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• What is the right tool to detect VMT or heap corruption in Delphi ?

  - by Roland Bengtsson

  I'm a member in a team that use Delphi 2007 for a larger application and we suspect heap corruption because sometimes there are strange bugs that have no other explanation. I believe that the Rangechecking option for the compiler is only for arrays. I want a tool that give an exception or log when there is a write on a memory address that is not allocated by the application. Regards EDIT: The error is of type: Error: Access violation at address 00404E78 in module 'BoatLogisticsAMCAttracsServer.exe'. Read of address FFFFFFDD EDIT2: Thanks for all suggestions. Unfortunately I think that the solution is deeper than that. We use a patched version of Bold for Delphi as we own the source. Probably there are some errors introduced in the Bold framwork. Yes we have a log with callstacks that are handled by JCL and also trace messages. So a callstack with the exception can lock like this: 20091210 16:02:29 (2356) [EXCEPTION] Raised EBold: Failed to derive ServerSession.mayDropSession: Boolean OCL expression: not active and not idle and timeout and (ApplicationKernel.allinstances->first.CurrentSession <> self) Error: Access violation at address 00404E78 in module 'BoatLogisticsAMCAttracsServer.exe'. Read of address FFFFFFDD. At Location BoldSystem.TBoldMember.CalculateDerivedMemberWithExpression (BoldSystem.pas:4016) Inner Exception Raised EBold: Failed to derive ServerSession.mayDropSession: Boolean OCL expression: not active and not idle and timeout and (ApplicationKernel.allinstances->first.CurrentSession <> self) Error: Access violation at address 00404E78 in module 'BoatLogisticsAMCAttracsServer.exe'. Read of address FFFFFFDD. At Location BoldSystem.TBoldMember.CalculateDerivedMemberWithExpression (BoldSystem.pas:4016) Inner Exception Call Stack: [00] System.TObject.InheritsFrom (sys\system.pas:9237) Call Stack: [00] BoldSystem.TBoldMember.CalculateDerivedMemberWithExpression (BoldSystem.pas:4016) [01] BoldSystem.TBoldMember.DeriveMember (BoldSystem.pas:3846) [02] BoldSystem.TBoldMemberDeriver.DoDeriveAndSubscribe (BoldSystem.pas:7491) [03] BoldDeriver.TBoldAbstractDeriver.DeriveAndSubscribe (BoldDeriver.pas:180) [04] BoldDeriver.TBoldAbstractDeriver.SetDeriverState (BoldDeriver.pas:262) [05] BoldDeriver.TBoldAbstractDeriver.Derive (BoldDeriver.pas:117) [06] BoldDeriver.TBoldAbstractDeriver.EnsureCurrent (BoldDeriver.pas:196) [07] BoldSystem.TBoldMember.EnsureContentsCurrent (BoldSystem.pas:4245) [08] BoldSystem.TBoldAttribute.EnsureNotNull (BoldSystem.pas:4813) [09] BoldAttributes.TBABoolean.GetAsBoolean (BoldAttributes.pas:3069) [10] BusinessClasses.TLogonSession._GetMayDropSession (code\BusinessClasses.pas:31854) [11] DMAttracsTimers.TAttracsTimerDataModule.RemoveDanglingLogonSessions (code\DMAttracsTimers.pas:237) [12] DMAttracsTimers.TAttracsTimerDataModule.UpdateServerTimeOnTimerTrig (code\DMAttracsTimers.pas:482) [13] DMAttracsTimers.TAttracsTimerDataModule.TimerKernelWork (code\DMAttracsTimers.pas:551) [14] DMAttracsTimers.TAttracsTimerDataModule.AttracsTimerTimer (code\DMAttracsTimers.pas:600) [15] ExtCtrls.TTimer.Timer (ExtCtrls.pas:2281) [16] Classes.StdWndProc (common\Classes.pas:11583) The inner exception part is the callstack at the moment an exception is reraised. EDIT3: The theory right now is that the Virtual Memory Table (VMT) is somehow broken. When this happen there is no indication of it. Only when a method is called an exception is raised (ALWAYS on address FFFFFFDD, -35 decimal) but then it is too late. You don't know the real cause for the error. Any hint of how to catch a bug like this is really appreciated!!! We have tried with SafeMM, but the problem is that the memory consumption is too high even when the 3 GB flag is used. So now I try to give a bounty to the SO community :) EDIT4: One hint is that according the log there is often (or even always) another exception before this. It can be for example optimistic locking in the database. We have tried to raise exceptions by force but in test environment it just works fine. EDIT5: Story continues... I did a search on the logs for the last 30 days now. The result: "Read of address FFFFFFDB" 0 "Read of address FFFFFFDC" 24 "Read of address FFFFFFDD" 270 "Read of address FFFFFFDE" 22 "Read of address FFFFFFDF" 7 "Read of address FFFFFFE0" 20 "Read of address FFFFFFE1" 0 So the current theory is that an enum (there is a lots in Bold) overwrite a pointer. I got 5 hits with different address above. It could mean that the enum holds 5 values where the second one is most used. If there is an exception a rollback should occur for the database and Boldobjects should be destroyed. Maybe there is a chance that not everything is destroyed and a enum still can write to an address location. If this is true maybe it is possible to search the code by a regexpr for an enum with 5 values ? EDIT6: To summarize, no there is no solution to the problem yet. I realize that I may mislead you a bit with the callstack. Yes there are a timer in that but there are other callstacks without a timer. Sorry for that. But there are 2 common factors. An exception with Read of address FFFFFFxx. Top of callstack is System.TObject.InheritsFrom (sys\system.pas:9237) This convince me that VilleK best describe the problem. I'm also convinced that the problem is somewhere in the Bold framework. But the BIG question is, how can problems like this be solved ? It is not enough to have an Assert like VilleK suggest as the damage has already happened and the callstack is gone at that moment. So to describe my view of what may cause the error: Somewhere a pointer is assigned a bad value 1, but it can be also 0, 2, 3 etc. An object is assigned to that pointer. There is method call in the objects baseclass. This cause method TObject.InheritsForm to be called and an exception appear on address FFFFFFDD. Those 3 events can be together in the code but they may also be used much later. I think this is true for the last method call. EDIT7: We work closely with the the author of Bold Jan Norden and he recently found a bug in the OCL-evaluator in Bold framework. When this was fixed these kinds of exceptions decreased a lot but they still occasionally come. But it is a big relief that this is almost solved.

