前段时间开发，碰到了一个问题，请求一个java接口，后台返回的数据原本应该是视频数据流，本来可以直接使用NSData接收就OK，但是出现了以前未曾遇到的dispatch_data_t，因为文件过大的缘故，返回了dispatch_data_t类型的数据。

安排一下：

创建一个NSData类型的类别：

.h

//
//  NSData+PIOAdditions.h
//  LuoJing
//
//  Created by 陈志远 on 2020/11/12.
//  Copyright © 2020 陈志远. All rights reserved.
//
#import <Foundation/Foundation.h>
#import <dispatch/data.h>

NS_ASSUME_NONNULL_BEGIN

@interface NSData (PIOAdditions)


+ (instancetype)dataWithDispatchData:(dispatch_data_t)data;

// returns a dispatch_data_t representation of this object.
// This does not copy the internal bytes
-  (dispatch_data_t)copyDispatchData DISPATCH_RETURNS_RETAINED;


@end

NS_ASSUME_NONNULL_END

.m

//
//  NSData+PIOAdditions.m
//  LuoJing
//
//  Created by 陈志远 on 2020/11/12.
//  Copyright © 2020 陈志远. All rights reserved.
//

#import "NSData+PIOAdditions.h"

// A way to do copyless dispatch data if the dispatch_data_t has just one segment.
@interface _PIOMappedDispatchData : NSData

- (instancetype)initWithData:(dispatch_data_t)data;

@end


@implementation NSData (PIOAdditions)

+ (instancetype)dataWithDispatchData:(dispatch_data_t)data;
{
    return [[_PIOMappedDispatchData alloc] initWithData:data];
}

- (dispatch_data_t)copyDispatchData;
{
    // just incase we are mutable;
    CFDataRef immutableSelf = CFBridgingRetain([self copy]);
    return dispatch_data_create(self.bytes, self.length, dispatch_get_main_queue(), ^{
        CFRelease(immutableSelf);
    });
}

@end

@implementation _PIOMappedDispatchData  {
    dispatch_data_t _data;
    NSUInteger _length;
    const void *_bytes;
}

- (instancetype)initWithData:(dispatch_data_t)data;
{
    const void *buffer;
    size_t size = 0;
    data = dispatch_data_create_map(data, &buffer, &size);
    
    self = [super init];
    if (self != nil) {
        _bytes = buffer;
        _length = size;
        _data = data;
    }
    return self;
}


- (NSUInteger)length;
{
    return _length;
}

- (const void *)bytes;
{
    return _bytes;
}

- (dispatch_data_t)copyDispatchData;
{
    return _data;
}

- (void)dealloc
{
    if (_data != NULL) {
       
    }
}

- (id)copy;
{
    return [[_PIOMappedDispatchData alloc] initWithData:_data];
}

@end

特别提醒 ****

不要去打印返回的Data