How can i use memory pool with a char array?
Is there a way to allocate memory somewhere in the middle of the array?
i.e. allocate memory in chunks.
E.g. allocate 24 bytes at location arr[56] in 256 byte array.
Similarly how can i deallocate that memory?
General Purpose: Delete all "white spaces" in text file, until the read-in char is _not_ a whitespace (mark as start of text file).
Problem: Cannot seem to shift char's over properly. (I think my problem is the inner loop - however other code may lead to this problem - I do not know)
Code:
#include <fstream>
#include <iostream>
using namespace std;
bool trimWhiteSpace(fstream &file, char * charMemoryBlock) {
if (!file.is_open()) {
[Code] ....
I'm the author of a realtime MIDI software called ChordEase which makes use of the MIDI aspects of the multimedia API, specifically MIDI input callbacks. In XP and before, these callbacks originated in the kernel and therefore had realtime priority by definition, but from Vista on, they originate in thread pool threads, and have a priority of zero. This is a problem because at priority zero they can be blocked by the GUI thread, causing serious latency, and I have proved that such blocking occurs.
I have experimented with raising the callback thread priority, using either of the following methods: 1) calling SetThreadPriority within the MIDI input callback function, and then setting a flag so that it isn't done repeatedly, or 2) creating a DLL that catches thread creation via DLL_ATTACH_THREAD in DllMain, and calling SetThreadPriority there. The first method is slightly wasteful since the flag has to be tested for every MIDI input event, but it also has the advantage of only affecting the MIDI input threads, whereas the second method affects all threads in the pool regardless of what they're used for. Neither method appears to cause any harmful effects but they make me nervous*. Other possible methods would include 3) using the thread pool API to raise the priority of the pool (assuming I could gain access to the pool handle somehow), or 4) permanently lowering the priority of the GUI thread, which I'm very reluctant to do because of the risk of unintended consequences.
I'm assuming the MIDI input callbacks are using threads in the default thread pool though I haven't actually proved this. Assuming that's so, are these threads private to my application, or is my application sharing them with other applications? Is there a safer way to achieve the result of increasing the priority of MIDI input callbacks? It's incredibly frustrating that MS would change the behavior of MIDI input callbacks so drastically without even telling anyone, but that's how it goes!
[URL] ....
*See for example theses warnings about changing thread pool priorities : [URL] ....
I've made a code to check whether or not a save file has been created correctly, but for some reason it always returns this line: readdata[qa]=='1' as true. in which qa is the counter I use in a for loop and readdata is a character array consisting of 50 characters that are either 0, 1 or 2.
this is the entire code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
[Code]....
at first is also went wrong at line 22 and also returned that as true, but then I added brackets and it worked.
I am trying to concatenate two words from a file together. ex: "joe" "bob" into "joe bob". I have provided my function(s) below. I am somehow obtaining the terminal readout below. I have initialized my memory (I have to use dynamic, dont suggest fixing that). I have set up my char arrays (I HAVE TO USE CHAR ARRAYS (c-style string) DONT SUGGEST STRINGS) I know this is a weird way to do this, but it is academic. I am currently stuck. My file will read in to my tempfName and templName and will concatenate correctly into my tempName, but I am unable to correctly get into my (*playerPtr).name.
/* this is my terminal readout
joe bob
<- nothing is put into (*playerPtr).name, why not?
joe bob joe bob
seg fault*/
/****************************************************************/
//This is here to show my struct/playerInit
[Code]....
I need to do a function that copy every word from a text to a char word. How can i do it?
View 5 Replies View RelatedI wrote this simplified version of a program i am writing that parses data in UDP packets. In the process of doing so i pretty much answered all my questions and fix all the problems i was having.
decodeSystemMap function will be in loop, and will proccess packets that have mostly the same data, only a few items will be added or changed or deleted.
whats the best way to check if there are any new, deleted, or removed items in the packet and only modify those?
Is there anything unsafe / dangrous about the way the code is now?
