In one of my methods, a function with two parameters is passed, and saved as rightClick. However, because its in a static function, the compiler wants the function to be initialised before. How can i go about this?
Mouse.cpp
void Mouse::clicked(int button, int state, int x, int y)
{
if(button == GLUT_LEFT_BUTTON) {
if(state == GLUT_DOWN) {
isDragging = true;
CurrentX = x;
CurrentY = y;
}
else
{
isDragging = false;
}
}
else if (button == GLUT_RIGHT_BUTTON)
{
if (state == GLUT_DOWN)
{
isDragging = true;
rightClick(x,y);
}
}
}
void Mouse::setRightClickFunction(void (*func)(int, int))
{
rightClick = func;
}
The setRightClickFunction is called before click ever is. Except now i'm getting a different problem : "Mouse::rightClick", referenced from:
Mouse::clicked(int, int, int, int) in Mouse.o
Based on your comments, you're getting a linker error about "undefined reference to Mouse::rightClick. This has nothing to do with function pointers. It's just that whenever you declare a static data member in a class, it's only a declaration. You have to define it somewhere (= in exactly one .cpp file).
Assuming your class Mouse looks something like this:
class Mouse
{
//...
static void (*rightClick)(int, int);
//...
};
You should put this line somewhere into Mouse.cpp:
void (*Mouse::rightClick)(int, int) = 0;
That will serve as the definition of the static data member rightClick.
Related
So I have been working on an Arduino program that sends MIDI data over USB, and I can't seem to figure out how to pass the function that handles sending of midi data to my main class. It worked at some point but for some reason, it doesn't, and I feel like I have tried every combination of things.
Here is my main file, simplified down to just output the MIDI data over serial:
#include "XiaoPiezoDrum.h"
void sendNoteOn(int note, int velocity, int chan) {
Serial.printf("WORKS! %d %d %d\n", note, velocity, chan);
};
XiaoPiezoDrum drum(9, 2, 3, 4);
void setup() {
drum.setNoteComFunctions(sendNoteOn);
}
Here is what that setNoteComFunctions method looks like:
void XiaoPiezoDrum::setNoteComFunctions(const std::function<void(int, int, int)>& onFunc) {
sendNote = [onFunc](auto && PH1, auto && PH2, auto && PH3) { onFunc(PH1, PH2, PH3); };
}
And here is the relevant parts of the main class definition:
class XiaoPiezoDrum {
public:
XiaoPiezoDrum();
XiaoPiezoDrum(int piezoPin, int rPin, int gPin, int bPin);
void setNoteComFunctions(const function<void(int, int, int)>& onFunc);
void RunCycle();
private:
std::function<void(int, int, int)> sendNote;
}
So everything runs just fine until I call sendNote from within RunCycle, which is just called every loop, and then serial communication just stops suddenly. What am I doing wrong? I also tried using bind instead of a lambda, and the same thing happens. When I just copy the same print statement that is in sendNoteOn in the main file into the lambda in setNoteComFunctions, it prints just fine, so I know the issue is all about linking the function from the main file.
Things I have tried:
passing the function in setNoteComFunctions both as a reference and not
using bind rather than lambda
changing the body of sendNoteOn
making the lambda arguments references
making the lambda arguments not references
returning onFunc in the lambda
I have been banging my head against the keyboard for hours with this. If anybody knows what I'm doing wrong, I'd love an explanation!
EDIT
Here is the full code of RunCycle. Many of these variables are instance variables that I left out of the provided class definition, but I know the issue is with the call of sendNote, because if I comment it out, things continue running normally. I have also tried replacing the velocity variable with a fixed integer, and the same thing happened.
void XiaoPiezoDrum::RunCycle() {
double val = sensor.read();
val = (val > 0) ? val : 0;
Serial.println(val);
unsigned long timeElapsed;
int velocity;
MaxVal = (val > MaxVal) ? val : MaxVal;
trigger = val > THRESHOLD && !triggering;
if (val > THRESHOLD && !triggering) trigger = true;
if (trigger) {
triggerTime = millis();
trigger = false;
triggering = true;
triggerBuffer.clear();
}
if (triggering) {
timeElapsed = millis() - triggerTime;
if (timeElapsed < SAMPLE_TIME) {
loopCounter++;
triggerBuffer.addValue(val);
Serial.println(val);
}
else {
velocity = map(round(triggerBuffer.getMax()), 0, 300, THRESHOLD, 127);
Serial.printf("Velocity: %d\n", velocity);
if (comFunctionsSet) sendNote(40, velocity, 1);
noteEndTime = millis();
triggerTime = 0;
triggerBuffer.clear();
triggering = false;
resting = true;
}
}
}
jignatius' answer did it! I should have known I could do that!! Thanks!
