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• optimize output value using a class and public member

  - by wiso

  Suppose you have a function, and you call it a lot of times, every time the function return a big object. I've optimized the problem using a functor that return void, and store the returning value in a public member: #include <vector> const int N = 100; std::vector<double> fun(const std::vector<double> & v, const int n) { std::vector<double> output = v; output[n] *= output[n]; return output; } class F { public: F() : output(N) {}; std::vector<double> output; void operator()(const std::vector<double> & v, const int n) { output = v; output[n] *= n; } }; int main() { std::vector<double> start(N,10.); std::vector<double> end(N); double a; // first solution for (unsigned long int i = 0; i != 10000000; ++i) a = fun(start, 2)[3]; // second solution F f; for (unsigned long int i = 0; i != 10000000; ++i) { f(start, 2); a = f.output[3]; } } Yes, I can use inline or optimize in an other way this problem, but here I want to stress on this problem: with the functor I declare and construct the output variable output only one time, using the function I do that every time it is called. The second solution is two time faster than the first with g++ -O1 or g++ -O2. What do you think about it, is it an ugly optimization?

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• PHP/mysqli: Inserting IP address with mysqli_stmt_bind_param()

  - by invarbrass

  Hello! I have a database table which contains an unsigned integer field to store the visitor's IP address: `user_ip` INT(10) UNSIGNED DEFAULT NULL, Here's the snippet of PHP code which tries to store the IP address: $ipaddr = $_SERVER['REMOTE_ADDR']; if ($stmt = mysqli_prepare($dbconn, 'INSERT INTO visitors(user_email, user_ip) VALUES (?,?)')) { $remote_ip = "INET_ATON('$ipaddr')"; mysqli_stmt_bind_param($stmt, 'ss', $email, $remote_ip); if (mysqli_stmt_execute($stmt) === FALSE) return FALSE; $rows_affected = mysqli_stmt_affected_rows($stmt); mysqli_stmt_close($stmt); } The INSERT operation succeeds, however the user_ip field contains a null value. I have also tried changing the parameter type in mysqli_stmt_bind_param() (which was set to string in the above example) to integer, i.e. mysqli_bind_param(... 'si',...) - but to no avail. I've also tried using the following bit of code instead of mysql's INET_ATON() SQL function: function IP_ATON($ipaddr) { $trio = intval(substr($ipaddr,0,3)); return ($trio>127) ? ((ip2long($ipaddr) & 0x7FFFFFFF) + 0x80000000) : ip2long($ipaddr); } It still doesn't work - the 'user_ip' field is still set to null. I've tried passing the $ip_addr variable as both integer & string in mysqli_bind_param() - to no avail. It seems the problem lies with the parameterized insert. The following "old-style" code works without any problem: mysqli_query(..., "INSERT INTO visitors(user_email, user_ip) VALUES ('$email',INET_ATON('$ipaddr'))"); What am I doing wrong here? Thanks in advance!

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• Mysql - Help me alter this query to apply AND logic instead of OR in searching?

  - by sandeepan-nath

  First execute these tables and data dumps :- CREATE TABLE IF NOT EXISTS `Tags` ( `id_tag` int(10) unsigned NOT NULL auto_increment, `tag` varchar(255) default NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=18 ; INSERT INTO `Tags` (`id_tag`, `tag`) VALUES (1, 'key1'), (2, 'key2'); CREATE TABLE IF NOT EXISTS `Tutors_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_tutor` int(10) default NULL, KEY `Tutors_Tag_Relations` (`id_tag`), KEY `id_tutor` (`id_tutor`), KEY `id_tag` (`id_tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Tutors_Tag_Relations` (`id_tag`, `id_tutor`) VALUES (1, 1), (2, 1); The following query finds all the tutors from Tutors_Tag_Relations table which have reference to at least one of the terms "key1" or "key2". SELECT td . * FROM Tutors_Tag_Relations AS td INNER JOIN Tags AS t ON t.id_tag = td.id_tag WHERE t.tag LIKE "%key1%" OR t.tag LIKE "%key2%" Group by td.id_tutor LIMIT 10 Please help me modify this query so that it returns all the tutors from Tutors_Tag_Relations table which have reference to both the terms "key1" and "key2" (AND logic instead of OR logic). Please suggest an optimized query considering huge number of data records (the query should NOT individually fetch two sets of tutors matching each keyword and then find the intersection).

