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  • Designing an API with compile-time option to remove first parameter to most functions and use a glob

    - by tomlogic
    I'm trying to design a portable API in ANSI C89/ISO C90 to access a wireless networking device on a serial interface. The library will have multiple network layers, and various versions need to run on embedded devices as small as an 8-bit micro with 32K of code and 2K of data, on up to embedded devices with a megabyte or more of code and data. In most cases, the target processor will have a single network interface and I'll want to use a single global structure with all state information for that device. I don't want to pass a pointer to that structure through the network layers. In a few cases (e.g., device with more resources that needs to live on two networks) I will interface to multiple devices, each with their own global state, and will need to pass a pointer to that state (or an index to a state array) through the layers. I came up with two possible solutions, but neither one is particularly pretty. Keep in mind that the full driver will potentially be 20,000 lines or more, cover multiple files, and contain hundreds of functions. The first solution requires a macro that discards the first parameter for every function that needs to access the global state: // network.h typedef struct dev_t { int var; long othervar; char name[20]; } dev_t; #ifdef IF_MULTI #define foo_function( x, a, b, c) _foo_function( x, a, b, c) #define bar_function( x) _bar_function( x) #else extern dev_t DEV; #define IFACE (&DEV) #define foo_function( x, a, b, c) _foo_function( a, b, c) #define bar_function( x) _bar_function( ) #endif int bar_function( dev_t *IFACE); int foo_function( dev_t *IFACE, int a, long b, char *c); // network.c #ifndef IF_MULTI dev_t DEV; #endif int bar_function( dev_t *IFACE) { memset( IFACE, 0, sizeof *IFACE); return 0; } int foo_function( dev_t *IFACE, int a, long b, char *c) { bar_function( IFACE); IFACE->var = a; IFACE->othervar = b; strcpy( IFACE->name, c); return 0; } The second solution defines macros to use in the function declarations: // network.h typedef struct dev_t { int var; long othervar; char name[20]; } dev_t; #ifdef IF_MULTI #define DEV_PARAM_ONLY dev_t *IFACE #define DEV_PARAM DEV_PARAM_ONLY, #else extern dev_t DEV; #define IFACE (&DEV) #define DEV_PARAM_ONLY void #define DEV_PARAM #endif int bar_function( DEV_PARAM_ONLY); // I don't like the missing comma between DEV_PARAM and arg2... int foo_function( DEV_PARAM int a, long b, char *c); // network.c #ifndef IF_MULTI dev_t DEV; #endif int bar_function( DEV_PARAM_ONLY) { memset( IFACE, 0, sizeof *IFACE); return 0; } int foo_function( DEV_PARAM int a, long b, char *c) { bar_function( IFACE); IFACE->var = a; IFACE->othervar = b; strcpy( IFACE->name, c); return 0; } The C code to access either method remains the same: // multi.c - example of multiple interfaces #define IF_MULTI #include "network.h" dev_t if0, if1; int main() { foo_function( &if0, -1, 3.1415926, "public"); foo_function( &if1, 42, 3.1415926, "private"); return 0; } // single.c - example of a single interface #include "network.h" int main() { foo_function( 11, 1.0, "network"); return 0; } Is there a cleaner method that I haven't figured out? I lean toward the second since it should be easier to maintain, and it's clearer that there's some macro magic in the parameters to the function. Also, the first method requires prefixing the function names with "_" when I want to use them as function pointers. I really do want to remove the parameter in the "single interface" case to eliminate unnecessary code to push the parameter onto the stack, and to allow the function to access the first "real" parameter in a register instead of loading it from the stack. And, if at all possible, I don't want to have to maintain two separate codebases. Thoughts? Ideas? Examples of something similar in existing code? (Note that using C++ isn't an option, since some of the planned targets don't have a C++ compiler available.)

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  • Is Catching a Null Pointer Exception a Code Smell?

    - by Drew
    Recently a co-worker of mine wrote in some code to catch a null pointer exception around an entire method, and return a single result. I pointed out how there could've been any number of reasons for the null pointer, so we changed it to a defensive check for the one result. However, catching NullPointerException just seemed wrong to me. In my mind, Null pointer exceptions are the result of bad code and not to be an expected exception in the system. Are there any cases where it makes sense to catch a null pointer exception?

