Function cvStartReadSeq

deps/opencv/modules/core/src/datastructs.cpp:925–977

Initialize sequence reader: */

/* Initialize sequence reader: */
CV_IMPL void
cvStartReadSeq( const CvSeq *seq, CvSeqReader * reader, int reverse )
{
    CvSeqBlock *first_block;
    CvSeqBlock *last_block;

    if( reader )
    {
        reader->seq = 0;
        reader->block = 0;
        reader->ptr = reader->block_max = reader->block_min = 0;
    }

    if( !seq || !reader )
        CV_Error( CV_StsNullPtr, "" );

    reader->header_size = sizeof( CvSeqReader );
    reader->seq = (CvSeq*)seq;

    first_block = seq->first;

    if( first_block )
    {
        last_block = first_block->prev;
        reader->ptr = first_block->data;
        reader->prev_elem = CV_GET_LAST_ELEM( seq, last_block );
        reader->delta_index = seq->first->start_index;

        if( reverse )
        {
            schar *temp = reader->ptr;

            reader->ptr = reader->prev_elem;
            reader->prev_elem = temp;

            reader->block = last_block;
        }
        else
        {
            reader->block = first_block;
        }

        reader->block_min = reader->block->data;
        reader->block_max = reader->block_min + reader->block->count * seq->elem_size;
    }
    else
    {
        reader->delta_index = 0;
        reader->block = 0;

        reader->ptr = reader->prev_elem = reader->block_min = reader->block_max = 0;
    }
}


/* Change the current reading block