实现对字符串进行压缩和解压缩操作 前提需要导入libz.1.2.5.dylib 库

import "BYViewController.h"

#import "zipAndUnzip.h"
 
@interface BYViewController ()
 
@end
 
@implementation BYViewController
 
- (void)viewDidLoad
{undefined
    [super viewDidLoad];
   
 zipAndUnzip *zipAnd = [[zipAndUnzip alloc] init];
    
    NSString *str = @"Hello.madison向显笑";
    NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding(NSUTF16BigEndianStringEncoding);
    NSData *data = [str dataUsingEncoding:enc];
    NSData *dataDeflate = [zipAnd gzipDeflate:data];
    Byte *byte = (Byte *)[dataDeflate bytes];
 
    for (int i=0 ; i<[dataDeflate length]; i++){undefined
    
        NSLog(@"byte = %d",byte[i]);
    }
    
    NSData *adata = [[NSData alloc] initWithBytes:byte length:[dataDeflate length]];
//    NSData *dataInflate =  [zipAnd gzipInflate:adata];
    NSString *aString = [[NSString alloc] initWithData:adata encoding:enc];
    NSLog(@"aString:%@",aString);
 
}
 
@end





@interface zipAndUnzip : NSObject
 
- (NSData *)gzipInflate:(NSData*)data;
- (NSData *)gzipDeflate:(NSData*)data;
 
@end


#import "zipAndUnzip.h"
#import "zlib.h"
 
@implementation zipAndUnzip
 
//解压缩

• (NSData )gzipInflate:(NSData)data
  {
  if ([data length] == 0) return data;

  unsigned full_length = (int)[data length];
  unsigned half_length = (int)[data length] / 2;

  NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length];
  BOOL done = NO;
  int status;

  z_stream strm;
  strm.next_in = (Bytef *)[data bytes];
  strm.avail_in = (int)[data 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] - (uint)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;
  }

//压缩

• (NSData )gzipDeflate:(NSData)data
  {
  if ([data length] == 0) return data;

  z_stream strm;

  strm.zalloc = Z_NULL;
  strm.zfree = Z_NULL;
  strm.opaque = Z_NULL;
  strm.total_out = 0;
  strm.next_in=(Bytef *)[data bytes];
  strm.avail_in = (int)[data 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] - (uint)strm.total_out;
    
    deflate(&strm, Z_FINISH);
  

  } while (strm.avail_out == 0);

  deflateEnd(&strm);

  [compressed setLength: strm.total_out];
  return [NSData dataWithData:compressed];
  }

原文链接：https://blog.csdn.net/u011043997/article/details/25381699