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• Keyboard input system handling

  - by The Communist Duck

  Note: I have to poll, rather than do callbacks because of API limitations (SFML). I also apologize for the lack of a 'decent' title. I think I have two questions here; how to register the input I'm receiving, and what to do with it. Handling Input I'm talking about after the fact you've registered that the 'A' key has been pressed, for example, and how to do it from there. I've seen an array of the whole keyboard, something like: bool keyboard[256]; //And each input loop check the state of every key on the keyboard But this seems inefficient. Not only are you coupling the key 'A' to 'player moving left', for example, but it checks every key, 30-60 times a second. I then tried another system which just looked for keys it wanted. std::map< unsigned char, Key keyMap; //Key stores the keycode, and whether it's been pressed. Then, I declare a load of const unsigned char called 'Quit' or 'PlayerLeft'. input-BindKey(Keys::PlayerLeft, KeyCode::A); //so now you can check if PlayerLeft, rather than if A. However, the problem with this is I cannot now type a name, for example, without having to bind every single key. Then, I have the second problem, which I cannot really think of a good solution for: Sending Input I now know that the A key has been pressed or that playerLeft is true. But how do I go from here? I thought about just checking if(input-IsKeyDown(Key::PlayerLeft) { player.MoveLeft(); } This couples the input greatly to the entities, and I find it rather messy. I'd prefer the player to handle its own movement when it gets updated. I thought some kind of event system could work, but I do not know how to go with it. (I heard signals and slots was good for this kind of work, but it's apparently very slow and I cannot see how it'd fit). Thanks.

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• Correct For Loop Design

  - by Yttrill

  What is the correct design for a for loop? Felix currently uses if len a > 0 do for var i in 0 upto len a - 1 do println a.[i]; done done which is inclusive of the upper bound. This is necessary to support the full range of values of a typical integer type. However the for loop shown does not support zero length arrays, hence the special test, nor will the subtraction of 1 work convincingly if the length of the array is equal to the number of integers. (I say convincingly because it may be that 0 - 1 = maxval: this is true in C for unsigned int, but are you sure it is true for unsigned char without thinking carefully about integral promotions?) The actual implementation of the for loop by my compiler does correctly handle 0 but this requires two tests to implement the loop: continue: if not (i <= bound) goto break body if i == bound goto break ++i goto continue break: Throw in the hand coded zero check in the array example and three tests are needed. If the loop were exclusive it would handle zero properly, avoiding the special test, but there'd be no way to express the upper bound of an array with maximum size. Note the C way of doing this: for(i=0; predicate(i); increment(i)) has the same problem. The predicate is tested after the increment, but the terminating increment is not universally valid! There is a general argument that a simple exclusive loop is enough: promote the index to a large type to prevent overflow, and assume no one will ever loop to the maximum value of this type.. but I'm not entirely convinced: if you promoted to C's size_t and looped from the second largest value to the largest you'd get an infinite loop!

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• Oracle JDK 7u10 released with new security features

  - by Henrik Stahl

  A few days ago, we released JRE and JDK 7 update 10. This release adds support for the following new platforms: Windows 8 on x86-64. Note that Modern UI (aka Metro) mode is not supported. Internet Explorer 10 on Windows 8. Mac OS X 10.8 (Mountain Lion) This release also introduces new features that provide enhanced security for Java applet and webstart applications, specifically: The Java runtime tracks if it is updated to the latest security baseline. If you try to execute an unsigned applet with an outdated version of Java, a warning dialog will prompt you to update before running the applet. The Java runtime includes a hardcoded best before date. It is assumed that a new version will be released before this date. If the client has not been able to check for an update prior to this date, the Java runtime will assume that it is insecure and start warning the user prior to executing any applets. The Java control panel now includes an option to set the desired security level on a low-medium-high-very high scale, as well as an option to disable Java applets and webstart entirely. This level controls things such as if the Java runtime is allowed to execute unsigned code, and if so what type of warning will be displayed to the user. More details on the security settings can be found in the documentation. See below for a sample screenshot. The new update of the JRE and the JDK are available via OTN. To learn more about the release please visit the release notes.

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• XNA texture stretching at extreme coordinates

  - by Shaun Hamman

  I was toying around with infinitely scrolling 2D textures using the XNA framework and came across a rather strange observation. Using the basic draw code: spriteBatch.Begin(SpriteSortMode.Deferred, null, SamplerState.PointWrap, null, null); spriteBatch.Draw(texture, Vector2.Zero, sourceRect, Color.White, 0.0f, Vector2.Zero, 2.0f, SpriteEffects.None, 1.0f); spriteBatch.End(); with a small 32x32 texture and a sourceRect defined as: sourceRect = new Rectangle(0, 0, Window.ClientBounds.Width, Window.ClientBounds.Height); I was able to scroll the texture across the window infinitely by changing the X and Y coordinates of the sourceRect. Playing with different coordinate locations, I noticed that if I made either of the coordinates too large, the texture no longer drew and was instead replaced by either a flat color or alternating bands of color. Tracing the coordinates back down, I found the following at around (0, -16,777,000): As you can see, the texture in the top half of the image is stretched vertically. My question is why is this occurring? Certainly I can do things like bind the x/y position to some low multiple of 32 to give the same effect without this occurring, so fixing it isn't an issue, but I'm curious about why this happens. My initial thought was perhaps it was overflowing the coordinate value or some such thing, but looking at a data type size chart, the next closest below is an unsigned short with a range of about 32,000, and above is an unsigned int with a range of around 2,000,000,000 so that isn't likely the cause.

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• Understanding how memory contents map into a struct

  - by user95592

  I am not able to understand how bytes in memory are being mapped into a struct. My machine is a little-endian x86_64. The code was compiled with gcc 4.7.0 from the Win64 mingw32-64 distribution for Win64. These are contents of the relevant memory fragment: ...450002cf9fe5000040115a9fc0a8fe... And this is the struct definition: typedef struct ip4 { unsigned int ihl :4; unsigned int version :4; uint8_t tos; uint16_t tot_len; uint16_t id; uint16_t frag_off; // flags=3 bits, offset=13 bits uint8_t ttl; uint8_t protocol; uint16_t check; uint32_t saddr; uint32_t daddr; /*The options start here. */ } ip4_t; When a pointer to such an structure (let it be *ip4) is initialized to the starting address of the above pasted memory region, this is what the debugger shows for the struct's fields: ip4: address=0x8da36ce ip4->ihl: address=0x8da36ce, value=0x5 ip4->version: address=0x8da36ce, value=0x4 ip4->tos: address=0x8da36d2, value=0x9f ip4->tot_len: address=0x8da36d4, value=0x0 ... I see how ihl and version are mapped: 4 bytes for a long integer, little-endian. But I don't understand how tos and tot_len are mapped; which bytes in memory correspond to each one of them. Thank you in advance.

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• Learning OpenGL GLSL - VAO buffer problems?

  - by Bleary

  I've just started digging through OpenGL and GLSL, and now stumbled on something I can't get my head around this one!? I've stepped back to loading a simple cube and using a simple shader on it, but the result is triangles drawn incorrectly and/or missing. The code I had working perfectly on meshes, but was attempting to move to using VAOs so none of the code for storing the vertices and indices has changed. http://i.stack.imgur.com/RxxZ5.jpg http://i.stack.imgur.com/zSU50.jpg What I have for creating the VAO and buffers is this //Create the Vertex array object glGenVertexArrays(1, &vaoID); // Finally create our vertex buffer objects glGenBuffers(VBO_COUNT, mVBONames); glBindVertexArray(vaoID); // Save vertex attributes into GPU glBindBuffer(GL_ARRAY_BUFFER, mVBONames[VERTEX_VBO]); // Copy data into the buffer object glBufferData(GL_ARRAY_BUFFER, lPolygonVertexCount*VERTEX_STRIDE*sizeof(GLfloat), lVertices, GL_STATIC_DRAW); glEnableVertexAttribArray(pos); glVertexAttribPointer(pos, 3, GL_FLOAT, GL_FALSE, VERTEX_STRIDE*sizeof(GLfloat),0); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mVBONames[INDEX_VBO]); glBufferData(GL_ELEMENT_ARRAY_BUFFER, lPolygonCount*sizeof(unsigned int), lIndices, GL_STATIC_DRAW); glBindVertexArray(0); And the code for drawing the mesh. glBindVertexArray(vaoID); glUseProgram(shader->programID); GLsizei lOffset = mSubMeshes[pMaterialIndex]->IndexOffset*sizeof(unsigned int); const GLsizei lElementCount = mSubMeshes[pMaterialIndex]->TriangleCount*TRIAGNLE_VERTEX_COUNT; glDrawElements(GL_TRIANGLES, lElementCount, GL_UNSIGNED_SHORT, reinterpret_cast<const GLvoid*>(lOffset)); // All the points are indeed in the correct place!? //glPointSize(10.0f); //glDrawElements(GL_POINTS, lElementCount, GL_UNSIGNED_SHORT, 0); glUseProgram(0); glBindVertexArray(0); Eyes have become bleary looking at this today so any thoughts or a fresh set of eyes would be greatly appreciated.

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• How to alter image pixels of a wild life bird?

