www form encoder / decoder.

Constructs application/x-www-form-urlencoded forms in a string from a
set of key / value pairs.  Also, provides a method to parse a form into
a vector of key / value pairs.

PiperOrigin-RevId: 248589839

Author: smiles

app/rest/www_form_url_encoded.cc

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+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "app/rest/www_form_url_encoded.h"
+
+#include <string.h>
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#include "app/rest/util.h"
+
+namespace firebase {
+namespace rest {
+
+void WwwFormUrlEncoded::Add(const char* key, const char* value) {
+  if (output_->length()) {
+    *output_ += "&";
+  }
+  *output_ += util::EncodeUrl(key);
+  *output_ += "=";
+  *output_ += util::EncodeUrl(value);
+}
+
+std::vector<WwwFormUrlEncoded::Item> WwwFormUrlEncoded::Parse(
+    const char* form) {
+  std::vector<Item> form_data;
+  const char* current_field = form;
+  const char* end_of_form = form + strlen(form);
+  while (current_field < end_of_form) {
+    const char* end_of_field =
+        std::find_if(current_field, end_of_form, [](char c) {
+          return c == '&' || c == '\n' || c == '\r' || c == '\t' || c == ' ';
+        });
+    if (end_of_field != current_field) {
+      const char* separator = std::find(current_field, end_of_field, '=');
+      if (separator != end_of_field) {
+        form_data.push_back(
+            Item(util::DecodeUrl(std::string(current_field, separator)),
+                 util::DecodeUrl(std::string(separator + 1, end_of_field))));
+      }
+    }
+    current_field = end_of_field + 1;
+  }
+  return form_data;
+}
+
+}  // namespace rest
+}  // namespace firebase

app/rest/www_form_url_encoded.h

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+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FIREBASE_APP_CLIENT_CPP_REST_WWW_FORM_URL_ENCODED_H_
+#define FIREBASE_APP_CLIENT_CPP_REST_WWW_FORM_URL_ENCODED_H_
+
+#include <string>
+#include <vector>
+
+namespace firebase {
+namespace rest {
+
+// Constructs and parses strings of key/value pairs in the
+// x-www-form-urlencoded format.
+// util::Initialize() must be called before this can be used.
+class WwwFormUrlEncoded {
+ public:
+  // Form item.
+  struct Item {
+    Item() {}
+    Item(const string& key_, const string& value_) : key(key_), value(value_) {}
+
+    std::string key;
+    std::string value;
+  };
+
+ public:
+  // Initialize with a string to output constructed form data.
+  explicit WwwFormUrlEncoded(std::string* output) : output_(output) {}
+
+  // Add a key / value pair to the form.
+  void Add(const char* key, const char* value);
+
+  // Add a key / value pair using a form item.
+  void Add(const Item& item) { Add(item.key.c_str(), item.value.c_str()); }
+
+  // Get the form data string constructed by successive calls to Add().
+  const std::string& form_data() const { return *output_; }
+
+  // Parse a x-www-form-urlencoded encoded form into a list of key value pairs.
+  static std::vector<Item> Parse(const char* form);
+
+ private:
+  std::string* output_;
+};
+
+}  // namespace rest
+}  // namespace firebase
+
+#endif  // FIREBASE_APP_CLIENT_CPP_REST_WWW_FORM_URL_ENCODED_H_