/*
 * This is a fragment, included from multiple places in ebwt_search.cpp.
 * It implements the logic of the first phase of the seeded, quality-
 * aware search routine.  It is implemented as a code fragment so that
 * it can be reused in both the half-index-in-memory and full-index-in-
 * memory situations.
 */
{
	btf1.setReportExacts(true);
	bt1.setReportExacts(true);

	if(verbose) {
		cout << patFw << ":" << qual << ", " << patRc << ":" << qualRev << endl;
	}

	bool done = false;
	if(plen < 4) {
		if(!quiet) {
			cerr << "Warning: Skipping read (" << name << ") because it is less than 4 characters long" << endl;
		}
		done = true;
	} else {
		// Check and see if the distribution of Ns disqualifies
		// this read right off the bat
		size_t slen = min<size_t>(plen, seedLen);
		int ns = 0;
		for(size_t i = 0; i < slen; i++) {
			if((int)(Dna5)patFw[i] == 4) {
				if(++ns > seedMms) {
					// Set 'done' so that
					done = true;
					break;
				}
			}
		}
	}
	if(done) {
		ASSERT_NO_HITS_FW(true);
		ASSERT_NO_HITS_RC(true);
		DONEMASK_SET(patid);
		skipped = true;
		sink->finishRead(*patsrc, true, true);
		continue;
	}

	if(!nofw) {
		// Do an exact-match search on the forward pattern, just in
		// case we can pick it off early here
		params.setFw(true);
		btf1.setQuery(patsrc->bufa());
		btf1.setOffs(0, plen, plen, plen, plen, plen);
		if(btf1.backtrack()) {
			DONEMASK_SET(patid);
			continue;
		}
	}

	if(!norc) {
		// Set up backtracker with reverse complement
		params.setFw(false);
		// Set up special seed bounds
		if(qs < s) {
			bt1.setOffs(0, 0, (seedMms > 0)? qs5 : qs,
							  (seedMms > 1)? qs5 : qs,
							  (seedMms > 2)? qs5 : qs,
							  (seedMms > 3)? qs5 : qs);
		} else {
			bt1.setOffs(0, 0, (seedMms > 0)? s5 : s,
							  (seedMms > 1)? s5 : s,
							  (seedMms > 2)? s5 : s,
							  (seedMms > 3)? s5 : s);
		}
		bt1.setQuery(patsrc->bufa());
		if(bt1.backtrack()) {
			// If we reach here, then we obtained a hit for case
			// 1R, 2R or 3R and can stop considering this read
			DONEMASK_SET(patid);
			continue;
		}
		// If we reach here, then cases 1R, 2R, and 3R have
		// been eliminated and the read needs further
		// examination
	}

	if(nofw && sink->finishedWithStratum(0)) { // no more exact hits are possible
		DONEMASK_SET(patid);
		continue;
	}
}