  - by NoobScratcher

  Hello so I was hoping someone knew how to move or change color and position actual image pixels and could explain and show the code to do so. I know how to write pixels on a surface or screen-surface usigned int *ptr = static_cast <unsigned int *> (screen-pixels); int offset = y * (screen->pitch / sizeof(unsigned int)); ptr[offset + x] = color; But I don't know how to alter or manipulate a image pixel of a png image my thoughts on this was How do I get the values and locations of pixels and what do I have to write to make it happen? Then how do I actually change the values or locations of those gotten pixels and how do I make that happen? any ideas tip suggestions are also welcome! int main(int argc , char *argv[]) { SDL_Surface *Screen = SDL_SetVideoMode(640,480,32,SDL_SWSURFACE); SDL_Surface *Image; Image = IMG_Load("image.png"); bool done = false; SDL_Event event; while(!done) { SDL_FillRect(Screen,NULL,(0,0,0)); SDL_BlitSurface(Image,NULL,Screen,NULL); while(SDL_PollEvent(&event)) { switch(event.type) { case SDL_QUIT: return 0; break; } } SDL_Flip(Screen); } return 0; }

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• OpenGL - Rendering from part of an index and vertex array depending on an element count

  - by user1423893

  I'm currently drawing my shapes as lines by using a VAO and then assigning the dynamic vertices and indices each frame. // Bind VAO glBindVertexArray(m_vao); // Update the vertex buffer with the new data (Copy data into the vertex buffer object) glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(VertexPosition), m_vertices.data(), GL_DYNAMIC_DRAW); // Update the index buffer with the new data (Copy data into the index buffer object) glBufferData(GL_ELEMENT_ARRAY_BUFFER, numIndices * sizeof(unsigned short), indices.data(), GL_DYNAMIC_DRAW); glDrawElements(GL_LINES, numIndices, GL_UNSIGNED_SHORT, BUFFER_OFFSET(0)); // Unbind VAO glBindVertexArray(0); What I would like to do is draw the lines using only part of the data stored in the index and vertex buffer objects. The vertex buffer has its vertices set from an array of defined maximum size: std::array<VertexPosition, maxVertices> m_vertices; The index buffer has its elements set from an array of defined maximum size: std::array<unsigned short, maxIndices> indices = { 0 }; A running total is kept of the number of vertices and indices needed for each draw call numVertices numIndices Can I not specify that the buffer data contain the entire array and only read from part of it when drawing? For example using the vertex buffer object glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(VertexPosition), m_vertices.data(), GL_DYNAMIC_DRAW); m_vertices.data() = Entire array is stored numVertices * sizeof(VertexPosition) = Amount of data to read from the entire array Is this not the correct way to approach this? I do not wish to use std::vector if possible.

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• How do you make a precise countdown timer using clock_gettime? [migrated]

  - by Joshun

  Could somebody please explain how to make a countdown timer using clock_gettime, under Linux. I know you can use the clock() function to get cpu time, and multiply it by CLOCKS_PER_SEC to get actual time, but I'm told the clock() function is not well suited for this. So far I have attempted this (a billion is to pause for one second) #include <stdio.h> #include <time.h> #define BILLION 1000000000 int main() { struct timespec rawtime; clock_gettime(CLOCK_MONOTONIC_RAW, &rawtime); unsigned long int current = ( rawtime.tv_sec + rawtime.tv_nsec ); unsigned long int end = (( rawtime.tv_sec + rawtime.tv_nsec ) + BILLION ); while ( current < end ) { clock_gettime(CLOCK_MONOTONIC_RAW, &rawtime); current = ( rawtime.tv_sec + rawtime.tv_nsec ); } return 0; } I know this wouldn't be very useful on its own, but once I've found out how to time correctly I can use this in my projects. I know that sleep() can be used for this purpose, but I want to code the timer myself so that I can better integrate it in my projects - such as the possibility of it returning the time left, as opposed to pausing the whole program.

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• Hi, I have a C hashing routine which is behaving strangely?

  - by aks

  Hi, In this hashing routine: 1.) I am able to add strings. 2.) I am able to view my added strings. 3.) When i try to add a duplicate string, it throws me an error saying already present. 4.) But, when i try to delete the same string which is already present in hash table, then the lookup_routine calls hash function to get an index. At this time, it throws a different hash index to the one it was already added. Hence, my delete routine is failing? I am able to understand the reason why for same string, hash fucntion calculates a different index each time (whereas the same logic works in view hash table routine)? Can someone help me? This is the Output, i am getting: $ ./a Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 1 Please enter the string :gaura enters in add_string DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 1 hashval = 1 enters in lookup_string str in lookup_string = gaura DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 1 hashval = 1 DEBUG ERROR :element not found in lookup string DEBUG Purpose NULL Inserting... DEBUG1 : enters here hashval = 1 String added successfully Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 1 Please enter the string :ayu enters in add_string DEBUG purpose in hash function: str passed = ayu Hashval returned in hash func= 1 hashval = 1 enters in lookup_string str in lookup_string = ayu DEBUG purpose in hash function: str passed = ayu Hashval returned in hash func= 1 hashval = 1 returns NULL in lookup_string DEBUG Purpose NULL Inserting... DEBUG2 : enters here hashval = 1 String added successfully Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 1 Please enter the string :gaurava enters in add_string DEBUG purpose in hash function: str passed = gaurava Hashval returned in hash func= 7 hashval = 7 enters in lookup_string str in lookup_string = gaurava DEBUG purpose in hash function: str passed = gaurava Hashval returned in hash func= 7 hashval = 7 DEBUG ERROR :element not found in lookup string DEBUG Purpose NULL Inserting... DEBUG1 : enters here hashval = 7 String added successfully Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 4 Index : i = 1 String = gaura ayu Index : i = 7 String = gaurava Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 2 Please enter the string you want to delete :gaura String entered = gaura enters in delete_string DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 0 hashval = 0 enters in lookup_string str in lookup_string = gaura DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 0 hashval = 0 DEBUG ERROR :element not found in lookup string DEBUG Purpose Item not present. So, cannot be deleted Item found in list: Deletion failed Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: My routine is pasted below: include include struct list { char *string; struct list *next; }; struct hash_table { int size; /* the size of the table */ struct list *table; / the table elements */ }; struct hash_table * hashtable = NULL; struct hash_table *create_hash_table(int size) { struct hash_table *new_table; int i; if (size<1) return NULL; /* invalid size for table */ /* Attempt to allocate memory for the table structure */ if ((new_table = malloc(sizeof(struct hash_table))) == NULL) { return NULL; } /* Attempt to allocate memory for the table itself */ if ((new_table->table = malloc(sizeof(struct list *) * size)) == NULL) { return NULL; } /* Initialize the elements of the table */ for(i=0; i<size; i++) new_table->table[i] = '\0'; /* Set the table's size */ new_table->size = size; return new_table; } unsigned int hash(struct hash_table *hashtable, char *str) { printf("\n DEBUG purpose in hash function:\n"); printf("\n str passed = %s", str); unsigned int hashval = 0; int i = 0; for(; *str != '\0'; str++) { hashval += str[i]; i++; } hashval = hashval % 10; printf("\n Hashval returned in hash func= %d", hashval); return hashval; } struct list *lookup_string(struct hash_table *hashtable, char *str) { printf("\n enters in lookup_string \n"); printf("\n str in lookup_string = %s",str); struct list * new_list; unsigned int hashval = hash(hashtable, str); printf("\n hashval = %d \n", hashval); if(hashtable->table[hashval] == NULL) { printf("\n DEBUG ERROR :element not found in lookup string \n"); return NULL; } /* Go to the correct list based on the hash value and see if str is * in the list. If it is, return return a pointer to the list element. * If it isn't, the item isn't in the table, so return NULL. */ for(new_list = hashtable->table[hashval]; new_list != NULL;new_list = new_list->next) { if (strcmp(str, new_list->string) == 0) return new_list; } printf("\n returns NULL in lookup_string \n"); return NULL; } int add_string(struct hash_table *hashtable, char *str) { printf("\n enters in add_string \n"); struct list *new_list; struct list *current_list; unsigned int hashval = hash(hashtable, str); printf("\n hashval = %d", hashval); /* Attempt to allocate memory for list */ if ((new_list = malloc(sizeof(struct list))) == NULL) { printf("\n enters here \n"); return 1; } /* Does item already exist? */ current_list = lookup_string(hashtable, str); if (current_list == NULL) { printf("\n DEBUG Purpose \n"); printf("\n NULL \n"); } /* item already exists, don't insert it again. */ if (current_list != NULL) { printf("\n Item already present...\n"); return 2; } /* Insert into list */ printf("\n Inserting...\n"); new_list->string = strdup(str); new_list->next = NULL; //new_list->next = hashtable->table[hashval]; if(hashtable->table[hashval] == NULL) { printf("\n DEBUG1 : enters here \n"); printf("\n hashval = %d", hashval); hashtable->table[hashval] = new_list; } else { printf("\n DEBUG2 : enters here \n"); printf("\n hashval = %d", hashval); struct list * temp_list = hashtable->table[hashval]; while(temp_list->next!=NULL) temp_list = temp_list->next; temp_list->next = new_list; // hashtable->table[hashval] = new_list; } return 0; } int delete_string(struct hash_table *hashtable, char *str) { printf("\n enters in delete_string \n"); struct list *new_list; struct list *current_list; unsigned int hashval = hash(hashtable, str); printf("\n hashval = %d", hashval); /* Does item already exist? */ current_list = lookup_string(hashtable, str); if (current_list == NULL) { printf("\n DEBUG Purpose \n"); printf("\n Item not present. So, cannot be deleted \n"); return 1; } /* item exists, delete it. */ if (current_list != NULL) { struct list * temp = hashtable->table[hashval]; if(strcmp(temp->string,str) == 0) { if(temp->next == NULL) { hashtable->table[hashval] = NULL; free(temp); } else { hashtable->table[hashval] = temp->next; free(temp); } } else { struct list * temp1; while(temp->next != NULL) { temp1 = temp; if(strcmp(temp->string, str) == 0) { break; } else { temp = temp->next; } } if(temp->next == NULL) { temp1->next = NULL; free(temp); } else { temp1->next = temp->next; free(temp); } } } return 0; } void free_table(struct hash_table *hashtable) { int i; struct list *new_list, *temp_list; if (hashtable==NULL) return; /* Free the memory for every item in the table, including the * strings themselves. */ for(i=0; i<hashtable->size; i++) { new_list = hashtable->table[i]; while(new_list!=NULL) { temp_list = new_list; new_list = new_list->next; free(temp_list->string); free(temp_list); } } /* Free the table itself */ free(hashtable->table); free(hashtable); } void view_hashtable(struct hash_table * hashtable) { int i = 0; if(hashtable == NULL) return; for(i =0; i < hashtable->size; i++) { if((hashtable->table[i] == 0) || (strcmp(hashtable->table[i]->string, "*") == 0)) { continue; } printf(" Index : i = %d\t String = %s",i, hashtable->table[i]->string); struct list * temp = hashtable->table[i]->next; while(temp != NULL) { printf("\t %s",temp->string); temp = temp->next; } printf("\n"); } } int main() { hashtable = create_hash_table(10); if(hashtable == NULL) { printf("\n Memory allocation failure during creation of hash table \n"); return 0; } int flag = 1; while(flag) { int choice; printf("\n Press 1 to add an element to the hashtable\n"); printf("\n Press 2 to delete an element from the hashtable\n"); printf("\n Press 3 to search the hashtable\n"); printf("\n Press 4 to view the hashtable\n"); printf("\n Press 5 to exit \n"); printf("\n Please enter your choice: "); scanf("%d",&choice); if(choice == 5) flag = 0; else if(choice == 1) { char str[20]; printf("\n Please enter the string :"); scanf("%s",&str); int i; i = add_string(hashtable,str); if(i == 1) { printf("\n Memory allocation failure:Choice 1 \n"); return 0; } else if(i == 2) { printf("\n String already prsent in hash table : Couldnot add it again\n"); return 0; } else { printf("\n String added successfully \n"); } } else if(choice == 2) { int i; struct list * temp_list; char str[20]; printf("\n Please enter the string you want to delete :"); scanf("%s",&str); printf("\n String entered = %s", str); i = delete_string(hashtable,str); if(i == 0) { printf("\n Item found in list: Deletion success \n"); } else printf("\n Item found in list: Deletion failed \n"); } else if(choice == 3) { struct list * temp_list; char str[20]; printf("\n Please enter the string :"); scanf("%s",&str); temp_list = lookup_string(hashtable,str); if(!temp_list) { printf("\n Item not found in list: Deletion failed \n"); return 0; } printf("\n Item found: Present in Hash Table \n"); } else if(choice == 4) { view_hashtable(hashtable); } else if(choice == 5) { printf("\n Exiting ...."); return 0; } else printf("\n Invalid choice:"); }; free_table(hashtable); return 0; }