I just had to replace
void XiaoPiezoDrum::setNoteComFunctions(const std::function<void(int, int, int)>& onFunc) {
sendNote = [onFunc](auto && PH1, auto && PH2, auto && PH3) { onFunc(PH1, PH2, PH3); };
}
with:
void XiaoPiezoDrum::setNoteComFunctions(const std::function<void(int, int, int)>& onFunc) {
sendNote = onFunc;
}
So glad to have that solved! Thanks!
I'm trying to extend the cefsimple app that comes with the Chromium Embedded Framework to include a V8 handler. The code I've written looks like this so far;
bool SimpleHandler::Execute(const CefString& name,
CefRefPtr<CefV8Value> object,
const CefV8ValueList& arguments,
CefRefPtr<CefV8Value>& retval,
CefString& exception) {
int argn = arguments.size();
if (name == "serial_connect" && (argn == 4 || argn == 1))
{
if (connection.isOpen())
connection.~Serial();
connection = NULL;
if (argn == 1)
{
int port = (arguments[0]); // convert to int?
}
else
{
}
}
else if (name == "serial_send" && argn >= 1)
{
}
else if (name == "serial_recieve")
{
}
else
return false;
return true;
}
I'm having trouble converting the generic value object returned given by the handler into a cpp int that I can use in calculations. I've found the function CefV8Value::GetIntValue();, but I can't figure out how to use it.
try calling object->GetIntValue()
The reason is that CefRefPtr is an object that holds a reference to CefV8Value, so you need the arrow operator to access the underlying CefV8Value object it points to
Sorry, but I have to repeat the same question as I asked before "C++, Adding conditions in class vars".
I am using SDL2 here.
In obj.h: (excluding preprocessor commands)
class obj {
public:
SDL_Rect clip;
void addCollideWith( SDL_Rect rect );
void hasCollide();
void clearCollideWith();
private:
std::list<bool *> collideWith;
};
In obj.cpp: (excluding preprocessor commands)
void obj::addCollideWith( SDL_Rect rect )
{
collideWith.push_back(SDL_HasIntersection(obj.clip, rect));
}
void obj::hasCollide()
{
bool retval = true;
for (std::list<bool *>::iterator it = collideWith.begin(); it != collideWith.end(); it++)
{
retval = retval && **it;
}
return retval;
}
void clearCollideWith()
{
collideWith.clear();
}
Inside main function, I am saying that the object moves by one pixel and every time when it moves by one pixel, it checks for collision with other objects. I cleared the pointer thing '*' as I am not putting in variables as you can see: collideWith.push_back(SDL_HasIntersection(obj.clip, rect));. What I do is to make it move a pixel, clear collideWith and add collideWith condition again for updating whether it is true or false.
Now, whats the problem?
Its making the program really really slow! If I remove collideWith thing and then, starts the program, it gets a lot more smoother. Now, what I want, is to store the statement rather than true or false. std::list takes:
collideWith.pushBack(true /*OR*/ false);
But what I want is:
collideWith.pushBack(/*statement determining whether it is true or false*/ var1 > var2);
Please do complain if context is missing or the question is somehow, not understandable!
(NOTE: Context related to moving the object and declaring obj clip sub-vars is not mentioned as they are not a part of question.)
You could try to replace
std::list<bool *> collideWith;
with
std::list<SDL_Rect> collideWith;
in order to track of the rectangles that you want to considere.
