C/C++ :: Add 8 Bits - Return The Character
Oct 10, 2014
I'm working on an assignment where I have to read an image in the PPM format. This format consists of a header that contains the parameters and the rest is raw bits.
I have to work with a modified PPM image that contains a secret message. This message is stored in the first X number of bytes. To decode a single character I would have to look at the lowest level bit of 8 bytes and return that as a character, then repeat this for the length of the message.
The code below is what I have so far, but I do not get the expected output but instead I get smiley-faces.... or other ASCII characters depending on the shift.
char buffer = 0;
int MsgSize =(size*8);
int nRead = 0;
printf("The secret message is displayed below:
");
for(i; i<MsgSize; i++) {
[Code] ....
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Jan 3, 2015
The task is to return the number of bits set to true.Here is my code:
Code:
int cardinalityBS(PBitSet _this) {
int s, counter = 0;
for(s = 0; s < 31; s++) {
counter += _this->bits & 1;
_this->bits <<= 1;
}
return counter;
}
[code]....
The code is not working, since whenever I set _this->bits to a number, it returns me the wrong result.
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Nov 5, 2014
I need understanding the logic behind this function. The function is supposed to "Return a pointer to the character at the index given" . For example, what exactly are we declaring at "(char * const c, int index)"? where does "index" come from or equal to in the body of the function?
Code:
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char * GetValueAtIndex(char * const c, int index)
{
int i = 0;
char *p = c;
while (i++ != index)
p++;
return p;
}
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May 14, 2013
I am working on a project where I need to retrive a double number and store 8 bits of the number in one field and the other 16 bits in another field. the code below gives me an error.
lata= lat>>8;
latb = (lat & 0xff);
The error states that & and >> are illegal for double. With this in mind, can I use these on a double. If not what can I do to achieve what I am trying to do?
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Sep 14, 2014
I keep getting this warning message and I do not know how to fix it. Is it because I'm using char to instead of strings to replace all 't' with 'lp'?
#include<iostream>
#include<string>
#include <stdio.h>
using namespace std;
char * scanf(char * a) {
[code]....
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Jul 25, 2012
Double values are stored in text file. 23.5 36.8 34.2 ... My teacher told me to read them character by character and then make words, like i have to read "2" "3" "." "5" and now have to make it or treat it as word and then using atoi(). I have to convert it into double. but i dont know how to do this....
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Nov 10, 2013
I have to optimize a code for below scenario. I am reading stdin (a file redirected to stdin) character by character. How many chars are going to come is not known. After every few chars there is a seaparator. e.g $ as below
rhhrkkj$hghjhdf$ddfkrjt
While reading, if the separator arrives I'm processing the string stored before that separator and then continue reading stdin in same fashion, till EOF. I am using getc(stdin) to read chars.
Using gprof I can see most of the program time is spent inside main() , for this reading logic. Rest of the program is just some insert and search operations. I am getting time of 0.01 secs at the moment, want to reduce further.
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Aug 10, 2012
How do I write an a program that will read an input file character by character?
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Mar 29, 2013
I'm writing some functions pertaining to binary trees. I've used recursion once before while learning quicksort but am still quite new and unfamiliar with it. And this is my first time touching a binary tree. So my question: In my addnode function, will the return root statement at the end ever return a value other than the value passed to the function?
Code:
#include <stdlib.h>
struct tnode
{
int data;
struct tnode * left;
struct tnode * right;
}
[code]....
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Oct 6, 2013
In my program, I'm supposed to read a text file (the name of which is given to me as a command line paramater, as long with an integer), and display the text in a specific format (each line can only be as long as the integer). However, I'm having trouble even reading the text file. I don't know the syntax. I'm only allowed to edit the function that does the formatting, and the code in that is
void typeset (int maxWidth, istream& documentIn)
I don't know how to 'read' the file, as most examples online are ifstream, or openFile or something like that. What I want to do is just read the first character of the file, and continuously keep reading characters until the end of the file.
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Sep 13, 2014
So I'm trying to create a function that replaces any instance of a character in a string with another. So first I tried the replace() string member function:
In my implementation file
void NewString::ReplaceChar(const char& target,const char& entry)
{
this->replace(this->begin(),this->end(), target, entry);
};
Main program
#include "NewString.h"
using namespace ...;
int main()
[Code].....