Code:
/* * File: main.c
* Author: david
*
* Created on May 23, 2013, 11:57 AM
*/
#include <stdio.h>
#include <stdlib.h>
[Code] ....
I have the following code which attempts to assign a u_int8 array of 256 to an unsigned char[256]:
Code:
unsigned char testData[256]=pSample->data;
I get the compilation error:
error C2440: 'initializing' : cannot convert from 'const uint8_t [256]' to 'unsigned char [256]'
What is the safe way to cast or convert here?
1) int *a=new int[10]
2) int a[10]
What are the exact differences in these two types of methods of allocating memory for an array ? When does 1st method is useful and when does 2nd ?I also read somewhere that in Ist method memory is allocated from heap but i don't know from where memory is allocated in 2nd method and what difference these memory allocations causes.
Here is my code:
Code:
class Base {
};
class Derived1 : public Base {
};
class Derived2 : public Base {
} class Bar {
public:
void SomeFunc();
[code].....
MSVC2010 throws out compiler error which says:
Code:
no operator found which takes a right-hand operand of type 'Derived *' (or there is no acceptable conversion)
What I don't understand is why? The pointer is an address of 0 element of an array. So what is the problem? I can eliminate the error by using double pointer but it will be an overkill.
Do you have to allocate memory(malloc) for an array of structs? Example:
Code:
typedef struct{
char * name;
}First;
struct name{
First fname;
};
struct name Names[10];
I'm making some multi-threaded program, but thats not my problem as i've done that already. I have a class with user-functions containing a structure which then contains a two dimensional array for each user with 25 elements. So I dont want to limit the user and make the array for example with just 10 rows, but allocate the needed memory to match the amount of 'users' a potential user of my program would want. The problem is, that i know how i should allocate it using 'new int' but it just doesnt work ! It gives an error:
Error: no operator "=" matches these operands
UserStuff.h:
struct userDataStruct {
bool* isAdmin;
[Code]...
Then, in some completely other class function inside the file mentioned above: (I know i could do a function in CUsers class which could allocate the memory, but I have this function which is used for some other things and it already has the amount of max users
void OtherClass::somefunction(maxusers)
{
// This gives an error: Error: no operator "=" matches these operands
curUsers->uData.userNumbers = new int*[maxusers]; //maxusers is the int variable of max users specified by the client
// However this doesn't
for( int i = 0 ; i < maxusers ; i++ )
curUsers->uData.userNumbers[i] = new int[25]; // 25 columns, this doesnt give any error
}
I'm not really sure what I'm doing wrong. Doing this in some function from CUsers class works (without curUsers-> or with, doesn't give any error) but doing it from some other class's function doesnt.
I want to be able to dynamically allocate and index an array like the following: vv2d[1][2].x and vv2d[1][2].y. In order to accomplish that I have chosen to use a std::vector of a std::vector of a 2D point class.
Code:
/// Here is my templated version of a 2d point class which I have adopted from
/// one by Alexander Chernosvitov, Function Graphics, 2001 (see ogview.h)
/// http://www.codeguru.com/cpp/g-m/opengl/article.php/c5581/Function-graphics-in-3D.htm
template <typename T>
[Code]....
Boundary violation occurs as soon as vv2d[1][0].x is encountered. I believe the problem is my inability to dynamically allocate the size of the (primary) typedef vector. However, eliminating the typedef for the following does not change the result. Further examination shows the vv2d[1][0] size and capacity to be 0.
Code:
vector<vector<CPoint2D<double>>> vv2d;
vv2d.resize(3);
vv2d[0].resize(3);
I have read that compiler allocates memory for an array.What does it exactly mean?For example,if compiler allocates memory at compilation-time,let's say it allocates memory address 189 for an array at compilation-time.But when I run the executable file and if that memory address(189) is not free,what happens?