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• Error: cluster_port_ready: could not find psql binary

  - by Christoffer D. Brammer

  When I use apt-get install i get the error: Error: cluster_port_ready: could not find psql binary What do I do here? I have tried to remove PostgreSQL 8.2 but it gives this error: The following packages have unmet dependencies: postgresql-8.2: Depends: libkrb53 (>= 1.6.dfsg.1) but it is not installable Depends: postgresql-client-8.2 but it is not installable E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution). And then I end up at the start, with the error when trying apt-get -f install. /Christoffer

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• Error when running binary with root setuid under encrypted home directory

  - by carestad

  I'm using a VPN script for Juniper's Secure Access protocol form here, which executes a binary located under ~/.juniper_networks/network_connect/ncsvc with the following permissions: -rws--s--x 1 root root 1225424 okt. 25 13:54 ncsvc But when I do, I get the following error: ncsvc> Failed to setuid to root. Error 1: Operation not permitted Moving/copying the ~/.juniper_networks folder to e.g. /opt/juniper (with the same owner permissions), I don't get the error. In the forum thread at Ubuntuforums someone pointed out that it's probably because I have encrypted my /home and thus a "problem" with ecryptfs. How can I fix this?

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• A deque based on binary trees

  - by Greg Ros

  This is a simple immutable deque based on binary trees. What do you think about it? Does this kind of data structure, or possibly an improvement thereof, seem useful? How could I improve it, preferably without getting rid of its strengths? (Not in the sense of more operations, in the sense of different design) Does this sort of thing have a name? Red nodes are newly instantiated; blue ones are reused. Nodes aren't actually red or anything, it's just for emphasis.

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• How to find Sub-trees in non-binary tree

  - by kenny

  I have a non-binary tree. I want to find all "sub-trees" that are connected to root. Sub-tree is a a link group of tree nodes. every group is colored in it's own color. What would be be the best approach? Run recursion down and up for every node? The data structure of every treenode is a list of children, list of parents. (the type of children and parents are treenodes) Clarification: Group defined if there is a kind of "closure" between nodes where root itself is not part of the closure. As you can see from the graph you can't travel from pink to other nodes (you CAN NOT use root). From brown node you can travel to it's child so this form another group. Finally you can travel from any cyan node to other cyan nodes so the form another group

