Function cvSeqRemoveSlice

deps/opencv/modules/core/src/datastructs.cpp:1671–1740

Remove slice from the middle of the sequence. !!! TODO !!! Implement more efficient algorithm

// Remove slice from the middle of the sequence.
// !!! TODO !!! Implement more efficient algorithm
CV_IMPL void
cvSeqRemoveSlice( CvSeq* seq, CvSlice slice )
{
    int total, length;

    if( !CV_IS_SEQ(seq) )
        CV_Error( CV_StsBadArg, "Invalid sequence header" );

    length = cvSliceLength( slice, seq );
    total = seq->total;

    if( slice.start_index < 0 )
        slice.start_index += total;
    else if( slice.start_index >= total )
        slice.start_index -= total;

    if( (unsigned)slice.start_index >= (unsigned)total )
        CV_Error( CV_StsOutOfRange, "start slice index is out of range" );

    slice.end_index = slice.start_index + length;

    if ( slice.start_index == slice.end_index )
        return;

    if( slice.end_index < total )
    {
        CvSeqReader reader_to, reader_from;
        int elem_size = seq->elem_size;

        cvStartReadSeq( seq, &reader_to );
        cvStartReadSeq( seq, &reader_from );

        if( slice.start_index > total - slice.end_index )
        {
            int i, count = seq->total - slice.end_index;
            cvSetSeqReaderPos( &reader_to, slice.start_index );
            cvSetSeqReaderPos( &reader_from, slice.end_index );

            for( i = 0; i < count; i++ )
            {
                memcpy( reader_to.ptr, reader_from.ptr, elem_size );
                CV_NEXT_SEQ_ELEM( elem_size, reader_to );
                CV_NEXT_SEQ_ELEM( elem_size, reader_from );
            }

            cvSeqPopMulti( seq, 0, slice.end_index - slice.start_index );
        }
        else
        {
            int i, count = slice.start_index;
            cvSetSeqReaderPos( &reader_to, slice.end_index );
            cvSetSeqReaderPos( &reader_from, slice.start_index );

            for( i = 0; i < count; i++ )
            {
                CV_PREV_SEQ_ELEM( elem_size, reader_to );
                CV_PREV_SEQ_ELEM( elem_size, reader_from );