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  • The SVG text node disappear after change its text content

    - by sureone
    svg: <text xml:space="preserve" y="228" x="349.98" text-anchor="middle" stroke-width="0" stroke-linejoin="null" stroke-linecap="null" stroke-dasharray="null" stroke="#000000" fill="#000000" style="cursor: move; pointer-events: inherit;" font-size="24" font-family="serif" id="cur_b">cur_b</text> <text xml:space="preserve" y="222" x="103.98" text-anchor="middle" stroke-width="0" stroke-linejoin="null" stroke-linecap="null" stroke-dasharray="null" stroke="#000000" fill="#000000" style="cursor: move; pointer-events: inherit;" font-size="24" font-family="serif" id="cur_a">cur_a</text> <text xml:space="preserve" y="229" x="590.0211" text-anchor="middle" stroke-width="0" stroke-linejoin="null" stroke-linecap="null" stroke-dasharray="null" stroke="#000000" fill="#000000" style="cursor: move; pointer-events: inherit;" font-size="24" font-family="serif" id="cur_c">cur_c</text> NSString* theJS = @ "var theNode0 = document.getElementById('cur_a'); theNode0.textContent='200A'; theNode0.setAttribute('fill','#FF0000'); var theNode1 = document.getElementById('cur_c'); theNode1.textContent='200A'; theNode1.setAttribute('fill','#00FF00');" [self.webView stringByEvaluatingJavaScriptFromString:theJS]; The SVG text node value is changed but disappeared after about one second.

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  • Proper way to reassign pointers in c++

    - by user272689
    I want to make sure i have these basic ideas correct before moving on (I am coming from a Java/Python background). I have been searching the net, but haven't found a concrete answer to this question yet. When you reassign a pointer to a new object, do you have to call delete on the old object first to avoid a memory leak? My intuition is telling me yes, but i want a concrete answer before moving on. For example, let say you had a class that stored a pointer to a string class MyClass { private: std::string *str; public: MyClass (const std::string &_str) { str=new std::string(_str); } void ChangeString(const std::string &_str) { // I am wondering if this is correct? delete str; str = new std::string(_str) /* * or could you simply do it like: * str = _str; */ } .... In the ChangeString method, which would be correct? I think i am getting hung up on if you dont use the new keyword for the second way, it will still compile and run like you expected. Does this just overwrite the data that this pointer points to? Or does it do something else? Any advice would be greatly appricated :D

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  • static_cast from Derived* to void* to Base*

    - by Roberto
    I would like to cast a pointer to a member of a derived class to void* and from there to a pointer of the base class, like in the example below: #include <iostream> class Base { public: void function1(){std::cout<<"1"<<std::endl;} virtual void function2()=0; }; class Derived : public Base { public: virtual void function2(){std::cout<<"2"<<std::endl;} }; int main() { Derived d; void ptr* = static_cast<void*>(&d); Base* baseptr=static_cast<Base*>(ptr); baseptr->function1(); baseptr->function2(); } This compiles and gives the desired result (prints 1 and 2 respectively), but is it guaranteed to work? The description of static_cast I found here: http://en.cppreference.com/w/cpp/language/static_cast only mentions conversion to void* and back to a pointer to the same class (point 10).

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  • Advanced TSQL Tuning: Why Internals Knowledge Matters