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• Computer Arithmetic - Binary for Decimal Numbers

  - by MarkPearl

  This may be of use to someone else doing this course… The Problem In the section on Computer Arithmetic it gives an example of converting -7.6875 to IEEE floating point format. I understand all the steps except for the first one, where it does the following... 7.6875 (base 10) = 111.1011 (base 2) I don't understand the conversion - I realize that 111 (base 2) = 7 (base 10), but how does the .6875 part relate to the .1011? Or am I totally off track with this? The Solution The fractional part of the decimal to binary conversion is done as follows: 0.6875 x 2 = 1.375 = 0.375 + 1 (Keep the 1 separate) 0.375 x 2   = 0.75   = 0.75    + 0 0.75 x 2    = 1.5      = 0.5      + 1 0.5 x 2     = 1.0       = 0.0       + 1 The bit pattern of 0s and 1s on the right-hand side gives you the fractional part. So 0.6875 (base 10) = .1011 (Base 2) See also Stallings, chapter 19.

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• Installing 64bit Java 7 - Cannot Execute Binary File

  - by warpstack

  So I downloaded the latest version of Java from Oracle so I could get a 64bit JVM on Ubuntu Server 10.10. After extracting the file and updating the alternatives I went to check my installation by running java -version and I get this error: -bash: /usr/bin/java: cannot execute binary file I'm at a loss for what to do here. My alternatives menu looks like this: Selection Path Priority Status ------------------------------------------------------------ 0 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 auto mode 1 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 manual mode 2 /usr/lib/jvm/java-7-openjdk-i386/jre/bin/java 1051 manual mode * 3 /usr/lib/jvm/jdk1.7.0/bin/java 3 manual mode After restarting the system I seem to be getting a totally new error when checking the java version. usr/bin/java: 1: Syntax error: end of file unexpected (expecting ")")

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• Algorithm for perfect non-binary graph layout

  - by mariki

  I have a complex non-binary graph model. Each tree node can have multiple children&parents (a node can also have a connection to it's "brother"). A node is represented as square on screen with lines to the connected nodes. For that I want to use Draw2D and GEF libraries. The problem I am facing is the graph layout. I need a nice algorithm that can reposition the square nodes and the connections with minimum intersections and also make it symmetric as possible.

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• How can I open binary image files? (.img)

  - by Simon Cahill

  I'm a Windows/Mac/Ubuntu and Androoid user, so I know what I'm talking about, when I say: How do I open binary image files? (.img) They just won't open, on any OS... I'm an Android dev... I'm currently working on a ROM, (I also program, using Windows) but I need to extract files, from .img files. I've converted them to .ext4.img but they just aren't recognized by Linux (Definitly not by Android), by Mac OS or Windows. In other words, I can't open, extract or mount them. Can anyone help me? I'm kinda confused...

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• SQL binary value to PHP variable leading zeros

  - by Agony

  Using sql query to pull data from a mssql database results in a value that still has leading zeros. The data in database is stored as binary(13) - so it will pull all 13 digits. However the value is a text, so any leading zeros will generally show up as '?' in a form on the site - and in return will update wrong data to the database later. So what i need is to only select/display the text itself, not all 13 bytes. using: SELECT CONVERT(char,uilock_pw) AS uipwd FROM tbl_UserAccount or SELECT uilock_pw FROM tbl_UserAccount still adds the leading zeros to the char array. Example in database: 0x71776531323300000000000000 Would show up as: qwe123??????? But should be: qwe123 Im not even sure what character those ? represent. Using Echo results in a normal qwe123 - but not in a form.

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• Unable to execute binary file. Exec format error

  - by user2689020

  I recently heard about Breach, a Node.js based browser. I was following the instructions on http://codeforgeek.com/2014/08/download-install-breach-browser-ubuntu-14-04/ to install it but got the following error : breach-v0.3.22-alpha.6-linux-x64/__AUTO_UPDATE_BUNDLE__/exo_browser/exo_browser: cannot execute binary file: Exec format error After some googling, I found that it is because I am trying to install the 64 bit package on the 32 bit Ubuntu installation. I tried to find 32 bit package of the same but ended up with no luck. The browser is only available in 64 bit packet(as far as i know). So, My question is : Is it possible to somehow install it on the 32 bit OS or if any program available which can run 64 bit applications on the 32 bit OS. I have been googling around and found no help. Can anyone help me? I am using Ubuntu 14.04 (32 Bit). Thank You

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• Why am I getting an IndexOutOfBoundsException here?

