C++ :: Writing Data On A File In Binary Mode Multiple Times
Oct 20, 2013
When you have to write data on a file in binary mode multiple times (without closing the file), is the put pointer left where you ended writing the last time, or do you have to use tellp() or seekp() again and again to make sure you write at the right place?
I would have the same question about the get pointer, does he stay in place after you're done reading something (without closing the file, of course), or do you have to set it back at the right place with seekg() ??
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Aug 16, 2013
I a want to write a code to convert a string into binary data for that i wrote a code its working perfectly but there is one problem , some of the binary data is written in 7bit and i want to convert it to 8 bit by adding 0 to the last.
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
[Code]....
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Mar 6, 2013
I am having problems either writing data to a binary file or reading from the file. Through the process of elimination I am posting the code where the data is written to file to see if I can eliminate that as an option. I know the data is being processed correctly because, through the use of another function, I can view the data.
I also know that fwrite must be including some padding because the file size ends up being 576 bytes after it is written instead of 540 bytes (the size it would be if no padding is used). Here is my struct:
Code:
typedef struct {
char teams[25];
float wins;
float losses;
float pct;
int runsScored;
int runsAgainst;
} STATISTICS;
Here is where I initialize it:
Code:
STATISTICS stats[12] = {
{"Anaheim Arrays", 0.0, 0.0, .000, 0, 0},
{"Pittsburg Pointers", 0.0, 0.0, .000, 0, 0},
{"Indianapolis Integers", 0.0, 0.0, .000, 0, 0},
[Code] ....
And here is the function that writes my data. The sA array is only used to change the scheduled games based on the variable week.
Code:
void schedule(STATISTICS stats[]) {
FILE *f;
int sA[12], week = 0, runsPerGameA = 0, runsPerGameB = 0, runsAgainstA = 0, runsAgainstB = 0;
int index, a = 0, b = 1, i = 0;
[Code] .....
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Jul 9, 2014
fstream ifs;
ifs.open ("data.str", ios::binary | ios:ut);
char *data1 = "data1";
char *data2 = "data2";
ifs.write(data1, strlen(data1));
ifs.write(data2, strlen(data2));
when i this,data2 is not going under data1, i thought each write starts on a new line?
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Apr 5, 2014
so i have to read a text file with an unknown number of lines and allocate memory to for the number of items in the text file.currently i read the entire file(counting the number of lines). i allocate memory according to the number of lines read and then use fseek() with an offset of zero to allow for the second read .
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Sep 28, 2013
I have a file in which I have written a structure called "Record".
Here is the struct definition:
Code:
#define IDSIZE 10
struct Record{
char id[IDSIZE];
int score;
};
Here's the code where I wrote to the file:
Code:
Record record;
char* id = "H12345678";
int score = 50;
record.id = id;
record.score = score;
file.write((const char*)&record, sizeof(record));
}
Here's a screenshot of the file in windows: [URL].... To the left is the id, 9 characters. To the right, well I'm assuming that's the score that I wrote.
And here's the problem, reading from the binary file:
Code:
Record record;
fstream file(argv[1], ios::in | ios::binary);
if(!file){
cerr << "Could not open the file." << endl;
return 1;
}
char* id = new char[IDSIZE];
[Code]...
The ID reads perfectly. The score...always returns 0, despite that it should show "50".
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Apr 2, 2013
I am writing a double number in Binary format to the console of program A (in FORTRAN) with the following code:
Code:
REAL*8 A
A = 12.54
INQUIRE(6, name = xstring)
OPEN(1,file=xstring, access='stream',action='write')
WRITE (1) A
CLOSE(1)
And trying to read that number by program B (in C++) which is connected to program A by anonymous pipes. Following is the reading part of program B:
Code:
#define BUF_SIZE 5000
BOOL bSuccess = FALSE;
char Buf[BUF_SIZE];
DWORD dwRead;
for (;;) {
bSuccess = ReadFile( V_hChildStd_OUT_Rd, Buf, BUF_SIZE, &dwRead, NULL);
if( ! bSuccess || dwRead == 0 ) break;
}
Note: V_hChildStd_OUT_Rd is a handle to the output of program A.
After running the program although bSuccess becomes TRUE, Buf array does not include the number (12.54) that I am expecting. If I do the same process without using the binary format it works fine and I can read the number. I know somethings wrong with the writing or reading of binary data but I do not know what it is.
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Mar 8, 2013
How to read and write an arbitrary number of bits from/to a file stream.
For instance, how to repeatedly read 9 bits from a file, then change to 10 bits, then 11 bits, and so on?
