[ONOS-3895, ONOS-3896, ONOS-3897] Data type interfaces

Change-Id: I9cd9d80ce0accc017118a944dff96367bca89bde
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangDataTypes.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangDataTypes.java
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+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.datamodel;
+
+/**
+ * ENUM to identify the YANG data type.
+ */
+public enum YangDataTypes {
+    /**
+     * Reference:RFC 6020.
+     * int8 represents integer values between -128 and 127, inclusively.
+     */
+    INT8,
+
+    /**
+     * Reference:RFC 6020.
+     * int16 represents integer values between -32768 and 32767, inclusively.
+     */
+    INT16,
+
+    /**
+     * Reference:RFC 6020.
+     * int32 represents integer values between -2147483648 and 2147483647,
+     * inclusively.
+     */
+    INT32,
+
+    /**
+     * Reference:RFC 6020.
+     * int64 represents integer values between -9223372036854775808 and
+     * 9223372036854775807, inclusively.
+     */
+    INT64,
+
+    /**
+     * Reference:RFC 6020.
+     * uint8 represents integer values between 0 and 255, inclusively.
+     */
+    UINT8,
+
+    /**
+     * Reference:RFC 6020.
+     * uint16 represents integer values between 0 and 65535, inclusively.
+     */
+    UINT16,
+
+    /**
+     * Reference:RFC 6020.
+     * uint32 represents integer values between 0 and 4294967295, inclusively.
+     */
+    UINT32,
+
+    /**
+     * Reference:RFC 6020.
+     * uint64 represents integer values between 0 and 18446744073709551615,
+     * inclusively.
+     */
+    UINT64,
+
+    /**
+     * Reference:RFC 6020.
+     * The decimal64 type represents a subset of the real numbers, which can be
+     * represented by decimal numerals. The value space of decimal64 is the set
+     * of numbers that can be obtained by multiplying a 64-bit signed integer by
+     * a negative power of ten, i.e., expressible as "i x 10^-n" where i is an
+     * integer64 and n is an integer between 1 and 18, inclusively.
+     */
+    DECIMAL64, // TODO: need to implement in type.
+
+    /**
+     * Reference:RFC 6020.
+     * The string built-in type represents human-readable strings in YANG. Legal
+     * characters are tab, carriage return, line feed, and the legal characters
+     * of Unicode and ISO/IEC 10646
+     */
+    STRING,
+
+    /**
+     * Reference:RFC 6020.
+     * The boolean built-in type represents a boolean value.
+     */
+    BOOLEAN,
+
+    /**
+     * Reference:RFC 6020.
+     * The enumeration built-in type represents values from a set of assigned
+     * names.
+     */
+    ENUMERATION,
+
+    /**
+     * Reference:RFC 6020.
+     * The bits built-in type represents a bit set. That is, a bits value is a
+     * set of flags identified by small integer position numbers starting at 0.
+     * Each bit number has an assigned name.
+     */
+    BITS,
+
+    /**
+     * Reference:RFC 6020.
+     * The binary built-in type represents any binary data, i.e., a sequence of
+     * octets.
+     */
+    BINARY,
+
+    /**
+     * Reference:RFC 6020.
+     * The leafref type is used to reference a particular leaf instance in the
+     * data tree. The "path" sub-statement (Section 9.9.2) selects a set of leaf
+     * instances, and the leafref value space is the set of values of these leaf
+     * instances.
+     *
+     * If the leaf with the leafref type represents configuration data, the leaf
+     * it refers to MUST also represent configuration. Such a leaf puts a
+     * constraint on valid data. All leafref nodes MUST reference existing leaf
+     * instances or leafs with default values in use for the data to be valid.
+     *
+     * There MUST NOT be any circular chains of leafrefs.
+     *
+     * If the leaf that the leafref refers to is conditional based on one or
+     * more features, then the leaf with the leafref type MUST also be
+     * conditional based on at least the same set of features.
+     */
+    LEAFREF, // TODO: need to implement in type.
+
+    /**
+     * Reference:RFC 6020.
+     * The identityref type is used to reference an existing identity.
+     */
+    IDENTITYREF,
+
+    /**
+     * Reference:RFC 6020.
+     * The empty built-in type represents a leaf that does not have any value,
+     * it conveys information by its presence or absence.
+     *
+     * An empty type cannot have a default value.
+     */
+    EMPTY,
+
+    /**
+     * Reference:RFC 6020.
+     * The union built-in type represents a value that corresponds to one of its
+     * member types.
+     *
+     * When the type is "union", the "type" statement MUST be present. It is
+     * used to repeatedly specify each member type of the union. It takes as an
+     * argument a string that is the name of a member type.
+     *
+     * A member type can be of any built-in or derived type, except it MUST NOT
+     * be one of the built-in types "empty" or "leafref".
+     *
+     * When a string representing a union data type is validated, the string is
+     * validated against each member type, in the order they are specified in
+     * the "type" statement, until a match is found.
+     *
+     * Any default value or "units" property defined in the member types is not
+     * inherited by the union type.
+     */
+    UNION,
+
+    /**
+     * Reference:RFC 6020.
+     * The instance-identifier built-in type is used to uniquely identify a
+     * particular instance node in the data tree.
+     *
+     * The syntax for an instance-identifier is a subset of the XPath
+     * abbreviated syntax, formally defined by the rule "instance-identifier".
+     * It is used to uniquely identify a node in the data tree. Predicates are
+     * used only for specifying the values for the key nodes for list entries, a
+     * value of a leaf-list entry, or a positional index for a list without
+     * keys. For identifying list entries with keys, each predicate consists of
+     * one equality test per key, and each key MUST have a corresponding
+     * predicate.
+     *
+     * If the leaf with the instance-identifier type represents configuration
+     * data, and the "require-instance" property is "true", the node it refers
+     * to MUST also represent configuration. Such a leaf puts a constraint on
+     * valid data. All such leaf nodes MUST reference existing nodes or leaf
+     * nodes with their default value in use for the data to be valid.
+     */
+    INSTANCE_IDENTIFIER,
+
+    /**
+     * Derived Data type.
+     */
+    DERIVED
+}