Shifted value with NSString * and void*

Question

I want to pass to a method a void* from a NSString get in a NSTextField so I did like this :

(It is to add a new password to the keychain access on OS X)

 NSString *password = [passwordTextField stringValue];
UInt32 passwordlength = (UInt32) [password length];


void *mypassword = malloc(passwordlength);
mypassword = &password;

StorePasswordKeychain(mypassword, passwordlength);

The problem is that if passwordTextField returns "hello" for example, i get back in the keychain "xhell". the x is random..

I think that it is a basic problem but i can't figure how to solve it ..

Answer 1

You should not assume how NSString object store it internal representation. In your case, first byte probably occupied with string length or other NSString internal data. Use following code instead:

NSString *password = [passwordTextField stringValue];
void *mypassword = (void *)[password UTF8String];
StorePasswordKeychain(mypassword, strlen(mypassword));

If you need different encoding, use cStringUsingEncoding: method instead of UTF8String.