Perform RemoveNulls & RemoveWhitespace transformations in-place

- Refactored to share implementation.

Author: eduar-hte

src/actions/transformations/remove_nulls.cc

@@ -19,23 +19,8 @@
 namespace modsecurity::actions::transformations {
 
 
-bool RemoveNulls::transform(std::string &val, const Transaction *trans) const {
-    size_t i = 0;
-    std::string transformed_value;
-    transformed_value.reserve(val.size());
-
-    while (i < val.size()) {
-        if (val.at(i) == '\0') {
-            // do nothing; continue on to next char in original val
-        } else {
-            transformed_value += val.at(i);
-        }
-        i++;
-    }
-
-    const auto changed = transformed_value != val;
-    val = transformed_value;
-    return changed;
+bool RemoveNulls::transform(std::string &value, const Transaction *trans) const {
+    return remove_if(value, [](const auto c) { return c == '\0'; });
 }
 
 

src/actions/transformations/remove_nulls.h

@@ -26,6 +26,18 @@ class RemoveNulls : public Transformation {
         : Transformation(action) { }
 
     bool transform(std::string &value, const Transaction *trans) const override;
+
+    template<typename Pred>
+    static bool remove_if(std::string &val, Pred pred) {
+        const auto old_size = val.size();
+
+        val.erase(
+            std::remove_if(
+                val.begin(), val.end(), pred),
+            val.end());
+
+        return val.size() != old_size;
+    }
 };
 
 }  // namespace modsecurity::actions::transformations

src/actions/transformations/remove_whitespace.cc

@@ -15,6 +15,8 @@
 
 #include "remove_whitespace.h"
 
+#include "remove_nulls.h"
+
 namespace modsecurity::actions::transformations {
 
 
@@ -23,30 +25,18 @@ RemoveWhitespace::RemoveWhitespace(const std::string &action)
     this->action_kind = 1;
 }
 
-bool RemoveWhitespace::transform(std::string &val, const Transaction *trans) const {
-    std::string transformed_value;
-    transformed_value.reserve(val.size());
-
-    size_t i = 0;
+bool RemoveWhitespace::transform(std::string &value, const Transaction *trans) const {
     const char nonBreakingSpaces = 0xa0;
     const char nonBreakingSpaces2 = 0xc2;
 
-    // loop through all the chars
-    while (i < val.size()) {
+    auto pred = [](const auto c) {
         // remove whitespaces and non breaking spaces (NBSP)
-        if (std::isspace(static_cast<unsigned char>(val[i]))
-            || (val[i] == nonBreakingSpaces)
-            || val[i] == nonBreakingSpaces2) {
-            // don't copy; continue on to next char in original val
-        } else {
-            transformed_value += val.at(i);
-        }
-        i++;
-    }
-
-    const auto changed = transformed_value != val;
-    val = transformed_value;
-    return changed;
+        return std::isspace(static_cast<unsigned char>(c))
+            || c == nonBreakingSpaces
+            || c == nonBreakingSpaces2;
+    };
+
+    return RemoveNulls::remove_if(value, pred);
 }