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  • Determining if Memory Pointer is Valid - C++

    - by Jim Fell
    It has been my observation that if free( ptr ) is called where ptr is not a valid pointer to system-allocated memory, an access violation occurs. Let's say that I call free like this: LPVOID ptr = (LPVOID)0x12345678; free( ptr ); This will most definitely cause an access violation. Is there a way to test that the memory location pointed to by ptr is valid system-allocated memory? It seems to me that the the memory management part of the Windows OS kernel must know what memory has been allocated and what memory remains for allocation. Otherwise, how could it know if enough memory remains to satisfy a given request? (rhetorical) That said, it seems reasonable to conclude that there must be a function (or set of functions) that would allow a user to determine if a pointer is valid system-allocated memory. Perhaps Microsoft has not made these functions public. If Microsoft has not provided such an API, I can only presume that it was for an intentional and specific reason. Would providing such a hook into the system prose a significant threat to system security? Situation Report Although knowing whether a memory pointer is valid could be useful in many scenarios, this is my particular situation: I am writing a driver for a new piece of hardware that is to replace an existing piece of hardware that connects to the PC via USB. My mandate is to write the new driver such that calls to the existing API for the current driver will continue to work in the PC applications in which it is used. Thus the only required changes to existing applications is to load the appropriate driver DLL(s) at startup. The problem here is that the existing driver uses a callback to send received serial messages to the application; a pointer to allocated memory containing the message is passed from the driver to the application via the callback. It is then the responsibility of the application to call another driver API to free the memory by passing back the same pointer from the application to the driver. In this scenario the second API has no way to determine if the application has actually passed back a pointer to valid memory.

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  • How to read the file

    - by muruga
    I want to get the file from one host to another host. We can get the file using the NET::FTP module. In that module we can use the get method to get the file.But I want the file content instead of the file. I know that using the read method we can read the file content. But how to call the read function and how to get the file content. Please help me.

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  • Best Practice: Direct SQL Access vs. Web Service

    - by phsr
    With respect to an application that has both a web and desktop client version: What is the best practice for the desktop client which needs access to a SQL Server? What are the benefits of connecting to the database from the application vs using a web service? Which one provides better security? What type of scope would call for one vs the other (enterprise intranet vs. web app, etc) Are there any other considerations that are necessary when choosing on platform?

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  • Why does this python code work?

    - by Int-0
    I have written a simple python module, it has this code: _log = logging.getLogger("mymodule") _started = False def set_log_level(level): _log.setLevel(level) if not _started: _hdlr = logging.FileHandler('mymodule.log') When I call set_log_level() program fails because symbol _started is not found. It is normal because global _started is missing in the method. But my question is: symbol _log has the same visibility as _started, so why does this symbol can be found? BR, // Toby

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  • What kind of language is CSS?

    - by Derek Adair
    What kind of language is CSS? My first inclination was to call it a markup language... but it doesn't really fit the mold. Edit: A markup language is a system for annotating a text in a way which is syntactically distinguishable from that text. -wikipedia CSS uses various selectors to apply properties to elements within HTML, a markup language

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  • iPhone memory management, a newbie question

    - by Reuven
    Hi, I've seen in (Apple) sample code two types of ways of allocation memory, and am not sure I understand the difference and resulting behavior. // FAILS NSMutableArray *anArray = [NSMutableArray array]; [anArray release]; // WORKS NSMutableArray *anArray1 = [[NSMutableArray alloc] init]; [anArray release]; By "FAILS" I mean I get crashes/runtime warnings etc., and not always as soon as I call the release... Any explanation appreciated. Thanks

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  • Unable to open images with Python's Image.open()

    - by ensnare
    My code reads: import Image def generateThumbnail(self, width, height): """ Generates thumbnails for an image """ im = Image.open(self._file) When I call this function, I get an error: ? AttributeError: type object 'Image' has no attribute 'open' However in the console: import Image im = Image.open('test.jpg') I have no problem. Any ideas? Thanks!

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  • Where does abort() and terminate() "live"?

    - by user325016
    Regarding the terminate handler, As i understand it, when something bad happens in code, for example when we dont catch an exception, terminate() is called, which in turn calls abort() set_terminate(my_function) allows us to get terminate() to call a user specified function my_terminate. my question is: where do these functions "live" they don't seem to be a part of the language, but work as if they are present in every single cpp file, without having to include any header file.

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  • Passing a filepath to a R function?

    - by Philipp
    Hi everybody, I tried to pass a filepath to a function in R, but I failed =/ I hope someone here can help me. >heat <- function(filepath) { chicks <- read.table(file=filepath, dec=",", header=TRUE, sep="\t") ... } When I call the function, nothing happens... >heat("/home/.../file.txt") ... and "chicks" is not found >chicks Error: Object 'chicks' not found What is the correct way to pass a path to a function? Best wishes from Germany, Phil

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  • XMLEncoder in java for serialization

    - by tom
    Im just wondering how i use xmlencoder to serialize ArrayList where foo is my own made class. Do i have to do anything in particular, ie define my own xml structure first and then call toString on each value in my list and write it out? Can anyone point me to a good tutorial? http://java.sun.com/products/jfc/tsc/articles/persistence4/ Thats what i have been looking at but it doesnt seem to mention what to do with non library classes. Thanks

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  • My Oracle 9i package won't compile, says that a user-defined function is out of scope... but it isn'

    - by bitstream
    I have an Oracle package which contains user-defined functions and procedures, including two user-defined functions which are called from SELECT and UPDATE statements. The functions in question are defined before the procedures that call them. This piece of code compiles and works fine on Oracle 10g but won't compile on 9i. The code should work as-is according to Oracle's own documentation. Any idea why it would throw this error on 9i?

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  • Time is updating when a form is not even running

    - by onaclov2000
    A co-worker of mine had downloaded a vb example project a while back to see how to make a call or two, he discovered it today again, and noticed that while sitting in the IDE the time/date is updating automatically when the entire project is not even running. How does this work, we looked around for code but can't find anything giving it away. Any ideas?

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  • F# mutual recursion between modules

    - by rwallace
    For recursion in F#, existing documentation is clear about how to do it in the special case where it's just one function calling itself, or a group of physically adjacent functions calling each other. But in the general case where a group of functions in different modules need to call each other, how do you do it?

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  • Manipulating DisplayMember before it is displayed

    - by DanDan
    Let's say I am using databinding like this: List<Entity> Entities = <some data> entityBinding.DataSource = Entities; lstEntities.DisplayMember = "Description"; which works fine. However, I want to manipulate the string coming back as the Entity's "Description". How can I call a function on DisplayMember?

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  • How to get the value of the input element of live of Value

    - by Aruna
    HI, i am having a Input hidden element like in my JQuery i am setting the value for the above input type after some ajax call like EDIT::: $.ajax({ type: "POST", url: "http://localhost/FormBuilder/index.php/forms/saveForm/", async: false, data: "formname="+formname+"&status="+status, success: function(msg){$("#FormID").val(msg); }//success });//ajax Now somewhere in the code after this i want to fetch the value of this FIeld.How to get this value on live of value for this input type.. EDIT::: i am retriving like by var FORMID=$("#FormID").val();//but shows null How to get the value of it on live of this Input element

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