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  • Android - Memory leak when dynamically building UI with image resource backgrounds

    - by Rich
    I have an Activity that I swear is leaking memory. The app I'm working on does a lot with images, so I've had to be pretty stingy with memory when working directly with Bitmaps. I added an Activity, and now if you use this new Activity it basically puts me over the edge with mem usage and I end up throwing the "Bitmap exceeds VM budget" exception. If you never launch this Activity, everything is smooth as it was previously. I started reading about memory leaks, and I think that I have a similar situation to what is described in the article in the Android docs. I'm dynamically creating a bunch of image views and adding a BackgroundDrawable from the resources and adding an OnClickListener as well. I imagine I have to do some cleanup when the Activity hits onPause in its life cycle, but I'd like to know specifically what is the correct way. Here is the code that should demonstrate the objects I'm working with... LinearLayout templateContainer; . . . ImageView imgTemplatePreview = (ImageView) item.findViewById(R.id.imgTemplatePreview); . . . imgTemplatePreview.setBackgroundDrawable(getResources().getDrawable(previewId)); imgTemplatePreview.setOnClickListener(imgClick); templateContainer.addView(item);

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  • Programmatic Text Wrapping in TextView

    - by Andrew
    I'm working on a custom widget for my application to replicate the look of a Preference button for layouts. The issue is the 'summary' text wont wrap when it hits the right wall of the view. One of the goals I'm trying to keep is that this widget is completely made from java with no xml attributes. here's what the widget looks like at the moment: http://dl.dropbox.com/u/56017670/Screenshot_2012-09-05-17-22-45.png notice that the middle two don't wrap the text but the text obviously runs right off the edge of the widget below is the code I'm using to create the text view. public void setSummary(String summary) { if (!TextUtils.isEmpty(summary)) { if (mSummaryView == null) { mSummaryView = new TextView(mContext); mSummaryView.setTextSize(14); mSummaryView.setTextColor(mContext.getResources().getColor( android.R.color.tertiary_text_dark)); addView(mSummaryView); } mSummaryView.setText(summary); mSummaryView.setVisibility(View.VISIBLE); } else { if (mSummaryView != null) { mSummaryView.setVisibility(View.GONE); } } mSummaryText = summary; } and here is the code I'm using to layout mSummaryView mSummaryView.layout( mPreferencePadding + mIconWidth, centerVertical + (mCombinedTextHeight / 2) - mSummaryHeight, width - mPreferencePadding, centerVertical + (mCombinedTextHeight / 2)); I've tried to add mSummaryView.setSingleLine(false); along with quite a few other tricks but they all ended in the same way.

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  • Make function declarations based on function definitions

    - by Clinton Blackmore
    I've written a .cpp file with a number of functions in it, and now need to declare them in the header file. It occurred to me that I could grep the file for the class name, and get the declarations that way, and it would've worked well enough, too, had the complete function declaration before the definition -- return code, name, and parameters (but not function body) -- been on one line. It seems to me that this is something that would be generally useful, and must've been solved a number of times. I am happy to edit the output and not worried about edge cases; anything that gives me results that are right 95% of the time would be great. So, if, for example, my .cpp file had: i2cstatus_t NXTI2CDevice::writeRegisters( uint8_t start_register, // start of the register range uint8_t bytes_to_write, // number of bytes to write uint8_t* buffer = 0) // optional user-supplied buffer { ... } and a number of other similar functions, getting this back: i2cstatus_t NXTI2CDevice::writeRegisters( uint8_t start_register, // start of the register range uint8_t bytes_to_write, // number of bytes to write uint8_t* buffer = 0) for inclusion in the header file, after a little editing, would be fine. Getting this back: i2cstatus_t writeRegisters( uint8_t start_register, uint8_t bytes_to_write, uint8_t* buffer); or this: i2cstatus_t writeRegisters(uint8_t start_register, uint8_t bytes_to_write, uint8_t* buffer); would be even better.

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  • Function return type style

    - by JB
    I'm learning c++0x, at least the parts supported by the Visual C++ Express 2010 Beta. This is a question about style rather than how it works. Perhaps it's too early for style and good practice to have evolved yet for a standard that isn't even released yet... In c++0x you can define the return type of a method using - type at the end of the function instead of putting the type at the start. I believe this change in syntax is required due to lambdas and some use cases of the new decltype keyword, but you can use it anywhere as far as I know. // Old style int add1(int a, int b) { return a + b; } // New style return type auto add2(int a, int b) -> int { return a + b; } My question really then, is given that some functions will need to be defined in the new way is it considered good style to define all functions in this way for consistency? Or should I stick to only using it when necessary?

