I am trying to read a las file larger then 2GBs (about 15GBs) but ios::fail() flag becomes true in 345th byte. Here is the code below.
void Foo()
{
char* filename = "../../../../../CAD/emi/LAS_Data/AOI.las";
ifstream m_file (filename);
char c;
int count = 0;
if (m_file.is_open())
{
while ( m_file.good() )
{
m_file.get(c);
cout << c << endl;
count++;
}
// Check State
if(m_file.fail())
cout << "File Error: logical error in i/o operation." << endl;
if(m_file.eof())
cout << "Total Bytes Read: " << count << endl;
m_file.close();
}
else
{
cout << "File Error: Couldn't open file: " << endl;
}
}
And the output is:
...
File Error: logical error in i/o operation.
Total Bytes Read: 345
What am I missing?
I'm going to guess that you're using Windows. Windows has a quirk that a Control-Z marks the end of a text file, no matter how large the file actually is. The solution is to open the file in Binary mode.
ifstream m_file (filename, std::ios::binary);
Related
Please look at this code first, then I will ask my question.
#include <bits/stdc++.h>
#include <fstream>
using std::cout;
using std::cin;
using std::endl;
int main() {
std::ofstream out_file ("outfile.txt"); /* creates a outfile.txt */
if (!out_file) { // checks files existence
std::cerr << "Error bruh!" << endl;
return (1);
}
int num = 100;
double total = 456.78;
std::string name = "atik";
out_file << num << "\n" // writing to the file
<< total << "\n"
<< name << endl;
/* Reading from file, because i want to! - */
std::ifstream in_file("outfile.txt"); // will open outfile for reading.
char c;
while (in_file.get(c)) {
cout << c;
}
/*
Output (as expected) -
100
456.78
atik
Right Now My **output.txt** file is - (as expected)
100
456.78
atik
*/
/* Appending the file that we just created - */
std::ofstream out_file2 ("outfile.txt", std::ios::app);
cout << "\nEnter something to write in file : " << endl;
std::string line;
getline(cin, line);
out_file2 << line; // writes to out_file2
/* Reading from file again - */
std::ifstream in_file2("outfile.txt"); // will open outfile.txt for reading.
if( !in_file2 ) {
std::cerr << "File didn't open. Error encountered." << endl;
}
char ch;
cout << endl;
while( in_file2.get(ch) ) {
cout << ch;
}
/*
Output (unexpected? why?)-
100
456.78
atik
*/
in_file.close();
in_file.close();
out_file.close();
out_file2.close();
return 0;
}
Now, my outfile..txt is - (as expected):
100
456.78
atik
Hello there
Then why is the output for in_file2 not showing Hello there? Why does it truncate the Hello there? Can someone please explain?
out_file2<<line;
doesn't flush (the use of std::endl in the prior code does), so if there's less than a full block of data read from std::cin, the data written to out_file2 is likely stuck in your user-mode buffers (and not visible when you open the file for read independently). Those buffers make I/O efficient by reducing the number of system calls when you're performing many smallish writes, in exchange for any buffered data not being visible outside of that file handle until the buffer is flushed (implicitly by filling, or explicitly by manual flushing or closing the file handle).
Simply changing that line to:
out_file2 << line << std::flush;
(or just .close()ing out_file2 once you're done with it) will cause it to flush properly and you should see the new data on opening it again for read.
Not easy to formulate that question, so I am sorry for any grief there..
I am writing to a csv file like this at the moment:
double indicators::SMACurrentWrite() {
if ( !boost::filesystem::exists( "./CalculatedOutput/SMAcurrent.csv" ) ) // std::cout << "Can't find my file!" << std::endl;
{
std::ofstream SMAfile;
SMAfile.open("./CalculatedOutput/SMAcurrent.csv");
SMAfile << "SMA" << endl << SMA[0] << endl; // .. or with '\n' at the end.
SMAfile.close();
}
else {
std::ofstream SMAfile;
SMAfile.open ("./CalculatedOutput/SMAcurrent.csv", ios::app); // Append mode
SMAfile << SMA[0] << endl; // Writing data to file
SMAfile.close();
}
return 0;
}
Each time the application runs, a new value is appended to the output file at the end:
SMA
32.325
I guess there is no way of just squeezing that new vector entry in there under the header( and over the number), but that is what I want to accomplish anyway.
So I guess I would have to read the existing output file back in,put it in a vector, and then replace the old file ? I started with smth like this:
double indicators::SMACurrentWrite() {
if ( !boost::filesystem::exists( "./CalculatedOutput/SMAcurrent.csv" ) ) // std::cout << "Can't find my file!" << std::endl;
{
std::ofstream SMAfile;
SMAfile.open("./CalculatedOutput/SMAcurrent.csv", ios::app);
SMAfile << "SMA" << endl << SMA[0] << endl; // .. or with '\n' at the end.