  - by Berzerker

  I'm getting an index out of bounds exception thrown and I don't know why, within my replaceValue method below. [null, (10,4), (52,3), (39,9), (78,7), (63,8), (42,2), (50,411)] replacement value test:411 size=7 [null, (10,4), (52,3), (39,9), (78,7), (63,8), (42,2), (50,101)] removal test of :(10,4) [null, (39,9), (52,3), (42,2), (78,7), (63,8), (50,101)] size=6 I try to replace the value again here and get an error... package heappriorityqueue; import java.util.*; public class HeapPriorityQueue<K,V> { protected ArrayList<Entry<K,V>> heap; protected Comparator<K> comp; int size = 0; protected static class MyEntry<K,V> implements Entry<K,V> { protected K key; protected V value; protected int loc; public MyEntry(K k, V v,int i) {key = k; value = v;loc =i;} public K getKey() {return key;} public V getValue() {return value;} public int getLoc(){return loc;} public String toString() {return "(" + key + "," + value + ")";} void setKey(K k1) {key = k1;} void setValue(V v1) {value = v1;} public void setLoc(int i) {loc = i;} } public HeapPriorityQueue() { heap = new ArrayList<Entry<K,V>>(); heap.add(0,null); comp = new DefaultComparator<K>(); } public HeapPriorityQueue(Comparator<K> c) { heap = new ArrayList<Entry<K,V>>(); heap.add(0,null); comp = c; } public int size() {return size;} public boolean isEmpty() {return size == 0; } public Entry<K,V> min() throws EmptyPriorityQueueException { if (isEmpty()) throw new EmptyPriorityQueueException("Priority Queue is Empty"); return heap.get(1); } public Entry<K,V> insert(K k, V v) { size++; Entry<K,V> entry = new MyEntry<K,V>(k,v,size); heap.add(size,entry); upHeap(size); return entry; } public Entry<K,V> removeMin() throws EmptyPriorityQueueException { if (isEmpty()) throw new EmptyPriorityQueueException("Priority Queue is Empty"); if (size == 1) return heap.remove(1); Entry<K,V> min = heap.get(1); heap.set(1, heap.remove(size)); size--; downHeap(1); return min; } public V replaceValue(Entry<K,V> e, V v) throws InvalidEntryException, EmptyPriorityQueueException { // replace the value field of entry e in the priority // queue with the given value v, and return the old value This is where I am getting the IndexOutOfBounds exception, on heap.get(i); if (isEmpty()){ throw new EmptyPriorityQueueException("Priority Queue is Empty."); } checkEntry(e); int i = e.getLoc(); Entry<K,V> entry=heap.get(((i))); V oldVal = entry.getValue(); K key=entry.getKey(); Entry<K,V> insert = new MyEntry<K,V>(key,v,i); heap.set(i, insert); return oldVal; } public K replaceKey(Entry<K,V> e, K k) throws InvalidEntryException, EmptyPriorityQueueException, InvalidKeyException { // replace the key field of entry e in the priority // queue with the given key k, and return the old key if (isEmpty()){ throw new EmptyPriorityQueueException("Priority Queue is Empty."); } checkKey(k); checkEntry(e); K oldKey=e.getKey(); int i = e.getLoc(); Entry<K,V> entry = new MyEntry<K,V>(k,e.getValue(),i); heap.set(i,entry); downHeap(i); upHeap(i); return oldKey; } public Entry<K,V> remove(Entry<K,V> e) throws InvalidEntryException, EmptyPriorityQueueException{ // remove entry e from priority queue and return it if (isEmpty()){ throw new EmptyPriorityQueueException("Priority Queue is Empty."); } MyEntry<K,V> entry = checkEntry(e); if (size==1){ return heap.remove(size--); } int i = e.getLoc(); heap.set(i, heap.remove(size--)); downHeap(i); return entry; } protected void upHeap(int i) { while (i > 1) { if (comp.compare(heap.get(i/2).getKey(), heap.get(i).getKey()) <= 0) break; swap(i/2,i); i = i/2; } } protected void downHeap(int i) { int smallerChild; while (size >= 2*i) { smallerChild = 2*i; if ( size >= 2*i + 1) if (comp.compare(heap.get(2*i + 1).getKey(), heap.get(2*i).getKey()) < 0) smallerChild = 2*i+1; if (comp.compare(heap.get(i).getKey(), heap.get(smallerChild).getKey()) <= 0) break; swap(i, smallerChild); i = smallerChild; } } protected void swap(int j, int i) { heap.get(j).setLoc(i); heap.get(i).setLoc(j); Entry<K,V> temp; temp = heap.get(j); heap.set(j, heap.get(i)); heap.set(i, temp); } public String toString() { return heap.toString(); } protected MyEntry<K,V> checkEntry(Entry<K,V> ent) throws InvalidEntryException { if(ent == null || !(ent instanceof MyEntry)) throw new InvalidEntryException("Invalid entry."); return (MyEntry)ent; } protected void checkKey(K key) throws InvalidKeyException{ try{comp.compare(key,key);} catch(Exception e){throw new InvalidKeyException("Invalid key.");} } }

