获取md5的高效的方法

来源：互联网发布：网络排名优化软件编辑：程序博客网时间：2024/06/05 15:29

CFStringRef 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 =4096;

}

// 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,

(constvoid *)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,

(constchar *)hash,

kCFStringEncodingUTF8);

done:

if (readStream) {

CFReadStreamClose(readStream);

CFRelease(readStream);

}

if (fileURL) {

CFRelease(fileURL);

}

return result;

}