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  • add objects with different name through for loop

    - by Gandalf StormCrow
    What is the best way to do the following: List<MyObject> list = new LinkedList<MyObject>(); for(int i=0; i<30;i++) { MyObject o1 = new MyObject(); list.add(o1); } But the things is I don't wanna create objects with same name, I wanna create them with different name like o1,o2,o3,o4,o5,o6,o7,o8,o9,o10 and I wanna add each to the list. What is the best way to do this ?

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  • Vserver: secure mails from a hacked webservice

    - by lukas
    I plan to rent and setup a vServer with Debian xor CentOS. I know from my host, that the vServers are virtualized with linux-vserver. Assume there is a lighthttpd and some mail transfer agent running and we have to assure that if the lighthttpd will be hacked, the stored e-mails are not readable easily. For me, this sounds impossible but may I missed something or at least you guys can validate the impossibility... :) I think basically there are three obvious approaches. The first is to encrypt all the data. Nevertheless, the server would have to store the key somewhere so an attacker (w|c)ould figure that out. Secondly one could isolate the critical services like lighthttpd. Since I am not allowed to do 'mknod' or remount /dev in a linux-vserver, it is not possible to setup a nested vServer with lxc or similar techniques. The last approach would be to do a chroot but I am not sure if it would provide enough security. Further I have not tried yet, if I am able to do a chroot in a linux-vserver...? Thanks in advance!

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  • Bad performance with Linux software RAID5 and LUKS encryption

    - by Philipp Wendler
    I have set up a Linux software RAID5 on three hard drives and want to encrypt it with cryptsetup/LUKS. My tests showed that the encryption leads to a massive performance decrease that I cannot explain. The RAID5 is able to write 187 MB/s [1] without encryption. With encryption on top of it, write speed is down to about 40 MB/s. The RAID has a chunk size of 512K and a write intent bitmap. I used -c aes-xts-plain -s 512 --align-payload=2048 as the parameters for cryptsetup luksFormat, so the payload should be aligned to 2048 blocks of 512 bytes (i.e., 1MB). cryptsetup luksDump shows a payload offset of 4096. So I think the alignment is correct and fits to the RAID chunk size. The CPU is not the bottleneck, as it has hardware support for AES (aesni_intel). If I write on another drive (an SSD with LVM) that is also encrypted, I do have a write speed of 150 MB/s. top shows that the CPU usage is indeed very low, only the RAID5 xor takes 14%. I also tried putting a filesystem (ext4) directly on the unencrypted RAID so see if the layering is problem. The filesystem decreases the performance a little bit as expected, but by far not that much (write speed varying, but 100 MB/s). Summary: Disks + RAID5: good Disks + RAID5 + ext4: good Disks + RAID5 + encryption: bad SSD + encryption + LVM + ext4: good The read performance is not affected by the encryption, it is 207 MB/s without and 205 MB/s with encryption (also showing that CPU power is not the problem). What can I do to improve the write performance of the encrypted RAID? [1] All speed measurements were done with several runs of dd if=/dev/zero of=DEV bs=100M count=100 (i.e., writing 10G in blocks of 100M). Edit: If this helps: I'm using Ubuntu 11.04 64bit with Linux 2.6.38. Edit2: The performance stays approximately the same if I pass a block size of 4KB, 1MB or 10MB to dd.

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  • Probelm with String.split() in java

    - by Matt
    What I am trying to do is read a .java file, and pick out all of the identifiers and store them in a list. My problem is with the .split() method. If you run this code the way it is, you will get ArrayOutOfBounds, but if you change the delimiter from "." to anything else, the code works. But I need to lines parsed by "." so is there another way I could accomplish this? import java.io.BufferedReader; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.IOException; import java.util.*; public class MyHash { private static String[] reserved = new String[100]; private static List list = new LinkedList(); private static List list2 = new LinkedList(); public static void main (String args[]){ Hashtable hashtable = new Hashtable(997); makeReserved(); readFile(); String line; ListIterator itr = list.listIterator(); int listIndex = 0; while (listIndex < list.size()) { if (itr.hasNext()){ line = itr.next().toString(); //PROBLEM IS HERE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! String[] words = line.split("."); //CHANGE THIS AND IT WILL WORK System.out.println(words[0]); //TESTING TO SEE IF IT WORKED } listIndex++; } } public static void readFile() { String text; String[] words; BufferedReader in = null; try { in = new BufferedReader(new FileReader("MyHash.java")); //NAME OF INPUT FILE } catch (FileNotFoundException ex) { Logger.getLogger(MyHash.class.getName()).log(Level.SEVERE, null, ex); } try { while ((text = in.readLine()) != null){ text = text.trim(); words = text.split("\\s+"); for (int i = 0; i < words.length; i++){ list.add(words[i]); } for (int j = 0; j < reserved.length; j++){ if (list.contains(reserved[j])){ list.remove(reserved[j]); } } } } catch (IOException ex) { Logger.getLogger(MyHash.class.getName()).log(Level.SEVERE, null, ex); } try { in.close(); } catch (IOException ex) { Logger.getLogger(MyHash.class.getName()).log(Level.SEVERE, null, ex); } } public static int keyIt (int x) { int key = x % 997; return key; } public static int horner (String word){ int length = word.length(); char[] letters = new char[length]; for (int i = 0; i < length; i++){ letters[i]=word.charAt(i); } char[] alphabet = new char[26]; String abc = "abcdefghijklmnopqrstuvwxyz"; for (int i = 0; i < 26; i++){ alphabet[i]=abc.charAt(i); } int[] numbers = new int[length]; int place = 0; for (int i = 0; i < length; i++){ for (int j = 0; j < 26; j++){ if (alphabet[j]==letters[i]){ numbers[place]=j+1; place++; } } } int hornered = numbers[0] * 32; for (int i = 1; i < numbers.length; i++){ hornered += numbers[i]; if (i == numbers.length -1){ return hornered; } hornered = hornered % 997; hornered *= 32; } return hornered; } public static String[] makeReserved (){ reserved[0] = "abstract"; reserved[1] = "assert"; reserved[2] = "boolean"; reserved[3] = "break"; reserved[4] = "byte"; reserved[5] = "case"; reserved[6] = "catch"; reserved[7] = "char"; reserved[8] = "class"; reserved[9] = "const"; reserved[10] = "continue"; reserved[11] = "default"; reserved[12] = "do"; reserved[13] = "double"; reserved[14] = "else"; reserved[15] = "enum"; reserved[16] = "extends"; reserved[17] = "false"; reserved[18] = "final"; reserved[19] = "finally"; reserved[20] = "float"; reserved[21] = "for"; reserved[22] = "goto"; reserved[23] = "if"; reserved[24] = "implements"; reserved[25] = "import"; reserved[26] = "instanceof"; reserved[27] = "int"; reserved[28] = "interface"; reserved[29] = "long"; reserved[30] = "native"; reserved[31] = "new"; reserved[32] = "null"; reserved[33] = "package"; reserved[34] = "private"; reserved[35] = "protected"; reserved[36] = "public"; reserved[37] = "return"; reserved[38] = "short"; reserved[39] = "static"; reserved[40] = "strictfp"; reserved[41] = "super"; reserved[42] = "switch"; reserved[43] = "synchronize"; reserved[44] = "this"; reserved[45] = "throw"; reserved[46] = "throws"; reserved[47] = "trasient"; reserved[48] = "true"; reserved[49] = "try"; reserved[50] = "void"; reserved[51] = "volatile"; reserved[52] = "while"; reserved[53] = "="; reserved[54] = "=="; reserved[55] = "!="; reserved[56] = "+"; reserved[57] = "-"; reserved[58] = "*"; reserved[59] = "/"; reserved[60] = "{"; reserved[61] = "}"; return reserved; } }

