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• ODBC and NLS_LANG

  - by Michael S.

  Let's say that I've created two different program executables, e.g. in C++. For some reason, the two programs internals representation of text are different from each other. Let's say the first program is using text representation A and the other text representation B. It could be a specific 8-bit ANSI codepage, Unicode/UTF-8 or Unicode/UTF-16 or whatever. Now each program want to communicate text (add/retrieve data) to/from the same database table on a (database) server. Each program communicates with the database through ODBC. So the programs do not know what database system they they are communicating with. In this specific case through the database is actually a Oracle RDMS database and the database server administrator has setup the database to use UTF-8. On the system on which the programs are running an appropriate ODBC driver is available, so that the programs can connect through ODBC. Each program will treat and convert from the ODBC data type SQL_C_CHAR to its internal text representation appropriately. I assume that the programs cannot do no other than to assume a specific encoding returned for SQL_C_CHAR text. If not the programs has to be told which encoding that is. For Oracle, I know that the NLS_LANG environment variable can be used on the client. I assume it affects the ODBC driver (related to SQL_C_CHAR) to convert from a specific encoding (as given by NLS_LANG) to the internal encoding of the database (in this example UTF-8) and vice-versa. If the machine running my programs are having a NLS_LANG this setting will affect the byte sequences returned for SQL_C_CHAR so my programs cannot suddenly assume a specific encoding for the text returned via SQL_C_CHAR. Is it possible to setup the ODBC connection (preferably programmatically at runtime), so that it takes care of text conversions appropriately for the two programs, i.e. from/to representation to/from UTF-8 and from/to representation B to/from UTF-8? Regards, /Michael PS. As the programs are connecting through ODBC I don't think it would be nice that they should now anything about NLS_LANG as this is a Orcacle specific environment variable.

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• Starting a process in one HTTP call and getting results in another

  - by KillianDS

  Hi, I'm writing a very simple testing framework for my application, the design isn't perfect, but I don't have time to write something more complex. Essentially, I have a client and server-application, on my server I want a small python web server to start the server application with given test sequences on a GET or POST call. Also, the application prints some testdata to stderr which I'd like to catch and return in another HTTP call. At the moment I have this: from subprocess import Popen, PIPE from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer p = None class MyHandler(BaseHTTPRequestHandler): def do_GET(self): global p if self.path.endswith("start/"): p = Popen(["./bin/Release/simplex264","BBB-360","127.0.0.1"], stderr=PIPE) print 'started' return elif self.path.endswith("getResults/"): self.wfile.write(p.stderr.read()) return self.send_error(404,'File Not Found: %s' % self.path) def main(): try: server = HTTPServer(('localhost', 9876), MyHandler) print 'Started server...' server.serve_forever() except KeyboardInterrupt: print 'Shutting down...' server.socket.close() if __name__ == '__main__': main() Which 'works', except for one part, when I try to open http://localhost:9876/start/, it does not return before the process ended. However, the 'started' appears in my shell immediately (I added this because I thought the Popen call would only return after execution). I do not know the perfect inner workings of Popen and BaseHTTPRequestHandler however and do not really know where it goes wrong. Is there any way to make this work asynchronously?

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• How should I avoid memoization causing bugs in Ruby?

  - by Andrew Grimm

  Is there a consensus on how to avoid memoization causing bugs due to mutable state? In this example, a cached result had its state mutated, and therefore gave the wrong result the second time it was called. class Greeter def initialize @greeting_cache = {} end def expensive_greeting_calculation(formality) case formality when :casual then "Hi" when :formal then "Hello" end end def greeting(formality) unless @greeting_cache.has_key?(formality) @greeting_cache[formality] = expensive_greeting_calculation(formality) end @greeting_cache[formality] end end def memoization_mutator greeter = Greeter.new first_person = "Bob" # Mildly contrived in this case, # but you could encounter this in more complex scenarios puts(greeter.greeting(:casual) << " " << first_person) # => Hi Bob second_person = "Sue" puts(greeter.greeting(:casual) << " " << second_person) # => Hi Bob Sue end memoization_mutator Approaches I can see to avoid this are: greeting could return a dup or clone of @greeting_cache[formality] greeting could freeze the result of @greeting_cache[formality]. That'd cause an exception to be raised when memoization_mutator appends strings to it. Check all code that uses the result of greeting to ensure none of it does any mutating of the string. Is there a consensus on the best approach? Is the only disadvantage of doing (1) or (2) decreased performance? (I also suspect freezing an object may not work fully if it has references to other objects) Side note: this problem doesn't affect the main application of memoization: as Fixnums are immutable, calculating Fibonacci sequences doesn't have problems with mutable state. :)

