Update to Scintilla5 (#2867)

[geany-mirror.git] / scintilla / src / SplitVector.h

// Scintilla source code edit control
/** @file SplitVector.h
 ** Main data structure for holding arrays that handle insertions
 ** and deletions efficiently.
 **/
// Copyright 1998-2007 by Neil Hodgson <neilh@scintilla.org>
// The License.txt file describes the conditions under which this software may be distributed.

#ifndef SPLITVECTOR_H
#define SPLITVECTOR_H

namespace Scintilla::Internal {

template <typename T>
class SplitVector {
protected:
        std::vector<T> body;
        T empty;        /// Returned as the result of out-of-bounds access.
        ptrdiff_t lengthBody;
        ptrdiff_t part1Length;
        ptrdiff_t gapLength;    /// invariant: gapLength == body.size() - lengthBody
        ptrdiff_t growSize;

        /// Move the gap to a particular position so that insertion and
        /// deletion at that point will not require much copying and
        /// hence be fast.
        void GapTo(ptrdiff_t position) noexcept {
                if (position != part1Length) {
                        try {
                                if (gapLength > 0) {    // If gap to move
                                        // This can never fail but std::move and std::move_backward are not noexcept.
                                        if (position < part1Length) {
                                                // Moving the gap towards start so moving elements towards end
                                                std::move_backward(
                                                        body.data() + position,
                                                        body.data() + part1Length,
                                                        body.data() + gapLength + part1Length);
                                        } else {        // position > part1Length
                                                // Moving the gap towards end so moving elements towards start
                                                std::move(
                                                        body.data() + part1Length + gapLength,
                                                        body.data() + gapLength + position,
                                                        body.data() + part1Length);
                                        }
                                }
                                part1Length = position;
                        } catch (...) {
                                // Ignore any exception
                        }
                }
        }

        /// Check that there is room in the buffer for an insertion,
        /// reallocating if more space needed.
        void RoomFor(ptrdiff_t insertionLength) {
                if (gapLength < insertionLength) {
                        while (growSize < static_cast<ptrdiff_t>(body.size() / 6))
                                growSize *= 2;
                        ReAllocate(body.size() + insertionLength + growSize);
                }
        }

        void Init() {
                body.clear();
                body.shrink_to_fit();
                lengthBody = 0;
                part1Length = 0;
                gapLength = 0;
                growSize = 8;
        }

public:
        /// Construct a split buffer.
        SplitVector() : empty(), lengthBody(0), part1Length(0), gapLength(0), growSize(8) {
        }

        // Deleted so SplitVector objects can not be copied.
        SplitVector(const SplitVector &) = delete;
        SplitVector(SplitVector &&) = delete;
        void operator=(const SplitVector &) = delete;
        void operator=(SplitVector &&) = delete;

        ~SplitVector() {
        }

        ptrdiff_t GetGrowSize() const noexcept {
                return growSize;
        }

        void SetGrowSize(ptrdiff_t growSize_) noexcept {
                growSize = growSize_;
        }

        /// Reallocate the storage for the buffer to be newSize and
        /// copy existing contents to the new buffer.
        /// Must not be used to decrease the size of the buffer.
        void ReAllocate(ptrdiff_t newSize) {
                if (newSize < 0)
                        throw std::runtime_error("SplitVector::ReAllocate: negative size.");

                if (newSize > static_cast<ptrdiff_t>(body.size())) {
                        // Move the gap to the end
                        GapTo(lengthBody);
                        gapLength += newSize - static_cast<ptrdiff_t>(body.size());
                        // RoomFor implements a growth strategy but so does vector::resize so
                        // ensure vector::resize allocates exactly the amount wanted by
                        // calling reserve first.
                        body.reserve(newSize);
                        body.resize(newSize);
                }
        }

