1 files changed, 95 insertions, 0 deletions
diff --git a/include/lv2/core/lv2_util.h b/include/lv2/core/lv2_util.h
new file mode 100644
index 0000000..82c5e1e
--- /dev/null
+++ b/include/lv2/core/lv2_util.h
@@ -0,0 +1,95 @@
+// Copyright 2016 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#ifndef LV2_CORE_LV2_UTIL_H
+#define LV2_CORE_LV2_UTIL_H
+
+/**
+   @defgroup lv2_util Utilities
+   @ingroup lv2core
+   @{
+*/
+
+#include <lv2/core/lv2.h>
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <string.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+   Return the data for a feature in a features array.
+
+   If the feature is not found, NULL is returned.  Note that this function is
+   only useful for features with data, and can not detect features that are
+   present but have NULL data.
+*/
+static inline void*
+lv2_features_data(const LV2_Feature* const* features, const char* const uri)
+{
+  if (features) {
+    for (const LV2_Feature* const* f = features; *f; ++f) {
+      if (!strcmp(uri, (*f)->URI)) {
+        return (*f)->data;
+      }
+    }
+  }
+  return NULL;
+}
+
+/**
+   Query a features array.
+
+   This function allows getting several features in one call, and detect
+   missing required features, with the same caveat of lv2_features_data().
+
+   The arguments should be a series of const char* uri, void** data, bool
+   required, terminated by a NULL URI.  The data pointers MUST be initialized
+   to NULL.  For example:
+
+   @code
+   LV2_URID_Log* log = NULL;
+   LV2_URID_Map* map = NULL;
+   const char* missing = lv2_features_query(
+        features,
+        LV2_LOG__log,  &log, false,
+        LV2_URID__map, &map, true,
+        NULL);
+   @endcode
+
+   @return NULL on success, otherwise the URI of this missing feature.
+*/
+static inline const char*
+lv2_features_query(const LV2_Feature* const* features, ...)
+{
+  va_list args; // NOLINT(cppcoreguidelines-init-variables)
+  va_start(args, features);
+
+  const char* uri = NULL;
+  while ((uri = va_arg(args, const char*))) {
+    void**     data     = va_arg(args, void**);
+    const bool required = (bool)va_arg(args, int);
+
+    *data = lv2_features_data(features, uri);
+    if (required && !*data) {
+      va_end(args);
+      return uri;
+    }
+  }
+
+  va_end(args);
+  return NULL;
+}
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+/**
+   @}
+*/
+
+#endif // LV2_CORE_LV2_UTIL_H