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• calculater by using reverse polish notation and using a stack

  - by programmer

  hello everyone I have a segmentation fault ,can you help please? if i have this operater "3 5 +" that mean 3+5 and like "9 8 * 5 + 4 + sin", "sin(((9*8)+5)+4)" so my idea is check if the first and second are numbers and push theem in the stack then when i have operator i pop the numbers and make the calculation then push the answer again. ` typedef struct st_node { float val; struct st_node *next; } t_node; typedef t_node t_stack; // a function to allocate memory for a stack and returns the stack t_stack* fnewCell() { t_stack* ret; ret = (t_stack*) malloc(sizeof(t_stack)); return ret; } // a function to allocate memory for a stack, fills it with value v and pointer n , and returns the stack t_stack* fnewCellFilled(float v, t_stack* n) { t_stack* ret; ret = fnewCell(); ret->val = v; ret->next =n; return ret; } //function to initialize stack void initstack(t_stack** stack) { fnewCellFilled(0,NULL); } // add new cell void insrtHead(t_stack** head,float val) { *head = fnewCellFilled(val,*head); } //function to push the value v into the stack s void push(t_stack **s, float val) { insrtHead(s,val); } //function to pop a value from the stack and returns it int pop(t_stack **s) { t_stack* tmp; int ret; tmp = (*s)->next; ret = (*s)->val; free(*s); (*s) = tmp; return ret; } int isempty (t_stack *t) { return t == NULL; } //function to transfer a string(str) to int (value) //returns -1 when success , i otherwise int str2int(char *str,int *value) { int i; *value = 0; int sign=(str[0]=='-' ? -1 : 1); for(i=(str[0]=='-' ? 1 : 0);str[i]!=0;i++) { if(!(str[i]>=48 && str[i]<=57)) // Ascii char 0 to 9 return i; *value= *value*10+(str[i]-48); } *value = *value * sign; return -1; } //a function that takes a string, transfer it into integer and make operation using a stack void function(t_stack *stack, char *str) { char x[10]=" "; int y,j,i=0,z; printf("++\n"); if(str[i] != '\0') { strcpy(x, strtok(str, " ")); z= str2int(x, &y); if(z == -1) { push(&stack,y); i=i+2; } } while(str[i] != '\0') { strcpy(x, strtok(NULL, " ")); z= str2int(x, &y); if(z == -1) { printf("yes %d",y); push(&stack,y); i=i+2; } else { y=pop(&stack); j=pop(&stack); if(x[0] == '+' ) push(&stack,y+j); else if (x[0] == '-' ) push(&stack,j-y); else if(x[0] == '*' ) push(&stack,j*y); else if(x[0] == '/') push (&stack ,j/y); } } } int main() { t_stack *s; initstack(&s); char *str="3 5 +"; function(s,str); return 0; } `

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• How can I use the Boost Graph Library to lay out verticies?

  - by Mike

  I'm trying to lay out vertices using the Boost Graph Library. However, I'm running into some compilation issues which I'm unsure about. Am I using the BGL in an improper manner? My code is: PositionVec position_vec(2); PositionMap position(position_vec.begin(), get(vertex_index, g)); int iterations = 100; double width = 100.0; double height = 100.0; minstd_rand gen; rectangle_topology<> topology(gen, 0, 0, 100, 100); fruchterman_reingold_force_directed_layout(g, position, topology); //Compile fails on this line The diagnostics produced by clang++(I've also tried GCC) are: In file included from test.cpp:2: /Volumes/Data/mike/Downloads/boost_1_43_0/boost/graph/fruchterman_reingold.hpp:95:3: error: no member named 'dimensions' in 'boost::simple_point<double>' BOOST_STATIC_ASSERT (Point::dimensions == 2); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from test.cpp:2: In file included from /Volumes/Data/mike/Downloads/boost_1_43_0/boost/graph/fruchterman_reingold.hpp:13: In file included from /Volumes/Data/mike/Downloads/boost_1_43_0/boost/graph/graph_traits.hpp:15: In file included from /Volumes/Data/mike/Downloads/boost_1_43_0/boost/tuple/tuple.hpp:24: /Volumes/Data/mike/Downloads/boost_1_43_0/boost/static_assert.hpp:118:49: note: instantiated from: sizeof(::boost::STATIC_ASSERTION_FAILURE< BOOST_STATIC_ASSERT_BOOL_CAST( B ) >)>\ ^ In file included from test.cpp:2: /Volumes/Data/mike/Downloads/boost_1_43_0/boost/graph/fruchterman_reingold.hpp:95:3: note: instantiated from: BOOST_STATIC_ASSERT (Point::dimensions == 2); ^ ~~~~~~~ /Volumes/Data/mike/Downloads/boost_1_43_0/boost/graph/fruchterman_reingold.hpp:95:31: note: instantiated from: BOOST_STATIC_ASSERT (Point::dimensions == 2); ~~~~~~~^ /Volumes/Data/mike/Downloads/boost_1_43_0/boost/graph/fruchterman_reingold.hpp:417:19: note: in instantiation of template class 'boost::grid_force_pairs<boost::rectangle_topology<boost::random::linear_congruential<int, 48271, 0, 2147483647, 399268537> >, boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::simple_point<double> *, std::vector<boost::simple_point<double>, std::allocator<boost::simple_point<double> > > >, boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::basic_string<char>, boost::no_property>, unsigned long>, boost::simple_point<double>, boost::simple_point<double> &> >' requested here make_grid_force_pairs(topology, position, g)), ^ /Volumes/Data/mike/Downloads/boost_1_43_0/boost/graph/fruchterman_reingold.hpp:431:3: note: in instantiation of function template specialization 'boost::fruchterman_reingold_force_directed_layout<boost::rectangle_topology<boost::random::linear_congruential<int, 48271, 0, 2147483647, 399268537> >, boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::property<boost::vertex_name_t, std::basic_string<char>, boost::no_property>, boost::no_property, boost::no_property, boost::listS>, boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::simple_point<double> *, std::vector<boost::simple_point<double>, std::allocator<boost::simple_point<double> > > >, boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::basic_string<char>, boost::no_property>, unsigned long>, boost::simple_point<double>, boost::simple_point<double> &>, boost::square_distance_attractive_force, boost::attractive_force_t, boost::no_property>' requested here fruchterman_reingold_force_directed_layout ^ test.cpp:48:3: note: in instantiation of function template specialization 'boost::fruchterman_reingold_force_directed_layout<boost::rectangle_topology<boost::random::linear_congruential<int, 48271, 0, 2147483647, 399268537> >, boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::property<boost::vertex_name_t, std::basic_string<char>, boost::no_property>, boost::no_property, boost::no_property, boost::listS>, boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::simple_point<double> *, std::vector<boost::simple_point<double>, std::allocator<boost::simple_point<double> > > >, boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_name_t, std::basic_string<char>, boost::no_property>, unsigned long>, boost::simple_point<double>, boost::simple_point<double> &> >' requested here fruchterman_reingold_force_directed_layout(g, position, topology); ^ 1 error generated.

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• ubuntu 13.10 kvm binary is deprecated, please use qemu-system-x86_64

  - by ??1986

  I just upgrade from 13.04 to 13.10 and I have this issue when I run my KVM Unable to complete install: 'internal error: process exited while connecting to monitor: W: kvm binary is deprecated, please use qemu-system-x86_64 instead char device redirected to /dev/pts/10 (label charserial0) failed to initialize KVM: Device or resource busy Detail Error: Traceback (most recent call last): File "/usr/share/virt-manager/virtManager/asyncjob.py", line 96, in cb_wrapper callback(asyncjob, *args, **kwargs) File "/usr/share/virt-manager/virtManager/create.py", line 1983, in do_install guest.start_install(False, meter=meter) File "/usr/lib/python2.7/dist-packages/virtinst/Guest.py", line 1246, in start_install noboot) File "/usr/lib/python2.7/dist-packages/virtinst/Guest.py", line 1314, in _create_guest dom = self.conn.createLinux(start_xml or final_xml, 0) File "/usr/lib/python2.7/dist-packages/libvirt.py", line 2892, in createLinux if ret is None:raise libvirtError('virDomainCreateLinux() failed', conn=self) libvirtError: internal error: process exited while connecting to monitor: W: kvm binary is deprecated, please use qemu-system-x86_64 instead char device redirected to /dev/pts/8 (label charserial0) failed to initialize KVM: Device or resource busy

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• Speeding up a search .net 4.0