    - by Paul White
    There is much more to query tuning than reducing logical reads and adding covering nonclustered indexes.  Query tuning is not complete as soon as the query returns results quickly in the development or test environments.  In production, your query will compete for memory, CPU, locks, I/O and other resources on the server.  Today’s entry looks at some tuning considerations that are often overlooked, and shows how deep internals knowledge can help you write better TSQL. As always, we’ll need some example data.  In fact, we are going to use three tables today, each of which is structured like this: Each table has 50,000 rows made up of an INTEGER id column and a padding column containing 3,999 characters in every row.  The only difference between the three tables is in the type of the padding column: the first table uses CHAR(3999), the second uses VARCHAR(MAX), and the third uses the deprecated TEXT type.  A script to create a database with the three tables and load the sample data follows: USE master; GO IF DB_ID('SortTest') IS NOT NULL DROP DATABASE SortTest; GO CREATE DATABASE SortTest COLLATE LATIN1_GENERAL_BIN; GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest', SIZE = 3GB, MAXSIZE = 3GB ); GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest_log', SIZE = 256MB, MAXSIZE = 1GB, FILEGROWTH = 128MB ); GO ALTER DATABASE SortTest SET ALLOW_SNAPSHOT_ISOLATION OFF ; ALTER DATABASE SortTest SET AUTO_CLOSE OFF ; ALTER DATABASE SortTest SET AUTO_CREATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_SHRINK OFF ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS_ASYNC ON ; ALTER DATABASE SortTest SET PARAMETERIZATION SIMPLE ; ALTER DATABASE SortTest SET READ_COMMITTED_SNAPSHOT OFF ; ALTER DATABASE SortTest SET MULTI_USER ; ALTER DATABASE SortTest SET RECOVERY SIMPLE ; USE SortTest; GO CREATE TABLE dbo.TestCHAR ( id INTEGER IDENTITY (1,1) NOT NULL, padding CHAR(3999) NOT NULL,   CONSTRAINT [PK dbo.TestCHAR (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestMAX ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAX (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestTEXT ( id INTEGER IDENTITY (1,1) NOT NULL, padding TEXT NOT NULL,   CONSTRAINT [PK dbo.TestTEXT (id)] PRIMARY KEY CLUSTERED (id), ) ; -- ============= -- Load TestCHAR (about 3s) -- ============= INSERT INTO dbo.TestCHAR WITH (TABLOCKX) ( padding ) SELECT padding = REPLICATE(CHAR(65 + (Data.n % 26)), 3999) FROM ( SELECT TOP (50000) n = ROW_NUMBER() OVER (ORDER BY (SELECT 0)) - 1 FROM master.sys.columns C1, master.sys.columns C2, master.sys.columns C3 ORDER BY n ASC ) AS Data ORDER BY Data.n ASC ; -- ============ -- Load TestMAX (about 3s) -- ============ INSERT INTO dbo.TestMAX WITH (TABLOCKX) ( padding ) SELECT CONVERT(VARCHAR(MAX), padding) FROM dbo.TestCHAR ORDER BY id ; -- ============= -- Load TestTEXT (about 5s) -- ============= INSERT INTO dbo.TestTEXT WITH (TABLOCKX) ( padding ) SELECT CONVERT(TEXT, padding) FROM dbo.TestCHAR ORDER BY id ; -- ========== -- Space used -- ========== -- EXECUTE sys.sp_spaceused @objname = 'dbo.TestCHAR'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAX'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestTEXT'; ; CHECKPOINT ; That takes around 15 seconds to run, and shows the space allocated to each table in its output: To illustrate the points I want to make today, the example task we are going to set ourselves is to return a random set of 150 rows from each table.  The basic shape of the test query is the same for each of the three test tables: SELECT TOP (150) T.id, T.padding FROM dbo.Test AS T ORDER BY NEWID() OPTION (MAXDOP 1) ; Test 1 – CHAR(3999) Running the template query shown above using the TestCHAR table as the target, we find that the query takes around 5 seconds to return its results.  This seems slow, considering that the table only has 50,000 rows.  Working on the assumption that generating a GUID for each row is a CPU-intensive operation, we might try enabling parallelism to see if that speeds up the response time.  Running the query again (but without the MAXDOP 1 hint) on a machine with eight logical processors, the query now takes 10 seconds to execute – twice as long as when run serially. Rather than attempting further guesses at the cause of the slowness, let’s go back to serial execution and add some monitoring.  The script below monitors STATISTICS IO output and the amount of tempdb used by the test query.  We will also run a Profiler trace to capture any warnings generated during query execution. DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TC.id, TC.padding FROM dbo.TestCHAR AS TC ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; Let’s take a closer look at the statistics and query plan generated from this: Following the flow of the data from right to left, we see the expected 50,000 rows emerging from the Clustered Index Scan, with a total estimated size of around 191MB.  The Compute Scalar adds a column containing a random GUID (generated from the NEWID() function call) for each row.  With this extra column in place, the size of the data arriving at the Sort operator is estimated to be 192MB. Sort is a blocking operator – it has to examine all of the rows on its input before it can produce its first row of output (the last row received might sort first).  This characteristic means that Sort requires a memory grant – memory allocated for the query’s use by SQL Server just before execution starts.  In this case, the Sort is the only memory-consuming operator in the plan, so it has access to the full 243MB (248,696KB) of memory reserved by SQL Server for this query execution. Notice that the memory grant is significantly larger than the expected size of the data to be sorted.  SQL Server uses a number of techniques to speed up sorting, some of which sacrifice size for comparison speed.  Sorts typically require a very large number of comparisons, so this is usually a very effective optimization.  One of the drawbacks is that it is not possible to exactly predict the sort space needed, as it depends on the data itself.  SQL Server takes an educated guess based on data types, sizes, and the number of rows expected, but the algorithm is not perfect. In spite of the large memory grant, the Profiler trace shows a Sort Warning event (indicating that the sort ran out of memory), and the tempdb usage monitor shows that 195MB of tempdb space was used – all of that for system use.  The 195MB represents physical write activity on tempdb, because SQL Server strictly enforces memory grants – a query cannot ‘cheat’ and effectively gain extra memory by spilling to tempdb pages that reside in memory.  Anyway, the key point here is that it takes a while to write 195MB to disk, and this is the main reason that the query takes 5 seconds overall. If you are wondering why using parallelism made the problem worse, consider that eight threads of execution result in eight concurrent partial sorts, each receiving one eighth of the memory grant.  The eight sorts all spilled to tempdb, resulting in inefficiencies as the spilled sorts competed for disk resources.  More importantly, there are specific problems at the point where the eight partial results are combined, but I’ll cover that in a future post. CHAR(3999) Performance Summary: 5 seconds elapsed time 243MB memory grant 195MB tempdb usage 192MB estimated sort set 25,043 logical reads Sort Warning Test 2 – VARCHAR(MAX) We’ll now run exactly the same test (with the additional monitoring) on the table using a VARCHAR(MAX) padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TM.id, TM.padding FROM dbo.TestMAX AS TM ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query takes around 8 seconds to complete (3 seconds longer than Test 1).  Notice that the estimated row and data sizes are very slightly larger, and the overall memory grant has also increased very slightly to 245MB.  The most marked difference is in the amount of tempdb space used – this query wrote almost 391MB of sort run data to the physical tempdb file.  Don’t draw any general conclusions about VARCHAR(MAX) versus CHAR from this – I chose the length of the data specifically to expose this edge case.  In most cases, VARCHAR(MAX) performs very similarly to CHAR – I just wanted to make test 2 a bit more exciting. MAX Performance Summary: 8 seconds elapsed time 245MB memory grant 391MB tempdb usage 193MB estimated sort set 25,043 logical reads Sort warning Test 3 – TEXT The same test again, but using the deprecated TEXT data type for the padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TT.id, TT.padding FROM dbo.TestTEXT AS TT ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query runs in 500ms.  If you look at the metrics we have been checking so far, it’s not hard to understand why: TEXT Performance Summary: 0.5 seconds elapsed time 9MB memory grant 5MB tempdb usage 5MB estimated sort set 207 logical reads 596 LOB logical reads Sort warning SQL Server’s memory grant algorithm still underestimates the memory needed to perform the sorting operation, but the size of the data to sort is so much smaller (5MB versus 193MB previously) that the spilled sort doesn’t matter very much.  Why is the data size so much smaller?  The query still produces the correct results – including the large amount of data held in the padding column – so what magic is being performed here? TEXT versus MAX Storage The answer lies in how columns of the TEXT data type are stored.  By default, TEXT data is stored off-row in separate LOB pages – which explains why this is the first query we have seen that records LOB logical reads in its STATISTICS IO output.  You may recall from my last post that LOB data leaves an in-row pointer to the separate storage structure holding the LOB data. SQL Server can see that the full LOB value is not required by the query plan until results are returned, so instead of passing the full LOB value down the plan from the Clustered Index Scan, it passes the small in-row structure instead.  SQL Server estimates that each row coming from the scan will be 79 bytes long – 11 bytes for row overhead, 4 bytes for the integer id column, and 64 bytes for the LOB pointer (in fact the pointer is rather smaller – usually 16 bytes – but the details of that don’t really matter right now). OK, so this query is much more efficient because it is sorting a very much smaller data set – SQL Server delays retrieving the LOB data itself until after the Sort starts producing its 150 rows.  The question that normally arises at this point is: Why doesn’t SQL Server use the same trick when the padding column is defined as VARCHAR(MAX)? The answer is connected with the fact that if the actual size of the VARCHAR(MAX) data is 8000 bytes or less, it is usually stored in-row in exactly the same way as for a VARCHAR(8000) column – MAX data only moves off-row into LOB storage when it exceeds 8000 bytes.  The default behaviour of the TEXT type is to be stored off-row by default, unless the ‘text in row’ table option is set suitably and there is room on the page.  There is an analogous (but opposite) setting to control the storage of MAX data – the ‘large value types out of row’ table option.  By enabling this option for a table, MAX data will be stored off-row (in a LOB structure) instead of in-row.  SQL Server Books Online has good coverage of both options in the topic In Row Data. The MAXOOR Table The essential difference, then, is that MAX defaults to in-row storage, and TEXT defaults to off-row (LOB) storage.  You might be thinking that we could get the same benefits seen for the TEXT data type by storing the VARCHAR(MAX) values off row – so let’s look at that option now.  This script creates a fourth table, with the VARCHAR(MAX) data stored off-row in LOB pages: CREATE TABLE dbo.TestMAXOOR ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAXOOR (id)] PRIMARY KEY CLUSTERED (id), ) ; EXECUTE sys.sp_tableoption @TableNamePattern = N'dbo.TestMAXOOR', @OptionName = 'large value types out of row', @OptionValue = 'true' ; SELECT large_value_types_out_of_row FROM sys.tables WHERE [schema_id] = SCHEMA_ID(N'dbo') AND name = N'TestMAXOOR' ; INSERT INTO dbo.TestMAXOOR WITH (TABLOCKX) ( padding ) SELECT SPACE(0) FROM dbo.TestCHAR ORDER BY id ; UPDATE TM WITH (TABLOCK) SET padding.WRITE (TC.padding, NULL, NULL) FROM dbo.TestMAXOOR AS TM JOIN dbo.TestCHAR AS TC ON TC.id = TM.id ; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAXOOR' ; CHECKPOINT ; Test 4 – MAXOOR We can now re-run our test on the MAXOOR (MAX out of row) table: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) MO.id, MO.padding FROM dbo.TestMAXOOR AS MO ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; TEXT Performance Summary: 0.3 seconds elapsed time 245MB memory grant 0MB tempdb usage 193MB estimated sort set 207 logical reads 446 LOB logical reads No sort warning The query runs very quickly – slightly faster than Test 3, and without spilling the sort to tempdb (there is no sort warning in the trace, and the monitoring query shows zero tempdb usage by this query).  SQL Server is passing the in-row pointer structure down the plan and only looking up the LOB value on the output side of the sort. The Hidden Problem There is still a huge problem with this query though – it requires a 245MB memory grant.  No wonder the sort doesn’t spill to tempdb now – 245MB is about 20 times more memory than this query actually requires to sort 50,000 records containing LOB data pointers.  Notice that the estimated row and data sizes in the plan are the same as in test 2 (where the MAX data was stored in-row). The optimizer assumes that MAX data is stored in-row, regardless of the sp_tableoption setting ‘large value types out of row’.  Why?  Because this option is dynamic – changing it does not immediately force all MAX data in the table in-row or off-row, only when data is added or actually changed.  SQL Server does not keep statistics to show how much MAX or TEXT data is currently in-row, and how much is stored in LOB pages.  This is an annoying limitation, and one which I hope will be addressed in a future version of the product. So why should we worry about this?  Excessive memory grants reduce concurrency and may result in queries waiting on the RESOURCE_SEMAPHORE wait type while they wait for memory they do not need.  245MB is an awful lot of memory, especially on 32-bit versions where memory grants cannot use AWE-mapped memory.  Even on a 64-bit server with plenty of memory, do you really want a single query to consume 0.25GB of memory unnecessarily?  That’s 32,000 8KB pages that might be put to much better use. The Solution The answer is not to use the TEXT data type for the padding column.  That solution happens to have better performance characteristics for this specific query, but it still results in a spilled sort, and it is hard to recommend the use of a data type which is scheduled for removal.  I hope it is clear to you that the fundamental problem here is that SQL Server sorts the whole set arriving at a Sort operator.  Clearly, it is not efficient to sort the whole table in memory just to return 150 rows in a random order. The TEXT example was more efficient because it dramatically reduced the size of the set that needed to be sorted.  We can do the same thing by selecting 150 unique keys from the table at random (sorting by NEWID() for example) and only then retrieving the large padding column values for just the 150 rows we need.  The following script implements that idea for all four tables: SET STATISTICS IO ON ; WITH TestTable AS ( SELECT * FROM dbo.TestCHAR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id = ANY (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAX ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestTEXT ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAXOOR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; All four queries now return results in much less than a second, with memory grants between 6 and 12MB, and without spilling to tempdb.  The small remaining inefficiency is in reading the id column values from the clustered primary key index.  As a clustered index, it contains all the in-row data at its leaf.  The CHAR and VARCHAR(MAX) tables store the padding column in-row, so id values are separated by a 3999-character column, plus row overhead.  The TEXT and MAXOOR tables store the padding values off-row, so id values in the clustered index leaf are separated by the much-smaller off-row pointer structure.  This difference is reflected in the number of logical page reads performed by the four queries: Table 'TestCHAR' logical reads 25511 lob logical reads 000 Table 'TestMAX'. logical reads 25511 lob logical reads 000 Table 'TestTEXT' logical reads 00412 lob logical reads 597 Table 'TestMAXOOR' logical reads 00413 lob logical reads 446 We can increase the density of the id values by creating a separate nonclustered index on the id column only.  This is the same key as the clustered index, of course, but the nonclustered index will not include the rest of the in-row column data. CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestCHAR (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAX (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestTEXT (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAXOOR (id); The four queries can now use the very dense nonclustered index to quickly scan the id values, sort them by NEWID(), select the 150 ids we want, and then look up the padding data.  The logical reads with the new indexes in place are: Table 'TestCHAR' logical reads 835 lob logical reads 0 Table 'TestMAX' logical reads 835 lob logical reads 0 Table 'TestTEXT' logical reads 686 lob logical reads 597 Table 'TestMAXOOR' logical reads 686 lob logical reads 448 With the new index, all four queries use the same query plan (click to enlarge): Performance Summary: 0.3 seconds elapsed time 6MB memory grant 0MB tempdb usage 1MB sort set 835 logical reads (CHAR, MAX) 686 logical reads (TEXT, MAXOOR) 597 LOB logical reads (TEXT) 448 LOB logical reads (MAXOOR) No sort warning I’ll leave it as an exercise for the reader to work out why trying to eliminate the Key Lookup by adding the padding column to the new nonclustered indexes would be a daft idea Conclusion This post is not about tuning queries that access columns containing big strings.  It isn’t about the internal differences between TEXT and MAX data types either.  It isn’t even about the cool use of UPDATE .WRITE used in the MAXOOR table load.  No, this post is about something else: Many developers might not have tuned our starting example query at all – 5 seconds isn’t that bad, and the original query plan looks reasonable at first glance.  Perhaps the NEWID() function would have been blamed for ‘just being slow’ – who knows.  5 seconds isn’t awful – unless your users expect sub-second responses – but using 250MB of memory and writing 200MB to tempdb certainly is!  If ten sessions ran that query at the same time in production that’s 2.5GB of memory usage and 2GB hitting tempdb.  Of course, not all queries can be rewritten to avoid large memory grants and sort spills using the key-lookup technique in this post, but that’s not the point either. The point of this post is that a basic understanding of execution plans is not enough.  Tuning for logical reads and adding covering indexes is not enough.  If you want to produce high-quality, scalable TSQL that won’t get you paged as soon as it hits production, you need a deep understanding of execution plans, and as much accurate, deep knowledge about SQL Server as you can lay your hands on.  The advanced database developer has a wide range of tools to use in writing queries that perform well in a range of circumstances. By the way, the examples in this post were written for SQL Server 2008.  They will run on 2005 and demonstrate the same principles, but you won’t get the same figures I did because 2005 had a rather nasty bug in the Top N Sort operator.  Fair warning: if you do decide to run the scripts on a 2005 instance (particularly the parallel query) do it before you head out for lunch… This post is dedicated to the people of Christchurch, New Zealand. © 2011 Paul White email: @[email protected] twitter: @SQL_Kiwi

