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  • how to deal with the position in a c# stream

    - by CapsicumDreams
    The (entire) documentation for the position property on a stream says: When overridden in a derived class, gets or sets the position within the current stream. The Position property does not keep track of the number of bytes from the stream that have been consumed, skipped, or both. That's it. OK, so we're fairly clear on what it doesn't tell us, but I'd really like to know what it in fact does stand for. What is 'the position' for? Why would we want to alter or read it? If we change it - what happens? In a pratical example, I have a a stream that periodically gets written to, and I have a thread that attempts to read from it (ideally ASAP). From reading many SO issues, I reset the position field to zero to start my reading. Once this is done: Does this affect where the writer to this stream is going to attempt to put the data? Do I need to keep track of the last write position myself? (ie if I set the position to zero to read, does the writer begin to overwrite everything from the first byte?) If so, do I need a semaphore/lock around this 'position' field (subclassing, perhaps?) due to my two threads accessing it? If I don't handle this property, does the writer just overflow the buffer? Perhaps I don't understand the Stream itself - I'm regarding it as a FIFO pipe: shove data in at one end, and suck it out at the other. If it's not like this, then do I have to keep copying the data past my last read (ie from position 0x84 on) back to the start of my buffer? I've seriously tried to research all of this for quite some time - but I'm new to .NET. Perhaps the Streams have a long, proud (undocumented) history that everyone else implicitly understands. But for a newcomer, it's like reading the manual to your car, and finding out: The accelerator pedal affects the volume of fuel and air sent to the fuel injectors. It does not affect the volume of the entertainment system, or the air pressure in any of the tires, if fitted. Technically true, but seriously, what we want to know is that if we mash it to the floor you go faster..

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  • Combining FileStream and MemoryStream to avoid disk accesses/paging while receiving gigabytes of data?

    - by w128
    I'm receiving a file as a stream of byte[] data packets (total size isn't known in advance) that I need to store somewhere before processing it immediately after it's been received (I can't do the processing on the fly). Total received file size can vary from as small as 10 KB to over 4 GB. One option for storing the received data is to use a MemoryStream, i.e. a sequence of MemoryStream.Write(bufferReceived, 0, count) calls to store the received packets. This is very simple, but obviously will result in out of memory exception for large files. An alternative option is to use a FileStream, i.e. FileStream.Write(bufferReceived, 0, count). This way, no out of memory exceptions will occur, but what I'm unsure about is bad performance due to disk writes (which I don't want to occur as long as plenty of memory is still available) - I'd like to avoid disk access as much as possible, but I don't know of a way to control this. I did some testing and most of the time, there seems to be little performance difference between say 10 000 consecutive calls of MemoryStream.Write() vs FileStream.Write(), but a lot seems to depend on buffer size and the total amount of data in question (i.e the number of writes). Obviously, MemoryStream size reallocation is also a factor. Does it make sense to use a combination of MemoryStream and FileStream, i.e. write to memory stream by default, but once the total amount of data received is over e.g. 500 MB, write it to FileStream; then, read in chunks from both streams for processing the received data (first process 500 MB from the MemoryStream, dispose it, then read from FileStream)? Another solution is to use a custom memory stream implementation that doesn't require continuous address space for internal array allocation (i.e. a linked list of memory streams); this way, at least on 64-bit environments, out of memory exceptions should no longer be an issue. Con: extra work, more room for mistakes. So how do FileStream vs MemoryStream read/writes behave in terms of disk access and memory caching, i.e. data size/performance balance. I would expect that as long as enough RAM is available, FileStream would internally read/write from memory (cache) anyway, and virtual memory would take care of the rest. But I don't know how often FileStream will explicitly access a disk when being written to. Any help would be appreciated.

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  • how can i get the file permission of a directory with java

    - by user571652
    i try to check the permission granted to a directory in linux, i mean i have a directory with permission 755 berty@berty-laptop:~$ ls -l / |grep directory drwxr-xr-x 3 root root 4096 2011-01-10 12:33 directory how can i read that permission with java? I've tried using FilePermission but though i have a directory with all the permissions (777) the FilePermission class always returns an exception java.security.AccessControlException: Access denied (java.io.FilePermission /home/directory read) at java.security.AccessController.checkPermission(AccessController.java:103) at com.snippets.Check4DirectoryPermission.checker(Check4DirectoryPermission.java:50) at com.snippets.Check4DirectoryPermission.main(Check4DirectoryPermission.java:70) is there another way to do this?

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  • How many colunms in table to keep? - MySQL

    - by Dennis
    I am stuck between row vs colunms table design for storing some items but the decision is which table is easier to manage and if colunms then how many colunms are best to have? For example I have object meta data, ideally there are 45 pieces of information (after being normalized) on the same level that i need to store per object. So is 45 colunms in a heavry read/write table good? Can it work flawless in a real world situation of heavy concurrent read/writes?

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  • How to convince someone, that reading books(blogs, so..) is important?