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• jQuery XML loading and then innerfade effect

  - by Ryan Max

  Hello, I think I can explain myself without code, so for brevity's sake here we go: I am using jquery to pull data from an xml and put it into a ul on the page with each xml entry as a li. This is working great! However, what I am trying to do afterwards is use the innerfade plugin to make a simple animation between each of the li's. It's not working though, as it is still just loading the static list with each item visible (whereas if innerfade was working it would only display the first....then fade into the second, etc) It's not an innerfade problem however, because if I add the list in manually to the page (not injecting it with jquery) then the innerfade works fine. I'm relatively new to DOM scripting, so I think I am missing something here. I'm not quite sure how jQuery sequences everything, and I'm having trouble phrasing my question in a search engine friendly manner so here I am. Is it possible to have jquery pull the data from xml, then inject it into the page, then have innerfade work it's magic? Or am I thinking about this the wrong way? xml code: $.ajax({ type: "GET", url: "xml/playlist.xml", dataType: "xml", success: function(xml) { $(xml).find('song').each(function(){ var name = $(this).attr('title'); var date = $(this).attr('artist'); var message = $(this).attr('path'); $('<li></li>').html('<span id="an_name">'+name+'</span><span id="an_date">'+date+'</span><span id="an_message">'+message+'</span>').appendTo('#anniversary'); }); } }); innerfade code: <script type="text/javascript"> jQuery.noConflict(); jQuery(document).ready( function(){ jQuery('#anniversary').innerfade({ speed: 1000, timeout: 5000, type: 'sequence', }); });

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• Setting an Excel Range with an Array using Python and comtypes?

  - by technomalogical

  Using comtypes to drive Python, it seems some magic is happening behind the scenes that is not converting tuples and lists to VARIANT types: # RANGE(“C14:D21”) has values # Setting the Value on the Range with a Variant should work, but # list or tuple is not getting converted properly it seems >>>from comtypes.client import CreateObject >>>xl = CreateObject("Excel.application") >>>xl.Workbooks.Open(r'C:\temp\my_file.xlsx') >>>xl.Visible = True >>>vals=tuple([(x,y) for x,y in zip('abcdefgh',xrange(8))]) # creates: #(('a', 0), ('b', 1), ('c', 2), ('d', 3), ('e', 4), ('f', 5), ('g', 6), ('h', 7)) >>>sheet = xl.Workbooks[1].Sheets["Sheet1"] >>>sheet.Range["C14","D21"].Value() (('foo',1),('foo',2),('foo',3),('foo',4),('foo',6),('foo',6),('foo',7),('foo',8)) >>>sheet.Range["C14","D21"].Value[()] = vals # no error, this blanks out the cells in the Range According to the comtypes docs: When you pass simple sequences (lists or tuples) as VARIANT parameters, the COM server will receive a VARIANT containing a SAFEARRAY of VARIANTs with the typecode VT_ARRAY | VT_VARIANT. This seems to be inline with what MSDN says about passing an array to a Range's Value. I also found this page showing something similar in C#. Can anybody tell me what I'm doing wrong? EDIT I've come up with a simpler example that performs the same way (in that, it does not work): >>>from comtypes.client import CreateObject >>>xl = CreateObject("Excel.application") >>>xl.Workbooks.Add() >>>sheet = xl.Workbooks[1].Sheets["Sheet1"] # at this point, I manually typed into the range A1:B3 >>> sheet.Range("A1","B3").Value() ((u'AAA', 1.0), (u'BBB', 2.0), (u'CCC', 3.0)) >>>sheet.Range("A1","B3").Value[()] = [(x,y) for x,y in zip('xyz',xrange(3))] # Using a generator expression, per @Mike's comment # However, this still blanks out my range :(

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• Maximum number of characters using keystrokes A, Ctrl+A, Ctrl+C and Ctrl+V

  - by munda

  This is an interview question from google. I am not able to solve it by myself. Can somebody shed some light? Write a program to print the sequence of keystrokes such that it generates the maximum number of character 'A's. You are allowed to use only 4 keys: A, Ctrl+A, Ctrl+C and Ctrl+V. Only N keystrokes are allowed. All Ctrl+ characters are considered as one keystroke, so Ctrl+A is one keystroke. For example, the sequence A, Ctrl+A, Ctrl+C, Ctrl+V generates two A's in 4 keystrokes. Ctrl+A is Select All Ctrl+C is Copy Ctrl+V is Paste I did some mathematics. For any N, using x numbers of A's , one Ctrl+A, one Ctrl+C and y Ctrl+V, we can generate max ((N-1)/2)2 number of A's. For some N M, it is better to use as many Ctrl+A's, Ctrl+C and Ctrl+V sequences as it doubles the number of A's. The sequence Ctrl+A, Ctrl+V, Ctrl+C will not overwrite the existing selection. It will append the copied selection to selected one.