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  • Networking- Wireless and Wired not working

    - by JJ White
    So everything in Ubuntu has been working great until networking stopped working. I've spent the better part of two days scouring for a fix with no luck. Here is my info...your help would so be appreciated. grep -i eth /var/log/syslog | tail Sep 25 16:31:59 jj-laptop NetworkManager[970]: <info> (eth0): cleaning up... Sep 25 16:31:59 jj-laptop NetworkManager[970]: <info> (eth0): taking down device. Sep 25 16:31:59 jj-laptop kernel: [23403.998837] sky2 0000:02:00.0: eth0: disabling interface Sep 25 16:35:54 jj-laptop NetworkManager[970]: <info> (eth0): now managed Sep 25 16:35:54 jj-laptop NetworkManager[970]: <info> (eth0): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2] Sep 25 16:35:54 jj-laptop NetworkManager[970]: <info> (eth0): bringing up device. Sep 25 16:35:54 jj-laptop kernel: [23413.629424] sky2 0000:02:00.0: eth0: enabling interface Sep 25 16:35:54 jj-laptop kernel: [23413.635703] ADDRCONF(NETDEV_UP): eth0: link is not ready Sep 25 16:35:54 jj-laptop NetworkManager[970]: <info> (eth0): preparing device. Sep 25 16:35:54 jj-laptop NetworkManager[970]: <info> (eth0): deactivating device (reason 'managed') [2] and then ifconfig -a eth0 Link encap:Ethernet HWaddr 00:17:42:14:e9:e1 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:4605 errors:0 dropped:0 overruns:0 frame:0 TX packets:287 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:315161 (315.1 KB) TX bytes:63680 (63.6 KB) Interrupt:16 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:13018 errors:0 dropped:0 overruns:0 frame:0 TX packets:13018 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:880484 (880.4 KB) TX bytes:880484 (880.4 KB) wlan0 Link encap:Ethernet HWaddr 00:13:02:d0:ee:13 BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) also iwconfig lo no wireless extensions. wlan0 IEEE 802.11abg ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=off Retry long limit:7 RTS thr:off Fragment thr:off Power Management:on eth0 no wireless extensions. and of course sudo lshw -C network *-network description: Ethernet interface product: 88E8055 PCI-E Gigabit Ethernet Controller vendor: Marvell Technology Group Ltd. physical id: 0 bus info: pci@0000:02:00.0 logical name: eth0 version: 12 serial: 00:17:42:14:e9:e1 size: 1Gbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm vpd msi pciexpress bus_master cap_list rom ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=sky2 driverversion=1.30 duplex=full firmware=N/A latency=0 link=no multicast=yes port=twisted pair speed=1Gbit/s resources: irq:44 memory:f0000000-f0003fff ioport:2000(size=256) memory:c0a00000-c0a1ffff *-network DISABLED description: Wireless interface product: PRO/Wireless 3945ABG [Golan] Network Connection vendor: Intel Corporation physical id: 0 bus info: pci@0000:05:00.0 logical name: wlan0 version: 02 serial: 00:13:02:d0:ee:13 width: 32 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=iwl3945 driverversion=3.2.0-31-generic firmware=15.32.2.9 latency=0 link=no multicast=yes wireless=IEEE 802.11abg resources: irq:45 memory:c0100000-c0100fff last but not least lsmod Module Size Used by nls_iso8859_1 12617 0 nls_cp437 12751 0 vfat 17308 0 fat 55605 1 vfat usb_storage 39646 0 uas 17828 0 dm_crypt 22528 0 rfcomm 38139 0 parport_pc 32114 0 bnep 17830 2 ppdev 12849 0 bluetooth 158438 10 rfcomm,bnep binfmt_misc 17292 1 snd_hda_codec_idt 60251 1 pcmcia 39791 0 joydev 17393 0 snd_hda_intel 32765 3 snd_hda_codec 109562 2 snd_hda_codec_idt,snd_hda_intel snd_hwdep 13276 1 snd_hda_codec snd_pcm 80845 2 snd_hda_intel,snd_hda_codec snd_seq_midi 13132 0 yenta_socket 27428 0 snd_rawmidi 25424 1 snd_seq_midi snd_seq_midi_event 14475 1 snd_seq_midi snd_seq 51567 2 snd_seq_midi,snd_seq_midi_event pcmcia_rsrc 18367 1 yenta_socket wacom_w8001 12906 0 irda 185517 0 arc4 12473 2 iwl3945 73111 0 iwl_legacy 71134 1 iwl3945 mac80211 436455 2 iwl3945,iwl_legacy cfg80211 178679 3 iwl3945,iwl_legacy,mac80211 snd_timer 28931 2 snd_pcm,snd_seq snd_seq_device 14172 3 snd_seq_midi,snd_rawmidi,snd_seq dm_multipath 22710 0 pcmcia_core 21511 3 pcmcia,yenta_socket,pcmcia_rsrc psmouse 96619 0 apanel 12718 0 serport 12808 1 serio_raw 13027 0 crc_ccitt 12595 1 irda mac_hid 13077 0 snd 62064 15 snd_hda_codec_idt,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_t imer,snd_seq_device input_polldev 13648 1 apanel soundcore 14635 1 snd snd_page_alloc 14115 2 snd_hda_intel,snd_pcm lp 17455 0 fujitsu_laptop 18504 0 parport 40930 3 parport_pc,ppdev,lp dm_raid45 76451 0 xor 25987 1 dm_raid45 dm_mirror 21822 0 dm_region_hash 16065 1 dm_mirror dm_log 18193 3 dm_raid45,dm_mirror,dm_region_hash sdhci_pci 18324 0 sdhci 28241 1 sdhci_pci sky2 49545 0 i915 414939 3 drm_kms_helper 45466 1 i915 drm 197692 4 i915,drm_kms_helper i2c_algo_bit 13199 1 i915 video 19068 1 i915

