NSMutableData删除、插入数据

NSMutableData的定义中关于数据操作的方法如下：

@interface NSMutableData (NSExtendedMutableData)

- (void)appendBytes:(const void *)bytes length:(NSUInteger)length;
- (void)appendData:(NSData *)other;
- (void)increaseLengthBy:(NSUInteger)extraLength;
- (void)replaceBytesInRange:(NSRange)range withBytes:(const void *)bytes;
- (void)resetBytesInRange:(NSRange)range;
- (void)setData:(NSData *)data;
- (void)replaceBytesInRange:(NSRange)range withBytes:(nullable const void *)replacementBytes length:(NSUInteger)replacementLength;

@end

通过观察方法名称，怎么没有删除和插入数据的操作呢？？？难道不支持吗？ 或者利用replace可以实现delete？好吧，我们来实验一下吧。

NSData *strData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding];
NSMutableData *data = [NSMutableData data];
[data appendData:strData];
NSLog(@"data length:%ld",data.length);

// delete
[data replaceBytesInRange:NSMakeRange(0, 4) withBytes:NULL length:0];
NSLog(@"data length:%ld",data.length);

//insert
[data replaceBytesInRange:NSMakeRange(0, 0) withBytes:strData.bytes length:strData.length];
NSLog(@"data length:%ld",data.length);

输出如下：

data length:8
data length:4
data length:12

so，果然如此。原来通过replace可以实现delete和insert功能。

ps: 发现了另一种删除的方式：

NSData *payloadData = [_receiveBuffer subdataWithRange:range];
uint32_t remainLen = (int)[_receiveBuffer length] - pduLen;
range = NSMakeRange(pduLen, remainLen);
NSData *remainData = [_receiveBuffer subdataWithRange:range];
[_receiveBuffer setData:remainData];