int - Page 182 - Developer IT

How to adjust microphone gain from C# (needs to work on XP & W7)...

- by Ed

First, note that I know there are a few questions like this already posted; however they don't seem to address the problem adequately. I have a C# application, with all the pInvoke hooks to talk to the waveXXX API, and I'm able to do capture and play back of audio with that. I'm also able to adjust speaker (WaveOut) volume with that API. The problem is that for whatever reason, that API does not allow me to adjust microphone (WaveIn) volume. So, I managed to find some mixer code that I've also pulled in and access through pInvoke and that allows me to adjust microphone volume, but only on my W7 PC. The mixer code I started with comes from here: http://social.msdn.microsoft.com/Forums/en-US/isvvba/thread/05dc2d35-1d45-4837-8e16-562ee919da85 and it works, but is written to adjust speaker volume. I added the SetMicVolume method shown here... public static void SetMicVolume(int mxid, int percentage) { bool rc; int mixer, vVolume; MIXERCONTROL volCtrl = new MIXERCONTROL(); int currentVol; mixerOpen(out mixer, mxid, 0, 0, MIXER_OBJECTF_WAVEIN); int type = MIXERCONTROL_CONTROLTYPE_VOLUME; rc = GetVolumeControl(mixer, MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE, type, out volCtrl, out currentVol); if (rc == false) { mixerClose(mixer); mixerOpen(out mixer, 0, 0, 0, 0); rc = GetVolumeControl(mixer, MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE, type, out volCtrl, out currentVol); if (rc == false) throw new Exception("SetMicVolume/GetVolumeControl() failed"); } vVolume = ((int)((float)(volCtrl.lMaximum - volCtrl.lMinimum) / 100.0F) * percentage); rc = SetVolumeControl(mixer, volCtrl, vVolume); if (rc == false) throw new Exception("SetMicVolume/SetVolumeControl() failed"); mixerClose(mixer); } Note the "second attempt" to call GetVolumeControl(). This is done because on XP, in the first call to GetVolumeControl (refer to site above for that code), the call to mixerGetLineControlsA() fails with XP systems returning MIXERR_INVALCONTROL. Then, with this second attempt using mixerOpen(out mixer, 0, 0, 0, 0), the code doesn't return a failure but the mic gain is unaffected. Note, as I said above, this works on W7 (the second attempt is never executed because it doesn't fail using mixerOpen(out mixer, mxid, 0, 0, MIXER_OBJECTF_WAVEIN)). I admit to not having a good grasp on the mixer API, so that's what I'm looking into now; however if anyone has a clue why this would work on W7, but not XP, I'd sure like to hear it. Meanwhile, if I figure it out before I get a response, I'll post my own answer...

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std::map insert segmentation fault

- by Jakub Czaplicki

Why does this code stop with segmentation fault : class MapFile { public: /* ... */ std::map <unsigned int, unsigned int> inToOut; }; bool MapFile::LoadMapFile( const wxString& fileName ) { /* ... */ inToOut.insert( std::make_pair(input,output) ); } but this one works fine : class MapFile { public: /* ... */ }; bool MapFile::LoadMapFile( const wxString& fileName ) { /* ... */ std::map <unsigned int, unsigned int> inToOut; inToOut.insert( std::make_pair(input,output) ); } ?

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[C++] My First Go With Function Templates

- by bobber205

Thought it was pretty straight forward. But I get a "iterator not dereferencable" errro when running the below code. What's wrong? template<typename T> struct SumsTo : public std::binary_function<T, T, bool> { int myInt; SumsTo(int a) { myInt = a; } bool operator()(const T& l, const T& r) { cout << l << " + " << r; if ((l + r) == myInt) { cout << " does add to " << myInt; } else { cout << " DOES NOT add to " << myInt; } return true; } }; void main() { list<int> l1; l1.push_back(1); l1.push_back(2); l1.push_back(3); l1.push_back(4); list<int> l2; l2.push_back(9); l2.push_back(8); l2.push_back(7); l2.push_back(6); transform(l1.begin(), l1.end(), l2.begin(), l2.end(), SumsTo<int>(10) ); }

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In C++, what is the "order of precedence" for shadowed variable names?

