iOS对大文件MD5摘要性能测试

最近接到了一个需求,里面需要对文件进行md5摘要.从网上搜索到了两个还可以的代码片段,为了更好的判断该使用哪个,这里对这两种摘要方式做了时间和内存的测试.

一 测试环境

1.四种大小的文件:1m,10,20m,30m3.工具:xcode84.设备:iphone4s,ios8;iphone5,ios10;iphone6,ios9;iphone6s,ios10

二. 两种方法代码

使用filehandle

+ (NSString *)md5WithFilePath:(NSString *)path {    NSFileHandle *handle = [NSFileHandle fileHandleForReadingAtPath:path];    if( handle== nil ) {        return nil;    }    CC_MD5_CTX md5;    CC_MD5_Init(&md5);    BOOL done = NO;    while(!done)    {        NSData* fileData = [handle readDataOfLength: 256 ];        CC_MD5_Update(&md5, [fileData bytes], (CC_LONG)[fileData length]);        if( [fileData length] == 0 ) done = YES;    }    unsigned char digest[CC_MD5_DIGEST_LENGTH];    CC_MD5_Final(digest, &md5);    NSString* s = [NSString stringWithFormat: @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",                   digest[0], digest[1],                   digest[2], digest[3],                   digest[4], digest[5],                   digest[6], digest[7],                   digest[8], digest[9],                   digest[10], digest[11],                   digest[12], digest[13],                   digest[14], digest[15]];    return s;}

使用readstream

// In bytes#define FileHashDefaultChunkSizeForReadingData 256// FunctionCFStringRef FileMD5HashCreateWithPath(CFStringRef filePath,                                      size_t chunkSizeForReadingData) {    // Declare needed variables    CFStringRef result = NULL;    CFReadStreamRef readStream = NULL;    // Get the file URL    CFURLRef fileURL =    CFURLCreateWithFileSystemPath(kCFAllocatorDefault,                                  (CFStringRef)filePath,                                  kCFURLPOSIXPathStyle,                                  (Boolean)false);    if (!fileURL) goto done;    // Create and open the read stream    readStream = CFReadStreamCreateWithFile(kCFAllocatorDefault,                                            (CFURLRef)fileURL);    if (!readStream) goto done;    bool didSucceed = (bool)CFReadStreamOpen(readStream);    if (!didSucceed) goto done;    // Initialize the hash object    CC_MD5_CTX hashObject;    CC_MD5_Init(&hashObject);    // Make sure chunkSizeForReadingData is valid    if (!chunkSizeForReadingData) {        chunkSizeForReadingData = FileHashDefaultChunkSizeForReadingData;    }    // Feed the data to the hash object    bool hasMoreData = true;    while (hasMoreData) {        uint8_t buffer[chunkSizeForReadingData];        CFIndex readBytesCount = CFReadStreamRead(readStream,                                                  (UInt8 *)buffer,                                                  (CFIndex)sizeof(buffer));        if (readBytesCount == -1) break;        if (readBytesCount == 0) {            hasMoreData = false;            continue;        }        CC_MD5_Update(&hashObject,                      (const void *)buffer,                      (CC_LONG)readBytesCount);    }    // Check if the read operation succeeded    didSucceed = !hasMoreData;    // Compute the hash digest    unsigned char digest[CC_MD5_DIGEST_LENGTH];    CC_MD5_Final(digest, &hashObject);    // Abort if the read operation failed    if (!didSucceed) goto done;    // Compute the string result    char hash[2 * sizeof(digest) + 1];    for (size_t i = 0; i < sizeof(digest); ++i) {        snprintf(hash + (2 * i), 3, "%02x", (int)(digest[i]));    }    result = CFStringCreateWithCString(kCFAllocatorDefault,                                       (const char *)hash,                                       kCFStringEncodingUTF8);done:    if (readStream) {        CFReadStreamClose(readStream);        CFRelease(readStream);    }    if (fileURL) {        CFRelease(fileURL);    }    return result;}

为方便比较,两个方法每次相同的每次读取大小256k

三 耗时比较

耗时测试方法:

1.采用dispatch_benchmark,对每个文件md5 100次,取平均值
2.示例代码:

“`
- (IBAction)M_md5_10M:(id)sender {
__block NSString *md5 = nil;

uint64_t t2 = dispatch_benchmark(_count, ^{    @autoreleasepool {        NSString *path = [self.paths objectAtIndex:1];        md5 = [self.class md5WithFilePath:path];    }});NSLog(@"[md5 10m file:] Avg. Runtime: %llu ns,md5:%@", t2,md5);

}
“`

耗时测试结果

handle耗时:

readstream耗时

结论:从上面两张图片可以看出,使用readsteam方法耗时平均比filehandle少50%左右,在iphone6和iphone6s上表现更为明显

四 . 内存消耗

内存测试方法

采用xcode memory 测试工具

测试结果

iphone4s, 第一个为handle,第二个为readstream:

iphone5, 第一个为handle,第二个为readstream:

iphone6, 第一个为handle,第二个为readstream:

iphone6s, 第一个为handle,第二个为readstream:
)

对比结果:readstream在内存上比handle消耗平均也少50%以上.

结论

readstream方法在时间和内存消耗上明显优于filehandle,平均都有50%的性能优势.因此选用readstream方法对大文件进行md5摘要.