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  • Problem with boundary collision

    - by James Century
    The problem: When the player hits the left boundary he stops (this is exactly what I want), when he hits the right boundary. He continues until his rectangle's left boundary meets with the right boundary. Outcome: https://www.youtube.com/watch?v=yuJfIWZ_LL0&feature=youtu.be My Code public class Player extends GameObject{ BufferedImageLoader loader; Texture tex = Game.getInstance(); BufferedImage image; Animation playerWalkLeft; private HealthBarManager healthBar; private String username; private int width; private ManaBarManager manaBar; public Player(float x, float y, ObjectID ID) { super(x, y, ID, null); loader = new BufferedImageLoader(); playerWalkLeft = new Animation(5,tex.player[10],tex.player[11],tex.player[12],tex.player[13],tex.player[14],tex.player[15],tex.player[17],tex.player[18]); } public void tick(LinkedList<GameObject> object) { setX(getX()+velX); setY(getY()+velY); playerWalkLeft.runAnimation(); } public void render(Graphics g) { g.setColor(Color.BLACK); FontMetrics fm = g.getFontMetrics(g.getFont()); if(username != null) width = fm.stringWidth(username); if(username != null){ g.drawString(username,(int) x-width/2+15,(int) y); } if(velX != 0){ playerWalkLeft.drawAnimation(g, (int)x, (int)y); }else{ g.drawImage(tex.player[16], (int)x, (int)y, null); } g.setColor(Color.PINK); g.drawRect((int)x,(int)y,33,48); g.drawRect(0,0,(int)Game.getWalkableBounds().getWidth(), (int)Game.getWalkableBounds().getHeight()); } @SuppressWarnings("unused") private Image getCurrentImage() { return image; } public float getX() { return x; } public float getY() { return y; } public void setX(float x) { Rectangle gameBoundry = Game.getWalkableBounds(); if(x >= gameBoundry.getMinX() && x <= gameBoundry.getMaxX()){ this.x = x; } } public void setY(float y) { //IGNORE THE SetY please. this.y = y; } public float getVelX() { return velX; } public void setHealthBar(HealthBarManager healthBar){ this.healthBar = healthBar; } public HealthBarManager getHealthBar(){ return healthBar; } public float getVelY() { return velY; } public void setVelX(float velX) { this.velX = velX; } public void setVelY(float velY) { this.velY = velY; } public ObjectID getID() { return ID; } public void setUsername(String playerName) { this.username = playerName; } public String getUsername(){ return this.username; } public void setManaBar(ManaBarManager manaBar) { this.manaBar = manaBar; } public ManaBarManager getManaBar(){ return manaBar; } public int getLevel(){ return 1; } public boolean isPlayerInsideBoundry(float x, float y){ Rectangle boundry = Game.getWalkableBounds(); if(boundry.contains(x,y)){ return true; } return false; } } What I've tried: - Using a method that checks if the game boundary contains player boundary rectangle. This gave me the same result as what the check statement in my setX did.