The implementation could be :
void obj::addCollideWith( SDL_Rect rect )
{
collideWith.push_back(rect);
}
// to test if it collides with at least one rectangle
bool obj::hasCollide()
{
bool retval = false;
for (std::list<SDL_Rect>::iterator it = collideWith.begin(); it != collideWith.end(); it++)
{
retval = retval || SDL_HasIntersection(obj.clip, *it);
}
return retval;
}
// to test if it collides with all rectangles
/* bool obj::hasCollide()
{
bool retval = true;
for (std::list<SDL_Rect>::iterator it = collideWith.begin(); it != collideWith.end(); it++)
{
retval = retval && SDL_HasIntersection(obj.clip, *it);
}
return retval;
} */
How can I find the current depth inside a recursive function in C++ without passing in the previous level? i.e. is it possible to know how many times the function was called without using a parameter to keep track of the level and passing that number in as a parameter each time the function is called?
For example my recursive function looks like this:
DoSomething(int level)
{
print level;
if (level > 10)
return;
DoSomething(++level);
}
main
{
DoSomething(0);
}
Building on the answer already given by JoshD:
void recursive()
{
static int calls = 0;
static int max_calls = 0;
calls++;
if (calls > max_calls)
max_calls = calls;
recursive();
calls--;
}
This resets the counter after the recursive function is complete, but still tracks the maximum depth of the recursion.
I wouldn't use static variables like this for anything but a quick test, to be deleted soon after. If you really need to track this on an ongoing basis there are better methods.
You could use a static variable in the function...
void recursive()
{
static int calls = 0;
calls++;
recursive();
}
Of course, this will keep counting when you start a new originating call....
If you want it to be re-entrant and thread-safe, why not:
void rec(int &level) // reference to your level var
{
// do work
rec(++level); // go down one level
}
main()
{
//and you call it like
int level=0;
rec(level);
cout<<level<<" levels."<<endl;
}
No static/global variables to mess up threading and you can use different variables for different recursive chains for re-entrancy issues.
You can use a local static variable, if you don't care about thread-safety.
Although, this will only give you a proper count the first time you run your recursive routine. A better technique would be a RAII guard-type class which contains an internal static variable. At the start of the recursive routine, construct the guard class. The constructor would increment the internal static variable, and the destructor would decrement it. This way, when you create a new stack-frame the counter increments by one, and when you return from each stack-frame the counter would decrement by one.
struct recursion_guard
{
recursion_guard() { ++counter; }
~recursion_guard() { --counter; }
static int counter;
};
int recursion_guard::counter = 0;
void recurse(int x)
{
recursion_guard rg;
if (x > 10) return;
recurse(x + 1);
}
int main()
{
recurse(0);
recurse(0);
}
Note however, that this is still not thread-safe. If you need thread-safety, you can replace the static-storage variable with a thread-local-storage variable, either using boost::thread_specific_ptr or the C++0x thread local facilities.
You could also pass in the level as a template parameter, if it can be determined at compile-time. You could also use a function object. This is by far and away the best option - less hassle, and static variables should be avoided wherever possible.
struct DoSomething {
DoSomething() {
calls = 0;
}
void operator()() {
std::cout << calls;
calls++;
if (calls < 10)
return operator()();
return;
}
int calls;
};
int main() {
DoSomething()(); // note the double ().
std::cin.get();
}
convert level to an instance variable of a new object (typically a template) capable of containing the arguments and (possibly) the function. then you can reuse the recursion accumulator interface.
You can also try using a global variable to log the depth.
var depth = 0;
DoSomething()
{
print ++depth;
if (depth > 10)
return;
DoSomething();
}
main
{
DoSomething(0);
}
I came here when I sensed that some recursion is required, because I was implementing a function that can validate the chain of trust in a certificate chain. This is not X.509 but instead it is just the basics wherein the issuer key of a certificate must match the public key of the signer.
bool verify_chain(std::vector<Cert>& chain,
Cert* certificate,
unsigned char* pOrigin = nullptr, int depth = 0)
{
bool flag = false;
if (certificate == nullptr) {
// use first element in case parameter is null
certificate = &chain[0];
}
if (pOrigin == nullptr) {
pOrigin = certificate->pubkey;
} else {
if (std::memcmp(pOrigin, certificate->pubkey, 32) == 0) {
return false; // detected circular chain
}
}
if (certificate->hasValidSignature()) {
if (!certificate->isRootCA()) {
Cert* issuerCert = certificate->getIssuer(chain);
if (issuerCert) {
flag = verify_chain(chain, issuerCert, pOrigin, depth+1);
}
} else {
flag = true;
}
}
if (pOrigin && depth == 1) {
pOrigin = nullptr;
}
return flag;
}
I needed to know the recursion depth so that I can correctly clean up pOrigin. at the right stack frame during the unwinding of the call stack.