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  • Regex to match pattern with subdomain in java gives issues

    - by Ramesh
    I am trying to match the sub domain of an url using http://([a-z0-9]*.)?example.com/.* which works perfectly for these cases. http://example.com/index.html http://test.example.com/index.html http://test1.example.com/index.html http://www.example.com/122/index.html But the problem is it matches for this URL too. http://www.test.com/?q=http://example.com/index.html if an URL with another domain has the URL in path it matches.Can any one tell me how to match for current domain only. getting the host will work but i need to match full URL.

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  • Positioning objects in views during re-orientation in iPad

    - by Arni
    iPad Gurus: Apple wants us to support all orientations. I take that to mean that a particular layout should either rotate so that all objects are positioned relatively the same OR, if that doesn't look good, then they ought to be repositioned, OR two views ought to be designed and built. If I rely on the built-in rotation mechanism, the objects either get resized or they straddle the edge of the page in one orientation or the other, or they disappear from view altogether. I can't seem to find the right settings to get the objects to align clearly so they are seen in each orientation. Repositioning leads to a lot of if statements in the View Controller. So I don't think Apple had that in mind. I tried replacing views and even view controllers in "willRotateToInterfaceOrientation" method, but that either causes crashes or the portrait views end up in landscape unexpectedly and vv. Moreover, two view controllers means double the coding for the same view. There must be proper way to handle orientation changes, but I have searched the internet and documentation and sample code in vain for something that works. How is this done properly? Thanks!

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  • Are there any context-sensitive code search tools?

    - by Vicky
    I have been getting very frustrated recently in dealing with a massive bulk of legacy code which I am trying to get familiar with. Say I try to search for a particular function call, I get loads of results that turn out to be completely irrelevant; some of them are easy to spot, eg a comment saying // Fixed functionality in foo() so don't need to handle this here any more But others are much harder to spot manually, because they turn out to be calls from other functions in modules that are only compiled in certain cases, or are part of a much larger block of code that is #if 0'd out in its entirety. What I'd like would be a search tool that would allow me to search for a term and give me the choice to include or exclude commented out or #if 0'd out code. Then the search results would be displayed alongside a list of #defines that are required in order for that snippet of code to be relevant. I'm working in C / C++, but other than the specific comment syntax I guess the techniques should be more generally applicable. Does such a tool exist?

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  • Instance where embedded C++ compilers don't support multiple inheritance?

    - by Nathan
    I read a bit about a previous attempt to make a C++ standard for embedded platforms where they specifically said multiple inheritance was bad and thus not supported. From what I understand, this was never implemented as a mainstream thing and most embedded C++ compilers support most standard C++ constructs. Are there cases where a compiler on a current embedded platform (i.e. something not more than a few years old) absolutely does not support multiple inheritance? I don't really want to do multiple inheritance in a sense where I have a child with two full implementations of a class. What I am most interested in is inheriting from a single implementation of a class and then also inheriting one or more pure virtual classes as interfaces only. This is roughly equivalent to Java/.Net where I can extend only one class but implement as many interfaces as I need. In C++ this is all done through multiple inheritance rather than being able to specifically define an interface and declare a class implements it.

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  • Undefined behaviour with non-virtual destructors - is it a real-world issue?

    - by Roddy
    Consider the following code: class A { public: A() {} ~A() {} }; class B: public A { B() {} ~B() {} }; A* b = new B; delete b; // undefined behaviour My understanding is that the C++ standard says that deleting b is undefined behaviour - ie, anything could happen. But, in the real world, my experience is that ~A() is always invoked, and the memory is correctly freed. if B introduces any class members with their own destructors, they won't get invoked, but I'm only interested in the simple kind of case above, where inheritance is used maybe to fix a bug in one class method for which source code is unavailable. Obviously this isn't going to be what you want in non-trivial cases, but it is at least consistent. Are you aware of any C++ implementation where the above does NOT happen, for the code shown?

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  • How to fight fake reviewers on iTunes?

    - by Tiger
    Hi my app "Vocal Zoo Plus" is under attak of fake reviews by a competitor Apple did nothing in similar cases and I don't even have a usa account Any id'e how to fight them? I will willingly give promocodes for my app if someone would like to help the fight and write a true review but that would only help me at usa since the attack is coming from UK as well all other reviews by the way are 5 stars The reviewer who gave me one star with false bugs happend to rate 5 star for this competitor Apps. Any advice / help will be apriciated.

