text hex to binary data

strhex.c

int htoi(char h)
{
    return h < 0x3A ? h - 0x30 : h - 0x57; 
}

void strhex(const char* str, uint8_t* out)
{
    for (unsigned i = 0; i < strlen(str) >> 1; i++)
        out[i] = htoi(str[i<<1]) << 4 | htoi(str[i<<1|1]);
}