UInt8 Array Swift to const char* C

Question

I have the following function

public func encryptWithRSAKey(_ data: String, rsaKeyRef: SecKey, padding: SecPadding) -> [UInt8]? {

    let blockSize = SecKeyGetBlockSize(rsaKeyRef)
    var messageEncrypted = [UInt8](repeating: 0, count: blockSize)
    var messageEncryptedSize = blockSize

    var status: OSStatus!

    status = SecKeyEncrypt(rsaKeyRef, SecPadding.OAEP, data, data.count, &messageEncrypted, &messageEncryptedSize)

    if status != noErr {
        print("\(logClassName): Encryption Error!")
    }

    return messageEncrypted

}

the output is encryptedMessage = [9,43,128...] 128 length

and I have to send the result into a C function

void STDCALL CpProxyAvOpenhomeOrgCredentials1BeginSet(THandle aHandle, const char* aId, const char* aUserName, const char* aPassword, uint32_t aPasswordLen, OhNetCallbackAsync aCallback, void* aPtr)
{
    CpProxyAvOpenhomeOrgCredentials1C* proxyC = reinterpret_cast<CpProxyAvOpenhomeOrgCredentials1C*>(aHandle);
    ASSERT(proxyC != NULL);
    Brh buf_aId(aId);
    Brh buf_aUserName(aUserName);
    Brh buf_aPassword;
    buf_aPassword.Set((const TByte*)aPassword, aPasswordLen);
    FunctorAsync functor = MakeFunctorAsync(aPtr, (OhNetFunctorAsync)aCallback);
    proxyC->BeginSet(buf_aId, buf_aUserName, buf_aPassword, functor);
}

What is the way for encoding messageEncrypted in swift to const char* aPassword in C

I see no C code anywhere!

Antti Haapala
– Antti Haapala

2017-11-12 19:50:00 +00:00
Commented Nov 12, 2017 at 19:50 — Antti Haapala
– Antti Haapala, Commented Nov 12, 2017 at 19:50

Martin R · Accepted Answer · 2017-11-12 19:49:41Z

6

A C function

void cfunc(const char* aPassword, uint32_t aPasswordLen);

is imported to Swift as

public func cfunc(_ aPassword: UnsafePointer<Int8>!, _ aPasswordLen: UInt32)

For an array, withUnsafeBufferPointer() gives you a pointer to the (contiguous) element storage. Due to the different signedness (Int8 vs UInt8), the pointer must be "rebound". Example:

let encryptedMessage: [UInt8] = [9, 43, 128]

encryptedMessage.withUnsafeBufferPointer {
    $0.baseAddress!.withMemoryRebound(to: Int8.self, capacity: encryptedMessage.count) {
        cfunc($0, UInt32(encryptedMessage.count))
    }
}

answered Nov 12, 2017 at 19:49

Martin R

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1 Comment

Reimond Hill Over a year ago

thank you for your answer. and would be the other way back?

Reimond Hill · Accepted Answer · 2017-11-16 09:06:54Z

0

I prefer this approach:

If I have:

let uint8ArrayVar:[UInt8]= [0,3,4,5]

If i want to sent it throught my c function I just do:

cfunc(uint8ArrayVar.map { Int8(bitPattern: $0) })

answered Nov 16, 2017 at 9:06

Reimond Hill

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1 Comment

Martin R Over a year ago

You can do that, but it creates an additional array, which is then passed to the C function.

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