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  • Sensei mouse sensitivity

    - by Marcelo
    I've recently acquired a Steelseries Sensei. Despite being a great mouse, I'm having some trouble finding settings that I can get used to... The mouse engine allows me to set a CPI from 0 to 5700. It also allows me to set it even higher, calling it "DCPI" (Double CPI), from 5701 to 11400. On Window's Control Panel, there's a "Pointer Speed" slider and a "Enhance Pointer Precision" checkbox (wording may be different as I use a non-english version). The majority of games allow me to set an in-game "Mouse Sensitivity". Some games let me use a "Raw mouse input". I'm already familiar with the basics of CPI/DPI - "higher CPI means less hand movement", but what are the differences between all those options? Is there a "better" or "worst" setting?

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  • Installing ImageMagick on Mac OSX 10.6

    - by Russell C.
    I just got a new Mac and am trying to setup a local Perl development environment. I'm using MAMP but also need the ImageMagick perl module installed in order to do some of the photo processing our scripts require. I tried installing ImageMagick manually but ran into some issues and after reading online a lot of people reported having issues going this route. The general consensus was to install it using MacPorts instead so I went ahead and installed MacPorts. Unfortunately, MacPorts can't seem to install it successfully either. Here is the command I'm using to try to install ImageMagick: sudo port install p5-perlmagick And here are all the errors reported during install: ---> Computing dependencies for p5-perlmagick ---> Building p5-perlmagick Error: Target org.macports.build returned: shell command " cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_perl_p5-perlmagick/work/PerlMagick-6.32" && /usr/bin/make -j2 all " returned error 2 Command output: Magick.xs:10918: error: 'struct Methods' has no member named 'exception' Magick.xs:10918: error: request for member 'severity' in something not a structure or union Magick.xs:10918: error: 'ErrorException' undeclared (first use in this function) Magick.xs:10919: error: 'struct Methods' has no member named 'exception' Magick.xs:10920: warning: implicit declaration of function 'GetImageException' Magick.xs:10922: error: 'struct PackageInfo' has no member named 'image_info' Magick.xs:10922: error: 'struct Methods' has no member named 'adjoin' Magick.xs:10929: error: request for member 'severity' in something not a structure or union Magick.xs:10929: error: 'UndefinedException' undeclared (first use in this function) Magick.xs:10929: error: request for member 'severity' in something not a structure or union Magick.xs:10929: error: request for member 'reason' in something not a structure or union Magick.xs:10929: error: request for member 'severity' in something not a structure or union Magick.xs:10929: error: request for member 'reason' in something not a structure or union Magick.xs:10929: warning: pointer/integer type mismatch in conditional expression Magick.xs:10929: error: request for member 'description' in something not a structure or union Magick.xs:10929: error: request for member 'description' in something not a structure or union Magick.xs:10929: error: request for member 'severity' in something not a structure or union Magick.xs:10929: error: request for member 'description' in something not a structure or union Magick.xs:10929: warning: pointer/integer type mismatch in conditional expression Magick.xs:10929: error: request for member 'description' in something not a structure or union Magick.xs:10929: warning: passing argument 2 of 'Perl_sv_catpv' from incompatible pointer type Magick.xs:10929: warning: unused variable 'message' Magick.xs:10856: warning: unused variable 'filename' Magick.c:10784: warning: unused variable 'ref' Magick.c:10777: warning: unused variable 'ix' Magick.xs: In function 'boot_Image__Magick': Magick.xs:2122: warning: implicit declaration of function 'InitializeMagick' Magick.xs:2123: warning: implicit declaration of function 'SetWarningHandler' Magick.xs:2124: warning: implicit declaration of function 'SetErrorHandler' make: *** [Magick.o] Error 1 Error: Status 1 encountered during processing. Before reporting a bug, first run the command again with the -d flag to get complete output. I have no idea what the problem might be or how to go about successfully installing ImageMagick. I'd appreciate any help & advice that someone out there that has done this successfully might be able to provide. Thanks in advance!

