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• SQL Server Clustered Index: (Physical) Data Page Order

  - by scherand

  I am struggling understanding what a clustered index in SQL Server 2005 is. I read the MSDN article Clustered Index Structures (among other things) but I am still unsure if I understand it correctly. The (main) question is: what happens if I insert a row (with a "low" key) into a table with a clustered index? The above mentioned MSDN article states: The pages in the data chain and the rows in them are ordered on the value of the clustered index key. And Using Clustered Indexes for example states: For example, if a record is added to the table that is close to the beginning of the sequentially ordered list, any records in the table after that record will need to shift to allow the record to be inserted. Does this mean that if I insert a row with a very "low" key into a table that already contains a gazillion rows literally all rows are physically shifted on disk? I cannot believe that. This would take ages, no? Or is it rather (as I suspect) that there are two scenarios depending on how "full" the first data page is. A) If the page has enough free space to accommodate the record it is placed into the existing data page and data might be (physically) reordered within that page. B) If the page does not have enough free space for the record a new data page would be created (anywhere on the disk!) and "linked" to the front of the leaf level of the B-Tree? This would then mean the "physical order" of the data is restricted to the "page level" (i.e. within a data page) but not to the pages residing on consecutive blocks on the physical hard drive. The data pages are then just linked together in the correct order. Or formulated in an alternative way: if SQL Server needs to read the first N rows of a table that has a clustered index it can read data pages sequentially (following the links) but these pages are not (necessarily) block wise in sequence on disk (so the disk head has to move "randomly"). How close am I? :)

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• Documentation for java.util.concurrent.locks.ReentrantReadWriteLock

  - by Andrei Taptunov

  Disclaimer: I'm not very good at Java and just comparing read/writer locks between C# and Java to understand this topic better & decisions behind both implementations. There is JavaDoc about ReentrantReadWriteLock. It states the following about upgrade/downgrade for locks: Lock downgrading ... However, upgrading from a read lock to the write lock is not possible. It also has the following example that shows manual upgrade from read lock to write lock: // Here is a code sketch showing how to exploit reentrancy // to perform lock downgrading after updating a cache void processCachedData() { rwl.readLock().lock(); if (!cacheValid) { // upgrade lock manually #1: rwl.readLock().unlock(); // must unlock first to obtain writelock #2: rwl.writeLock().lock(); if (!cacheValid) { // recheck ... } ... } use(data); rwl.readLock().unlock(); Does it mean that actually the sample from above may not behave correctly in some cases - I mean there is no lock between lines #1 & #2 and underlying structure is exposed to changes from other threads. So it can not be considered as the correct way to upgrade the lock or do I miss something here?

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• Using .NET XmlSerializer with get properties and setter functions

  - by brone

  I'm trying to use XmlSerializer from C# to save out a class that has some values that are read by properties (the code being just a simple retrieval of field value) but set by setter functions (since there is a delegate called if the value changes). What I'm currently doing is this sort of thing. The intended use is to use the InT property to read the value, and use SetInT to set it. Setting it has side-effects, so a method is more appropriate than a property here. XmlSerializationOnly_InT exists solely for the benefit of the XmlSerializer (hence the name), and shouldn't be used by normal code. class X { public double InT { get { return _inT; } } public void SetInT(double newInT) { if (newInT != _inT) { _inT = newInT; Changed();//includes delegate call; potentially expensive } } private double _inT; // not called by normal code, as the property set is not just a simple // field set or two. [XmlElement(ElementName = "InT")] public double XmlSerializationOnly_InT { get { return InT; } set { SetInT(value); } } } This works, it's easy enough to do, and the XML file looks like you'd expect. It's manual labour though, and a bit ugly, so I'm only somewhat satisfied. What I'd really like is to be able to tell the XML serialization to read the value using the property, and set it using the setter function. Then I wouldn't need XmlSerializationOnly_InT at all. I seem to be following standard practise by distinguishing between property sets and setter functions in this way, so I'm sure I'm not the only person to have encountered this (though google suggests I might be). What have others done in this situation? Is there some easy way to persuade the XmlSerializer to handle this sort of thing better? If not, is there perhaps some other easy way to do it?

