Only track contexts if needed

This turns out to be relatively expensive, only allocate memory and test all conditions if needed.
hahnjo · Jul 21, 2019 · c6fe99c · c6fe99c
1 parent 7463087
commit c6fe99c
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Showing 2 changed files with 38 additions and 26 deletions.
diff --git a/pkg/apply.go b/pkg/apply.go
@@ -56,14 +56,18 @@ func applyAppend(r Recipe, modified []byte) []byte {
 func ApplyToInput(r Recipe, input []byte) []byte {
 	inLen := len(input)
 
-	// A rule is active iff there is no begin pattern for a context.
-	deleteActive := make([]bool, len(r.Delete))
-	replaceActive := make([]bool, len(r.Replace))
-	for idx, d := range r.Delete {
-		deleteActive[idx] = (d.Context.BeginRegexp == nil)
-	}
-	for idx, r := range r.Replace {
-		replaceActive[idx] = (r.Context.BeginRegexp == nil)
+	deleteActive := []bool(nil)
+	replaceActive := []bool(nil)
+	if r.hasContext {
+		// A rule is active iff there is no begin pattern for a context.
+		deleteActive = make([]bool, len(r.Delete))
+		replaceActive = make([]bool, len(r.Replace))
+		for idx, d := range r.Delete {
+			deleteActive[idx] = (d.Context.BeginRegexp == nil)
+		}
+		for idx, r := range r.Replace {
+			replaceActive[idx] = (r.Context.BeginRegexp == nil)
+		}
 	}
 
 	modified := make([]byte, 0)
@@ -87,36 +91,38 @@ func ApplyToInput(r Recipe, input []byte) []byte {
 			next++
 		}
 
-		// For each delete and replace, check if the context begins or ends.
-		for idx, d := range r.Delete {
-			c := d.Context
-			if !deleteActive[idx] && c.BeginRegexp != nil && c.BeginRegexp.Match(line) {
-				deleteActive[idx] = true
-			}
-			if deleteActive[idx] && c.EndRegexp != nil && c.EndRegexp.Match(line) {
-				deleteActive[idx] = false
-			}
-		}
-		for idx, sr := range r.Replace {
-			c := sr.Context
-			if !replaceActive[idx] && c.BeginRegexp != nil && c.BeginRegexp.Match(line) {
-				replaceActive[idx] = true
+		if r.hasContext {
+			// For each delete and replace, check if the context begins or ends.
+			for idx, d := range r.Delete {
+				c := d.Context
+				if !deleteActive[idx] && c.BeginRegexp != nil && c.BeginRegexp.Match(line) {
+					deleteActive[idx] = true
+				}
+				if deleteActive[idx] && c.EndRegexp != nil && c.EndRegexp.Match(line) {
+					deleteActive[idx] = false
+				}
 			}
-			if replaceActive[idx] && c.EndRegexp != nil && c.EndRegexp.Match(line) {
-				replaceActive[idx] = false
+			for idx, sr := range r.Replace {
+				c := sr.Context
+				if !replaceActive[idx] && c.BeginRegexp != nil && c.BeginRegexp.Match(line) {
+					replaceActive[idx] = true
+				}
+				if replaceActive[idx] && c.EndRegexp != nil && c.EndRegexp.Match(line) {
+					replaceActive[idx] = false
+				}
 			}
 		}
 
 		// Skip line if it matches a pattern that shall be deleted.
 		for idx, d := range r.Delete {
-			if deleteActive[idx] && d.SearchRegexp.Match(line) {
+			if (!r.hasContext || deleteActive[idx]) && d.SearchRegexp.Match(line) {
 				goto next
 			}
 		}
 
 		// Check if line matches a pattern that shall be replaced.
 		for idx, sr := range r.Replace {
-			if replaceActive[idx] {
+			if !r.hasContext || replaceActive[idx] {
 				line = sr.SearchRegexp.ReplaceAll(line, sr.ReplaceBytes)
 			}
 		}

diff --git a/pkg/recipe.go b/pkg/recipe.go
@@ -37,6 +37,8 @@ type Recipe struct {
 	Delete  []DeleteEntry
 	Replace []ReplaceEntry
 	Append  string
+
+	hasContext bool
 }
 
 func (r *Recipe) Read(filename string) error {
@@ -67,12 +69,14 @@ func (r *Recipe) Compile() error {
 		}
 
 		if d.Context.Begin != "" {
+			r.hasContext = true
 			r.Delete[idx].Context.BeginRegexp, err = regexp.Compile(d.Context.Begin)
 			if err != nil {
 				return err
 			}
 		}
 		if d.Context.End != "" {
+			r.hasContext = true
 			r.Delete[idx].Context.EndRegexp, err = regexp.Compile(d.Context.End)
 			if err != nil {
 				return err
@@ -88,12 +92,14 @@ func (r *Recipe) Compile() error {
 		r.Replace[idx].ReplaceBytes = []byte(sr.Replace)
 
 		if sr.Context.Begin != "" {
+			r.hasContext = true
 			r.Replace[idx].Context.BeginRegexp, err = regexp.Compile(sr.Context.Begin)
 			if err != nil {
 				return err
 			}
 		}
 		if sr.Context.End != "" {
+			r.hasContext = true
 			r.Replace[idx].Context.EndRegexp, err = regexp.Compile(sr.Context.End)
 			if err != nil {
 				return err