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  • wmi not available for some time after reboot

    - by Alex Okrushko
    I'm having the problem with the WMI availability on logon. Right after reboot I open cmd and with python interpreter: >>> import wmi >>> c = wmi.WMI() >>> c.Win32_OperatingSystem() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "C:\Python27\lib\site-packages\wmi.py", line 1147, in __getattr__ return getattr (self._namespace, attribute) File "C:\Python27\lib\site-packages\win32com\client\dynamic.py", line 516, in __getattr__ raise AttributeError("%s.%s" % (self._username_, attr)) AttributeError: winmgmts:.Win32_OperatingSystem >>> 5 minutes later I open another cmd and python interpreter: Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on win 32 Type "help", "copyright", "credits" or "license" for more information. >>> import wmi >>> c = wmi.WMI() >>> c.Win32_OperatingSystem() [<_wmi_object: \\W520-ALEX-WIN7\root\cimv2:Win32_OperatingSystem=@>] >>> NOTE: the first cmd still keeps saying AttributeError even 5 minutes later. NOTE 2: if I logout and login wmi is available, so it is somehow effected by reboot with process explorer I check the environmental variables and they are the same for both cmds What could that be? Please help. UPDATE: Apparently the problem is connecting to the wbem services: >>> import win32com.client >>> win32com.client.Dispatch('WbemScripting.SWbemLocator') <COMObject WbemScripting.SWbemLocator> >>> wmi_service= win32com.client.Dispatch('WbemScripting.SWbemLocator') >>> wbem_service = wmi_service.ConnectServer('.','root/cimv2') >>> wbem_service <COMObject <unknown>> >>> items = wbem_service.ExecQuery('Select * from Win32_OperatingSystem') Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<COMObject <unknown>>", line 3, in ExecQuery File "C:\Python27\lib\site-packages\win32com\client\dynamic.py", line 282, in _ApplyTypes_ result = self._oleobj_.InvokeTypes(*(dispid, LCID, wFlags, retType, argTypes ) + args) pywintypes.com_error: (-2147352567, 'Exception occurred.', (0, u'SWbemServicesEx ', u'Generic failure ', None, 0, -2147217407), None) >>> NOTE 3: wmic os always worked. NOTE 4: re-installing pywin32 package didn't help. Neither did Re-registering/re-compiling the WMI components and resetting of the WMI database (as recommended here) NOTE 5: my 4 Other laptops don't have this problem. Also wmiprov.log has: (Mon Oct 29 11:40:07 2012.248587) : *************************************** (Mon Oct 29 11:40:07 2012.248587) : Could not get pointer to binary resource for file: (Mon Oct 29 11:40:07 2012.248587) : C:\Windows\system32\drivers\ndis.sys[MofResourceName](Mon Oct 29 11:40:07 2012.248587) : (Mon Oct 29 11:40:07 2012.248587) : *************************************** (Mon Oct 29 11:40:07 2012.248587) : *************************************** (Mon Oct 29 11:40:07 2012.248587) : Could not get pointer to binary resource for file: (Mon Oct 29 11:40:07 2012.248587) : C:\Windows\system32\drivers\en-US\ndis.sys.mui[MofResourceName](Mon Oct 29 11:40:07 2012.248587) : (Mon Oct 29 11:40:07 2012.248587) : *************************************** (Mon Oct 29 11:40:07 2012.248603) : *************************************** (Mon Oct 29 11:40:07 2012.248603) : Could not get pointer to binary resource for file: (Mon Oct 29 11:40:07 2012.248603) : C:\Windows\system32\DRIVERS\wmiacpi.sys[MofResource](Mon Oct 29 11:40:07 2012.248603) : (Mon Oct 29 11:40:07 2012.248603) : *************************************** (Mon Oct 29 11:40:07 2012.248603) : *************************************** (Mon Oct 29 11:40:07 2012.248603) : Could not get pointer to binary resource for file: (Mon Oct 29 11:40:07 2012.248603) : C:\Windows\system32\DRIVERS\monitor.sys[MonitorWMI](Mon Oct 29 11:40:07 2012.248603) : (Mon Oct 29 11:40:07 2012.248603) : *************************************** NOTE 6: the WMIDiag tool report is at my dropbox

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  • compiling openss7

    - by deddihp
    hello, i got an error while compiling openss7. Do you know what happen ? Thanks.... gcc -DHAVE_CONFIG_H -I. -I. -I. -DLFS=1 -imacros ./config.h -imacros ./include/sys/config.h -I. -I./include -I./include -nostdinc -iwithprefix include -DLINUX -D__KERNEL__ -I/usr/src/linux-headers-lbm-2.6.28-11-generic -I/lib/modules/2.6.28-11-generic/build/include -Iinclude2 -I/lib/modules/2.6.28-11-generic/build/include -I/lib/modules/2.6.28-11-generic/build/arch/x86/include -include /lib/modules/2.6.28-11-generic/build/include/linux/autoconf.h -Iubuntu/include -I/lib/modules/2.6.28-11-generic/build/ubuntu/include -I/lib/modules/2.6.28-11-generic/build/arch/x86/include/asm/mach-default '-DKBUILD_STR(s)=#s' '-DKBUILD_BASENAME=KBUILD_STR('`echo libLfS_specfs_a-specfs.o | sed -e 's,lib.*_a-,,;s,\.o,,;s,-,_,g'`')' -DMODULE -D__NO_VERSION__ -DEXPORT_SYMTAB -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -O2 -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i586 -mtune=generic -Wa,-mtune=generic32 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -Wdeclaration-after-statement -Wno-pointer-sign -fwrapv -ffreestanding -c -o libLfS_specfs_a-specfs.o `test -f 'src/kernel/specfs.c' || echo './'`src/kernel/specfs.c In file included from src/kernel/specfs.c:123: src/kernel/strspecfs.c: In function ‘specfs_init_cache’: src/kernel/strspecfs.c:1406: warning: passing argument 5 of ‘kmem_cache_create’ from incompatible pointer type src/kernel/strspecfs.c:1406: error: too many arguments to function ‘kmem_cache_create’ In file included from src/kernel/specfs.c:126: src/kernel/strlookup.c: In function ‘cdev_lookup’: src/kernel/strlookup.c:508: warning: format not a string literal and no format arguments src/kernel/strlookup.c:514: warning: format not a string literal and no format arguments src/kernel/strlookup.c:521: warning: format not a string literal and no format arguments src/kernel/strlookup.c: In function ‘cdrv_lookup’: src/kernel/strlookup.c:562: warning: format not a string literal and no format arguments src/kernel/strlookup.c: In function ‘fmod_lookup’: src/kernel/strlookup.c:604: warning: format not a string literal and no format arguments src/kernel/strlookup.c: In function ‘cdev_search’: src/kernel/strlookup.c:709: warning: format not a string literal and no format arguments src/kernel/strlookup.c:716: warning: format not a string literal and no format arguments src/kernel/strlookup.c: In function ‘fmod_search’: src/kernel/strlookup.c:768: warning: format not a string literal and no format arguments src/kernel/strlookup.c: In function ‘cmin_search’: src/kernel/strlookup.c:823: warning: format not a string literal and no format arguments src/kernel/strlookup.c:830: warning: format not a string literal and no format arguments src/kernel/strlookup.c:840: warning: format not a string literal and no format arguments src/kernel/strlookup.c:848: warning: format not a string literal and no format arguments In file included from src/kernel/specfs.c:129: src/kernel/strattach.c: In function ‘check_mnt’: src/kernel/strattach.c:131: error: ‘struct vfsmount’ has no member named ‘mnt_namespace’ src/kernel/strattach.c:131: error: ‘struct task_struct’ has no member named ‘namespace’ src/kernel/strattach.c: In function ‘do_fattach’: src/kernel/strattach.c:200: error: ‘struct nameidata’ has no member named ‘dentry’ src/kernel/strattach.c:200: error: ‘struct nameidata’ has no member named ‘mnt’ src/kernel/strattach.c:200: error: ‘struct nameidata’ has no member named ‘dentry’ src/kernel/strattach.c:203: error: ‘struct nameidata’ has no member named ‘mnt’ src/kernel/strattach.c:208: error: ‘struct nameidata’ has no member named ‘mnt’ src/kernel/strattach.c:208: error: ‘struct nameidata’ has no member named ‘mnt’ src/kernel/strattach.c:208: error: ‘struct nameidata’ has no member named ‘dentry’ src/kernel/strattach.c:226: error: implicit declaration of function ‘path_release’ src/kernel/strattach.c: In function ‘do_fdetach’: src/kernel/strattach.c:253: error: ‘struct nameidata’ has no member named ‘dentry’ src/kernel/strattach.c:253: error: ‘struct nameidata’ has no member named ‘mnt’ src/kernel/strattach.c:255: error: ‘struct nameidata’ has no member named ‘mnt’ src/kernel/strattach.c:257: error: ‘struct nameidata’ has no member named ‘dentry’ src/kernel/strattach.c:262: error: ‘struct nameidata’ has no member named ‘mnt’ src/kernel/strattach.c:265: error: ‘struct nameidata’ has no member named ‘mnt’ In file included from src/kernel/specfs.c:132: src/kernel/strpipe.c: In function ‘do_spipe’: src/kernel/strpipe.c:372: warning: assignment discards qualifiers from pointer target type make[4]: *** [libLfS_specfs_a-specfs.o] Error 1 make[4]: Leaving directory `/home/deddihp/dev/source/openss7-0.9.2.G/streams-0.9.2.4' make[3]: *** [all-recursive] Error 1 make[3]: Leaving directory `/home/deddihp/dev/source/openss7-0.9.2.G/streams-0.9.2.4' make[2]: *** [all] Error 2 make[2]: Leaving directory `/home/deddihp/dev/source/openss7-0.9.2.G/streams-0.9.2.4' make[1]: *** [all-recursive] Error 1 make[1]: Leaving directory `/home/deddihp/dev/source/openss7-0.9.2.G' make: *** [all] Error 2