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  • Generic Adjacency List Graph implementation

    - by DmainEvent
    I am trying to come up with a decent Adjacency List graph implementation so I can start tooling around with all kinds of graph problems and algorithms like traveling salesman and other problems... But I can't seem to come up with a decent implementation. This is probably because I am trying to dust the cobwebs off my data structures class. But what I have so far... and this is implemented in Java... is basically an edgeNode class that has a generic type and a weight-in the event the graph is indeed weighted. public class edgeNode<E> { private E y; private int weight; //... getters and setters as well as constructors... } I have a graph class that has a list of edges a value for the number of Vertices and and an int value for edges as well as a boolean value for whether or not it is directed. The brings up my first question, if the graph is indeed directed, shouldn't I have a value in my edgeNode class? Or would I just need to add another vertices to my LinkedList? That would imply that a directed graph is 2X as big as an undirected graph wouldn't it? public class graph { private List<edgeNode<?>> edges; private int nVertices; private int nEdges; private boolean directed; //... getters and setters as well as constructors... } Finally does anybody have a standard way of initializing there graph? I was thinking of reading in a pipe-delimited file but that is so 1997. public graph GenereateGraph(boolean directed, String file){ List<edgeNode<?>> edges; graph g; try{ int count = 0; String line; FileReader input = new FileReader("C:\\Users\\derekww\\Documents\\JavaEE Projects\\graphFile"); BufferedReader bufRead = new BufferedReader(input); line = bufRead.readLine(); count++; edges = new ArrayList<edgeNode<?>>(); while(line != null){ line = bufRead.readLine(); Object edgeInfo = line.split("|")[0]; int weight = Integer.parseInt(line.split("|")[1]); edgeNode<String> e = new edgeNode<String>((String) edges.add(e); } return g; } catch(Exception e){ return null; } } I guess when I am adding edges if boolean is true I would be adding a second edge. So far, this all depends on the file I write. So if I wrote a file with the following Vertices and weights... Buffalo | 18 br Pittsburgh | 20 br New York | 15 br D.C | 45 br I would obviously load them into my list of edges, but how can I represent one vertices connected to the other... so on... I would need the opposite vertices? Say I was representing Highways connected to each city weighted and un-directed (each edge is bi-directional with weights in some fictional distance unit)... Would my implementation be the best way to do that? I found this tutorial online Graph Tutorial that has a connector object. This appears to me be a collection of vertices pointing to each other. So you would have A and B each with there weights and so on, and you would add this to a list and this list of connectors to your graph... That strikes me as somewhat cumbersome and a little dismissive of the adjacency list concept? Am I wrong and that is a novel solution? This is all inspired by steve skiena's Algorithm Design Manual. Which I have to say is pretty good so far. Thanks for any help you can provide.

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  • determine parity of a bit representation of a number in MIPS

    - by Hristo
    Is there some instruction in MIPS that will determine the parity of a certain bit representation? I know to determine whether a "number" has an even parity or an odd parity is to XOR the individual bits of the binary representation together, but that seems computationally-intensive for a set of MIPS instructions... and I need to do this as quick as possible. Also, the number I'm working in is represented in Grey Code... just to throw that in there. So is there some pseudo-instruction in MIPS to determine the parity of a "number" or do I have to do it by hand? If there is no MIPS instruction, which it seems very unlikely to be, any advice on how to do it by hand? Thanks, Hristo follow-up: I found a optimization, but my implementation isn't working. unsigned int v; // 32-bit word v ^= v >> 1; v ^= v >> 2; v = (v & 0x11111111U) * 0x11111111U; return (v >> 28) & 1;

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  • c++ generate a good random seed for psudo random number generators

    - by posop
    I am trying to generate a good random seed for a psudo-random number generator. I thought I'd get the expert's opinions. let me know if this is a bad way of doing it or if there are much better ways. #include <iostream> #include <cstdlib> #include <fstream> #include <ctime> unsigned int good_seed() { unsigned int random_seed, random_seed_a, random_seed_b; std::ifstream file ("/dev/random", std::ios::binary); if (file.is_open()) { char * memblock; int size = sizeof(int); memblock = new char [size]; file.read (memblock, size); file.close(); random_seed_a = int(memblock); delete[] memblock; }// end if else { random_seed_a = 0; } random_seed_b = std::time(0); random_seed = random_seed_a xor random_seed_b; return random_seed; } // end good_seed()

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  • Bitwise Interval Arithmetic

    - by KennyTM
    I've recently read an interesting thread on the D newsgroup, which basically asks, Given two signed integers a ∈ [amin, amax], b ∈ [bmin, bmax], what is the tightest interval of a | b? I'm think if interval arithmetics can be applied on general bitwise operators (assuming infinite bits). The bitwise-NOT and shifts are trivial since they just corresponds to -1 − x and 2n x. But bitwise-AND/OR are a lot trickier, due to the mix of bitwise and arithmetic properties. Is there a polynomial-time algorithm to compute the intervals of bitwise-AND/OR? Note: Assume all bitwise operations run in linear time (of number of bits), and test/set a bit is constant time. The brute-force algorithm runs in exponential time. Because ~(a | b) = ~a & ~b and a ^ b = (a | b) & ~(a & b), solving the bitwise-AND and -NOT problem implies bitwise-OR and -XOR are done. Although the content of that thread suggests min{a | b} = max(amin, bmin), it is not the tightest bound. Just consider [2, 3] | [8, 9] = [10, 11].)

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  • JAVA image transfer problem