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• general learning methodology

  - by momo

  just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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• emacs -- keybind questions

  - by user565739

  I have successfully used Ctrl+Shift+Up ' Ctrl+Shift+down ' Ctrl+Shift+left' Ctrl+Shift+Right to different commands. But when I tried to use Ctrl+s to the command save-buffer and Ctrl+Shift+s, which is equivalent to Ctrl+S, to another command, it has some problem. save-buffer works fine, but when I type Ctrl+Shift+s, it excute the command save-buffer. I used Ctrl+q to find the control sequences of Ctrl+s and Ctrl+Shift+S, I get the same result, which is ^S. I expect that I will get ^s for Ctrl+s, but it doesn't. Anyone knows the reason? Another queston is: I use Ctrl+c for the command killing-ring-save. In this case, all commands (which are of large number) begin with Ctrl+c don't work now. Is there a way to replace the prefix Ctrl+c by another customized prefix? I may pose my question in the wrong direction. I use ctrl+c as killing-ring-save. It works fine in emacs (no mode). But if I open a .c file (C-mode), then when I type Ctrl+c, it waits me to type another key. I think in this case, ctrl+c is regarded as a prefix. In this case, I need the following modifications: Using a custom defined prefix, say Ctrl+a, as Ctrl+c ; Remove the prefix Ctrl+c ; Using Ctrl+c as killing-ring-save. I add the following to my ~/.emacs : (defun my-c-initialization-hook () (define-key c-mode-base-map (kbd "C-a") mode-specific-map) (define-key c-mode-base-map (kbd "C-c") 'kill-ring-save)) (add-hook 'c-initialization-hook 'my-c-initialization-hook) But this doesn't work. Ctrl+c is still regarded as a prefix, so I can't use it as kill-ring-save. Furthermore, if I type Ctrl+a Ctrl+c, it said it's not defined. (I thought it will have the same result as I type Ctrl+c Ctrl+c)

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• Find min. "join" operations for sequence

  - by utyle

  Let's say, we have a list/an array of positive integers x1, x2, ... , xn. We can do a join operation on this sequence, that means that we can replace two elements that are next to each other with one element, which is sum of these elements. For example: - array/list: [1;2;3;4;5;6] we can join 2 and 3, and replace them with 5; we can join 5 and 6, and replace them with 11; we cannot join 2 and 4; we cannot join 1 and 3 etc. Main problem is to find minimum join operations for given sequence, after which this sequence will be sorted in increasing order. Note: empty and one-element sequences are sorted in increasing order. Basic examples: for [4; 6; 5; 3; 9] solution is 1 (we join 5 and 3) for [1; 3; 6; 5] solution is also 1 (we join 6 and 5) What I am looking for, is an algorithm that solve this problem. It could be in pseudocode, C, C++, PHP, OCaml or similar (I mean: I woluld understand solution, if You wrote solution in one of these languages). I would appreciate Your help.

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• Programming time schedule for porting a program.

  - by Lothar

  I'm working on a large program which has an abstracted GUI API. It is very GUI based, many dialogs and a few nasty features which rely heavily on the message flow of the GUI (correct sequences of focus/mouse/active handling etc.) - not easy to port I now want to port it from the currently used FOX Toolkit to native Cocoa/MFC. I give myself a timeframe until the end of the year but my main work will be to continue development work with the existing toolkit, but there is no planned release for end customers before both tasks are done. My question is how should i spend my time? Stop working on the main program and do a 90% port (about 3 month) of the GUI first Splitting everything into smaller sessions of one month each. Assigning Monday/Tuesday to the GUI project and the rest of the week for the app. Finishing the App first, then port. I think there are three arguments which i need to balance. Motivation, i want to see something going on on both projects Brain Input Overflow, both tasks require a lot of detail information in my brain and sometimes enough is just enough. I guess the porting is intervowen so porting would also require a lot of code changes in the existing code and the new code that will be written in the meantime.

