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  • How to call a generic method through reflection

    - by milan
    Hi, is it possible to call with reflection a method with "explict type argument" <S> definition e.g. oObject.Cast<S>() ? where is: IList <P> oObject = new List <P>(); I tried with oObject.getType().InvokeMember( "Cast", BindingFlags.InvokeMethod, null, oObject, null) but it does not work, does anyone know why?

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  • Where am I going wrong with the count in Hql

    - by Bipul
    So I only want the count of the results not the results themselves therefore I am using count in hql. So, below is the query (int) Session.CreateQuery("select count(*) from TableName where Lhs=Rhs").UniqueResult(); But it is giving me the error Specified cast is not valid.. So, can any body tell me how to cast the count to int. Any help is very much appreciated.

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  • SQL server datetime column filter on certain date or range of dates

    - by MicMit
    There is an example for today here http://stackoverflow.com/questions/2583228/get-row-where-datetime-column-today-sql-server-noob I am primarily interested in 2008 only. For today it looked like SELECT (list of fields) FROM dbo.YourTable WHERE dateValue BETWEEN CAST(GETDATE() AS DATE) AND DATEADD(DAY, 1, CAST(GETDATE() AS DATE)) What literal value of date(s) or functions ( I need a format ) should I place there to make it work independent of local settings.

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  • minutes to time in sql server

    - by Luca Romagnoli
    i've created a function for convert minutes (smallint) in time (varchar(5)) like 58 - 00:58 set QUOTED_IDENTIFIER ON GO Create FUNCTION [dbo].[IntToMinutes] ( @m smallint ) RETURNS nvarchar(5) AS BEGIN DECLARE @c nvarchar(5) SET @c = CAST((@m / 60) as varchar(2)) + ':' + CAST((@m % 60) as varchar(2)) RETURN @c END The problem is when there are minutes < 10 in time like 9 the result of this function is 0:9 i want that the format is 00:09 how can i do that?

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  • [C++ / NCURSES] Can't convert from 'int' to 'int *'

    - by flarn2006
    So I have these lines of code: int maxY, maxX; getmaxyx(stdscr, &maxY, &maxX); It gives me the following error: error C2440: '=' : cannot convert from 'int' to 'int *' Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast twice for each time I use it. I'm not even using the = operator! The curses.h file is included. What am I doing wrong?

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  • is it possible to select EXISTS directly as a bit?

    - by jcollum
    I was wondering if it's possible to do something like this (which doesn't work): select cast( (exists(select * from theTable where theColumn like 'theValue%') as bit) Seems like it should be doable, but lots of things that should work in SQL don't ;) I've seen workarounds for this (SELECT 1 where... Exists...) but it seems like I should be able to just cast the result of the exists function as a bit and be done with it.

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  • Building up an array in numpy/scipy by iteration in Python?

    - by user248237
    Often, I am building an array by iterating through some data, e.g.: my_array = [] for n in range(1000): # do operation, get value my_array.append(value) # cast to array my_array = array(my_array) I find that I have to first build a list and then cast it (using "array") to an array. Is there a way around these? all these casting calls clutter the code... how can I iteratively build up "my_array", with it being an array from the start? thanks.

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  • Please help translate this in linq to ef

    - by user3487644
    StringBuilder sb = new StringBuilder(); sb.AppendLine("SELECT"); sb.AppendLine(String.Format(" (SELECT TOP 1 CAST(ProspectID AS VARCHAR(5)) FROM Lead_Import_Fail Where ProspectID < {0} AND ProspectFullName = '{1}')", Convert.ToInt64(lead.LeadID), lead.Name)); sb.AppendLine(String.Format(", (SELECT TOP 1 CAST(ProspectID AS VARCHAR(5)) FROM Lead_Import_Fail Where ProspectID < {0} AND ProspectNRICPassport = '{1}')", Convert.ToInt64(lead.LeadID), lead.NRIC)); Thanks in advance.

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  • Php pdo_dblib - cannot find/unable to load freetds

    - by MaxPowers
    Self-hosted box, RHEL 6 PHP 5.3.3 PDO installed freetds installed pdo_dblib - so far no luck installing My goal is to use PDO with sybase. Attempting to install pdo_dblib from the appropriate version php source code. I have tried a variety of methods and searched quite a bit for help on this topic, but have yet to be successful. Method 1 Install freetds $ ./configure $ make $ su root Password: $ make install This is successful Install pdo_dblib inside the /ext/pdo_dblib folder: $ phpize $ ./configure $ make $ make test Error output: PHP Warning: PHP Startup: Unable to load dynamic library '/home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so' - /home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so: undefined symbol: php_pdo_register_driver in Unknown on line 0 Warning: PHP Startup: Unable to load dynamic library '/home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so' - /home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so: undefined symbol: php_pdo_register_driver in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so' - /home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so: undefined symbol: php_pdo_register_driver in Unknown on line 0 Warning: PHP Startup: Unable to load dynamic library '/home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so' - /home/sybase/Install_items/php_533_src/php-5.3.3/ext/pdo_dblib/modules/pdo_dblib.so: undefined symbol: php_pdo_register_driver in Unknown on line 0 That doesn't look good...I researched this and found an interesting hack for this here. But changing pdo.ini to pdo_0.ini was not the solution, as I still got the same errors on make test. $ su $ make install Output: Installing shared extensions: /usr/lib64/php/modules/ That seems strange...and no, it doesn't actually install (not showing up on phpinfo after apache restart). Method 2 Install freetds following the instructions exactly, i add the prefix $ ./configure --prefix=/usr/local/freetds $ make $ su root Password: $ make install This is successful Install pdo_dblib inside the /ext/pdo_dblib folder: $ phpize $ ./configure --with-sybase=/usr/local/freetds This produces the following error at the bottom of the output ... checking for PDO_DBLIB support via FreeTDS... yes, shared configure: error: Cannot find FreeTDS in known installation directories Method 3 freetds ./configure variation (including or not include the --prefix...) did not change the result of this so I'll skip it. Install pdo_dblib pecl extension following the method specified here. pecl download pdo_dblib tar -xzvf PDO_DBLIB-1.0.tgz Removed the line, <dep type=”ext” rel=”ge” version=”1.0?>pdo</dep> Saved the package.xml file, and moved it in to the PDO_DBLIB directory. mv package.xml ./PDO_DBLIB-1.0 Navigated to the PDO_DBLIB directory, then installed the package from the directory. cd ./PDO_DBLIB-1.0 pecl install package.xml But, this command gives me the following error output, same as Method 2. checking for PDO_DBLIB support via FreeTDS... yes, shared configure: error: Cannot find FreeTDS in known installation directories ERROR: `/home/sybase/Install_items/pecl_pdo_dblib/PDO_DBLIB-1.0/configure' failed