    - by user579098
    Hi, I have a school assignment, to send a jpg image,split it into groups of 100 bytes, corrupt it, use a CRC check to locate the errors and re-transmit until it eventually is built back into its original form. It's practically ready, however when I check out the new images, they appear with errors.. I would really appreciate if someone could look at my code below and maybe locate this logical mistake as I can't understand what the problem is because everything looks ok :S For the file with all the data needed including photos and error patterns one could download it from this link:http://rapidshare.com/#!download|932tl2|443122762|Data.zip|739 Thanks in advance, Stefan p.s dont forget to change the paths in the code for the image and error files package networks; import java.io.*; // for file reader import java.util.zip.CRC32; // CRC32 IEEE (Ethernet) public class Main { /** * Reads a whole file into an array of bytes. * @param file The file in question. * @return Array of bytes containing file data. * @throws IOException Message contains why it failed. */ public static byte[] readFileArray(File file) throws IOException { InputStream is = new FileInputStream(file); byte[] data=new byte[(int)file.length()]; is.read(data); is.close(); return data; } /** * Writes (or overwrites if exists) a file with data from an array of bytes. * @param file The file in question. * @param data Array of bytes containing the new file data. * @throws IOException Message contains why it failed. */ public static void writeFileArray(File file, byte[] data) throws IOException { OutputStream os = new FileOutputStream(file,false); os.write(data); os.close(); } /** * Converts a long value to an array of bytes. * @param data The target variable. * @return Byte array conversion of data. * @see http://www.daniweb.com/code/snippet216874.html */ public static byte[] toByta(long data) { return new byte[] { (byte)((data >> 56) & 0xff), (byte)((data >> 48) & 0xff), (byte)((data >> 40) & 0xff), (byte)((data >> 32) & 0xff), (byte)((data >> 24) & 0xff), (byte)((data >> 16) & 0xff), (byte)((data >> 8) & 0xff), (byte)((data >> 0) & 0xff), }; } /** * Converts a an array of bytes to long value. * @param data The target variable. * @return Long value conversion of data. * @see http://www.daniweb.com/code/snippet216874.html */ public static long toLong(byte[] data) { if (data == null || data.length != 8) return 0x0; return (long)( // (Below) convert to longs before shift because digits // are lost with ints beyond the 32-bit limit (long)(0xff & data[0]) << 56 | (long)(0xff & data[1]) << 48 | (long)(0xff & data[2]) << 40 | (long)(0xff & data[3]) << 32 | (long)(0xff & data[4]) << 24 | (long)(0xff & data[5]) << 16 | (long)(0xff & data[6]) << 8 | (long)(0xff & data[7]) << 0 ); } public static byte[] nextNoise(){ byte[] result=new byte[100]; // copy a frame's worth of data (or remaining data if it is less than frame length) int read=Math.min(err_data.length-err_pstn, 100); System.arraycopy(err_data, err_pstn, result, 0, read); // if read data is less than frame length, reset position and add remaining data if(read<100){ err_pstn=100-read; System.arraycopy(err_data, 0, result, read, err_pstn); }else // otherwise, increase position err_pstn+=100; // return noise segment return result; } /** * Given some original data, it is purposefully corrupted according to a * second data array (which is read from a file). In pseudocode: * corrupt = original xor corruptor * @param data The original data. * @return The new (corrupted) data. */ public static byte[] corruptData(byte[] data){ // get the next noise sequence byte[] noise = nextNoise(); // finally, xor data with noise and return result for(int i=0; i<100; i++)data[i]^=noise[i]; return data; } /** * Given an array of data, a packet is created. In pseudocode: * frame = corrupt(data) + crc(data) * @param data The original frame data. * @return The resulting frame data. */ public static byte[] buildFrame(byte[] data){ // pack = [data]+crc32([data]) byte[] hash = new byte[8]; // calculate crc32 of data and copy it to byte array CRC32 crc = new CRC32(); crc.update(data); hash=toByta(crc.getValue()); // create a byte array holding the final packet byte[] pack = new byte[data.length+hash.length]; // create the corrupted data byte[] crpt = new byte[data.length]; crpt = corruptData(data); // copy corrupted data into pack System.arraycopy(crpt, 0, pack, 0, crpt.length); // copy hash into pack System.arraycopy(hash, 0, pack, data.length, hash.length); // return pack return pack; } /** * Verifies frame contents. * @param frame The frame data (data+crc32). * @return True if frame is valid, false otherwise. */ public static boolean verifyFrame(byte[] frame){ // allocate hash and data variables byte[] hash=new byte[8]; byte[] data=new byte[frame.length-hash.length]; // read frame into hash and data variables System.arraycopy(frame, frame.length-hash.length, hash, 0, hash.length); System.arraycopy(frame, 0, data, 0, frame.length-hash.length); // get crc32 of data CRC32 crc = new CRC32(); crc.update(data); // compare crc32 of data with crc32 of frame return crc.getValue()==toLong(hash); } /** * Transfers a file through a channel in frames and reconstructs it into a new file. * @param jpg_file File name of target file to transfer. * @param err_file The channel noise file used to simulate corruption. * @param out_file The name of the newly-created file. * @throws IOException */ public static void transferFile(String jpg_file, String err_file, String out_file) throws IOException { // read file data into global variables jpg_data = readFileArray(new File(jpg_file)); err_data = readFileArray(new File(err_file)); err_pstn = 0; // variable that will hold the final (transfered) data byte[] out_data = new byte[jpg_data.length]; // holds the current frame data byte[] frame_orig = new byte[100]; byte[] frame_sent = new byte[100]; // send file in chunks (frames) of 100 bytes for(int i=0; i<Math.ceil(jpg_data.length/100); i++){ // copy jpg data into frame and init first-time switch System.arraycopy(jpg_data, i*100, frame_orig, 0, 100); boolean not_first=false; System.out.print("Packet #"+i+": "); // repeat getting same frame until frame crc matches with frame content do { if(not_first)System.out.print("F"); frame_sent=buildFrame(frame_orig); not_first=true; }while(!verifyFrame(frame_sent)); // usually, you'd constrain this by time to prevent infinite loops (in // case the channel is so wacked up it doesn't get a single packet right) // copy frame to image file System.out.println("S"); System.arraycopy(frame_sent, 0, out_data, i*100, 100); } System.out.println("\nDone."); writeFileArray(new File(out_file),out_data); } // global variables for file data and pointer public static byte[] jpg_data; public static byte[] err_data; public static int err_pstn=0; public static void main(String[] args) throws IOException { // list of jpg files String[] jpg_file={ "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo1.jpg", "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo2.jpg", "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo3.jpg", "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo4.jpg" }; // list of error patterns String[] err_file={ "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 1.DAT", "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 2.DAT", "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 3.DAT", "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 4.DAT" }; // loop through all jpg/channel combinations and run tests for(int x=0; x<jpg_file.length; x++){ for(int y=0; y<err_file.length; y++){ System.out.println("Transfering photo"+(x+1)+".jpg using Pattern "+(y+1)+"..."); transferFile(jpg_file[x],err_file[y],jpg_file[x].replace("photo","CH#"+y+"_photo")); } } } }