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• Pairs from single list

  - by Apalala

  Often enough, I've found the need to process a list by pairs. I was wondering which would be the pythonic and efficient way to do it, and found this on Google: pairs = zip(t[::2], t[1::2]) I thought that was pythonic enough, but after a recent discussion involving idioms versus efficiency, I decided to do some tests: import time from itertools import islice, izip def pairs_1(t): return zip(t[::2], t[1::2]) def pairs_2(t): return izip(t[::2], t[1::2]) def pairs_3(t): return izip(islice(t,None,None,2), islice(t,1,None,2)) A = range(10000) B = xrange(len(A)) def pairs_4(t): # ignore value of t! t = B return izip(islice(t,None,None,2), islice(t,1,None,2)) for f in pairs_1, pairs_2, pairs_3, pairs_4: # time the pairing s = time.time() for i in range(1000): p = f(A) t1 = time.time() - s # time using the pairs s = time.time() for i in range(1000): p = f(A) for a, b in p: pass t2 = time.time() - s print t1, t2, t2-t1 These were the results on my computer: 1.48668909073 2.63187503815 1.14518594742 0.105381965637 1.35109519958 1.24571323395 0.00257992744446 1.46182489395 1.45924496651 0.00251388549805 1.70076990128 1.69825601578 If I'm interpreting them correctly, that should mean that the implementation of lists, list indexing, and list slicing in Python is very efficient. It's a result both comforting and unexpected. Is there another, "better" way of traversing a list in pairs? Note that if the list has an odd number of elements then the last one will not be in any of the pairs. Which would be the right way to ensure that all elements are included? I added these two suggestions from the answers to the tests: def pairwise(t): it = iter(t) return izip(it, it) def chunkwise(t, size=2): it = iter(t) return izip(*[it]*size) These are the results: 0.00159502029419 1.25745987892 1.25586485863 0.00222492218018 1.23795199394 1.23572707176 Results so far Most pythonic and very efficient: pairs = izip(t[::2], t[1::2]) Most efficient and very pythonic: pairs = izip(*[iter(t)]*2) It took me a moment to grok that the first answer uses two iterators while the second uses a single one. To deal with sequences with an odd number of elements, the suggestion has been to augment the original sequence adding one element (None) that gets paired with the previous last element, something that can be achieved with itertools.izip_longest().

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• Auto increment with a Unit Of Work

  - by Derick

  Context I'm building a persistence layer to abstract different types of databases that I'll be needing. On the relational part I have mySQL, Oracle and PostgreSQL. Let's take the following simplified MySQL tables: CREATE TABLE Contact ( ID varchar(15), NAME varchar(30) ); CREATE TABLE Address ( ID varchar(15), CONTACT_ID varchar(15), NAME varchar(50) ); I use code to generate system specific alpha numeric unique ID's fitting 15 chars in this case. Thus, if I insert a Contact record with it's Addresses I have my generated Contact.ID and Address.CONTACT_IDs before committing. I've created a Unit of Work (amongst others) as per Martin Fowler's patterns to add transaction support. I'm using a key based Identity Map in the UoW to track the changed records in memory. It works like a charm for the scenario above, all pretty standard stuff so far. The question scenario comes in when I have a database that is not under my control and the ID fields are auto-increment (or in Oracle sequences). In this case I do not have the db generated Contact.ID beforehand, so when I create my Address I do not have a value for Address.CONTACT_ID. The transaction has not been started on the DB session since all is kept in the Identity Map in memory. Question: What is a good approach to address this? (Avoiding unnecessary db round trips) Some ideas: Retrieve the last ID: I can do a call to the database to retrieve the last Id like: SELECT Auto_increment FROM information_schema.tables WHERE table_name='Contact'; But this is MySQL specific and probably something similar can be done for the other databases. If do this then would need to do the 1st insert, get the ID and then update the children (Address.CONTACT_IDs) – all in the current transaction context.

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• How to properly set button phase after dragging over button?

  - by irobeth

  I have a class (mxml) that extends Button while implementing drag/drop support. When I drag one of them onto another, the drag receiver stays stuck in its 'over' phase until I click on it (As if something about DragManager.acceptDragDrop is preventing the MouseEvent from getting to button) Is there a way to make a button re-evaluate its phase after the drop? I've tried fabricating a MouseEvent and sending it to rollOverHandler with no luck. This resembles the scenario in Button.as (lines 2606-2647) described like Drag over and up mouse down while out of Button roll over Button - stay in "up" phase mouse up while over Button - "over" phase continue with step 2 of first three sequences above This is my drag/drop handler private function dragDropHandler(event:DragEvent):void { trace("dropped"); var ib : IconButton = (event.dragInitiator as IconButton); if(this.data is Section) { if(ib.data is Item) { trace("ITEM"); //move an item into a section. var ae : AldonaEvent = new AldonaEvent(AldonaEvent.MOVE); ae.data = ib.data; dispatchEvent(ae); } else if(ib.data is Section) { trace("SECTION"); //change a section's parent. var ae : AldonaEvent = new AldonaEvent(AldonaEvent.MOVE); ae.data = ib.data; dispatchEvent(ae); } } //you can only drag stuff into sections. }