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• Need a design pattern for representing multiple information sources

  - by hsmit

  I'm building a Java application that retrieves information from differing information sources. I'm using a sensor, a set of RecordStores and a few online web services. In the basic application all these resources are loaded by default. Some of these sources are directly read in a separate thread (load database, read sensor etc.). From this basic application some functions are started that use these sources. The classes that contain these functions (usually combining multiple sources information) are currently paramterized with a set of resources like this: AppPart a1 = new AppPart(source1, source2, source3); I could also do it like this AppPart a1 = new AppPart(this); ..where I need to make my sources public in order to read them. I'm also thinking about a kind of stage/collection to publish all sources on, e.g: public SourceCollectionStage sStage = new SourceCollectionStage(); and later: sStage.getSensor(); .. for example. What do you guys think is the best or most often used way to do this? Btw: the user interface is often implemented by the specific funtion classes, not by the main class. Should I do this in another way?

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• Map element position in data file to class property

  - by Augusto

  I need to read/write files, following a format provided by a third party specification. The specification itself is pretty simple: it says the position and the size of the data that will be saved in the file. For example: Position Size Description -------------------------------------------------- 0001 10 Device serial number 0011 02 Hour 0013 02 Minute 0015 02 Second 0017 02 Day 0019 02 Month 0021 02 Year The list is very long, it has about 400 elements. But lots of them can be combined. For example, hour, minute, second, day, month and year can be combined in a single DateTime object. I've splitted the elements into about 4 categories, and created separeted classes for holding the data. So, instead of a big structure representing the data, I have some smaller classes. I've also created different classes for reading and writing the data. The problem is: how to map the positions in the file to the objects properties, so that I don't need to repeat the values in the reading/writing class? I could use some custom attributes and retrieve them via reflection. But since the code will be running on devices with small memory and processor, it would be nice to find another way. My current read code looks like this: public void Read() { DataFile dataFile = new DataFile(); // the arguments are: position, size dataFile.SerialNumber = ReadLong(1, 10); //... } Any ideas on this one? Thanks!

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• Subversion svn:externals - What's wrong here?

  - by Brandon Montgomery

  I first want to say I've read the Subversion manual. I've read this question. I've also read this question. Here's my dilemma. Let's say I have 3 repositories laid out like this: DataAccessObject/ branches/ tags/ trunk/ DataAccessObject/ DataAccessObjectTests/ PlanObject/ branches/ tags/ trunk/ PlanObject/ PlanObjectTests/ WinFormsPlanViewer/ branches/ tags/ trunk/ WinFormsPlanViewer/ The PlanObject and DataAccessObject repositories contain shared projects. They are used by the WinFormsPlanViewer, but also by several other projects in several other repositories. Bear with me here. I put an svn:externals definition on the WinFormsPlanViewer/trunk folder like this: https://server/svn/PlanObject/trunk Objects https://server/svn/DataAccessObject/trunk Objects And here's what I see after I do an svn update. WinFormsPlanViewer/ branches/ tags/ trunk/ WinFormsPlanViewer/ Objects/ DataAccessObject/ DataAccessObjectTests/ The PlanObject stuff doesn't even come down in the update! I don't know if this has anything to do with it, but there's an externals definition on the PlanObject/trunk folder also: https://server/svn/DataAccessObject/trunk Objects What's going on here? What am I doing wrong? Are there bad consequences of referencing the PlanObject and the DataAccessObject from the WinFormsPlanViewer using svn:externals when the PlanObject references the DataAccessObject using svn:externals also?

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• Why does output of fltk-config truncate arguments to gcc?

