C++ :: RAM Disk And Pointer To Content In File
Mar 3, 2014
When we are using RAM DISK - the files are stored on the RAM. From what I understand (and saw many examples) in order to read data from file (the file which locate on the RAM) - I need to use the read function.
Is there a chance to get char* (or any pointer) to the content of the file without using the read function ?
If the file locate on the RAM, it seem that it is like I have a buffer on the RAM (like an array which was dynamic allocated) and in the case of a buffer on the ram -> we can use pointers to the data without reading all the data.
example:
class CDATA {
int nValue1;
int nValue2;
double dValue3;
double dValue4;
char achBuf[10];
[Code] .....
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Oct 30, 2013
I wrote a code and I found a small problem with the display of the pointer
here is the code :
Code:
#include <stdio.h>#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[]) {
[Code]....
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Sep 12, 2013
I made a text file. I can do all File I/O functions in c. no problem! except that "I want to get the memory address of the beginning of that File", so that I can access each character of the file by incrementing memory address.
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May 26, 2013
Here is a working C++ program and its output that reads the names of a certain number of functions whose names are written in a disk file that provides the control parameters in a near-real time fashion. Based on this information, the program calls those functions whose names were given in this text file as parameters. The method I have used is to build a map of functions that connects the names of the functions to the actual functions. Once this map is created, then it is very easy to iterate in such a way that only those selected functions are called.
So far this is working well, and it makes the logic of the code easier because ultimately there will be a large inventory of functions (probably hundreds of functions), and this way of pre-building a map of functions avoids writing hundreds of if statements in the code. Of course, pre-building this reusable map in the background is still equivalent to writing that many if statements, but at least it makes the code very compact and much more automatic, since it is done only once.
But I now have a related question: In this case (when the selected subset of functions to call is given as incoming data as in this example), does C++ make it possible to avoid using maps of functions, by directly applying the string variable that holds the name of the function in order to call the original function immediately For instance, if a string variable s = "MyFunction", then is there a more direct way of using this string as if it were the actual function whose name is spelled exactly in that way? This would make the code even more compact.
Here is the sample test code for the map of functions, and its output:
First of all here is the text file "FileForNamesOfFunctions.TXT" that contains the part of the "data", which is the set of functions select from from the inventory and only call these:
Code:
function2
function3
function5 And here is the C++ code that uses this "data":
Code:
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
[Code] ....
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Mar 15, 2013
The Objective Of This Program Is To Create A File To Write Text And Read Back The File Content. To Do That I Have Made Two Function writeFile() To Write And readFile() To Read.The readFile() function works just fine but writeFile() doesn't.
How writeFile() function Works? when writeFile() function Execute It Takes Characters User Type And When Hit Enter(ASC|| 10) It Ask "More?(Y/N)" That Means What User Want? Want To Go Next Line Or End Input?
If "Y" Than Inputs Are Taken From Next Line Else Input Ends.
But The Problem Is When Program Encounters ch==10 It Shows "More?(Y/N)" And Takes Input In cmd variable.If cmd=='Y' I Mean More From Next Line Than It Should Execute Scanf Again To Take ch I Mean User Input.But Its Not!!! Its Always Showing "More?(Y/N)" Again And Again Like A Loop.
Code:
#include <stdio.h>
void writeFile(void);
void readFile(void);
int main(){
[Code].....
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Mar 28, 2013
Can i edit records stored in file without rewriting whole file again .?
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Apr 3, 2013
I am using c to read and write contents of a file into other:
FILE *ptr;
status_t status;
uint32_t block_size, result;
uint32_t num_blocks;
char temp_buffer[1024];
}
[code]....
Is there way to see the binary content of this file.
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Sep 18, 2013
A user enters a query and other users reply to it. But it creates a problem here. After adding queries, if I wish to reply to query in between then it adds a redundant entry in file. 1st entry is the original query without reply and 2nd entry is the same query now with a reply added. I want only 1 entry of the query along with replies.Here is the code:
Code:
#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
#include "var.c"
int check_count();
void add_query();
void add_reply();
}
[code]....
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Sep 24, 2013
I'm trying to read all content from a text file into a string. This is the code I'm using for it (I know there are other, maybe better ways to do it but I'd like to stick to this for now):
char* buffer;
std::string data;
FILE* fp = fopen("textfile.txt", "rb");
if (!fp) {
printf("Can't open file");
[Code] ....
So my problem is that I get an exception when I try to free the memory -> 0xC0000005: Access violation reading location 0x51366199
I even get the exception when I try to free it immediately after calloc() but why this is.
And if I use buffer = (char*)malloc(lSize); I don't get any exceptions.
So, why this fails and what I'm doing wrong.
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Jan 28, 2013
I would like to store the entire content of a file in a single c-string variable or in a standard string class variable. Is there a function that will do this for me? I am familiar with functions that get one character or one line at a time but I don't think I've encountered a function that gets the entire file. Does this function keep or disregard the end-of-line character? If no such function exists, I would write my own function to create and return such a variable.
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Jun 8, 2014
I need to develop a simple program, i have 2 variables (begin, end), and i need to search in a file, And extract the string between the Begin and the End variables to a new File, For Example:
my text file: file.txt:
some text here<StartHere>more text here</EndHere>text text
C++ Program:
//Declear 2 variables
strcpy_s(begin, string("<StartHere>").c_str());
strcpy_s(end, string("</EndHere>").c_str());
//And now, search in the Text file, And Extract the text between the begin string and the End string.
<...>
The Result should be: NewFile.txt with the content:
<StartHere>more text here</EndHere>
That's it!, Here is what i have for now:
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
int main() {
int ocurrences_count = 0;
int ocurrences2_count = 0;
char word[20]; //this array will save user input
[Code] ....
