如何从 NSData 中拆分字节？

Question

所以..我已经从服务器加密数据需要解密，这样我才能得到完整的响应JSON。问题是我需要拆分前 16 个字节的数据以获得用于解密的 IV，其余字节是加密数据。我尝试了以下方法：

NSData *wholeData = [[NSData alloc] initWithBase64EncodedString:@"IYSaYh92saFT5t/ueQQtlTaFT1oW33FXPLDUsRMATBLUrY/6Z1VGK1KFmyeRwHpbi85T7ZNzDQAl5v8cu60DcJLwVQDI6KdwbmCq0+L62IM7Ixw60+G8gTkm+6+MLtyE" options:0];

NSData *d1 = [wholeData subdataWithRange:NSMakeRange(0, 16)];
NSData *d2 = [wholeData subdataWithRange:NSMakeRange(17, wholeData.length)];

NSData *enc = d2;
NSData *key = [[NSData alloc] initWithBase64EncodedString:@"alskd81039aisdf/tusd8341iasldkjfY=" options:0];
NSData *enciv = d1;

NSData *decrypted = [FBEncryptorAES decryptData:enc key:key iv:enciv];

然后我得到以下错误：

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSConcreteData subdataWithRange:]: range {17, 96} exceeds data length 96'

我该如何解决我的问题？

Answer 1

NSData *d2 = [wholeData subdataWithRange:NSMakeRange(17, wholeData.length - 17)];

Answer 2

你可以试试这个

 NSData* blob;
    NSUInteger length = [blob length];
    NSUInteger chunkSize = 100 * 1024;
    NSUInteger offset = 0;
    do {
        NSUInteger thisChunkSize = length - offset > chunkSize ? chunkSize : length - offset;
        NSData* chunk = [NSData dataWithBytesNoCopy:(char *)[blob bytes] + offset
                                             length:thisChunkSize
                                       freeWhenDone:NO];
        offset += thisChunkSize;
        // do something with chunk
    } while (offset < length);

如何从 NSData 中拆分字节？

How to split bytes from NSData?

ios

objective-c

iphone

byte

nsdata