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• How do people handle foreign keys on clients when synchronizing to master db

  - by excsm

  Hi, I'm writing an application with offline support. i.e. browser/mobile clients sync commands to the master db every so often. I'm using uuid's on both client and server-side. When synching up to the server, the servre will return a map of local uuids (luid) to server uuids (suid). Upon receiving this map, clients updated their records suid attributes with the appropriate values. However, say a client record, e.g. a todo, has an attribute 'list_id' which holds the foreign key to the todos' list record. I use luids in foreign_keys on clients. However, when that attribute is sent over to the server, it would dirty the server db with luids rather than the suid the server is using. My current solution, is for the master server to keep a record of the mappings of luids to suids (per client id) and for each foreign key in a command, look up the suid for that particular client and use the suid instead. I'm wondering wether others have come across thus problem and if so how they have solved it? Is there a more efficient, simpler way? I took a look at this question "Synchronizing one or more databases with a master database - Foreign keys (5)" and someone seemed to suggest my current solution as one option, composite keys using suids and autoincrementing sequences and another option using -ve ids for client ids and then updating all negative ids with the suids. Both of these other options seem like a lot more work. Thanks, Saimon

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• Fluent NHibernate AutoMap

  - by Markus

  Hi. I have a qouestion regarding the AutoMap xml generation. I have two classes: public class User { virtual public Guid Id { get; private set; } virtual public String Name { get; set; } virtual public String Email { get; set; } virtual public String Password { get; set; } virtual public IList<OpenID> OpenIDs { get; set; } } public class OpenID { virtual public Guid Id { get; private set; } virtual public String Provider { get; set; } virtual public String Ticket { get; set; } virtual public User User { get; set; } } The generated sequences of xml files are: For User class: <bag name="OpenIDs"> <key> <column name="User_Id" /> </key> <one-to-many class="BL_DAL.Entities.OpenID, BL_DAL, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> </bag> For OpenID class: <many-to-one class="BL_DAL.Entities.User, BL_DAL, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="User"> <column name="User_id" /> </many-to-one> I don't see the inverse=true attribute for the User mapping. Is it a normal behavior, or I made a mistake somewhere?

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• Heroku only initializes some of my models.

  - by JayX

  So I ran heroku db:push And it returned Sending schema Schema: 100% |==========================================| Time: 00:00:08 Sending indexes schema_migrat: 100% |==========================================| Time: 00:00:00 projects: 100% |==========================================| Time: 00:00:00 tasks: 100% |==========================================| Time: 00:00:00 users: 100% |==========================================| Time: 00:00:00 Sending data 8 tables, 70,551 records groups: 100% |==========================================| Time: 00:00:00 schema_migrat: 100% |==========================================| Time: 00:00:00 projects: 100% |==========================================| Time: 00:00:00 tasks: 100% |==========================================| Time: 00:00:02 authenticatio: 100% |==========================================| Time: 00:00:00 articles: 100% |==========================================| Time: 00:08:27 users: 100% |==========================================| Time: 00:00:00 topics: 100% |==========================================| Time: 00:01:22 Resetting sequences And when I went to heroku console This worked >> Task => Task(id: integer, topic: string, content: string, This worked >> User => User(id: integer, name: string, email: string, But the rest only returned something like >> Project NameError: uninitialized constant Project /home/heroku_rack/lib/console.rb:150 /home/heroku_rack/lib/console.rb:150:in `call' /home/heroku_rack/lib/console.rb:28:in `call' >> Authentication NameError: uninitialized constant Authentication /home/heroku_rack/lib/console.rb:150 /home/heroku_rack/lib/console.rb:150:in `call' update 1: And when I typed >> ActiveRecord::Base.connection.tables it returned => ["projects", "groups", "tasks", "topics", "articles", "schema_migrations", "authentications", "users"] Using heroku's SQL console plugin I got SQL> show tables +-------------------+ | table_name | +-------------------+ | authentications | | topics | | groups | | projects | | schema_migrations | | tasks | | articles | | users | +-------------------+ So I think they are existing in heroku's database already. There is probably something wrong with rack db:migrate update 2: I ran rack db:migrate locally in both production and development modes and nothing wrong happened. But when I ran it on heroku it only returned: $ heroku rake db:migrate (in /disk1/home/slugs/389817_1c16250_4bf2-f9c9517b-bdbd-49d9-8e5a-a87111d3558e/mnt) $ Also, I am using sqlite3 update 3: so I opened up heroku console and typed in the following command class Authentication < ActiveRecord::Base;end Amazingly I was able to call Authentication class, but once I exited, nothing was changed.

