iOS gzip解压

1. 导入libz库（如：libz 1.2.5.dylib）

2. 引入头文件

#import "zlib.h"

3. 实现解压（输入输出都为NSData对象）

-(NSData *)uncompressZippedData:(NSData *)compressedData
{
    if ([compressedData length] == 0) return compressedData;

    unsigned full_length = [compressedData length];

    unsigned half_length = [compressedData length] / 2;
    NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length];
    BOOL done = NO;
    int status;
    z_stream strm;
    strm.next_in = (Bytef *)[compressedData bytes];
    strm.avail_in = [compressedData 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];
        }
        // chadeltu 加了(Bytef *)
        strm.next_out = (Bytef *)[decompressed mutableBytes] + strm.total_out;
        strm.avail_out = [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;
    }
}

使用样例：

// gzip解压，mapFilePath为待解压文件路径
NSData *dataInitial = [NSData dataWithContentsOfFile:mapFilePath];	// 解压前
NSData *dataUncompressed = [self uncompressZippedData:dataInitial];	// 解压后

参考博客：

在iPhone开发中实现解压缩gzip