(Unicode C++) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

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#include <CkPublicKeyW.h>
#include <CkBinDataW.h>
#include <CkRsaW.h>

void ChilkatSample(void)
    {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkPublicKeyW pubKey;

    // Load the public key from an PEM file:
    bool success = pubKey.LoadFromFile(L"pubKey.pem");
    if (success != true) {
        wprintf(L"%s\n",pubKey.lastErrorText());
        return;
    }

    // Load the data of the original file that was signed.
    CkBinDataW bdFileData;
    success = bdFileData.LoadFile(L"in.dat");

    // Load the signature.
    CkBinDataW bdSig;
    success = bdSig.LoadFile(L"signature.sig");

    CkRsaW rsa;

    // Import the public key into the RSA component:
    success = rsa.ImportPublicKeyObj(pubKey);
    if (success != true) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    // OpenSSL uses big-endian.
    rsa.put_LittleEndian(false);

    success = rsa.VerifyBd(bdFileData,L"sha256",bdSig);
    if (success != true) {
        wprintf(L"%s\n",rsa.lastErrorText());
        wprintf(L"The signature was invalid.\n");
        return;
    }

    wprintf(L"The signature was verified.\n");
    }