/**
* Checks if the specified step will never yield results.
*
* @param rt root value
* @param s index of step
* @return {@code true} if steps will never yield results
*/
private boolean emptyPath(final Value rt, final int s) {
final Step step = axisStep(s);
if (step == null) return false;
final Axis axis = step.axis;
if (s == 0) {
// first location step:
if (root instanceof CAttr) {
// @.../child:: / @.../descendant::
if (axis == CHILD || axis == DESC) return true;
} else if (root instanceof Root
|| root instanceof CDoc
|| rt != null && rt.type == NodeType.DOC) {
if (axis == SELF || axis == ANCORSELF) {
if (step.test != Test.NOD && step.test != Test.DOC) return true;
} else if (axis == CHILD || axis == DESC) {
if (step.test == Test.DOC || step.test == Test.ATT) return true;
} else if (axis == DESCORSELF) {
if (step.test == Test.ATT) return true;
} else {
return true;
}
}
} else {
// remaining steps:
final Step last = axisStep(s - 1);
if (last == null) return false;
// .../self:: / .../descendant-or-self::
if (axis == SELF || axis == DESCORSELF) {
if (step.test == Test.NOD) return false;
// @.../..., text()/...
if (last.axis == ATTR && step.test.type != NodeType.ATT
|| last.test == Test.TXT && step.test != Test.TXT) return true;
if (axis == DESCORSELF) return false;
// .../self::
final QNm name = step.test.name, lastName = last.test.name;
if (lastName == null
|| name == null
|| lastName.local().length == 0
|| name.local().length == 0) return false;
// ...X/...Y
return !name.eq(lastName);
}
// .../following-sibling:: / .../preceding-sibling::
if (axis == FOLLSIBL || axis == PRECSIBL) return last.axis == ATTR;
// .../descendant:: / .../child:: / .../attribute::
if (axis == DESC || axis == CHILD || axis == ATTR)
return last.axis == ATTR
|| last.test == Test.TXT
|| last.test == Test.COM
|| last.test == Test.PI
|| axis == ATTR && step.test == Test.NSP;
// .../parent:: / .../ancestor::
if (axis == PARENT || axis == ANC) return last.test == Test.DOC;
}
return false;
}
/**
* Converts descendant to child steps.
*
* @param qc query context
* @param rt root value
* @return original or new expression
*/
private Expr children(final QueryContext qc, final Value rt) {
// skip if index does not exist or is out-dated, or if several namespaces occur in the input
final Data data = rt.data();
if (data == null || !data.meta.uptodate || data.nspaces.globalNS() == null) return this;
Path path = this;
final int sl = steps.length;
for (int s = 0; s < sl; s++) {
// don't allow predicates in preceding location steps
final Step prev = s > 0 ? axisStep(s - 1) : null;
if (prev != null && prev.preds.length != 0) break;
// ignore axes other than descendant, or numeric predicates
final Step curr = axisStep(s);
if (curr == null || curr.axis != DESC || curr.has(Flag.FCS)) continue;
// check if child steps can be retrieved for current step
ArrayList<PathNode> nodes = pathNodes(data, s);
if (nodes == null) continue;
// cache child steps
final ArrayList<QNm> qnm = new ArrayList<>();
while (nodes.get(0).parent != null) {
QNm nm = new QNm(data.elemNames.key(nodes.get(0).name));
// skip children with prefixes
if (nm.hasPrefix()) return this;
for (final PathNode p : nodes) {
if (nodes.get(0).name != p.name) nm = null;
}
qnm.add(nm);
nodes = PathSummary.parent(nodes);
}
qc.compInfo(OPTCHILD, steps[s]);
// build new steps
int ts = qnm.size();
final Expr[] stps = new Expr[ts + sl - s - 1];
for (int t = 0; t < ts; t++) {
final Expr[] preds = t == ts - 1 ? ((Preds) steps[s]).preds : new Expr[0];
final QNm nm = qnm.get(ts - t - 1);
final NameTest nt =
nm == null ? new NameTest(false) : new NameTest(nm, Kind.NAME, false, null);
stps[t] = Step.get(info, CHILD, nt, preds);
}
while (++s < sl) stps[ts++] = steps[s];
path = get(info, root, stps);
break;
}
// check if all steps yield results; if not, return empty sequence
final ArrayList<PathNode> nodes = pathNodes(qc);
if (nodes != null && nodes.isEmpty()) {
qc.compInfo(OPTPATH, path);
return Empty.SEQ;
}
return path;
}
/**
* Converts descendant to child steps.