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• Complex sorting on MySQL database

  - by ChrisR

  I'm facing the following situation. We've got an CMS with an entity with translations. These translations are stored in a different table with a one-to-many relationship. For example newsarticles and newsarticle_translations. The amount of available languages is dynamically determined by the same CMS. When entering a new newsarticle the editor is required to enter at least one translation, which one of the available languages he chooses is up to him. In the newsarticle overview in our CMS we would like to show a column with the (translated) article title, but since none of the languages are mandatory (one of them is mandatory but i don't know which one) i don't really know how to construct my mysql query to select a title for each newsarticle, regardless of the entered language. And to make it all a little harder, our manager asked for the possibilty to also be able to sort on title, so fetching the translations in a separate query is ruled out as far as i know. Anyone has an idea on how to solve this in the most efficient way? Here are my table schema's it it might help > desc news; +-----------------+----------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+----------------+------+-----+-------------------+----------------+ | id | int(10) | NO | PRI | NULL | auto_increment | | category_id | int(1) | YES | | NULL | | | created | timestamp | NO | | CURRENT_TIMESTAMP | | | user_id | int(10) | YES | | NULL | | +-----------------+----------------+------+-----+-------------------+----------------+ > desc news_translations; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | enabled | tinyint(1) | NO | | 0 | | | news_id | int(1) unsigned | NO | | NULL | | | title | varchar(255) | NO | | | | | summary | text | YES | | NULL | | | body | text | NO | | NULL | | | language | varchar(2) | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ PS: i've though about subqueries and coalesce() solutions but those seem rather dirty tricks, wondering if something better is know that i'm not thinking of?

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• Array's index and argc signedness

  - by tusbar

  Hello, The C standard (5.1.2.2.1 Program startup) says: The function called at program startup is named main. [...] It shall be de?ned with a return type of int and with no parameters: int main(void) { /* ... */ } or with two parameters [...] : int main(int argc, char *argv[]) { /* ... */ } And later says: The value of argc shall be nonnegative. Why shouldn't argc be defined as an unsigned int, argc supposedly meaning 'argument count'? Should argc be used as an index for argv? So I started wondering if the C standard says something about the type of array's index. Is it signed? 6.5.2.1 Array subscripting: One of the expressions shall have type ‘‘pointer to object type’’, the other expression shall have integer type, and the result has type ‘‘type’’. It doesn't say anything about its signedness (or I didn't find it). It is pretty common to see codes using negatives array indexes (array[-1]) but isn't it undefined behavior? Should array's indexes be unsigned?

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• Measuring the CPU frequency scaling effect

  - by Bryan Fok

  Recently I am trying to measure the effect of the cpu scaling. Is it accurate if I use this clock to measure it? template<std::intmax_t clock_freq> struct rdtsc_clock { typedef unsigned long long rep; typedef std::ratio<1, clock_freq> period; typedef std::chrono::duration<rep, period> duration; typedef std::chrono::time_point<rdtsc_clock> time_point; static const bool is_steady = true; static time_point now() noexcept { unsigned lo, hi; asm volatile("rdtsc" : "=a" (lo), "=d" (hi)); return time_point(duration(static_cast<rep>(hi) << 32 | lo)); } }; Update: According to the comment from my another post, I believe redtsc cannot use for measure the effect of cpu frequency scaling because the counter from the redtsc does not affected by the CPU frequency, am i right?

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• Has anyone ever successfully make index merge work for MySQL?

  - by user198729

  Setup: mysql> create table t(a integer unsigned,b integer unsigned); mysql> insert into t(a,b) values (1,2),(1,3),(2,4); mysql> create index i_t_a on t(a); mysql> create index i_t_b on t(b); mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 3 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Is there something I'm missing? Update mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 1863 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Version: mysql> select version(); +----------------------+ | version() | +----------------------+ | 5.1.36-community-log | +----------------------+ Has anyone ever successfully make index merge work for MySQL? I'll be glad to see successful stories here:)

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• C++ ulong to class method pointer and back

