src/core/thread/child_table.hpp

/*
 *  Copyright (c) 2016-2018, The OpenThread Authors.
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 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
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 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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/**
 * @file
 *   This file includes definitions for Thread child table.
 */

#ifndef CHILD_TABLE_HPP_
#define CHILD_TABLE_HPP_

#include "openthread-core-config.h"

#if OPENTHREAD_FTD

#include "common/locator.hpp"
#include "thread/topology.hpp"

namespace ot {

/**
 * This class represents the Thread child table.
 *
 */
class ChildTable : public InstanceLocator
{
    class IteratorBuilder;

public:
    /**
     * This class represents an iterator for iterating through the child entries in the child table.
     *
     */
    class Iterator : public InstanceLocator
    {
        friend class IteratorBuilder;

    public:
        /**
         * This constructor initializes an `Iterator` instance.
         *
         * @param[in] aInstance  A reference to the OpenThread instance.
         * @param[in] aFilter    A child state filter.
         *
         */
        Iterator(Instance &aInstance, Child::StateFilter aFilter);

        /**
         * This method resets the iterator to start over.
         *
         */
        void Reset(void);

        /**
         * This method indicates whether there are no more `Child` entries in the list (iterator has reached end of
         * the list).
         *
         * @retval TRUE   There are no more entries in the list (reached end of the list).
         * @retval FALSE  The current entry is valid.
         *
         */
        bool IsDone(void) const { return (mChild == nullptr); }

        /**
         * This method overloads `++` operator (pre-increment) to advance the iterator.
         *
         * The iterator is moved to point to the next `Child` entry matching the given state filter in the constructor.
         * If there are no more `Child` entries matching the given filter, the iterator becomes empty (i.e.,
         * `GetChild()` returns `nullptr` and `IsDone()` returns `true`).
         *
         */
        void operator++(void) { Advance(); }

        /**
         * This method overloads `++` operator (post-increment) to advance the iterator.
         *
         * The iterator is moved to point to the next `Child` entry matching the given state filter in the constructor.
         * If there are no more `Child` entries matching the given filter, the iterator becomes empty (i.e.,
         * `GetChild()` returns `nullptr` and `IsDone()` returns `true`).
         *
         */
        void operator++(int) { Advance(); }

        /**
         * This method gets the `Child` entry to which the iterator is currently pointing.
         *
         * @returns A pointer to the `Child` entry, or `nullptr` if the iterator is done and/or empty.
         *
         */
        Child *GetChild(void) { return mChild; }

        /**
         * This method overloads the `*` dereference operator and gets a reference to `Child` entry to which the
         * iterator is currently pointing.
         *
         * This method MUST be used when the iterator is not empty/finished (i.e., `IsDone()` returns `false`).
         *
         * @returns A reference to the `Child` entry currently pointed by the iterator.
         *
         */
        Child &operator*(void) { return *mChild; }

        /**
         * This method overloads the `->` dereference operator and gets a pointer to `Child` entry to which the iterator
         * is currently pointing.
         *
         * @returns A pointer to the `Child` entry associated with the iterator, or `nullptr` if iterator is empty/done.
         *
         */
        Child *operator->(void) { return mChild; }

        /**
         * This method overloads operator `==` to evaluate whether or not two `Iterator` instances point to the same
         * child entry.
         *
         * @param[in]  aOther  The other `Iterator` to compare with.
         *
         * @retval TRUE   If the two `Iterator` objects point to the same child entry or both are done.
         * @retval FALSE  If the two `Iterator` objects do not point to the same child entry.
         *
         */
        bool operator==(const Iterator &aOther) const { return mChild == aOther.mChild; }

        /**
         * This method overloads operator `!=` to evaluate whether or not two `Iterator` instances point to the same
         * child entry.
         *
         * @param[in]  aOther  The other `Iterator` to compare with.
         *
         * @retval TRUE   If the two `Iterator` objects do not point to the same child entry.
         * @retval FALSE  If the two `Iterator` objects point to the same child entry or both are done.
         *
         */
        bool operator!=(const Iterator &aOther) const { return mChild != aOther.mChild; }

    private:
        Iterator(Instance &aInstance)
            : InstanceLocator(aInstance)
            , mFilter(Child::StateFilter::kInStateValid)
            , mChild(nullptr)
        {
        }

        void Advance(void);

        Child::StateFilter mFilter;
        Child *            mChild;
    };

    /**
     * This constructor initializes a `ChildTable` instance.
     *
     * @param[in]  aInstance     A reference to the OpenThread instance.
     *
     */
    explicit ChildTable(Instance &aInstance);

    /**
     * This method clears the child table.
     *
     */
    void Clear(void);

    /**
     * This method returns the child table index for a given `Child` instance.
     *
     * @param[in]  aChild  A reference to a `Child`
     *
     * @returns The index corresponding to @p aChild.
     *
     */
    uint16_t GetChildIndex(const Child &aChild) const { return static_cast<uint16_t>(&aChild - mChildren); }

