change MAINTENANCE move plugins sources into separate subdirectories
diff --git a/src/plugins_exts/metadata.c b/src/plugins_exts/metadata.c
new file mode 100644
index 0000000..726ecb9
--- /dev/null
+++ b/src/plugins_exts/metadata.c
@@ -0,0 +1,169 @@
+/**
+ * @file plugins_exts_nacm.c
+ * @author Radek Krejci <rkrejci@cesnet.cz>
+ * @brief libyang extension plugin - Metadata (RFC 7952)
+ *
+ * Copyright (c) 2019 CESNET, z.s.p.o.
+ *
+ * This source code is licensed under BSD 3-Clause License (the "License").
+ * You may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://opensource.org/licenses/BSD-3-Clause
+ */
+
+#include "metadata.h"
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "libyang.h"
+#include "plugins_exts.h"
+
+/**
+ * @brief Representation of the compiled metadata substatements - simplify storage for the items available via
+ * ::lysc_ext_substmt.
+ */
+struct lyext_metadata {
+    struct lysc_type *type;            /**< type of the metadata (mandatory) */
+    const char *units;                 /**< units of the leaf's type */
+    struct lysc_iffeature *iffeatures; /**< list of if-feature expressions ([sized array](@ref sizedarrays)) */
+    const char *dsc;                   /**< description */
+    const char *ref;                   /**< reference */
+    uint16_t flags;                    /**< [schema node flags](@ref snodeflags) - only LYS_STATUS_* values are allowed */
+};
+
+/**
+ * @brief Compile annotation extension instances.
+ *
+ * Implementation of ::lyplg_ext_compile_clb callback set as lyext_plugin::compile.
+ */
+static LY_ERR
+annotation_compile(struct lysc_ctx *cctx, const struct lysp_ext_instance *p_ext, struct lysc_ext_instance *c_ext)
+{
+    LY_ERR ret;
+    struct lyext_metadata *annotation;
+    struct lysc_module *mod_c;
+    LY_ARRAY_COUNT_TYPE u;
+
+    /* annotations can appear only at the top level of a YANG module or submodule */
+    if ((c_ext->parent_stmt != LY_STMT_MODULE) && (c_ext->parent_stmt != LY_STMT_SUBMODULE)) {
+        lyplg_ext_log(c_ext, LY_LLERR, LY_EVALID, lysc_ctx_get_path(cctx),
+                "Extension %s is allowed only at the top level of a YANG module or submodule, but it is placed in \"%s\" statement.",
+                p_ext->name, ly_stmt2str(c_ext->parent_stmt));
+        return LY_EVALID;
+    }
+    /* check mandatory argument */
+    if (!c_ext->argument) {
+        lyplg_ext_log(c_ext, LY_LLERR, LY_EVALID, lysc_ctx_get_path(cctx),
+                "Extension %s is instantiated without mandatory argument representing metadata name.", p_ext->name);
+        return LY_EVALID;
+    }
+
+    mod_c = (struct lysc_module *)c_ext->parent;
+
+    /* check for duplication */
+    LY_ARRAY_FOR(mod_c->exts, u) {
+        if ((&mod_c->exts[u] != c_ext) && (mod_c->exts[u].def == c_ext->def) && !strcmp(mod_c->exts[u].argument, c_ext->argument)) {
+            /* duplication of the same annotation extension in a single module */
+            lyplg_ext_log(c_ext, LY_LLERR, LY_EVALID, lysc_ctx_get_path(cctx), "Extension %s is instantiated multiple times.", p_ext->name);
+            return LY_EVALID;
+        }
+    }
+
+    /* compile annotation substatements */
+    c_ext->data = annotation = calloc(1, sizeof *annotation);
+    if (!annotation) {