  - by Simone Margaritelli

  Hi guys, I'm using a hash table (source code by Google Inc) to store some method pointers defined as: typedef Object *(Executor::*expression_delegate_t)( vframe_t *, Node * ); Where obviously "Executor" is the class. The function prototype to insert some value to the hash table is: hash_item_t *ht_insert( hash_table_t *ht, ulong key, ulong data ); So basically i'm doing the insert double casting the method pointer: ht_insert( table, ASSIGN, reinterpret_cast<ulong>( (void *)&Executor::onAssign ) ); Where table is defined as a 'hash_table_t *' inside the declaration of the Executor class, ASSIGN is an unsigned long value, and 'onAssign' is the method I have to map. Now, Executor::onAssign is stored as an unsigned long value, its address in memory I think, and I need to cast back the ulong to a method pointer. But this code: hash_item_t* item = ht_find( table, ASSIGN ); expression_delegate_t delegate = reinterpret_cast < expression_delegate_t > (item->data); Gives me the following compilation error : src/executor.cpp:45: error: invalid cast from type ‘ulong’ to type ‘Object* (Executor::*)(vframe_t*, Node*)’ I'm using GCC v4.4.3 on a x86 GNU/Linux machine. Any hints?

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• MySQL: optimization of table (indexing, foreign key) with no primary keys

  - by Haradzieniec

  Each member has 0 or more orders. Each order contains at least 1 item. memberid - varchar, not integer - that's OK (please do not mention that's not very good, I can't change it). So, thera 3 tables: members, orders and order_items. Orders and order_items are below: CREATE TABLE `orders` ( `orderid` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT, `memberid` VARCHAR( 20 ), `Time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP , `info` VARCHAR( 3200 ) NULL , PRIMARY KEY (orderid) , FOREIGN KEY (memberid) REFERENCES members(memberid) ) ENGINE = InnoDB; CREATE TABLE `order_items` ( `orderid` INT(11) UNSIGNED NOT NULL, `item_number_in_cart` tinyint(1) NOT NULL , --- 5 items in cart= 5 rows `price` DECIMAL (6,2) NOT NULL, FOREIGN KEY (orderid) REFERENCES orders(orderid) ) ENGINE = InnoDB; So, order_items table looks like: orderid - item_number_in_cart - price: ... 1000456 - 1 - 24.99 1000456 - 2 - 39.99 1000456 - 3 - 4.99 1000456 - 4 - 17.97 1000457 - 1 - 20.00 1000458 - 1 - 99.99 1000459 - 1 - 2.99 1000459 - 2 - 69.99 1000460 - 1 - 4.99 ... As you see, order_items table has no primary keys (and I think there is no sense to create an auto_increment id for this table, because once we want to extract data, we always extract it as WHERE orderid='1000456' order by item_number_in_card asc - the whole block, id woudn't be helpful in queries). Once data is inserted into order_items, it's not UPDATEd, just SELECTed. The questions are: I think it's a good idea to put index on item_number_in_cart. Could anybody please confirm that? Is there anything else I have to do with order_items to increase the performance, or that looks pretty good? I could miss something because I'm a newbie. Thank you in advance.

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• MySQL Casting in C#

  - by user798080

  Okay, so I'm attempting to print out the contents of a table in a comma-separated file. using (OdbcCommand com = new OdbcCommand("SELECT * FROM pie_data WHERE Pie_ID = ?", con)) { com.Parameters.AddWithValue("", Request.Form["pie_id"]); com.ExecuteNonQuery(); using (OdbcDataReader reader = com.ExecuteReader()) { string finalstring = ""; while (reader.Read()) { finalstring = reader.GetString(9) + ","; for (int i = 0; i <= 8; i = i + 1) { finalstring = finalstring + reader.GetString(i) + ","; } } } Response.Write(finalstring); noredirect = 1; } My table layout is: CREATE TABLE `rent_data` ( `Pies` INT(10) UNSIGNED NOT NULL, `Name` VARCHAR(85) NOT NULL, `Email` VARCHAR(85) NOT NULL, `Pie_Rent` DATE NOT NULL, `Rent_To` DATE NOT NULL, `Returned_Date` DATE NULL DEFAULT NULL, `Place` VARCHAR(100) NOT NULL, `Purpose` MEDIUMTEXT NOT NULL, `Comments` MEDIUMTEXT NULL, `Pie_ID` SMALLINT(5) UNSIGNED ZEROFILL NOT NULL, INDEX `Pie_ID` (`Equipment_ID`) ) The error I'm getting is this: Exception Details: System.InvalidCastException: Unable to cast object of type 'System.Int64' to type 'System.String'. On the line: finalstring = finalstring + reader.GetString(i) + ",";

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• Locking a GDI+ Bitmap in Native C++?

