Copy 80 bit hex number from char array to uint16_t vector or array

Question

Say I have a text file containing the 80bit hex number

0xabcdef0123456789abcd

My C++ program reads that using fstream into a char array called buffer. But then I want to store it in a uint16_t array such that:

uint16_t * key = {0xabcd, 0xef01, 0x2345, 0x6789, 0xabcd}

I have tried several approaches, but I continue to get decimal integers, for instance:

const std::size_t strLength = strlen(buffer);
std::vector<uint16_t> arr16bit((strLength / 2) + 1);

for (std::size_t i = 0; i < strLength; ++i)
{
    arr16bit[i / 2] <<= 8;
    arr16bit[i / 2] |= buffer[i];
}

Yields:

arr16bit = {24930, 25444, 25958, 12337, 12851}

There must be an easy way to do this that I'm just not seeing.

Here is the full solution I came up with based on the comments:

int hex_char_to_int(char c) {
    if (int(c) < 58) //numbers
        return c - 48;
    else if (int(c) < 91) //capital letters
        return c - 65 + 10;
    else if (int(c) < 123) //lower case letters
        return c - 97 + 10;
}
uint16_t ints_to_int16(int i0, int i1, int i2, int i3) {
    return (i3 * 16 * 16 * 16) + (i2 * 16 * 16) + (i1 * 16) + i0;
}

void readKey() {
    const int bufferSize = 25;
    char buffer[bufferSize] = { NULL };
    ifstream* pStream = new ifstream("key.txt");
    if (pStream->is_open() == true)
    {
        pStream->read(buffer, bufferSize);
    }
    cout << buffer << endl;
    const size_t strLength = strlen(buffer);
    int* hex_to_int = new int[strLength - 2];
    for (int i = 2; i < strLength; i++) {
        hex_to_int[i - 2] = hex_char_to_int(buffer[i]);
    }
    cout << endl;
    uint16_t* key16 = new uint16_t[5];
    int j = 0;
    for (int i = 0; i < 5; i++) {
        key16[i] = ints_to_int16(hex_to_int[j++], hex_to_int[j++], hex_to_int[j++], hex_to_int[j++]);
        cout << "0x" << hex << key16[i] << " ";
    }
    cout << endl;
}

This outputs:

0xabcdef0123456789abcd

0xabcd 0xef01 0x2345 0x6789 0xabcd