变更记录

序号 录入时间 录入人 备注
1 2016-10-13 Alfred Jiang -

方案名称

NSData - NSData 数据压缩与解压缩

关键字

NSData \ 文件 \ 压缩与解压缩

需求场景

  1. 需要对 NSData 进行压缩解压缩存取时

参考链接

  1. CSDN - IOS 压缩与解压字符串(文件) 操作(推荐)

详细内容

NSData+Compresssion.h

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//
//  NSData+Compresssion.h
//  JDiPadNetworking
//
//  Created by viktyz on 16/10/13.
//  Copyright © 2016年 Alfred Jiang. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSData (Compresssion)

- (NSData *)compresssion;
- (NSData *)deCompresssion;

@end

NSData+Compresssion.m

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//
//  NSData+Compresssion.m
//  JDiPadNetworking
//
//  Created by viktyz on 16/10/13.
//  Copyright © 2016年 Alfred Jiang. All rights reserved.
//

#import "NSData+Compresssion.h"
#include <zlib.h>

@implementation NSData (Compresssion)

- (NSData *)compresssion
{
    if ([self length] == 0) return self;
    
    unsigned full_length = (unsigned) self.length;
    unsigned half_length = (unsigned) self.length / 2;
    
    NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length];
    BOOL done = NO;
    int status;
    
    z_stream strm;
    strm.next_in = (Bytef *)self.bytes;
    strm.avail_in = (uInt) self.length;
    strm.total_out = 0;
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    
    if (inflateInit2(&strm, (15+32)) != Z_OK) return nil;
    while (!done)
    {
        // Make sure we have enough room and reset the lengths.
        if (strm.total_out >= decompressed.length)
            [decompressed increaseLengthBy: half_length];
        strm.next_out = decompressed.mutableBytes + strm.total_out;
        strm.avail_out = (uInt) (decompressed.length - strm.total_out);
        
        // Inflate another chunk.
        status = inflate (&strm, Z_SYNC_FLUSH);
        if (status == Z_STREAM_END) done = YES;
        else if (status != Z_OK) break;
    }
    if (inflateEnd (&strm) != Z_OK) return nil;
    
    // Set real length.
    if (done)
    {
        [decompressed setLength: strm.total_out];
        return [NSData dataWithData: decompressed];
    }
    else return nil;
}

- (NSData *)deCompresssion
{
    if ([self length] == 0) return self;
    
    z_stream strm;
    
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    strm.total_out = 0;
    strm.next_in=(Bytef *)self.bytes;
    strm.avail_in = (uInt) self.length;
    
    // Compresssion Levels:
    //   Z_NO_COMPRESSION
    //   Z_BEST_SPEED
    //   Z_BEST_COMPRESSION
    //   Z_DEFAULT_COMPRESSION
    
    if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, (15+16), 8, Z_DEFAULT_STRATEGY) != Z_OK) return nil;
    
    NSMutableData *compressed = [NSMutableData dataWithLength:16384];  // 16K chunks for expansion
    
    do {
        
        if (strm.total_out >= compressed.length)
            [compressed increaseLengthBy: 16384];
        
        strm.next_out = compressed.mutableBytes + strm.total_out;
        strm.avail_out = (uInt) (compressed.length - strm.total_out);
        
        deflate(&strm, Z_FINISH);
        
    } while (strm.avail_out == 0);
    
    deflateEnd(&strm);
    
    [compressed setLength: strm.total_out];
    return [NSData dataWithData:compressed];
}

@end

效果图

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备注

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