why I cannot get correct value for the third element in my struct?In the second file where I'm reading from memory I allocate some space. Is this incorrect in some way? I'm running this on a Linux machine.
Say now I have a dll, loaded and run by a 32bit program. One of the things that I access from the program in the dll are several 1024x1024 int buffers. However I would like to put some data into those buffers from a external process. And I would like a separate thread in that external process for each buffer. Is there any way I can make that memory space accessible to the external process so I can use my own multi threaded memory transfers to pass that data over provided I ensure that the original process doesn't try to do anything with that data? And I would like to do this without resorting to the Read/WriteProcessMemory functions which are not threadsafe. In short, I want to set up direct memory access between the 2 programs without creating any intermediate shared memory buffers ie I want to set permissions for an existing memory space. Is this possible?
I am not so experianced with c++ myself, but I need to evaluate if a certain idea might work.
I am working with a system for automation purposes that is running on a realtime OS in parallel to windows. Windows and the RTOS exchange data via shared memory. The application in the RTOS is compiled in C++. Now I would like to be able to influence the some data manipulation tasks in the RTOS application without changing the code of the RTOS application. So a concept like calling a dll.
My idea was to create a class with virtual methods in the RTOS application. The objects that are used should then be created on the Windows side with the same class prototype, but specific implementation of the virtual methods. The objects should then be moved to the shared memory, where they are used by the RTOS application.
Is something like this possible or am I completly on the wrong path?
In interprocess communication(IPC) when processe have to share data among each other,why cant they all connect to one single file and share data with basic file handling functions such as read and write?
Why do we need
shared memory(shmget shmat(),shmdt()..etc) and mapped memory(mmap(),munmap()..etc)
I have one requirement to store an array of structure at shared memory. Also the shared memory should have one counter to store number of elements in the array.
I tried to look at some placed but didn't find anything relevant.
So my first question, is it possible that we can store two things on same shared memory. And second if not then how to achieve the same?
I am trying to initialize a 2D char array of strings into POSIX shared memory to be shared between 3 other processes. There are plenty of tutorials on how to use a pointer to share a single string or an integer between processes, but I could find no examples on how to initialize 1D or 2D arrays using mmap(). I have posted what I have so far below. It is the first program, which creates the shared memory object and initialize the array char files[20][2][100] with the value files[0][0][0] = ' '. What is the proper method to initialize and share an array in C?
(program initializes shared memory object and array)
I was trying to put mutex lock on shared memory but my code is not working. What I want is that if some process is putting something on shared memory segment, other process should not be able to access that segment. For testing , I create a server program which put data in shared memory and client program which access the data.
To test it, I put break point after:
pthread_mutex_lock(&(init_lock));
But I see that client program was able to access shared memory.
I'm working on a project that is supposed to create 3 processes. Process 1 should count from 1 to 100,000. Process 2 from 1 to 200,000. Process 3 from 1 to 300,000. I've written the basic code of it but my processes aren't printing out very accurate numbers.
I have a question concerning shared memory (in linux-environment). In our company we currently have an application that is restarted once in a while. There are multiple instances running of this application (on different physical machines), and all access the same centralized database. Because of IO and Network bottleneck the start gets very slow, and takes about 10 Minutes. Besides some new data, most of the data stays the same, so reading from the database again is quite redundant. An idea is to write all relevant object to a shared memory segment, when the application is shut down. A second dummy process attaches to the same shared memory (just so that some process is still attached). If the application is restarted, it is attached again to its shared memory, and reads it to its own adress range again. There might occur a difference regarding the data so it might me necessary to load some new data afterwards, but that is different problem.
The current idea is to serialize all Objects (could be about 1-2 Gigabyte) with Apache Thrift, and write them into shared memory. With Thrift the data is more or less ordered, so creating the objects anew is possibly easier (not sure here).
My Question is:
- Does it even make sense to consider shared memory in this scenario. I've read a lot stuff about in the last few days, and for now I don't see big disadvantages (except if the application crashes, in this case I've to read from database again). On the other hand I don't know how to really implement this functionality (as I'm no experienced Developer)
- Should I aim for Boost::Interproces, considering even memory mappable files, or stay with the traditional shmat (and stuff..)?