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• More localized, efficient Lowest Common Ancestor algorithm given multiple binary trees?

  - by mstksg

  I have multiple binary trees stored as an array. In each slot is either nil (or null; pick your language) or a fixed tuple storing two numbers: the indices of the two "children". No node will have only one child -- it's either none or two. Think of each slot as a binary node that only stores pointers to its children, and no inherent value. Take this system of binary trees: 0 1 / \ / \ 2 3 4 5 / \ / \ 6 7 8 9 / \ 10 11 The associated array would be: 0 1 2 3 4 5 6 7 8 9 10 11 [ [2,3] , [4,5] , [6,7] , nil , nil , [8,9] , nil , [10,11] , nil , nil , nil , nil ] I've already written simple functions to find direct parents of nodes (simply by searching from the front until there is a node that contains the child) Furthermore, let us say that at relevant times, both all trees are anywhere between a few to a few thousand levels deep. I'd like to find a function P(m,n) to find the lowest common ancestor of m and n -- to put more formally, the LCA is defined as the "lowest", or deepest node in which have m and n as descendants (children, or children of children, etc.). If there is none, a nil would be a valid return. Some examples, given our given tree: P( 6,11) # => 2 P( 3,10) # => 0 P( 8, 6) # => nil P( 2,11) # => 2 The main method I've been able to find is one that uses an Euler trace, which turns the given tree, with a node A to be the invisible parent of 0 and 1 with a depth of -1, into: A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A And from that, simply find the node between your given m and n that has the lowest number; For example, to find P(6,11), look for a 6 and an 11 on the trace. The number between them that is the lowest is 2, and that's your answer. If A is in between them, return nil. -- Calculating P(6,11) -- A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A ^ ^ ^ | | | m lowest n Unfortunately, I do believe that finding the Euler trace of a tree that can be several thousands of levels deep is a bit machine-taxing...and because my tree is constantly being changed throughout the course of the programming, every time I wanted to find the LCA, I'd have to re-calculate the Euler trace and hold it in memory every time. Is there a more memory efficient way, given the framework I'm using? One that maybe iterates upwards? One way I could think of would be the "count" the generation/depth of both nodes, and climb the lowest node until it matched the depth of the highest, and increment both until they find someone similar. But that'd involve climbing up from level, say, 3025, back to 0, twice, to count the generation, and using a terribly inefficient climbing-up algorithm in the first place, and then re-climbing back up. Are there any other better ways?

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• I never really understood: what is Application Binary Interface (ABI)?