  - by James Morris

  I'm trying to build an application I've downloaded which uses the SCONS "make replacement" and the Fast Light Tool Kit Gui. The SConstruct code to detect the presence of fltk is: guienv = Environment(CPPFLAGS = '') guiconf = Configure(guienv) if not guiconf.CheckLibWithHeader('lo', 'lo/lo.h','c'): print 'Did not find liblo for OSC, exiting!' Exit(1) if not guiconf.CheckLibWithHeader('fltk', 'FL/Fl.H','c++'): print 'Did not find FLTK for the gui, exiting!' Exit(1) Unfortunately, on my (Gentoo Linux) system, and many others (Linux distributions) this can be quite troublesome if the package manager allows the simultaneous install of FLTK-1 and FLTK-2. I have attempted to modify the SConstruct file to use fltk-config --cflags and fltk-config --ldflags (or fltk-config --libs might be better than ldflags) by adding them like so: guienv.Append(CPPPATH = os.popen('fltk-config --cflags').read()) guienv.Append(LIBPATH = os.popen('fltk-config --ldflags').read()) But this causes the test for liblo to fail! Looking in config.log shows how it failed: scons: Configure: Checking for C library lo... gcc -o .sconf_temp/conftest_4.o -c "-I/usr/include/fltk-1.1 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_THREAD_SAFE -D_REENTRANT" gcc: no input files scons: Configure: no How should this really be done? And to complete my answer, how do I remove the quotes from the result of os.popen( 'command').read()? EDIT The real question here is why does appending the output of fltk-config cause gcc to not receive the filename argument it is supposed to compile?

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• DataTable vs. Collection in .Net

  - by B Pete

  I am writing a program that needs to read a set of records that describe the register map of a device I need to communicate with. Each record will have a handfull of fields that describe the properties of each register. I don't really need to edit or modify the data in my VB or C# program, though I would like to be able to display the data on a grid. I would like to store the data in a CSV file, or perhaps an XML file. I need to enable users to edit the data off-line, preferably in excel. I am considering using a DataTable or a Collection of "Register" objects (which I would define). I prototyped a DataTable, and found I can read/write XML easily using the built in methods and I can easily bind to a DataGridView. I was not able to find a way to retreive info on a single register without using a query that returns a collection of rows, even though I defined a unique primaty key column. The syntax to get a value from a column is also complex, though I could be missing something on both counts. I'm tempted to use a collection of "Register" objects that I can access via a unique key. It would be a little more coding up front, but seems like a cleaner solution overall. I should still be able to use LINQ to dataset to query subsets of registers when I need them, but would also be able to grab a single field using a the key value, something like this: Registers(keyValue).fieldName). Which would be a cleaner approach to the problem? Is there a way to read/write XML into a Collection without needing custom code? Could this be accomplished using String for a key?

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• Using perl to split a line that may contain whitespace

  - by Tommy Fisk

  Okay, so I'm using perl to read in a file that contains some general configuration data. This data is organized into headers based on what they mean. An example follows: [vars] # This is how we define a variable! $var = 10; $str = "Hello thar!"; # This section contains flags which can be used to modify module behavior # All modules read this file and if they understand any of the flags, use them [flags] Verbose = true; # Notice the errant whitespace! [path] WinPath = default; # Keyword which loads the standard PATH as defined by the operating system. Append with additonal values. LinuxPath = default; Goal: Using the first line as an example "$var = 10;", I'd like to use the split function in perl to create an array that contains the characters "$var" and "10" as elements. Using another line as an example: Verbose = true; # Should become [Verbose, true] aka no whitespace is present This is needed because I will be outputting these values to a new file (which a different piece of C++ code will read) to instantiate dictionary objects. Just to give you a little taste of what it might look like (just making it up as I go along): define new dictionary name: [flags] # Start defining keys => values new key name: Verbose new value val: 10 # End dictionary Oh, and here is the code I currently have along with what it is doing (incorrectly): sub makeref($) { my @line = (split (/=/)); # Produces ["Verbose", " true"]; }

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• Which Code Should Go Where in MVC Structure

  - by Oguz

  My problem is in somewhere between model and controller.Everything works perfect for me when I use MVC just for crud (create, read, update, delete).I have separate models for each database table .I access these models from controller , to crud them . For example , in contacts application,I have actions (create, read, update, delete) in controller(contact) to use model's (contact) methods (create, read, update, delete). The problem starts when I try to do something more complicated. There are some complex processes which I do not know where should I put them. For example , in registering user process. I can not just finish this process in user model because , I have to use other models too (sending mails , creating other records for user via other models) and do lots of complex validations via other models. For example , in some complex searching processes , I have to access lots of models (articles, videos, images etc.) Or, sometimes , I have to use apis to decide what I will do next or which database model I will use to record data So where is the place to do this complicated processes. I do not want to do them in controllers , Because sometimes I should use these processes in other controllers too. And I do not want to put these process in models because , I use models as database access layers .May be I am wrong,I want to know . Thank you for your answer .

