Refactor lifted args to use basic string walker

This removes regexp, taking >= 60% less CPU time

caching_parser.go

@@ -2,8 +2,6 @@ package expr
 
 import (
 	"regexp"
-	"strconv"
-	"strings"
 	"sync"
 	"sync/atomic"
 
@@ -13,13 +11,9 @@ import (
 
 var (
 	doubleQuoteMatch *regexp.Regexp
-	replace          = []string{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j"}
+	replace          = []string{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t"}
 )
 
-func init() {
-	doubleQuoteMatch = regexp.MustCompile(`"[^"]*"`)
-}
-
 // NewCachingParser returns a CELParser which lifts quoted literals out of the expression
 // as variables and uses caching to cache expression parsing, resulting in improved
 // performance when parsing expressions.
@@ -40,43 +34,7 @@ type cachingParser struct {
 	misses int64
 }
 
-// liftLiterals lifts quoted literals into variables, allowing us to normalize
-// expressions to increase cache hit rates.
-func liftLiterals(expr string) (string, map[string]any) {
-	// TODO: Optimize this please.  Use strconv.Unquote as the basis, and perform
-	// searches across each index quotes.
-
-	// If this contains an escape sequence (eg. `\` or `\'`), skip the lifting
-	// of literals out of the expression.
-	if strings.Contains(expr, `\"`) || strings.Contains(expr, `\'`) {
-		return expr, nil
-	}
-
-	var (
-		counter int
-		vars    = map[string]any{}
-	)
-
-	rewrite := func(str string) string {
-		if counter > len(replace) {
-			return str
-		}
-
-		idx := replace[counter]
-		if val, err := strconv.Unquote(str); err == nil {
-			str = val
-		}
-		vars[idx] = str
-
-		counter++
-		return VarPrefix + idx
-	}
-
-	expr = doubleQuoteMatch.ReplaceAllStringFunc(expr, rewrite)
-	return expr, vars
-}
-
-func (c *cachingParser) Parse(expr string) (*cel.Ast, *cel.Issues, map[string]any) {
+func (c *cachingParser) Parse(expr string) (*cel.Ast, *cel.Issues, LiftedArgs) {
 	expr, vars := liftLiterals(expr)
 
 	// TODO: ccache, when I have internet.

caching_parser_test.go

@@ -16,7 +16,7 @@ func TestCachingParser_CachesSame(t *testing.T) {
 	var (
 		prevAST    *cel.Ast
 		prevIssues *cel.Issues
-		prevVars   map[string]any
+		prevVars   LiftedArgs
 	)
 
 	t.Run("With an uncached expression", func(t *testing.T) {
@@ -61,7 +61,7 @@ func TestCachingParser_CacheIgnoreLiterals_Unescaped(t *testing.T) {
 	var (
 		prevAST    *cel.Ast
 		prevIssues *cel.Issues
-		prevVars   map[string]any
+		prevVars   LiftedArgs
 	)
 
 	t.Run("With an uncached expression", func(t *testing.T) {

expr_test.go

@@ -70,7 +70,7 @@ func evaluate(b *testing.B, i int, parser TreeParser) error {
 
 func TestEvaluate(t *testing.T) {
 	ctx := context.Background()
-	parser, err := newParser()
+	parser, err := NewTreeParser(NewCachingParser(newEnv()))
 	require.NoError(t, err)
 	e := NewAggregateEvaluator(parser, testBoolEvaluator)
 

lift.go

@@ -0,0 +1,153 @@
+package expr
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type LiftedArgs interface {
+	Get(val string) (any, bool)
+}
+
+// liftLiterals lifts quoted literals into variables, allowing us to normalize
+// expressions to increase cache hit rates.
+func liftLiterals(expr string) (string, LiftedArgs) {
+	// TODO: Lift numeric literals out of expressions.
+	// If this contains an escape sequence (eg. `\` or `\'`), skip the lifting
+	// of literals out of the expression.
+	if strings.Contains(expr, `\"`) || strings.Contains(expr, `\'`) {
+		return expr, nil
+	}
+
+	lp := liftParser{expr: expr}
+	return lp.lift()
+}
+
+type liftParser struct {
+	expr string
+	idx  int
+
+	rewritten *strings.Builder
+
+	// varCounter counts the number of variables lifted.
+	varCounter int
+
+	vars pointerArgMap
+}
+
+func (l *liftParser) lift() (string, LiftedArgs) {
+	l.vars = pointerArgMap{
+		expr: l.expr,
+		vars: map[string]argMapValue{},
+	}
+
+	l.rewritten = &strings.Builder{}
+
+	for l.idx < len(l.expr) {
+		char := l.expr[l.idx]
+
+		l.idx++
+
+		switch char {
+		case '"':
+			// Consume the string arg.
+			val := l.consumeString('"')
+			l.addLiftedVar(val)
+
+		case '\'':
+			val := l.consumeString('\'')
+			l.addLiftedVar(val)
+		default:
+			l.rewritten.WriteByte(char)
+		}
+	}
+
+	return l.rewritten.String(), l.vars
+}
+
+func (l *liftParser) addLiftedVar(val argMapValue) {
+	if l.varCounter >= len(replace) {
+		// Do nothing.
+		str := val.get(l.expr)
+		l.rewritten.WriteString(strconv.Quote(str.(string)))
+		return
+	}
+
+	letter := replace[l.varCounter]
+
+	l.vars.vars[letter] = val
+	l.varCounter++
+
+	l.rewritten.WriteString(VarPrefix + letter)
+}
+
+func (l *liftParser) consumeString(quoteChar byte) argMapValue {
+	offset := l.idx
+	length := 0
+	for l.idx < len(l.expr) {
+		char := l.expr[l.idx]
+
+		// Grab the next char for evaluation.
+		l.idx++
+
+		if char == '\\' && l.peek() == quoteChar {
+			// If we're escaping the quote character, ignore it.
+			l.idx++
+			length++
+			continue
+		}
+
+		if char == quoteChar {
+			return argMapValue{offset, length}
+		}
+
+		// Only now has the length of the inner quote increased.
+		length++
+	}
+
+	// Should never happen:  we should always find the ending string quote, as the
+	// expression should have already been validated.
+	panic(fmt.Sprintf("unable to parse quoted string: `%s` (offset %d)", l.expr, offset))
+}
+
+func (l *liftParser) peek() byte {
+	if (l.idx + 1) >= len(l.expr) {
+		return 0x0
+	}
+	return l.expr[l.idx+1]
+}
+
+// pointerArgMap takes the original expression, and adds pointers to the original expression
+// in order to grab variables.
+//
+// It does this by pointing to the offset and length of data within the expression, as opposed
+// to extracting the value into a new string.  This greatly reduces memory growth & heap allocations.
+type pointerArgMap struct {
+	expr string
+	vars map[string]argMapValue
+}
+
+func (p pointerArgMap) Get(key string) (any, bool) {
+	val, ok := p.vars[key]
+	if !ok {
+		return nil, false
+	}
+	data := val.get(p.expr)
+	return data, true
+}
+
+// argMapValue represents an offset and length for an argument in an expression string
+type argMapValue [2]int
+
+func (a argMapValue) get(expr string) any {
+	data := expr[a[0] : a[0]+a[1]]
+	return data
+}
+
+type regularArgMap map[string]any
+
+func (p regularArgMap) Get(key string) (any, bool) {
+	val, ok := p[key]
+	return val, ok
+}

