Fixed a problem generaitng JSON with NaN value

There was a problem where the JSON generator would allow NaN value of
NSDecimalNumber to be written into JSON. This was due to the fact that
NSDecimalNumber is a subclass of NSNumber, and stringValue of NaN value
is represented as "NaN", which is invalid in JSON. JSON data with NaN
value can cause many parsers to fail (including YAJL), as this is not
supported by JSON.

Classes/YAJLGen.m

@@ -118,10 +118,14 @@ - (void)bool:(BOOL)b {
 }
 
 - (void)number:(NSNumber *)number {
-  NSString *s = [number stringValue];
-  unsigned int length = [s lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
-  const char *c = [s UTF8String];
-  yajl_gen_number(gen_, c, length);
+  if ([number isEqualToNumber:[NSDecimalNumber notANumber]]) {
+    yajl_gen_null(gen_);
+  } else {
+    NSString *s = [number stringValue];
+    unsigned int length = [s lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
+    const char *c = [s UTF8String];
+    yajl_gen_number(gen_, c, length);
+  }
 }
 
 - (void)string:(NSString *)s {

Tests/NSObjectTest.m

@@ -21,7 +21,7 @@ @implementation NSObjectTest
 - (void)testDictionary {
   NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                         [NSArray arrayWithObjects:@"arrayValue1", [NSNumber numberWithBool:YES], [NSNumber numberWithBool:NO], [NSNull null], 
-                         [NSNumber numberWithInteger:1], [NSNumber numberWithDouble:234234.234234], nil], @"key2",
+                         [NSNumber numberWithInteger:1], [NSNumber numberWithDouble:234234.234234], [NSDecimalNumber notANumber], nil], @"key2",
                         nil];
 
   NSString *JSONString = [dict yajl_JSONStringWithOptions:YAJLGenOptionsBeautify indentString:@"  "];

Tests/Samples/gen_expected1.json

@@ -5,6 +5,7 @@
     false,
     null,
     1,
-    234234.234234
+    234234.234234,
+    null
   ]
 }

Tests/Samples/gen_expected2.json

@@ -1 +1 @@
-{"key2":["arrayValue1",true,false,null,1,234234.234234]}
+{"key2":["arrayValue1",true,false,null,1,234234.234234,null]}

Tests/YAJLGenTest.m

@@ -26,6 +26,7 @@ - (void)testGen1 {
   [gen null];
   [gen number:[NSNumber numberWithInteger:1]];
   [gen number:[NSNumber numberWithDouble:234234.234234]];
+  [gen number:[NSDecimalNumber notANumber]];
   [gen endArray];
   [gen endDictionary];
   NSString *buffer = [gen buffer];
@@ -48,6 +49,7 @@ - (void)testGen2 {
   [gen null];
   [gen number:[NSNumber numberWithInteger:1]];
   [gen number:[NSNumber numberWithDouble:234234.234234]];
+  [gen number:[NSDecimalNumber notANumber]];
   [gen endArray];
   [gen endDictionary];
   NSString *buffer = [gen buffer];
@@ -63,7 +65,7 @@ - (void)testGen2 {
 - (void)testGenObject1 {
   NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
    [NSArray arrayWithObjects:@"arrayValue1", [NSNumber numberWithBool:YES], [NSNumber numberWithBool:NO], [NSNull null], 
-    [NSNumber numberWithInteger:1], [NSNumber numberWithDouble:234234.234234], nil], @"key2",
+    [NSNumber numberWithInteger:1], [NSNumber numberWithDouble:234234.234234], [NSDecimalNumber notANumber], nil], @"key2",
    nil];
 
   YAJLGen *gen = [[YAJLGen alloc] initWithGenOptions:YAJLGenOptionsBeautify indentString:@"  "];