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  • Far jump in ntdll.dll's internal ZwCreateUserProcess

    - by user49164
    I'm trying to understand how the Windows API creates processes so I can create a program to determine where invalid exes fail. I have a program that calls kernel32.CreateProcessA. Following along in OllyDbg, this calls kernel32.CreateProcessInternalA, which calls kernel32.CreateProcessInternalW, which calls ntdll.ZwCreateUserProcess. This function goes: mov eax, 0xAA xor ecx, ecx lea edx, dword ptr [esp+4] call dword ptr fs:[0xC0] add esp, 4 retn 0x2C So I follow the call to fs:[0xC0], which contains a single instruction: jmp far 0x33:0x74BE271E But when I step this instruction, Olly just comes back to ntdll.ZwCreateUserProcess at the add esp, 4 right after the call (which is not at 0x74BE271E). I put a breakpoint at retn 0x2C, and I find that the new process was somehow created during the execution of add esp, 4. So I'm assuming there's some magic involved in the far jump. I tried to change the CS register to 0x33 and EIP to 0x74BE271E instead of actually executing the far jump, but that just gave me an access violation after a few instructions. What's going on here? I need to be able to delve deeper beyond the abstraction of this ZwCreateUserProcess to figure out how exactly Windows creates processes.

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  • Generic Dictionary and generating a hashcode for multi-part key

    - by Andrew
    I have an object that has a multi-part key and I am struggling to find a suitable way override GetHashCode. An example of what the class looks like is. public class wibble{ public int keypart1 {get; set;} public int keypart2 {get; set;} public int keypart3 {get; set;} public int keypart4 {get; set;} public int keypart5 {get; set;} public int keypart6 {get; set;} public int keypart7 {get; set;} public single value {get; set;} } Note in just about every instance of the class no more than 2 or 3 of the keyparts would have a value greater than 0. Any ideas on how best to generate a unique hashcode in this situation? I have also been playing around with creating a key that is not unique, but spreads the objects evenly between the dictionaries buckets and then storing objects with matched hashes in a List< or LinkedList< or SortedList<. Any thoughts on this?

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  • Why collection literals ?

    - by Green Hyena
    Hi fellow Java programmers. From the various online articles on Java 7 I have come to know that Java 7 will be having collection literals like the following: List<String> fruits = [ "Apple", "Mango", "Guava" ]; Set<String> flowers = { "Rose", "Daisy", "Chrysanthemum" }; Map<Integer, String> hindiNums = { 1 : "Ek", 2 : "Do", 3 : "Teen" }; My questions are: 1] Wouldn't it have been possible to provide a static method of in all of the collection classes which could be used as follows: List<String> fruits = ArrayList.of("Apple", "Mango", "Guava"); IMO this looks as good as the literal version and is also reasonably concise. Why then did they have to invent a new syntax? 2] When I say List<String> fruits = [ "Apple", "Mango", "Guava" ]; what List would I actually get? Would it be ArrayList or LinkedList or something else? Thanks.

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  • What are the most interesting equivalences arising from the Curry-Howard Isomorphism?

    - by Tom
    I came upon the Curry-Howard Isomorphism relatively late in my programming life, and perhaps this contributes to my being utterly fascinated by it. It implies that for every programming concept there exists a precise analogue in formal logic, and vice versa. Here's an "obvious" list of such analogies, off the top of my head: program/definition | proof type/declaration | proposition inhabited type | theorem function | implication function argument | hypothesis/antecedent function result | conclusion/consequent function application | modus ponens recursion | induction identity function | tautology non-terminating function | absurdity tuple | conjunction (and) disjoint union | exclusive disjunction (xor) parametric polymorphism | universal quantification So, to my question: what are some of the more interesting/obscure implications of this isomorphism? I'm no logician so I'm sure I've only scratched the surface with this list. For example, here are some programming notions for which I'm unaware of pithy names in logic: currying | "((a & b) => c) iff (a => (b => c))" scope | "known theory + hypotheses" And here are some logical concepts which I haven't quite pinned down in programming terms: primitive type? | axiom set of valid programs? | theory ? | disjunction (or)

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  • SQL with Regular Expressions vs Indexes with Logical Merging Functions

    - by geeko
    Hello Lads, I am trying to develop a complex textual search engine. I have thousands of textual pages from many books. I need to search pages that contain specified complex logical criterias. These criterias can contain virtually any compination of the following: A: Full words. B: Word roots (semilar to stems; i.e. all words with certain key letters). C: Word templates (in some languages are filled in certain templates to form various part of speech such as adjactives, past/present verbs...). D: Logical connectives: AND/OR/XOR/NOT/IF/IFF and parentheses to state priorities. Now, would it be faster to have the pages' full text in database (not indexed) and search though them all using SQL and Regular Expressions ? Or would it be better to construct indexes of word/root/template-page-location tuples. Hence, we can boost searching for individual words/roots/templates. However, it gets tricky as we interdouce logical connectives into our query. I thought of doing the following steps in such cases: 1: Seperately search for each individual words/roots/templates in the specified query. 2: On priority bases, we merge two result lists (from step 1) at a time depedning on the logical connective For example, if we are searching for "he AND (is OR was)": 1: We shall search for "he", "is" and "was" seperately and get result lists for each word. 2: Merge the result lists of "is" and "was" using the merging function OR-MERGE 3: Merge the merged result list from the OR-MERGE function with the one of "he" using the merging function AND-MERGE The result of step 3 is then returned as the result of the specified query. What do you think gurues ? Which is faster ? Any better ideas ? Thank you all in advance.

