f4b08 100644
--- a/cabinet/magic.hpp
+++ b/cabinet/magic.hpp
@@ -55,6 +55,7 @@ namespace cab
     auto operator=(magic && other) noexcept -> magic &;
 
     auto process(std::filesystem::path path) -> std::expected<std::string, std::string>;
+    auto process(int file_descriptor) -> std::expected<std::string, std::string>;
 
   private:
     explicit magic(::magic_t cookie) noexcept;
diff --git a/cabinet/main.cpp b/cabinet/main.cpp
index 77a73ca..db2d43b 100644
--- a/cabinet/main.cpp
+++ b/cabinet/main.cpp
@@ -1,7 +1,8 @@
 #include <cabinet/magic.hpp>
 
+#include <fcntl.h>
+
 #include <cstdlib>
-#include <filesystem>
 #include <iostream>
 #include <print>
 
@@ -15,19 +16,19 @@ auto main(int argc, char ** argv) -> int
     return EXIT_FAILURE;
   }
 
-  auto magic = cab::magic::open(flags::follow_symlinks | flags::mime_type);
+  auto magic = cab::magic::open(flags::follow_symlinks | flags::mime_type | flags::forward_errors);
   if (!magic)
   {
     std::println(std::cerr, "Failed to initialize libmagic: {}", magic.error().message());
     return EXIT_FAILURE;
   }
 
-  auto mime_type = magic->process(std::filesystem::path{argv[1]});
+  auto fd = open(argv[1], O_RDONLY);
+  auto mime_type = magic->process(fd);
   if (!mime_type)
   {
     std::println(std::cerr, "Failed to determine file type: {}", mime_type.error());
     return EXIT_FAILURE;
   }
-
   std::println("{}: {}", argv[1], mime_type.value());
 }
-- 
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