Obviously one way is by doing a lot of bit shifting, and masking. But honestly, I'm too dumb to get it right. Then I thought about using std::bitset and std::vector<bool>.
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Mar 16, 2012
Two questions:
1. I have some vector<unsigned char> containing binary data. I would like to combine them into one std::string. How is the correct way to accomplish this?
This is my best guess for sample code:
Code:
vector<unsigned char> data; //conatins some data
vector<unsigned char> data2; //contains more data
string temp(data.begin(), data.end());
temp.append(data2.begin(), data2.end());
Will this code work with binary data, or will it null terminate?
2. A similar problem.. I have some unsigned char* variables, and I want to combine them into one std::string. How can I accomplish this? will the member append() work here? or will it null terminate? Something like:
Code:
unsigned char* data; //conatins some data
unsigned char* data2; //contains more data
string temp(reinterpret_cast<const char*>(data));
temp.append(string(reinterpret_cast<const char*>(data2)));
Will the above sample code work without null termination?
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Aug 7, 2013
I'm currently working on a server for handling clients in a 2d online game and I wrote some regular fstream file code for handling the file that stores their information and I was about to implement it into the server, then I realized there might be a problem having it open multiple times concurrently, so I googled it and came up with
posts like
[URL]
I'm wondering if I can just treat it like everything else or will I have to do something specific for opening on multiple threads?
p.s. I did read those posts but I'm very new to multithreading
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Mar 10, 2014
So I'm trying to write an array of integers to a binary file. He's my code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
[Code].....
I know that it is an array of characters right now, and I will be using the reinterpret_cast when I finish my program. Anyways, when I run the executable, it only writes 1234 to the file. My assumption was that the sizeof() was not being set properly, but even manipulating that won't fix it.
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Dec 6, 2013
Following is the program I wrote it basically takes 9 inputs and then save them into binary file. then print out the data stored in binary data and find inverse of it then print the inverse out. but its stuck in a loop somewhere.
Code:
#include <stdio.h>
int main() {
int a[3][3],i,j;
float determinant=0;
int x;
FILE *fp = fopen ("file.bin", "wb");
[Code] .....
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Jan 21, 2013
tell me where the errors in the below code are?
Extra info:
getrowsize() gives the size of a row in bytes (see VGA CRTC register).
getVRAMMemAddrSize() gives the size of a pixel in memory (1=byte,2=word,4=dword)
set/getBitPlaneBit(startaddr,plane,offset,bit[,on when writing]) sets/gets a bit on a specific bit plane offset (start addr is the start address register from VGA,
plane is the plane to read/write,
offset is the offset within the plane,
bit is the bit to read/write (0-7),
[on(when writing) is the value of the bit)]
[code]....
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Feb 17, 2014
cant write to binary file
#include <stdio.h>
#include <stdlib.h>
typedef struct {
int number;
} something;
void main() {
int numbers[10]={1,2,3,4,5,6,7,8,10,12};
[Code] .....
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May 30, 2013
Both arrays arr and pointers are the same size. I am having problems reading pointers from file into a new int array.
FILE* ky_pt=fopen("stashedclient","ab");
write(fileno(ky_pt), pointers, sizeof(pointers) );
pointerindex=lseek(fileno(ky_pt), 0, SEEK_CUR );
printf("pointerindex after writing array %d
[Code] .......
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Aug 21, 2014
I would like to write a complete structure array to a file and read it back, recovering all the data. I have tried the following:
Code:
#include <stdio.h>
#include <string.h>
#define NUM 256
const char *fname="binary.bin";
typedef struct foo_s {
int intA;
int intB;
char string[20];
[Code]...
//---------------------------------------------------- but the mac field is reading back some random value repeatedly. Why is that? And how do I fix this?
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Sep 7, 2014
I have a question about SDL and drawing sprites (SDL surfaces). My idea is that the user can create a wall of separate sprites by create one sprite each time in the current mouseX and mouseY position, when the user push down the e-key. The problem is that I have no idea how I could draw the same sprite multiple times without to delete the previous one.
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Mar 21, 2013
Im programming client/server app that client provide the file name then the server send it to client then the client will save it ..this is part of code in client
Code:
char buffer[1024];
printf("FIle is being downloaded ...
");
printf("%s
",buffer);
}
[code],...
So i have 2 problems ::
1st one is when i write to file the file permission i cant define it with data type mode_t ,so the file does not open at all after creation...
2nd one is: the data in buffer is less than 1024 ,the data wrote to buffer but with garbage data . How to make the file read only the real data with garbage ??
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Aug 19, 2013
I am trying to write one data to my file(myfile.#abc).