    - by hgulyan
    Dear all, please, help me to convince, that no matter what you're doing, you need to read some stuff, try to learn something new. They say, that they don't want to sit in front of computer in the end of a day and they don't have opportunity to read in working hours, or they're too tired for doing something. Have you faced this kind of situation? What did you do?

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  • Extracting contents of ConnectionStrings in web.config in Silverlight Business application.

    - by webKite
    I am trying to read dataSource ad Catalog from connectionString in web.config in Silverlight business project. Unfortunately when I used "SqlConnectionStringBuilder", I could not read connectionstring the has "connectionString="metadata=res:///MainDatabase.Main.csdl|res:///MainDatabase.Main.ssdl|......."" where as it work for "connectionString="Data Source=My-PC\SQL_2008;Initial Catalog =...."". I could get them using "Split" however, I don't like that solution. Is there any way to get my requirements? Thanks

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  • How do I detect server status in a port scanner java implementation

    - by akz
    I am writing a port scanner in Java and I want to be able to distinct the following 4 use cases: port is open port is open and server banner was read port is closed server is not live I have the following code: InetAddress address = InetAddress.getByName("google.com"); int[] ports = new int[]{21, 22, 23, 80, 443}; for (int i = 0; i < ports.length; i++) { int port = ports[i]; Socket socket = null; try { socket = new Socket(address, port); socket.setSoTimeout(500); System.out.println("port " + port + " open"); BufferedReader reader = new BufferedReader( new InputStreamReader(socket.getInputStream())); String line = reader.readLine(); if (line != null) { System.out.println(line); } socket.close(); } catch (SocketTimeoutException ex) { // port was open but nothing was read from input stream ex.printStackTrace(); } catch (ConnectException ex) { // port is closed ex.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null && !socket.isClosed()) { try { socket.close(); } catch (Exception e) { e.printStackTrace(); } } } } The problem is that I get a ConnectionException both when the port is closed and the server cannot be reached but with a different exception message: java.net.ConnectException: Connection timed out: connect when the connection was never established and java.net.ConnectException: Connection refused: connect when the port was closed so I cannot make the distinction between the two use cases without digging into the actual exception message. Same thing happens when I try a different approach for the socket creation. If I use: socket = new Socket(); socket.setSoTimeout(500); socket.connect(new InetSocketAddress(address, port), 1000); I have the same problem but with the SocketTimeoutException instead. I get a java.net.SocketTimeoutException: Read timed out if port was open but there was no banner to be read and java.net.SocketTimeoutException: connect timed out if server is not live or port is closed. Any ideas? Thanks in advance!

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  • problem with reading arabic in jsp page?

    - by sword101
    Hey there i have a column in the databsePostgreSQL which contains arabic data when reading the data from the database in the controller it's read fine, encoding is good but when sending the data to the jsp page and trying to read it it appears something like ????????? any ideas why something like this occur?

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  • Boost BGL thread safety

    - by Budzoli
    Hi! I'd like multiple threads to use the dijkstra_shortest_paths and astar_search functions of the BGL, and then read the property maps of the result vertices and edges. I'm wondering wether I should use mutexes to ensure thread-safety. So here are my questions: 1., Are the dijkstra_shortest_paths and astar_search functions of the Boost.Graph thread safe? 2., If I only try to read the property maps of the graph from multiple threads, do I need to worry about thread safety?

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  • reading a text file in java

    - by aks
    I want to read a text file containing a space sepearted vlaues.Values are integers. How can i read it and put it in a array list?? eg of contents of texx file 1 62 4 55 5 6 77 now i want a arraylist as [1, 62,4,55,5,6,77]. How do i do it in java?

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  • warcraft3 packet infromation [closed]

    - by ajay009ajay
    Hello All, I have made a program which is fetching data from server to and game to server. I want to keep these record in my file. But my problem is this is not in good format that i can read easily. I am reading all data as "Byte" (from java). Can anybody explain header or data info of packet. so I can read it in human manner Huh thanks.

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  • Alt for images in JasperReports

    - by Aviator
    Hello all, While putting an image element in PDF report, how can we give the alt description or similar kind of description for that image? The idea is to read the description when some screen reader is used to read the PDF. Currently, the reader (JAWS) says just 'graphic' when encountering an image in the PDF. Thanks!

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  • Erlang Types Specifications

    - by Chang
    I recently read the source code of couch-db, I find this type definition which i don't understand: -type branch() :: {Key::term(), Value::term(), Tree::term()}. -type path() :: {Start::pos_integer(), branch()}. -type tree() :: [branch()]. I did read Erlang doc, But what is the meaning of Start, Key, Value and Tree? From what i understand, they are Erlang variables! I didn't find any information about this in Erlang doc.

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  • Encrypt file using M2Crypto

    - by Bear
    It is known that I can read the whole file content in memory and encrypt it using the following code. contents = fin.read() cipher = M2Crypto.EVP.Cipher(alg="aes_128_cbc", key = aes_key, iv = aes_iv, op = 1) encryptedContents = cipher.update(contents) encryptedContents += cipher.final() But what if the file size is large, is there a way for me to pass the input stream to M2Crypto instead of reading the whole file first?

