reading byte by byte from memory

Hi,
I had one small query.
I 'm coping data from an unsigned short to a char*.

code is

#include<stdio.h>

int main(void){
unsigned short type=0xFE10;
char * buf = char(*) malloc(512);

memset(buf,0,512);

//copying 2 bytes of type which is 0xFE10 to buf
memcpy(buf,type,2);
}

here, how to I cehck if the data has been successfully copied or not.
the actual purpose is....... this is a client prog and I wanna send
the value of buf at the server.
At server I wanna check if the value received is 0xFE10 pr not.

Can anyone please help me with this? 'm new to memory level C prog.

Thanks in advance.

re: reading byte by byte from memory

On Sep 5, 9:55*pm, Ashit Vora <a.k.v...@gmail.comwrote:Here is the actual code 'm using... If it makes the picture more
clear.

Client's piece of code.

//total_buf_size is the sum of header plus data
total_buf_size=10;
buf =(char*) malloc (total_buf_size);

if(buf==NULL){
printf("Malloc Failed\n");
}

memset(buf,0, total_buf_size);
memcpy(buf,&type,2);
memcpy(&buf[2],&offset,4);
memcpy(&buf[6],&data_length,4);



/*now sending the data BYTE AT A TIME*/
for(i=0;i<10;i++){
if(send(client_sock,&buf[i],1,0)==-1){
perror("send");
exit(1);
}
}

/**************************************************/
Server's piece of Code is:

for(i=0;i<10;i++){
if(recv(new_fd,&buf[i],1, 0)==-1){
perror("receive");
exit(1);
}
printf("%02x \t",buf[i]);
}
printf("\n");
memcpy(&type,buf,2);
buf+=2;
memcpy(&offset,buf,4);
buf+=4;
memcpy(&data_length,buf,4);

printf("TYPE: %s\n",(char*)type);
if(type == 0xFE10)
printf("RECEIVED");
else
printf("NOT RECEIVED");
}



NOTE: type at client was unsigned short type=0xFE10


Thanks

re: reading byte by byte from memory

Martin Ambuhl wrote:.... snip ...I gather you don't consider his code exemplary? :-)

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.

re: reading byte by byte from memory

Ashit Vora wrote:BEGIN new.c output

buf[0] is 0x16
buf[1] is 0x254

END new.c output


Feel free to ask any questions about new.c:

/* BEGIN new.c */

#include <stdio.h>
#include <string.h>

int main(void)
{
unsigned short type = 0xFE10;
unsigned char buf[sizeof type] = {0};
unsigned byte;
/*
** copying 2 bytes of type which is 0xFE10 to buf
*/
memcpy(buf, &type, sizeof type != 1 ? 2 : 1);
puts("BEGIN new.c output\n");
for (byte = 0; byte != sizeof type; ++byte) {
printf("buf[%u] is 0x%u\n", byte, buf[byte]);
}
puts("\nEND new.c output");
return 0;
}

/* END new.c */


--
pete

re: reading byte by byte from memory

pete wrote:That's not really what I wanted.
I'll try again:

BEGIN new.c output

buf[0] is 0x10
buf[1] is 0xfe

END new.c output




/* BEGIN new.c */

#include <stdio.h>
#include <string.h>

int main(void)
{
unsigned short type = 0xfe10;
unsigned char buf[sizeof type] = {0};
unsigned byte;
/*
** copying all bytes of type which is 0xfe10 to buf
*/
memcpy(buf, &type, sizeof type);
puts("BEGIN new.c output\n");
for (byte = 0; byte != sizeof type; ++byte) {
printf("buf[%u] is 0x%x\n", byte, buf[byte]);
}
puts("\nEND new.c output");
return 0;
}

/* END new.c */

--
pete

re: reading byte by byte from memory

Ashit Vora wrote:
If buf_size is really only 10 bytes, you could just use char buf[10];
You seem to be filling a struct with values of 2,4 and 4 bytes. You might be
better off defining:

struct {
unsigned short sig;
int offset, data_length;
} header = {0xFE10, 0, 0};

BUT only if you can persuade your compiler not to leave a 2-byte gap between
..sig and .offset.

Then instead of memcpy:

header.offset=offset;
header.data_length=data_length;
Accessing buf (now header) a byte at a time is a little more tricky:

for (i=0; i<sizeof(header); ++i){
if send(client_sock, ((char*)&header+i),1,0)...

(Why can't you send all bytes at once? If you can do that, you can also send
0xFE10 as a 2-byte block, and offset and data_length as two 4-byte blocks,
you don't need the struct or buf)

Do something similar in the server code and check whether .sig or .sig is
0xFE10

--
Bartc

re: reading byte by byte from memory

On Sep 6, 5:55*am, Ashit Vora <a.k.v...@gmail.comwrote:
the cast is syntactically wrong and unnecessary
why wouldn't it be? use printf(), or memcmp() or a debugger
....... isn't standard punctuation
"to the server"? For socket stuff try comp.unix.programmer (I think).
memcmp()?
I'm not sure what "memory level programming" is


--
Nick Keighley