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  • How to handle inaccurate Google Maps locations?

    - by Azzizz81
    When I type in addresses in Google maps for locations in Asia, quite a lot of them are off by more than 200 metres. For example, "blk 85 bedok north road, singapore" is off by more than 300 metres. While I don't expect Google Maps to be spot on every time, sometimes the error is too great for certain use cases. What options do I have to handle inaccurate Google Maps locations in a web app? The web app should let the user enter an address or postal code as part of an entry and I will geocode the address and store the lat-long.

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  • Qt/C++ event loop exception handling

    - by Georg
    I am having an application heavily based on QT and on a lot of third party libs. THese happen to throw some exceptions in several cases. In a native Qt App this causes the application to abort or terminate. Often the main data model is still intact as I am keeping it in pure Qt with no external data. So I am thinking that I could also just recover by telling the user that there has occured an error in this an that process and he should save now or even decide to continue working on the main model. Currently the program jsut silently exits without even telling a story. Please help.

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  • better for-loop syntax for detecting empty sequences?

    - by Dmitry Beransky
    Hi, Is there a better way to write the following: row_counter = 0 for item in iterable_sequence: # do stuff with the item counter += 1 if not row_counter: # handle the empty-sequence-case Please keep in mind that I can't use len(iterable_sequence) because 1) not all sequences have known lengths; 2) in some cases calling len() may trigger loading of the sequence's items into memory (as the case would be with sql query results). The reason I ask is that I'm simply curious if there is a way to make above more concise and idiomatic. What I'm looking for is along the lines of: for item in sequence: #process item *else*: #handle the empty sequence case (assuming "else" here worked only on empty sequences, which I know it doesn't)

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  • Check if edit is valid for database ms-access

    - by twodayslate
    I want to be able to check if I can edit a cell in a database with a new object Example method declaration: something.isValid(Object newObject, row, column); Example cases: If the editing cell stores an Number and I give it a String, the method will return false... If the editing cell has to be different than every other entry and the new object is the same as something else, the method will also return false.... My main goal... I want to check a whole row, and if everything is valid, I will edit the whole row. Right now, the only way I can find out if I can actually edit something is by actually editing it and seeing if I get an error.

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  • How to switch iostream from binary to text mode and vice versa?

    - by Mad Fish
    I want to read both formatted text and binary data from the same iostream. How can I do that? Why? Imagine this situation: You have different resources, and resource loaders for them, that take a std::istream as a parameter. And there are a "resource source" that provides these streams. Resources can be both text and binary and I need to handle both cases with resource loaders. Or other situation: Image that you have an archive with resources of mixed types. How can I get a text stream from inside the binary archive stream?

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  • check if a tree is complete standard ml

    - by aizen92
    I want to make a function in standard ml that checks if a tree is complete or not, the function somehow works, but its giving me the wrong type and a warning of non-exhaustive cases The tree code: datatype 'data tree = EMPTY | NODE of 'data tree * 'data * 'data tree; fun isComplete EMPTY = true | isComplete (NODE(x, y, z)) = if (x = EMPTY andalso z <> EMPTY) orelse (x <> EMPTY andalso z = EMPTY) then false else true; Now the above function's type is: ''a tree -> bool but the required type is 'a tree -> bool The warning I'm having is: stdIn:169.8 Warning: calling polyEqual stdIn:169.26 Warning: calling polyEqual stdIn:169.45-169.47 Warning: calling polyEqual stdIn:169.64-169.66 Warning: calling polyEqual stdIn:124.1-169.94 Warning: match nonexhaustive NODE (x,y,z) => ... What is the problem I'm having?

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  • Need some explanation about MS Ajax using PageMethods

    - by Ahmed Said
    I have a project that uses PageMethods to call functions on the server. The server functions (written in C#) return the values as array of strings, without doing any kind of serialization and in the client side (from Js) the accessing of the return values is by using static variable called arguments. I found that sometimes for some users (cases are not repro) sometimes an exception occured "WebServiceFailedException the server method 'Foo' returned invalid data. the 'd' property is missing from JSON." Some searching on google I found that people are serializing the return values using DataContractJsonSerializer class and in js accessing the return value using one of the callback function Example: function OnRequestComplete(result, userContext, methodName) { var Person = eval('(' + result + ')'); alert(Person.Forename); alert(Person.Surname); } So is the first technique is correct? or what?

