C++ :: Pushing Characters Back Into The Input Buffer?
Mar 29, 2013
I plan to read one character at a time from a very large text file.
The tokens that I would like to extract are basically words and they are delimited by varying numbers of spaces or tabs.
For example, the first line has two words separated by five spaces:
Joe Mark
Problem:I apply get() each time advancing towards Mark. For me to know ive reached the next token, Mark, I merely have to get() until it equals 'M'. The problem by then its too late as Ive already captured 'M'. I somehow need to capture the fifth space and the code must "know" the next character is 'M' without getting() it.
Kernighan and Richie offer us a function getch() and ungetch() whereby the ungetch pushes back the last character into the input . The problem with this is that I believe is that the buffer is not the actual input buffer stream but rather a simulated character array which contains the input. I dont think itll be as efficient on a text file so large.
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Jun 20, 2013
I'm challenged to write a code for the following:
write a text up to 1000 characters, and get it back. the end of the text is detected though EOF on a new line or reaching 1000 characters.(EOF=ctr-Z on a new line)
I mainly have problem how to bring the EOF work probably. it doesn't react when I press ctrl-z directly?
Code:
int i;
char Text[1000];
printf("write the text:
");
gets(Text);
for(i=0;i<=1000;i++){
[Code] .....
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Feb 9, 2015
I have to make a function that i'll later be able to use for a ceasar cypher. The letters should shift a user inputted number. This is what I have so far:
char shiftChar(char c, int s) {
char ch = c;
int shift = s;
int newC;
newC = int(ch) + shift;
return newC;
}
The problem with this, is that it doesn't loop back to the start of the alphabet once i get past z.
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Aug 13, 2014
I would just like to know what does
while( (c =getchar())!='
' && c !=EOF );
do ? and how it do it?
I have see it in a example to clear the input buffer for next input through scanf but does not know its working clearly.
it is used in this example :
Code:
#include<stdio.h>
struct linklist {
char value[20];
struct linklist *next;
};
struct linklist *head,*curr;
[Code] .....
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Aug 7, 2014
When the program is processing/sleeping, those char input at that time would not goes into the buffer until the next input request (such as calling istream::get). The program below shows this.
#include <iostream>
#include <streambuf>
#include <chrono>
#include <thread>
int main() {
std::cout << "Sleeping...
[Code] ....
I wonder if there is a way to distinguish between the input comes from the time that does not request it (i.e., during processing or sleeping) and those comes after the time does request it (in the example, after "Input something: ").
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May 6, 2014
The documentation of the class filebuf in the reference of cplusplus.com says:
Objects of this class may internally maintain an intermediate input buffer and/or an intermediate output buffer, where individual characters are read or written by i/o operations. These buffers are synchronized with the contents of the file once filled up, when explicitly requested to do so (sync), or when the object is closed.
Objects of this class may be explicitly made unbuffered by calling member pubsetbuf with both arguments set to zero (see member setbuf): Unbuffered file stream buffers perform the i/o operations directly on the file, without an intermediate buffer.
The C++ standard ensures that filebuf objects have an intermediate input/output buffer/s (i.e, the default constructor of the class filebuf creates the intermediate buffer/s)?
The standard C++ library only allows unbuffering filebuf objects (as the above quote says) but doesn't allow forcing filebuf objects to be buffered.
I have been seeying the concrete implementation code of the standard C++ library in my Windows Operating System (Windows 7 Ultimate 64 bits Service Pack 1) and it seems that fielbuf objects never uses intermediate input/output buffer/s, they use FILE streams of the standard C library instead to do the work. Are this FILE streams always buffered? If true, are they fully-buffered or line-buffered? what is the size of the buffers (perhaps macro BUFSIZ from <cstdio>)? and can I change this size?
I am worried about performance in reading and writing from/to files: if the default behaviour offers the best performance (perhaps if files are too large is better force buffering and choose a larger buffer size).
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Jul 17, 2014
I am receiving packets of data from an ethernet cable. This is the line of code that is streaming in data from the ethernet cable:
size_t num_rx_samps = rx_stream->recv(&buff.front(), buff.size(), md, 3.0, enable_size_map);
and here is my attempt to push it onto a vector:
std::vector<size_t> processing_queue; //HERE IS WHERE I'M TRYING TO PUSH THE PACKETS ONTO A VECTOR
processing_queue.push_back(num_rx_samps);
I previously had my program saving to a .dat file (the commented out lines), but I'm trying to change it to pushing values onto a vector so I can stream the data packets from the ethernet cable to be processed. However, I'm having issues with pushing the data packets onto the vector?