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Feb 8, 2014
I am trying to write a program for a library system that allow stuff to add, remove, view and delete customer. i try to use file to store data and i open the file in mode read then i store then i put the content of the file into a structure. now the problem started it is only showing me haft of the content and here is the coding.
#include <stdio.h>
# include <windows.h>
# include <stdlib.h>
#include<string.h>
#include<conio.h>
void search(int s,struct books eli[20]);
void view(int x,struct books eli[20]);
[Code] .....
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Dec 10, 2013
I need a large string vector for file content manipulation.
v1.max_size() gives me 153 391 689.
But if I make a test by looping a vector pushing back strings it crashes around 16 - 26 000 000 though I still have a lot of ram (1GB left).
How come and why isn't vector size limited by ram instead?
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Nov 29, 2014
Code software that, from an original text file, generate another file with the text content in upper case.For exemple:
entrence:
luke
tom
alex
outings:
LUKE
TOM
ALEX
My code so far:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
}
[code]....
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Aug 30, 2013
Any algorithm or function to rotate a displayed circle. To turn it 360 degrees like a car-tire. (It's needed to turn a turn-table in a model-railrod control program) .....
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Mar 30, 2014
I'm trying to write a program that writes data to a disk in C++ without caring about it's file system. Here is what I can do so far:
#include <iostream>
#include <unistd.h>
#include <fcntl.h>
using namespace std;
char buffer[] = "Wow! I'm writing this data to a disk without puttting it into a file!";
int main(){
int Disk=open("/dev/sdb",O_RDWR);
write(Disk,buffer,sizeof(buffer));
close(Disk);
return 0;}
But this program can only write ASCII characters to the disk. But what if I want to mainipulate bits on the disk, how would I do that?
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Dec 29, 2013
lets say I have a char array with four elements but only one char is used, does it write four elements or just one?
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Oct 1, 2013
So this code compiles without any problem but it is not producing the correct output. I know there's a problem in either my getBlock or putBlock functions but I can't see it.
Currently the output is "Should be 32 1s: "
"Should be 32 2s: "
There should be 32 1s and 32 2s and nothing is coming out.
#include <iostream>
#include <fstream>
using namespace std;
class Sdisk {
public :
Sdisk(string diskname);
[Code] .....
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Feb 9, 2014
I am using Visual C++ to write an app. One problem is that the application will allocate a lot of object instances of a specific class CMyObject, maybe 400, 000. This will cause "Out of memory" error when total allocated CMyObject reaches 400,000.
To solve this problem, I just wonder when a new CMyObject instance is created, is it possible to specify so that the instance will allocate on a disk cache, or file mapping instead of the memory space?
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May 31, 2013
I am trying to get text file and read only first 100 lines of the text content using c/c++. how can i do it?
is it something like string line;
getline(stream,line);
??
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Apr 21, 2012
Basically, I want to write an image to disk in parallel with an algorithm that is processing that same image. The code is really simple:
Code:
string ProcessImage(System::Drawing::Bitmap ^bmp, System::String^ targetFile) {
bmp->Save(targetFile);
System::Drawing::Bitmap^ bmp8 = BitmapConvertPixelFormat(bmp, 8); //<-- a function I wrote which converts the 32bpp I am passed into an 8bpp one
string results = Analyze(bmp8); //<--- takes a good bit of time
return results;
}
What would be the fastest way to do this? Any libraries with a code sample. I would prefer one that is within .NET or native C++ just to avoid having to link into many different libraries.
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Nov 23, 2014
Code:
_int64 free_space_64bit;
PULARGE_INTEGER lpFreeBytesAvailable, lpTotalNumberOfBytes,lpTotalNumberOfFreeBytes;
//char currentPath[MAX_PATH];
//GetCurrentDirectoryA(MAX_PATH, currentPath);
GetDiskFreeSpaceExA("H:C", lpFreeBytesAvailable, lpTotalNumberOfBytes,lpTotalNumberOfFreeBytes);
free_space_64bit = lpFreeBytesAvailable->HighPart << 32 | lpFreeBytesAvailable->LowPart;
This directory "H:C" does exist, if I comment out the GetDiskFreeSpaceExA line, the program doesn't crash, but it leads to some peculiar results (some uninitialized and random value, but at least it doesn't crash)
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Jan 23, 2015
I am reading my file (20GB) line by line using boost like this
PHP Code:
boost::interprocess::file_mapping* fm = new boost::interprocess::file_mapping("E:Mountain.7z", boost::interprocess::read_only);
boost::interprocess::mapped_region* mr = new boost::interprocess::mapped_region(*fm, boost::interprocess::read_only);
char* bytes = static_cast<char*>(mr->get_address());
An exception is thrown in the second line while allocating memory for mr.
I use boost because it can also work in Mac which my code will be ported to.
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Jan 15, 2013
Opening large files in c++. In my application, i am trying to save video as long as users have space in harddisk. What I am trying to do is when user is recording video i am trying to append the video data in to the file. The problem is that every time file size reach over 2GB my software crashes.
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Jan 7, 2014
In a C++ map, is there any way to search for the key given a content? Example:
I have this map:
map<int,string> myMap;
myMap[0] = "foo";
Is there any way that I can find the corresponding int, given the value "foo"?
cout << myMap.some_function("foo") <<endl;
Output: 0
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Dec 17, 2014
I need to display all the content of the ( codedParams & modeParam ) in the next piece of code
struct SAOOffset {
SAOMode modeIdc; // SAOMode is an enumerator
Int typeIdc;
Int typeAuxInfo;
Int offset[MAX_NUM_SAO_CLASSES];
SAOOffset();
~SAOOffset();
Void reset();
const SAOOffset& operator= (const SAOOffset& src);
[Code] .....
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