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• How does one decrypt a PDF with an owner password, but no user password?

  - by Tony Meyer

  Although the PDF specification is available from Adobe, it's not exactly the simplest document to read through. PDF allows documents to be encrypted so that either a user password and/or an owner password is required to do various things with the document (display, print, etc). A common use is to lock a PDF so that end users can read it without entering any password, but a password is required to do anything else. I'm trying to parse PDFs that are locked in this way (to get the same privileges as you would get opening them in any reader). Using an empty string as the user password doesn't work, but it seems (section 3.5.2 of the spec) that there has to be a user password to create the hash for the admin password. What I would like is either an explanation of how to do this, or any code that I can read (ideally Python, C, or C++, but anything readable will do) that does this so that I can understand what I'm meant to be doing. Standalone code, rather than reading through (e.g.) the gsview source, would be best.

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• WCF and streaming requests and responses

  - by Cheeso

  Is it correct that in WCF, I cannot have a service write to a stream that is received by the client? My understanding is that streaming is supported in WCF for requests, responses, or both. Is it true that in all cases, the receiver of the stream must invoke Read ? I would like to support a scenario where the receiver of the stream can Write on it. Is this supported? Let me show it this way. The simplest example of Streaming in WCF is the service returning a FileStream to a client. This is a streamed response. The server code is like this: [ServiceContract] public interface IStreamService { [OperationContract] Stream GetData(string fileName); } public class StreamService : IStreamService { public Stream GetData(string filename) { FileStream fs = new FileStream(filename, FileMode.Open) return fs; } } And the client code is like this: StreamDemo.StreamServiceClient client = new WcfStreamDemoClient.StreamDemo.StreamServiceClient(); Stream str = client.GetData(@"c:\path\to\myfile.dat"); do { b = str.ReadByte(); //read next byte from stream ... } while (b != -1); (example taken from http://blog.joachim.at/?p=33) Clear, right? The server returns the Stream to the client, and the client invokes Read on it. Is it possible for the client to provide a Stream, and the server to invoke Write on it? In other words, rather than a pull model - where the client pulls data from the server - it is a push model, where the client provides the "sink" stream and the server writes into it. Is this possible in WCF, and if so, how? What are the config settings required for the binding, interface, etc? The analogy is the Response.OutputStream from an ASP.NET request. In ASPNET, any page can invoke Write on the output stream, and the content is received by the client. Can I do something similar in WCF? Thanks.

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• Understanding CSRF - Simple Question

  - by byronh

  I know this might make me seem like an idiot, I've read everything there is to read about CSRF and I still don't understand how using a 'challenge token' would add any sort of prevention. Please help me clarify the basic concept, none of the articles and posts here on SO I read seemed to really explicitly state what value you're comparing with what. From OWASP: In general, developers need only generate this token once for the current session. After initial generation of this token, the value is stored in the session and is utilized for each subsequent request until the session expires. If I understand the process correctly, this is what happens. I log in at http://example.com and a session/cookie is created containing this random token. Then, every form includes a hidden input also containing this random value from the session which is compared with the session/cookie upon form submission. But what does that accomplish? Aren't you just taking session data, putting it in the page, and then comparing it with the exact same session data? Seems like circular reasoning. These articles keep talking about following the "same-origin policy" but that makes no sense, because all CSRF attacks ARE of the same origin as the user, just tricking the user into doing actions he/she didn't intend. Is there any alternative other than appending the token to every single URL as a query string? Seems very ugly and impractical, and makes bookmarking harder for the user.

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• Parsing multibyte string in PHP

  - by Petr Peller

  I would like to write a (HTML) parser based on state machine but I have doubts how to acctually read/use an input. I decided to load the whole input into one string and then work with it as with an array and hold its index as current parsing position. There would be no problems with single-byte encoding, but in multi-byte encoding each value does not represent a character, but a byte of a character. Example: $mb_string = 'žšcr'; //4 multi-byte characters in UTF-8 for($i=0; $i < 4; $i++) { echo $mb_string[$i], PHP_EOL; } Outputs: L ž L A This means I cannot iterate through the string in a loop to check single characters, because I never know if I am in the middle of an character or not. So the questions are: How do I multi-byte safe read a single character from a string in a performance friendly way? Is it good idea to work with the string as it was an array in this case? How would you read the input?