- by Emile Cormier

In C++, what is the "order of precedence" for shadowed variable names? I can't seem to find a concise answer online. For example: #include <iostream> int shadowed = 1; struct Foo { Foo() : shadowed(2) {} void bar(int shadowed = 3) { std::cout << shadowed << std::endl; // What does this output? } int shadowed; }; int main() { Foo().bar(); } I can't think of any other scopes where a variable might conflict. Please let me know if I missed one.

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STL vectors with uninitialized storage?

- by Jim Hunziker

I'm writing an inner loop that needs to place structs in contiguous storage. I don't know how many of these structs there will be ahead of time. My problem is that STL's vector initializes its values to 0, so no matter what I do, I incur the cost of the initialization plus the cost of setting the struct's members to their values. Is there any way to prevent the initialization, or is there an STL-like container out there with resizeable contiguous storage and uninitialized elements? (I'm certain that this part of the code needs to be optimized, and I'm certain that the initialization is a significant cost.) Also, see my comments below for a clarification about when the initialization occurs. SOME CODE: void GetsCalledALot(int* data1, int* data2, int count) { int mvSize = memberVector.size() memberVector.resize(mvSize + count); // causes 0-initialization for (int i = 0; i < count; ++i) { memberVector[mvSize + i].d1 = data1[i]; memberVector[mvSize + i].d2 = data2[i]; } }

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How can this code be made more Pythonic?

- by usethedeathstar

This next part of code does exactly what I want it to do. dem_rows and dem_cols contain float values for a number of things i can identify in an image, but i need to get the nearest pixel for each of them, and than to make sure I only get the unique points, and no duplicates. The problem is that this code is ugly and as far as I get it, as unpythonic as it gets. If there would be a pure-numpy-solution (without for-loops) that would be even better. # next part is to make sure that we get the rounding done correctly, and than to get the integer part out of it # without the annoying floatingpoint-error, and without duplicates fielddic={} for i in range(len(dem_rows)): # here comes the ugly part: abusing the fact that i overwrite dictionary keys if I get duplicates fielddic[int(round(dem_rows[i]) + 0.1), int(round(dem_cols[i]) + 0.1)] = None # also very ugly: to make two arrays of integers out of the first and second part of the keys field_rows = numpy.zeros((len(fielddic.keys())), int) field_cols = numpy.zeros((len(fielddic.keys())), int) for i, (r, c) in enumerate(fielddic.keys()): field_rows[i] = r field_cols[i] = c

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Better data-structure design

- by Tempname

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How do I marshal a pointer to an array of pointers to structures?

- by Daniel Stutzbach

I have a C function with the following signature: int my_function(int n, struct player **players) players is a pointer to an array of pointers to struct player objects. n is the number of pointers in the array. The function does not modify the array nor the contents of the structures, and it does not retain any pointers after returning. I tried the following: [DllImport("mylibary.dll")] static extern int my_function(int n, [In, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 0)] player_in []players); However, that marshals the data as a pointer to an array of structures, not a pointer to an array of pointers to structures.

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Is scala's cake pattern possible with parametrized components?

- by Nicolas

Parametrized components work well with the cake pattern as long as you are only interested in a unique component for each typed component's, example: trait AComponent[T] { val a:A[T] class A[T](implicit mf:Manifest[T]) { println(mf) } } class App extends AComponent[Int] { val a = new A[Int]() } new App Now my application requires me to inject an A[Int] and an A[String], obviously scala's type system doesn't allow me to extends AComponent twice. What is the common practice in this situation ?

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How can I detect endianness on a system where all primitive integer sizes are the same?

- by Joe Wreschnig

(This question came out of explaining the details of CHAR_BIT, sizeof, and endianness to someone yesterday. It's entirely hypothetical.) Let's say I'm on a platform where CHAR_BIT is 32, so sizeof(char) == sizeof(short) == sizeof(int) == sizeof(long). I believe this is still a standards-conformant environment. The usual way to detect endianness at runtime (because there is no reliable way to do it at compile time) is to make a union { int i, char c[sizeof(int)] } x; x.i = 1 and see whether x.c[0] or x.c[sizeof(int)-1] got set. But that doesn't work on this platform, as I end up with a char[1]. Is there a way to detect whether such a platform is big-endian or little-endian, at runtime? Obviously it doesn't matter inside this hypothetical system, but one can imagine it is writing to a file, or some kind of memory-mapped area, which another machine reads and reconstructs it according to its (saner) memory model.