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  • A RenderTargetView cannot be created from a NULL Resource

    - by numerical25
    I am trying to create my render target view but I get this error from direct X A RenderTargetView cannot be created from a NULL Resource To my knowledge it seems that I must fill the rendertarget pointer with data before passing it. But I am having trouble figure out how. Below is my declaration and implementation declaration #pragma once #include "stdafx.h" #include "resource.h" #include "d3d10.h" #include "d3dx10.h" #include "dinput.h" #define MAX_LOADSTRING 100 class RenderEngine { protected: RECT m_screenRect; //direct3d Members ID3D10Device *m_pDevice; // The IDirect3DDevice10 // interface ID3D10Texture2D *m_pBackBuffer; // Pointer to the back buffer ID3D10RenderTargetView *m_pRenderTargetView; // Pointer to render target view IDXGISwapChain *m_pSwapChain; // Pointer to the swap chain RECT m_rcScreenRect; // The dimensions of the screen ID3DX10Font *m_pFont; // The font used for rendering text // Sprites used to hold font characters ID3DX10Sprite *m_pFontSprite; ATOM RegisterEngineClass(); void Present(); public: static HINSTANCE m_hInst; HWND m_hWnd; int m_nCmdShow; TCHAR m_szTitle[MAX_LOADSTRING]; // The title bar text TCHAR m_szWindowClass[MAX_LOADSTRING]; // the main window class name void DrawTextString(int x, int y, D3DXCOLOR color, const TCHAR *strOutput); //static functions static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam); static INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam); bool InitWindow(); bool InitDirectX(); bool InitInstance(); int Run(); RenderEngine() { m_screenRect.right = 800; m_screenRect.bottom = 600; } }; my implementation bool RenderEngine::InitDirectX() { //potential error. You did not set to zero memory and you did not set the scaling property DXGI_MODE_DESC bd; bd.Width = m_screenRect.right; bd.Height = m_screenRect.bottom; bd.Format = DXGI_FORMAT_R8G8B8A8_UNORM; bd.RefreshRate.Numerator = 60; bd.RefreshRate.Denominator = 1; DXGI_SAMPLE_DESC sd; sd.Count = 1; sd.Quality = 0; DXGI_SWAP_CHAIN_DESC swapDesc; ZeroMemory(&swapDesc, sizeof(swapDesc)); swapDesc.BufferDesc = bd; swapDesc.SampleDesc = sd; swapDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT; swapDesc.OutputWindow = m_hWnd; swapDesc.BufferCount = 1; swapDesc.SwapEffect = DXGI_SWAP_EFFECT_DISCARD, swapDesc.Windowed = true; swapDesc.Flags = 0; HRESULT hr; hr = D3D10CreateDeviceAndSwapChain(NULL, D3D10_DRIVER_TYPE_HARDWARE, NULL, D3D10_CREATE_DEVICE_DEBUG, D3D10_SDK_VERSION , &swapDesc, &m_pSwapChain, &m_pDevice); if(FAILED(hr)) return false; // Create a render target view hr = m_pDevice->CreateRenderTargetView( m_pBackBuffer, NULL, &m_pRenderTargetView); // FAILS RIGHT HERE // if(FAILED(hr)) return false; return true; }

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  • A black screen with only the mouse cursor while booting

    - by akb.zak
    Once i tried to re-install Windows 7. I formatted C drive, during installation system was hanged during the step "installing updates". then i cancelled the process. When i tried again, after booting from CD a black screen with a mouse pointer appears. No further progress. The mouse pointer can be moved. I tried with some other disks also. I tried with installing ubuntu also. Even though similar condition.plz help........... I cannot install an OS

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  • Problem whit usb wireless mouse

    - by aiacet
    Recently i have thi problem whit my wireless mouse (Trust model on: www.trust.com/15313). Sometimes when i start the Pc or during a game the pointer/arrow stop to move it. In the Pc start the pointer is blocked on the center of the screen. If I'm lucky i have to chance the USB wirless adapter from port 1 to port 2 but sometimes this trick doesn't work i to use the mouse i have to restart. Like you can see in the productor webpage this mouse don't have the direver but only a tool to solve some problem. Thank you in advance to all the "super-users" that reading this question would be help me Ajax

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  • Debian Squeeze: Trackpad on EEE PC 1000HA acts like slate

    - by CarlF
    I'm using Debian on an Asus Eee PC 1000HA. It works flawlessly, except that the built-in trackpad acts as if it was a slate. That is, if I touch the upper-left quadrant of the trackpad, the mouse pointer "teleports" to the upper left of the netbook's screen. If I touch the bottom center, the pointer teleports to the bottom center of the screen. I currently have no xorg.conf. I have tried various settings for the mouse in xorg.confs that I created, and none of them did more than disable the trackpad entirely. The trackpad works perfectly in Windows XP (shipped with the Eee) and in Ubuntu. Debian works fine with the (USB) mouse. Any suggestions? Thanks.

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  • Problem with usb wireless mouse

    - by aiacet
    Recently I have started having problems with my wireless mouse (Wireless Optical Mouse MI-4910D). Sometimes when I start my PC or during a game the pointer/arrow stops moving. When the PC boots the pointer is locked in the center of the screen. If I'm lucky it helps to change the USB wireless adapter from port 1 to port 2 but sometimes this trick doesn't work and I have to restart my PC to get the mouse to work again. Like you can see in the product web page this mouse don't have a driver but only a tool to solve some problems. Thank you in advance to all the "super-users" that reading this question would be help me Ajax

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  • Installing ruby 1.9.1 on OS X with RVM, getting error I can't make sense of

    - by Pselus
    I'm trying to update my ruby install on Leopard to at least 1.9.1. I found a tutorial that tells me how to do it with RVM and I get as far as downloading, configuring and compiling the version I want, but during the compile I get errors. When checking the make.error.log file this is the message I get: [2010-11-07 13:43:44] make main.c: In function ‘objcdummyfunction’: main.c:19: warning: implicit declaration of function ‘objc_msgSend’ main.c: At top level: main.c:19: warning: ‘objcdummyfunction’ defined but not used eval.c: In function ‘ruby_cleanup’: eval.c:139: warning: passing argument 1 of ‘ruby_init_stack’ discards qualifiers from pointer target type gc.c: In function ‘garbage_collect_with_gvl’: gc.c:597: warning: cast from pointer to integer of different size w: illegal option -- L usage: w [hi] [user ...] make: [libruby.1.9.1.dylib] Error 1 (ignored) readline.c: In function ‘username_completion_proc_call’: readline.c:1159: error: ‘username_completion_function’ undeclared (first use in this function) readline.c:1159: error: (Each undeclared identifier is reported only once readline.c:1159: error: for each function it appears in.) make[1]: *** [readline.o] Error 1 make: *** [mkmain.sh] Error 1 I have no idea what any of that means. Help?

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  • dell studio 1558 multi touchpad multi finger problem

    - by christian130
    Recently I bought an Intel Core i7 Dell laptop fully integrated. I have an ATi Radeon 1 gb ram graphic card and so on. Everything works fine even the brightness, but when I try the multi touch multi finger(touchpad which enables two or more finger) the pointer jump and go there and go here and so It's very annoying because when I'm trying to write this question I cannot let the pointer be cool! when I accidentally the touchpad it is very annoying. How can I fix this ?

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  • Is there a library available which easily can record and replay results of API calls?