  - by user231465

  Wondering if I can speed up the search. I need to build a functionality that has to be used by many UI screens The one I have got works but I need to make sure I am implementing a fast algoritim if you like It's like an incremental search. User types a word to search for eg const string searchFor = "Guinea"; const char nextLetter = ' ' It looks in the list and returns 2 records "Guinea and Guinea Bissau " User types a word to search for eg const string searchFor = "Gu"; const char nextLetter = 'i' returns 3 results. This is the function but I would like to speed it up. Is there a pattern for this kind of search? class Program { static void Main() { //Find all countries that begin with string + a possible letter added to it //const string searchFor = "Guinea"; //const char nextLetter = ' '; //returns 2 results const string searchFor = "Gu"; const char nextLetter = 'i'; List<string> result = FindPossibleMatches(searchFor, nextLetter); result.ForEach(x=>Console.WriteLine(x)); //returns 3 results Console.Read(); } /// <summary> /// Find all possible matches /// </summary> /// <param name="searchFor">string to search for</param> /// <param name="nextLetter">pretend user as just typed a letter</param> /// <returns></returns> public static List<string> FindPossibleMatches (string searchFor, char nextLetter) { var hashedCountryList = new HashSet<string>(CountriesList()); var result=new List<string>(); IEnumerable<string> tempCountryList = hashedCountryList.Where(x => x.StartsWith(searchFor)); foreach (string item in tempCountryList) { string tempSearchItem; if (nextLetter == ' ') { tempSearchItem = searchFor; } else { tempSearchItem = searchFor + nextLetter; } if(item.StartsWith(tempSearchItem)) { result.Add(item); } } return result; } /// <summary> /// Returns list of countries. /// </summary> public static string[] CountriesList() { return new[] { "Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra", "Angola", "Anguilla", "Antarctica", "Antigua And Barbuda", "Argentina", "Armenia", "Aruba", "Australia", "Austria", "Azerbaijan", "Bahamas", "Bahrain", "Bangladesh", "Barbados", "Belarus", "Belgium", "Belize", "Benin", "Bermuda", "Bhutan", "Bolivia", "Bosnia Hercegovina", "Botswana", "Bouvet Island", "Brazil", "Brunei Darussalam", "Bulgaria", "Burkina Faso", "Burundi", "Byelorussian SSR", "Cambodia", "Cameroon", "Canada", "Cape Verde", "Cayman Islands", "Central African Republic", "Chad", "Chile", "China", "Christmas Island", "Cocos (Keeling) Islands", "Colombia", "Comoros", "Congo", "Cook Islands", "Costa Rica", "Cote D'Ivoire", "Croatia", "Cuba", "Cyprus", "Czech Republic", "Czechoslovakia", "Denmark", "Djibouti", "Dominica", "Dominican Republic", "East Timor", "Ecuador", "Egypt", "El Salvador", "England", "Equatorial Guinea", "Eritrea", "Estonia", "Ethiopia", "Falkland Islands", "Faroe Islands", "Fiji", "Finland", "France", "Gabon", "Gambia", "Georgia", "Germany", "Ghana", "Gibraltar", "Great Britain", "Greece", "Greenland", "Grenada", "Guadeloupe", "Guam", "Guatemela", "Guernsey", "Guiana", "Guinea", "Guinea Bissau", "Guyana", "Haiti", "Heard Islands", "Honduras", "Hong Kong", "Hungary", "Iceland", "India", "Indonesia", "Iran", "Iraq", "Ireland", "Isle Of Man", "Israel", "Italy", "Jamaica", "Japan", "Jersey", "Jordan", "Kazakhstan", "Kenya", "Kiribati", "Korea, South", "Korea, North", "Kuwait", "Kyrgyzstan", "Lao People's Dem. Rep.", "Latvia", "Lebanon", "Lesotho", "Liberia", "Libya", "Liechtenstein", "Lithuania", "Luxembourg", "Macau", "Macedonia", "Madagascar", "Malawi", "Malaysia", "Maldives", "Mali", "Malta", "Mariana Islands", "Marshall Islands", "Martinique", "Mauritania", "Mauritius", "Mayotte", "Mexico", "Micronesia", "Moldova", "Monaco", "Mongolia", "Montserrat", "Morocco", "Mozambique", "Myanmar", "Namibia", "Nauru", "Nepal", "Netherlands", "Netherlands Antilles", "Neutral Zone", "New Caledonia", "New Zealand", "Nicaragua", "Niger", "Nigeria", "Niue", "Norfolk Island", "Northern Ireland", "Norway", "Oman", "Pakistan", "Palau", "Panama", "Papua New Guinea", "Paraguay", "Peru", "Philippines", "Pitcairn", "Poland", "Polynesia", "Portugal", "Puerto Rico", "Qatar", "Reunion", "Romania", "Russian Federation", "Rwanda", "Saint Helena", "Saint Kitts", "Saint Lucia", "Saint Pierre", "Saint Vincent", "Samoa", "San Marino", "Sao Tome and Principe", "Saudi Arabia", "Scotland", "Senegal", "Seychelles", "Sierra Leone", "Singapore", "Slovakia", "Slovenia", "Solomon Islands", "Somalia", "South Africa", "South Georgia", "Spain", "Sri Lanka", "Sudan", "Suriname", "Svalbard", "Swaziland", "Sweden", "Switzerland", "Syrian Arab Republic", "Taiwan", "Tajikista", "Tanzania", "Thailand", "Togo", "Tokelau", "Tonga", "Trinidad and Tobago", "Tunisia", "Turkey", "Turkmenistan", "Turks and Caicos Islands", "Tuvalu", "Uganda", "Ukraine", "United Arab Emirates", "United Kingdom", "United States", "Uruguay", "Uzbekistan", "Vanuatu", "Vatican City State", "Venezuela", "Vietnam", "Virgin Islands", "Wales", "Western Sahara", "Yemen", "Yugoslavia", "Zaire", "Zambia", "Zimbabwe" }; } } } Any suggestions? Thanks

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• Visual C++ 2010 Winform Errors C2238, C2059, C1075.

  - by tracelez

  It errors when I try compile. I cut the code out of the program and the program works and complies correctly. Not sure why it doesn't like this. This part of the code does single digit math with numeric strings that are converted into a char arrays. ** Error 2 error C2238: unexpected token(s) preceding ';' C:\Users\Alpha\documents\visual studio 2010\Projects\Win32 Form c++\Win32 Form c++\Win32 Form c++.cpp 10 1 Win32 Form c++ ** Error 1 error C2059: syntax error : 'namespace' C:\Users\Alpha\documents\visual studio 2010\Projects\Win32 Form c++\Win32 Form c++\Win32 Form c++.cpp 10 1 Win32 Form c++ ** Error 3 error C1075: end of file found before the left brace '{' at 'c:\users\alpha\documents\visual studio 2010\projects\win32 form c++\win32 form c++\Form1.h(40)' was matched C:\Users\Alpha\documents\visual studio 2010\Projects\Win32 Form c++\Win32 Form c++\Win32 Form c++.cpp 23 1 Win32 Form c++ ////// ////// // chX[] and chY[] are char arrays from functional part of program std::reverse( chX, &chX[ strlen( chX ) ] ); std::reverse( chY, &chY[ strlen( chY ) ] ); // makes sure x is larger or equal to y...makes looping logic easier if (strlen(chX) < strlen(chY)) { char *chZ = chX; chX = chY; chY = chZ; } //Variables for this part of the program char chX2; char chY2; std::string strSum; int sum = 0; bool carryth1 = false; int x=0; int y=0; for (int i = 0; i <= (strlen(chX)-1); i++) { if (i <= strlen(chY)-1) { chX2= chX[i]; chY2= chY[i]; x = atoi(chX2); y = atoi(chY2); //x = atoi(chX[i]); sum = x+y+(int)carryth1; carryth1 = false; if (sum > 9) { if(i == 0) { sum -=10; strSum = itoa(sum); carryth1 = true; } else { sum -=10; strSum += itoa(sum); carryth1 = true; } } else { if(i == 0) { strSum = itoa(sum); } else { strSum += itoa(sum); } } else { y = 0; chX2= chX[i]; x = atoi(chX2); sum = x+y+(int)carryth1; if((i == strlen(chX)-1)&& (carryth1 == true) && (x == 9)) { strSum += "10"; } else { strSum = itoa(sum); } } std::reverse( strSum, &strSum[ strlen( strSum ) ] ); //Creates new string for txtDisplay this simplifies conversions String^ strDisplay = "X is " + gcnew String((strX1.c_str())) + " Y is " +gcnew String((strY1.c_str())) + " \r\n " ; strDisplay += "The sum of the X + Y = "; txtDisplay->Text = gcnew String((strSum.c_str())) ;

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• Howto install google-mock on Ubuntu 12.10

  - by user1459339

  I am having hard time trying to install Google C++ Mocking Framework. I have successfully run sudo apt-get install google-mock. Then I tried to compile this sample file #include "gmock/gmock.h" int main(int argc, char** argv) { ::testing::InitGoogleMock(&argc, argv); return RUN_ALL_TESTS(); } with g++ -lgmock main.cpp and these errors have shown main.cpp:(.text+0x1e): undefined reference to `testing::InitGoogleMock(int*, char**)' main.cpp:(.text+0x23): undefined reference to `testing::UnitTest::GetInstance()' main.cpp:(.text+0x2b): undefined reference to `testing::UnitTest::Run()' collect2: error: ld returned 1 exit status I guess the linker can not find the library files. Does anybody know how to fix this?

