UT_PackedArrayOfArrays.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        UT_PackedArrayOfArrays.h (UT Library, C++)
 *
 * COMMENTS:    An array of arrays that is more efficiently
 *              laid out than the UT_Array<UT_Array<T> >
 *              Only allows appending, however.
 */

#pragma once

#ifndef __UT_PACKED_ARRAY_OF_ARRAYS_H__
#define __UT_PACKED_ARRAY_OF_ARRAYS_H__

#include "UT_API.h"

#include "UT_Array.h"
#include "UT_Span.h"
#include "UT_IteratorRange.h"

template <typename T>
class UT_API_TMPL UT_PackedArrayOfArrays
{
public:
    typedef UT_Array<T> value_type;

    UT_PackedArrayOfArrays()
    {
    }

    void        clear()
                { myOffsets.clear(); myData.clear(); }
    bool        isEmpty() const
                { return size() == 0; }

    /// Returns the number of arrays in this structure.
    exint       size() const { return SYSmax(myOffsets.size() - 1, 0); }
    exint       entries() const { return size(); }

    int64       getMemoryUsage(bool inclusive = false) const
                {
                    return (inclusive ? sizeof(*this) : 0) +
                           myOffsets.getMemoryUsage(false) +
                           myData.getMemoryUsage(false);
                }

    /// Adds a new array to the end of our list of arrays.
    void        append(const UT_Array<T> &arr)
                { append(arr.array(), arr.entries()); }
    void        append(const T *data, exint len)
                {
                    if (myOffsets.isEmpty())
                        myOffsets.append(0);
                    for (exint i = 0; i < len; i++)
                        myData.append(data[i]);
                    myOffsets.append(myData.entries());
                }
    void        append(const UT_PackedArrayOfArrays<T> &arr, exint idx)
                { append(arr.arrayData(idx), arr.arrayLen(idx)); }

    /// Appends an array of arrays to our list.
    void        concat(const UT_PackedArrayOfArrays<T> &arr)
                { 
                    for (exint i = 0; i < arr.entries(); i++)
                        append(arr, i);
                }

    /// Moves an array of arrays to our list.
    void        concat(UT_PackedArrayOfArrays<T> &&arr)
                {
                    // If the array is empty just steal the other array.
                    if (isEmpty())
                    {
                        *this = std::move(arr);
                        return;
                    }

                    // Otherwise we can do a move concat for the data, but the
                    // offsets need to be shifted.
                    myData.concat(std::move(arr.myData));

                    myOffsets.bumpCapacity(myOffsets.size() + arr.size());
                    for (exint i = 0, n = arr.size(); i < n; ++i)
                        myOffsets.append(myOffsets.last() + arr.arrayLen(i));

                    arr.myOffsets.clear();
                }

    /// Appends a new array and returns a pointer to the resulting
    /// data so it can be filled in.
    T           *appendArray(exint len)
                {
                    if (myOffsets.isEmpty())
                        myOffsets.append(0);
                    exint base = myOffsets.last();
                    myOffsets.append(base+len);
                    myData.bumpSize(base+len);
                    return myData.array() + base;
                }

    /// From the given idxth array, return the idx_in_array element
    const T     &operator()(exint idx, exint idx_in_array) const
                {
                    UT_ASSERT_P(idx >= 0 && idx < size());
                    exint       base = myOffsets(idx);
                    UT_ASSERT_P(base+idx_in_array < myOffsets(idx+1));
                    return myData(base+idx_in_array);
                }

    /// Extracts an array into a UT_Array.
    void        extract(UT_Array<T> &result, exint idx) const
                {
                    UT_ASSERT_P(idx >= 0 && idx < size());
                    exint       base = myOffsets(idx);
                    exint       len = myOffsets(idx+1)-base;
                    result.entries(len);
                    for (exint i = 0; i < len; i++)
                        result(i) = myData(base+i);
                }

    T           *arrayData(exint idx)
                {
                    // This is less than equal to as it is valid to
                    // point to the final element if the corresponding
                    // array is empty!
                    UT_ASSERT_P(myOffsets(idx) <= myData.size());
                    return myData.array() + myOffsets(idx);
                }
    const T     *arrayData(exint idx) const
                {
                    UT_ASSERT_P(myOffsets(idx) <= myData.size());
                    return myData.array() + myOffsets(idx);
                }
    exint       arrayLen(exint idx) const
                {
                    return myOffsets(idx+1)-myOffsets(idx);
                }
    UT_Span<const T>    span(exint idx) const
    {
        return UT_Span<const T>(arrayData(idx), arrayLen(idx));
    }

    /// @{
    /// Returns an iterator range for the specified array.
    UT_IteratorRange<T *> arrayRange(exint idx)
                { return UTmakeRange(arrayData(idx), arrayData(idx + 1)); }
    UT_IteratorRange<const T *> arrayRange(exint idx) const
                { return UTmakeRange(arrayData(idx), arrayData(idx + 1)); }
    /// @}

    /// Decreases, but never expands, to the given maxsize.
    void            truncate(exint maxsize)
    {
        if (maxsize >= 0 && size() > maxsize)
        {
            if (maxsize == 0)
                clear();
            else
            {
                myOffsets.setSize(maxsize+1);
                myData.setSize(myOffsets(maxsize));
            }
        }
    }

    /// These adjust the capacity without adjusting the entries
    /// and are useful for pre-allocing the amount when known
    /// in advance.
    void        setDataCapacity(exint capacity)
                { myData.setCapacity(capacity); }
    void        setDataCapacityIfNeeded(exint capacity)
                { myData.setCapacityIfNeeded(capacity); }
    void        setArrayCapacity(exint capacity)
                { myOffsets.setCapacity(capacity); }
    void        setArrayCapacityIfNeeded(exint capacity)
                { myOffsets.setCapacityIfNeeded(capacity); }
    
    /// The raw offset table stores the end of each array
    /// in the data array.  
    /// Each array has [rawOffsets(idx) ... rawOffsets(idx+1))
    UT_Array<exint>             &rawOffsets() { return myOffsets; }
    const UT_Array<exint>       &rawOffsets() const { return myOffsets; }

    /// All of the array data is in one contiguous block.
    UT_Array<T>                 &rawData() { return myData; }
    const UT_Array<T>           &rawData() const { return myData; }
    
private:
    UT_Array<exint>     myOffsets;
    UT_Array<T>         myData;
};

#endif