SMAfile.close();
}
else {
std::ofstream SMARfile("./CalculatedOutput/SMAReplacecurrent.csv");
std::ifstream SMAfile("./CalculatedOutput/SMAcurrent.csv");
SMARfile << SMA[0] << endl; // Writing data to file
SMARfile << SMAfile.rdbuf();
SMAfile.close();
SMARfile.close();
std::remove("./CalculatedOutput/SMAcurrent.csv");
std::rename("./CalculatedOutput/SMAReplacecurrent.csv","./CalculatedOutput/SMAcurrent.csv");
}
return 0;
}
...., but of course that just puts the new data in above the header like this :
32.247
SMA
32.325
..rather than this
SMA
32.247
32.325
I would rather this didn't become such a time- consuming exercise, but I appreciate any help on how I could get this done.
If you read in the first line from the input file you can use that to start the new file and it will leave the file pointer at the second line where the old data starts. Then you can write the new stuff like this:
if(!boost::filesystem::exists("./CalculatedOutput/SMAcurrent.csv"))
{
std::ofstream SMAfile;
SMAfile.open("./CalculatedOutput/SMAcurrent.csv", ios::app);
SMAfile << "SMA" << '\n' << SMA[0] << '\n';
SMAfile.close();
}
else
{
std::ofstream SMARfile("./CalculatedOutput/SMAReplacecurrent.csv");
std::ifstream SMAfile("./CalculatedOutput/SMAcurrent.csv");
// first read header from input file
std::string header;
std::getline(SMAfile, header);
// Next write out the header followed by the new data
// then everything else
SMARfile << header << '\n'; // Writing header
SMARfile << SMA[0] << '\n'; // Write new data after header
SMARfile << SMAfile.rdbuf(); // Write rest of data
SMAfile.close();
SMARfile.close();
std::remove("./CalculatedOutput/SMAcurrent.csv");
std::rename("./CalculatedOutput/SMAReplacecurrent.csv",
"./CalculatedOutput/SMAcurrent.csv");
}
IN IOS app, module written in C++ I am writing my data (map of basic strings and integers) to a text file. Using following method:
bool Recognizer::saveMap(const char * s)
{
if(trainingData.model && !trainingData.model.empty()) {
const string filename = string(s);
std::ofstream file(s, ios_base::trunc );
try{
if(! file.is_open())
{
file.open(s);
}
for (map<String,int>::iterator it=trainingData.idMap.begin(); it!=trainingData.idMap.end(); ++it)
{
cout << it->second << " " << it->first << endl;
file << it->first << endl << it->second << endl;
}
file.close();
}
catch(cv::Exception & e){
if(file.is_open())
file.close();
int code = e.code;
string message = e.err;
cerr << "cv::Exeption code: " << code << " " << message << endl;
return false;
}
std::streampos fileLength = iosFileSize(s);
cout << "Saved map to: " << filename << " length: " << fileLength << endl;
return true;
}
return false;
}
My contains one entry and console output indicates that two lines: string, string representing number have been written to my file.
Subsequent opening file for reading and reading using getline or using stream operator indicates that file is empty:
bool Recognizer::loadMap(const char * s)
{
std::streampos fileLenght = iosFileSize(s);
std::ifstream file(s, ios::in);
try{
if(file.is_open())
{
string name;
string lineName;
string lineTag;
int tag;
int count = 0;
while(getline(file,name))
{
if(getline(file,lineTag))
{
tag = stoi(lineTag,0,10);
count++;
cout << tag << " " << name << endl;
trainingData.idMap[name]=tag;
trainingData.namesMap[tag]=name;
}
}trainingData.personsCount=count;
file.close();
}
}
catch(cv::Exception & e){
if(file.is_open())
file.close();
int code = e.code;
string message = e.err;
cerr << "cv::Exeption code: " << code << " " << message << endl;
return false;
}
cout << "Loaded map from: " << s << " lenght: "<< fileLenght << endl;
return true;
}
I also copied from one of stackoverflow answers method returning file lenght and using it to verify lenghth of the file after write operation:
std::streampos iosFileSize( const char* filePath ){
std::streampos fsize = 0;
std::ifstream file( filePath, std::ios::binary );
fsize = file.tellg();
file.seekg( 0, std::ios::end );
fsize = file.tellg() - fsize;
file.close();
return fsize;
}
The file path passed to saveMap and loadMap seems to be legit. With path that the app could not write to, attempt to write caused exception.