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• Bullet physics debug drawing not working

  - by Krishnabhadra

  Background I am following on from this question, which isn't answered yet. Basically I have a cube and a UVSphere in my scene, with UVSphere on the top of the cube without touching the cube. Both exported from blender. When I run the app The UVSphere does circle around the cube for 3 or 4 times and jump out of the scene. What I actually expect was the sphere to fall on top of the cube. What this question about From the comment to the linked question, I got to know about bullet debug drawing, which helps in debugging by drawing outline of physics bodies which are normally invisible. I did some research on that and came up with the code given below. From whatever I have read, below code should work, but it doesn't. My Code My bullet initialization code. -(void) initializeScene { /*Setup physics world*/ _physicsWorld = [[CC3PhysicsWorld alloc] init]; [_physicsWorld setGravity:0 y:-9.8 z:0]; /*Setting up debug draw*/ MyDebugDraw *draw = new MyDebugDraw; draw->setDebugMode(draw->getDebugMode() | btIDebugDraw::DBG_DrawWireframe ); _physicsWorld._discreteDynamicsWorld->setDebugDrawer(draw); /*Setup camera and lamb*/ ………….. //This simpleCube.pod contains the cube [self addContentFromPODFile: @"simpleCube.pod"]; //This file contains sphere [self addContentFromPODFile: @"SimpleSphere.pod"]; [self createGLBuffers]; CC3MeshNode* cubeNode = (CC3MeshNode*)[self getNodeNamed:@"Cube"]; CC3MeshNode* sphereNode = (CC3MeshNode*)[self getNodeNamed:@"Sphere"]; // both cubeNode and sphereNode are not nil from this point float *cVertexData = (float*)((CC3VertexArrayMesh*)cubeNode.mesh) .vertexLocations.vertices; int cVertexCount = ((CC3VertexArrayMesh*)cubeNode.mesh) .vertexLocations.vertexCount; btTriangleMesh* cTriangleMesh = new btTriangleMesh(); int offset = 0; for (int i = 0; i < (cVertexCount / 3); i++) { unsigned int index1 = offset; unsigned int index2 = offset+6; unsigned int index3 = offset+12; cTriangleMesh->addTriangle( btVector3(cVertexData[index1], cVertexData[index1+1], cVertexData[index1+2]), btVector3(cVertexData[index2], cVertexData[index2+1], cVertexData[index2+2]), btVector3(cVertexData[index3], cVertexData[index3+1], cVertexData[index3+2])); offset += 18; } [self releaseRedundantData]; /*Create a triangle mesh from the vertices*/ btBvhTriangleMeshShape* cTriMeshShape = new btBvhTriangleMeshShape(cTriangleMesh,true); btCollisionShape *sphereShape = new btSphereShape(1); gTriMeshObject = [_physicsWorld createPhysicsObjectTrimesh:cubeNode shape:cTriMeshShape mass:0 restitution:1.0 position:cubeNode.location]; sphereObject = [_physicsWorld createPhysicsObject:sphereNode shape:sphereShape mass:1 restitution:0.1 position:sphereNode.location]; sphereObject.rigidBody->setDamping(0.1,0.8); /*Enable debug drawing*/ _physicsWorld._discreteDynamicsWorld->debugDrawWorld(); } And My btIDebugDraw implementation (MyDebugDraw.h) //MyDebugDraw.h class MyDebugDraw: public btIDebugDraw{ int m_debugMode; public: virtual void drawLine(const btVector3& from,const btVector3& to ,const btVector3& color); virtual void drawContactPoint(const btVector3& PointOnB ,const btVector3& normalOnB,btScalar distance ,int lifeTime,const btVector3& color); virtual void reportErrorWarning(const char* warningString); virtual void draw3dText(const btVector3& location ,const char* textString); virtual void setDebugMode(int debugMode); virtual int getDebugMode() const; }; void MyDebugDraw::drawLine(const btVector3& from,const btVector3& to ,const btVector3& color){ LogInfo(@"Works!!"); glPushMatrix(); glColor4f(color.getX(), color.getY(), color.getZ(), 1.0); const GLfloat line[] = { from.getX()*1, from.getY()*1, from.getZ()*1, //point A to.getX()*1, to.getY()*1,to.getZ()*1 //point B }; glVertexPointer( 3, GL_FLOAT, 0, &line ); glPointSize( 5.0f ); glDrawArrays( GL_POINTS, 0, 2 ); glDrawArrays( GL_LINES, 0, 2 ); glPopMatrix(); } void MyDebugDraw::drawContactPoint(const btVector3 &PointOnB ,const btVector3 &normalOnB, btScalar distance ,int lifeTime, const btVector3 &color){ } void MyDebugDraw::reportErrorWarning(const char *warningString){ } void MyDebugDraw::draw3dText(const btVector3 &location , const char *textString){ } void MyDebugDraw::setDebugMode(int debugMode){ } int MyDebugDraw::getDebugMode() const{ return DBG_DrawWireframe; } My Problem The drawLine method is getting called. I can see the cube and sphere in place. Sphere again does some circling around the cube before jumping off. No debug lines are getting drawn.

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• C#/.NET Little Wonders: The ConcurrentDictionary