    - by Billy ONeal
    I'm working on writing various things that call relatively complicated Win32 API functions. Here's an example: //Encapsulates calling NtQuerySystemInformation buffer management. WindowsApi::AutoArray NtDll::NtQuerySystemInformation( SystemInformationClass toGet ) const { AutoArray result; ULONG allocationSize = 1024; ULONG previousSize; NTSTATUS errorCheck; do { previousSize = allocationSize; result.Allocate(allocationSize); errorCheck = WinQuerySystemInformation(toGet, result.GetAs<void>(), allocationSize, &allocationSize); if (allocationSize <= previousSize) allocationSize = previousSize * 2; } while (errorCheck == 0xC0000004L); if (errorCheck != 0) { THROW_MANUAL_WINDOWS_ERROR(WinRtlNtStatusToDosError(errorCheck)); } return result; } //Client of the above. ProcessSnapshot::ProcessSnapshot() { using Dll::NtDll; NtDll ntdll; AutoArray systemInfoBuffer = ntdll.NtQuerySystemInformation( NtDll::SystemProcessInformation); BYTE * currentPtr = systemInfoBuffer.GetAs<BYTE>(); //Loop through the results, creating Process objects. SYSTEM_PROCESSES * asSysInfo; do { // Loop book keeping asSysInfo = reinterpret_cast<SYSTEM_PROCESSES *>(currentPtr); currentPtr += asSysInfo->NextEntryDelta; //Create the process for the current iteration and fill it with data. std::auto_ptr<ProcImpl> currentProc(ProcFactory( static_cast<unsigned __int32>(asSysInfo->ProcessId), this)); NormalProcess* nptr = dynamic_cast<NormalProcess*>(currentProc.get()); if (nptr) { nptr->SetProcessName(asSysInfo->ProcessName); } // Populate process threads for(ULONG idx = 0; idx < asSysInfo->ThreadCount; ++idx) { SYSTEM_THREADS& sysThread = asSysInfo->Threads[idx]; Thread thread( currentProc.get(), static_cast<unsigned __int32>(sysThread.ClientId.UniqueThread), sysThread.StartAddress); currentProc->AddThread(thread); } processes.push_back(currentProc); } while(asSysInfo->NextEntryDelta != 0); } My problem is in mocking out the NtDll::NtQuerySystemInformation method -- namely, that the data structure returned is complicated (Well, here it's actually relatively simple but it can be complicated), and writing a test which builds the data structure like the API call does can take 5-6 times as long as writing the code that uses the API. What I'd like to do is take a call to the API, and record it somehow, so that I can return that recorded value to the code under test without actually calling the API. The returned structures cannot simply be memcpy'd, because they often contain inner pointers (pointers to other locations in the same buffer). The library in question would need to check for these kinds of things, and be able to restore pointer values to a similar buffer upon replay. (i.e. check each pointer sized value if it could be interpreted as a pointer within the buffer, change that to an offset, and remember to change it back to a pointer on replay -- a false positive rate here is acceptable) Is there anything out there that does anything like this?

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  • Const-correctness semantics in C++

    - by thirtythreeforty
    For fun and profit™, I'm writing a trie class in C++ (using the C++11 standard.) My trie<T> has an iterator, trie<T>::iterator. (They're all actually functionally const_iterators, because you cannot modify a trie's value_type.) The iterator's class declaration looks partially like this: template<typename T> class trie<T>::iterator : public std::iterator<std::bidirectional_iterator_tag, T> { friend class trie<T>; struct state { state(const trie<T>* const node, const typename std::vector<std::pair<typename T::value_type, std::unique_ptr<trie<T>>>>::const_iterator& node_map_it ) : node{node}, node_map_it{node_map_it} {} // This pointer is to const data: const trie<T>* node; typename std::vector<std::pair<typename T::value_type, std::unique_ptr<trie<T>>>>::const_iterator node_map_it; }; public: typedef const T value_type; iterator() =default; iterator(const trie<T>* node) { parents.emplace(node, node->children.cbegin()); // ... } // ... private: std::stack<state> parents; // ... }; Notice that the node pointer is declared const. This is because (in my mind) the iterator should not be modifying the node that it points to; it is just an iterator. Now, elsewhere in my main trie<T> class, I have an erase function that has a common STL signature--it takes an iterator to data to erase (and returns an iterator to the next object). template<typename T> typename trie<T>::iterator trie<T>::erase(const_iterator it) { // ... // Cannot modify a const object! it.parents.top().node->is_leaf = false; // ... } The compiler complains because the node pointer is read-only! The erase function definitely should modify the trie that the iterator points to, even though the iterator shouldn't. So, I have two questions: Should iterator's constructors be public? trie<T> has the necessary begin() and end() members, and of course trie<T>::iterator and trie<T> are mutual friends, but I don't know what the convention is. Making them private would solve a lot of the angst I'm having about removing the const "promise" from the iterator's constructor. What are the correct const semantics/conventions regarding the iterator and its node pointer here? Nobody has ever explained this to me, and I can't find any tutorials or articles on the Web. This is probably the more important question, but it does require a good deal of planning and proper implementation. I suppose it could be circumvented by just implementing 1, but it's the principle of the thing!

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  • where is the error in this C code , and how to get rid of the warnings?

    - by mekasperasky
    #include<stdio.h> #include<string.h> //This program is a sorting application that reads a sequence of numbers from a file and prints them on the screen . The reading from the file here , is a call back function . typedef int (*CompFunc)(const char* , const char* ); typedef int (*ReadCheck)(char nullcheck); char array[100]; //Let this fucntion be done in the library itself . It doesnt care as to where the compare function and how is it implemented . Meaning suppose the function wants to do sort in ascending order or in descending order then the changes have to be done by the client code in the "COMPARE" function who will be implementing the lib code . void ReadFile(FILE *fp,ReadCheck rc) { char a; char d[100]; int count = 0,count1=0; a=fgetc(fp); while(1 != (*rc)(a)) { if(a=='\0') { strcpy(array[count],d); count=count+1; } else { d[count1]=a; count1=count1+1; } } } void Bubblesort(int* array , int size , int elem_size , CompFunc cf) { int i,j; int *temp; for( i=0;i < size ;i++) { for ( j=0;j < size -1 ; j++) { // make the callback to the comparision function if(1 == (*cf)(array+j*elem_size,array+ (j+1)*elem_size)) { //interchanging of elements temp = malloc(sizeof(int *) * elem_size); memcpy(temp , array+j*elem_size,elem_size); memcpy(array+j*elem_size,array+(j+1)*elem_size,elem_size); memcpy(array + (j+1)*elem_size , temp , elem_size); free(temp); } } } } //Let these functions be done at the client side int Compare(const char* el1 , const char* el2) { int element1 = *(int*)el1; int element2 = *(int*)el2; if(element1 < element2 ) return -1; if(element1 > element2) return 1 ; return 0; } int ReadChecked(char nullcheck) { if (nullcheck=='\n') return 1; else return 0; } int main() { FILE fp1; int k; fp1=fopen("readdata.txt","r"); Readfile(fp1,&ReadChecked); Bubblesort((char*)array,5,sizeof(array[0]),&Compare); printf("after sorting \n"); for (k=0;k<5;k++) printf("%d",array[k]); return 0; } The error i get is fsc1.c: In function ‘ReadFile’: fsc1.c:19: warning: passing argument 1 of ‘strcpy’ makes pointer from integer without a cast fsc1.c: In function ‘Bubblesort’: fsc1.c:40: warning: passing argument 1 of ‘cf’ from incompatible pointer type fsc1.c:40: warning: passing argument 2 of ‘cf’ from incompatible pointer type fsc1.c:43: warning: incompatible implicit declaration of built-in function ‘malloc’ fsc1.c:47: warning: incompatible implicit declaration of built-in function ‘free’ fsc1.c: In function ‘main’: fsc1.c:80: error: incompatible types in assignment fsc1.c:82: warning: passing argument 1 of ‘Bubblesort’ from incompatible pointer type

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  • Windows 8: Is Internet Explorer10 Metro mode disabled? Here is the fix.