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  • i386 assembly question: why do I need to meddle with the stack pointer?

    - by zneak
    Hello everyone, I decided it would be fun to learn x86 assembly during the summer break. So I started with a very simple hello world program, borrowing on free examples gcc -S could give me. I ended up with this: HELLO: .ascii "Hello, world!\12\0" .text .globl _main _main: pushl %ebp # 1. puts the base stack address on the stack movl %esp, %ebp # 2. puts the base stack address in the stack address register subl $20, %esp # 3. ??? pushl $HELLO # 4. push HELLO's address on the stack call _puts # 5. call puts xorl %eax, %eax # 6. zero %eax, probably not necessary since we didn't do anything with it leave # 7. clean up ret # 8. return # PROFIT! It compiles and even works! And I think I understand most of it. Though, magic happens at step 3. Would I remove this line, my program would die between the call to puts and the xor from a misaligned stack error. And would I change $20 to another value, it'd crash too. So I came to the conclusion that this value is very important. Problem is, I don't know what it does and why it's needed. Can anyone explain me? (I'm on Mac OS, would it ever matter.)

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  • How to create extensible dynamic array in Java without using pre-made classes?

    - by AndrejaKo
    Yeah, it's a homework question, so givemetehkodezplsthx! :) Anyway, here's what I need to do: I need to have a class which will have among its attributes array of objects of another class. The proper way to do this in my opinion would be to use something like LinkedList, Vector or similar. Unfortunately, last time I did that, I got fire and brimstone from my professor, because according to his belief I was using advanced stuff without understanding basics. Now next obvious solution would be to create array with fixed number of elements and add checks to get and set which will see if the array is full. If it is full, they'd create new bigger array, copy older array's data to the new array and return the new array to the caller. If it's mostly empty, they'd create new smaller array and move data from old array to new. To me this looks a bit stupid. For my homework, there probably won't be more that 3 elements in an array, but I'd like to make a scalable solution without manually calculating statistics about how often is array filled, what is the average number of new elements added, then using results of calculation to calculate number of elements in new array and so on. By the way, there is no need to remove elements from the middle of the array. Any tips?

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  • Compile Assembly Output generated by VC++?

    - by SDD
    I have a simple hello world C program and compile it with /FA. As a consequence, the compiler also generates the corresponding assembly listing. Now I want to use masm/link to assemble an executable from the generated .asm listing. The following command line yields 3 linker errors: \masm32\bin\ml /I"C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include" /c /coff asm_test.asm \masm32\bin\link /SUBSYSTEM:CONSOLE /LIBPATH:"C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\lib" asm_test.obj indicating that the C-runtime functions were not linked to the object files produced earlier: asm_test.obj : error LNK2001: unresolved external symbol @__security_check_cookie@4 asm_test.obj : error LNK2001: unresolved external symbol _printf LINK : error LNK2001: unresolved external symbol _wmainCRTStartup asm_test.exe : fatal error LNK1120: 3 unresolved externals Here is the generated assembly listing ; Listing generated by Microsoft (R) Optimizing Compiler Version 15.00.30729.01 TITLE c:\asm_test\asm_test\asm_test.cpp .686P .XMM include listing.inc .model flat INCLUDELIB OLDNAMES PUBLIC ??_C@_0O@OBPALAEI@hello?5world?$CB?6?$AA@ ; `string' EXTRN @__security_check_cookie@4:PROC EXTRN _printf:PROC ; COMDAT ??_C@_0O@OBPALAEI@hello?5world?$CB?6?$AA@ CONST SEGMENT ??_C@_0O@OBPALAEI@hello?5world?$CB?6?$AA@ DB 'hello world!', 0aH, 00H ; `string' CONST ENDS PUBLIC _wmain ; Function compile flags: /Ogtpy ; COMDAT _wmain _TEXT SEGMENT _argc$ = 8 ; size = 4 _argv$ = 12 ; size = 4 _wmain PROC ; COMDAT ; File c:\users\octon\desktop\asm_test\asm_test\asm_test.cpp ; Line 21 push OFFSET ??_C@_0O@OBPALAEI@hello?5world?$CB?6?$AA@ call _printf add esp, 4 ; Line 22 xor eax, eax ; Line 23 ret 0 _wmain ENDP _TEXT ENDS END I am using the latest masm32 version (6.14.8444).

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  • Find the Algorithm that generates the checksum

    - by knivmannen
    I have a sensing device that transmits a 6-byte message along with an 1-byte counter and supposely a checksum. The data looks something like this: ------DATA----------- -Counter- --Checksum?-- 55 FF 00 00 EC FF ---- 60---------- 1F The last four bits in the counter are always set 0, i.e those bits are probably not used. The last byte is assumed to be the checksum since it has a quite peculiar nature. It tends to randomly change as data changes. Now what i need is to find the algorithm to compute this checksum based on --DATA--. what i have tried is all possible CRC-8 polynomials, for each polynomial i have tried to reflect data, toggle it, initiate it with non-zeroes etc etc. Ive come to the conclusion that i am not dealing with a normal crc-algorithm. I have also tried some flether and adler methods without succes, xor stuff back and forth but still i have no clue how to generate the checksum. My biggest concern is, how is the counter used??? Same data but with different countervalue generates different checksums. I have tried to include the counter in my computations but without any luck. Here are some other datasamples: 55 FF 00 00 F0 FF A0 38 66 0B EA FF BF FF C0 CA 5E 18 EA FF B7 FF 60 BD F6 30 16 00 FC FE 10 81 One more thing that might be worth mentioning is that the last byte in the data only takes on the values FF or FE Plz if u have any tips or tricks that i may try post them here, I am truly desperate. Thx

