Int array to Char array conversion? 1

[ezeke1]

Hello, I'm trying to convert an integer array into an unsigned char array, but my experience with this is limited. I don't want to lose any information during the conversion. Can anyone provide some tips?

 

[sedj]

Well, generally speaking (though it is OS/compiler dependant), an int is 4 bytes, and a char is one byte - so depending on the actual size of your int (ie whether or not it is taking up the whole 4 bytes), you cannot avoid losing data.

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[xwb]

Your problem is not clear and can be interpreted in several ways. What form do you want to convert it?

Say you have an array with

123 -1 99 -5 0

Do you want an array with

0x7B 0xFF 0x63 0xFB 0x00

or do you want an array with

"123 -1 99 -5 0"

or do you want a 2D array with

"123", "-1", "99", "-5", "0"

What do you do with numbers over 128 or less than -127? Do you want it in text form or big endian/little endian? These are just some of the questions that I would ask from such a specification.

 

[ezeke1]

Thank you for the response sedj and xwb

xwb, you bring up a good point.

What I have is an integer array where each element is a number from 0-100. e.g. int array[100] = {1,2,66..etc};

In addition I have an unsigned char array and I would like this array to have "1 2 66..etc" since this type of data format will be easier to send over a network. In other words I guess this should be text form because I do not have to account for a little/big endian issue at this time.

Like sedj pointed out, a int is 4 bytes while a char is only 1 byte. To make matters a little more complicated both arrays are set sizes. So the integer array would be size 178 and the unsigned char array would have to be 178 too.

 

[xwb]

If the range is only 1-100, it will fit in a signed char. You can just transmit it as a series of chars.

 

[DaveSinkula]

Given the value range, wouldn't it just be like this?

void foo(unsigned char *dst, const int *src, size_t size)
{
   while ( size-- )
   {
      *dst++ = *src++;
   }
}

 

[ezeke1]

Thanks all for the help.

Since the int array only has positive numeric values and I wanted the char array to contain the text format of each integer, I was able to make a simple assignment like so,

......includes......
#define size 2

int main()
{
int i;
int a[size] = {1,2};
unsigned char b[size];

for(i=0; i<size; i++)
b = size;
return 0;
}

 

[cpjust]

I wanted the char array to contain the text format of each integer

If you want a number like 100 to be an array of 3 chars "100", that won't work.
Try sprintf() instead.

#define SIZE  50

int main()
{
   int i;
   int a[ SIZE ] = {...}; /* Max int size of 100 */
   char temp[ 4 ];
   char str[ (SIZE * 3) + 2 ];
   memset( str, '\0', sizeof( str ) );

   for ( i = 0; i < SIZE; ++i )
   {
      sprintf( temp, "%d", a[ i ] );
      strcat( str, temp );
      strcat( str, " " );
   }
}

 

[adrstan1]

Just send the integer buffer byte by byte after converting the data to the network host order (using htonl function).
Is there a hidden reason your are not proceeding in the normal way ?

"In other words I guess this should be text form because I do not have to account for a little/big endian issue at this time."

What is the endianess issue if using the htonl / ntohl functions ?