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  • Make vhdresizer work on XP Mode VHD files

    - by A_M
    I'm trying to shrink a Windows 7 XP Mode VHD file with VhdResizer with little success. When I select my VHD file, it says "VhdExpand only supports fixed and dynamic VHD files". My XP Mode VHDs are dynamic files. Does anyone have any idea why it is failing? Failing that, does anyone have a process that I can use to shrink my XP mode VHD files? Thanks.

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  • IKE Phase 1 Aggressive Mode exchange does not complete

    - by Isaac Sutherland
    I've configured a 3G IP Gateway of mine to connect using IKE Phase 1 Aggressive Mode with PSK to my openswan installation running on Ubuntu server 12.04. I've configured openswan as follows: /etc/ipsec.conf: version 2.0 config setup nat_traversal=yes virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12 oe=off protostack=netkey conn net-to-net authby=secret left=192.168.0.11 [email protected] leftsubnet=10.1.0.0/16 leftsourceip=10.1.0.1 right=%any [email protected] rightsubnet=192.168.127.0/24 rightsourceip=192.168.127.254 aggrmode=yes ike=aes128-md5;modp1536 auto=add /etc/ipsec.secrets: @left.paxcoda.com @right.paxcoda.com: PSK "testpassword" Note that both left and right are NAT'd, with dynamic public IP's. My left ISP gives my router a public IP, but my right ISP gives me a shared dynamic public IP and dynamic private IP. I have dynamic dns for the public ip on the left side. Here is what I see when I sniff the ISAKMP protocol: 21:17:31.228715 IP (tos 0x0, ttl 235, id 43639, offset 0, flags [none], proto UDP (17), length 437) 74.198.87.93.49604 > 192.168.0.11.isakmp: [udp sum ok] isakmp 1.0 msgid 00000000 cookie da31a7896e2a1958->0000000000000000: phase 1 I agg: (sa: doi=ipsec situation=identity (p: #1 protoid=isakmp transform=1 (t: #1 id=ike (type=enc value=aes)(type=keylen value=0080)(type=hash value=md5)(type=auth value=preshared)(type=group desc value=modp1536)(type=lifetype value=sec)(type=lifeduration len=4 value=00015180)))) (ke: key len=192) (nonce: n len=16 data=(da31a7896e2a19582b33...0000001462b01880674b3739630ca7558cec8a89)) (id: idtype=FQDN protoid=0 port=0 len=17 right.paxcoda.com) (vid: len=16) (vid: len=16) (vid: len=16) (vid: len=16) 21:17:31.236720 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 456) 192.168.0.11.isakmp > 74.198.87.93.49604: [bad udp cksum 0x649c -> 0xcd2f!] isakmp 1.0 msgid 00000000 cookie da31a7896e2a1958->5b9776d4ea8b61b7: phase 1 R agg: (sa: doi=ipsec situation=identity (p: #1 protoid=isakmp transform=1 (t: #1 id=ike (type=enc value=aes)(type=keylen value=0080)(type=hash value=md5)(type=auth value=preshared)(type=group desc value=modp1536)(type=lifetype value=sec)(type=lifeduration len=4 value=00015180)))) (ke: key len=192) (nonce: n len=16 data=(32ccefcb793afb368975...000000144a131c81070358455c5728f20e95452f)) (id: idtype=FQDN protoid=0 port=0 len=16 left.paxcoda.com) (hash: len=16) (vid: len=16) (pay20) (pay20) (vid: len=16) However, my 3G Gateway (on the right) doesn't respond, and I don't know why. I think left's response is indeed getting through to my gateway, because in another question, I was trying to set up a similar scenario with Main Mode IKE, and in that case it looks as though at least one of the three 2-way main mode exchanges succeeded. What other explanation for the failure is there? (The 3G Gateway I'm using on the right is a Moxa G3150, by the way.)

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  • Netstat flags on OS/2

    - by Cian
    On an OS/2 box, what do the flags UGDP mean in the output of netstat -r. Google seems to point to them meaning Up, Gateway (i.e. an indirect root), and Dynamic (learned from a redirect), but that leaves me mystified as to the meaning of P. The only suggestion I've had is permanent but that doesn't make any sense with dynamic. Any ideas?

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  • How to shrink Windows 7 XP Mode VHD files?

    - by A_M
    I'm trying to shrink a Windows 7 XP Mode VHD file with VhdResizer with little success. When I select my VHD file, it says "VhdExpand only supports fixed and dynamic VHD files". My XP Mode VHDs are dynamic files. Does anyone have any idea why it is failing? Failing that, does anyone have a process that I can use to shrink my XP mode VHD files on Windows 7 (64 bit)?

