Add a function to escape a query part of url

net/base/escape.cc

Index: net/base/escape.cc
diff --git a/net/base/escape.cc b/net/base/escape.cc
index ab70f1db30187e6a28e09757819d2f307291fd53..1844f64613ad4d715c0d3c7f97677d4c695403bd 100644
--- a/net/base/escape.cc
+++ b/net/base/escape.cc
@@ -24,6 +24,13 @@ inline char IntToHex(int i) {
   return kHexString[i];
 }
 
+inline bool IsHexChar(unsigned char c) {
+  if ((c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F') ||
+      (c >= '0' && c <= '9'))
+    return true;
+  return false;
+}
+
 // A fast bit-vector map for ascii characters.
 //
 // Internally stores 256 bits in an array of 8 ints.
@@ -41,13 +48,17 @@ struct Charmap {
 // to +, otherwise, if spaces are in the charmap, they are converted to
 // %20.
 std::string Escape(const std::string& text, const Charmap& charmap,
-                   bool use_plus) {
+                   bool use_plus, bool keep_escaped = false) {
   std::string escaped;
   escaped.reserve(text.length() * 3);
   for (unsigned int i = 0; i < text.length(); ++i) {
     unsigned char c = static_cast<unsigned char>(text[i]);
     if (use_plus && ' ' == c) {
       escaped.push_back('+');
+    } else if (keep_escaped && '%' == c && i + 2 < text.length() &&
+               IsHexChar(static_cast<unsigned char>(text[i + 1])) &&
+               IsHexChar(static_cast<unsigned char>(text[i + 2]))) {
+      escaped.push_back('%');
     } else if (charmap.Contains(c)) {
       escaped.push_back('%');
       escaped.push_back(IntToHex(c >> 4));
@@ -299,6 +310,13 @@ static const Charmap kExternalHandlerCharmap = {{
   0xffffffffL, 0xffffffffL, 0xffffffffL, 0xffffffffL
 }};
 
+// Everything except alphanumerics, the reserved characters(;/?:@&=+$,), the
+// mark characters(-_.!~*'()).
+static const Charmap kQueryPartCharmap = {{
+  0xffffffffL, 0x5000002dL, 0x78000000L, 0xb8000001L,
+  0xffffffffL, 0xffffffffL, 0xffffffffL, 0xffffffffL
+}};
+
 }  // namespace
 
 std::string EscapeQueryParamValue(const std::string& text, bool use_plus) {
@@ -321,6 +339,10 @@ std::string EscapeExternalHandlerValue(const std::string& text) {
   return Escape(text, kExternalHandlerCharmap, false);
 }
 
+std::string EscapeQueryPart(const std::string& query) {
+  return Escape(query, kQueryPartCharmap, false, true);
+}
+
 void AppendEscapedCharForHTML(char c, std::string* output) {
   AppendEscapedCharForHTMLImpl(c, output);
 }