I have a program that writes out the frame number and current system time whenever a picture is taken on a camera:
SYSTEMTIME st;
GetSystemTime(&st);
lStr.Format( _T("%d %d.%d.%d.%d\r\n"),GetFrames() ,st.wHour, st.wMinute, st.wSecond, st.wMilliseconds);
std::wfstream myfile;
myfile.open("test.txt", std::ios::out | std::ios::in | std::ios::app );
if (myfile.is_open())
{
myfile.write((LPCTSTR)lStr, lStr.GetLength()*sizeof(TCHAR));
myfile.close();
}
else {lStr.Format( _T("open file failed: %d"), WSAGetLastError());
}
The text file that the program outputs seems to write the data correctly, but I get spaces and characters that shouldn't be there at the start of each line. The website doesn't seem to format the spaces correctly so i'll post a picture, this is what the text file looks like. The file also shows bullet points sometimes in addition to the zero's.
As you can see the first line is fine but it seems to get worse the longer I write to the text file. The program is writing to the file about 10 times every second. I am new to C++ and I am not sure what could be causing this. I tried to look for other questions similar to this but they didn't seem to have a solution I was looking for. Any help would be appreciated.
The solution has 2 parts:
lStr.Format( _T("%d %d.%d.%d.%d\r\n"),GetFrames() ,st.wHour, st.wMinute, st.wSecond, st.wMilliseconds);
should be
lStr.Format( _T("%lu %d.%d.%d.%d\n"),GetFrames() ,st.wHour, st.wMinute, st.wSecond, st.wMilliseconds);
As GetFrames() returns DWORD which is unsigned long and you are writing the file as text so \n is converted to \r\n if needed, depending on the operating system.
The other part is that the second parameter of wfstream::write is number of characters not number of bytes so
myfile.write((LPCTSTR)lStr, lStr.GetLength()*sizeof(TCHAR));
should be
myfile.write((LPCTSTR)lStr, lStr.GetLength());
When you use std::wfstream::write (basic_ostream), it takes the size of your string. You multiply that size again with * sizeof(TCHAR). Removing this additional multiply should simply fix your problem.
Though if you have anywhere else issues (e.g. a third-party library returns with too many spaces), you could always trim the string.
A basic example for this:
template<class TString>
static inline TString &trim_left(TString &s)
{
s.erase(std::begin(s), std::find_if(std::begin(s), std::end(s), std::not1(std::ptr_fun<int, int>(std::isspace))));
return s;
}
template<class TString>
static inline TString &trim_right(TString &s)
{
s.erase(std::find_if(s.rbegin(), s.rend(), std::not1(std::ptr_fun<int, int>(std::isspace))).base(), std::end(s));
return s;
}
template<class TString>
static inline TString &trim(TString &s)
{
return trim_left(trim_right(s));
}
Related
I actually need my driver to read (line by line) some programs that are going to be blacklisted.
_T("bannedfile.exe") is where I actually need to put the blacklisted program.
How can I make _tcscmp read a text file, line by line?
(It makes a comparison between the host program that loads the driver, and the blacklisted one)
BOOL ProcessBlackList() {
TCHAR modulename[MAX_PATH];
GetModuleFileName(NULL, modulename, MAX_PATH);
PathStripPath(modulename);
if (_tcscmp(modulename, _T("bannedfile.exe")) != 1) {
return 0;
}
else {
return 0x2;
}
}
Can't be done that way.
You should be able to use use getline to read the file line by line and then pass the lines to _tcscmp. Should work something like this:
wchar_t const name[] = L"bannedfile.exe";
std::wifstream file(name);
std::wstring line;
while (std::getline(file, line)
{
if (_tcscmp(modulename, line.c_str()) == 0) {
return TRUE; //module is in list
}
}
return FALSE; // module is not in list
Lacking a copy of VS to test it at the moment.
If you run into unicode parsing problems because the file's encoding isn't quite what the defaults expect, give this a read: What is std::wifstream::getline doing to my wchar_t array? It's treated like a byte array after getline returns
I am working on a program that can encode and then decode text in C++. I am using the stack library. The way the program works is that it first asks you for a cypher key, which you put in manually. It then asks for the file name, which is a text file. If it is a normal txt file, it encodes the message to a new file and adds a .iia files extension. If the text file already has a .iia file extension, then it decodes the message, as long as the cypher key is the same as the one used to encode it.
My program does encode and decode, but how many characters it decodes is determined by temp.size() % cypher.length() that is in the while loop in the readFileEncode() function. I think this is what is keeping the entire file from being encoded and then decoded correctly. Another words, the ending file after it has been decoded from say "example.txt.iia" back to "example.txt" is missing a large portion of the text from the original "example.txt" file. I tried just cypher.length() but of course that does not encode or decode anything then. The entire process is determined by that argument for the decoding and encoding.
