C :: Fastest Way To Check If Bytes Contained In Array Are All X00
Nov 30, 2014
I'll process the raw content of a stream which obviously will be loaded one chunk at a time into an buffer.I need to check if every chunk content is x00 filled. If it is, I'll increase the blank chunks counter of 1.On your personal opinion, which is the fastest an less cycles consuming manner to achieve such result?
I was wondering this: is it possible to make an instant XOR of all the buffer content to check if it does return 0 ?the only way is it to cycle through all the bytes and compare each one of them with 0?
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Feb 22, 2013
and see if the first three match a list then read in three more behind those that were left and perform a similar test on them and keep going?
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Feb 15, 2014
I am wonder what is the fastest way of changing elements in array of characters for encode purpose, here is simple example presenting an idea:
Code:
char *a = "123456789":
char b[] = "ABCDEFGHI";
int 1;
for (i=0;i<strlen(a);i++) {
b[i] = a[i];
}
Is this approach better or worse than bit manipulation ?
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Mar 15, 2015
how to accommodate double-size:8 bytes in 4 bytes pointer in 32bit system.
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Mar 24, 2013
Code:
int i12 = 1001;
cout << i12 << " " << &i12 << endl;
gives the result: 0x7fff0d065098
It's 6 bytes, but I'd expect the address to be 8 bytes on my 64 bit machine. I am using Ubuntu 12.04, GNU compiler.
So, why the address is 6 bytes and not 8 bytes?
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May 8, 2012
i'm iterating through the system processes an when i find a process that belongs to a text oriented application, i want to read that text inside the external app. For example, when i get the process to an instance of notepad, i want to get the text contained inside notepad. i've tried to do it using Process.MainWindowHandle pointer, but with no success. How to do it? (This is for an "nanny" app i'm writing, which need access to text in external applications so that i can detect any unappropriated words)
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Mar 2, 2015
pThread turns out to be NULL here. Wondering what the correct way is...
Code:
class CPF_Thread {
public:
unsigned int threadID;
Coordinater coordinater;
virtual UINT proc() {
[Code] .....
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Sep 23, 2014
m_sName-- character array shall be 128 bytes
How do i create a character array that has 128 bytes?
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Feb 22, 2013
Using a table with the 256 bytes as strings, said table is used as a reference in the 2 functions of this code. Functions who make the conversion such as the title establishes, and in the inverse way too.
The main advantage is that you don't need any knowledge about managing bytes with c++..
Code:
#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
char* hextabla[] = { //256 BYTES
"00","01","02","03","04","05","06","07","08","09",
"0A","0B","0C","0D","0E","0F","10","11","12","13",
[Code] ....
I leave the project in MSVCPP 6, see attachment...
It's ready to compile in 'Release' mode.
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Mar 1, 2013
I do not understand how I can implement this.If fread != to at least 8 bytes then do THIS: printf (" your file is near the end of file", fread result);
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Dec 1, 2014
I need fastest method to reverse order of bytes in my char array.
For example i have:
unsigned char buf[8];
// consider data stored in buf is 88 77 66 55 44 33 22 11
// how to reverse it to: 11 22 33 44 55 66 77 88
// currently i can do it by equal assignment , i make another buf like:
unsigned char buf_ok[8];
[Code] ....
// This does reverse the bytes as i want but its very slow , i am looking for fast method ..
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Jun 2, 2013
I followed a tutorial to load a bitmap from file and convert it to a array of bytes to access it directly. Now to display the bitmap on screen do I have to convert it to a HBITMAP or can I display it from the array of bytes?
Also the program I am building is a calendar program and I need to know if I can manipulate the bitmaps pixels in the byte array (e.g change color and resize image)
here is the code to load the bitmap
HTML Code:
BYTE* Sprite2::LoadBMP(int* width, int* height, long* size, LPCTSTR bmpfile ) {
BITMAPFILEHEADER bmpheader;
BITMAPINFOHEADER bmpinfo;
DWORD bytesread;
HANDLE file = CreateFile(bmpfile,GENERIC_READ, FILE_SHARE_READ,
0, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, 0);
[code]....
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Apr 1, 2013
What is the most efficient way to calculate Fibonacci. Is it recursion with memorization, is it iteration or is there another approach?
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Jul 12, 2012
I have to write a function
struct rNumber add(rNumber a ,rNumber b);
which adds two rational numbers in following representation :
rNumber := s*(n/d)* 2^e
struct rNumber{
_byte_t s; // sign (do not consider for this question)
uint n; //numerator
uint d;// denominator
short e;//exponent
}
If the exponents of both numbers are not equal, then they have to be made equal in order to add them. This can be made in 4 ways : increase or decrease the n or d of both numbers.
But if we decrease the denominator of a number (a.d =1) by shifting it for example 1 bit to the right, we get 0 which leads to INFINITY for the fraction. In another case decreasing the numerator would lead the n to be 0 which meanse the whole fraction is then 0.
According to this, in worst case, all 4 cases has to be checked for the right result.
So far the UNDERFLOW of n or d is considered. If we try to increase the value of n or d, then OVERFLOW may also occur.
The very first, intuitive solution would be iteratively increase/decrease one of the terms and to check if the change leads to ZERO or INFINITY.