  - by user146780

  I can find many examples on how to do this in managed c++ but none for unmanaged. I want to get all the pixel data as efficiently as possible, but some of the scan0 stuff I would need more info about so I can properly iterate through the pixel data and get each rgba value from it. right now I have this: Bitmap *b = new Bitmap(filename); if(b == NULL) { return 0; } UINT w,h; w = b->GetWidth(); h = b->GetHeight(); Rect *r = new Rect(0,0,w,h); BitmapData *lockdat; b->LockBits(r,ImageLockModeRead,PixelFormatDontCare,lockdat); delete(r); if(w == 0 && h == 0) { return 0; } Color c; std::vector<GLubyte> pdata(w * h * 4,0.0); for (unsigned int i = 0; i < h; i++) { for (unsigned int j = 0; j < w; j++) { b->GetPixel(j,i,&c); pdata[i * 4 * w + j * 4 + 0] = (GLubyte) c.GetR(); pdata[i * 4 * w + j * 4 + 1] = (GLubyte) c.GetG(); pdata[i * 4 * w + j * 4 + 2] = (GLubyte) c.GetB(); pdata[i * 4 * w + j * 4 + 3] = (GLubyte) c.GetA(); } } delete(b); return CreateTexture(pdata,w,h); How do I use lockdat to do the equivalent of getpixel? Thanks

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• How to properly cast a global memory array using the uint4 vector in CUDA to increase memory throughput?

  - by charis

  There are generally two techniques to increase the memory throughput of the global memory on a CUDA kernel; memory accesses coalescence and accessing words of at least 4 bytes. With the first technique accesses to the same memory segment by threads of the same half-warp are coalesced to fewer transactions while be accessing words of at least 4 bytes this memory segment is effectively increased from 32 bytes to 128. To access 16-byte instead of 1-byte words when there are unsigned chars stored in the global memory, the uint4 vector is commonly used by casting the memory array to uint4: uint4 *text4 = ( uint4 * ) d_text; var = text4[i]; In order to extract the 16 chars from var, i am currently using bitwise operations. For example: s_array[j * 16 + 0] = var.x & 0x000000FF; s_array[j * 16 + 1] = (var.x >> 8) & 0x000000FF; s_array[j * 16 + 2] = (var.x >> 16) & 0x000000FF; s_array[j * 16 + 3] = (var.x >> 24) & 0x000000FF; My question is, is it possible to recast var (or for that matter *text4) to unsigned char in order to avoid the additional overhead of the bitwise operations?

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• Why is joining two vectors simply not working?

  - by Jim

  I have two vectors of MyObj structs. MyObj is defined as follows: struct MyObj { float x, y; unsigned int data[8]; unsigned int tmp[1]; MyObj(const MyObj &m) { x = m.x; y = m.y; tmp[0] = 0; for (int i = 0; i < 8; ++i) { data[i] = m.data[i]; } } }; I then have two vectors... vector<MyObj> v1; vector<MyObj> v2; // both get data eventually. v1.insert(v1.end(), v2.begin(), v2.end()); v2 has 3535004 elements in my experiment. v1 is similarly sized. I've also tried building a new vector and just using .push_back to build it from both vectors. Essentially, when I try to merge the two vectors I just get an error from visual studio saying "Debug error! R6010, abort() has been called". Very non-useful... So my question is: what could be causing this error, and how can I solve it? Thank you

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• Connector/C++ compile error