I used pOrigin to detect a circular chain, without which the recursive call can go on forever. For example,
cert0 signs cert1
cert1 signs cert2
cert2 signs cert0
I later realized that a simple for-loop can do it for simple cases when there is only one common chain.
bool verify_chain2(std::vector<Cert> &chain, Cert& cert)
{
Cert *pCert = &cert;
unsigned char *startkey = cert.pubkey;
while (pCert != nullptr) {
if (pCert->hasValidSignature()) {
if (!pCert->isRootCA()) {
pCert = pCert->getIssuer(chain);
if (pCert == nullptr
|| std::memcmp(pCert->pubkey, startkey, 32) == 0) {
return false;
}
continue;
} else {
return true;
}
} else {
return false;
}
}
return false;
}
But recursion is a must when there is not one common chain but instead the chain is within each certificate. I welcome any comments. Thank you.
I have a few classes set up for a game, with XMapObject as the base, and XEntity, XEnviron, and XItem inheriting it.
MapObjects have a number of flags, one of them being MAPOBJECT_SOLID. My problem is that XEntity is the only class that correctly detects MAPOBJECT_SOLID. Both Items are Environs are always considered solid by the game, regardless of the flag's state. What is important is that Environs and Item should almost never be solid.
Each class has a very basic preliminary constructor, just initializing all varibles to zero or NULL. During the CreateX() phase, Objects are linked into the map, set into a linked linked list.
Both XItem and XEnviron are a tad sloppy. They are both new, and in the middle or my debugging attempts.
Here are the relevent code samples:
XMapObject:
#define MAPOBJECT_ACTIVE 1
#define MAPOBJECT_RENDER 2
#define MAPOBJECT_SOLID 4
class XMapObject : public XObject
{
public:
Uint8 MapObjectType,Location[2],MapObjectFlags;
XMapObject *NextMapObject,*PrevMapObject;
XMapObject();
void CreateMapObject(Uint8 MapObjectType);
void SpawnMapObject(Uint8 MapObjectLocation[2]);
void RemoveMapObject();
void DeleteMapObject();
void MapObjectSetLocation(Uint8 Y,Uint8 X);
void MapObjectMapLink();
void MapObjectMapUnlink();
};
XMapObject::XMapObject()
{
MapObjectType = 0;
Location[0] = 0;
Location[1] = 1;
NextMapObject = NULL;
PrevMapObject = NULL;
}
void XMapObject::CreateMapObject(Uint8 Type)
{
MapObjectType = Type;
}
void XMapObject::SpawnMapObject(Uint8 MapObjectLocation[2])
{
if(!(MapObjectFlags & MAPOBJECT_ACTIVE)) { MapObjectFlags += MAPOBJECT_ACTIVE; }
Location[0] = MapObjectLocation[0];
Location[1] = MapObjectLocation[1];
MapObjectMapLink();
}
XEntity:
XEntity *StartEntity = NULL,*EndEntity = NULL;
class XEntity : public XMapObject
{
public:
Uint8 Health,EntityFlags;
float Speed,Time;
XEntity *NextEntity,*PrevEntity;
XItem *IventoryList;
XEntity();
void CreateEntity(Uint8 EntityType,Uint8 EntityLocation[2]);
void DeleteEntity();
void EntityLink();
void EntityUnlink();
Uint8 MoveEntity(Uint8 YOffset,Uint8 XOffset);
};
XEntity::XEntity()
{
Health = 0;
Speed = 0;
Time = 1.0;
EntityFlags = 0;
NextEntity = NULL;
PrevEntity = NULL;
IventoryList = NULL;
}
void XEntity::CreateEntity(Uint8 EntityType,Uint8 EntityLocation[2])
{
CreateMapObject(EntityType);
SpawnMapObject(EntityLocation);
if(!(MapObjectFlags & MAPOBJECT_SOLID) { MapObjectFlags += MAPOBJECT_SOLID; }
EntityFlags = ENTITY_CLIPPING;
Time = 1.0;
Speed = 1.0;
EntityLink();
}
void XEntity::EntityLink()
{
if(StartEntity == NULL)
{
StartEntity = this;
PrevEntity = NULL;
NextEntity = NULL;
}
else
{
EndEntity->NextEntity = this;
}