  - by James Michael Hare

  Once again we consider some of the lesser known classes and keywords of C#.  In this series of posts, we will discuss how the concurrent collections have been developed to help alleviate these multi-threading concerns.  Last week’s post began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>.  Today's post discusses the ConcurrentDictionary<T> (originally I had intended to discuss ConcurrentBag this week as well, but ConcurrentDictionary had enough information to create a very full post on its own!).  Finally next week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. Recap As you'll recall from the previous post, the original collections were object-based containers that accomplished synchronization through a Synchronized member.  While these were convenient because you didn't have to worry about writing your own synchronization logic, they were a bit too finely grained and if you needed to perform multiple operations under one lock, the automatic synchronization didn't buy much. With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization.  This cuts both ways in that you have a lot more control as a developer over when and how fine-grained you want to synchronize, but on the other hand if you just want simple synchronization it creates more work. With .NET 4.0, we get the best of both worlds in generic collections.  A new breed of collections was born called the concurrent collections in the System.Collections.Concurrent namespace.  These amazing collections are fine-tuned to have best overall performance for situations requiring concurrent access.  They are not meant to replace the generic collections, but to simply be an alternative to creating your own locking mechanisms. Among those concurrent collections were the ConcurrentStack<T> and ConcurrentQueue<T> which provide classic LIFO and FIFO collections with a concurrent twist.  As we saw, some of the traditional methods that required calls to be made in a certain order (like checking for not IsEmpty before calling Pop()) were replaced in favor of an umbrella operation that combined both under one lock (like TryPop()). Now, let's take a look at the next in our series of concurrent collections!For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here. ConcurrentDictionary – the fully thread-safe dictionary The ConcurrentDictionary<TKey,TValue> is the thread-safe counterpart to the generic Dictionary<TKey, TValue> collection.  Obviously, both are designed for quick – O(1) – lookups of data based on a key.  If you think of algorithms where you need lightning fast lookups of data and don’t care whether the data is maintained in any particular ordering or not, the unsorted dictionaries are generally the best way to go. Note: as a side note, there are sorted implementations of IDictionary, namely SortedDictionary and SortedList which are stored as an ordered tree and a ordered list respectively.  While these are not as fast as the non-sorted dictionaries – they are O(log2 n) – they are a great combination of both speed and ordering -- and still greatly outperform a linear search. Now, once again keep in mind that if all you need to do is load a collection once and then allow multi-threaded reading you do not need any locking.  Examples of this tend to be situations where you load a lookup or translation table once at program start, then keep it in memory for read-only reference.  In such cases locking is completely non-productive. However, most of the time when we need a concurrent dictionary we are interleaving both reads and updates.  This is where the ConcurrentDictionary really shines!  It achieves its thread-safety with no common lock to improve efficiency.  It actually uses a series of locks to provide concurrent updates, and has lockless reads!  This means that the ConcurrentDictionary gets even more efficient the higher the ratio of reads-to-writes you have. ConcurrentDictionary and Dictionary differences For the most part, the ConcurrentDictionary<TKey,TValue> behaves like it’s Dictionary<TKey,TValue> counterpart with a few differences.  Some notable examples of which are: Add() does not exist in the concurrent dictionary. This means you must use TryAdd(), AddOrUpdate(), or GetOrAdd().  It also means that you can’t use a collection initializer with the concurrent dictionary. TryAdd() replaced Add() to attempt atomic, safe adds. Because Add() only succeeds if the item doesn’t already exist, we need an atomic operation to check if the item exists, and if not add it while still under an atomic lock. TryUpdate() was added to attempt atomic, safe updates. If we want to update an item, we must make sure it exists first and that the original value is what we expected it to be.  If all these are true, we can update the item under one atomic step. TryRemove() was added to attempt atomic, safe removes. To safely attempt to remove a value we need to see if the key exists first, this checks for existence and removes under an atomic lock. AddOrUpdate() was added to attempt an thread-safe “upsert”. There are many times where you want to insert into a dictionary if the key doesn’t exist, or update the value if it does.  This allows you to make a thread-safe add-or-update. GetOrAdd() was added to attempt an thread-safe query/insert. Sometimes, you want to query for whether an item exists in the cache, and if it doesn’t insert a starting value for it.  This allows you to get the value if it exists and insert if not. Count, Keys, Values properties take a snapshot of the dictionary. Accessing these properties may interfere with add and update performance and should be used with caution. ToArray() returns a static snapshot of the dictionary. That is, the dictionary is locked, and then copied to an array as a O(n) operation.  GetEnumerator() is thread-safe and efficient, but allows dirty reads. Because reads require no locking, you can safely iterate over the contents of the dictionary.  The only downside is that, depending on timing, you may get dirty reads. Dirty reads during iteration The last point on GetEnumerator() bears some explanation.  Picture a scenario in which you call GetEnumerator() (or iterate using a foreach, etc.) and then, during that iteration the dictionary gets updated.  This may not sound like a big deal, but it can lead to inconsistent results if used incorrectly.  The problem is that items you already iterated over that are updated a split second after don’t show the update, but items that you iterate over that were updated a split second before do show the update.  Thus you may get a combination of items that are “stale” because you iterated before the update, and “fresh” because they were updated after GetEnumerator() but before the iteration reached them. Let’s illustrate with an example, let’s say you load up a concurrent dictionary like this: 1: // load up a dictionary. 2: var dictionary = new ConcurrentDictionary<string, int>(); 3:  4: dictionary["A"] = 1; 5: dictionary["B"] = 2; 6: dictionary["C"] = 3; 7: dictionary["D"] = 4; 8: dictionary["E"] = 5; 9: dictionary["F"] = 6; Then you have one task (using the wonderful TPL!) to iterate using dirty reads: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); And one task to attempt updates in a separate thread (probably): 1: // attempt updates in a separate thread 2: var updateTask = new Task(() => 3: { 4: // iterates, and updates the value by one 5: foreach (var pair in dictionary) 6: { 7: dictionary[pair.Key] = pair.Value + 1; 8: } 9: }); Now that we’ve done this, we can fire up both tasks and wait for them to complete: 1: // start both tasks 2: updateTask.Start(); 3: iterationTask.Start(); 4:  5: // wait for both to complete. 6: Task.WaitAll(updateTask, iterationTask); Now, if I you didn’t know about the dirty reads, you may have expected to see the iteration before the updates (such as A:1, B:2, C:3, D:4, E:5, F:6).  However, because the reads are dirty, we will quite possibly get a combination of some updated, some original.  My own run netted this result: 1: F:6 2: E:6 3: D:5 4: C:4 5: B:3 6: A:2 Note that, of course, iteration is not in order because ConcurrentDictionary, like Dictionary, is unordered.  Also note that both E and F show the value 6.  This is because the output task reached F before the update, but the updates for the rest of the items occurred before their output (probably because console output is very slow, comparatively). If we want to always guarantee that we will get a consistent snapshot to iterate over (that is, at the point we ask for it we see precisely what is in the dictionary and no subsequent updates during iteration), we should iterate over a call to ToArray() instead: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary.ToArray()) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); The atomic Try…() methods As you can imagine TryAdd() and TryRemove() have few surprises.  Both first check the existence of the item to determine if it can be added or removed based on whether or not the key currently exists in the dictionary: 1: // try add attempts an add and returns false if it already exists 2: if (dictionary.TryAdd("G", 7)) 3: Console.WriteLine("G did not exist, now inserted with 7"); 4: else 5: Console.WriteLine("G already existed, insert failed."); TryRemove() also has the virtue of returning the value portion of the removed entry matching the given key: 1: // attempt to remove the value, if it exists it is removed and the original is returned 2: int removedValue; 3: if (dictionary.TryRemove("C", out removedValue)) 4: Console.WriteLine("Removed C and its value was " + removedValue); 5: else 6: Console.WriteLine("C did not exist, remove failed."); Now TryUpdate() is an interesting creature.  You might think from it’s name that TryUpdate() first checks for an item’s existence, and then updates if the item exists, otherwise it returns false.  Well, note quite... It turns out when you call TryUpdate() on a concurrent dictionary, you pass it not only the new value you want it to have, but also the value you expected it to have before the update.  If the item exists in the dictionary, and it has the value you expected, it will update it to the new value atomically and return true.  If the item is not in the dictionary or does not have the value you expected, it is not modified and false is returned. 1: // attempt to update the value, if it exists and if it has the expected original value 2: if (dictionary.TryUpdate("G", 42, 7)) 3: Console.WriteLine("G existed and was 7, now it's 42."); 4: else 5: Console.WriteLine("G either didn't exist, or wasn't 7."); The composite Add methods The ConcurrentDictionary also has composite add methods that can be used to perform updates and gets, with an add if the item is not existing at the time of the update or get. The first of these, AddOrUpdate(), allows you to add a new item to the dictionary if it doesn’t exist, or update the existing item if it does.  For example, let’s say you are creating a dictionary of counts of stock ticker symbols you’ve subscribed to from a market data feed: 1: public sealed class SubscriptionManager 2: { 3: private readonly ConcurrentDictionary<string, int> _subscriptions = new ConcurrentDictionary<string, int>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public void AddSubscription(string tickerKey) 7: { 8: // add a new subscription with count of 1, or update existing count by 1 if exists 9: var resultCount = _subscriptions.AddOrUpdate(tickerKey, 1, (symbol, count) => count + 1); 10:  11: // now check the result to see if we just incremented the count, or inserted first count 12: if (resultCount == 1) 13: { 14: // subscribe to symbol... 15: } 16: } 17: } Notice the update value factory Func delegate.  If the key does not exist in the dictionary, the add value is used (in this case 1 representing the first subscription for this symbol), but if the key already exists, it passes the key and current value to the update delegate which computes the new value to be stored in the dictionary.  The return result of this operation is the value used (in our case: 1 if added, existing value + 1 if updated). Likewise, the GetOrAdd() allows you to attempt to retrieve a value from the dictionary, and if the value does not currently exist in the dictionary it will insert a value.  This can be handy in cases where perhaps you wish to cache data, and thus you would query the cache to see if the item exists, and if it doesn’t you would put the item into the cache for the first time: 1: public sealed class PriceCache 2: { 3: private readonly ConcurrentDictionary<string, double> _cache = new ConcurrentDictionary<string, double>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public double QueryPrice(string tickerKey) 7: { 8: // check for the price in the cache, if it doesn't exist it will call the delegate to create value. 9: return _cache.GetOrAdd(tickerKey, symbol => GetCurrentPrice(symbol)); 10: } 11:  12: private double GetCurrentPrice(string tickerKey) 13: { 14: // do code to calculate actual true price. 15: } 16: } There are other variations of these two methods which vary whether a value is provided or a factory delegate, but otherwise they work much the same. Oddities with the composite Add methods The AddOrUpdate() and GetOrAdd() methods are totally thread-safe, on this you may rely, but they are not atomic.  It is important to note that the methods that use delegates execute those delegates outside of the lock.  This was done intentionally so that a user delegate (of which the ConcurrentDictionary has no control of course) does not take too long and lock out other threads. This is not necessarily an issue, per se, but it is something you must consider in your design.  The main thing to consider is that your delegate may get called to generate an item, but that item may not be the one returned!  Consider this scenario: A calls GetOrAdd and sees that the key does not currently exist, so it calls the delegate.  Now thread B also calls GetOrAdd and also sees that the key does not currently exist, and for whatever reason in this race condition it’s delegate completes first and it adds its new value to the dictionary.  Now A is done and goes to get the lock, and now sees that the item now exists.  In this case even though it called the delegate to create the item, it will pitch it because an item arrived between the time it attempted to create one and it attempted to add it. Let’s illustrate, assume this totally contrived example program which has a dictionary of char to int.  And in this dictionary we want to store a char and it’s ordinal (that is, A = 1, B = 2, etc).  So for our value generator, we will simply increment the previous value in a thread-safe way (perhaps using Interlocked): 1: public static class Program 2: { 3: private static int _nextNumber = 0; 4:  5: // the holder of the char to ordinal 6: private static ConcurrentDictionary<char, int> _dictionary 7: = new ConcurrentDictionary<char, int>(); 8:  9: // get the next id value 10: public static int NextId 11: { 12: get { return Interlocked.Increment(ref _nextNumber); } 13: } Then, we add a method that will perform our insert: 1: public static void Inserter() 2: { 3: for (int i = 0; i < 26; i++) 4: { 5: _dictionary.GetOrAdd((char)('A' + i), key => NextId); 6: } 7: } Finally, we run our test by starting two tasks to do this work and get the results… 1: public static void Main() 2: { 3: // 3 tasks attempting to get/insert 4: var tasks = new List<Task> 5: { 6: new Task(Inserter), 7: new Task(Inserter) 8: }; 9:  10: tasks.ForEach(t => t.Start()); 11: Task.WaitAll(tasks.ToArray()); 12:  13: foreach (var pair in _dictionary.OrderBy(p => p.Key)) 14: { 15: Console.WriteLine(pair.Key + ":" + pair.Value); 16: } 17: } If you run this with only one task, you get the expected A:1, B:2, ..., Z:26.  But running this in parallel you will get something a bit more complex.  My run netted these results: 1: A:1 2: B:3 3: C:4 4: D:5 5: E:6 6: F:7 7: G:8 8: H:9 9: I:10 10: J:11 11: K:12 12: L:13 13: M:14 14: N:15 15: O:16 16: P:17 17: Q:18 18: R:19 19: S:20 20: T:21 21: U:22 22: V:23 23: W:24 24: X:25 25: Y:26 26: Z:27 Notice that B is 3?  This is most likely because both threads attempted to call GetOrAdd() at roughly the same time and both saw that B did not exist, thus they both called the generator and one thread got back 2 and the other got back 3.  However, only one of those threads can get the lock at a time for the actual insert, and thus the one that generated the 3 won and the 3 was inserted and the 2 got discarded.  This is why on these methods your factory delegates should be careful not to have any logic that would be unsafe if the value they generate will be pitched in favor of another item generated at roughly the same time.  As such, it is probably a good idea to keep those generators as stateless as possible. Summary The ConcurrentDictionary is a very efficient and thread-safe version of the Dictionary generic collection.  It has all the benefits of type-safety that it’s generic collection counterpart does, and in addition is extremely efficient especially when there are more reads than writes concurrently. Tweet Technorati Tags: C#, .NET, Concurrent Collections, Collections, Little Wonders, Black Rabbit Coder,James Michael Hare

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• Binary Tree in C Insertion Error

  - by Paul

  I'm quite new to C and I'm trying to implement a Binary Tree in C which will store a number and a string and then print them off e.g. 1 : Bread 2 : WashingUpLiquid etc. The code I have so far is: #include <stdio.h> #include <stdlib.h> #define LENGTH 300 struct node { int data; char * definition; struct node *left; struct node *right; }; struct node *node_insert(struct node *p, int value, char * word); void print_preorder(struct node *p); int main(void) { int i = 0; int d = 0; char def[LENGTH]; struct node *root = NULL; for(i = 0; i < 2; i++) { printf("Please enter a number: \n"); scanf("%d", &d); printf("Please enter a definition for this word:\n"); scanf("%s", def); root = node_insert(root, d, def); printf("%s\n", def); } printf("preorder : "); print_preorder(root); printf("\n"); return 0; } struct node *node_insert(struct node *p, int value, char * word) { struct node *tmp_one = NULL; struct node *tmp_two = NULL; if(p == NULL) { p = (struct node *)malloc(sizeof(struct node)); p->data = value; p->definition = word; p->left = p->right = NULL; } else { tmp_one = p; while(tmp_one != NULL) { tmp_two = tmp_one; if(tmp_one->data > value) tmp_one = tmp_one->left; else tmp_one = tmp_one->right; } if(tmp_two->data > value) { tmp_two->left = (struct node *)malloc(sizeof(struct node)); tmp_two = tmp_two->left; tmp_two->data = value; tmp_two->definition = word; tmp_two->left = tmp_two->right = NULL; } else { tmp_two->right = (struct node *)malloc(sizeof(struct node)); tmp_two = tmp_two->right; tmp_two->data = value; tmp_two->definition = word; tmp_two->left = tmp_two->right = NULL; } } return(p); } void print_preorder(struct node *p) { if(p != NULL) { printf("%d : %s\n", p->data, p->definition); print_preorder(p->left); print_preorder(p->right); } } At the moment it seems to work for the ints but the description part only prints out for the last one entered. I assume it has something to do with pointers on the char array but I had no luck getting it to work. Any ideas or advice? Thanks