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  • Do I dare clicking Delete Volume instead of Delete Partition?

    - by Olle
    I have a VMWare machine with one VM. That VM has a virtual disk which in windows is configured with two partitions and then a lot of slack space, as illustrated here: http://piclair.com/q8g5s What I want to do is delete the partition of 639 GB. However, since it's a dynamic disk, the right menu item says "Delete Volume" instead of "Delete Partition" (when I right click the 639GB space). My question is weather I dare to use "Delete Volume". I have read doing stuff like this on a dynamic volume can cause other partitions/volumes to go corrupt.

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  • Which web server architecture do you think is better?

    - by ngache
    use apache to server dynamic requests that need to be processed by php,and use nginx to serve static files use nginx to serve all requests So the key point is: which of them is more efficient in serving dynamic requests(we have no doubt that nginx is much better than apache in serving static files)?

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  • power equation for RAM

    - by kashyapa
    How is the dynamic power consumption of memory determined . Can anybody give a canonical equation for power consumption of the RAM. What are the parameters involved in determing the dynamic power consumption of RAM ? Thanks in advance

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  • how to make vhdresizer work on XP Mode VHD files

    - by A_M
    Hi, I'm trying to shrink an Windows 7 XP Mode VHD file with little success. I've been trying to use VhdResizer. When I select my VHD file, it says "VhdExpand only supports fixed and dynamic VHD files". My XP Mode VHDs are dynamic files. Does anyone have any idea why it is failing? Failing that, does anyone have a process which I can use to shrink my XP mode VHD files? Thanks.

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  • IP assignment in small network

    - by nooneon
    What is the best way to assign IPs in your opinion? I've got ~100 PCs, some servers and see three ways to assign IPs: Static IPs for every PC/server Static IP reservation by MAC-address in DHCP Dynamic IPs via DHCP. Of course, you can combine them, i.e. dynamic for PCs, static for servers. But, again, what is the best way? How do you do that?

