json流编写叠加器，拥有个可变data对象
1 @interface SBJsonStreamWriterAccumulator : NSObject <SBJsonStreamWriterDelegate>
2
3 @property (readonly, copy) NSMutableData* data;
4
5 @end
具体实现：
1 @implementation SBJsonStreamWriterAccumulator
2
3 @synthesize data;
4
5 - (id)init {
6 self = [super init];
7 if (self) {
8 data = [[NSMutableData alloc] initWithCapacity:8096u];
9 }
10 return self;
11 }
12
13
14 #pragma mark SBJsonStreamWriterDelegate
15
16 //实现SBJsonStreamWriterDelegate协议，把二进制数据添加到data
17
18 - (void)writer:(SBJsonStreamWriter *)writer appendBytes:(const void *)bytes length:(NSUInteger)length {
19 [data appendBytes:bytes length:length];
20 }
21
22 @end