Instead of replacing the the l's with y's it outputted a long string of y's. Also, NewString is derived from the string class (it's for the assignment). the header and whole implementation file, already tested.
I've also tried, instead, to use a for loop in ReplaceChar() but I need to overload the == operator and I don't know how I should exactly:
bool NewString::operator ==(const char& target)const {
if(*this == target)
return true;
[Code]....
I want the == operator to test if the value in the char array is equal to target but I'm not sure how to pass in the position. I'm guessing the this pointer in ReplaceChar() is not the same as the one dereferenced in ==() because target is never replaced by entry in the string.
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Jan 11, 2015
From the page: [URL] ....
#include <iostream>
using namespace std;
int n;
int& test();
[Code] ....
Explanation
In program above, the return type of function test() is int&. Hence this function returns by reference. The return statement is return n; but unlike return by value. This statement doesn't return value of n, instead it returns variable n itself.
Then the variable n is assigned to the left side of code test() = 5; and value of n is displayed.
I don't quite understand the bold sentence. Shouldn't value of n and variable n be the same?
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Feb 12, 2014
I am having a problem assigning bits a value of 0. The data is a 16 bit integer the bits greater than the 12th bit have garbage either a 0 or a 1. I would like to assign all bits greater than 12th bit the value 0 no matter what their values are. Whats the best approach.
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Aug 13, 2013
Using the old fashioned (unsigned) multiplication instruction in x64 assembly multiplies RAX (64 bit register) by a 64 bit register. The answer is stored in RDX:RAX (i.e. the answer is 128 bits). Is there any way, using native c++ to get the value in RDX (higher 64 bits)? One I can think of is: right/(limit/left) e.g. if we are limited to a byte then 97*123 would overflow:
97/(255/123) = 46 times, which is RDX's (if it was one byte) value. But this is too inefficient. Is there a fast way?
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Mar 25, 2014
Value x is a 32-bit unsigned integer 3:
00000000000000000000000000000011
If we use bitwise-shift to shift all bits to the right by 2, x is 0:
00000000000000000000000000000000
If we then do a bitwise leftshift on x by 30, do we end up with:
11000000000000000000000000000000
or
00000000000000000000000000000000
In other words, when we perform right shift which clips away the least most significant bits, and then do a left shift, is it possible for those bits to reappear?
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Apr 25, 2013
I am trying to retrieve the first three bits of a number. The code that I am using should work but it isn't giving me the correct result when trying certain numbers. Below is the code I am using:
unsigned short num1, num2 = 0;
unsigned short num = 65535// binary 111111111111111
num1 = num && 0x07;// gives me 1 but should give 7(111)
num2 = num >>3;//gives me 8191, which is correct
Why I am not getting the first three correct bits(111)?
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Sep 3, 2013
I am working on a project where I need to reverse bits for a number.
For example, if I have 110111100000000 I need to reverse it to 0000000001111011.
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Aug 8, 2013
I have a double variable and depending on certain conditions I need to set certain bits of an unsigned short Variable. For example, if double var is odd I need to set the 15th bit of the unsigned short variable.
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Mar 30, 2014
I'm trying to write a program that writes data to a disk in C++ without caring about it's file system. Here is what I can do so far:
#include <iostream>
#include <unistd.h>
#include <fcntl.h>
using namespace std;
char buffer[] = "Wow! I'm writing this data to a disk without puttting it into a file!";
int main(){
int Disk=open("/dev/sdb",O_RDWR);
write(Disk,buffer,sizeof(buffer));
close(Disk);
return 0;}
But this program can only write ASCII characters to the disk. But what if I want to mainipulate bits on the disk, how would I do that?
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Jul 15, 2014
I am trying to encrypt a plaintext using DES in C. I read about the algorithm and how it works, but when i came to write the code i struggled. :
How to locate the lowest 8-bits in a 64-bit key ?
How to shuffle the plaintext according to the algorithm description ? (I read about bitwise operations, but i still cannot understand how i can use them to transfer for example the 5th bit to the location of the 30th bit)
Left shifting the key would not wrap the bits, so i just bitwise or with a mask that will add the bits that did not wrap around?
