Merge "Refactoring checkAndPrepareWriting." into lmp-dev

}

bool BufferWithExtendableBuffer::checkAndPrepareWriting(const int pos, const int size) {

    if (isInAdditionalBuffer(pos)) {

        const int tailPosition = getTailPosition();

        if (pos == tailPosition) {

            // Append data to the tail.

            if (pos + size > static_cast<int>(mAdditionalBuffer.size()) + mOriginalBufferSize) {

                // Need to extend buffer.

                if (!extendBuffer()) {

    if (pos < 0 || size < 0) {

        // Invalid position or size.

        return false;

    }

            }

            mUsedAdditionalBufferSize += size;

        } else if (pos + size > tailPosition) {

            // The access will beyond the tail of used region.

    const size_t totalRequiredSize = static_cast<size_t>(pos + size);

    if (!isInAdditionalBuffer(pos)) {

        // Here don't need to care about the additional buffer.

        if (static_cast<size_t>(mOriginalBufferSize) < totalRequiredSize) {

            // Violate the boundary.

            return false;

        }

    } else {

        if (pos < 0 || mOriginalBufferSize < pos + size) {

            // Invalid position or violate the boundary.

        // The buffer has sufficient capacity.

        return true;

    }

    // Hereafter, pos is in the additional buffer.

    const size_t tailPosition = static_cast<size_t>(getTailPosition());

    if (totalRequiredSize <= tailPosition) {

        // The buffer has sufficient capacity.

        return true;

    }

    if (static_cast<size_t>(pos) != tailPosition) {

        // The additional buffer must be extended from the tail position.

        return false;

    }

    const size_t extendSize = totalRequiredSize -

            std::min(mAdditionalBuffer.size() + mOriginalBufferSize, totalRequiredSize);

    if (extendSize > 0 && !extendBuffer()) {

        // Failed to extend the buffer.

        return false;

    }

    mUsedAdditionalBufferSize += size;

    return true;

}