I have an array uint8_t arr[512] and I need to store a string, IP address and a 32digit number in this array. So I thought of defining another array of strings as below.
uint8_t *ch[] = {
"abcd",
"1.1.1.1",
"123456782341223344445"
};
Then do a memcpy into the arr[512]. Is this OK? I think I may not be able to retrieve the IP address from the arr. Any other ideas please. Thanks for your time.
If you think about how an array of pointers is stored in memory, you would understand why it can't be done.
Your string array looks like this:
+-------+-------+-------+ | ch[0] | ch[1] | ch[2] | +-------+-------+-------+ | | | | | v | | "abcd" | v | "1.1.1.1" v "123456782341223344445"
So if you do a memcpy from the ch array you only copy the pointers, not the actual strings.
You can of course copy each string in the array separately into the destination array, but then it's no different than doing it to separate and unrelated strings.
arr[512]?strcpy and strlen are good here).
sprintf(arr, "%s %s %s", ch[0], ch[1], ch[2]); in single step. (Yes but Joachim Pileborg's suggestion is more better if you don't know number of strings ("ip") you wish to copy from ch[] and you will need a loop)snprintf is a better choice, to not risk buffer overflows.I don't think that's a good idea. Better use structures.
struct info
{
char* name;
char* address;
char* number; // or other type
}
You can use pragma pack if you want to copy full struct to the array. Or use something like copy to combine them.
And if you want to copy it to static array you need to check name length.
You can do so if you memcpy() the strings ch[0] to ch[2] including ithe terminating \0. You can't just memcpy() the complete array ch. To retrieve the second string from within arr you can use strlen() or memchr():
char *ip = arr + strlen(arr) + 1;
or
char *ip = memchr( arr, '\0', sizeof( arr ) ) + 1;
Personally I would prefere the first option, as it is easier to adpopt to get the third string.
Beware that uint8_t arr[512] is not the same kind of type as uint8_t *ch[].
The first one is an array of 512 bytes.
The second is an array of pointers to bytes.
You may have serious problems. So please hep us and tell us what you really want to do.
arr[512]. So when I try to retrieve them a[0] must be a a[1] = b a[2] = c a[3]=1 a[4]=1 a[5]=1 a[6]=1 a[7]=1 and so on...
char* str[]and charstr[][]and how both stores in memory? to know how*ch[]stored in memory, memcopy needsourcein continues memory whereas its not.uint8_t*instead ofchar*?structthat contains a string, a 32Bit-Integer for the IP-adress and a second string for the 32-digit number?structinstead ofarr[512]orch[]? can you please elaborate.