        /// Retrieve the element at a particular position.
        /// Retrieving positions outside the range of the buffer returns empty or 0.
        const T& ValueAt(ptrdiff_t position) const noexcept {
                if (position < part1Length) {
                        if (position < 0) {
                                return empty;
                        } else {
                                return body[position];
                        }
                } else {
                        if (position >= lengthBody) {
                                return empty;
                        } else {
                                return body[gapLength + position];
                        }
                }
        }

        /// Set the element at a particular position.
        /// Setting positions outside the range of the buffer performs no assignment
        /// but asserts in debug builds.
        template <typename ParamType>
        void SetValueAt(ptrdiff_t position, ParamType&& v) noexcept {
                if (position < part1Length) {
                        PLATFORM_ASSERT(position >= 0);
                        if (position < 0) {
                                ;
                        } else {
                                body[position] = std::forward<ParamType>(v);
                        }
                } else {
                        PLATFORM_ASSERT(position < lengthBody);
                        if (position >= lengthBody) {
                                ;
                        } else {
                                body[gapLength + position] = std::forward<ParamType>(v);
                        }
                }
        }

        /// Retrieve the element at a particular position.
        /// The position must be within bounds or an assertion is triggered.
        const T &operator[](ptrdiff_t position) const noexcept {
                PLATFORM_ASSERT(position >= 0 && position < lengthBody);
                if (position < part1Length) {
                        return body[position];
                } else {
                        return body[gapLength + position];
                }
        }

        /// Retrieve reference to the element at a particular position.
        /// This, instead of the const variant, can be used to mutate in-place.
        /// The position must be within bounds or an assertion is triggered.
        T &operator[](ptrdiff_t position) noexcept {
                PLATFORM_ASSERT(position >= 0 && position < lengthBody);
                if (position < part1Length) {
                        return body[position];
                } else {
                        return body[gapLength + position];
                }
        }

        /// Retrieve the length of the buffer.
        ptrdiff_t Length() const noexcept {
                return lengthBody;
        }

        /// Insert a single value into the buffer.
        /// Inserting at positions outside the current range fails.
        void Insert(ptrdiff_t position, T v) {
                PLATFORM_ASSERT((position >= 0) && (position <= lengthBody));
                if ((position < 0) || (position > lengthBody)) {
                        return;
                }
                RoomFor(1);
                GapTo(position);
                body[part1Length] = std::move(v);
                lengthBody++;
                part1Length++;
                gapLength--;
        }

        /// Insert a number of elements into the buffer setting their value.
        /// Inserting at positions outside the current range fails.
        void InsertValue(ptrdiff_t position, ptrdiff_t insertLength, T v) {
                PLATFORM_ASSERT((position >= 0) && (position <= lengthBody));
                if (insertLength > 0) {
                        if ((position < 0) || (position > lengthBody)) {
                                return;
                        }
                        RoomFor(insertLength);
                        GapTo(position);
                        std::fill(body.data() + part1Length, body.data() + part1Length + insertLength, v);
                        lengthBody += insertLength;
                        part1Length += insertLength;
                        gapLength -= insertLength;
                }
        }

        /// Add some new empty elements.
        /// InsertValue is good for value objects but not for unique_ptr objects
        /// since they can only be moved from once.
        /// Callers can write to the returned pointer to transform inputs without copies.
        T *InsertEmpty(ptrdiff_t position, ptrdiff_t insertLength) {
                PLATFORM_ASSERT((position >= 0) && (position <= lengthBody));
                if (insertLength > 0) {
                        if ((position < 0) || (position > lengthBody)) {
                                return nullptr;
                        }
                        RoomFor(insertLength);
                        GapTo(position);
                        for (ptrdiff_t elem = part1Length; elem < part1Length + insertLength; elem++) {
                                T emptyOne = {};
                                body[elem] = std::move(emptyOne);
                        }
                        lengthBody += insertLength;
                        part1Length += insertLength;
                        gapLength -= insertLength;
                }
                return body.data() + position;
        }

        /// Ensure at least length elements allocated,
        /// appending zero valued elements if needed.
        void EnsureLength(ptrdiff_t wantedLength) {
                if (Length() < wantedLength) {
                        InsertEmpty(Length(), wantedLength - Length());
                }
        }