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  • value types in the vm

    - by john.rose
    value types in the vm p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} p.p2 {margin: 0.0px 0.0px 14.0px 0.0px; font: 14.0px Times} p.p3 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times} p.p4 {margin: 0.0px 0.0px 15.0px 0.0px; font: 14.0px Times} p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier} p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier; min-height: 17.0px} p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p8 {margin: 0.0px 0.0px 0.0px 36.0px; text-indent: -36.0px; font: 14.0px Times; min-height: 18.0px} p.p9 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p10 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; color: #000000} li.li1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} li.li7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} span.s1 {font: 14.0px Courier} span.s2 {color: #000000} span.s3 {font: 14.0px Courier; color: #000000} ol.ol1 {list-style-type: decimal} Or, enduring values for a changing world. Introduction A value type is a data type which, generally speaking, is designed for being passed by value in and out of methods, and stored by value in data structures. The only value types which the Java language directly supports are the eight primitive types. Java indirectly and approximately supports value types, if they are implemented in terms of classes. For example, both Integer and String may be viewed as value types, especially if their usage is restricted to avoid operations appropriate to Object. In this note, we propose a definition of value types in terms of a design pattern for Java classes, accompanied by a set of usage restrictions. We also sketch the relation of such value types to tuple types (which are a JVM-level notion), and point out JVM optimizations that can apply to value types. This note is a thought experiment to extend the JVM’s performance model in support of value types. The demonstration has two phases.  Initially the extension can simply use design patterns, within the current bytecode architecture, and in today’s Java language. But if the performance model is to be realized in practice, it will probably require new JVM bytecode features, changes to the Java language, or both.  We will look at a few possibilities for these new features. An Axiom of Value In the context of the JVM, a value type is a data type equipped with construction, assignment, and equality operations, and a set of typed components, such that, whenever two variables of the value type produce equal corresponding values for their components, the values of the two variables cannot be distinguished by any JVM operation. Here are some corollaries: A value type is immutable, since otherwise a copy could be constructed and the original could be modified in one of its components, allowing the copies to be distinguished. Changing the component of a value type requires construction of a new value. The equals and hashCode operations are strictly component-wise. If a value type is represented by a JVM reference, that reference cannot be successfully synchronized on, and cannot be usefully compared for reference equality. A value type can be viewed in terms of what it doesn’t do. We can say that a value type omits all value-unsafe operations, which could violate the constraints on value types.  These operations, which are ordinarily allowed for Java object types, are pointer equality comparison (the acmp instruction), synchronization (the monitor instructions), all the wait and notify methods of class Object, and non-trivial finalize methods. The clone method is also value-unsafe, although for value types it could be treated as the identity function. Finally, and most importantly, any side effect on an object (however visible) also counts as an value-unsafe operation. A value type may have methods, but such methods must not change the components of the value. It is reasonable and useful to define methods like toString, equals, and hashCode on value types, and also methods which are specifically valuable to users of the value type. Representations of Value Value types have two natural representations in the JVM, unboxed and boxed. An unboxed value consists of the components, as simple variables. For example, the complex number x=(1+2i), in rectangular coordinate form, may be represented in unboxed form by the following pair of variables: /*Complex x = Complex.valueOf(1.0, 2.0):*/ double x_re = 1.0, x_im = 2.0; These variables might be locals, parameters, or fields. Their association as components of a single value is not defined to the JVM. Here is a sample computation which computes the norm of the difference between two complex numbers: double distance(/*Complex x:*/ double x_re, double x_im,         /*Complex y:*/ double y_re, double y_im) {     /*Complex z = x.minus(y):*/     double z_re = x_re - y_re, z_im = x_im - y_im;     /*return z.abs():*/     return Math.sqrt(z_re*z_re + z_im*z_im); } A boxed representation groups component values under a single object reference. The reference is to a ‘wrapper class’ that carries the component values in its fields. (A primitive type can naturally be equated with a trivial value type with just one component of that type. In that view, the wrapper class Integer can serve as a boxed representation of value type int.) The unboxed representation of complex numbers is practical for many uses, but it fails to cover several major use cases: return values, array elements, and generic APIs. The two components of a complex number cannot be directly returned from a Java function, since Java does not support multiple return values. The same story applies to array elements: Java has no ’array of structs’ feature. (Double-length arrays are a possible workaround for complex numbers, but not for value types with heterogeneous components.) By generic APIs I mean both those which use generic types, like Arrays.asList and those which have special case support for primitive types, like String.valueOf and PrintStream.println. Those APIs do not support unboxed values, and offer some problems to boxed values. Any ’real’ JVM type should have a story for returns, arrays, and API interoperability. The basic problem here is that value types fall between primitive types and object types. Value types are clearly more complex than primitive types, and object types are slightly too complicated. Objects are a little bit dangerous to use as value carriers, since object references can be compared for pointer equality, and can be synchronized on. Also, as many Java programmers have observed, there is often a performance cost to using wrapper objects, even on modern JVMs. Even so, wrapper classes are a good starting point for talking about value types. If there were a set of structural rules and restrictions which would prevent value-unsafe operations on value types, wrapper classes would provide a good notation for defining value types. This note attempts to define such rules and restrictions. Let’s Start Coding Now it is time to look at some real code. Here is a definition, written in Java, of a complex number value type. @ValueSafe public final class Complex implements java.io.Serializable {     // immutable component structure:     public final double re, im;     private Complex(double re, double im) {         this.re = re; this.im = im;     }     // interoperability methods:     public String toString() { return "Complex("+re+","+im+")"; }     public List<Double> asList() { return Arrays.asList(re, im); }     public boolean equals(Complex c) {         return re == c.re && im == c.im;     }     public boolean equals(@ValueSafe Object x) {         return x instanceof Complex && equals((Complex) x);     }     public int hashCode() {         return 31*Double.valueOf(re).hashCode()                 + Double.valueOf(im).hashCode();     }     // factory methods:     public static Complex valueOf(double re, double im) {         return new Complex(re, im);     }     public Complex changeRe(double re2) { return valueOf(re2, im); }     public Complex changeIm(double im2) { return valueOf(re, im2); }     public static Complex cast(@ValueSafe Object x) {         return x == null ? ZERO : (Complex) x;     }     // utility methods and constants:     public Complex plus(Complex c)  { return new Complex(re+c.re, im+c.im); }     public Complex minus(Complex c) { return new Complex(re-c.re, im-c.im); }     public double abs() { return Math.sqrt(re*re + im*im); }     public static final Complex PI = valueOf(Math.PI, 0.0);     public static final Complex ZERO = valueOf(0.0, 0.0); } This is not a minimal definition, because it includes some utility methods and other optional parts.  The essential elements are as follows: The class is marked as a value type with an annotation. The class is final, because it does not make sense to create subclasses of value types. The fields of the class are all non-private and final.  (I.e., the type is immutable and structurally transparent.) From the supertype Object, all public non-final methods are overridden. The constructor is private. Beyond these bare essentials, we can observe the following features in this example, which are likely to be typical of all value types: One or more factory methods are responsible for value creation, including a component-wise valueOf method. There are utility methods for complex arithmetic and instance creation, such as plus and changeIm. There are static utility constants, such as PI. The type is serializable, using the default mechanisms. There are methods for converting to and from dynamically typed references, such as asList and cast. The Rules In order to use value types properly, the programmer must avoid value-unsafe operations.  A helpful Java compiler should issue errors (or at least warnings) for code which provably applies value-unsafe operations, and should issue warnings for code which might be correct but does not provably avoid value-unsafe operations.  No such compilers exist today, but to simplify our account here, we will pretend that they do exist. A value-safe type is any class, interface, or type parameter marked with the @ValueSafe annotation, or any subtype of a value-safe type.  If a value-safe class is marked final, it is in fact a value type.  All other value-safe classes must be abstract.  The non-static fields of a value class must be non-public and final, and all its constructors must be private. Under the above rules, a standard interface could be helpful to define value types like Complex.  Here is an example: @ValueSafe public interface ValueType extends java.io.Serializable {     // All methods listed here must get redefined.     // Definitions must be value-safe, which means     // they may depend on component values only.     