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• Scheme - Memory System

  - by Eric

  I am trying to make a memory system where you input something in a slot of memory. So what I am doing is making an Alist and the car of the pairs is the memory location and the cdr is the val. I need the program to understand two messages, Read and Write. Read just displaying the memory location selected and the val that is assigned to that location and write changes the val of the location or address. How do I make my code so it reads the location you want it to and write to the location you want it to? Feel free to test this yourself. Any help would be much appreciated. This is what I have: (define make-memory (lambda (n) (letrec ((mem '()) (dump (display mem))) (lambda () (if (= n 0) (cons (cons n 0) mem) mem) (cons (cons (- n 1) 0) mem)) (lambda (msg loc val) (cond ((equal? msg 'read) (display (cons n val))(set! n (- n 1))) ((equal? msg 'write) (set! mem (cons val loc)) (set! n (- n 1)) (display mem))))))) (define mymem (make-memory 100))

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• Using pipes in Linux with C

  - by Dave

  Hi, I'm doing a course in Operating Systems and we're supposed to learn how to use pipes to transfer data between processes. We were given this simple piece of code which demonstrates how to use pipes,but I'm having difficulty understanding it. #include <stdio.h> #include <stdlib.h> #include <unistd.h> main() { int pipefd [2], n; char buff[100] ; if( pipe( pipefd) < 0) { printf("can not create pipe \n"); } printf("read fd = %d, write fd = %d \n", pipefd[0], pipefd[1]); if ( write (pipefd[1],"hello world\n", 12)!= 12) { printf("pipe write error \n"); } if( ( n = read ( pipefd[0] , buff, sizeof ( buff) ) ) <= 0 ) { printf("pipe read error \n"); } write ( 1, buff, n ) ; exit (0); } What does the write function do? It seems to send data to the pipe and also print it to the screen (at least it seems like the second time the write function is called it does this). Does anyone have any suggestions of good websites for learning about topics such as this, FIFO, signals, other basic linux commands used in C?

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• With regards to urllib AttributeError: 'module' object has no attribute 'urlopen'

  - by Matt

  import re import string import shutil import os import os.path import time import datetime import math import urllib from array import array import random filehandle = urllib.urlopen('http://www.google.com/') #open webpage s = filehandle.read() #read print s #display #what i plan to do with it once i get the first part working #results = re.findall('[<td style="font-weight:bold;" nowrap>$][0-9][0-9][0-9][.][0-9][0-9][</td></tr></tfoot></table>]',s) #earnings = '$ ' #for money in results: #earnings = earnings + money[1]+money[2]+money[3]+'.'+money[5]+money[6] #print earnings #raw_input() this is the code that i have so far. now i have looked at all the other forums that give solutions such as the name of the script, which is parse_Money.py, and i have tried doing it with urllib.request.urlopen AND i have tried running it on python 2.5, 2.6, and 2.7. If anybody has any suggestions it would be really welcome, thanks everyone!! --Matt ---EDIT--- I also tried this code and it worked, so im thinking its some kind of syntax error, so if anybody with a sharp eye can point it out, i would be very appreciative. import shutil import os import os.path import time import datetime import math import urllib from array import array import random b = 3 #find URL URL = raw_input('Type the URL you would like to read from[Example: http://www.google.com/] :') while b == 3: #get file name file1 = raw_input('Enter a file name for the downloaded code:') filepath = file1 + '.txt' if os.path.isfile(filepath): print 'File already exists' b = 3 else: print 'Filename accepted' b = 4 file_path = filepath #open file FileWrite = open(file_path, 'a') #acces URL filehandle = urllib.urlopen(URL) #display souce code for lines in filehandle.readlines(): FileWrite.write(lines) print lines print 'The above has been saved in both a text and html file' #close files filehandle.close() FileWrite.close()

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• Perl, regex, extract data from a line