  - by claws

  I never clearly understood what is an ABI. I'm sorry for such a lengthy question. I just want to clearly understand things. Please don't point me to wiki article, If could understand it, I wouldn't be here posting such a lengthy post. This is my mindset about different interfaces: TV remote is an interface between user and TV. It is an existing entity but useless (doesn't provide any functionality) by itself. All the functionality for each of those buttons on the remote is implemented in the Television set. Interface: It is a "existing entity" layer between the functionality and consumer of that functionality. An, interface by itself is doesn't do anything. It just invokes the functionality lying behind. Now depending on who the user is there are different type of interfaces. Command Line Interface(CLI) commands are the existing entities, consumer is the user and functionality lies behind. functionality: my software functionality which solves some purpose to which we are describing this interface. existing entities: commands consumer: user Graphical User Interface(GUI) window,buttons etc.. are the existing entities, again consumer is the user and functionality lies behind. functionality: my software functionality which solves some purpose to which we are describing this interface. existing entities: window,buttons etc.. consumer: user Application Programming Interface(API) functions or to be more correct, interfaces (in interfaced based programming) are the existing entities, consumer here is another program not a user. and again functionality lies behind this layer. functionality: my software functionality which solves some purpose to which we are describing this interface. existing entities: functions, Interfaces(array of functions). consumer: another program/application. Application Binary Interface (ABI) Here is my problem starts. functionality: ??? existing entities: ??? consumer: ??? I've wrote few softwares in different languages and provided different kind of interfaces (CLI, GUI, API) but I'm not sure, if I ever, provided any ABI. http://en.wikipedia.org/wiki/Application_binary_interface says: ABIs cover details such as data type, size, and alignment; the calling convention, which controls how functions' arguments are passed and return values retrieved; the system call numbers and how an application should make system calls to the operating system; Other ABIs standardize details such as the C++ name mangling,[2] . exception propagation,[3] and calling convention between compilers on the same platform, but do not require cross-platform compatibility. Who needs these details? Please don't say, OS. I know assembly programming. I know how linking & loading works. I know what exactly happens inside. Where did C++ name mangling come in between? I thought we are talking at the binary level. Where did languages come in between? anyway, I've downloaded the [PDF] System V Application Binary Interface Edition 4.1 (1997-03-18) to see what exactly it contains. Well, most of it didn't make any sense. Why does it contain 2 chapters (4th & 5th) which describe the ELF file format.Infact, these are the only 2 significant chapters that specification. Rest of all the chapters "Processor Specific". Anyway, I thought that it is completely different topic. Please don't say that ELF file format specs are the ABI. It doesn't qualify to be Interface according to the definition. I know, since we are talking at such low level it must be very specific. But I'm not sure how is it "Instruction Set Architecture(ISA)" specific? Where can I find MS Window's ABI? So, these are the major queries that are bugging me.

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• How to create binary TIFF image?

  - by pineapple

  Is there any utility to create/convert a image to binary TIFF image. I want to use that binary tiff image as a input to a software ( an open source project which takes only binary tiff images as input).

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• Binary search in a sorted (memory-mapped ?) file in Java

  - by sds

  I am struggling to port a Perl program to Java, and learning Java as I go. A central component of the original program is a Perl module that does string prefix lookups in a +500 GB sorted text file using binary search (essentially, "seek" to a byte offset in the middle of the file, backtrack to nearest newline, compare line prefix with the search string, "seek" to half/double that byte offset, repeat until found...) I have experimented with several database solutions but found that nothing beats this in sheer lookup speed with data sets of this size. Do you know of any existing Java library that implements such functionality? Failing that, could you point me to some idiomatic example code that does random access reads in text files? Alternatively, I am not familiar with the new (?) Java I/O libraries but would it be an option to memory-map the 500 GB text file (I'm on a 64-bit machine with memory to spare) and do binary search on the memory-mapped byte array? I would be very interested to hear any experiences you have to share about this and similar problems.

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• How to pass binary data between two apps using Content Provider?

  - by Viktor

  I need to pass some binary data between two android apps using Content Provider (sharedUserId is not an option). I would prefer not to pass the data (a savegame stored as a file, small in size < 20k) as a file (ie. overriding openFile()) since this would necessitate some complicated temp-file scheme to cope with concurrency with several content provider accesses and a running game. I would like to read the file into memory under a mutex lock and then pass the binary array in the simplest way possible. How do I do this? It seems creating a file in memory is not a possibility due to the return type of openFile(). query() needs to return a Cursor. Using MatrixCursor is not possible since it applies toString() to all stored objects when reading it. What do I need to do? Implement a custom Cursor? This class has 30 abstract methods. Do I read the file, put it in a SQLite db and return the cursor? The complexity of this seemingly simple task is mindboggling.

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• How to create a Binary Tree from a General Tree?