There are no errors returned by write operation but both, attempts to read and iosFileSize() indicate that file is empty.
I am not sure if i need call file.open() and file.close() or file is open and closed automatically when output stream is created and later goes out of scope.
I experimented with those with the same result ( call to file.is_open returns true so the block calling file.open() is skipped.
What am I doing wrong?
I appreciate all responses.
It does not seem like you call file.flush(); anywhere in Recognizer::saveMap() after writing to the file stream. std::ofstream::flush() saves changes you've made to the file. Add file.flush(); between when you make changes to the code and when you close the file. See if that remedies your issue.
I also had the same issue. Using file.flush() everytime after you insert to a file can save your file.
However if you insert something like this, say,
file << "Insert This"; You will need to add file.flush().
But some people have issues, like if you just insert file << "Insert This" << endl; , this works fine. The key point here is that, std::endl calls flush() everytime it is used internally. you can say it is a shortend form of "\n" + flush().
I believe from looking at your code that you are overwriting your data when you open the file in the second program you should be using something like this.
std::fstream fs;
fs.open ("test.txt", ios::app)
instead of doing the ios::in
I am having some trouble with sprintf and fstream functions in order to create new text files for a POS program/check whether the file already exists. I don't know if i am doing something wrong because the same set of functions works fine in other places in my code...
This particular section of code is taking input from the user to create a details file, the name is made up of the first and last name details that were entered into the system. For some reason the new file is not being created. When I step through the program I can see that the custDetC variable is being filled with the correct data. I have also included the file existence check as it may or may not have something to do with the issue at hand...
Tony Mickel
sprintf(custDetC,"%s%s.txt", firstName.c_str(), lastName.c_str());
cout << custDetC << endl;
FileEX = FileExists(custDetC);
if (FileEX == true)
{
fopen_s(&custDetF,custDetC, "rt");
fprintf(custDetF, "%s %s\n", firstName, lastName);
fprintf(custDetF, "$d\n", phoneNo);
fprintf(custDetF, "%s $s\n", unitHouseNum, street);
fprintf(custDetF, "%s %s %d", suburb, state, postCode);
fclose(custDetF);
}
else
{
char *buf = new char[100];
GetCurrentPath(buf);
cout << "file " << custDetC << " does not exist in " << buf << endl;
}
}
bool FileExists(char* strFilename)
{
bool flag = false;
std::fstream fin;
// _MAX_PATH is the maximum length allowed for a path
char CurrentPath[_MAX_PATH];
// use the function to get the path
GetCurrentPath(CurrentPath);
fin.open(strFilename, ios::in);
if( fin.is_open() )
{
//cout << "file exists in " << CurrentPath << endl;
flag = true;
}
else
{
//cout << "file does not exist in " << CurrentPath << endl;
flag = false;
}
fin.close();
return flag;
}
You seem to be opening the file for reading, but you need to open it for writing.
Instead of "rt" use "wt" in fopen_s()
For some reason, Xcode will not take input from a file, while Visual C++ will.
When I run this program in xcode, the variables numberRows and numberCols stay 0 (they are initialized to 0 in the main function).
When I run it in Visual C++ they become 30 and 30 (the top line of maze.txt is "30 30" without the quotes).
Any ideas why this is happening?
void readIn(int &numberRows, int &numberCols, char maze[][100]){
ifstream inData;
inData.open("maze.txt");
if (!inData.is_open()) {
cout << "Could not open file. Aborting...";
return;
}
inData >> numberRows >> numberCols;
cout << numberRows << numberCols;
inData.close();
return;
}
There is something else wrong.
Unfortunately it is hard to tell.
Try flushing the output to make sure you get the error message:
void readIn(int &numberRows, int &numberCols, char maze[][100])
{
ifstream inData("maze.txt");
if (!inData) // Check for all errors.
{
cerr << "Could not open file. Aborting..." << std::endl;
}
else
{
// Check that you got here.
cerr << "File open correctly:" << std::endl;
// inData >> numberRows >> numberCols;
// cout << numberRows << numberCols;
std::string word;
while(inData >> word)
{
std::cout << "GOT:(" << word << ")\n";
}
if (!inData) // Check for all errors.
{
cerr << "Something went wrong" << std::endl;
}
}
}
interesting, so I followed the following suggestion from this post http://forums.macrumors.com/showthread.php?t=796818:
Under Xcode 3.2 when creating a new
project based on stdc++ project
template the target build settings for
Debug configuration adds preprocessor
macros which are incompatible with
gcc-4.2:
_GLIBCXX_DEBUG=1
_GLIBXX_DEBUG_PEDANTIC=1
Destroy them if you want Debug/gcc-4.2
to execute correctly.