CODEWITHSUNDEEP
c
user2305811
user2305811

Reputation: 1

concatenating char to int type

Been racking my brain for the past few hours but i need help. Pretty much trying to write a C model for a blocking cache to be used in a RTL design. I've defined the cache line in C as an array of 'char' types to make it byte-addressable. Only difficulty is I can't for the life of me figure how to concatenate four bytes (chars) into a 32bit 'int' type to be returned. I've tried everything I could think of using strcat, strncat, strcpy, etc but no luck. strcat returns the proper value when I the char array is populated with actual characters, but it doesn't behave as desired when numbers are use (strcat only returns the first element instead of the entire char array). Example code:

unsigned char aa[4] = {0};
char testet[2] = {1,0};
printf(" aa[0] = %d \n", aa[0]);
printf(" aa[1] = %d \n", aa[1]);
printf(" aa[2] = %d \n", aa[2]);
printf(" aa[3] = %d \n", aa[3]);
printf(" aaconcat as a 32b word is %u \n", *strncat(aa, testet,2));
printf(" aaconcat as a 32b word is %u \n", *strncat(aa, testet,1));
printf(" aa[0] = %d \n", aa[0]);
printf(" aa[1] = %d \n", aa[1]);
printf(" aa[2] = %d \n", aa[2]);
printf(" aa[3] = %d \n", aa[3]);

Returns:

aaconcat as a 32b word is 1 
aaconcat as a 32b word is 1 
aa[0] = 1 
aa[1] = 2 
aa[2] = 1 
aa[3] = 0

Though I'm expecting {testet[0],testet[1],testet[0]} = 131330.

Upvotes: 0

Views: 4467

Answers (1)

user1167662
user1167662

Reputation: 1265

if you are trying to concatenate the actual bits, which I suspect you may be trying to do given your expected result from {testet[0],testet[1],testet[0]} = 131330, then try something like this to concatenate the chars:

This assumes the chars you want to concatenate are stored in unsigned char chararr[4].

long int chars_in_int = 0;
for (int i = 0; i < 4; i++ ) {
    chars_in_int << 8;    /* redundant on first loop */
    chars_in_int += chararr[i];
}

This will place the chars with the lowest index in chararr in the most significant bits of chars_in_int.

Upvotes: 1

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