- I guess 1-2 Gigabyte shared memory will be necessary. This amount is only needed in the gap between application shutdown and restart. Will the sheer amount of needed shared memory be a problem (all examples I found just used a few Bytes or Kilobytes)
I am trying to write a client/server application that takes input to an array of structures from the user,stores the data in a shared memory segment and then writes the same to a file when I close the application. How do I get started? And how do I ensure that the server stores the data correctly? Also, the server needs to be a concurrent server that accepts connections from multiple clients.
the question is; Write a program that prints out the memory addresses of each element in a two-dimensional array. Check to see if the values printed out make sense to you based on the way I explained it before.
Below is the code I have done. I am having problems printing the "-" sign to keep formatting with the board when the user enter in different dimensions other than [4][4].
Code:
#include <iostream> using namespace std; void printTable (int x, int y) { int **p_p_twoDimension = new int* [y]; for (int i = 0; i < y; i++) { p_p_twoDimension[i] = new int [x];}
I am trying to store each value of a column from a text file into an dynamically allocated array, which needs to be globally declared for further usage in the program.The input textfile contains the following:
#include<stdio.h> #include<stdlib.h> #include<string.h> int main() }
[code]....
The commented printf line gives the entire values of the column, which proves that the file is correctly being read.But on compiling this program I get both compiler warnings and finally segmentation fault.
I CANT use std::string, classes, constructors for this project. I am required to use this archaic method of c-style strings with dynamic memory allocation occurring outside the struct.. i know its not the best way to go about this, but there's nothing i can go. I have a struct:
struct card { char *suit; char *rank; int cvalue; }
I've created a pointer of size 52 for my deck
card *deckPtr = new card[52]; card *deckHome = &deckPtr[0];
I then try to use
for(int i=0;i<52;i++) { (*deckPtr).suit = new char[8]; (*deckPtr).rank = new char[7]; deckPtr++ } deckPtr=deckHome;
I am essentially trying to fill in these arrays from a card file, but I cannot make it past running the program, i get sa seg fault which I dont understand why.
I dynamically allocate memory in my card read in function..
Consider I have a vector of strings and then I use an istringstream to read each word of each element in the vector, why do I nescessarily use an istringstream?
This is the code that does what I just described (I think)..
I am having a structure called matrix as shown below to represent a matrix your read from a text file.
struct matrix { double mat[30][30]; //content of the matrix mat int row; //number of row in the matrix mat int col; ////number of col in the matrix mat };
Declare 3 variables of structure matrix, m1, m2 and m3 in main to be used as describe below.
Task:
1.Write a function void readFile(char *filename, matrix *m) that will read a matrix from a text file and copy to the structure matrix m.
I am trying to use struct to store variables from a text file and use them in the main program. I have first tried running the program without using struct and declaring the variables within the main program and it runs fine. But after using struct, it gives no compilation error and a segmentation fault as output. Also, if the size of file/variable size is unknown can I declare variables as char string[]??
The code is as below:
Code:
#include<stdio.h> struct test { char string1[10000];
I have a C program. Within it, I would like to embed either a file or a pre-assigned variable. I would prefer a method that is platform independent.
I am using the data type "RSA" from <openssl/rsa.h>. I have a key file in PEM format, but I would like to embed an RSA object in the program instead. I tried creating a char array and then casting the pointer, but that caused some sort of illegal casting issue. I tried using memcpy but I haven't been able to get it working that way. What is the best way of going about this? Is it possible to read a file directly from a memory buffer?
I'm not sure if I should do this with malloc or a char array. What I need to do is create 4 methods to read and 4 to write to memory like this (and it has to be fast):
Code:
char GetByte(char* memory, int offset); uint16 GetInt16(char* memory, int offset); uint32 GetInt32(char* memory, int offset); char[] GetString(char* memory, int offset);
So basically memory is the malloced memory and the offset is the position I want to read at.
I'm not sure if there's already a way to do this and maybe I'm overlooking something.
i want to write a program that can access to variables and methods of another program. I ques for access to variables need to read memory, but about methods?how i can use methods and call them?
I decided I wanted to make a proper programming language with a virtual machine and bytecode. I used this tutorial: [URL] .....
As a starting point for my project. So far I have modified it to allow for 32-bit addressing so that I can theoretically use 4GB in my programs. Now the problem I'm having is creating the memory.
Question:
I'm not sure if I should do this with malloc or a char array. What I need to do is create 4 methods to read and 4 to write to memory like this (and it has to be fast):
char GetByte(char* memory, int offset); uint16 GetInt16(char* memory, int offset); uint32 GetInt32(char* memory, int offset); char[] GetString(char* memory, int offset);
So basically memory is the malloced memory and the offset is the position I want to read at.