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• SQL Select syntax error

  - by Odette

  hi guys thanks for your help yesterday. I am now trying to incorporate the query from yesterday into an existing query so I can show the highest itemcode's reporting group in the existing query..but I have a syntax error somewhere at my Select statement. ERROR: Keyword SELECT not expected. I have tried putting brackets at every possible place but still no go..can you please help? (ps-this whole query has been giving me nightmares!) WITH CALC1 AS (SELECT OTQUOT, OTIT01 AS ITEMS, ROUND(OQCQ01 * OVRC01,2) AS COST FROM @[email protected] WHERE OTIT01 < '' UNION ALL SELECT OTQUOT, OTIT02 AS ITEMS, ROUND(OQCQ02 * OVRC02,2) AS COST FROM @[email protected] WHERE OTIT02 < '' UNION ALL SELECT OTQUOT, OTIT03 AS ITEMS, ROUND(OQCQ03 * OVRC03,2) AS COST FROM @[email protected] WHERE OTIT03 < '' UNION ALL SELECT OTQUOT, OTIT04 AS ITEMS, ROUND(OQCQ04 * OVRC04,2) AS COST FROM @[email protected] WHERE OTIT04 < '' UNION ALL SELECT OTQUOT, OTIT05 AS ITEMS, ROUND(OQCQ05 * OVRC05,2) AS COST FROM @[email protected] WHERE OTIT05 < '' UNION ALL SELECT OTQUOT, OTIT06 AS ITEMS, ROUND(OQCQ06 * OVRC06,2) AS COST FROM @[email protected] WHERE OTIT06 < '' UNION ALL SELECT OTQUOT, OTIT07 AS ITEMS, ROUND(OQCQ07 * OVRC07,2) AS COST FROM @[email protected] WHERE OTIT07 < '' UNION ALL SELECT OTQUOT, OTIT08 AS ITEMS, ROUND(OQCQ08 * OVRC08,2) AS COST FROM @[email protected] WHERE OTIT08 < '' UNION ALL SELECT OTQUOT, OTIT09 AS ITEMS, ROUND(OQCQ09 * OVRC09,2) AS COST FROM @[email protected] WHERE OTIT09 < '' UNION ALL SELECT OTQUOT, OTIT10 AS ITEMS, ROUND(OQCQ10 * OVRC10,2) AS COST FROM @[email protected] WHERE OTIT10 < '' ) (SELECT OTQUOT, DESC FROM ( SELECT OTQUOT, ITEMS, B.IXRPGP AS GROUP, C.OTRDSC AS DESC, COST, ROW_NUMBER() OVER (ORDER BY COST DESC) AS RN FROM CALC1 AS A INNER JOIN @[email protected] AS B ON (A.ITEMS = B.IKITMC) INNER JOIN DATAGRP.GDSGRP AS C ON (B.IXRPGP = C.OKRPGP) ) T WHERE T.RN = 1) SELECT A.OKPBRN, A.OCAREA, A.OTCCDE, A.OTCNAM, A.OTSMAN, A.OKPBRN||A.OAPNUM AS OTQUOT, A.OTONUM, A.OTCAD1, A.OTCAD2, A.OTCAD3, A.OTPCDE, A.OTDEL1, A.OTDEL2, A.OTDEL3, CHAR(DATE(CASE WHEN SUBSTR(A.ODOQDT,5,4) = '0000' THEN '0001' ELSE SUBSTR(A.ODOQDT,5,4) END ||'-'|| CASE WHEN SUBSTR(A.ODOQDT,4,2) = '00' THEN '01' ELSE SUBSTR(A.ODOQDT,3,2) END ||'-'|| CASE WHEN SUBSTR(A.ODOQDT,1,2) = '00' THEN '01' ELSE SUBSTR(A.ODOQDT,1,2) END), ISO) AS ODOQDT_CCYYMMDD, CHAR(DATE(CASE WHEN SUBSTR(A.ODDELD,7,2) = '' THEN '0001' ELSE '20'||SUBSTR(A.ODDELD,7,2) END ||'-'|| CASE WHEN SUBSTR(A.ODDELD,4,2) = '' THEN '01' ELSE SUBSTR(A.ODDELD,4,2) END ||'-'|| CASE WHEN SUBSTR(A.ODDELD,1,2) = '' THEN '01' ELSE SUBSTR(A.ODDELD,1,2) END), ISO) AS ODDELD_CCYYMMDD, B.DESC, A.OVQTVL FROM @[email protected] AS A INNER JOIN CALC1 AS B ON (A.OKPBRN||A.OAPNUM = B.OTQUOT) WHERE A.OKPBRN = '@OKPBRN@' AND A.OTCCDE NOT LIKE '*DEP%' AND CHAR(DATE(CASE WHEN SUBSTR(A.ODOQDT,5,4) = '0000' THEN '0001' ELSE SUBSTR (A.ODOQDT,5,4) END ||'-'|| CASE WHEN SUBSTR(A.ODOQDT,4,2) = '00' THEN '01' ELSE SUBSTR(A.ODOQDT,3,2) END ||'-'|| CASE WHEN SUBSTR(A.ODOQDT,1,2) = '00' THEN '01' ELSE SUBSTR(A.ODOQDT,1,2) END), ISO) = CHAR(CURDATE() - 3 MONTH, ISO) AND A.OCQF01 = '0' AND A.OCQF02 = '0' AND A.OCQF04 = '0' AND A.OCQF05 = '0' AND A.OCQF06 = '0' AND A.OCQF07 = '0' AND A.OCQF08 = '0' AND A.OCQF09 = '0' AND A.OCQF10 = '1' AND A.OTCGRP LIKE 'S/%' ORDER BY A.OTSMAN ASC, A.OVQTVL DESC, CHAR(DATE(CASE WHEN SUBSTR(A.ODDELD,7,2) = '' THEN '0001' ELSE '20'||SUBSTR(A.ODDELD,7,2) END ||'-'|| CASE WHEN SUBSTR(A.ODDELD,4,2) = '' THEN '01' ELSE SUBSTR(A.ODDELD,4,2) END ||'-'|| CASE WHEN SUBSTR(A.ODDELD,1,2) = '' THEN '01' ELSE SUBSTR(A.ODDELD,1,2) END),ISO) ASC

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• Implement Negascout Algorithm with stack

  - by Dan

  I'm not familiar with how these stack exchange accounts work so if this is double posting I apologize. I asked the same thing on stackoverflow. I have added an AI routine to a game I am working on using the Negascout algorithm. It works great, but when I set a higher maximum depth it can take a few seconds to complete. The problem is it blocks the main thread, and the framework I am using does not have a way to deal with multi-threading properly across platforms. So I am trying to change this routine from recursively calling itself, to just managing a stack (vector) so that I can progress through the routine at a controlled pace and not lock up the application while the AI is thinking. I am getting hung up on the second recursive call in the loop. It relies on a returned value from the first call, so I don't know how to add these to a stack. My Working c++ Recursive Code: MoveScore abNegascout(vector<vector<char> > &board, int ply, int alpha, int beta, char piece) { if (ply==mMaxPly) { return MoveScore(evaluation.evaluateBoard(board, piece, oppPiece)); } int currentScore; int bestScore = -INFINITY; MoveCoord bestMove; int adaptiveBeta = beta; vector<MoveCoord> moveList = evaluation.genPriorityMoves(board, piece, findValidMove(board, piece, false)); if (moveList.empty()) { return MoveScore(bestScore); } bestMove = moveList[0]; for(int i=0;i<moveList.size();i++) { MoveCoord move = moveList[i]; vector<vector<char> > newBoard; newBoard.insert( newBoard.end(), board.begin(), board.end() ); effectMove(newBoard, piece, move.getRow(), move.getCol()); // First Call ****** MoveScore current = abNegascout(newBoard, ply+1, -adaptiveBeta, -max(alpha,bestScore), oppPiece); currentScore = - current.getScore(); if (currentScore>bestScore){ if (adaptiveBeta == beta || ply>=(mMaxPly-2)){ bestScore = currentScore; bestMove = move; }else { // Second Call ****** current = abNegascout(newBoard, ply+1, -beta, -currentScore, oppPiece); bestScore = - current.getScore(); bestMove = move; } if(bestScore>=beta){ return MoveScore(bestMove,bestScore); } adaptiveBeta = max(alpha, bestScore) + 1; } } return MoveScore(bestMove,bestScore); } If someone can please help by explaining how to get this to work with a simple stack. Example code would be much appreciated. While c++ would be perfect, any language that demonstrates how would be great. Thank You.

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• Is this proper OO design for C++?

  - by user121917

  I recently took a software processes course and this is my first time attempting OO design on my own. I am trying to follow OO design principles and C++ conventions. I attempted and gave up on MVC for this application, but I am trying to "decouple" my classes such that they can be easily unit-tested and so that I can easily change the GUI library used and/or the target OS. At this time, I have finished designing classes but have not yet started implementing methods. The function of the software is to log all packets sent and received, and display them on the screen (like WireShark, but for one local process only). The software accomplishes this by hooking the send() and recv() functions in winsock32.dll, or some other pair of analogous functions depending on what the intended Target is. The hooks add packets to SendPacketList/RecvPacketList. The GuiLogic class starts a thread which checks for new packets. When new packets are found, it utilizes the PacketFilter class to determine the formatting for the new packet, and then sends it to MainWindow, a native win32 window (with intent to later port to Qt).1 Full size image of UML class diagram Here are my classes in skeleton/header form (this is my actual code): class PacketModel { protected: std::vector<byte> data; int id; public: PacketModel(); PacketModel(byte* data, unsigned int size); PacketModel(int id, byte* data, unsigned int size); int GetLen(); bool IsValid(); //len >= sizeof(opcode_t) opcode_t GetOpcode(); byte* GetData(); //returns &(data[0]) bool GetData(byte* outdata, int maxlen); void SetData(byte* pdata, int len); int GetId(); void SetId(int id); bool ParseData(char* instr); bool StringRepr(char* outstr); byte& operator[] (const int index); }; class SendPacket : public PacketModel { protected: byte* returnAddy; public: byte* GetReturnAddy(); void SetReturnAddy(byte* addy); }; class RecvPacket : public PacketModel { protected: byte* callAddy; public: byte* GetCallAddy(); void SetCallAddy(byte* addy); }; //problem: packets may be added to list at any time by any number of threads //solution: critical section associated with each packet list class Synch { public: void Enter(); void Leave(); }; template<class PacketType> class PacketList { private: static const int MAX_STORED_PACKETS = 1000; public: static const int DEFAULT_SHOWN_PACKETS = 100; private: vector<PacketType> list; Synch synch; //wrapper for critical section public: void AddPacket(PacketType* packet); PacketType* GetPacket(int id); int TotalPackets(); }; class SendPacketList : PacketList<SendPacket> { }; class RecvPacketList : PacketList<RecvPacket> { }; class Target //one socket { bool Send(SendPacket* packet); bool Inject(RecvPacket* packet); bool InitSendHook(SendPacketList* sendList); bool InitRecvHook(RecvPacketList* recvList); }; class FilterModel { private: opcode_t opcode; int colorID; bool bFilter; char name[41]; }; class FilterFile { private: FilterModel filter; public: void Save(); void Load(); FilterModel* GetFilter(opcode_t opcode); }; class PacketFilter { private: FilterFile filters; public: bool IsFiltered(opcode_t opcode); bool GetName(opcode_t opcode, char* namestr); //return false if name does not exist COLORREF GetColor(opcode_t opcode); //return default color if no custom color }; class GuiLogic { private: SendPacketList sendList; RecvPacketList recvList; PacketFilter packetFilter; void GetPacketRepr(PacketModel* packet); void ReadNew(); void AddToWindow(); public: void Refresh(); //called from thread void GetPacketInfo(int id); //called from MainWindow }; I'm looking for a general review of my OO design, use of UML, and use of C++ features. I especially just want to know if I'm doing anything considerably wrong. From what I've read, design review is on-topic for this site (and off-topic for the Code Review site). Any sort of feedback is greatly appreciated. Thanks for reading this.