List<? extends Object> asList();     int hashCode();     boolean equals(@ValueSafe Object c);     String toString(); } //@ValueSafe inherited from supertype: public final class Complex implements ValueType { … The main advantage of such a conventional interface is that (unlike an annotation) it is reified in the runtime type system.  It could appear as an element type or parameter bound, for facilities which are designed to work on value types only.  More broadly, it might assist the JVM to perform dynamic enforcement of the rules for value types. Besides types, the annotation @ValueSafe can mark fields, parameters, local variables, and methods.  (This is redundant when the type is also value-safe, but may be useful when the type is Object or another supertype of a value type.)  Working forward from these annotations, an expression E is defined as value-safe if it satisfies one or more of the following: The type of E is a value-safe type. E names a field, parameter, or local variable whose declaration is marked @ValueSafe. E is a call to a method whose declaration is marked @ValueSafe. E is an assignment to a value-safe variable, field reference, or array reference. E is a cast to a value-safe type from a value-safe expression. E is a conditional expression E0 ? E1 : E2, and both E1 and E2 are value-safe. Assignments to value-safe expressions and initializations of value-safe names must take their values from value-safe expressions. A value-safe expression may not be the subject of a value-unsafe operation.  In particular, it cannot be synchronized on, nor can it be compared with the “==” operator, not even with a null or with another value-safe type. In a program where all of these rules are followed, no value-type value will be subject to a value-unsafe operation.  Thus, the prime axiom of value types will be satisfied, that no two value type will be distinguishable as long as their component values are equal. More Code To illustrate these rules, here are some usage examples for Complex: Complex pi = Complex.valueOf(Math.PI, 0); Complex zero = pi.changeRe(0);  //zero = pi; zero.re = 0; ValueType vtype = pi; @SuppressWarnings("value-unsafe")   Object obj = pi; @ValueSafe Object obj2 = pi; obj2 = new Object();  // ok List<Complex> clist = new ArrayList<Complex>(); clist.add(pi);  // (ok assuming List.add param is @ValueSafe) List<ValueType> vlist = new ArrayList<ValueType>(); vlist.add(pi);  // (ok) List<Object> olist = new ArrayList<Object>(); olist.add(pi);  // warning: "value-unsafe" boolean z = pi.equals(zero); boolean z1 = (pi == zero);  // error: reference comparison on value type boolean z2 = (pi == null);  // error: reference comparison on value type boolean z3 = (pi == obj2);  // error: reference comparison on value type synchronized (pi) { }  // error: synch of value, unpredictable result synchronized (obj2) { }  // unpredictable result Complex qq = pi; qq = null;  // possible NPE; warning: “null-unsafe" qq = (Complex) obj;  // warning: “null-unsafe" qq = Complex.cast(obj);  // OK @SuppressWarnings("null-unsafe")   Complex empty = null;  // possible NPE qq = empty;  // possible NPE (null pollution) The Payoffs It follows from this that either the JVM or the java compiler can replace boxed value-type values with unboxed ones, without affecting normal computations.  Fields and variables of value types can be split into their unboxed components.  Non-static methods on value types can be transformed into static methods which take the components as value parameters. Some common questions arise around this point in any discussion of value types. Why burden the programmer with all these extra rules?  Why not detect programs automagically and perform unboxing transparently?  The answer is that it is easy to break the rules accidently unless they are agreed to by the programmer and enforced.  Automatic unboxing optimizations are tantalizing but (so far) unreachable ideal.  In the current state of the art, it is possible exhibit benchmarks in which automatic unboxing provides the desired effects, but it is not possible to provide a JVM with a performance model that assures the programmer when unboxing will occur.  This is why I’m writing this note, to enlist help from, and provide assurances to, the programmer.  Basically, I’m shooting for a good set of user-supplied “pragmas” to frame the desired optimization. Again, the important thing is that the unboxing must be done reliably, or else programmers will have no reason to work with the extra complexity of the value-safety rules.  There must be a reasonably stable performance model, wherein using a value type has approximately the same performance characteristics as writing the unboxed components as separate Java variables. There are some rough corners to the present scheme.  Since Java fields and array elements are initialized to null, value-type computations which incorporate uninitialized variables can produce null pointer exceptions.  One workaround for this is to require such variables to be null-tested, and the result replaced with a suitable all-zero value of the value type.  That is what the “cast” method does above. Generically typed APIs like List<T> will continue to manipulate boxed values always, at least until we figure out how to do reification of generic type instances.  Use of such APIs will elicit warnings until their type parameters (and/or relevant members) are annotated or typed as value-safe.  Retrofitting List<T> is likely to expose flaws in the present scheme, which we will need to engineer around.  Here are a couple of first approaches: public interface java.util.List<@ValueSafe T> extends Collection<T> { … public interface java.util.List<T extends Object|ValueType> extends Collection<T> { … (The second approach would require disjunctive types, in which value-safety is “contagious” from the constituent types.) With more transformations, the return value types of methods can also be unboxed.  This may require significant bytecode-level transformations, and would work best in the presence of a bytecode representation for multiple value groups, which I have proposed elsewhere under the title “Tuples in the VM”. But for starters, the JVM can apply this transformation under the covers, to internally compiled methods.  This would give a way to express multiple return values and structured return values, which is a significant pain-point for Java programmers, especially those who work with low-level structure types favored by modern vector and graphics processors.  The lack of multiple return values has a strong distorting effect on many Java APIs. Even if the JVM fails to unbox a value, there is still potential benefit to the value type.  Clustered computing systems something have copy operations (serialization or something similar) which apply implicitly to command operands.  When copying JVM objects, it is extremely helpful to know when an object’s identity is important or not.  If an object reference is a copied operand, the system may have to create a proxy handle which points back to the original object, so that side effects are visible.  Proxies must be managed carefully, and this can be expensive.  On the other hand, value types are exactly those types which a JVM can “copy and forget” with no downside. Array types are crucial to bulk data interfaces.  (As data sizes and rates increase, bulk data becomes more important than scalar data, so arrays are definitely accompanying us into the future of computing.)  Value types are very helpful for adding structure to bulk data, so a successful value type mechanism will make it easier for us to express richer forms of bulk data. Unboxing arrays (i.e., arrays containing unboxed values) will provide better cache and memory density, and more direct data movement within clustered or heterogeneous computing systems.  They require the deepest transformations, relative to today’s JVM.  There is an impedance mismatch between value-type arrays and Java’s covariant array typing, so compromises will need to be struck with existing Java semantics.  It is probably worth the effort, since arrays of unboxed value types are inherently more memory-efficient than standard Java arrays, which rely on dependent pointer chains. It may be sufficient to extend the “value-safe” concept to array declarations, and allow low-level transformations to change value-safe array declarations from the standard boxed form into an unboxed tuple-based form.  Such value-safe arrays would not be convertible to Object[] arrays.  Certain connection points, such as Arrays.copyOf and System.arraycopy might need additional input/output combinations, to allow smooth conversion between arrays with boxed and unboxed elements. Alternatively, the correct solution may have to wait until we have enough reification of generic types, and enough operator overloading, to enable an overhaul of Java arrays. Implicit Method Definitions The example of class Complex above may be unattractively complex.  I believe most or all of the elements of the example class are required by the logic of value types. If this is true, a programmer who writes a value type will have to write lots of error-prone boilerplate code.  On the other hand, I think nearly all of the code (except for the domain-specific parts like plus and minus) can be implicitly generated. Java has a rule for implicitly defining a class’s constructor, if no it defines no constructors explicitly.  Likewise, there are rules for providing default access modifiers for interface members.  Because of the highly regular structure of value types, it might be reasonable to perform similar implicit transformations on value types.  Here’s an example of a “highly implicit” definition of a complex number type: public class Complex implements ValueType {  // implicitly final     public double re, im;  // implicitly public final     //implicit methods are defined elementwise from te fields:     //  toString, asList, equals(2), hashCode, valueOf, cast     //optionally, explicit methods (plus, abs, etc.) would go here } In other words, with the right defaults, a simple value type definition can be a one-liner.  The observant reader will have noticed the similarities (and suitable differences) between the explicit methods above and the corresponding methods for List<T>. Another way to abbreviate such a class would be to make an annotation the primary trigger of the functionality, and to add the interface(s) implicitly: public @ValueType class Complex { … // implicitly final, implements ValueType (But to me it seems better to communicate the “magic” via an interface, even if it is rooted in an annotation.) Implicitly Defined Value Types So far we have been working with nominal value types, which is to say that the sequence of typed components is associated with a name and additional methods that convey the intention of the programmer.  A simple ordered pair of floating point numbers can be variously interpreted as (to name a few possibilities) a rectangular or polar complex number or Cartesian point.  