    - by Gopinath
    Are you having issues with Internet Explorer 10 on Windows 8? Is Internet Explorer 10 application not launching in Metro mode and always launching in Desktop mode? Continue reading the post to understand and fix the problem. When Internet Explorer 10 does not launch in Metro mode? On Windows 8 when Internet Explorer is launched from Start screen it launches in Metro UI mode and when launched from Desktop it launches in traditional desktop UI mode. But when Internet Explorer  is not set as default browser, Windows 8 always launches Internet Explorer in Desktop mode irrespective of whether its launched from Start screen or Desktop. This generally happens when we install the browsers Firefox or Chrome and set them as default browser. How to restore Internet Explorer 10 Metro mode? The problem can be resolved by setting Internet Explorer 10 as the default web browser in Windows 8. But setting default web browser in Windows 8 is a bit tricky as there is no option available Options screen of  of Internet Explorer. To set Internet Explorer 10 as the default web browser follow these steps 1. Go to Start screen of Windows 8 and search for Default Programs app by typing Default using keyboard. 2. Click on the link Set your default programs 3. Choose Internet Explorer on the left section of the screen(pointer 1) and then click on the option Set this program as default available at the bottom right section(pointer 2) 4. That’s it. Now Internet Explorer is set as default web browser and from now onwards you will be able to launch Metro UI based Internet Explorer from Start screen

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  • Ogre 3d and bullet physics interaction

    - by Tim
    I have been playing around with Ogre3d and trying to integrate bullet physics. I have previously somewhat successfully got this functionality working with irrlicht and bullet and I am trying to base this on what I had done there, but modifying it to fit with Ogre. It is working but not correctly and I would like some help to understand what it is I am doing wrong. I have a state system and when I enter the "gamestate" I call some functions such as setting up a basic scene, creating the physics simulation. I am doing that as follows. void GameState::enter() { ... // Setup Physics btBroadphaseInterface *BroadPhase = new btAxisSweep3(btVector3(-1000,-1000,-1000), btVector3(1000,1000,1000)); btDefaultCollisionConfiguration *CollisionConfiguration = new btDefaultCollisionConfiguration(); btCollisionDispatcher *Dispatcher = new btCollisionDispatcher(CollisionConfiguration); btSequentialImpulseConstraintSolver *Solver = new btSequentialImpulseConstraintSolver(); World = new btDiscreteDynamicsWorld(Dispatcher, BroadPhase, Solver, CollisionConfiguration); ... createScene(); } In the createScene method I add a light and try to setup a "ground" plane to act as the ground for things to collide with.. as follows. I expect there is issues with this as I get objects colliding with the ground but half way through it and they glitch around like crazy on collision. void GameState::createScene() { m_pSceneMgr->createLight("Light")->setPosition(75,75,75); // Physics // As a test we want a floor plane for things to collide with Ogre::Entity *ent; Ogre::Plane p; p.normal = Ogre::Vector3(0,1,0); p.d = 0; Ogre::MeshManager::getSingleton().createPlane( "FloorPlane", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME, p, 200000, 200000, 20, 20, true, 1, 9000,9000,Ogre::Vector3::UNIT_Z); ent = m_pSceneMgr->createEntity("floor", "FloorPlane"); ent->setMaterialName("Test/Floor"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(ent); btTransform Transform; Transform.setIdentity(); Transform.setOrigin(btVector3(0,1,0)); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); btCollisionShape *Shape = new btStaticPlaneShape(btVector3(0,1,0),0); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(0, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(0, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; // End Physics } I then have a method to create a cube and give it rigid body physics properties. I know there will be errors here as I get the items colliding with the ground but not with each other properly. So I would appreciate some input on what I am doing wrong. void GameState::CreateBox(const btVector3 &TPosition, const btVector3 &TScale, btScalar TMass) { Ogre::Vector3 size = Ogre::Vector3::ZERO; Ogre::Vector3 pos = Ogre::Vector3::ZERO; Ogre::Vector3 scale = Ogre::Vector3::ZERO; pos.x = TPosition.getX(); pos.y = TPosition.getY(); pos.z = TPosition.getZ(); scale.x = TScale.getX(); scale.y = TScale.getY(); scale.z = TScale.getZ(); Ogre::Entity *entity = m_pSceneMgr->createEntity( "Box" + Ogre::StringConverter::toString(m_pNumEntities), "cube.mesh"); entity->setCastShadows(true); Ogre::AxisAlignedBox boundingB = entity->getBoundingBox(); size = boundingB.getSize(); //size /= 2.0f; // Only the half needed? //size *= 0.96f; // Bullet margin is a bit bigger so we need a smaller size entity->setMaterialName("Test/Cube"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(entity); node->setPosition(pos); //node->scale(scale); // Physics btTransform Transform; Transform.setIdentity(); Transform.setOrigin(TPosition); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); btVector3 HalfExtents(TScale.getX()*0.5f,TScale.getY()*0.5f,TScale.getZ()*0.5f); btCollisionShape *Shape = new btBoxShape(HalfExtents); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(TMass, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(TMass, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; } Then in the GameState::update() method which which runs every frame to handle input and render etc I call an UpdatePhysics method to update the physics simulation. void GameState::UpdatePhysics(unsigned int TDeltaTime) { World->stepSimulation(TDeltaTime * 0.001f, 60); btRigidBody *TObject; for(std::vector<btRigidBody *>::iterator it = Objects.begin(); it != Objects.end(); ++it) { // Update renderer Ogre::SceneNode *node = static_cast<Ogre::SceneNode *>((*it)->getUserPointer()); TObject = *it; // Set position btVector3 Point = TObject->getCenterOfMassPosition(); node->setPosition(Ogre::Vector3((float)Point[0], (float)Point[1], (float)Point[2])); // set rotation btVector3 EulerRotation; QuaternionToEuler(TObject->getOrientation(), EulerRotation); node->setOrientation(1,(Ogre::Real)EulerRotation[0], (Ogre::Real)EulerRotation[1], (Ogre::Real)EulerRotation[2]); //node->rotate(Ogre::Vector3(EulerRotation[0], EulerRotation[1], EulerRotation[2])); } } void GameState::QuaternionToEuler(const btQuaternion &TQuat, btVector3 &TEuler) { btScalar W = TQuat.getW(); btScalar X = TQuat.getX(); btScalar Y = TQuat.getY(); btScalar Z = TQuat.getZ(); float WSquared = W * W; float XSquared = X * X; float YSquared = Y * Y; float ZSquared = Z * Z; TEuler.setX(atan2f(2.0f * (Y * Z + X * W), -XSquared - YSquared + ZSquared + WSquared)); TEuler.setY(asinf(-2.0f * (X * Z - Y * W))); TEuler.setZ(atan2f(2.0f * (X * Y + Z * W), XSquared - YSquared - ZSquared + WSquared)); TEuler *= RADTODEG; } I seem to have issues with the cubes not colliding with each other and colliding strangely with the ground. I have tried to capture the effect with the attached image. I would appreciate any help in understanding what I have done wrong. Thanks. EDIT : Solution The following code shows the changes I made to get accurate physics. void GameState::createScene() { m_pSceneMgr->createLight("Light")->setPosition(75,75,75); // Physics // As a test we want a floor plane for things to collide with Ogre::Entity *ent; Ogre::Plane p; p.normal = Ogre::Vector3(0,1,0); p.d = 0; Ogre::MeshManager::getSingleton().createPlane( "FloorPlane", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME, p, 200000, 200000, 20, 20, true, 1, 9000,9000,Ogre::Vector3::UNIT_Z); ent = m_pSceneMgr->createEntity("floor", "FloorPlane"); ent->setMaterialName("Test/Floor"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(ent); btTransform Transform; Transform.setIdentity(); // Fixed the transform vector here for y back to 0 to stop the objects sinking into the ground. Transform.setOrigin(btVector3(0,0,0)); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); btCollisionShape *Shape = new btStaticPlaneShape(btVector3(0,1,0),0); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(0, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(0, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; // End Physics } void GameState::CreateBox(const btVector3 &TPosition, const btVector3 &TScale, btScalar TMass) { Ogre::Vector3 size = Ogre::Vector3::ZERO; Ogre::Vector3 pos = Ogre::Vector3::ZERO; Ogre::Vector3 scale = Ogre::Vector3::ZERO; pos.x = TPosition.getX(); pos.y = TPosition.getY(); pos.z = TPosition.getZ(); scale.x = TScale.getX(); scale.y = TScale.getY(); scale.z = TScale.getZ(); Ogre::Entity *entity = m_pSceneMgr->createEntity( "Box" + Ogre::StringConverter::toString(m_pNumEntities), "cube.mesh"); entity->setCastShadows(true); Ogre::AxisAlignedBox boundingB = entity->getBoundingBox(); // The ogre bounding box is slightly bigger so I am reducing it for // use with the rigid body. size = boundingB.getSize()*0.95f; entity->setMaterialName("Test/Cube"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(entity); node->setPosition(pos); node->showBoundingBox(true); //node->scale(scale); // Physics btTransform Transform; Transform.setIdentity(); Transform.setOrigin(TPosition); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); // I got the size of the bounding box above but wasn't using it to set // the size for the rigid body. This now does. btVector3 HalfExtents(size.x*0.5f,size.y*0.5f,size.z*0.5f); btCollisionShape *Shape = new btBoxShape(HalfExtents); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(TMass, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(TMass, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; } void GameState::UpdatePhysics(unsigned int TDeltaTime) { World->stepSimulation(TDeltaTime * 0.001f, 60); btRigidBody *TObject; for(std::vector<btRigidBody *>::iterator it = Objects.begin(); it != Objects.end(); ++it) { // Update renderer Ogre::SceneNode *node = static_cast<Ogre::SceneNode *>((*it)->getUserPointer()); TObject = *it; // Set position btVector3 Point = TObject->getCenterOfMassPosition(); node->setPosition(Ogre::Vector3((float)Point[0], (float)Point[1], (float)Point[2])); // Convert the bullet Quaternion to an Ogre quaternion btQuaternion btq = TObject->getOrientation(); Ogre::Quaternion quart = Ogre::Quaternion(btq.w(),btq.x(),btq.y(),btq.z()); // use the quaternion with setOrientation node->setOrientation(quart); } } The QuaternionToEuler function isn't needed so that was removed from code and header files. The objects now collide with the ground and each other appropriately.

