rx: add file lock utility

rx/CMakeLists.txt

@@ -9,6 +9,7 @@ add_library(${PROJECT_NAME} OBJECT
     src/hexdump.cpp
     src/mem.cpp
     src/Version.cpp
+    src/FileLock.cpp
 )
 
 target_include_directories(${PROJECT_NAME}

rx/include/rx/FileLock.hpp

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <cstdio>
+#include <utility>
+
+namespace rx {
+void fileLock(std::FILE *file);
+void fileUnlock(std::FILE *file);
+
+class ScopedFileLock {
+  std::FILE *mFile = nullptr;
+
+public:
+  ScopedFileLock() = default;
+  ScopedFileLock(const ScopedFileLock &) = delete;
+  ScopedFileLock &operator=(const ScopedFileLock &) = delete;
+
+  ScopedFileLock(ScopedFileLock &&other) noexcept
+      : mFile(std::exchange(other.mFile, nullptr)) {}
+  ScopedFileLock &operator=(ScopedFileLock &&other) noexcept {
+    std::swap(mFile, other.mFile);
+    return *this;
+  }
+
+  ScopedFileLock(std::FILE *file) : mFile(file) {
+    if (file) {
+      fileLock(file);
+    }
+  }
+
+  ~ScopedFileLock() {
+    if (mFile) {
+      fileUnlock(mFile);
+    }
+  }
+};
+} // namespace rx

rx/include/rx/hexdump.hpp

@@ -4,5 +4,8 @@
 #include <span>
 
 namespace rx {
-void hexdump(std::span<std::byte> bytes);
+void hexdump(std::span<const std::byte> bytes);
+inline void hexdump(const void *data, std::size_t size) {
+  hexdump({reinterpret_cast<const std::byte *>(data), size});
+}
 } // namespace rx

rx/src/FileLock.cpp

@@ -0,0 +1,18 @@
+#include "FileLock.hpp"
+#include <cstdio>
+
+void rx::fileLock(std::FILE *file) {
+#ifdef _WIN32
+  _lock_file(file);
+#else
+  flockfile(file);
+#endif
+}
+
+void rx::fileUnlock(std::FILE *file) {
+#ifdef _WIN32
+  _unlock_file(file);
+#else
+  funlockfile(file);
+#endif
+}

rx/src/hexdump.cpp

@@ -1,10 +1,11 @@
 #include "hexdump.hpp"
+#include "FileLock.hpp"
 #include <cstdio>
 #include <cstring>
 #include <print>
 #include <string>
 
-void rx::hexdump(std::span<std::byte> bytes) {
+void rx::hexdump(std::span<const std::byte> bytes) {
   unsigned sizeWidth = 1;
 
   {
@@ -16,7 +17,7 @@ void rx::hexdump(std::span<std::byte> bytes) {
     }
   }
 
-  flockfile(stderr);
+  rx::ScopedFileLock stderrLock(stderr);
   std::print(stderr, "{} ", std::string(sizeWidth, ' '));
   for (unsigned i = 0; i < 16; ++i) {
     std::print(stderr, " {:02x}", i);
@@ -82,5 +83,4 @@ void rx::hexdump(std::span<std::byte> bytes) {
     }
   }
   std::println(stderr, "");
-  funlockfile(stderr);
 }