The following is the code:
#include <uhd/types/tune_request.hpp>
#include <uhd/utils/thread_priority.hpp>
#include <uhd/utils/safe_main.hpp>
[Code].....
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Apr 16, 2014
Using cin.sync() works great so far, but my program still breaks if you copy something with multiple lines into the console.
string test = "";
while(true) {
cin.sync();
getline(cin, test );
cout << endl << "test: " << test << endl;
}
However, if you were to copy this:
1
2
3
and paste it into the program, the output would be1
2
3
test: 1
test: 2
And if you press enter one more time:1
2
3
test: 1
test: 2
test: 3
The 3 finally pops out.
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Jul 6, 2012
I am busy with a project, it is going to consist out of 3 different windows which is logic enough for this whole code to be interactive.
It must be able to pull data into a windows form, displaying it into a textbox, and when you click on the textbox it needs to open up another window where you will have a windows form that will display data as the code loops through the questions in the database.
I am not sure how to push the data that has been selected on the database to the next window..
Here is my code for the first window:
;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form {
//SqlConnection myConnection = new SqlConnection("Data Source=(local);Initial Catalog=KnowledgeEssentials;Integrated Security=SSPI");
//int intType = 0;
public Form1()
[code].....
With the second window the data in the table needs to be displayed and each row from the table needs to have a checkbox next to them, so that if the check box is checked, the relevant information of the checked row will show up in the 3rd window... so MY question is, HOW do I pull that data from that specific database and let it show in the listcheckbox?
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Oct 23, 2013
I'm trying to get the user to input their 5 digit zip code but my problem is how can I stop the program after the five characters have been inputted. Also how can I only get numbers to be inputted cause so far letters can be inputted as well.
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Mar 17, 2015
I am trying to generate possible combinations of 4 lower case letters from aaaa - zzzz. The words will then be used against a file that contains encrypted passwords that each relate to a 4 lower case word. I have successfully generated the words. Now all i need to do is put the created words (aaaa, aaab, etc...) to an array so I can use crypt((array[i+1]), buff) and print the encrypted 4 letters that come from the file. I am having a lot of trouble complete this though.
New problems that are occurring
The main problem is in the all function and main. I'm not wanting to print the aaaa, aaab, aaac, etc to the screen but I want to put it in an char array so that i can compare each individually to each line from the file using crypt. How to put all 456976 combinations into an array, compare it to each line of code, and print the solutions to the screen.
File:
$1$6gMKIopE$I.zkP2EvrXHDmApzYoV.B.
$1$pkMKIcvE$WQfqzTNmcQr7fqsNq7K2p0
$1$0lMKIuvE$7mOnlu6RZ/cUFRBidK7PK.
Code:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
[Code]....
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Mar 13, 2013
how to read characters from user and construct a sting and then extract part of it using substring?
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Jan 5, 2015
I have got to create a program that will gather input from the user and then encrypt & decrypt those characters.
I'm not very confident at coding so I'm sure many parts of my code are written poorly and not following the best practice so I have written a simple version of an algorithm where the program simply adds/subtracts a value of 2 to/from the ASCII values but I have discovered the use of the rand() and srand functions but I'm unsure how to go about using them within both my encrypt and decrypt function as a single value (static variable?).
Here is my code in its entirety at the moment.
#include <iostream >
#include <iomanip>
#include <cstdlib>
#include <ctime>
#include <string>
#include <cstring>
#include <fstream>
using namespace std;
char getMenuSelection (char m);
void encrypt (char key[]);
void decrypt (char code[]);
[code]....
This code currently doesn't execute due to ' undefined reference to 'encrypt(char*) '
Question
I am asking how to generate the random number and incorporate this into my encrypt and decrypt functions.
1. Would the use of a static or global variable make this work as is?
2. Would I need to create separate class files for both functions?
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Jan 10, 2014
I'm doing an exercise that prints all input lines that are longer than 80 characters. I rather not use any libraries so I decided to write my own function that counts characters to use it in my main program. However when integrate things my function returns zero all the time.
Here is my full code:
/* Exercise 1-17 Write a program to print all input lines that are longer than 80 characters */
#include<stdio.h>
/* Declarations*/
#define MAX_STRING_LEN 1000
int count_characters(char S1[]);
int main() {
[Code] .....
So I was trying to debug my count_characters() function and this is the code if I was to run it seperately:
Code:
#include <stdio.h>
/* counts character of a string*/
main() {
int nc = 0;
int c;
for (nc = 0; (c = getchar()) != '
'; ++nc);
printf("Number of characters = %d
", nc);
}
which works...