EndEntity = this;
}
XEnviron:
class XEnviron : public XMapObject
{
public:
Uint8 Effect,TimeOut;
void CreateEnviron(Uint8 Type,Uint8 Y,Uint8 X,Uint8 TimeOut);
};
void XEnviron::CreateEnviron(Uint8 EnvironType,Uint8 Y,Uint8 X,Uint8 TimeOut)
{
CreateMapObject(EnvironType);
Location[0] = Y;
Location[1] = X;
SpawnMapObject(Location);
XTile *Tile = GetTile(Y,X);
Tile->Environ = this;
MapObjectFlags = MAPOBJECT_ACTIVE + MAPOBJECT_SOLID;
printf("%i\n",MapObjectFlags);
}
XItem:
class XItem : public XMapObject
{
public:
void CreateItem(Uint8 Type,Uint8 Y,Uint8 X);
};
void XItem::CreateItem(Uint8 Type,Uint8 Y,Uint8 X)
{
CreateMapObject(Type);
Location[0] = Y;
Location[1] = X;
SpawnMapObject(Location);
}
And lastly, the entity move code. Only entities are capable of moving themselves.
Uint8 XEntity::MoveEntity(Uint8 YOffset,Uint8 XOffset)
{
Uint8
NewY = Location[0] + YOffset,
NewX = Location[1] + XOffset;
if((NewY >= 0 && NewY < MAPY) && (NewX >= 0 && NewX < MAPX))
{
XTile *Tile = GetTile(NewY,NewX);
if(Tile->MapList != NULL)
{
XMapObject *MapObject = Tile->MapList;
while(MapObject != NULL)
{
if(MapObject->MapObjectFlags & MAPOBJECT_SOLID)
{
printf("solid\n");
return 0;
}
MapObject = MapObject->NextMapObject;
}
}
if(Tile->Flags & TILE_SOLID && EntityFlags & ENTITY_CLIPPING)
{
return 0;
}
this->MapObjectSetLocation(NewY,NewX);
return 1;
}
return 0;
}
What is wierd, is that the bitwise operator always returns true when the MapObject is an Environ or an Item, but it works correctly for Entities. For debug I am using the printf "Solid", and also a printf containing the value of the flag for both Environs and Items.
Any help is greatly appreciated, as this is a major bug for the small game I am working on. I am also very new at Object Oriented programming, anything tips, suggestions and/or criticism are also welcome.
Your problem appears to be that you never initialize MapObjectFlags in any classes other than XEnviron so, as a basic type, it will have an unspecified value in XItem, XEntity and other XMapObject derived objects. I suggest that, as a member of XMapObject you explicitly initialize it to a known value.
As a rule, it is generally a good idea to ensure that all members of basic type are explicitly initialized in the initializer list of every constructor that you define.
e.g.
XMapObject()
: MapObjectFlags(0)
, // ... other initializers
{
// Other initializations
}
You can't (legally) be calling XEntity::MoveEntity on a MapObject or Environ because they don't have such a method. If you're using static_cast to change your object pointer into an XEntity so you can call MoveEntity on it, then you really have no guarantees about how the bit operation will work. In some implementations, things may appear to work in MoveEntity, but what's actually happening is it's interpreting the other object's memory as an XEntity. When it tries to access the offset where it believes MapObjectFlags exists, it's not actually there and always has that bit set to 1.
I figured out the problem earlier today - It didn't have any relation to OO programming, inheritance, or bitwise; it was a simple scope error.
The problem was in the fact that during my quick test to get an Environ in game, I declared the new variable inside of the control switch sequence, so the next time any control was used, the Environ would act in unpredictable ways.
switch(Event.key.keysym.sym)
{
...
case SDLK_c: { XEnviron Environ; Environ.InitEnviron(...); }
...
}