+        goto emem;
+    }
+    LY_ARRAY_CREATE_GOTO(lysc_ctx_get_ctx(cctx), c_ext->substmts, 6, ret, emem);
+
+    LY_ARRAY_INCREMENT(c_ext->substmts);
+    c_ext->substmts[ANNOTATION_SUBSTMT_IFF].stmt = LY_STMT_IF_FEATURE;
+    c_ext->substmts[ANNOTATION_SUBSTMT_IFF].cardinality = LY_STMT_CARD_ANY;
+    c_ext->substmts[ANNOTATION_SUBSTMT_IFF].storage = &annotation->iffeatures;
+
+    LY_ARRAY_INCREMENT(c_ext->substmts);
+    c_ext->substmts[ANNOTATION_SUBSTMT_UNITS].stmt = LY_STMT_UNITS;
+    c_ext->substmts[ANNOTATION_SUBSTMT_UNITS].cardinality = LY_STMT_CARD_OPT;
+    c_ext->substmts[ANNOTATION_SUBSTMT_UNITS].storage = &annotation->units;
+
+    LY_ARRAY_INCREMENT(c_ext->substmts);
+    c_ext->substmts[ANNOTATION_SUBSTMT_STATUS].stmt = LY_STMT_STATUS;
+    c_ext->substmts[ANNOTATION_SUBSTMT_STATUS].cardinality = LY_STMT_CARD_OPT;
+    c_ext->substmts[ANNOTATION_SUBSTMT_STATUS].storage = &annotation->flags;
+
+    LY_ARRAY_INCREMENT(c_ext->substmts);
+    c_ext->substmts[ANNOTATION_SUBSTMT_TYPE].stmt = LY_STMT_TYPE;
+    c_ext->substmts[ANNOTATION_SUBSTMT_TYPE].cardinality = LY_STMT_CARD_MAND;
+    c_ext->substmts[ANNOTATION_SUBSTMT_TYPE].storage = &annotation->type;
+
+    LY_ARRAY_INCREMENT(c_ext->substmts);
+    c_ext->substmts[ANNOTATION_SUBSTMT_DSC].stmt = LY_STMT_DESCRIPTION;
+    c_ext->substmts[ANNOTATION_SUBSTMT_DSC].cardinality = LY_STMT_CARD_OPT;
+    c_ext->substmts[ANNOTATION_SUBSTMT_DSC].storage = &annotation->dsc;
+
+    LY_ARRAY_INCREMENT(c_ext->substmts);
+    c_ext->substmts[ANNOTATION_SUBSTMT_REF].stmt = LY_STMT_REFERENCE;
+    c_ext->substmts[ANNOTATION_SUBSTMT_REF].cardinality = LY_STMT_CARD_OPT;
+    c_ext->substmts[ANNOTATION_SUBSTMT_REF].storage = &annotation->ref;
+
+    ret = lys_compile_extension_instance(cctx, p_ext, c_ext);
+    return ret;
+
+emem:
+    lyplg_ext_log(c_ext, LY_LLERR, LY_EMEM, lysc_ctx_get_path(cctx), "Memory allocation failed (%s()).", __func__);
+    return LY_EMEM;
+}
+
+/**
+ * @brief INFO printer
+ *
+ * Implementation of ::lyplg_ext_schema_printer_clb set as ::lyext_plugin::sprinter
+ */
+static LY_ERR
+annotation_schema_printer(struct lyspr_ctx *ctx, struct lysc_ext_instance *ext, ly_bool *flag)
+{
+    lysc_print_extension_instance(ctx, ext, flag);
+
+    return LY_SUCCESS;
+}
+
+/**
+ * @brief Free annotation extension instances' data.
+ *
+ * Implementation of ::lyplg_ext_free_clb callback set as ::lyext_plugin::free.
+ */
+static void
+annotation_free(struct ly_ctx *ctx, struct lysc_ext_instance *ext)
+{
+    if (!ext->substmts) {
+        return;
+    }
+
+    lyplg_ext_instance_substatements_free(ctx, ext->substmts);
+    free(ext->data);
+}
+
+/**
+ * @brief Plugin descriptions for the Metadata's annotation extension
+ *
+ * Note that external plugins are supposed to use:
+ *
+ *   LYPLG_EXTENSIONS = {
+ */
+const struct lyplg_ext_record plugins_metadata[] = {
+    {
+        .module = "ietf-yang-metadata",
+        .revision = "2016-08-05",
+        .name = "annotation",
+
+        .plugin.id = "libyang 2 - metadata, version 1",
+        .plugin.compile = &annotation_compile,
+        .plugin.validate = NULL,
+        .plugin.sprinter = &annotation_schema_printer,
+        .plugin.free = annotation_free
+    },
+    {0}     /* terminating zeroed record */
+};