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Can this example be done with pointers instead of global variable?

- by Louise

This is a simplified example of the problem I have: #include <stdio.h> #include <stdlib.h> void f2(int** a) { printf("a: %i\n", **a); } void f1(int* a) { f2(&a); } int main() { int a = 3; f1(&a); // prints "a: 3" f2(???); return 0; } The problem is that I would like to be able to use f2() both in main() and in f1(). Can that be done without using global variables?

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Adding the sum of numbers using a loop statement

- by Deonna

I need serious help dividing the positive numbers and the negative numbers. I am to accumulate the total of the negative values and separately accumulate the total of the positive values. After the loop, you are then to display the sum of the negative values and the sum of the positive values. The data is suppose to look like this: -2.3 -1.9 -1.5 -1.1 -0.7 -0.3 0.1 0.5 0.9 1.3 1.7 2.1 2.5 2.9 Sum of negative values: -7.8 Sum of positive values: 12 So far I have this: int main () { int num, num2, num3, num4, num5, sum, count, sum1; int tempVariable = 0; int numCount = 100; int newlineCount = 0, newlineCount1 = 0; float numCount1 = -2.3; while (numCount <= 150) { cout << numCount << " "; numCount += 2; newlineCount ++; if(newlineCount == 6) { cout<< " " << endl; newlineCount = 0; } } **cout << "" << endl; while (numCount1 <=2.9 ) { cout << numCount1 << " "; numCount1 += 0.4; newlineCount1 ++; } while ( newlineCount1 <= 0 && newlineCount >= -2.3 ); cout << "The sum is " << newlineCount1 << endl;** return 0; }

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typedef declaration syntax

- by mt_serg

Some days ago I looked at boost sources and found interesting typedef. There is a code from "boost\detail\none_t.hpp": namespace boost { namespace detail { struct none_helper{}; typedef int none_helper::*none_t ; } // namespace detail } // namespace boost I didn't see syntax like that earlier and can't explain the sense of that. This typedef introduces name "none_t" as pointer to int in boost::detail namespace. What the syntax is? And what difference between "typedef int none_helper::*none_t" and for example "typedef int *none_t" ?

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Showing an image after loading it from sql database

- by user330075

I have a problem showing the image form database in a view Details and a ImageController. Inside the view I have: img src=Url.Action("GetFile","Image", new {id= Model.id}) and in controller: public FileContentResult GetFile(int idl) { //int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } When the view is called, function GetFile it just won't work. But if I cut out the parameter int id1 and I instantiate it as a variable it does work. public FileContentResult GetFile() { int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } Why?

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Is it necessarily bad style to ignore the return value of a method

- by Jono

Let's say I have a C# method public void CheckXYZ(int xyz) { // do some operation with side effects } Elsewhere in the same class is another method public int GetCheckedXYZ(int xyz) { int abc; // functionally equivalent operation to CheckXYZ, // with additional side effect of assigning a value to abc return abc; // this value is calculated during the check above } Is it necessarily bad style to refactor this by removing the CheckXYZ method, and replacing all existing CheckXYZ() calls with GetCheckedXYZ(), ignoring the return value? The returned type isn't IDisposable in this case. Does it come down to discretion?

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Boost threading/mutexs, why does this work?

- by Flamewires

Code: #include <iostream> #include "stdafx.h" #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> using namespace std; boost::mutex mut; double results[10]; void doubler(int x) { //boost::mutex::scoped_lock lck(mut); results[x] = x*2; } int _tmain(int argc, _TCHAR* argv[]) { boost::thread_group thds; for (int x = 10; x>0; x--) { boost::thread *Thread = new boost::thread(&doubler, x); thds.add_thread(Thread); } thds.join_all(); for (int x = 0; x<10; x++) { cout << results[x] << endl; } return 0; } Output: 0 2 4 6 8 10 12 14 16 18 Press any key to continue . . . So...my question is why does this work(as far as i can tell, i ran it about 20 times), producing the above output, even with the locking commented out? I thought the general idea was: in each thread: calculate 2*x copy results to CPU register(s) store calculation in correct part of array copy results back to main(shared) memory I would think that under all but perfect conditions this would result in some part of the results array having 0 values. Is it only copying the required double of the array to a cpu register? Or is it just too short of a calculation to get preempted before it writes the result back to ram? Thanks.