  - by perlnoob

  Im trying to extract part of a line with perl use strict; use warnings; # Set path for my.txt and extract datadir my @myfile = "C:\backups\MySQL\my.txt"; my @datadir = ""; open READMYFILE, @myfile or die "Error, my.txt not found.\n"; while (<READMYFILE>) { # Read file and extract DataDir path if (/C:\backups/gi) { push @datadir, $_; } } # ensure the path was found print @datadir . " \n"; Basically at first im trying to set the location of the my.txt file. Next im trying to read it and pull part of the line with regex. The error Im getting is: Unrecognized escape \m passed through at 1130.pl line 17. I took a look at http://stackoverflow.com/questions/1040657/how-can-i-grab-multiple-lines-after-a-matching-line-in-perl to get an idea of how to read a file and match a line within it, however im not 100% sure I'm doing this right or in the best way. I also seem to produce the error: Error, my.txt not found. But the file does exist in the folder C:\backups\MySQL\

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• Elegant Algorithm for Parsing Data Stream Into Record

  - by Matt Long

  I am interfacing with a hardware device that streams data to my app over Wifi. The data is streaming in just fine. The data contains a character header (DATA:) that indicates a new record has begun. The issues is that the data I receive doesn't necessarily fall on the header boundary, so I have to capture the data until what I've captured contains the header. Then, everything that precedes the header goes into the previous record and everything that comes after it goes into a new record. I have this working, but wondered if anyone has done this before and has a good computer-sciencey way to solve the problem. Here's what I do: Convert the NSData of the current read to an NSString Append the NSString to a placeholder string Check placeholder string for the header (DATA:). If the header is not there, just wait for the next read. If the header exists, append whatever precedes it to a previous record placeholder and hand that placeholder off to an array as a complete record that I can further parse into fields. Take whatever shows up after the header and place it in the record placeholder so that it can be appended to in the next read. Repeat steps 3 - 5. Let me know if you see any flaws with this or have a suggestion for a better way. Seems there should be some design pattern for this, but I can't think of one. Thanks.

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• Who architected / designed C++'s IOStreams, and would it still be considered well-designed by today'

  - by stakx

  First off, it may seem that I'm asking for subjective opinions, but that's not what I'm after. I'd love to hear some well-grounded arguments on this topic. In the hope of getting some insight into how a modern streams / serialization framework ought to be designed, I recently got myself a copy of the book Standard C++ IOStreams and Locales by Angelika Langer and Klaus Kreft. I figured that if IOStreams wasn't well-designed, it wouldn't have made it into the C++ standard library in the first place. After having read various parts of this book, I am starting to have doubts if IOStreams can compare to e.g. the STL from an overall architectural point-of-view. Read e.g. this interview with Alexander Stepanov (the STL's "inventor") to learn about some design decisions that went into the STL. What surprises me in particular: It seems to be unknown who was responsible for IOStreams' overall design (I'd love to read some background information about this — does anyone know good resources?); Once you delve beneath the immediate surface of IOStreams, e.g. if you want to extend IOStreams with your own classes, you get to an interface with fairly cryptic and confusing member function names, e.g. getloc/imbue, uflow/underflow, snextc/sbumpc/sgetc/sgetn, pbase/pptr/epptr (and there's probably even worse examples). This makes it so much harder to understand the overall design and how the single parts co-operate. Even the book I mentioned above doesn't help that much (IMHO). Thus my question: If you had to judge by today's software engineering standards (if there actually is any general agreement on these), would C++'s IOStreams still be considered well-designed? (I wouldn't want to improve my software design skills from something that's generally considered outdated.)

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• Using sqldatareader in asp.net

  - by Phil

  I have this code to get data; s = "select documents.filename, documents.description, documents.filesize from documents, contentdocuments, content where contentdocuments.contentid = content.id and content.id = @contentid and contentdocuments.documentsid = documents.id ORDER BY documents.description" x = New SqlCommand(s, c) x.Parameters.Add("@contentid", SqlDbType.Int) x.Parameters("@contentid").Value = contentid c.Open() r = x.ExecuteReader If r.Read Then DownloadsRepeater.DataSource = r DownloadsRepeater.DataBind() **imagepath = "<img src='images/'" & getimage(r("filename")) & " border='0'** align='absmiddle'" End If c.Close() r.Close() The problem is on the line; imagepath = "<img src='images/'" & getimage(r("filename")) & " The error is; Invalid attempt to read when no data is present. How can I check to make sure data is present and get rid of this error? I thought the 'if r.read' did this? Thanks :EDIT: Function getimage(ByVal strin As String) As String If strin > "" Then dotpos = InStrRev(strin, ".") ext = Right(strin, Len(strin) - dotpos) getimage = ext & ".gif" End If Return getimage End Function

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• Zend_Validate_Abstract custom validator not displaying correct error messages.

