序列化/反序列化未签名的字符

Question

I'm working on an API for an embedded device, and need to display an image generated (by the API). The screen attached to the device allows me to render bitmaps, with data stored as unsigned char image[] = { 0B00000000, 0B00001111, 0B11111110... } .

What is the easiest way to deserialize a string in whatever format needed?

My approach was to create a stringstream , separate by comma and push to vector<char> . However, the function to render bitmaps will only accept char , and from what I can find online it seems to be quite difficult to convert it. Ideally, I'd rather not use a vector at all, as including it adds several kbs to the project, which is limited in size by both the download speed of the embedded device (firmware is transferred by EDGE) and the onboard storage.

Answer 1

From the comments, it sounds like you want to convert a string composed of a series of "0b00000000" style literals, comma separated, into an array of their actual values. The way I would do this is to:

1. Get the number of bytes in the image (I assume this is known from the string length?).
2. Create a std::vector of unsigned char to hold the results.
3. For each byte in the input, construct a std::bitset from the string value, and then get its actual value.

Here's a code example. Since you have said you'd rather not use vector I have used C-style arrays and strings:

#include <bitset>
#include <cstring>
#include <iostream>
#include <memory>

int main() {
    auto input = "0b00000000,0b00001111,0b11111111";
    auto length = strlen(input);

    // Get the number of bytes from the string length. Each byte takes 10 chars
    // plus a comma separator.
    int size = (length + 1) / 11;

    // Allocate memory to hold the result.
    std::unique_ptr<unsigned char[]> bytes(new unsigned char[size]);

    // Populate each byte individually.
    for (int i = 0; i < size; ++i) {
        // Create the bitset. The stride is 11, and skip the first 2 characters
        // to skip the 0b prefix.
        std::bitset<8> bitset(input + 2 + i * 11, 8);

        // Store the resulting byte.
        bytes[i] = bitset.to_ulong();
    }

    // Now loop back over each byte, and output it to confirm the result.
    for (int i = 0; i < size; ++i) {
        std::cout << "0b" << std::bitset<8>(bytes[i]) << std::endl;
    }
}