  - by rizzo0917

  When I compile code that includes Connector/C++ headers, I get the following errors: c:\qt\2010.03\mingw\bin../lib/gcc/mingw32/4.4.0/../../../../include/stdint.h:27: error: 'int8_t' has a previous declaration as 'typedef signed char int8_t' c:\qt\2010.03\mingw\bin../lib/gcc/mingw32/4.4.0/../../../../include/stdint.h:31: error: 'int32_t' has a previous declaration as 'typedef int int32_t' c:\qt\2010.03\mingw\bin../lib/gcc/mingw32/4.4.0/../../../../include/stdint.h:32: error: 'uint32_t' has a previous declaration as 'typedef unsigned int uint32_t' Literally all I do is this: #include <cppconn/driver.h> #include <cppconn/exception.h> #include <cppconn/resultset.h> #include <cppconn/statement.h> #include <cppconn/prepared_statement.h> Now I can go into the file and comment the lines out that give me errors: //typedef signed char int8_t; //typedef int int32_t; //typedef unsigned uint32_t; It compiles, but when I try to run the mysql code: sql::Driver *driver; driver = get_driver_instance(); I get this output test.exe exited with code -1073741515 Any Ideas?

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• multiple mysql_real_query() in while loop

  - by Steve

  It seems that when I have one mysql_real_query() function in a continuous while loop, the query will get executed OK. However, if multiple mysql_real_query() are inside the while loop, one right after the other. Depending on the query, sometimes neither the first query nor second query will execute properly. This seems like a threading issue to me. I'm wondering if the mysql c api has a way of dealing with this? Does anyone know how to deal with this? mysql_free_result() doesn't work since I am not even storing the results. //keep polling as long as stop character '-' is not read while(szRxChar != '-') { // Check if a read is outstanding if (HasOverlappedIoCompleted(&ovRead)) { // Issue a serial port read if (!ReadFile(hSerial,&szRxChar,1, &dwBytesRead,&ovRead)) { DWORD dwErr = GetLastError(); if (dwErr!=ERROR_IO_PENDING) return dwErr; } } // Wait 5 seconds for serial input if (!(HasOverlappedIoCompleted(&ovRead))) { WaitForSingleObject(hReadEvent,RESET_TIME); } // Check if serial input has arrived if (GetOverlappedResult(hSerial,&ovRead, &dwBytesRead,FALSE)) { // Wait for the write GetOverlappedResult(hSerial,&ovWrite, &dwBytesWritten,TRUE); //load tagBuffer with byte stream tagBuffer[i] = szRxChar; i++; tagBuffer[i] = 0; //char arrays are \0 terminated //run query with tagBuffer if( strlen(tagBuffer)==PACKET_LENGTH ) { sprintf(query,"insert into scan (rfidnum) values ('"); strcat(query, tagBuffer); strcat(query, "')"); mysql_real_query(&mysql,query,(unsigned int)strlen(query)); i=0; } mysql_real_query(&mysql,"insert into scan (rfidnum) values ('2nd query')",(unsigned int)strlen("insert into scan (rfid) values ('2nd query')")); mysql_free_result(res); } }

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• Simple OpenCL Kernel

  - by Yuuta

  I'm trying to write a kernel which is a little long but the output is not correct. I took out a lot almost everything and finally narrowed down the an initialization problem and I found that the following works: __kernel void k_sIntegral(__global const float* eData,__global const unsigned long* elements,__global float* area){ const int i = get_global_id(0); if(i < elements[0]){ area[i] = i; } } But the following does not work: __kernel void k_sIntegral(__global const float* eData,__global const unsigned long* elements,__global float* area){ const int i = get_global_id(0); if(i < elements[0]){ __local float a,b,c,j,k,h,s; area[i] = i; } } Using the first kernel, I get: area[1] = 1 Using the second kernel, I get: area[1] = 0 (from calloc) Update: It seems like the code does work, but I need to change the function name otherwise it somehow calls the previous function even though it was not compiled (?). Any leads to why that happens? If anyone can let me know what might be the problem I'll be really grateful, thanks in advance!

