c# - Converting 4 bytes (from String format) into one u32. C or C#

Question

I am attempting to convert some text from a text field to a(n) u32 value. An example would be that I enter in string format (to represent a 32-bit integer), "0x30323436", and the output in string format would be "0246". I am trying to do this in C#, but I can use C as well. Thank you.

Answer 1

これはあなたが望むことをするはずです：

string ParseWeirdFormat(string input)
{
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < input.Length; i += 2)
    {
        string hex = input.Substring(i, 2);
        int value = Convert.ToInt32(hex, 16);
        char c = (char)value;
        sb.Append(c);
    }
    return sb.ToString();
}

Answer 2

これが、C が C# よりも優れている理由です。

char in[] = "0x30323436";
char out[5] = {0};
sscanf( in, "0x%02x%02x%02x%02x", &out[0], &out[1], &out[2], &out[3] );

Answer 3

C (C99 以上) の場合:

#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static bool cvt(const char* in, char* out)
{
    if (strlen(in) != 8)
        return false;

    char* end;
    long n = strtol(in, &end, 16);
    if (end == in || *end)
        return false;

    for(int i = 0; i < 4; i++)
    {
        unsigned char c = n >> ((3-i)*8);
        if(!isdigit(c))
            return false;
        out[i] = c;
    }
    return true;
}

int main(int argc, char** argv)
{
    char out[4];

    if ( argc <= 1 || !cvt(argv[1], out) )
    {
        fprintf(stderr, "usage: %s hex-ASCII-encoding-of-four-digit-string\n", argv[0]);
        return 1;
    }

    printf("%.4s\n", out);

    return 0;
}