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  • NHibernate: What are child sessions and why and when should I use them?

    - by stefando
    In the comments for the ayende's blog about the auditing in NHibernate there is a mention about the need to use a child session:session.GetSession(EntityMode.Poco). As far as I understand it, it has something to do with the order of the SQL operation which session.Flush will emit. (For example: If I wanted to perform some delete operation in the pre-insert event but the session was already done with deleting operations, I would need some way to inject them in.) However I did not find documentation about this feature and behavior. Questions: Is my understanding of child sessions correct? How and in which scenarios should I use them? Are they documented somewhere? Could they be used for session "scoping"? (For example: I open the master session which will hold some data and then I create 2 child-sessions from the master one. I'd expect that the two child-scopes will be separated but the will share objects from the master session cache. Is this the case?) Are they first class citizens in NHibernate or are they just hack to support some edge-case scenarios? Thanks in advance for any info.

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  • Ignoring characters in a file while parsing

    - by sfactor
    i need to parse through a text file and process the data. the valid data is usually denoted by either a timestamp with TS followed by 10 numbers (TS1040501134) or values with a alpabet followed by nine numbers (A098098098)...so it will be like TS1040501134A111111111B222222222...........TS1020304050A000000000........ However, there are cases when there will be filler 0s when there is no data. So, such a case might be 00000000000000000000TS1040501134A111111111B2222222220000000000TS1020304050A000000000........` Now as we can see I need to ignore these zeros. how might i do this? I am using gnu C.

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  • Proper thread termination in multi-threaded C# application

    - by Brian
    I have what I think is a rather complex problem. I have a C# application that utilizes a plug-in architecture using reflection. The application loads plug-in dlls and the user is able to enable/disable them. When a plug-in is enabled, the main app starts a thread to run the plug-in in. In many cases the plug-in may have multiple threads of its own. When I want to disable a plug-in I am calling Thread.Abort(). This seems to kill the initial thread that was created for the plug-in, but any additional threads that the plug-in created continue running. Is there a better way to stop all of the associated plug-in's threads along with the main thread? Thanks.

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  • Reusing of a PreparedStatement between methods?

    - by MRalwasser
    We all know that we should rather reuse a JDBC PreparedStatement than creating a new instance within a loop. But how to deal with PreparedStatement reuse between different method invocations? Does the reuse-"rule" still count? Should I really consider using a field for the PreparedStatement or should I close and re-create the prepared statement in every invocation? (Of course an instance of such a class would be bound to a Connection which might be a disadvantage) I am aware that the ideal answer might be "it depends". But I am looking for a best practice for less experienced developers that they will do the right choice in most of the cases.

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  • Symfony 1.3: different form filters generated

    - by user248959
    Hi, i have this class in rs1/lib/filter/doctrine/FelizFormFilter.class.php <?php /** * Feliz filter form. * * @package rs * @subpackage filter * @author Your name here * @version SVN: $Id: sfDoctrineFormFilterTemplate.php 23810 2009-11-12 11:07:44Z Kris.Wallsmith $ */ class FelizFormFilter extends BaseFelizFormFilter { public function configure() { } } and this in rs2/lib/filter/doctrine/FelizFormFilter.class.php <?php /** * Feliz filter form. * * @package filters * @subpackage Feliz * * @version SVN: $Id: sfDoctrineFormFilterTemplate.php 11675 2008-09-19 15:21:38Z fabien $ */ class FelizFormFilter extends BaseFelizFormFilter { public function configure() { } } Both were generated using "php symfony doctrine:build --all --and-load" and the version of symfony is 1.3.4 in both. This is the schema of both cases: Feliz: columns: name: string(20) Could you tell me why are different? One more thing in Eclipse: when i go with the mouse pointer to the word "BaseFelizFormFilter", in the second case (rs2) the yellow window with the information about the class is showed, but in the first case that yellow popup is not showed. Why? Javi

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  • How to limit the number of post values on UpdatePanel ?

    - by Aristos
    I have notice that the UpdatePanel post every field included on the form on every trigger. But in most of my cases I use 2-3 UpdatePanels at the same page, and each one is independent. When I click for update the one panel, then my page receive all the input data of the page (ok this is logical) but I won to read only this UpdatePanels data and act according, and not the other panels data. So I see that a lot of traffic is happened this way. So is there a way to say to one UpdatePanel - send only my input data, and not everything found on the page. ? Thank you in advanced.

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