    /**
     * This method returns a pointer to a `Child` entry at a given index, or `nullptr` if the index is out of bounds,
     * i.e., index is larger or equal to maximum number of children allowed (@sa GetMaxChildrenAllowed()).
     *
     * @param[in]  aChildIndex  A child index.
     *
     * @returns A pointer to the `Child` corresponding to the given index, or `nullptr` if the index is out of bounds.
     *
     */
    Child *GetChildAtIndex(uint16_t aChildIndex);

    /**
     * This method gets a new/unused `Child` entry from the child table.
     *
     * @note The returned child entry will be cleared (`memset` to zero).
     *
     * @returns A pointer to a new `Child` entry, or `nullptr` if all `Child` entries are in use.
     *
     */
    Child *GetNewChild(void);

    /**
     * This method searches the child table for a `Child` with a given RLOC16 also matching a given state filter.
     *
     * @param[in]  aRloc16  A RLOC16 address.
     * @param[in]  aFilter  A child state filter.
     *
     * @returns  A pointer to the `Child` entry if one is found, or `nullptr` otherwise.
     *
     */
    Child *FindChild(uint16_t aRloc16, Child::StateFilter aFilter);

    /**
     * This method searches the child table for a `Child` with a given extended address also matching a given state
     * filter.
     *
     * @param[in]  aAddress A reference to an extended address.
     * @param[in]  aFilter  A child state filter.
     *
     * @returns  A pointer to the `Child` entry if one is found, or `nullptr` otherwise.
     *
     */
    Child *FindChild(const Mac::ExtAddress &aAddress, Child::StateFilter aFilter);

    /**
     * This method searches the child table for a `Child` with a given address also matching a given state filter.
     *
     * @param[in]  aAddress A reference to a MAC address.
     * @param[in]  aFilter  A child state filter.
     *
     * @returns  A pointer to the `Child` entry if one is found, or `nullptr` otherwise.
     *
     */
    Child *FindChild(const Mac::Address &aAddress, Child::StateFilter aFilter);

    /**
     * This method indicates whether the child table contains any child matching a given state filter.
     *
     * @param[in]  aFilter  A child state filter.
     *
     * @returns  TRUE if the table contains at least one child table matching the given filter, FALSE otherwise.
     *
     */
    bool HasChildren(Child::StateFilter aFilter) const;

    /**
     * This method returns the number of children in the child table matching a given state filter.
     *
     * @param[in]  aFilter  A child state filter.
     *
     * @returns Number of children matching the given state filer.
     *
     */
    uint16_t GetNumChildren(Child::StateFilter aFilter) const;

    /**
     * This method returns the maximum number of children that can be supported (build-time constant).
     *
     * @note Number of children allowed (from `GetMaxChildrenAllowed()`) can be less than maximum number of supported
     * children.
     *
     * @returns  The maximum number of children supported
     *
     */
    uint16_t GetMaxChildren(void) const { return kMaxChildren; }

    /**
     * This method get the maximum number of children allowed.
     *
     * @returns  The maximum number of children allowed.
     *
     */
    uint16_t GetMaxChildrenAllowed(void) const { return mMaxChildrenAllowed; }

    /**
     * This method sets the maximum number of children allowed.
     *
     * The number of children allowed must be at least one and at most same as maximum supported children (@sa
     * GetMaxChildren()). It can be changed only if the child table is empty.
     *
     * @param[in]  aMaxChildren  Maximum number of children allowed.
     *
     * @retval OT_ERROR_NONE          The number of allowed children changed successfully.
     * @retval OT_ERROR_INVALID_ARGS  If @p aMaxChildren is not in the range [1, Max supported children].
     * @retval OT_ERROR_INVALID_STATE The child table is not empty.
     *
     */
    otError SetMaxChildrenAllowed(uint16_t aMaxChildren);

    /**
     * This method enables range-based `for` loop iteration over all child entries in the child table matching a given
     * state filter.
     *
     * This method should be used as follows:
     *
     *     for (Child &child : aChildTable.Iterate(aFilter)) { ... }
     *
     * @param[in] aFilter  A child state filter.
     *
     * @returns An IteratorBuilder instance.
     *
     */
    IteratorBuilder Iterate(Child::StateFilter aFilter) { return IteratorBuilder(GetInstance(), aFilter); }

private:
    enum
    {
        kMaxChildren = OPENTHREAD_CONFIG_MLE_MAX_CHILDREN,
    };

    class IteratorBuilder : public InstanceLocator
    {
    public:
        IteratorBuilder(Instance &aInstance, Child::StateFilter aFilter)
            : InstanceLocator(aInstance)
            , mFilter(aFilter)
        {
        }

        Iterator begin(void) { return Iterator(GetInstance(), mFilter); }
        Iterator end(void) { return Iterator(GetInstance()); }

    private:
        Child::StateFilter mFilter;
    };

    uint16_t mMaxChildrenAllowed;
    Child    mChildren[kMaxChildren];
};

} // namespace ot

#endif // OPENTHREAD_FTD

#endif // CHILD_TABLE_HPP_