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• Optimal (Time paradigm) solution to check variable within boundary

  - by kumar_m_kiran

  Hi All, Sorry if the question is very naive. I will have to check the below condition in my code 0 < x < y i.e code similar to if(x > 0 && x < y) The basic problem at system level is - currently, for every call (Telecom domain terminology), my existing code is hit (many times). So performance is very very critical, Now, I need to add a check for boundary checking (at many location - but different boundary comparison at each location). At very normal level of coding, the above comparison would look very naive without any issue. However, when added over my statistics module (which is dipped many times), performance will go down. So I would like to know the best possible way to handle the above scenario (kind of optimal way for limits checking technique). Like for example, if bit comparison works better than normal comparison or can both the comparison be evaluation in shorter time span? Other Info x is unsigned integer (which must be checked to be greater than 0 and less than y). y is unsigned integer. y is a non-const and varies for every comparison. Here time is the constraint compared to space. Language - C++. Now, later if I need to change the attribute of y to a float/double, would there be another way to optimize the check (i.e will the suggested optimal technique for integer become non-optimal solution when y is changed to float/double). Thanks in advance for any input. PS : OS used is SUSE 10 64 bit x64_64, AIX 5.3 64 bit, HP UX 11.1 A 64.

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• What would the destructor for this class look like?

  - by cam

  class Equipment { std::vector<Armor*> vEquip; Weapon* mainWeapon; int totalDefense; int totalAttack; public: unsigned int GetWeight(); int * GetDefense(); bool EquipArmor(Armor* armor); bool UnequipArmor(Armor* armor); bool EquipWeapon(Weapon* wep); bool UnequipWeapon(Weapon* wep); Equipment(); virtual ~Equipment(); }; It seems like there should be no destructor. The vector of pointers will take care of itself when it goes out of scope, and the actual objects the pointers point to don't need to be deleted as there will be other references to it. All of the objects in this refer to the main Container: class Container { int weightLimit; unsigned int currWeight; std::vector<Item*> vItems; public: bool AddItem(Item* item); bool RemoveItem(Item* item); Container(); Container(int weightLim); Container(int weightLim, std::vector<Item*> items); ~Container(); }; Now here I can see it being necessary to delete all objects in the container, because this is where all the objects are assigned via AddItem(new Item("Blah")) (Armor and Weapon inherit from Item)

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• Rotating bits of any integer in C

  - by Tim

  Pass a integer 2 to this function and then return a integer which is 4 x = 2; x = rotateInt('L', x, 1); (left shift the bits by 1) Example: 00000010 - rotate left by 1 - 00000100 but if I pass this: x = rotateInt('R', x, 3); it will return 64, 01000000 Here is the code, can someone correct the error... thanks int rotateInt(char direction, unsigned int x, int y) { unsigned int mask = 0; int num = 0, result = 0; int i; for(i = 0; i < y; i++) { if(direction == 'R') { if((x & 1) == 1) x = (x ^ 129); else x = x >> 1; } else if(direction == 'L') { if((x & 128) == 1) x = (x ^ 129); else x = x << 1; } } result = (result ^ x); return result; }

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• Assigning address to array from heap

  - by Schaltfehler

  I want to save the state of my structs as a binary file and load them again. My structs look like this: typedef struct { uint8_t pointerLength; uint8_t *pointer; uint8_t NumBla; uinT16 Bla[MAX_NUM_Bla]; ... } BAR_STRUCT, *BAR; typedef struct { int numBar; BAR bars[MAX_NUM_BAR]; } FOO_STRUCT, *FOO; Saving is no problem, but restoring the state. Iam at the point where the bytestring from the file is on the heap and a pointer is pointing to the first adress of this string. And I do as follows: const void* dataPointer //points to adress in heap unsigned char* bytePointer = (unsigned char*)dataPointer; FOO foo = (FOO_STRUCT*)bytePointer; bytePointer += sizeof(FOO_STRUCT); for (int i=0; i < MAX_NUM_BAR; i++) { foo->bars[i] = (BAR_STRUCT*)bytePointer; } The last assignment doesn't work and I get an EXC_BAD_ACCESS. Because bars is an array of pointers i need to correct the adresses of each element is pointing to. Because they are not valid anymore. So I try to assign the adress of the object I saved in the bytesteam to foo-bars[i]; But I can not change foo-bars[i] at all. Accessing works but but assigning a new adress doesn't. I wonder why.

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• Why is it 8 here,understanding buffer overflow

  - by Mask

  void function(int a, int b, int c) { char buffer1[5]; char buffer2[10]; int *ret; ret = buffer1 + 12; (*ret) += 8;//why is it 8?? } void main() { int x; x = 0; function(1,2,3); x = 1; printf("%d\n",x); } The above demo is from here: http://insecure.org/stf/smashstack.html But it's not working here: D:\test>gcc -Wall -Wextra hw.cpp && a.exe hw.cpp: In function `void function(int, int, int)': hw.cpp:6: warning: unused variable 'buffer2' hw.cpp: At global scope: hw.cpp:4: warning: unused parameter 'a' hw.cpp:4: warning: unused parameter 'b' hw.cpp:4: warning: unused parameter 'c' 1 And I don't understand why it's 8 though the author thinks: A little math tells us the distance is 8 bytes.