*
* @param ctx query context
* @param data data reference
* @return path
*/
Expr children(final QueryContext ctx, final Data data) {
// skip path check if no path index exists, or if it is out-of-date
if (!data.meta.uptodate || data.nspaces.globalNS() == null) return this;
Path path = this;
for (int s = 0; s < steps.length; ++s) {
// don't allow predicates in preceding location steps
final Step prev = s > 0 ? axisStep(s - 1) : null;
if (prev != null && prev.preds.length != 0) break;
// ignore axes other than descendant, or numeric predicates
final Step curr = axisStep(s);
if (curr == null || curr.axis != DESC || curr.has(Flag.FCS)) continue;
// check if child steps can be retrieved for current step
ArrayList<PathNode> pn = pathNodes(data, s);
if (pn == null) continue;
// cache child steps
final ArrayList<QNm> qnm = new ArrayList<>();
while (pn.get(0).par != null) {
QNm nm = new QNm(data.tagindex.key(pn.get(0).name));
// skip children with prefixes
if (nm.hasPrefix()) return this;
for (final PathNode p : pn) {
if (pn.get(0).name != p.name) nm = null;
}
qnm.add(nm);
pn = PathSummary.parent(pn);
}
ctx.compInfo(OPTCHILD, steps[s]);
// build new steps
int ts = qnm.size();
final Expr[] stps = new Expr[ts + steps.length - s - 1];
for (int t = 0; t < ts; ++t) {
final Expr[] preds = t == ts - 1 ? ((Preds) steps[s]).preds : new Expr[0];
final QNm nm = qnm.get(ts - t - 1);
final NameTest nt =
nm == null ? new NameTest(false) : new NameTest(nm, Mode.LN, false, null);
stps[t] = Step.get(info, CHILD, nt, preds);
}
while (++s < steps.length) stps[ts++] = steps[s];
path = get(info, root, stps);
break;
}
// check if the all children in the path exist; don't test with namespaces
if (data.nspaces.size() == 0) {
LOOP:
for (int s = 0; s < path.steps.length; ++s) {
// only verify child steps; ignore namespaces
final Step st = path.axisStep(s);
if (st == null || st.axis != CHILD) break;
if (st.test.mode == Mode.ALL || st.test.mode == null) continue;
if (st.test.mode != Mode.LN) break;
// check if one of the addressed nodes is on the correct level
final int name = data.tagindex.id(st.test.name.local());
for (final PathNode pn : data.paths.desc(name, Data.ELEM)) {
if (pn.level() == s + 1) continue LOOP;
}
ctx.compInfo(OPTPATH, path);
return Empty.SEQ;
}
}
return path;
}
/**
* Checks if the location path contains steps that will never yield results.
*
* @param stps step array
* @param ctx query context
*/
void voidStep(final Expr[] stps, final QueryContext ctx) {
for (int l = 0; l < stps.length; ++l) {
final Step s = axisStep(l);
if (s == null) continue;
final Axis sa = s.axis;
if (l == 0) {
if (root instanceof CAttr) {
// @.../child:: / @.../descendant::
if (sa == CHILD || sa == DESC) {
ctx.compInfo(WARNDESC, root);
return;
}
} else if (root instanceof Root
|| root instanceof Value && ((Value) root).type == NodeType.DOC
|| root instanceof CDoc) {
if (sa != CHILD
&& sa != DESC
&& sa != DESCORSELF
&& (sa != SELF && sa != ANCORSELF || s.test != Test.NOD && s.test != Test.DOC)) {
ctx.compInfo(WARNDOC, root, sa);
return;
}
}
} else {
final Step ls = axisStep(l - 1);
if (ls == null) continue;
final Axis lsa = ls.axis;
boolean warning = true;
if (sa == SELF || sa == DESCORSELF) {
// .../self:: / .../descendant-or-self::
if (s.test == Test.NOD) continue;
// @.../..., text()/...
warning =
lsa == ATTR && s.test.type != NodeType.ATT
|| ls.test == Test.TXT && s.test != Test.TXT;
if (!warning) {
if (sa == DESCORSELF) continue;
// .../self::
final QNm n0 = ls.test.name;
final QNm n1 = s.test.name;
if (n0 == null || n1 == null || n0.local().length == 0 || n1.local().length == 0)
continue;
// ...X/...Y
warning = !n1.eq(n0);
}
} else if (sa == FOLLSIBL || sa == PRECSIBL) {
// .../following-sibling:: / .../preceding-sibling::
warning = lsa == ATTR;
} else if (sa == DESC || sa == CHILD || sa == ATTR) {
// .../descendant:: / .../child:: / .../attribute::
warning =
lsa == ATTR
|| ls.test == Test.TXT
|| ls.test == Test.COM
|| ls.test == Test.PI
|| sa == ATTR && s.test == Test.NSP;
} else if (sa == PARENT || sa == ANC) {
// .../parent:: / .../ancestor::
warning = ls.test == Test.DOC;
}
if (warning) {
ctx.compInfo(WARNSELF, s);
return;
}
}
}
}