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Passing an empty IEnumerable argument to a method

- by avance70

I have this method (simplified): void DoSomething(IEnumerable<int> numbers); And I invoke it like this: DoSomething(condition==true?results:new List<int>()); The variable results is formed with a LINQ select condition (IEnumerable). I was wondering is this List<int>() the best way (the fastest?) to pass an empty collection, or is new int[0] better? Or, something else would be faster, a Collection, etc.? In my example null wouldn't be ok.

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I can't set main Class variable in onCreate Method

- by natrollus

Main class has two variables that want to reach another class: public class MyClassA extends Activity { int i = 1; Button b1; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); this.i = 31; this.b1 = (Button) findViewById(R.id.btn1); ~~ } } Second class want to call variables in mainClass object: public class MyclassB implements OnClickListener{ MyClassA mainClass = new MyClassA(); Button btn = mainClass.b1; int n = mainClass.i; public void OnClick(View arg0){ Log.v("btn:",btn); Log.v("int:",n); } //btn returns null; //int returns 1; But onCreate method not set variables.. Why not set main class variables like this.i=31 ?

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MySQL Removing Some Foreign keys

- by Drew

I have a table whose primary key is used in several other tables and has several foreign keys to other tables. CREATE TABLE location ( locationID INT NOT NULL AUTO_INCREMENT PRIMARY KEY ... ) ENGINE = InnoDB; CREATE TABLE assignment ( assignmentID INT NOT NULL AUTO_INCREMENT PRIMARY KEY, locationID INT NOT NULL, FOREIGN KEY locationIDX (locationID) REFERENCES location (locationID) ... ) ENGINE = InnoDB; CREATE TABLE assignmentStuff ( ... assignmentID INT NOT NULL, FOREIGN KEY assignmentIDX (assignmentID) REFERENCES assignment (assignmentID) ) ENGINE = InnoDB; The problem is that when I'm trying to drop one of the foreign key columns (ie locationIDX) it gives me an "ERROR 1025 (HY000): Error on rename" error. How can I drop the column in the assignment table above without getting this error?

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Optional parameters for interfaces

- by bryanjonker

Using c# 4.0 -- building an interface and a class that implements the interface. I want to declare an optional parameter in the interface and have it be reflected in the class. So, I have the following: public interface IFoo { void Bar(int i, int j=0); } public class Foo { void Bar(int i, int j=0) { // do stuff } } This compiles, but it doesn't look right. The interface needs to have the optional parameters, because otherwise it doesn't reflect correctly in the interface method signature. Should I skip the optional parameter and just use a nullable type? Or will this work as intended with no side effects or consequences?

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Converting text into numeric in xls using Java

- by Work World

When I create excel sheet through java ,the column which has number datatype in the oracle table, get converted to text format in excel.I want it to remain in the number format.Below is my code snippet for excel creation. FileWriter fw = new FileWriter(tempFile.getAbsoluteFile(),true); // BufferedWriter bw = new BufferedWriter(fw); HSSFWorkbook wb = new HSSFWorkbook(); HSSFSheet sheet = wb.createSheet("Excel Sheet"); //Column Size of excel for(int i=0;i<10;i++) { sheet.setColumnWidth((short) i, (short)8000); } String userSelectedValues=result; HSSFCellStyle style = wb.createCellStyle(); ///HSSFDataFormat df = wb.createDataFormat(); style.setFillForegroundColor(HSSFColor.GREY_25_PERCENT.index); style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND); //style.setDataFormat(df.getFormat("0")); HSSFFont font = wb.createFont(); font.setColor(HSSFColor.BLACK.index); font.setBoldweight((short) 700); style.setFont(font); int selecteditems=userSelectedValues.split(",").length; // HSSFRow rowhead = sheet.createRow((short)0); //System.out.println("**************selecteditems************" +selecteditems); for(int k=0; k<selecteditems;k++) { HSSFRow rowhead = sheet.createRow((short)k); if(userSelectedValues.contains("O_UID")) { HSSFCell cell0 = rowhead.createCell((short) k); cell0.setCellValue("O UID"); cell0.setCellStyle(style); k=k+1; } ///some columns here.. } int index=1; for (int i = 0; i<dataBeanList.size(); i++) { odb=(OppDataBean)dataBeanList.get(i); HSSFRow row = sheet.createRow((short)index); for(int j=0;j<selecteditems;j++) { if(userSelectedValues.contains("O_UID")) { row.createCell((short)j).setCellValue(odb.getUID()); j=j+1; } } index++; } FileOutputStream fileOut = null; try { fileOut = new FileOutputStream(path.toString()+"/temp.xls"); } catch (FileNotFoundException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } try { wb.write(fileOut); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } try { fileOut.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

