您可以分块计算MD5校验和,例如在?中有没有一个MD5库不需要同时输入全部内容?。
这是使用Swift的可能实现(现已针对Swift 5更新)
import CommonCrypto
func md5File(url: URL) -> Data? {
let bufferSize = 1024 * 1024
do {
// Open file for reading:
let file = try FileHandle(forReadingFrom: url)
defer {
file.closeFile()
}
// Create and initialize MD5 context:
var context = CC_MD5_CTX()
CC_MD5_Init(&context)
// Read up to `bufferSize` bytes, until EOF is reached, and update MD5 context:
while autoreleasepool(invoking: {
let data = file.readData(ofLength: bufferSize)
if data.count > 0 {
data.withUnsafeBytes {
_ = CC_MD5_Update(&context, $0.baseAddress, numericCast(data.count))
}
return true // Continue
} else {
return false // End of file
}
}) { }
// Compute the MD5 digest:
var digest: [UInt8] = Array(repeating: 0, count: Int(CC_MD5_DIGEST_LENGTH))
_ = CC_MD5_Final(&digest, &context)
return Data(digest)
} catch {
print("Cannot open file:", error.localizedDescription)
return nil
}
}
需要自动释放池来释放所返回的内存 file.readData()
,否则,整个文件(可能很大)将被加载到内存中。感谢Abhi Beckert注意到这一点并提供了实现。
如果您需要摘要作为十六进制编码的字符串,则将返回类型更改为String?
并替换
return digest
通过
let hexDigest = digest.map { String(format: "%02hhx", $0) }.joined()
return hexDigest