        /// Insert text into the buffer from an array.
        void InsertFromArray(ptrdiff_t positionToInsert, const T s[], ptrdiff_t positionFrom, ptrdiff_t insertLength) {
                PLATFORM_ASSERT((positionToInsert >= 0) && (positionToInsert <= lengthBody));
                if (insertLength > 0) {
                        if ((positionToInsert < 0) || (positionToInsert > lengthBody)) {
                                return;
                        }
                        RoomFor(insertLength);
                        GapTo(positionToInsert);
                        std::copy(s + positionFrom, s + positionFrom + insertLength, body.data() + part1Length);
                        lengthBody += insertLength;
                        part1Length += insertLength;
                        gapLength -= insertLength;
                }
        }

        /// Delete one element from the buffer.
        void Delete(ptrdiff_t position) {
                PLATFORM_ASSERT((position >= 0) && (position < lengthBody));
                DeleteRange(position, 1);
        }

        /// Delete a range from the buffer.
        /// Deleting positions outside the current range fails.
        /// Cannot be noexcept as vector::shrink_to_fit may be called and it may throw.
        void DeleteRange(ptrdiff_t position, ptrdiff_t deleteLength) {
                PLATFORM_ASSERT((position >= 0) && (position + deleteLength <= lengthBody));
                if ((position < 0) || ((position + deleteLength) > lengthBody)) {
                        return;
                }
                if ((position == 0) && (deleteLength == lengthBody)) {
                        // Full deallocation returns storage and is faster
                        Init();
                } else if (deleteLength > 0) {
                        GapTo(position);
                        lengthBody -= deleteLength;
                        gapLength += deleteLength;
                }
        }

        /// Delete all the buffer contents.
        void DeleteAll() {
                DeleteRange(0, lengthBody);
        }

        /// Retrieve a range of elements into an array
        void GetRange(T *buffer, ptrdiff_t position, ptrdiff_t retrieveLength) const {
                // Split into up to 2 ranges, before and after the split then use memcpy on each.
                ptrdiff_t range1Length = 0;
                if (position < part1Length) {
                        const ptrdiff_t part1AfterPosition = part1Length - position;
                        range1Length = retrieveLength;
                        if (range1Length > part1AfterPosition)
                                range1Length = part1AfterPosition;
                }
                std::copy(body.data() + position, body.data() + position + range1Length, buffer);
                buffer += range1Length;
                position = position + range1Length + gapLength;
                const ptrdiff_t range2Length = retrieveLength - range1Length;
                std::copy(body.data() + position, body.data() + position + range2Length, buffer);
        }

        /// Compact the buffer and return a pointer to the first element.
        /// Also ensures there is an empty element beyond logical end in case its
        /// passed to a function expecting a NUL terminated string.
        T *BufferPointer() {
                RoomFor(1);
                GapTo(lengthBody);
                T emptyOne = {};
                body[lengthBody] = std::move(emptyOne);
                return body.data();
        }

        /// Return a pointer to a range of elements, first rearranging the buffer if
        /// needed to make that range contiguous.
        T *RangePointer(ptrdiff_t position, ptrdiff_t rangeLength) noexcept {
                if (position < part1Length) {
                        if ((position + rangeLength) > part1Length) {
                                // Range overlaps gap, so move gap to start of range.
                                GapTo(position);
                                return body.data() + position + gapLength;
                        } else {
                                return body.data() + position;
                        }
                } else {
                        return body.data() + position + gapLength;
                }
        }

        /// Return a pointer to a single element.
        /// Does not rearrange the buffer.
        const T *ElementPointer(ptrdiff_t position) const noexcept {
                if (position < part1Length) {
                        return body.data() + position;
                } else {
                        return body.data() + position + gapLength;
                }
        }

        /// Return the position of the gap within the buffer.
        ptrdiff_t GapPosition() const noexcept {
                return part1Length;
        }
};

}

#endif