uint8_t C的字符串向量

Question

I have a vector with strings that represent bits as follows:

string str1[] = { "0b01100101", "0b01100101", "0b01011101", "0b11001111"}

and I need the exact values added to a uint8_t bits vector:

uint8_t str2[] = { 0b01100101, 0b01100101, 0b01011101, 0b11001111}

The end result should look exactly like above. If anyone has any idea how I could do that I would appreciate it.

Answer 1

There is no standard function to parse binary strings with "0b" prefix, unfortunately.

You can employ good old std::strtoul (1 line to call std::strtoul and 5 lines of error checking):

#include <algorithm>
#include <stdexcept>
#include <cstdlib>
#include <string>

uint8_t binary_string_to_uint8(std::string const& s) {
    if(s.size() != 10 || '0' != s[0] || 'b' != s[1])
        throw std::runtime_error("Invalid bit string format: " + s);
    char* end = 0;
    auto n = std::strtoul(s.c_str() + 2, &end, 2);
    if(end != s.c_str() + s.size())
        throw std::runtime_error("Invalid bit string format: " + s);
    return n;
}

int main() {
    std::string str1[] = { "0b01100001", "0b01100101", "0b01011101", "0b11001111"};
    uint8_t str2[sizeof str1 / sizeof *str1];
    std::transform(std::begin(str1), std::end(str1), std::begin(str2), binary_string_to_uint8);
}

Answer 2

Note that these will likely output nearly the same or the same assembly as an algorithm, so an algorithm like in the other answer is almost always preferred. Nonetheless, here are a few more options using loops:

std::stoul - at least C++11 required. We also do not bounds check here, we assume all strings are >= 2 in size.

std::string str1[] = {"0b01100101", "0b01100101", "0b01011101", "0b11001111"};
const size_t sz = sizeof str1 / sizeof *str1;
uint8_t str2[sz];
for (size_t i = 0; i < sz; ++i)
    str2[i] = static_cast<uint8_t>(std::stoul(&str1[i][2], nullptr, 2));

Since in reality these are most likely going to be variable sized arrays, you may be better off using the actual vector type here.

std::vector<std::string> vs;
// add a bunch of stuff to vs
...

std::vector<uint8_t> vi;
vi.reserve(vs.size());
for (const auto &s : vs)
    vi.push_back(static_cast<uint8_t>(std::stoul(&s[2], nullptr, 2)));