ios 将 NSData 转换为字符串？
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Convert NSData to String?
提问by Zach
I am storing a openssl private Key EVP_PKEY as nsdata. For this I am serializing into a byte stream using the code below
我将 openssl 私钥 EVP_PKEY 存储为 nsdata。为此，我使用下面的代码序列化为字节流
unsigned char *buf, *p;
int len;
len = i2d_PrivateKey(pkey, NULL);
buf = OPENSSL_malloc(len);
p = buf;
i2d_PrivateKey(pkey, &p);
where pkey is of type EVP_PKEY. Then I am storing the bytes from buffer 'p' as an NSData using the line given below
其中 pkey 的类型为 EVP_PKEY。然后我使用下面给出的行将缓冲区“p”中的字节存储为 NSData
NSData *keydata = [NSData dataWithBytes:P length:len];
Now I am converting it to a NSString using the code given below but when i print it into console its giving some other characters.
现在我使用下面给出的代码将它转换为 NSString，但是当我将它打印到控制台时，它给出了一些其他字符。
NSString *content =[ NSString stringWithCString:[keydata bytes] encoding:NSUTF8StringEncoding];
Could someone help?
有人可以帮忙吗？
Basically I want to store the EVP_PKEY into a sqlite database
基本上我想将 EVP_PKEY 存储到 sqlite 数据库中
am I on the right track? Thanks.
我在正确的轨道上吗？谢谢。
回答by louiscoquio
Objective-C
目标-C
You can use (see NSString Class Reference)
您可以使用（见NSString类参考）
- (id)initWithData:(NSData *)data encoding:(NSStringEncoding)encoding
Example:
例子：
NSString *myString = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
Remark: Please notice the NSDatavalue must be valid for the encoding specified (UTF-8 in the example above), otherwise nilwill be returned:
备注：请注意该NSData值必须对指定的编码（上例中的 UTF-8）有效，否则nil将返回：
Prior Swift 3.0
之前的 Swift 3.0
String(data: yourData, encoding: NSUTF8StringEncoding)
Swift 3.0
斯威夫特 3.0
String(data: yourData, encoding: .utf8)
回答by pierre23
Prior Swift 3.0 :
Swift 3.0 之前的版本：
String(data: yourData, encoding: NSUTF8StringEncoding)
For Swift 4.0:
对于 Swift 4.0：
String(data: yourData, encoding: .utf8)
回答by aspergillusOryzae
I believe your "P" as the dataWithBytes param
我相信你的“P”作为 dataWithBytes 参数
NSData *keydata = [NSData dataWithBytes:P length:len];
should be "buf"
应该是“buf”
NSData *keydata = [NSData dataWithBytes:buf length:len];
since i2d_PrivateKey puts the pointer to the output buffer p at the end of the buffer and waiting for further input, and buf is still pointing to the beginning of your buffer.
因为 i2d_PrivateKey 将指向输出缓冲区 p 的指针放在缓冲区的末尾并等待进一步的输入，而 buf 仍指向缓冲区的开头。
The following code works for me where pkey is a pointer to an EVP_PKEY:
以下代码对我有用，其中 pkey 是指向 EVP_PKEY 的指针：
unsigned char *buf, *pp;
int len = i2d_PrivateKey(pkey, NULL);
buf = OPENSSL_malloc(len);
pp = buf;
i2d_PrivateKey(pkey, &pp);
NSData* pkeyData = [NSData dataWithBytes:(const void *)buf length:len];
DLog(@"Private key in hex (%d): %@", len, pkeyData);
You can use an online converter to convert your binary data into base 64 (http://tomeko.net/online_tools/hex_to_base64.php?lang=en) and compare it to the private key in your cert file after using the following command and checking the output of mypkey.pem:
您可以使用在线转换器的二进制数据转换成基64（http://tomeko.net/online_tools/hex_to_base64.php?lang=en在你的证书文件中使用以下命令后），并把它比作私钥和检查 mypkey.pem 的输出：
openssl pkcs12 -in myCert.p12 -nocerts -nodes -out mypkey.pem
I referenced your question and this EVP function sitefor my answer.
我参考了你的问题和这个 EVP 功能站点作为我的答案。
回答by Travis M.
Swift 3:
斯威夫特 3：
String(data: data, encoding: .utf8)
回答by Billy
A simple way to convert arbitrary NSData to NSString is to base64 encode it.
任意的NSData转换为NSString的一个简单的方法是Base64编码它。
NSString *base64EncodedKey = [keydata base64EncodedStringWithOptions: NSDataBase64Encoding64CharacterLineLength];
You can then store it into your database for reuse later. Just decode it back to NSData.
然后，您可以将其存储到您的数据库中以供以后重用。只需将其解码回 NSData。
回答by Alexander Volkov
Swift:
迅速：
String(data: data!, encoding: NSUTF8StringEncoding)