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• finding long repeated substrings in a massive string

  - by Will

  I naively imagined that I could build a suffix trie where I keep a visit-count for each node, and then the deepest nodes with counts greater than one are the result set I'm looking for. I have a really really long string (hundreds of megabytes). I have about 1 GB of RAM. This is why building a suffix trie with counting data is too inefficient space-wise to work for me. To quote Wikipedia's Suffix tree: storing a string's suffix tree typically requires significantly more space than storing the string itself. The large amount of information in each edge and node makes the suffix tree very expensive, consuming about ten to twenty times the memory size of the source text in good implementations. The suffix array reduces this requirement to a factor of four, and researchers have continued to find smaller indexing structures. And that was wikipedia's comments on the tree, not trie. How can I find long repeated sequences in such a large amount of data, and in a reasonable amount of time (e.g. less than an hour on a modern desktop machine)? (Some wikipedia links to avoid people posting them as the 'answer': Algorithms on strings and especially Longest repeated substring problem ;-) )

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• C preprocessor problem in Microsoft Visual Studio 2010

  - by Remo.D

  I've encountered a problem with the new Visual C++ in VS 2010. I've got a header with the following defines: #define STC(y) #y #define STR(y) STC(\y) #define NUM(y) 0##y The intent is that you can have some constant around like #define TOKEN x5A and then you can have the token as a number or as a string: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\x5A" This is the expected behavior under the the substitution rules of macros arguments and so far it has worked well with gcc, open watcom, pellesC (lcc), Digital Mars C and Visual C++ in VS2008 Express. Today I recompiled the library with VS2010 Express only to discover that it doesn't work anymore! Using the new version I would get: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\y" It seems that the new preprocessor treats \y as an escape sequence even within a macro body which is a non-sense as escape sequences only have a meaning in literal strings. I suspect this is a gray area of the ANSI standard but even if the original behavior was mandated by the standard, MS VC++ is not exactly famous to be 100% ANSI C compliant so I guess I'll have to live with the new behavior of the MS compiler. Given that, does anybody have a suggestion on how to re-implement the original macros behavior with VS2010?

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• Exploiting Path Traversal Vulnerability

  - by Maputo

  I have a Java Web App running on Tomcat on which I'm supposed to exploit Path traversal vulnerability. There is a section (in the App) at which I can upload a .zip file, which gets extracted in the server's /tmp directory. The content of the .zip file is not being checked, so basically I could put anything in it. I tried putting a .jsp file in it and it extracts perfectly. My problem is that I don't know how to reach this file as a "normal" user from browser. I tried entering ../../../tmp/somepage.jsp in the address bar, but Tomcat just strips the ../ and gives me http://localhost:8080/tmp/ resource not available. Ideal would be if I could somehow rename the somepage.jsp so that it gets extracted in the web directory of the Web App. But then, the Linux filesystem disallows slashes in filenames (e.g. ../../home/webapp/somepage.jsp). Are there maybe any escape sequences that would translate to / after extracting? Any ideas would be highly appreciated. Note: This is a school project in a Security course where I'm supposed to locate vulnerabilities and correct them. Not trying to harm anyone...

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• wxpython - Running threads sequentially without blocking GUI

  - by ryantmer

  I've got a GUI script with all my wxPython code in it, and a separate testSequences module that has a bunch of tasks that I run based on input from the GUI. The tasks take a long time to complete (from 20 seconds to 3 minutes), so I want to thread them, otherwise the GUI locks up while they're running. I also need them to run one after another, since they all use the same hardware. (My rationale behind threading is simply to prevent the GUI from locking up.) I'd like to have a "Running" message (with varying number of periods after it, i.e. "Running", "Running.", "Running..", etc.) so the user knows that progress is occurring, even though it isn't visible. I'd like this script to run the test sequences in separate threads, but sequentially, so that the second thread won't be created and run until the first is complete. Since this is kind of the opposite of the purpose of threads, I can't really find any information on how to do this... Any help would be greatly appreciated. Thanks in advance! gui.py import testSequences from threading import Thread #wxPython code for setting everything up here... for j in range(5): testThread = Thread(target=testSequences.test1) testThread.start() while testThread.isAlive(): #wait until the previous thread is complete time.sleep(0.5) i = (i+1) % 4 self.status.SetStatusText("Running"+'.'*i) testSequences.py import time def test1(): for i in range(10): print i time.sleep(1) (Obviously this isn't the actual test code, but the idea is the same.)