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• How can I use Boost::regex.hpp library in C++?

  - by MIH1406

  I tried to use Boost library but I failed, see my code: #include "listy.h" #include <boost/regex.hpp> using namespace boost; ListyCheck::ListyCheck() { } ListyCheck::~ListyCheck() { } bool ListyCheck::isValidItem(std::string &__item) { regex e("(\\d{4}[- ]){3}\\d{4}"); return regex_match(__item, e); } When I tried to compile it I get those messages: /usr/include/boost/regex/v4/regex_match.hpp:50: undefined reference to `boost::re_detail::perl_matcher<__gnu_cxx::__normal_iterator, std::allocator , std::allocator, std::allocator , boost::regex_traits ::match()' /usr/include/boost/regex/v4/basic_regex.hpp:425: undefined reference to `boost::basic_regex ::do_assign(char const*, char const*, unsigned int)' /usr/include/boost/regex/v4/perl_matcher.hpp:366: undefined reference to `boost::re_detail::perl_matcher<__gnu_cxx::__normal_iterator, std::allocator , std::allocator, std::allocator , boost::regex_traits ::construct_init(boost::basic_regex const&, boost::regex_constants::_match_flags)' etc...

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• How do I parse JSON from a Java HTTPResponse?

  - by Joe Ludwig

  I have an HttpResponse object for a web request I just made. The response is in the JSON format, so I need to parse it. I can do it in an absurdly complex way, but it seems like there must be a better way. Is this really the best I can do? HttpResponse response; // some response object Reader in = new BufferedReader( new InputStreamReader(response.getEntity().getContent(), "UTF-8")); StringBuilder builder= new StringBuilder(); char[] buf = new char[1000]; int l = 0; while (l >= 0) { builder.append(buf, 0, l); l = in.read(buf); } JSONTokener tokener = new JSONTokener( builder.toString() ); JSONArray finalResult = new JSONArray( tokener ); I'm on Android if that makes any difference.

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• C++ Preprocessor string literal concatenation

  - by ezpz

  I found this regarding how the C preprocessor should handle string literal concatenation (phase 6). However, I can not find anything regarding how this is handled in C++ (does C++ use the C preprocessor?). The reason I ask is that I have the following: const char * Foo::encoding = "\0" "1234567890\0abcdefg"; where encoding is a static member of class Foo. Without the availability of concatenation I wouldnt be able to write that sequence of characters like that. const char * Foo::encoding = "\01234567890\0abcdefg"; Is something entirely different due to the way \012 is interpreted. I dont have access to multiple platforms and I'm curious how confident I should be that the above is always handled correctly - i.e. I will always get { 0, '1', '2', '3', ... }

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• why am i getting error in this switch statement written in c

