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Hi,

I have a standard Internet Checksum function as follows:


uint16_t checksum_f(uint16_t *addr, uint32_t length) {


register long sum = 0;

Actually, I think I will make it so that the message is no longer passed in as an argument and I could just get the message inside the function and that way, both options and message will be local...

Can you explain what you mean please?

Thanks.

The way it stands I have little choice as the program I'm communicating with is already made and cannot be changed.

I need to send one buffer in the form:

[<- 12 bytes of header->][<- variable...

Surely I can't use sizeof(message) though...

That's going to be 4 bytes wihch is wrong as the message could be up to 300 bytes long...

int some_function(char *message) {

DATE tx_header;
uint8_t options[64]; // this isn't always totally full (normally only the first two elements) so hence the strlen below:

void* tx_buffer =...

that should be fine because in the tx_header, there is a an offset field and a length_of_message field which tell the receiver where everything is.

hmm, do I actually need to do this then:

void* tx_buffer = malloc(sizeof(tx_header) + strlen(options) + 1 + strlen(message) + 1);

"sizeof(tx_header) + strlen(options) + 1 + strlen(message) + 1"...

Am I right in assuming the "+ 1" is needed because tx_buffer will have a \0 on the end of it?

btw, tx_header is a struct - I made a mistake in my prev post.

corrected to : "DATE tx_header"

Ok, so I need to pass the size of tx_header to function.

Shall I just pass: "sizeof(tx_header)...

Ok, so presumably:

tx_buffer will look like this:

options[0] = 0;
options[1] = 1;

[<-12 bytes of header->][<- 2 bytes of options ->][<-10 bytes of message->]

so what function will get...

Both options and message are strings, so I don't see the problem. I pass in a char line_buf[300] as the argument to the function, so I'd assume strlen would be ok for this?

The point I'm trying to...

hmm slight problem:

I have this kind of thing:


int some_function(char *message) {

DATE tx_header;
uint8_t options[64]; // this isn't always totally full (normally only the first two...

Sorry, that getchar() was meant to be removed. It actually looks like:



do
{
printf("Encrypt (Y / N)");
while ((key = getchar()) != '\n' && key != EOF);

} while (!(key == 'N'...

I've tried this:


do
{
printf("Encrypt (Y / N)");
while ((key = getchar()) != '\n' && key != EOF);
getchar();
} while (!(key == 'N' || key == 'Y'));

char key;


do
{
printf("Encrypt (Y / N)");
key = getchar();

}while(!(key=='N' || key=='Y'));

Is there a way to achieve the same thing without using scanf?

Thanks guys. I'll just use strlen. It seems to work.

I just made up the example in my post. I didn't bother to copy my actual program as it would take too long, so just ignore the lack of return...

Hi,

I have the following:


function (char *message) {

printf("sizeof(message) is: %d", sizeof(message));
printf("strlen(message) is: %d", strlen(message));

Hi,

I want to have the following in my program:

"Encrypt message ? (Y / N):"

If the user enters Y then a boolean variable is set to true and if they enter N a boolean variable is set to...

Thanks all! :)

Could you please give me an example of how you would do this?
Thanks!

#include <sys/socket.h>

ssize_t sendto(int socket, const void *message, size_t length,
int flags, const struct sockaddr *dest_addr,
socklen_t dest_len);

With that definition, I...

Thanks for your amazingly fast reply!

That make perfect sense now.

Do you also know how I could string together the following to make one argument
to pass to sendto() which takes a message in...

Hi,

I just wanted to clear something up regarding structs.

Why is it that I can declare a strut like this:




typedef struct date_header {