Implementing support for reading and writing Unicode escape sequences.

include/json/reader.h

@@ -115,6 +115,10 @@ namespace Json {
       bool decodeString( Token &token );
       bool decodeString( Token &token, std::string &decoded );
       bool decodeDouble( Token &token );
+      bool decodeUnicodeCodePoint( Token &token, 
+                                   Location &current, 
+                                   Location end, 
+                                   unsigned int &unicode );
       bool decodeUnicodeEscapeSequence( Token &token, 
                                         Location &current, 
                                         Location end, 

src/lib_json/json_reader.cpp

@@ -36,6 +36,42 @@ containsNewLine( Reader::Location begin,
    return false;
 }
 
+static std::string codePointToUTF8(unsigned int cp)
+{
+   std::string result;
+   
+   // based on description from http://en.wikipedia.org/wiki/UTF-8
+
+   if (cp <= 0x7f) 
+   {
+      result.resize(1);
+      result[0] = static_cast<char>(cp);
+   } 
+   else if (cp <= 0x7FF) 
+   {
+      result.resize(2);
+      result[1] = static_cast<char>(0x80 | (0x3f & cp));
+      result[0] = static_cast<char>(0xC0 | (0x1f & (cp >> 6)));
+   } 
+   else if (cp <= 0xFFFF) 
+   {
+      result.resize(3);
+      result[2] = static_cast<char>(0x80 | (0x3f & cp));
+      result[1] = 0x80 | static_cast<char>((0x3f & (cp >> 6)));
+      result[0] = 0xE0 | static_cast<char>((0xf & (cp >> 12)));
+   }
+   else if (cp <= 0x10FFFF) 
+   {
+      result.resize(4);
+      result[3] = static_cast<char>(0x80 | (0x3f & cp));
+      result[2] = static_cast<char>(0x80 | (0x3f & (cp >> 6)));
+      result[1] = static_cast<char>(0x80 | (0x3f & (cp >> 12)));
+      result[0] = static_cast<char>(0xF0 | (0x7 & (cp >> 18)));
+   }
+
+   return result;
+}
+
 
 // Class Reader
 // //////////////////////////////////////////////////////////////////
@@ -577,10 +613,9 @@ Reader::decodeString( Token &token, std::string &decoded )
          case 'u':
             {
                unsigned int unicode;
-               if ( !decodeUnicodeEscapeSequence( token, current, end, unicode ) )
+               if ( !decodeUnicodeCodePoint( token, current, end, unicode ) )
                   return false;
-               // @todo encode unicode as utf8.
+               decoded += codePointToUTF8(unicode);
-	       // @todo remember to alter the writer too.
             }
             break;
          default:
@@ -595,6 +630,35 @@ Reader::decodeString( Token &token, std::string &decoded )
    return true;
 }
 
+bool
+Reader::decodeUnicodeCodePoint( Token &token, 
+                                     Location &current, 
+                                     Location end, 
+                                     unsigned int &unicode )
+{
+
+   if ( !decodeUnicodeEscapeSequence( token, current, end, unicode ) )
+      return false;
+   if (unicode >= 0xD800 && unicode <= 0xDBFF)
+   {
+      // surrogate pairs
+      if (end - current < 6)
+         return addError( "additional six characters expected to parse unicode surrogate pair.", token, current );
+      unsigned int surrogatePair;
+      if (*(current++) == '\\' && *(current++)== 'u')
+      {
+         if (decodeUnicodeEscapeSequence( token, current, end, surrogatePair ))
+         {
+            unicode = 0x10000 + ((unicode & 0x3FF) << 10) + (surrogatePair & 0x3FF);
+         } 
+         else
+            return false;
+      } 
+      else
+         return addError( "expecting another \\u token to begin the second half of a unicode surrogate pair", token, current );
+   }
+   return true;
+}
 
 bool 
 Reader::decodeUnicodeEscapeSequence( Token &token, 

src/lib_json/json_writer.cpp

@@ -4,6 +4,8 @@
 #include <stdio.h>
 #include <string.h>
 #include <iostream>
+#include <sstream>
+#include <iomanip>
 
 #if _MSC_VER >= 1400 // VC++ 8.0
 #pragma warning( disable : 4996 )   // disable warning about strdup being deprecated.
@@ -11,6 +13,20 @@
 
 namespace Json {
 
+static bool isControlCharacter(char ch)
+{
+   return ch > 0 && ch <= 0x1F;
+}
+
+static bool containsControlCharacter( const char* str )
+{
+   while ( str ) 
+   {
+      if ( isControlCharacter( *(str++) ) )
+         return true;
+   }
+   return false;
+}
 static void uintToString( unsigned int value, 
                           char *&current )
 {
@@ -95,7 +111,7 @@ std::string valueToString( bool value )
 std::string valueToQuotedString( const char *value )
 {
    // Not sure how to handle unicode...
-   if (strpbrk(value, "\"\\\b\f\n\r\t") == NULL)
+   if (strpbrk(value, "\"\\\b\f\n\r\t") == NULL && !containsControlCharacter( value ))
       return std::string("\"") + value + "\"";
    // We have to walk value and escape any special characters.
    // Appending to std::string is not efficient, but this should be rare.
@@ -132,8 +148,16 @@ std::string valueToQuotedString( const char *value )
 	 // slash is also legal, so I see no reason to escape it.
 	 // (I hope I am not misunderstanding something.)
 	 default:
-	    result += *c;
+	    if ( isControlCharacter( *c ) )
+       {
+          std::ostringstream oss;
+          oss << "\\u" << std::hex << std::uppercase << std::setfill('0') << std::setw(4) << static_cast<int>(*c);
+          result += oss.str();
+       }
+       else
+         result += *c;
       }
+      break;
    }
    result += "\"";
    return result;

test/test_string_unicode_01.expected

@@ -0,0 +1 @@
+.="a"

test/test_string_unicode_01.json

@@ -0,0 +1 @@
+"\u0061"

test/test_string_unicode_02.expected

@@ -0,0 +1 @@
+.="¢"

test/test_string_unicode_02.json

@@ -0,0 +1 @@
+"\u00A2"

test/test_string_unicode_03.expected

@@ -0,0 +1 @@
+.="€"

test/test_string_unicode_03.json

@@ -0,0 +1 @@
+"\u20AC"

test/test_string_unicode_04.expected

@@ -0,0 +1 @@
+.="𝄞"

test/test_string_unicode_04.json

@@ -0,0 +1 @@
+"\uD834\uDD1E"