Merge pull request #18 from Teemperor/fix_quote_escaping

Fixed escaped quotes (issue #17)

src/json.cc

@@ -2042,34 +2042,46 @@ Parses a string after opening quotes (\p ") where read.
 */
 std::string json::parser::parseString()
 {
- // get position of closing quotes
- auto quotepos_ = buffer_.find_first_of("\"", pos_);
-
- // if the closing quotes are escaped (character before the quotes is a
- // backslash), we continue looking for the final quotes
- while (quotepos_ != std::string::npos and buffer_[quotepos_ - 1] == '\\')
- {
- quotepos_ = buffer_.find_first_of("\"", quotepos_ + 1);
- }
+ // 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;
+
+ // iterate with pos_ over the whole string
+ 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) {
+
+ 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);
+ }
+ }
 
- // check if closing quotes were found
- if (quotepos_ == std::string::npos)
- {
- error("expected '\"'");
+ // remember if we have an even amount of backslashes before the current character
+ if (currentChar == '\\') {
+ // jump between even/uneven for each backslash we encounter
+ evenAmountOfBackslashes = !evenAmountOfBackslashes;
+ } else {
+ // zero backslashes are also an even number, so as soon as we encounter a non-backslash
+ // the chain of backslashes breaks and we start again from zero
+ evenAmountOfBackslashes = true;
+ }
  }
 
- // store the coordinates of the string for the later return value
- const auto stringBegin = pos_;
- const auto stringLength = quotepos_ - pos_;
-
- // set buffer position to the position behind (+1) the closing quote
- pos_ = quotepos_ + 1;
-
- // read next character
- next();
-
- // return the string value
- return buffer_.substr(stringBegin, stringLength);
+ // we iterated over the whole string without finding a unescaped quote
+ // so the given string is malformed
+ error("expected '\"'");
 }
 
 /*!

test/json_unit.cc

@@ -1621,6 +1621,7 @@ TEST_CASE("Parser")
  // escape characters
  CHECK_THROWS_AS(json::parse("\"\\\""), std::invalid_argument);
  CHECK_NOTHROW(json::parse("\"\\\"\""));
+ CHECK_NOTHROW(json::parse("\"\\\\\""));
 
  // quotes must be closed
  CHECK_THROWS_AS(json::parse("\""), std::invalid_argument);