I cannot seem to find out the exact logic for this to encode and decode all the characters in any size file. Here is the following code for the function that does the decoding and encoding:
EDIT: Using WhozCraig's code that he edited for me:
void readFileEncode(string fileName, stack<char> &text, string cypher)
{
std::ifstream file(fileName, std::ios::in|std::ios::binary);
stack<char> temp;
char ch;
while (file.get(ch))
temp.push(ch ^ cypher[temp.size() % cypher.length()]);
while (!temp.empty())
{
text.push(temp.top());
temp.pop();
}
}
EDIT: A stack is required. I am going to implement my own stack class, but I am trying to get this to work first with the stack library. Also, if there is a better way of implementing this, please let me know. Otherwise, I believe that there is not much wrong with this except to get it to go through the loop to encode and decode the entire file. I am just unsure as to why it stops at, say 20 characters sometimes, or ten characters. I know it has to do with how long the cypher is too, so I believe it is in the % (mod). Just not sure how to rewrite.
EDIT: Ok, tried WhozCraig's solution and I don't get the desired output, so the error now must be in my main. Here is my code for the main:
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <cstdlib>
#include <cctype>
#include <stack>
using namespace std;
void readFileEncode(string fileName, stack<char> &text, string cypher);
int main()
{
stack<char> text; // allows me to use stack from standard library
string cypher;
string inputFileName;
string outputFileName;
int position;
cout << "Enter a cypher code" << endl;
cin >> cypher;
cout << "Enter the name of the input file" << endl;
cin >> inputFileName;
position = inputFileName.find(".iia");//checks to see if the input file has the iia extension
if (position > 1){
outputFileName = inputFileName;
outputFileName.erase(position, position + 3);// if input file has the .iia extension it is erased
}
else
//outputFileName.erase(position, position + 3);// remove the .txt extension and
outputFileName = inputFileName + ".iia";// add the .iia extension to file if it does not have it
cout << "Here is the new name of the inputfile " << outputFileName << endl; // shows you that it did actually put the .iia on or erase it depending on the situation
system("pause");
readFileEncode(inputFileName, text, cypher); //calls function
std::ofstream file(outputFileName); // calling function
while (text.size()){// goes through text file
file << text.top();
text.pop(); //clears pop
}
system("pause");
}
Basically, I am reading .txt file to encrypt and then put a .iia file extension on the filename. Then I go back through, enter the file back with the .iia extension to decode it back. When I decode it back it is gibberish after about the first ten words.
#WhozCraig Does it matter what white space, newlines, or punctuation is in the file? Maybe with the full solution here you can direct me at what is wrong.
just for information: never read file char by char it will take you hours to finish 100Mb.
read at least 512 byte(in my case i read directly 1 or 2Mb ==> store in char * and then process).
If I understand what you're trying to do correctly, you want the entire file rotationally XOR'd with the chars in the cipher key. If that is the case, you can probably address your immediate error by simply doing this:
void readFileEncode(string fileName, stack<char> &text, string cypher)
{
std::ifstream file(fileName, std::ios::in|std::ios::binary);
stack<char> temp;
char ch;
while (file.get(ch))
temp.push(ch ^ cypher[temp.size() % cypher.length()]);
while (!temp.empty())
{
text.push(temp.top());
temp.pop();
}
}
The most notable changes are
Opening the file in binary-mode using std::ios::in|std::ios::binary for the open-mode. this will eliminate the need to invoke the noskipws manipulator (which is usually a function call) for every character extracted.
Using file.get(ch) to extract the next character. The member will pull the next char form the file buffer directly if one is available, otherwise load the next buffer and try again.
Alternative
A character by character approach is going to be expensive any way you slice it. That this is going through a stack<>, which will be backed by a vector or deque isn't going to do you any favors. That it is going through two of them just compounds the agony. You may as well load the whole file in one shot, compute all the XOR's directly, then push them on to you stack via a reverse iterator:
void readFileEncode
(
const std::string& fileName,
std::stack<char> &text,
const std::string& cypher
)
{
std::ifstream file(fileName, std::ios::in|std::ios::binary);
// retrieve file size
file.seekg(0, std::ios::end);
std::istream::pos_type pos = file.tellg();
file.seekg(0, std::ios::beg);
// early exit on zero-length file.
if (pos == 0)
return;
// make space for a full read
std::vector<char> temp;
temp.resize(static_cast<size_t>(pos));
file.read(temp.data(), pos);
size_t c_len = cypher.length();
for (size_t i=0; i<pos; ++i)
temp[i] ^= cypher[i % c_len];
for (auto it=temp.rbegin(); it!=temp.rend(); ++it)
text.push(*it);
}
You still get your stack on the caller-side, but I think you'll be considerably happier with the performance.
I am maintaining a C++ method which one of my clients is hitting an issue with. The method is supposed to write out a series of identifiers to a file delimited by a new line. However on their machine somehow the method is writing a series of NULL's out to the file. Opening the file in a binary editor shows that it contains all zeros.
I can't understand why this is happening. I've tried assigning empty strings and strings with the first character set to 0. There is no problem creating the file, just writing the identifiers to it.
Here is the method:
void writeIdentifiers(std::vector<std::string> IDs, std::string filename)
{
std::ofstream out (filename.c_str(), std::ofstream::binary);
if (out.is_open())
{
for (std::vector<std::string>::iterator it = IDs.begin();
it != IDs.end();
it++)
{
out << *it << "\n";
}
}
out.close();
}
My questions: is there any possible input you can provide that method which will create a file which has NULL values in it?