parser.go

@@ -29,7 +29,7 @@ type TreeParser interface {
 // to provide a caching layer on top of *cel.Env to optimize parsing, as it's
 // the slowest part of the expression process.
 type CELParser interface {
-	Parse(expr string) (*cel.Ast, *cel.Issues, map[string]any)
+	Parse(expr string) (*cel.Ast, *cel.Issues, LiftedArgs)
 }
 
 // EnvParser turns a *cel.Env into a CELParser.
@@ -41,7 +41,7 @@ type envparser struct {
 	env *cel.Env
 }
 
-func (e envparser) Parse(txt string) (*cel.Ast, *cel.Issues, map[string]any) {
+func (e envparser) Parse(txt string) (*cel.Ast, *cel.Issues, LiftedArgs) {
 	ast, iss := e.env.Parse(txt)
 	return ast, iss, nil
 }
@@ -98,8 +98,7 @@ type ParsedExpression struct {
 	// share the same expression.  Using the same expression allows us
 	// to cache and skip CEL parsing, which is the slowest aspect of
 	// expression matching.
-	//
-	Vars map[string]any
+	Vars LiftedArgs
 
 	// Evaluable stores the original evaluable interface that was parsed.
 	Evaluable Evaluable
@@ -330,7 +329,7 @@ type expr struct {
 // It does this by iterating through the expression, amending the current `group` until
 // an or expression is found.  When an or expression is found, we create another group which
 // is mutated by the iteration.
-func navigateAST(nav expr, parent *Node, vars map[string]any) ([]*Node, error) {
+func navigateAST(nav expr, parent *Node, vars LiftedArgs) ([]*Node, error) {
 	// on the very first call to navigateAST, ensure that we set the first node
 	// inside the nodemap.
 	result := []*Node{}
@@ -464,7 +463,7 @@ func peek(nav expr, operator string) []expr {
 // callToPredicate transforms a function call within an expression (eg `>`) into
 // a Predicate struct for our matching engine.  It ahandles normalization of
 // LHS/RHS plus inversions.
-func callToPredicate(item celast.Expr, negated bool, vars map[string]any) *Predicate {
+func callToPredicate(item celast.Expr, negated bool, vars LiftedArgs) *Predicate {
 	fn := item.AsCall().FunctionName()
 	if fn == operators.LogicalAnd || fn == operators.LogicalOr {
 		// Quit early, as we descend into these while iterating through the tree when calling this.
@@ -547,7 +546,7 @@ func callToPredicate(item celast.Expr, negated bool, vars map[string]any) *Predi
 		}
 
 		if aIsVar {
-			if val, ok := vars[strings.TrimPrefix(identA, VarPrefix)]; ok {
+			if val, ok := vars.Get(strings.TrimPrefix(identA, VarPrefix)); ok {
 				// Normalize.
 				literal = val
 				identA = identB
@@ -556,7 +555,7 @@ func callToPredicate(item celast.Expr, negated bool, vars map[string]any) *Predi
 		}
 
 		if bIsVar {
-			if val, ok := vars[strings.TrimPrefix(identB, VarPrefix)]; ok {
+			if val, ok := vars.Get(strings.TrimPrefix(identB, VarPrefix)); ok {
 				// Normalize.
 				literal = val
 				identB = ""

parser_test.go

@@ -997,7 +997,7 @@ func TestParse_LiftedVars(t *testing.T) {
 							Operator: operators.Equals,
 						},
 					},
-					Vars: map[string]any{
+					Vars: regularArgMap{
 						"a": "foo",
 					},
 				},
@@ -1013,7 +1013,7 @@ func TestParse_LiftedVars(t *testing.T) {
 							Operator: operators.Equals,
 						},
 					},
-					Vars: map[string]any{
+					Vars: regularArgMap{
 						"a": "bar",
 					},
 				},
@@ -1029,7 +1029,7 @@ func TestParse_LiftedVars(t *testing.T) {
 							Operator: operators.Equals,
 						},
 					},
-					Vars: map[string]any{
+					Vars: regularArgMap{
 						"a": "bar",
 					},
 				},