CODEWITHSUNDEEP
cstring
Janni Nevill
Janni Nevill

Reputation: 37

string concatenation with "\x" hex character escape

How do I create a string that contain multiple '\x41' or with arbitrary '\xnn' by copy from some give string for example:

char * string1 = "4141414141414141"; or char * string2 = "bde54d7ee10a2122";

And I would like my char * string3 become something like: char * string3 = "\xbd\xe5\x4d\x7e\xe1\x0a\x21\x22"; or char * string3 = "\x41\x41\x41\x41\x41\x41\x41\x41";

Here is the code that I am trying to do, but it doesn't work.

char * string1 = "4141414141414141";
char c;
char * slash_x = "\\x";
int len = strlen(string1);
char * string3 = (char *) malloc(9);
for (i = 0; i < len; i++) {
    if (0 == i % 2) {
        printf("start\n");
        j = i;
        strcat(salt_empty, slash_x);
        c = string[j];
        printf("%c\n", c);
        strncat(salt_empty, &c, 1);
        j++;
        c = string[j];
        printf("%c\n", c);
        strncat(salt_empty, &c, 1);
    }
}
printf("%s\n", string3);

So the output with string3 will be "\x41\x41\x41\x41\x41\x41\x41\x41" instead of "AAAAAAAA" at console.

How could I fix the code in order to get "AAAAAAAA"

If the string1 is "bde54d7ee10a2122", then the string3 output at console would be ��M~ !"

Upvotes: 1

Views: 575

Answers (3)

alk
alk

Reputation: 70971

You want:

char string1[] = {0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0};

Upvotes: 1

chqrlie
chqrlie

Reputation: 144989

You cannot convert the string by re-interpreting it from its source form. Use this instead (inefficient, but simple):

char *string1 = "4141414141414141";
int i, j, len = strlen(string1) & ~1;
char string3[len / 2 + 1];
for (i = j = 0; i < len; i += 2, j++) {
    char buf[3];
    memcpy(buf, string1 + i, 2);
    buf[2] = '\0';
    string3[j] = strtol(buf, NULL, 16);
}
string3[j] = '\0';
printf("%s\n", string3);

Upvotes: 3

1201ProgramAlarm
1201ProgramAlarm

Reputation: 32727

For each pair of characters in the source string, determine the hex value of each character in the pair, combine them to come up with the encoded character, then store the result in your destination string.

Upvotes: 0

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