View 6 Replies View RelatedI 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 have to allocate memory for an array of structures, and my structure looks as following:
Code:
typedef struct {
char *name;
Uint *start_pos;
Uint len;
}
example_struct;
And now I want to allocate memory, for a variable number (so an array) of example_struct, so I first do:
Code:
example struct *all_struct;
int total_num = 3;
//will be set somehow, but for the example I set it on 3 all_struct = malloc (sizeof(example_struct) * total_num);
And now, as far as I now, I will have to allocate for each field of the structure memory, in order to be able to use it later. But I have problem at this point, a problem of understanding:
- I just allocated memory for 3 structures, but don't I have to allocate then memory for each structure separately, or can I just now allocate the fields like this:
Code: all_struct[0].name = malloc.....
But if yes, why the hell this works...
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)
Code:
#include<fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/mman.h>
int main (int argc, char *argv[]){
[Code] ......
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 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.
I use the array of Radiobutton,string,.. in my project. How i can destruct these array from memory,because i see the stackoverflew exception.
View 1 Replies View RelatedWhat is wrong with my function why does it spit out huge numbers? And how do i use malloc or calloc to create an array in dynamic memory, and return a pointer to this array
Code:
#include <stdio.h>#include <stdlib.h>
int fibonacci(int n)
{
int i;
long int fib[40];
fib[0]=0;
fib[1]=1;
for(i=2;i<n;i++){
fib[i] = fib[i-1] + fib[i-2];
[Code]....
Suppose I wished to reallocate memory (resize) an array of pointers. Why does the following not work?(The program runs, yet yields a faulty segmentation error message. Why?):
Code: char **ptrarr = (char**) malloc(sizeof(char*))
Code: ptrarr = (char**) realloc(ptrarr, (capacity) * sizeof(char*));
When declaring char array[10], memory is allocated for 10 1-bit memory locations. Is extra memory allocated for storing the address of array[0]? In expressions, is array equivalent to a pointer constant or is it an identifier for a memory cell containing the address of array[0]? In other words, is array a variable or an alias for &array[0]?
View 6 Replies View RelatedI'm using C++ Form Application in Visual Studio 2010. I defined a new two dimentional array. like this "static int dizi[26][26];" I want to change the value when I clicked the button1. For example, I can change as dizi[2][3]=1. But I couldn't change like in this code. dizi[a][b]=1 didn't happen.
Error is... "access violation exception was unhandled. attempted to read or write protected memory. this is often an indication that other memory is corrupt."
for(int i=1;i<=26;i++){
uzunluk=0;
for(int uzun=1;uzun<=26;uzun++){
if(ogrenci[i].ders[uzun]!=0)
uzunluk+=1;
else break;
[Code] ....
I don't use zeroth variable here.So, It started from 1. My problem is variable can't be changed.I can't assign a value to variable. I have to use 'ogrenci[i].ders[j]'s index for dizi array in this code. It's really weird.
I have a contiguous sequence of section headers in a file (all the data in the file is stored in void * data), where each section header is the same size and has the same fields in the same order. So it's laid out like an array.
I have to:
- Use an offset value and the number of section headers variables to identify the location and length of the section header table (these are hdr.offset and hdr.length respectively).
- The offset value shows the distance between the start of the file and the start of the first section header (so I need a pointer to the start of the first section header)
- Apply a typecast to location of the section header table to process it as an array of section headers.
Here is what I have done, but I am getting a segmentation fault. What am I doing wrong? How do I fix this?
typedef struct {
unsigned int name;
unsigned int type;
} SectionHeader;
[Code] ....
When you have constant arrays, they are stored in the programme memory space. Upon execution, they are copied into the data space for easy access. To save space in the data space, it is possible to stop it from being copied. Some compilers will deal with this by just specifying the array as const, g++ has a type modifier called PROGMEM.
In any case, the problem is that I'd like to generate some data, preferably without using an external programme to do it. Hence, my question using the template system. Now I could possibly use macro metaprogramming via boost instead of template metaprogramming, and I may have to go that route. However there are limitations, especially since its numbering system is only equivalent to an unsigned byte, which I possibly could use, but could become more messy than if I use the template system that has long long types as well as a whole slue of type safety mechanisms.