Yeah, the following code quite clearly writes a series of NULL bytes:
std::vector<std::string> ids;
std::string nullstring;
nullstring.assign("\0\0\0\0\0\0\0\0\0\0", 10);
ids.push_back(nullstring);
writeIdentifiers(ids, "test.dat");
Because the std::string container stores the string length, it can't necessarily be used in the same way as an ordinary C (null-terminated) string. Here, I assign a string containing 10 NULL bytes. Those are then output because the string length is 10.
So I have a .cpp file with a Function which recieves a filename, and should return a String with the contents of the file (actualy modified contents, I modified the code to make it more understandable, but that doesn't have any effect on my problem). The problem is that f.good() is returning false and the loop, which reads the file is not working.
CODE :
#include "StdAfx.h"
#include "Form21.h"
#include <string>
#include <fstream>
#include <iostream>
string ReadAndWrite(char* a){
char filename[8];
strcpy_s(filename,a);
string output;
char c;
ifstream f(filename,ios::in);
output+= "Example text"; // <-- this writes and returns just fine!
c = f.get();
while (f.good())
{
output+= c;
c= f.get();
}
return output;
}
Does anyone have an idea on why this is happening?
Does it have something to do with, that this is a seperate .cpp file( it doesnt even throw out an error when I remove #include <fstream>).
Maybe there is a different kind of method to make the loop?
I'll be very happy to hear any suggestions on how to fix this or maybe a different method on how to achieve my goal.
First, there's really no reason to copy the file name you receive -- you can just use it as-is. Second, almost any loop of the form while (stream.good()), while (!stream.bad()), while (stream), etc., is nearly certain to be buggy. What you normally want to do is check whether reading some data worked.
Alternatively, you can skip using a loop at all. There are a couple of ways to do this. One that works nicely for shorter files looks like this:
string readfile(std::string const &filename) {
std::ifstream f(filename.c_str());
std::string retval;
retval << f.rdbuf();
return retval;
}
That works nicely up to a few tens of kilobytes (or so) of data, but starts to slow down on larger files. In such a case, you usually want to use ifstream::read to get the data, something along this general line:
std::string readfile(std::string const &filename) {
std::ifstream f(filename.c_str());
f.seekg(0, std::ios_base::end);
size_t size = f.tellg();
std::string retval(size, ' ');
f.seekg(0);
f.read(&retval[0], size);
return retval;
}
Edit: If you need to process the individual characters (not just read them) you have a couple of choices. One is to separate it into phases, where you read all the data in one phase, and do the processing in a separate phase. Another possibility (if you just need to look at individual characters during processing) is to use something like std::transform to read data, do the processing, and put the output into a string:
struct character_processor {
char operator()(char input) {
// do some sort of processing on each character:
return ~input;
}
};
std::transform(std::istream_iterator<char>(f),
std::istream_iterator<char>(),
std::back_inserter(result),
character_processor());
I would check that strlen(a) is not greater than 7...
You might overrun filename and get a file name that doesn't exist.
Not relating the problem, I would re-write the function:
string ReadAndWrite(string a) { // string here, if you are into C++ already
string filename; // also here
filename = a; // simpler
string output;
char c;
ifstream f(filename.c_str()); // no need for ios::in (but needs a char *, not a string
output+= "Example text"; // <-- this writes and returns just fine!
f >> c; // instead c = f.get();
while (f) // no need for f.good())
{
output+= c;
f >> c; // again, instead c= f.get();
}
return output;
}
Might I suggest using fopen? http://www.cplusplus.com/reference/clibrary/cstdio/fopen/ It takes in a filename and returns a file pointer. With that you can use fgets to read the file line by line http://www.cplusplus.com/reference/clibrary/cstdio/fgets/
I am currently developing an application, which gets the input from a text file and proceeds accordingly. The concept is the input file will have details in this fomat
A AND B
B OR C
Each and every line will be seperated by a blank space and the input must be taken from the text file and processed by logic. I use a TCPP compiler and i am facing problems reading the input. Please help me with the issue...
Reading input a line at a time is normally done with std::getline, something like this:
std::string line;
std::ifstream infile("filename");
while (std::getline(line, infile))
// show what we read
std::cout << line << "\n";
If you're having trouble with things like this, you might consider looking for a (better) book on C++ than whatever you're now (hopefully) using.
Following can be used straightaway:
BOOL ReadFile(CString filename)
{
BOOL bRead = TRUE;
std::ifstream m_strmFile;
m_strmFile.open(filename, std::ios::in);
char pszLine[256];
memset(pszLine, 256, 0);
if (m_strmFile)
{
// Read whatever number of lines in your file
for (unsigned int i = 0; i < 5/*number of lines*/; i++)
m_strmFile.getline(pszLine, 256);
// Do whatever you want to do with your read lines here...
}
else bRead = FALSE;
return bRead;
}
are you using headr files like:
include
or #include and you can make use of the fileobject.getline(), (do check its proper syntax.) function in C++ or for char by char use fileobject.get(ch) kind of function