  - by Jeremy Dowell

  I have two text fields in a form that I need to make sure neither have empty values nor contain the same string. The custom validator that I wrote extends Zend_Validate_Abstract and works correctly in that it passes back the correct error messages. In this case either: isEmpty or isMatch. However, the documentation says to use addErrorMessages to define the correct error messages to be displayed. in this case, i have attached ->addErrorMessages(array("isEmpty"=>"foo", "isMatch"=>"bar")); to the form field. According to everything I've read, if I return "isEmpty" from isValid(), my error message should read "foo" and if i return "isMatch" then it should read "bar". This is not the case I'm running into though. If I return false from is valid, no matter what i set $this-_error() to be, my error message displays "foo", or whatever I have at index[0] of the error messages array. If I don't define errorMessages, then I just get the error code I passed back for the display and I get the proper one, depending on what I passed back. How do I catch the error code and display the correct error message in my form? The fix I have implemented, until I figure it out properly, is to pass back the full message as the errorcode from the custom validator. This will work in this instance, but the error message is specific to this page and doesn't really allow for re-use of code. Things I have already tried: I have already tried validator chaining so that my custom validator only checks for matches: ->setRequired("true") ->addValidator("NotEmpty") ->addErrorMessage("URL May Not Be Empty") ->addValidator([*customValidator]*) ->addErrorMessage("X and Y urls may not be the same") But again, if either throws an error, the last error message to be set displays, regardless of what the error truly is. I'm not entirely sure where to go from here. Any suggestions?

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• Which book should I choose?

  - by sebastianlarsson

  Hi guys, I'm looking for a good read on object oriented design. The two books I'm currently looking Head First Design Patterns and Head First Object object-oriented analysis & design. They seem very similar when looking at the contents and browsing through available sample text. Which one would be the best choice? About myself: I have a bachelor in computer science and I am currently studying Msc. Software Quality Engineering (read Software Engineering with focus on Quality). I am already confident in object-oriented design and have a lot of programming courses in my backpack. I have done games in c++, courses in advanced java programming (I am SCJP certified), but my preferred language is C#. I have also worked with Java for the last 7 months while studying. I am currently also studying for certificates in C# (apart from my usual studies). So I believe I have the prerequisites of actually understanding the contents of both books. Reason: I just want to be better and keep evolving as a programmer. I think it is fun. I believe Bert Bates and Kathy Sierra are involved in both these books and I have previously read their SCJP preparation book in java. I really do enjoy their style of writing. Other books which I am considering are: Clean Code: A Handbook Of Agile Software Craftsmanship Thx in advance Sebastian

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• Gadget vista error var with flyout

  - by Jiinn

  hello ! i have a problem with a variable for the flyout : var friendsUser = ""; var friendsMdp = ""; System.Gadget.Settings.write("variableName", variableName); System.Gadget.settingsUI = "Settings.html"; System.Gadget.onSettingsClosed = SettingsClosed; System.Gadget.Flyout.visible = SettingsClosed; function SettingsClosed() { variableName = System.Gadget.Settings.read("variableName"); friendsUser = System.Gadget.Settings.read("friendUser"); friendsMdp = System.Gadget.Settings.read("friendMdp"); setContentText(); } function flyFriends() { System.Gadget.Flyout.file = 'friends.htm'; System.Gadget.Flyout.show = true ; var flyoutDiv = System.Gadget.Flyout.document.parentWindow; flyoutDiv.gMyVar = friendsUser; flyoutDiv.gMyVar2 = friendsMdp; } If i use this my flyout var is undefined , and if i write : var friendsUser = "test"; i have Test in var and after use setting i have nothing ... if i write var in flyoutDiv before System.Gadget.Flyout.show = true ; gadget bug . my settings dont have a problem, but the refresh of the var ... have you a idea ? thank you for all !

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• 1k of Program Space, 64 bytes of RAM. Is assembly an absolute must?

  - by Earlz

  (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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