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• Error in python - don't understand

  - by Jasper

  Hi, I'm creating a game, and am quite new to Python generally. I created a function 'descriptionGenerator()' which generates a description for characters and objects either randomly or using variables passed to it. It seemed to be working, but every now and then it wouldn't work correctly. So i placed it in a loop, and it never seems to be able to complete the loop without one of the iterations having this problem. The code is as follows: #+------------------------------------------+ #| Name: bitsandpieces.py | #| A module for the 'Europa I' game | #| created for the Game Making Competition | #| | #| Date Created/Modified: | #| 3/4/10 | 3/4/10 | #+------------------------------------------+ # Import the required modules # Import system modules: import time import random # Import 3rd party modules: # Import game modules: # Define the 'descriptionGenerator()' function def descriptionGenerator(descriptionVariables): descriptionVariableSize = len(descriptionVariables) if descriptionVariables[0] == 'char': # If there is only one variable ('char'), create a random description if descriptionVariableSize == 1: # Define choices for descriptionVariables to be generated from gender_choices = ['male', 'female'] hair_choices = ['black', 'red', 'blonde', 'grey', 'brown', 'blue'] hair_choices2 = ['long', 'short', 'cropped', 'curly'] size_choices = ['tubby', 'thin', 'fat', 'almost twig-like'] demeanour_choices = ['glowering', 'bright', 'smiling', 'sombre', 'intelligent'] impression_choices = ['likeable', 'unlikeable', 'dangerous', 'annoying', 'afraid'] # Define description variables gender = random.choice(gender_choices) height = str(float('0.' + str(random.randint(1, 9))) + float(random.randint(1, 2))) if float(height) > 1.8: height_string = 'tall' if float(height) > 2: height_string = 'very tall' elif float(height) < 1.8 and float(height) > 1.5: height_string = 'average' elif float(height) < 1.5: height_string = 'short' if float(height) < 1.3: height_string = 'very short' hair = random.choice(hair_choices2) + ' ' + random.choice(hair_choices) size = random.choice(size_choices) demeanour = random.choice(demeanour_choices) impression = random.choice(impression_choices) # Collect description variables in list 'randomDescriptionVariables' randomDescriptionVariables = ['char', gender, height, height_string, hair, size, demeanour, impression] # Generate description using the 'descriptionGenerator' function descriptionGenerator(randomDescriptionVariables) # Generate the description of a character using the variables passed to the function elif descriptionVariableSize == 8: if descriptionVariables[1] == 'male': if descriptionVariables[7] != 'afraid': print """A %s man, about %s m tall. He has %s hair and is %s. He is %s and you get the impression that he is %s.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) elif descriptionVariables[7] == 'afraid': print """A %s man, about %s m tall. He has %s hair and is %s. He is %s.\nYou feel that you should be %s of him.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) elif descriptionVariables[1] == 'female': if descriptionVariables[7] != 'afraid': print """A %s woman, about %s m tall. She has %s hair and is %s. She is %s and you get the impression that she is %s.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) elif descriptionVariables[7] == 'afraid': print """A %s woman, about %s m tall. She has %s hair and is %s. She is %s.\nYou feel that you should be %s of her.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) else: pass elif descriptionVariables[0] == 'obj': # Insert code here 2 deal with object stuff pass print print myDescriptionVariables = ['char'] i = 0 while i < 30: print print print descriptionGenerator(myDescriptionVariables) i = i + 1 time.sleep(10) When it fails to properly execute it says this: Traceback (most recent call last): File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/Code/Code 2.0/bitsandpieces.py", line 79, in <module> descriptionGenerator(myDescriptionVariables) File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/Code/Code 2.0/bitsandpieces.py", line 50, in descriptionGenerator randomDescriptionVariables = ['char', gender, height, height_string, hair, size, demeanour, impression] UnboundLocalError: local variable 'height_string' referenced before assignment Thanks for any help with this

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• Blender DirectX exporter to Panda3D

  - by jakebird451

  I have been experimenting with Panda3D lately. I have a character made in Blender with various bones and currently with one animation that I wish to export to a *.x format for Panda3D. My current attempt was to export the model was to first export with bones [Armatures] by checking the "Export Armatures" button in the export menu (file name: char.x). Thanks to the *.x file format, I read the file and it seems to have the same bone structure format as the model (with parenting and matrix positional data). The second export was selecting Animations - Full Animation to provide just the animation (file name: char_idle.x). The models exported just fine. I am not sure about the animation yet, but the file seems to be just fine. This is my code for loading the model into python & Panda3D: self.model = Actor("char.x",{"char_idle.x"}) When I run the program the command line provides a couple of errors, the main errors of interest are: :Actor(warning): char.x is not a character! and ... File "C:\Panda3D-1.8.0\direct\actor\Actor.py", line 284, in __init__ if (type(anims[anims.keys()[0]])==type({})): AttributeError: 'set' object has no attribute 'keys' The first error is the most interesting to me. The model works if I leave the animation dictionary blank. With no animations loaded the character appears in its un-animated T position, however the actor warning still shows up. The character should include the various bones when I exported the model right? I am not that experienced with blender, I'm just a programmer. So if the problem lies in blender please try to keep that in mind when posting a reply. I'll try my best to keep up. I also tried to print out the bone structure without any animations loaded and it provides a similar error with the line print self.model.listJoints(): File "C:\Panda3D-1.8.0\direct\actor\Actor.py", line 410, in listJoints Actor.notify.error("no part named: %s" % (partName)) File "C:\Panda3D-1.8.0\direct\directnotify\Notifier.py", line 132, in error raise exception(errorString) StandardError: no part named: modelRoot I really hope it is a simple exporting fix.

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• How to use pipes for nonblocking IPC (UART emulation)

  - by codebauer

  I would like to write some test/emulation code that emulates a serial port connection. The real code looks like this: DUT <- UART - testtool.exe My plan is to use create a test application (CodeUnderTest.out) on linux that forks to launch testool.out with two (read & write) named pipes as arguments. But I cannot figure out how to make all the pipe IO non-blocking! The setup would look like this:. CodeUnderTest.out <- named pipes - testTool.out (lauched from CodeUnderTest.out) I have tried opening the pipes as following: open(wpipe,O_WRONLY|O_NONBLOCK); open(rpipe,O_RDONLY|O_NONBLOCK); But the write blocks until the reader opens the wpipe. Next I tried the following: open(wpipe,O_RDWR|O_NONBLOCK); open(rpipe,O_RDONLY|O_NONBLOCK); But then the reader of the first message never gets any data (doesn't block though) I also tried adding open and close calls around each message, but that didn't work either... Here is some test code: #include <stdio.h> #include <sys/types.h> #include <unistd.h> #include <fcntl.h> pid_t pid; char* rpipe, *wpipe,*x; FILE *rh,*wh; int rfd,wfd; void openrpipe( void ) { rfd = open(rpipe,O_RDONLY|O_NONBLOCK); rh = fdopen(rfd,"rb"); printf("%sopeningr %x\n",x,rh); } void openwpipe( void ) { //Fails when reader not already opened //wfd = open(wpipe,O_WRONLY|O_NONBLOCK); wfd = open(wpipe,O_RDWR|O_NONBLOCK); wh = fdopen(wfd,"wb"); printf("%sopeningw %x\n",x,wh); } void closerpipe( void ) { int i; i = fclose(rh); printf("%sclosingr %d\n",x,i); } void closewpipe( void ) { int i; i = fclose(wh); printf("%sclosingw %d\n",x,i); } void readpipe( char* expect, int len) { char buf[1024]; int i=0; printf("%sreading\n",x); while(i==0) { //printf("."); i = fread(buf,1,len,rh); } printf("%sread (%d) %s\n",x,i,buf); } void writepipe( char* data, int len) { int i,j; printf("%swriting\n",x); i = fwrite(data,1,len,rh); j = fflush(rh); //No help! printf("%sflush %d\n",x,j); printf("%swrite (%d) %s\n",x,i,data); } int main(int argc, char **argv) { rpipe = "readfifo"; wpipe = "writefifo"; x = ""; pid = fork(); if( pid == 0) { wpipe = "readfifo"; rpipe = "writefifo"; x = " "; openrpipe(); openwpipe(); writepipe("paul",4); readpipe("was",3); writepipe("here",4); closerpipe(); closewpipe(); exit(0); } openrpipe(); openwpipe(); readpipe("paul",4); writepipe("was",3); readpipe("here",4); closerpipe(); closewpipe(); return( -1 ); } BTW: To use the testocd above you need to pipes in the cwd: mkfifo ./readfifo mkfifo ./writefifo

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