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• Python, web log data mining for frequent patterns

  - by descent

  Hello! I need to develop a tool for web log data mining. Having many sequences of urls, requested in a particular user session (retrieved from web-application logs), I need to figure out the patterns of usage and groups (clusters) of users of the website. I am new to Data Mining, and now examining Google a lot. Found some useful info, i.e. querying Frequent Pattern Mining in Web Log Data seems to point to almost exactly similar studies. So my questions are: Are there any python-based tools that do what I need or at least smth similar? Can Orange toolkit be of any help? Can reading the book Programming Collective Intelligence be of any help? What to Google for, what to read, which relatively simple algorithms to use best? I am very limited in time (to around a week), so any help would be extremely precious. What I need is to point me into the right direction and the advice of how to accomplish the task in the shortest time. Thanks in advance!

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• What encoding does c32rtomb convert to?

  - by R. Martinho Fernandes

  The functions c32rtomb and mbrtoc32 from <cuchar>/<uchar.h> are described in the C Unicode TR (draft) as performing conversions between UTF-321 and "multibyte characters". (...) If s is not a null pointer, the c32rtomb function determines the number of bytes needed to represent the multibyte character that corresponds to the wide character given by c32 (including any shift sequences), and stores the multibyte character representation in the array whose first element is pointed to by s. (...) What is this "multibyte character representation"? I'm actually interested in the behaviour of the following program: #include <cassert> #include <cuchar> #include <string> int main() { std::u32string u32 = U"this is a wide string"; std::string narrow = "this is a wide string"; std::string converted(1000, '\0'); char* ptr = &converted[0]; std::mbstate_t state {}; for(auto u : u32) { ptr += std::c32rtomb(ptr, u, &state); } converted.resize(ptr - &converted[0]); assert(converted == narrow); } Is the assertion in it guaranteed to hold1? 1 Working under the assumption that __STDC_UTF_32__ is defined.

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• Can an administration extraction of an MSI file perform registry and/or system wide changes?

  - by Wil

  I am always getting MSI (or setup EXEs which are basically MSI) files, and half the time they really do not need to be a setup. Microsoft is probably one of the biggest sources - almost every time I want to download a little source code sample, it has a MSI which if you install, only usually has three files. I would rather not do an install and add it to the add/remove programs and who knows what else (although I am sure it wouldn't be that bad) for the sake of three files! For this reason, I always use the following command: MSIEXEC /a <filename.msi> /qb TARGETDIR=<directory name> Now, this works fine and I have never had problems... However, I was just browsing some articles on Technet and found the following resource about administration installs. Apparently, MSI files can have two sequences: The AdminUISequence Table and the AdminExecuteSequence Table. I am not so worried about the AdminUISequence Table as it states that "The installer skips the actions in this table if the user interface level is set to basic UI or no UI", and this is what the /qb switch I use does. However, there is nothing similar written against AdminExecuteSequence Table. I realise that many people who write MSI files simply do it for a single end user and probably do not even touch the admin install options, however, is it possible for them to set items that can affect the system and if so, is there a fail proof way of extracting? I do already use 7-zip, however despite it being on the "supported" page, MSI support is lacking... well... completely sucks. It looses the file names and is generally useless. They have a bug which was closed with no reason/resolution over three years ago, and I opened a forum post and haven't had a reply. I would not really want to install any additional programs if I could help it and just want peoples opinions on this. Thanks. edit - Should also say, I run with UAC on, and I have never ever had a elevation prompt whilst performing the MSIEXEC operation, so I am guessing I have never had a system wide change, however, I am still curious as to if it is possible... As if changes (even just to the user) are possible I would do this locally/in a VM and never on a server or place of importance!

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• Having trouble Getting "RTSP over HTTP"