Code:
FILE * pFile;
int iLast Col=3;
fopen_s (&pFile,_T("myfile.#abc"), "w+");
fwrite ((char *)&iLastCol,1,2,pFile);
fclose (pFile);
Inside file ia getting a value like this
[ETX][NULL]
What is mean by ETX,Like that some other variable I amgetting [SUB],[STX]etc.what is this?
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Dec 6, 2013
I need to find inverse of a matrix data in binary file should be used to form matrix.its not finding inverse correctly rest is working good.
Code:
#include <stdio.h>
void createbin();
void display();
void inverse();
int main()
{
createbin();
display();
inverse();
[Code] ....
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Sep 15, 2014
I've been stuck on this for hours, and have scoured the internet for any insight on this particular issue with no luck.
I'll simplify the problem here. I have a lines in an input file:
John Smith 1234 Main St New York
Carol Thomas 5678 5th Ave Columbus
...
and I am reading into character arrays using code like this:
infile.getline(name,20);
infile.getline(street,15);
infile.getline(city,10);
but when I print the output using something like this:
outfile << "Owner Name: " << name << endl;
outfile << "Address: " << street << city << endl;
(let's pretend I included spaces between the address components, which I omitted to save space)
I get an output file of:
Owner Name: John Smith
Address:
The output stops after the name variable, which I believe is stored correctly. I don't think anything is storing in the address pieces, this is the problem.
I think it's because I'm not using getline() properly in this case. Can you string together multiple getline()s like that?
If this was my design, I'd read in strings instead, but that is not possible in this case.
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Sep 19, 2014
I've been working on a program that uses a reference counting class that I've written which works fine for objects that inherit from it however I now need to have the following setup:
class SBComponent : private Refcounted { /*stuff*/}
class ProxiedComponent : public SBComponent, private Refcounted {/*stuff*/}
The compiler gives the following warnings
warning: direct base ‘Refcounted’ inaccessible in ‘ProxiedComponent’ due to ambiguity
And then several repeats of the error:
error: request for member ‘bk’ is ambiguous
Back *b = bk<ProxiedComponent>();
bk is a templated function that's defined in Refcounted and returns a pointer of type <template arg>::Back (ProxiedComponent::Back in this case).
I don't understand why the call to bk is ambiguous as although there's two instances of Refcounted (there needs to be with the way I've designed it so I can't make it virtual) it's inheritance is private in both cases so there should only be one instance of it visible in ProxiedComponent.
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Nov 6, 2014
I've been struggling with an object when trying to add it to a list with [Listname].push_back. You see, I have a list with some objects that will be rendered in the screen (Called objects) and a function to create a text box with some text. The function in question is the following:
void reprEv(int evNum, ALLEGRO_BITMAP *txtbxim) //Event to call, default text box image.
{
textBox *txtBox = new textBox("Line 1 ", "Line 2 ", "Line 3 ", "Line 4 ", "Line 5 ", textboximage);
objects.push_back(txtBox);
[Code]....
(txtNum is increased then space is pressed, and when certain screen (maxScreen) have been shown, then it will go to the playing state)
My problem begins when the text box is created, because it's supposed to add only 1 text box to objects list, but instead adds hundreds of text boxes to objects.
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Jan 5, 2015
Code to write data(Double type e.g 12345.67891) in text file like pattern given below. Remember to put tab between each column.
-----------------------------------------------------
Column1 Column2 Column3
Value 1 Value 2 Value 3
Value 4 Value 5 Value 6
Value 7 Value 8 Value 9
----------------------------------------------------
& Also how to read data from this file.
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Jan 7, 2015
I'm facing a problem regarding data entry in file.I'm making arrays which terminates when I press enter key but problem is that character at 0 index is not in file while rest of the indexes are there .. In other words,while writing on file my first character of any array got missed and did'nt present in the file ..
char CNIC[10000];
std::fstream file1;
cout<<"Enter CNIC's >>>>>>>>>>> "<<endl;
file1.open("Nadra database.txt",std::fstream::in | std::fstream::out | std::fstream::app);
if(!file1) {
cout<<"File was not open";
} else {
for(int i=0;i<11;i++)
[code]....
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Apr 17, 2014
My application calls malloc in multiple subroutines, finally releasing all using free. This is done using my zalloc library (see my other post: [URL] .....
Somehow, when the applications tries to detect the available ammount of memory at the end of the test (allocating, freeing, testing), the freemem function gives me about 4-6MB less memory than at the start of the test? (out of 21MB available on the device at the start).
All memory is allocated and freed using the malloc/free routines within the library, with the exception of the SDL functions, which are registered externally on allocation and release.
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