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Jan 15, 2014
I just have a short question! I have an sbyte and I want to convert it to an int, but I do not want a value conversion, just to copy the bits, such that the negative numbers in the sbyte will be their complement in the int (-12 in sbyte -> 244 in int)... How can I do that?las
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Jun 24, 2013
I have a 64-bit uint64_t number:
Code:
Primitive<uint64_t> b = 0xCCCCCCCC00000000; I need to save the first 31 (most important) bits - 7FFFFFFE.
I found this solution in the Internet:
Code:
start = (((b)>>(first)) & ((1<<(((last+1)-(first))))-1)); but in my case for this code:
Code: Primitive<uint64_t> start = (((b)>>(32)) & ((1<<(((63+1)-(32))))-1));
I get an error: left shift count >= width of type
And even if I change 63 to 62:
Code:
Primitive<uint64_t> start = (((b)>>(32)) & ((1<<(((62+1)-(32))))-1));
I get: error: integer overflow in expression
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Sep 9, 2014
I was trying to program an decimal to binary converter (8-bits) in C. I am a complete beginner so I tried to put the 1's and 0's of the binary number as they come without reversing the order for beginning. I have seen example on the internet but didn't understand them so I decided to write it as I understood it. So, I typed the code as shown below:
Code:
#include <stdio.h>
#include <stdlib.h>
int main() {
int number;
int BitNum[8], x;
[Code] ....
The problem with the code is that if binary form has 0s in it then program displays a random number instead of a 0. For example if decimal is 7, it should print out 11100000 but it displays only 111(and some stupid numbers instead of 0). I have tried to solve it but failed.
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Oct 3, 2013
So I'm supposed to write a code that asks a user for a string and then displays the hex, decimal, and binary code for each individual letter and then tells the user how many bits in binary were 1. For example: Enter a line of text: Hello
The ASCII code for 'H' is 0x48 in hex, 72 in decimal, or 01001000 in binary, 2 bits were set.
The ASCII code for 'e' is 0x65 in hex, 101 in decimal, or 01100101 in binary, 4 bits were set.
The ASCII code for 'l' is 0x6c in hex, 108 in decimal, or 01101100 in binary, 4 bits were set.
The ASCII code for 'l' is 0x6c in hex, 108 in decimal, or 01101100 in binary, 4 bits were set.
The ASCII code for 'o' is 0x6f in hex, 111 in decimal, or 01101111 in binary, 6 bits were set.
So far I've got a code that will display the binary bit pattern by shifting a mask and testing for a 1 or 0. The problem is I can't figure out how to make it so the 1's and 0's get put into a single integer rather than just printing out. I hope that makes sense. Here's my whole code.
Code:
#include<stdio.h>
main ()
{
int i;
char input;
printf ("Enter ........: ");
scanf ("%c", &input);
for (i = 1; i <= 8; i++)
[Code]...
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May 13, 2013
I made this program to convert bits to bytes, because I'm so sick of seeing ISP's advertise speeds in megabits, which I consider an intentional attempt to decieve :P And I think I've finally understood how the return value of scanf works since the last time I posted here, so my program can check to see if an integer was entered before processing the input, but I'm stuck on how to make the whole program start over if an integer is not entered. I have a hunch it would involve a loop, but I can't figure out how to make the program start over at "How many mb do you need converted?" if an integer is not entered into scanf..Here is the code I have so far:
Code:
#include <stdio.h>
int main () {
int b, mb, kb, Byte, kB, mB, gB;
char term;
}
[code]....
and my program makes the assumption for now at least, that mb will be inputted because that's the unit of measurement that i usually see advertised, and i didn't bother making an if statement to print a conversion in terms of gigabytes because i've never heard of a connection that fast :P
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Aug 10, 2013
I need a translate (in both directions) all primitive types, into char[] (will be stored in string)
I understand how to manipulate integral types with bits and I cant just cut them down and shift them, but float and double don't work with this manipulation. So, how I can create a perfect bit copy of float and double?
int i = 0xFCED03A4; //Random number
char c[4];
c[0] = ((i >> 3) & 0xFF);
c[1] = ((i >> 2) & 0xFF);
c[2] = ((i >> 1) & 0xFF);
c[1] = (i & 0xFF);
[Code]...
This is basic stuff but I need an equivalent for float and double types, and it needs to be a perfect BIT copy, not value copy.
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