/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

// vim:cindent:ts=4:et:sw=4:

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef SpanningCellSorter_h

#define SpanningCellSorter_h

/*

 * Code to sort cells by their colspan, used by BasicTableLayoutStrategy.

 */

#include "PLDHashTable.h"

#include "nsDebug.h"

#include "StackArena.h"

/**

 * The SpanningCellSorter is responsible for accumulating lists of cells

 * with colspans so that those cells can later be enumerated, sorted

 * from lowest number of columns spanned to highest.  It does not use a

 * stable sort (in fact, it currently reverses).

 */

class MOZ_STACK_CLASS SpanningCellSorter {

public:

    SpanningCellSorter();

    ~SpanningCellSorter();

    struct Item {

        int32_t row, col;

        Item *next;

    };

    /**

     * Add a cell to the sorter.  Returns false on out of memory.

     * aColSpan is the number of columns spanned, and aRow/aCol are the

     * position of the cell in the table (for GetCellInfoAt).

     */

    bool AddCell(int32_t aColSpan, int32_t aRow, int32_t aCol);

    /**

     * Get the next *list* of cells.  Each list contains all the cells

     * for a colspan value, and the lists are given in order from lowest

     * to highest colspan.  The colspan value is filled in to *aColSpan.

     */

    Item* GetNext(int32_t *aColSpan);

private:

    enum State { ADDING, ENUMERATING_ARRAY, ENUMERATING_HASH, DONE };

    State mState;

    // store small colspans in an array for fast sorting and

    // enumeration, and large colspans in a hash table

    enum { ARRAY_BASE = 2 };

    enum { ARRAY_SIZE = 8 };

    Item *mArray[ARRAY_SIZE];

    int32_t SpanToIndex(int32_t aSpan) { return aSpan - ARRAY_BASE; }

    int32_t IndexToSpan(int32_t aIndex) { return aIndex + ARRAY_BASE; }

    bool UseArrayForSpan(int32_t aSpan) {

        NS_ASSERTION(SpanToIndex(aSpan) >= 0, "cell without colspan");

        return SpanToIndex(aSpan) < ARRAY_SIZE;

    }

    PLDHashTable mHashTable;

    struct HashTableEntry : public PLDHashEntryHdr {

        int32_t mColSpan;

        Item *mItems;

    };

    static const PLDHashTableOps HashTableOps;

    static PLDHashNumber HashTableHashKey(const void *key);

    static bool

        HashTableMatchEntry(const PLDHashEntryHdr *hdr, const void *key);

    static int SortArray(const void *a, const void *b, void *closure);

    /* state used only during enumeration */

    uint32_t mEnumerationIndex; // into mArray or mSortedHashTable

    HashTableEntry **mSortedHashTable;

    /*

     * operator new is forbidden since we use the pres shell's stack

     * memory, which much be pushed and popped at points matching a

     * push/pop on the C++ stack.

     */

    void* operator new(size_t sz) CPP_THROW_NEW { return nullptr; }

};

#endif