The name and the methods convey the intended meaning. But what if we need a truly simple ordered pair of floating point numbers, without any further conceptual baggage?  Perhaps we are writing a method (like “divideAndRemainder”) which naturally returns a pair of numbers instead of a single number.  Wrapping the pair of numbers in a nominal type (like “QuotientAndRemainder”) makes as little sense as wrapping a single return value in a nominal type (like “Quotient”).  What we need here are structural value types commonly known as tuples. For the present discussion, let us assign a conventional, JVM-friendly name to tuples, roughly as follows: public class java.lang.tuple.$DD extends java.lang.tuple.Tuple {      double $1, $2; } Here the component names are fixed and all the required methods are defined implicitly.  The supertype is an abstract class which has suitable shared declarations.  The name itself mentions a JVM-style method parameter descriptor, which may be “cracked” to determine the number and types of the component fields. The odd thing about such a tuple type (and structural types in general) is it must be instantiated lazily, in response to linkage requests from one or more classes that need it.  The JVM and/or its class loaders must be prepared to spin a tuple type on demand, given a simple name reference, $xyz, where the xyz is cracked into a series of component types.  (Specifics of naming and name mangling need some tasteful engineering.) Tuples also seem to demand, even more than nominal types, some support from the language.  (This is probably because notations for non-nominal types work best as combinations of punctuation and type names, rather than named constructors like Function3 or Tuple2.)  At a minimum, languages with tuples usually (I think) have some sort of simple bracket notation for creating tuples, and a corresponding pattern-matching syntax (or “destructuring bind”) for taking tuples apart, at least when they are parameter lists.  Designing such a syntax is no simple thing, because it ought to play well with nominal value types, and also with pre-existing Java features, such as method parameter lists, implicit conversions, generic types, and reflection.  That is a task for another day. Other Use Cases Besides complex numbers and simple tuples there are many use cases for value types.  Many tuple-like types have natural value-type representations. These include rational numbers, point locations and pixel colors, and various kinds of dates and addresses. Other types have a variable-length ‘tail’ of internal values. The most common example of this is String, which is (mathematically) a sequence of UTF-16 character values. Similarly, bit vectors, multiple-precision numbers, and polynomials are composed of sequences of values. Such types include, in their representation, a reference to a variable-sized data structure (often an array) which (somehow) represents the sequence of values. The value type may also include ’header’ information. Variable-sized values often have a length distribution which favors short lengths. In that case, the design of the value type can make the first few values in the sequence be direct ’header’ fields of the value type. In the common case where the header is enough to represent the whole value, the tail can be a shared null value, or even just a null reference. Note that the tail need not be an immutable object, as long as the header type encapsulates it well enough. This is the case with String, where the tail is a mutable (but never mutated) character array. Field types and their order must be a globally visible part of the API.  The structure of the value type must be transparent enough to have a globally consistent unboxed representation, so that all callers and callees agree about the type and order of components  that appear as parameters, return types, and array elements.  This is a trade-off between efficiency and encapsulation, which is forced on us when we remove an indirection enjoyed by boxed representations.  A JVM-only transformation would not care about such visibility, but a bytecode transformation would need to take care that (say) the components of complex numbers would not get swapped after a redefinition of Complex and a partial recompile.  Perhaps constant pool references to value types need to declare the field order as assumed by each API user. This brings up the delicate status of private fields in a value type.  It must always be possible to load, store, and copy value types as coordinated groups, and the JVM performs those movements by moving individual scalar values between locals and stack.  If a component field is not public, what is to prevent hostile code from plucking it out of the tuple using a rogue aload or astore instruction?  Nothing but the verifier, so we may need to give it more smarts, so that it treats value types as inseparable groups of stack slots or locals (something like long or double). My initial thought was to make the fields always public, which would make the security problem moot.  But public is not always the right answer; consider the case of String, where the underlying mutable character array must be encapsulated to prevent security holes.  I believe we can win back both sides of the tradeoff, by training the verifier never to split up the components in an unboxed value.  Just as the verifier encapsulates the two halves of a 64-bit primitive, it can encapsulate the the header and body of an unboxed String, so that no code other than that of class String itself can take apart the values. Similar to String, we could build an efficient multi-precision decimal type along these lines: public final class DecimalValue extends ValueType {     protected final long header;     protected private final BigInteger digits;     public DecimalValue valueOf(int value, int scale) {         assert(scale >= 0);         return new DecimalValue(((long)value << 32) + scale, null);     }     public DecimalValue valueOf(long value, int scale) {         if (value == (int) value)             return valueOf((int)value, scale);         return new DecimalValue(-scale, new BigInteger(value));     } } Values of this type would be passed between methods as two machine words. Small values (those with a significand which fits into 32 bits) would be represented without any heap data at all, unless the DecimalValue itself were boxed. (Note the tension between encapsulation and unboxing in this case.  It would be better if the header and digits fields were private, but depending on where the unboxing information must “leak”, it is probably safer to make a public revelation of the internal structure.) Note that, although an array of Complex can be faked with a double-length array of double, there is no easy way to fake an array of unboxed DecimalValues.  (Either an array of boxed values or a transposed pair of homogeneous arrays would be reasonable fallbacks, in a current JVM.)  Getting the full benefit of unboxing and arrays will require some new JVM magic. Although the JVM emphasizes portability, system dependent code will benefit from using machine-level types larger than 64 bits.  For example, the back end of a linear algebra package might benefit from value types like Float4 which map to stock vector types.  This is probably only worthwhile if the unboxing arrays can be packed with such values. More Daydreams A more finely-divided design for dynamic enforcement of value safety could feature separate marker interfaces for each invariant.  An empty marker interface Unsynchronizable could cause suitable exceptions for monitor instructions on objects in marked classes.  More radically, a Interchangeable marker interface could cause JVM primitives that are sensitive to object identity to raise exceptions; the strangest result would be that the acmp instruction would have to be specified as raising an exception. @ValueSafe public interface ValueType extends java.io.Serializable,         Unsynchronizable, Interchangeable { … public class Complex implements ValueType {     // inherits Serializable, Unsynchronizable, Interchangeable, @ValueSafe     … It seems possible that Integer and the other wrapper types could be retro-fitted as value-safe types.  This is a major change, since wrapper objects would be unsynchronizable and their references interchangeable.  It is likely that code which violates value-safety for wrapper types exists but is uncommon.  It is less plausible to retro-fit String, since the prominent operation String.intern is often used with value-unsafe code. We should also reconsider the distinction between boxed and unboxed values in code.  The design presented above obscures that distinction.  As another thought experiment, we could imagine making a first class distinction in the type system between boxed and unboxed representations.  Since only primitive types are named with a lower-case initial letter, we could define that the capitalized version of a value type name always refers to the boxed representation, while the initial lower-case variant always refers to boxed.  For example: complex pi = complex.valueOf(Math.PI, 0); Complex boxPi = pi;  // convert to boxed myList.add(boxPi); complex z = myList.get(0);  // unbox Such a convention could perhaps absorb the current difference between int and Integer, double and Double. It might also allow the programmer to express a helpful distinction among array types. As said above, array types are crucial to bulk data interfaces, but are limited in the JVM.  Extending arrays beyond the present limitations is worth thinking about; for example, the Maxine JVM implementation has a hybrid object/array type.  Something like this which can also accommodate value type components seems worthwhile.  On the other hand, does it make sense for value types to contain short arrays?  And why should random-access arrays be the end of our design process, when bulk data is often sequentially accessed, and it might make sense to have heterogeneous streams of data as the natural “jumbo” data structure.  These considerations must wait for another day and another note. More Work It seems to me that a good sequence for introducing such value types would be as follows: Add the value-safety restrictions to an experimental version of javac. Code some sample applications with value types, including Complex and DecimalValue. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. A staggered roll-out like this would decouple language changes from bytecode changes, which is always a convenient thing. A similar investigation should be applied (concurrently) to array types.  In this case, it seems to me that the starting point is in the JVM: Add an experimental unboxing array data structure to a production JVM, perhaps along the lines of Maxine hybrids.  No bytecode or language support is required at first; everything can be done with encapsulated unsafe operations and/or method handles. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. That’s enough musing me for now.  Back to work!

