From dbfe85a717b7ac8b9bd30eb51796811c0c651da9 Mon Sep 17 00:00:00 2001
From: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Date: Sun, 26 Oct 2014 10:24:57 -0700
Subject: XPath: Only recognize numeric constant expressions
Numeric and boolean constant expressions in filters are different in that
to evaluate numeric expressions we need a sorted order, but to evaluate
boolean expressions we don't. The previously implemented optimization adds
an extra sorting step for constant boolean filters that will be more expensive
than redundant computations.
Since constant booleans are sort of an edge case, don't do this optimization.
This allows us to simplify apply_predicate_const to only handle numbers.
---
src/pugixml.cpp | 35 +++++++++++++----------------------
1 file changed, 13 insertions(+), 22 deletions(-)
diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index d66f9f9..67591a3 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -8536,6 +8536,7 @@ PUGI__NS_BEGIN
static void apply_predicate_const(xpath_node_set_raw& ns, size_t first, xpath_ast_node* expr, const xpath_stack& stack)
{
assert(ns.size() >= first);
+ assert(expr->rettype() == xpath_type_number);
size_t size = ns.size() - first;
@@ -8543,27 +8544,17 @@ PUGI__NS_BEGIN
xpath_context c(xpath_node(), 1, size);
- if (expr->rettype() == xpath_type_number)
+ double er = expr->eval_number(c, stack);
+
+ if (er >= 1.0 && er <= size)
{
- double er = expr->eval_number(c, stack);
+ size_t eri = static_cast<size_t>(er);
- if (er >= 1.0 && er <= size)
+ if (er == eri)
{
- size_t eri = static_cast<size_t>(er);
-
- if (er == eri)
- {
- xpath_node r = last[eri - 1];
+ xpath_node r = last[eri - 1];
- *last++ = r;
- }
- }
- }
- else
- {
- if (expr->eval_boolean(c, stack))
- {
- last += size;
+ *last++ = r;
}
}
@@ -9781,16 +9772,16 @@ PUGI__NS_BEGIN
if (_right->_type == ast_number_constant && _right->_data.number == 1.0)
_test = predicate_constant_one;
- else if (_right->_type == ast_number_constant || _right->_type == ast_variable)
+ else if (_right->_rettype == xpath_type_number && (_right->_type == ast_number_constant || _right->_type == ast_variable))
_test = predicate_constant;
else if (_right->_rettype != xpath_type_number && _right->is_posinv_expr())
_test = predicate_posinv;
}
- // Replace descendant-or-self::node()/child::foo with descendant::foo
+ // Rewrite descendant-or-self::node()/child::foo with descendant::foo
// The former is a full form of //foo, the latter is much faster since it executes the node test immediately
- // Do a similar kind of replacement for self/descendant/descendant-or-self axes
- // Note that we only replace positionally invariant steps (//foo[1] != /descendant::foo[1])
+ // Do a similar kind of rewrite for self/descendant/descendant-or-self axes
+ // Note that we only rewrite positionally invariant steps (//foo[1] != /descendant::foo[1])
if (_type == ast_step && (_axis == axis_child || _axis == axis_self || _axis == axis_descendant || _axis == axis_descendant_or_self) && _left &&
_left->_type == ast_step && _left->_axis == axis_descendant_or_self && _left->_test == nodetest_type_node && !_left->_right &&
is_posinv_step())
@@ -9803,7 +9794,7 @@ PUGI__NS_BEGIN
_left = _left->_left;
}
- // Replace translate() with constant arguments with a table
+ // Use optimized lookup table implementation for translate() with constant arguments
if (_type == ast_func_translate && _right->_type == ast_string_constant && _right->_next->_type == ast_string_constant)
{
unsigned char* table = translate_table_generate(alloc, _right->_data.string, _right->_next->_data.string);
--
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