  - by Muhammad Adeel Zahid

  There is an axis camera that is connected to our site (camba.tv) through axis one click connection component (which acts as proxy). We can communicate with this camera only through http by setting the proxy to our OCCC server's address. If we want to get RTSP streams (h.264) we are only left with "RTSP over HTTP" option. For this I have followed axis VAPIX 3 documentation section 3.3. I issue requests through fiddler but don't get any response. But when i put the URL (axrtsphttp://1.00408CBEA38B/axis-media/media.amp) in windows media player (with proxy set to OCCC server 212.78.237.156:3128) the player is able to get RTSP stream over HTTP after logging in. I have created a request trace of communication between camera and windows media player through wireshark and the request that brings the stream looks like http://1.00408cbea38b/axis-media/media.amp HTTP/1.1 x-sessioncookie: 619 User-Agent: Axis AMC Host: 1.00408CBEA38B Proxy-Connection: Keep-Alive Pragma: no-cache Authorization: Digest username="root",realm="AXIS_00408CBEA38B",nonce="000a8b40Y0100409c13ac7e6cceb069289041d8feb1691",uri="/axis-media/media.amp",cnonce="9946e2582bd590418c9b70e1b17956c7",nc=00000001,response="f3cab86fc84bfe33719675848e7fdc0a",qop="auth" HTTP/1.0 200 OK Content-Type: application/x-rtsp-tunnelled Date: Tue, 02 Nov 2010 11:45:23 GMT RTSP/1.0 200 OK CSeq: 1 Content-Type: application/sdp Content-Base: rtsp://1.00408CBEA38B/axis-media/media.amp/ Date: Tue, 02 Nov 2010 11:45:23 GMT Content-Length: 410 v=0 o=- 1288698323798001 1288698323798001 IN IP4 1.00408CBEA38B s=Media Presentation e=NONE c=IN IP4 0.0.0.0 b=AS:50000 t=0 0 a=control:* a=range:npt=0.000000- m=video 0 RTP/AVP 96 b=AS:50000 a=framerate:30.0 a=transform:1,0,0;0,1,0;0,0,1 a=control:trackID=1 a=rtpmap:96 H264/90000 a=fmtp:96 packetization-mode=1; profile-level-id=420029; sprop-parameter-sets=Z0IAKeNQFAe2AtwEBAaQeJEV,aM48gA== RTSP/1.0 200 OK CSeq: 2 Session: 3F4763D8; timeout=60 Transport: RTP/AVP/TCP;unicast;interleaved=0-1;ssrc=060922C6;mode="PLAY" Date: Tue, 02 Nov 2010 11:45:24 GMT RTSP/1.0 200 OK CSeq: 3 Session: 3F4763D8 Range: npt=0- RTP-Info: url=rtsp://1.00408CBEA38B/axis-media/media.amp/trackID=1;seq=7392;rtptime=4190934902 Date: Tue, 02 Nov 2010 11:45:24 GMT [Binary Stream Content] But when i copy this request to fiddler, I only get 200 status code with content-type set to application/x-rtsp-tunneled and there is no stream data. The only thing i do different with stream is to use Basic in authorization header instead of Digest and I do not get 401 (Un authorized) status code. Can anyone explain what's happening here? How can I write request sequences to get stream in fiddler? If it is needed, I can upload the wireshark request dump somewhere.

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• What would cause my SendMail server not to acknowledge receiving a TCP Sequence?

  - by Mike B

  My TCP/IP Stack knowledge is a little rusty so please bear with me.... I have a CentOS 5.7 server with SendMail and am having seeing intermittent timeout issues sending email (particularly larger email) to other remote domains. It doesn't happen with all attachments or recipient domains. Just some. After some extended troubleshooting, I think I've narrowed it down to TCP Sequences not being acknowledged. Here's a breakdown of the TCP session from a packet capture I collected directly on my MTA (fooMTA): Packet 1 - 11: Standard TCP handshake followed by initial SMTP conversation. No errors. Packet #12 Recipient MTA: TCP sequence 231. Ack 91. Packet #13 FooMTA: TCP sequence 91. Ack 305. Packet #14 FooMTA: TCP sequence 1115. Ack 305. Packet #15 Recipient MTA: TCP sequence 305. Ack 2495. Packet #16 FooMTA: TCP sequence 2495. Ack 305. Packet #17 FooMTA: TCP sequence 5255. Ack 305. Packet #18: Recipient MTA: TCP sequence 305. Ack 5255. Packet #19: FooMTA: TCP sequence 6635. Ack 305. Packet #20: FooMTA: TCP sequence 8015. Ack 305. Packet #21: Recipient MTA: TCP Sequence 305. Ack 8015. Packet #22: FooMTA: TCP Sequence 10775. Ack 305. Packet #23: FooMTA: TCP Sequence 13535. Ack 305. Packet #24: Recipient MTA: TCP sequence 305. Ack 10775 Packet #25: FooMTA: TCP Sequence 14915. Ack 305 It keeps going like this with my server still thinking it hasn’t received sequence 305… in response the remote side eventually retransmits its prior data thinking that it never arrived. Eventually the gap gets so large that no new data is sent and the remote MTA keeps retransmitting old stuff. This contributes to an exponential backoff and eventually the remote side gives up. What’s strange to me is that I see the “missing” TCP sequence (305 in this case) arriving back to my server (via a packet capture collected directly from fooMTA) So I don’t get why my server keeps asking for it. Could this be firewall related? What would be the next step in troubleshooting?

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