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  • How can I turn on DynamicCompression feature of IIS programmatically?

    - by LockeVN
    I'm making an installer program for my web application. My web application uses CSS and JS heavily, so I want to enable both Static and Dynamic HttpCompression for IIS7/7.5. It needs 2 steps: I can modified the web.config, put <httpcompression> tag, it's ok. DynamicContentCompression must be turned on in Windows Feature to make httpCompression work. Static HttpCompression is enable by default in IIS7 and IIS7.5, but Dynamic HttpCompression is not enable by default (although it's available). I can do manually by turn on: Start/ControlPanel/ProgramsAndFeatures/TurnWindowsFeatures on or Off/IIS/WWW Service/Performance features/Dynamic Content Compression, but How can I programmatically turn it on that Windows Feature? I can use PowerShell, C# in my installer. Any idea how I might be able to do this? Thanks.

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  • GCC / C++ Static linking for headers in a shared object

    - by Swaroop S
    -I am trying to create a shared object libfoo.so. libfoo.so is created from "foo.c" - Assume that I include headers "static.h" and "Dynamic.h" where in I want the compiler to resolve the symbols for Static.h and leave the rest ie from Dynamic.h for runtime. - How do i do this ? What are the CFLAG and LDFLAG options that I need to pass. - My makefile is setup to create a shared object using the CFLAGS=fPIC , shared , W1,export-dynamic. - In the include paths i Specify the correct location for "Static.h" Can someone help me ?