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  • access DLLs with java script

    - by Caio Garcia
    I need to read the serial port as an input for a web based applicaton. I know that the browser can't do it, but if I build an DLL and send it to my client, can I access this DLL and read de serial port with an java script or i will need something like ActiveX?

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  • Call panel.invalidate outside form class in C#

    - by Shaza
    Hey, I need to call "panel.invalidate" outside my form (WINform) class also I need to change some other controls as well, I read similar question here, and tried what they said, but it didn't work and I wasn't convinced at all. The answer I read was about exposing a public method like this: public void EnableButton(bool enable) { this.myButton.Enabled = enable; } Also I made a static instance in the other file static Form1 myForm = new Form1(); Any useful suggestions??

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  • How do find line in a List

    - by Shonna
    I have a text file. I read each line with sr.readline(); as i read that line, i want to search for it in a List that it should have been added to previously, then add it to a NEW list. How do i do this?

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  • Skipping a line and reading another line in shell script while loop

    - by parameswar
    i have a code which reads a file line by line using a while loop. Inside the while loop, i have certain conditions. Is there a way using which i can skip the current line and read the next line based upon the condition ? Let me be precise: while read Line do //some sample conditions a=$Line if [ "a" == "b" ] //i want to go to the next line from this point. done < **inputfile** Any help would be appreciated.

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  • Accessing Identity.AuthenticationType

    - by Tewr
    While implementing a custom authentication type in a wcf service, I'm trying to read the property IIdentity.AuthenticationType using the call Thread.CurrentPrincipal.Identity.AuthenticationType. Unless the account running the service is local administrator, UnauthorizedAccessException is thrown when accessing this property, much like described in this support thread. I can however reset the Thread.CurrentPrincipalobject without hassle, thus altering the Authentication Type - But read it, I cannot. Is running as an administrator the only way here or is there some trick to let the user running the service "just" access this property?

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  • hibernate annotation- extending base class - values are not being set - strange error

    - by gt_ebuddy
    I was following Hibernate: Use a Base Class to Map Common Fields and openjpa inheritance tutorial to put common columns like ID, lastModifiedDate etc in base table. My annotated mappings are as follow : BaseTable : @MappedSuperclass public abstract class BaseTable { @Id @GeneratedValue @Column(name = "id") private int id; @Column(name = "lastmodifieddate") private Date lastModifiedDate; ... Person table - @Entity @Table(name = "Person ") public class Person extends BaseTable implements Serializable{ ... Create statement generated : create table Person (id integer not null auto_increment, lastmodifieddate datetime, name varchar(255), primary key (id)) ; After I save a Person object to db, Person p = new Person(); p.setName("Test"); p.setLastModifiedDate(new Date()); .. getSession().save(p); I am setting the date field but, it is saving the record with generated ID and LastModifiedDate = null, and Name="Test". Insert Statement : insert into Person (lastmodifieddate, name) values (?, ?) binding parameter [1] as [TIMESTAMP] - <null> binding parameter [2] as [VARCHAR] - Test Read by ID query : When I do hibernate query (get By ID) as below, It reads person by given ID. Criteria c = getSession().createCriteria(Person.class); c.add(Restrictions.eq("id", id)); Person person= c.list().get(0); //person has generated ID, LastModifiedDate is null select query select person0_.id as id8_, person0_.lastmodifieddate as lastmodi8_, person0_.name as person8_ from Person person0_ - Found [1] as column [id8_] - Found [null] as column [lastmodi8_] - Found [Test] as column [person8_] ReadAll query : //read all Query query = getSession().createQuery("from " + Person.class.getName()); List allPersons=query.list(); Corresponding SQL for read all select query select person0_.id as id8_, person0_.lastmodifieddate as lastmodi8_, person0_.name as person8_ from Person person0_ - Found [1] as column [id8_] - Found [null] as column [lastmodi8_] - Found [Test] as column [person8_] - Found [2] as column [id8_] - Found [null] as column [lastmodi8_] - Found [Test2] as column [person8_] But when I print out the list in console, its being more weird. it is selecting List of Person object with ID fields = all 0 (why all 0 ?) LastModifiedDate = null Name fields have valid values I don't know whats wrong here. Could you please look at it? FYI, My Hibernate-core version : 4.1.2, MySQL Connector version : 5.1.9 . In summary, There are two issues here Why I am getting All ID Fields =0 when using read all? Why the LastModifiedDate is not being inserted?

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  • Easiest way to store long term variables with AS3

    - by deeb
    What's the easiest way to store a simple numeric variable on my server and then have a Flash application also hosted on the server read/write the variable? I've seen various xml solutions, but they look too complex for such a simple job. Is there a way to just read/write a simple text file with just AS3 and no middle-ware?

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