From 7f4fcc51f624d56b9729cf88bb4e7d6376419e2f Mon Sep 17 00:00:00 2001
From: Raphael Isemann <teemperor@gmail.com>
Date: Fri, 9 Jan 2015 20:03:18 +0100
Subject: [PATCH] Implemented the JSON spec for string parsing for everything
 but the \uXXXX escaping for unicode

---
 src/json.cc       | 52 +++++++++++++++++++++++++++++++++++------------
 test/json_unit.cc | 33 ++++++++++++++++++++++++++++--
 2 files changed, 70 insertions(+), 15 deletions(-)

diff --git a/src/json.cc b/src/json.cc
index 1a18a9e4..1666b23c 100644
--- a/src/json.cc
+++ b/src/json.cc
@@ -2042,32 +2042,58 @@ Parses a string after opening quotes (\p ") where read.
 */
 std::string json::parser::parseString()
 {
-    // remember the position where the first character of the string was
-    const auto startPos = pos_;
     // true if and only if the amount of backslashes before the current
     // character is even
     bool evenAmountOfBackslashes = true;
 
+    // the result of the parse process
+    std::string result;
+
     // iterate with pos_ over the whole string
-    for (; pos_ < buffer_.size(); pos_++)
-    {
+    for (; pos_ < buffer_.size(); pos_++) {
         char currentChar = buffer_[pos_];
 
-        // currentChar is a quote, so we might have found the end of the string
-        if (currentChar == '"')
-        {
-            // but only if the amount of backslashes before that quote is even
-            if (evenAmountOfBackslashes)
-            {
+        // uneven amount of backslashes means the user wants to escape something
+        if (!evenAmountOfBackslashes) {
+
+            // slash, backslash and quote are copied as is
+            if (   currentChar == '/'
+                || currentChar == '\\'
+                || currentChar == '"') {
+                result += currentChar;
+            } else {
+                // All other characters are replaced by their respective special character
+                if (currentChar == 't') {
+                    result += '\t';
+                } else if (currentChar == 'b') {
+                    result += '\b';
+                } else if (currentChar == 'f') {
+                    result += '\f';
+                } else if (currentChar == 'n') {
+                    result += '\n';
+                } else if (currentChar == 'r') {
+                    result += '\r';
+                } else {
+                    error("expected one of \\,/,b,f,n,r,t behind backslash.");
+                }
+                // TODO implement \uXXXX
+            }
+        } else {
+            if (currentChar == '"') {
+                // currentChar is a quote, so we found the end of the string
+
 
-                const auto stringLength = pos_ - startPos;
                 // set pos_ behind the trailing quote
                 pos_++;
                 // find next char to parse
                 next();
 
-                // return string inside the quotes
-                return buffer_.substr(startPos, stringLength);
+                // bring the result of the parsing process back to the caller
+                return result;
+            } else if (currentChar != '\\') {
+                // all non-backslash characters are added to the end of the result string.
+                // the only backslashes we want in the result are the ones that are escaped (which happens above).
+                result += currentChar;
             }
         }
 
diff --git a/test/json_unit.cc b/test/json_unit.cc
index 7856bdd1..3835e198 100644
--- a/test/json_unit.cc
+++ b/test/json_unit.cc
@@ -1618,10 +1618,39 @@ TEST_CASE("Parser")
         CHECK(json::parse("\"\"") == json(""));
         CHECK(json::parse("\"foo\"") == json("foo"));
 
-        // escape characters
+        // escaping quotes
         CHECK_THROWS_AS(json::parse("\"\\\""), std::invalid_argument);
         CHECK_NOTHROW(json::parse("\"\\\"\""));
-        CHECK_NOTHROW(json::parse("\"\\\\\""));
+
+        // escaping backslashes
+        CHECK(json::parse("\"a\\\\z\"") == json("a\\z"));
+        CHECK(json::parse("\"\\\\\"") == json("\\"));
+        CHECK(json::parse("\"\\\\a\\\\\"") == json("\\a\\"));
+        CHECK(json::parse("\"\\\\\\\\\"") == json("\\\\"));
+
+        // escaping slash
+        CHECK(json::parse("\"a\\/z\"") == json("a/z"));
+        CHECK(json::parse("\"\\/\"") == json("/"));
+
+        // escaping tabs
+        CHECK(json::parse("\"a\\tz\"") == json("a\tz"));
+        CHECK(json::parse("\"\\t\"") == json("\t"));
+
+        // escaping formfeed
+        CHECK(json::parse("\"a\\fz\"") == json("a\fz"));
+        CHECK(json::parse("\"\\f\"") == json("\f"));
+
+        // escaping carriage return
+        CHECK(json::parse("\"a\\rz\"") == json("a\rz"));
+        CHECK(json::parse("\"\\r\"") == json("\r"));
+
+        // escaping backspace
+        CHECK(json::parse("\"a\\bz\"") == json("a\bz"));
+        CHECK(json::parse("\"\\b\"") == json("\b"));
+
+        // escaping newline
+        CHECK(json::parse("\"a\\nz\"") == json("a\nz"));
+        CHECK(json::parse("\"\\n\"") == json("\n"));
 
         // quotes must be closed
         CHECK_THROWS_AS(json::parse("\""), std::invalid_argument);