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Database Structure for CakePHP Models

- by Michael T. Smith

We're building a data tracking web app using CakePHP, and I'm having some issues getting the database structure right. We have Companies that haveMany Sites. Sites haveMany DataSamples. Tags haveAndBelongToMany Sites. That is all set up fine. The problem is "ranking" the sites within tags. We need to store it in the database as an archive. I created a Rank model that is setup like this: rank ( id (int), sample_id (int), tag_id (int), site_id (int), rank (int), total_rows) ) So, the question is, how do I create the associations for tag, site and sample to rank? I originally set them as haveMany. But the returned structures don't get me where I'd like to be. It looks like: [Site] => Array ( [Sample] = Array(), [Tag] = Array() ) When I'm really looking for: [Site] => Array ( [Tag] = Array ( [Sample] => Array ( [Rank] => Array ( ...data... ) ) ) ) I think that I may not be structuring the database properly; so if I need to update please let me know. Otherwise, how do I write a find query that gets me where I need to be? Thanks! Thoughts? Need more details? Just ask!

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Merge n files using a C program

- by Amal

I am writing a download Accelerator. So I download a file from the webserver into n parts. Now I want to merge the files into 1 single file. So I use the following code. And the file names are in the correct order. But the output file I am getting is different from the original download file. Can you tell me where could the error be ?C int cbd_merge_files(const char** filenames, int n, const char* final_filename) { FILE* fp = fopen(final_filename, "wb"); if (fp == NULL) return 1; char buffer[4097]; for (int i = 0; i < n; ++i) { const char* fname = filenames[i]; FILE* fp_read = fopen(fname, "rb"); if (fp_read == NULL) return 1; int n; while ((n = fread(buffer, sizeof(char), 4096, fp_read))) { int k = fwrite(buffer, sizeof(char), n, fp); if (!k) return 1; } fclose(fp_read); } fclose(fp); return 0; }

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Final enum in Thread's run() method

- by portoalet

Hi, Why is the Elvis elvis definition has to be final to be used inside the Thread run() method? Elvis elvis = Elvis.INSTANCE; // ----> should be final Elvis elvis = Elvis.INSTANCE elvis.sing(4); Thread t1 = new Thread( new Runnable() { @Override public void run() { elvis.sing(6); // --------> elvis has to be final to compile } } ); public enum Elvis { INSTANCE(2); Elvis() { this.x = new AtomicInteger(0); } Elvis(int x){ this.x = new AtomicInteger(x); } private AtomicInteger x = new AtomicInteger(0); public int getX() { return x.get(); } public void setX(int x) {this.x = new AtomicInteger(x);} public void sing(int x) { this.x = new AtomicInteger(x); System.out.println("Elvis singing.." + x); } }

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Does my GetEnumerator cause a deadlock?

- by Scott Chamberlain

I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. TLDR; version private object _Lock = new object(); public IEnumerator GetEnumerator() { var infoSource = myInforSource.GetEnumerator(); //Will this cause a deadlock if two threads lock (_Lock) //use the enumator at the same time? { while (infoSource.MoveNext()) { yield return infoSource.Current; } } } full code protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the MSDN example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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- by Ed

- by Jakub Czaplicki

- by bobber205

- by Emile Cormier

- by Jim Hunziker

- by usethedeathstar

- by Tempname

- by Daniel Stutzbach

- by Nicolas

- by Joe Wreschnig

- by Louise

- by Deonna

- by mt_serg

- by user330075

- by Jono

- by Flamewires

- by avance70

- by natrollus

- by Drew

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- by Work World

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