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  • Acer Aspire One 725 - missing graphic card driver?

    - by Melon
    Recently I bought an Acer Aspire One 725 Netbook and installed Ubuntu 12.10 on it. I bought it, because it can run HD movies and has Full HD on external VGA port. However, movies from youtube have a really slow framerate. If you open three tabs in Opera (for example g-mail, youtube and askubuntu) it gets really laggy. My suspicion is that the driver for graphic card is missing. When I check the System->Details->Graphics the driver is unknown. After running lspci | grep VGA I get this output: 00:01.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Device 980a From what I see, I have a AMD C70 processor integrated with (or something similar) AMD Radeon HD 6290. Has anyone had the same problem? Do you know which drivers need to be installed for the graphics to work properly? On official Acer page there are only drivers for Win7 and Win8... Update: I have tried installing fglrx but I get the following error (either I don't have libraries or someone didn't make a clean build before release ;) /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c: In function ‘KCL_MEM_AllocLinearAddrInterval’: /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c:2124:5: error: implicit declaration of function ‘do_mmap’ [-Werror=implicit-function-declaration] /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c:2124:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c: In function ‘kasInitExecutionLevels’: /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c:4159:5: error: ‘cpu_possible_map’ undeclared (first use in this function) /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c:4159:5: note: each undeclared identifier is reported only once for each function it appears in /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c:4159:5: warning: left-hand operand of comma expression has no effect [-Wunused-value] Update 2: After fixing the erros in compilation, ubuntu acts bizarre and unstable (no left icon panel, no upper panel, cannot run any programs, I only see desktop)

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  • Per-vertex animation with VBOs: VBO per character or VBO per animation?

    - by charstar
    Goal To leverage the richness of well vetted animation tools such as Blender to do the heavy lifting for a small but rich set of animations. I am aware of additive pose blending like that from Naughty Dog and similar techniques but I would prefer to expend a little RAM/VRAM to avoid implementing a thesis-ready pose solver. I would also like to avoid implementing a key-frame + interpolation curve solver (reinventing Blender vertex groups and IPOs), if possible. Scenario Meshes are animated using either skeletons (skinned animation) or some form of morph targets (i.e. per-vertex key frames). However, in either case, the animations are known in full at load-time, that is, there is no physics, IK solving, or any other form of in-game pose solving. The number of character actions (animations) will be limited but rich (hand-animated). There may be multiple characters using a each mesh and its animations simultaneously in-game (they will likely be at different frames of the same animation at the same time). Assume color and texture coordinate buffers are static. Current Considerations Much like a non-shader-powered pose solver, create a VBO for each character and copy vertex and normal data to each VBO on each frame (VBO in STREAMING). Create one VBO for each animation where each frame (interleaved vertex and normal data) is concatenated onto the VBO. Then each character simply has a buffer pointer offset based on its current animation frame (e.g. pointer offset = (numVertices+numNormals)*frameNumber). (VBO in STATIC) Known Trade-Offs In 1 above: Each VBO would be small but there would be many VBOs and therefore lots of buffer binding and vertex copying each frame. Both client and pipeline intensive. In 2 above: There would be few VBOs therefore insignificant buffer binding and no vertex data getting jammed down the pipe each frame, but each VBO would be quite large. Are there any pitfalls to number 2 (aside from finite memory)? I've found a lot of information on what you can do, but no real best practices. Are there other considerations or methods that I am missing?

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  • controlling an object through another object ?

    - by Stefano Borini
    Today I've seen the following pattern: you have an object A and an object B. Object B accepts a pointer to A at its constructor. Once B is created, there's a method B.doCalc() that performs a calculation (internally using A's information). The result is obtained with method B.getResult(). In order to perform another calculation, A is modified, and B.doCalc() is called again. What is your opinion on this choice ? I would have designed it differently, but I want to hear your voice. Edit : note that my main objection is to modify A to have a different result from B, without touching B. Although similar, I think that just this discipline expresses a much better feeling of what's going on. Instead of a = new A a.whatever = 5 b = new B(a) b.doCalc() res = b.getResult() a.whatever = 6 b.doCalc() res = b.getResult() You get the a pointer object from b itself. a = new A a.whatever = 5 b = new B(a) b.doCalc() res = b.getResult() a = b.getAPointer() a.whatever = 6 b.doCalc() res = b.getResult() because it makes more explicit the fact that a is taken from b and then modified. I still don't like it, though...

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  • How important do you find exception safety to be in your C++ code?

    - by Kai
    Every time I consider making my code strongly exception safe, I justify not doing it because it would be so time consuming. Consider this relatively simple snippet: Level::Entity* entity = new Level::Entity(); entity->id = GetNextId(); entity->AddComponent(new Component::Position(x, y)); entity->AddComponent(new Component::Movement()); entity->AddComponent(new Component::Render()); allEntities.push_back(entity); // std::vector entityById[entity->id] = entity; // std::map return entity; To implement a basic exception guarantee, I could use a scoped pointer on the new calls. This would prevent memory leaks if any of the calls were to throw an exception. However, let's say I want to implement a strong exception guarantee. At the least, I would need to implement a shared pointer for my containers (I'm not using Boost), a nothrow Entity::Swap for adding the components atomically, and some sort of idiom for atomically adding to both the Vector and Map. Not only would these be time consuming to implement, but they would be expensive since it involves a lot more copying than the exception unsafe solution. Ultimately, it feels to me like that time spent doing all of that wouldn't be justified just so that the a simple CreateEntity function is strongly exception safe. I probably just want the game to display an error and close at that point anyway. How far do you take this in your own game projects? Is it generally acceptable to write exception unsafe code for a program that can just crash when there is an exception?

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  • How to manage focus for a small set of simple widgets

    - by Christoph
    I'm developing a set of simple widgets for a small (128x128) display. For example I'd like to have a main screen with an overlay menu which I can use to toggle visibilty of main screen elements. Each option would be an icon with a box around it while it is selected. Button (left, up, right, down, enter) events should be given to the widget that has "focus". Focus is a simple thing to understand when using a GUI, but I'm having trouble implementing this. Can you suggest a simple concept for managing focus and input events? I have these simple ideas: Only one widget can have focus, so I need a single pointer to that widget. When this widget gets some kind of "cycle" input (as in "highlight the next item in this list"), the focus is given to a different widget. a widget must have a way of telling the application which widget the focus is given to next. if a widget cannot give a "next focus" hint, the application must be able to figure out where the focus should go. Widgets are currently structured like this: A widget can have a parent, which is passed to the constructor. Widgets are created statically, as I want to avoid dynamic memory allocation (I only have 16kB of RAM and I'd like to have control over that). widgets have siblings, implemented as an intrusive linked list (they have a next member). A parent has a pointer to the head of its list of children. Input events are arguments to the widgets buttonEvent methods which can accept or ignore that event. If it ignores the event, it can pass the event to its parent. My Questions: How can I manage focus for these widgets? Am I making this too complicated?

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