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  • Scala type inference failure on "? extends" in Java code

    - by oxbow_lakes
    I have the following simple Java code: package testj; import java.util.*; public class Query<T> { private static List<Object> l = Arrays.<Object>asList(1, "Hello", 3.0); private final Class<? extends T> clazz; public static Query<Object> newQuery() { return new Query<Object>(Object.class); } public Query(Class<? extends T> clazz) { this.clazz = clazz; } public <S extends T> Query<S> refine(Class<? extends S> clazz) { return new Query<S>(clazz); } public List<T> run() { List<T> r = new LinkedList<T>(); for (Object o : l) { if (clazz.isInstance(o)) r.add(clazz.cast(o)); } return r; } } I can call this from Java as follows: Query<String> sq = Query.newQuery().refine(String.class); //NOTE NO <String> But if I try and do the same from Scala: val sq = Query.newQuery().refine(classOf[String]) I get the following error: error: type mismatch found :lang.this.class[scala.this.Predef.String] required: lang.this.class[?0] forSome{ type ?0 <: ? } val sq = Query.newQuery().refine(classOf[String]) This is only fixed by the insertion of the correct type parameter! val sq = Query.newQuery().refine[String](classOf[String]) Why can't scala infer this from my argument? Note I am using Scala 2.7

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  • unable to set fields of a collection-property elements after changing their order (elements becoming

    - by Jaroslav Záruba
    Hello I want to change order of objects in a collection, and then to access+modify fields of those items. Unfortunately the items somehow become 'deleted'. This is what I do... if(someCondition) { MainEvent mainEvent = pm.getObjectById(MainEvent.class, mainEventKey); /* * events in the original order * MainEvent.subEvents field is not in default fetch group, * therefore I also tried to add the named group into the * persistenceManeger fetch plan, no difference * (mainEvent is not instance of the Event sub/class BTW) */ List<Event> subEvents = mainEvent.getSubEvents(); // re-arrange the events according to keysOrdered { Map<Key, Event> eventMap = new HashMap<Key, Event>(); for(Event event : subEvents) eventMap.put(event.getKey(), event); List<Event> eventsOrdered = new LinkedList<Event>(); for(Key eventKey : keysOrdered) eventsOrdered.add(eventMap.put(eventKey, eventMap.get(eventKey))); // } // put the re-arranged items back into the collection property { subEvents.clear(); subEvents.addAll(eventsOrdered); // } pm.makePersistent(mainEvent); eventsOrdered = subEvents; } else eventsOrdered = getEventsUsingAlternateApproach(); /* * so by now the mainEvent variable does not exist; * could it be this lead the persistence manager to mark * my events as abandoned/obsolete/invalid/deleted...? */ for(Event event : eventsOrdered) event.setDate(new Date()); // -> "Cannot write fields to a deleted object" What am I doing wrong please?

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  • Did I implement clock drift properly?

    - by David Titarenco
    I couldn't find any clock drift RNG code for Windows anywhere so I attempted to implement it myself. I haven't run the numbers through ent or DIEHARD yet, and I'm just wondering if this is even remotely correct... void QueryRDTSC(__int64* tick) { __asm { xor eax, eax cpuid rdtsc mov edi, dword ptr tick mov dword ptr [edi], eax mov dword ptr [edi+4], edx } } __int64 clockDriftRNG() { __int64 CPU_start, CPU_end, OS_start, OS_end; // get CPU ticks -- uses RDTSC on the Processor QueryRDTSC(&CPU_start); Sleep(1); QueryRDTSC(&CPU_end); // get OS ticks -- uses the Motherboard clock QueryPerformanceCounter((LARGE_INTEGER*)&OS_start); Sleep(1); QueryPerformanceCounter((LARGE_INTEGER*)&OS_end); // CPU clock is ~1000x faster than mobo clock // return raw return ((CPU_end - CPU_start)/(OS_end - OS_start)); // or // return a random number from 0 to 9 // return ((CPU_end - CPU_start)/(OS_end - OS_start)%10); } If you're wondering why I Sleep(1), it's because if I don't, OS_end - OS_start returns 0 consistently (because of the bad timer resolution, I presume). Basically, (CPU_end - CPU_start)/(OS_end - OS_start) always returns around 1000 with a slight variation based on the entropy of CPU load, maybe temperature, quartz crystal vibration imperfections, etc. Anyway, the numbers have a pretty decent distribution, but this could be totally wrong. I have no idea.

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  • How to efficiently convert String, integer, double, datetime to binary and vica versa?

    - by Ben
    Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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  • To use the 'I' prefix for interfaces or not to

    - by ng
    That is the question? So how big a sin is it not to use this convention when developing a c# project? This convention is widely used in the .NET class library. However, I am not a fan to say the least, not just for asthetic reasons but I don't think it makes any contribution. For example is IPSec an interface of PSec? Is IIOPConnection An interface of IOPConnection, I usually go to the definition to find out anyway. So would not using this convention cause confusion? Are there any c# projects or libraries of note that drop this convention? Do any c# projects that mix conventions, as unfortunately Apache Wicket does? The Java class libraries have existed without this for many years, I don't feel I have ever struggled to read code without it. Also, should the interface not be the most primitive description? I mean IList<T> as an interface for List<T> in c#, is it not better to have List<T> and LinkedList<T> or ArrayList<T> or even CopyOnWriteArrayList<T>? The classes describe the implementation? I think I get more information here, than I do from List<T> in c#.

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