From a1445d9459458f0837ad90c3f21e6905ead2069e Mon Sep 17 00:00:00 2001
From: Alex Hultman <alexhultman@gmail.com>
Date: Mon, 28 Sep 2020 12:15:01 +0200
Subject: [PATCH] Add QueryParser.h for decoding URI queries by key

---
 src/HttpParser.h  |  10 ++++
 src/QueryParser.h | 113 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 123 insertions(+)
 create mode 100644 src/QueryParser.h

diff --git a/src/HttpParser.h b/src/HttpParser.h
index 7530417..022e65a 100644
--- a/src/HttpParser.h
+++ b/src/HttpParser.h
@@ -29,6 +29,7 @@
 
 #include "BloomFilter.h"
 #include "ProxyParser.h"
+#include "QueryParser.h"
 
 namespace uWS {
 
@@ -108,6 +109,7 @@ public:
         return std::string_view(headers->key.data(), headers->key.length());
     }
 
+    /* Returns the raw querystring as a whole, still encoded */
     std::string_view getQuery() {
         if (querySeparator < (int) headers->value.length()) {
             /* Strip the initial ? */
@@ -117,6 +119,14 @@ public:
         }
     }
 
+    /* Finds and decodes the URI component. */
+    std::string_view getQuery(std::string_view key) {
+        /* Raw querystring including initial '?' sign */
+        std::string_view queryString = std::string_view(headers->value.data() + querySeparator, headers->value.length() - querySeparator);
+
+        return getDecodedQueryValue(key, queryString);
+    }
+
     void setParameters(std::pair<int, std::string_view *> parameters) {
         currentParameters = parameters;
     }
diff --git a/src/QueryParser.h b/src/QueryParser.h
new file mode 100644
index 0000000..9dd3b10
--- /dev/null
+++ b/src/QueryParser.h
@@ -0,0 +1,113 @@
+/*
+ * Authored by Alex Hultman, 2018-2020.
+ * Intellectual property of third-party.
+
+ * 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.
+ */
+
+/* This module implements URI query parsing and retrieval of value given key */
+
+#include <string_view>
+
+namespace uWS {
+
+    /* Takes raw query including initial '?' sign. Will inplace decode, so input will mutate */
+    std::string_view getDecodedQueryValue(std::string_view key, std::string_view rawQuery) {
+
+        /* Can't have a value without a key */
+        if (!key.length()) {
+            return {};
+        }
+
+        /* Start with the whole querystring including initial '?' */
+        std::string_view queryString = rawQuery;
+
+        /* List of key, value could be cached for repeated fetches similar to how headers are, todo! */
+        while (queryString.length()) {
+            /* Find boundaries of this statement */
+            std::string_view statement = queryString.substr(1, queryString.find('&', 1) - 1);
+
+            /* Only bother if first char of key match (early exit) */
+            if (statement.length() && statement[0] == key[0]) {
+                /* Equal sign must be present and not in the end of statement */
+                auto equality = statement.find('=');
+                if (equality != std::string_view::npos && equality != statement.length() - 1) {
+
+                    std::string_view statementKey = statement.substr(0, equality);
+                    std::string_view statementValue = statement.substr(equality + 1);
+
+                    /* String comparison */
+                    if (key == statementKey) {
+
+                        /* Decode value inplace, put null at end if before length of original */
+                        char *in = (char *) statementValue.data();
+
+                        /* Write offset */
+                        int out = 0;
+
+                        /* Walk over all chars until end or null char, decoding in place */
+                        for (int i = 0; in[i] && i < statementValue.length(); i++) {
+                                /* Only bother with '%' */
+                                if (in[i] == '%') {
+                                    /* Do we have enough data for two bytes hex? */
+                                    if (i + 2 >= statementValue.length()) {
+                                        return {};
+                                    }
+
+                                    /* Two bytes hex */
+                                    char hex1 = in[i + 1] - '0';
+                                    if (hex1 > 9) {
+                                        hex1 -= 7;
+                                    }
+
+                                    char hex2 = in[i + 2] - '0';
+                                    if (hex2 > 9) {
+                                        hex2 -= 7;
+                                    }
+
+                                    in[out] = hex1 * 16 + hex2;
+                                    i += 2;
+                                } else {
+                                    /* Is this even a rule? */
+                                    if (in[i] == '+') {
+                                        in[out] = ' ';
+                                    } else {
+                                        in[out] = in[i];
+                                    }
+                                }
+
+                                /* We always only write one char */
+                                out++;
+                        }
+
+                        /* If decoded string is shorter than original, put null char to stop next read */
+                        if (out < statementValue.length()) {
+                            in[out] = 0;
+                        }
+
+                        return statementValue.substr(0, out);
+                    }
+                } else {
+                    /* This querystring is invalid, cannot parse it */
+                    return {};
+                }
+            }
+
+            queryString.remove_prefix(statement.length() + 1);
+        }
+
+        /* Nothing found */
+        return {};
+    }
+
+}
\ No newline at end of file