  - by mekasperasky

  I have a character array b which stores different identifiers in different iterations . I have to compare b with various identifiers of the programming language C and print it into a file . When i do it using the following switch statement it gives me errors b[i]='\0'; switch(b[i]) { case "if":fprintf(fp2,"if ----> IDENTIFIER \n"); case "then":fprintf(fp2,"then ----> IDENTIFIER \n"); case "else":fprintf(fp2,"else ----> IDENTIFIER \n"); case "switch":fprintf(fp2,"switch ----> IDENTIFIER \n"); case 'printf':fprintf(fp2,"prtintf ----> IDENTIFIER \n"); case 'scanf':fprintf(fp2,"else ----> IDENTIFIER \n"); case 'NULL':fprintf(fp2,"NULL ----> IDENTIFIER \n"); case 'int':fprintf(fp2,"INT ----> IDENTIFIER \n"); case 'char':fprintf(fp2,"char ----> IDENTIFIER \n"); case 'float':fprintf(fp2,"float ----> IDENTIFIER \n"); case 'long':fprintf(fp2,"long ----> IDENTIFIER \n"); case 'double':fprintf(fp2,"double ----> IDENTIFIER \n"); case 'char':fprintf(fp2,"char ----> IDENTIFIER \n"); case 'const':fprintf(fp2,"const ----> IDENTIFIER \n"); case 'continue':fprintf(fp2,"continue ----> IDENTIFIER \n"); case 'break':fprintf(fp2,"long ----> IDENTIFIER \n"); case 'for':fprintf(fp2,"long ----> IDENTIFIER \n"); case 'size of':fprintf(fp2,"size of ----> IDENTIFIER \n"); case 'register':fprintf(fp2,"register ----> IDENTIFIER \n"); case 'short':fprintf(fp2,"short ----> IDENTIFIER \n"); case 'auto':fprintf(fp2,"auto ----> IDENTIFIER \n"); case 'while':fprintf(fp2,"while ----> IDENTIFIER \n"); case 'do':fprintf(fp2,"do ----> IDENTIFIER \n"); case 'case':fprintf(fp2,"case ----> IDENTIFIER \n"); } the error being lex.c:94:13: warning: character constant too long for its type lex.c:95:13: warning: character constant too long for its type lex.c:96:13: warning: multi-character character constant lex.c:97:13: warning: multi-character character constant lex.c:98:13: warning: multi-character character constant lex.c:99:13: warning: character constant too long for its type lex.c:100:13: warning: multi-character character constant lex.c:101:13: warning: character constant too long for its type lex.c:102:13: warning: multi-character character constant lex.c:103:13: warning: character constant too long for its type lex.c:104:13: warning: character constant too long for its type lex.c:105:13: warning: character constant too long for its type lex.c:106:13: warning: multi-character character constant lex.c:107:13: warning: character constant too long for its type lex.c:108:13: warning: character constant too long for its type lex.c:109:13: warning: character constant too long for its type lex.c:110:12: warning: multi-character character constant lex.c:111:13: warning: character constant too long for its type lex.c:112:13: warning: multi-character character constant lex.c:113:13: warning: multi-character character constant lex.c: In function ‘int main()’: lex.c:90: error: case label does not reduce to an integer constant lex.c:91: error: case label does not reduce to an integer constant lex.c:92: error: case label does not reduce to an integer constant lex.c:93: error: case label does not reduce to an integer constant lex.c:94: warning: overflow in implicit constant conversion lex.c:95: warning: overflow in implicit constant conversion lex.c:95: error: duplicate case value lex.c:94: error: previously used here lex.c:96: warning: overflow in implicit constant conversion lex.c:97: warning: overflow in implicit constant conversion lex.c:98: warning: overflow in implicit constant conversion lex.c:99: warning: overflow in implicit constant conversion lex.c:99: error: duplicate case value lex.c:97: error: previously used here lex.c:100: warning: overflow in implicit constant conversion lex.c:101: warning: overflow in implicit constant conversion lex.c:102: warning: overflow in implicit constant conversion lex.c:102: error: duplicate case value lex.c:98: error: previously used here lex.c:103: warning: overflow in implicit constant conversion lex.c:103: error: duplicate case value lex.c:97: error: previously used here lex.c:104: warning: overflow in implicit constant conversion lex.c:104: error: duplicate case value lex.c:101: error: previously used here lex.c:105: warning: overflow in implicit constant conversion lex.c:106: warning: overflow in implicit constant conversion lex.c:106: error: duplicate case value lex.c:98: error: previously used here lex.c:107: warning: overflow in implicit constant conversion lex.c:107: error: duplicate case value lex.c:94: error: previously used here lex.c:108: warning: overflow in implicit constant conversion lex.c:108: error: duplicate case value lex.c:98: error: previously used here lex.c:109: warning: overflow in implicit constant conversion lex.c:109: error: duplicate case value lex.c:97: error: previously used here lex.c:110: warning: overflow in implicit constant conversion lex.c:111: warning: overflow in implicit constant conversion lex.c:111: error: duplicate case value lex.c:101: error: previously used here lex.c:112: warning: overflow in implicit constant conversion lex.c:112: error: duplicate case value lex.c:110: error: previously used here lex.c:113: warning: overflow in implicit constant conversion lex.c:113: error: duplicate case value lex.c:101: error: previously used here

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