如何将字符串转换为字节数组

Question

I have a byte array which contain hex value. To store it I encode it to string, and to retrieve it first I decode it to string, how can I convert it to byte array then?

Here is the code :

I create byte array here:

AutoSeededRandomPool prng;
byte key[CryptoPP::AES::MAX_KEYLENGTH];

prng.GenerateBlock(key, sizeof(key));

and then encode it as string with following:

string encoded;
encoded.clear();
StringSource(key, sizeof(key), true,
    new HexEncoder(
        new StringSink(encoded)
    ) // HexEncoder
); // StringSource

Now to get main byte array, first I decode it:

string decodedkey;
StringSource ssk(encoded, true /*pumpAll*/,
new HexDecoder(
    new StringSink(decodedkey)
    ) // HexDecoder
); // StringSource

but I don't know how to reach to byte array.

byte key[CryptoPP::AES::MAX_KEYLENGTH]; 

Answer 1

I think this will work better for you for encoding. Assumes byte is a typedef for unsigned char .

std::stringstream ss;
ss.fill('0');
ss.width(2);

for (int x = 0; x < CryptoPP::AES::MAX_KEYLENGTH; x++)
{
    unsigned int val = (unsigned int)bytes[x];
    ss << std::hex << val;  // writes val out as a 2-digit hex char
}

std::string result = ss.str();  // result is a hex string of your byte array

The above will convert a byte array such as {1,99,200} into "0163C8"

Then to decode the string back to the byte array:

byte key[MAX_KEYLENGTH] = {};
for (int x = 0; x < MAX_KEYLENGTH; x++)
{
    char sz[3];
    sz[0] = result[x*2];
    sz[1] = result[x*2+1];
    sz[2] = '\0';
    unsigned char val = (unsigned char)strtoul(sz, NULL, 10);
    bytes[x] = val;
}

Answer 2

key = (byte *)decodedkey.data();