Merge all the things

cpp/src/arrow/dataset/file_parquet_encryption_test.cc

@@ -38,7 +38,7 @@
 #include "arrow/util/thread_pool.h"
 #include "parquet/arrow/reader.h"
 #include "parquet/encryption/crypto_factory.h"
-#include "parquet/encryption/encryption_internal.h"
+#include "parquet/encryption/encryption_utils.h"
 #include "parquet/encryption/kms_client.h"
 #include "parquet/encryption/test_in_memory_kms.h"
 

cpp/src/arrow/util/io_util.cc

@@ -2296,4 +2296,24 @@ Result<void*> GetSymbol(void* handle, const char* name) {
 #endif
 }
 
+Status CloseDynamicLibrary(void* handle) {
+  if (handle == nullptr) {
+    return Status::Invalid("Attempting to close null library handle");
+  }
+#ifdef _WIN32
+  if (FreeLibrary(reinterpret_cast<HMODULE>(handle))) {
+    return Status::OK();
+  }
+  // win32 api doc: "If the function fails, the return value is zero."
+  return IOErrorFromWinError(GetLastError(), "FreeLibrary() failed");
+#else
+  if (dlclose(handle) == 0) {
+    return Status::OK();
+  }
+  // dlclose(3) man page: "On success, dlclose() returns 0; on error, it returns a nonzero value."
+  auto* error = dlerror();
+  return Status::IOError("dlclose() failed: ", error ? error : "unknown error");
+#endif
+}
+
 }  // namespace arrow::internal

cpp/src/arrow/util/io_util.h

@@ -449,6 +449,13 @@ ARROW_EXPORT Result<void*> LoadDynamicLibrary(const char* path);
 ///         returned; instead an error will be raised.
 ARROW_EXPORT Result<void*> GetSymbol(void* handle, const char* name);
 
+/// \brief Close a dynamic library
+///
+/// This wraps dlclose() except on Windows, where FreeLibrary() is called.
+///
+/// \return Status::OK() if the library was closed successfully, otherwise an error is returned.
+ARROW_EXPORT Status CloseDynamicLibrary(void* handle);
+
 template <typename T>
 Result<T*> GetSymbolAs(void* handle, const char* name) {
   ARROW_ASSIGN_OR_RAISE(void* sym, GetSymbol(handle, name));