苹果提供的常用的数据压缩算法LZMA、ZLIB、LZ4等；
这三种算法也是苹果建议的，可跨平台使用；
定义如下：
/* Commonly-available encoders */
COMPRESSION_LZ4 = 0x100, // available starting OS X 10.11, iOS 9.0
COMPRESSION_ZLIB = 0x205, // available starting OS X 10.11, iOS 9.0
COMPRESSION_LZMA = 0x306, // available starting OS X 10.11, iOS 9.0
COMPRESSION_LZ4_RAW = 0x101, // available starting OS X 10.11, iOS 9.0
/* Apple-specific encoders */
COMPRESSION_LZFSE = 0x801, // available starting OS X 10.11, iOS 9.0
适用于有大文件数据上传下载，节省流量可以考虑使用；
使用说明：
1. 需要引用头文件
#include "compression.h"
2. 数据压缩示例：
- (void)testCompress{
NSData *src = [NSData dataWithContentsOfFile:@"/Users/cocoajin/Desktop/src.txt"];
NSLog(@"src: %ld",src.length);
uint8_t *dstBuffer = (uint8_t *)malloc(src.length);
memset(dstBuffer, 0, src.length);
size_t compressResultLength = compression_encode_buffer(dstBuffer, src.length, [src bytes], src.length, NULL, COMPRESSION_LZMA);
if (compressResultLength > 0) {
NSData *newData = [NSData dataWithBytes:dstBuffer length:compressResultLength];
[newData writeToFile:@"/Users/cocoajin/Desktop/compress.data" atomically:YES];
NSLog(@"com: %ld",compressResultLength);
NSLog(@"com: %.2f",(src.length-compressResultLength)/(float)src.length);
}else{
NSLog(@"compress error!");
}
free(dstBuffer);
}
3. 数据解压缩示例：
- (void)testDeCompress{
NSData *src = [NSData dataWithContentsOfFile:@"/Users/cocoajin/Desktop/compress.data"];
NSLog(@"src: %ld",src.length);
uint8_t *dstBuffer = (uint8_t *)malloc(1024*1024*10);
memset(dstBuffer, 0, src.length);
size_t decompressLen = compression_decode_buffer(dstBuffer,1024*1024*10,src.bytes,src.length,NULL,COMPRESSION_LZMA);
if (decompressLen > 0) {
NSData *newData = [NSData dataWithBytes:dstBuffer length:decompressLen];
[newData writeToFile:@"/Users/cocoajin/Desktop/decompress.txt" atomically:YES];
NSLog(@"com: %ld",decompressLen);
}else{
NSLog(@"decompressLen error!");
}
free(dstBuffer);
}
4. 实际测对一个1.9M的txt小说文件压缩，压缩以后大小为0.8m，压缩效果还是很明显的；