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  • Edit first column of GridView

    - by nCdy
    I've got very dynamic GridView and I need to allow to user to edit first column of it. After he edit first column of grid it must be updated on DataBase. Is there any ways to handle it ? My only idea is to put some changeable element to first cell of each Row so it must be able to set / get my values for each row but can't find yet any examples of it ... Additional info : GridView takes data from Object data source and all columns are dynamic (yes, maybe except first, but I add it in dynamic way) and load complete DataTable...

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  • when text changed inputbox automatically updates next 6 text boxes

    - by James123
    I have 7 textboxes. If Top 1 textbox(Volume All Years) text changed, text need to be updated in next 6 inputboxes(Latest 2009 Volume to Latest 2014 Volume). I need javascript or Jquery for this. I will write Js textchanged() or focuschange() for top 1 textbox. So what should I write in focuschage() or textchanged methods() <tr id="row12_136" class="RegText"> <td style="width:420px;Padding-right:20px;">Volume All Years</td> <td style="width:420px;Padding-left:0px;"> <input name="12_136" type="text" maxlength="255" id="12_136" tabindex="61" title="Volume All Years" class="textbox" OnKeyPress="javascript:FocusChange();" style="width:300px;" /> </td> </tr><tr id="row12_60" class="RegText"> <td style="width:420px;Padding-right:20px;">Latest 2009 Volume*</td> <td style="width:420px;Padding-left:0px;"> <input name="12_60" type="text" maxlength="255" id="12_60" tabindex="62" title="Latest 2009 Volume" class="textbox" OnKeyPress="javascript:FocusChange();" style="width:300px;" /> <span controltovalidate="12_60" errormessage="* Required!" display="Dynamic" validationGroup="ValidateInsert" id="_ctl47" evaluationfunction="RequiredFieldValidatorEvaluateIsValid" initialvalue="" style="color:Red;display:none;">* Required!</span> </td> </tr><tr id="row12_61" class="RegText"> <td style="width:420px;Padding-right:20px;">Latest 2010 Volume*</td> <td style="width:420px;Padding-left:0px;"> <input name="12_61" type="text" maxlength="255" id="12_61" tabindex="63" title="Latest 2010 Volume" class="textbox" OnKeyPress="javascript:FocusChange();" style="width:300px;" /> <span controltovalidate="12_61" errormessage="* Required!" display="Dynamic" validationGroup="ValidateInsert" id="_ctl48" evaluationfunction="RequiredFieldValidatorEvaluateIsValid" initialvalue="" style="color:Red;display:none;">* Required!</span> </td> </tr><tr id="row12_62" class="RegText"> <td style="width:420px;Padding-right:20px;">Latest 2011 Volume*</td> <td style="width:420px;Padding-left:0px;"> <input name="12_62" type="text" maxlength="255" id="12_62" tabindex="64" title="Latest 2011 Volume" class="textbox" OnKeyPress="javascript:FocusChange();" style="width:300px;" /> <span controltovalidate="12_62" errormessage="* Required!" display="Dynamic" validationGroup="ValidateInsert" id="_ctl49" evaluationfunction="RequiredFieldValidatorEvaluateIsValid" initialvalue="" style="color:Red;display:none;">* Required!</span> </td> </tr><tr id="row12_63" class="RegText"> <td style="width:420px;Padding-right:20px;">Latest 2012 Volume*</td> <td style="width:420px;Padding-left:0px;"> <input name="12_63" type="text" maxlength="255" id="12_63" tabindex="65" title="Latest 2012 Volume" class="textbox" OnKeyPress="javascript:FocusChange();" style="width:300px;" /> <span controltovalidate="12_63" errormessage="* Required!" display="Dynamic" validationGroup="ValidateInsert" id="_ctl50" evaluationfunction="RequiredFieldValidatorEvaluateIsValid" initialvalue="" style="color:Red;display:none;">* Required!</span> </td> </tr><tr id="row12_64" class="RegText"> <td style="width:420px;Padding-right:20px;">Latest 2013 Volume*</td> <td style="width:420px;Padding-left:0px;"> <input name="12_64" type="text" maxlength="255" id="12_64" tabindex="66" title="Latest 2013 Volume" class="textbox" OnKeyPress="javascript:FocusChange();" style="width:300px;" /> <span controltovalidate="12_64" errormessage="* Required!" display="Dynamic" validationGroup="ValidateInsert" id="_ctl51" evaluationfunction="RequiredFieldValidatorEvaluateIsValid" initialvalue="" style="color:Red;display:none;">* Required!</span> </td> </tr><tr id="row12_65" class="RegText"> <td style="width:420px;Padding-right:20px;">Latest 2014 Volume*</td> <td style="width:420px;Padding-left:0px;"> <input name="12_65" type="text" maxlength="255" id="12_65" tabindex="67" title="Latest 2014 Volume" class="textbox" OnKeyPress="javascript:FocusChange();" style="width:300px;" /> <span controltovalidate="12_65" errormessage="* Required!" display="Dynamic" validationGroup="ValidateInsert" id="_ctl52" evaluationfunction="RequiredFieldValidatorEvaluateIsValid" initialvalue="" style="color:Red;display:none;">* Required!</span> </td>

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  • Embedded Linux: Memory Fragmentation

    - by waffleman
    In many embedded systems, memory fragmentation is a concern. Particularly, for software that runs for long periods of time (months, years, etc...). For many projects, the solution is to simply not use dynamic memory allocation such as malloc/free and new/delete. Global memory is used whenever possible and memory pools for types that are frequently allocated and deallocated are good strategies to avoid dynamic memory management use. In Embedded Linux how is this addressed? I see many libraries use dynamic memory. Is there mechanism that the OS uses to prevent memory fragmentation? Does it clean up the heap periodically? Or should one avoid using these libraries in an embedded environment?

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