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Nov 24, 2014
I have trouble printing out the movies starting with inputing only two letters.
#include <iostream> //cout, cin, endl,getline
#include <fstream> //ifstream
#include <cstdlib> // exit
using namespace std;
const int NUM_MOVIES = 116792;
struct Movie {
[Code] ....
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Jul 19, 2013
How do I prevent user from entering characters or symbols instead of numbers?
int num;
cout<<"Enter a number."<<endl;
cin>>num;
Also, how do I prevent user from entering a number instead of a character?
char c;
cout<<"Enter a character."<<endl;
cin>>c;
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Feb 7, 2013
I am stuck in this program, Be given a string of chars, where each single char belongs to the following alphabet: a..zA..Z0..9 (So, in the string there are only lowercases, uppercases and digits. No blank, no comma, ...). For every char of the given alphabet, count how many times in the string
1-- the char belong to a sequence of identical chars whose length is at least three (i.e.: in the string cc74uyrpfccc348fhsjcccc3848djccccc484jd for three times the character 'c' satisfies this condition)
Code:
#include<stdio.h>
#include<conio.h>
#include<string.h>
[Code]...
2-what is the longest substring of characters strictly rising interm of ASCII code(the following is greater (>) of the previous)
3- what is the longest substring of successive characters interm of given string rannge (i.e.: fhkjshdfruytyzABCDEfglsj => 7)
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Mar 20, 2014
so my question is i want to print characters,no string just an array of characters,i do this but it s not working,maybe i have to put the '' at the end?
Code:
int main() {
int i;
char ch[5];
for(i = 0; i < 5; i++) {
scanf("%c",&ch[i]);
[Code]...
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Jul 6, 2014
Im supposed to find the common characters between two string characters, assuming that the user wont input duplicate letters like ddog. When I run my code I get an output of a question mark upside down. Here is my code with comments on what each part is supposed to do
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(){
char str1[20], str2[20],remp = ' ';
int size1,i,j,temp;
printf ("Input the first string");
[Code]...
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Mar 26, 2014
I have an array of characters. I am trying to find "houston". The only way I can think of to do this is to use a for loop and check each individual character. Is there an easier way to do this?
char string[] = "Fishing tourism miami atlanta dallas houston";
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Oct 29, 2014
I have an int array of size 5 and I have my program to accept 5 integers between 10 and 100 inclusively. I should be able to type integers over and over again until I get 5 that are in the range, 10 <= x <= 100. Now when I get 5 that fall in that range the program should continue but instead it wants a 6th number before continuing. I'm suspecting the program is hanging on to a new line character. Anyway to ignore the new lines? Couldn't find anything for C# without clearing the screen.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace DupElim {
//dup elimination
[code]....
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Oct 17, 2014
Im creating a permissions profiler in c by using stat()I ran into a problem of getting a bad address as in my path. Ive tried multiple solutions with no dice, and now I have one more solution I want to try but I dont understand how.how do you use a snprintf and pass that into a buffer, and pass that into a path for stat()?
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Jan 12, 2015
I`ve wrote a function for my utility to XOR char* buffer by a key, then to reverse it with the same key. Here is the code, it`s simple enough:
Code:
static inline char* XOR_buffer(const char* d, const char* k ) {
char *newstr = (char*) malloc(sizeof(char)* strlen(d));
newstr[0]='';
printf("%d is size of string
", strlen(d));
char *begin = newstr;
char* ret = begin;
int len = strlen(k);
}
[code]....
The lengh of the string is reduced by the second XOR call. You can try it out, just define XORDBG to view the error message in the second pass to the buffer.
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Feb 5, 2014
I want to use a const char* as a buffer. I am reading values from a file and adding them to a buffer. How to extract the values is simple enough. I am reading through a filestream, reading each character into a char pointer and progressing that char pointer every time. I have another char pointer marking the start positon
eg.
char *mychar = new char;
char *char1 = new char;
char *char2 = new char;
const char *constchar ;
char2 = char1;
while(filestream.read(mychar,1) {
*char1 = *mychar;
++char1;
}
Then I get this problem: constchar = mychar; // const char* = char*.
Constchar does not catch all the data in other words. At some stage some data is lost due to zeros in the data.. How can I put values into a const char and get around this problem? The const char* will //only record everything up until the first zero.
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Aug 22, 2014
suddenly nothing is written to my file
void taglessLine(char line[],ofstream& buffer){
buffer.open("buffer.txt", ios::out);
int len=strlen(line);
[Code].....
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Dec 17, 2014
get some opinions on, or established methods on how your buffer size should be decided.
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