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Apr 25, 2013
I'm currently building a new data structures that will be used in monte carlo generators (and so will be constructed several million times) and I'm wondering what's the best way (computer-speed-wise) to pass the data to the constructor. I am currently doing it using references and passing arrays as pointers like this:
Code:
class particle{
public:
particle(double *ar,int &id):IDup(id){
for (int i=0;i<5;++i)
Pup[i]=ar[i];
}
int IDup;
double Pup[5];
};
I'm assuming that since using references has no need to create a temporary memory slot it's more efficient .....
As for the arrays: is there a way for me to pass them as reference as well? (not using c++11), I'm using arrays instead of vectors as much as I can because I assume that vectors, being more advanced data structures, would take more time to create.
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Jan 9, 2013
Names are std::string no more than 3 characters in length. What built in container or boost container is fastest at finding a name (Key) in it's container.
Finding a name.
At the name will be a value double.
I need the most efficient at finding and finding/updating the value. Forget out inserts and deletes.
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Sep 3, 2014
Suppose you have defined a container of elements and you want do define a comparison function between elements based on the ordering of the elements in that container. What algorithm for the comparison would be the most efficient?
Example:
master = {tom, sam, mary, sally, bert, frank}
subset = {bert, sam, mary, tom}
goal: change subset to {tom, sam, mary, bert}
My current idea is to simply iterate from the beginning of the container, and whichever of the two elements is found first is the lesser (assuming the second is not the same as the first). It seems kind of naïve though. Any better performing algorithm? This is what I have so far:
#include <iostream>
#include <iterator>
#include <list>
#include <vector>
#include <stdexcept>
#include <algorithm>
[code]....
Would perhaps forcing the container to have a random access iterator, like vector, and then writing a specialized comparison function based on that perform even faster? Or perhaps force the container to be a map to integers, and compare the elements by comparing the integer mapped values?
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Sep 24, 2013
1. Input an dimension and elements of an array from the keyboard. Count the odd elements of an array and that number join to variable K, then sort the last K elements in decreasing order.
Code:
#include <stdio.h>
main ()
{
int A[100], i, n, j, K = 0;
printf ("Type in the dimension of an array:
");
scanf ("%d", &n);
[Code]....
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Apr 7, 2014
I can have at most 3 structs in array, but it could be 0,1,2 or 3 structs in array. I am trying to avoid dynamic memory allocation. I initialize sensors to 3 to reserve space for them in memory, since there may be at most 3 elements in the array. But I am testing a condition where there will only be 2 elements:
Code:
#include <stdio.h>#include <stdlib.h>
#include <string.h>
typedef struct {
unsigned long long int address;
float current;
unsigned char pressure_units;
} sensor;
[Code]...
The problem is even though there are only 2 sensors out of 3 in the array, sizeof(sensors)/sizeof(sensors[0]) returns 3. I assume because when it allocates memory for 3, it includes that allocated memory even though it really doesn't contain the struct. How can I figure out how many elements were really inserted into array, not just allocated to array?
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Nov 8, 2013
This program works but i need to build an additional loop that will re-prompt a user if his initial entry (int y_n) is other than 'Y', 'y', 'N', 'n'. For instance if a user tries to enter 'Yup', he will be prompted "That isn't a valid entry" and then re-asked to enter int y_n.
Note: If user answers Y he is asked to enter a value that is entered into an array. If the user at any point answers N, the program ends and final stats are cout.
#include <iostream>
using namespace std;
int main(){
char y_n;
int i = 0;
float input_value;
float myarray[100];
[Code] .....
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Oct 16, 2013
If I have a char array that that looks like
char array[] = {'a', 'b', 'c'};
How can I check user input against all of these values at once?
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Dec 24, 2013
How can I check how many times the numbers in the array are listed?
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Jun 9, 2013
This is an assignment question In C++, there is no check to determine whether the array
index is out of bounds.Design a class myArray that solves the out-of-bound array index problem and allows the user to begin the array index starting at any integer, positive or negative. Every object of type myArray should be an array of type int.
Part 1 processes only int arrays. Redesign the class myArray using class templates so that the class can be used in any application that requires arrays to process data.
I don't understand the second part. should i just change the array from int to char or something?
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Oct 3, 2013
How i could go about extracting and checking if the very first character in my string array is an alphabet
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Jan 27, 2015
finishing my program which needs to do the following:
(i) Write code to read in the dictionary into an array of words
(ii) Write code to check the spelling of a word entered by the use
(iii) Like Scrabble / Countdown the user enters the letters they have and my code must find the word using the highest number of those letters
I have completed a good bit so far but I'm stuck on my checkSpelling() and findWord() functions as well as part (iii)
#include "stdafx.h"
#include <stdio.h>
#include "string.h"
int countCharOccurence(char *string, char c);
int getOption();
int checkSpelling();
[Code]....
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Nov 20, 2012
I am unable to check if the character in the 2D array is alpha
here is my code
#include<iostream>
#include<cctype>
#include<cassert>
#include<cstring>
const int maxChar = 20 ;
using namespace std ;
int main() {
int count = 0 ;
char d[2][20] = { "hi" , "di" } ;
[code]....
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