  - by mno4k

  I have to solve the following constructor for a BinaryTree class in java: BinaryTree(GeneralTree<T> aTree) This method should create a BinaryTree (bt) from a General Tree (gt) as follows: Every Vertex from gt will be represented as a leaf in bt. If gt is a leaf, then bt will be a leaf with the same value as gt If gt is not a leaf, then bt will be constructed as an empty root, a left subTree (lt) and a right subTree (lr). Lt is a stric binary tree created from the oldest subtree of gt (the left-most subtree) and lr is a stric binary tree created from gt without its left-most subtree. The frist part is trivial enough, but the second one is giving me some trouble. I've gotten this far: public BinaryTree(GeneralTree<T> aTree){ if (aTree.isLeaf()){ root= new BinaryNode<T>(aTree.getRootData()); }else{ root= new BinaryNode<T>(null); // empty root LinkedList<GeneralTree<T>> childs = aTree.getChilds(); // Childs of the GT are implemented as a LinkedList of SubTrees child.begin(); //start iteration trough list BinaryTree<T> lt = new BinaryTree<T>(childs.element(0)); // first element = left-most child this.addLeftChild(lt); aTree.DeleteChild(hijos.elemento(0)); BinaryTree<T> lr = new BinaryTree<T>(aTree); this.addRightChild(lr); } } Is this the right way? If not, can you think of a better way to solve this? Thank you!

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• Why use bin2hex when inserting binary data from PHP into MySQL?

  - by Atli

  I heard a rumor that when inserting binary data (files and such) into MySQL, you should use the bin2hex() function and send it as a HEX-coded value, rather than just use mysql_real_escape_string on the binary string and use that. // That you should do $hex = bin2hex($raw_bin); $sql = "INSERT INTO `table`(`file`) VALUES (X'{$hex}')"; // Rather than $bin = mysql_real_escape_string($raw_bin); $sql = "INSERT INTO `table`(`file`) VALUES ('{$bin}')"; It is supposedly for performance reasons. Something to do with how MySQL handles large strings vs. how it handles HEX-coded values However, I am having a hard time confirming this. All my tests indicate the exact oposite; that the bin2hex method is ~85% slower and uses ~24% more memory. (I am testing this on PHP 5.3, MySQL 5.1, Win7 x64 - Using a farily simple insert loop.) For instance, this graph shows the private memory usage of the mysqld process while the test code was running: Does anybody have any explainations or reasources that would clarify this? Thanks.

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• Increasing the JVM maximum heap size for memory intensive applications

  - by Alceu Costa

  I need to run a Java memory intensive application that uses more than 2GB, but I am having problems to increase the heap maximum size. So far, I have tried the following approaches: Setting the -Xmx parameter, e.g. -Xmx3000m. This approaches fails at the creation of the JVM. From what I've googled, it looks like that -Xmx must be less than 2GB. Using the -XX:+AggressiveHeap option. When I try this approach I get an 'Not enough memory' error that tells that the heap size is 1273.4 MB, even though my computer has 8GB of memory. Is there another approach that I can try to increase the maximum heap size of the JVM? Here's a summary of the computer specs: OS: Windows 7 (64 bit) Processor: Intel Core i7 (2.66 GHz) Memory: 8 GB

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• How much is modern programming still tied to underyling digital logic?

  - by New Talk

  First of all: I've got no academic background. I'm working primarily with Java and Spring and I'm also fond of web programming and relational databases. I hope I'm using the right terms and I hope that this vague question makes some sense. Today the following question came to my mind: How much is modern programming still tied to the underlying digital logic? With modern programming I mean concepts like OOP, AOP, Java 7, AJAX, … I hope you get the idea. Do they no longer need the digital logic with which computers are working internally? Or is binary logic still ubiquitous when programming this way? If I'd change the inner workings of a computer overnight, would it matter, because my programming techniques are already that abstract? P. S.: With digital logic I mean the physical representation of everything "inside" the computer as zeroes and ones. Changed "binary" to "digital".

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• Count function on tree structure (non-binary)

  - by Spevy

  I am implementing a tree Data structure in c# based (largely on Dan Vanderboom's Generic implementation). I am now considering approach on handling a Count property which Dan does not implement. The obvious and easy way would be to use a recursive call which Traverses the tree happily adding up nodes (or iteratively traversing the tree with a Queue and counting nodes if you prefer). It just seems expensive. (I also may want to lazy load some of my nodes down the road). I could maintain a count at the root node. All children would traverse up to and/or hold a reference to the root, and update a internally settable count property on changes. This would push the iteration problem to when ever I want to break off a branch or clear all children below a given node. Generally less expensive, and puts the heavy lifting what I think will be less frequently called functions. Seems a little brute force, and that usually means exception cases I haven't thought of yet, or bugs if you prefer. Does anyone have an example of an implementation which keeps a count for an Unbalanced and/or non-binary tree structure rather than counting on the fly? Don't worry about the lazy load, or language. I am sure I can adjust the example to fit my specific needs. EDIT: I am curious about an example, rather than instructions or discussion. I know this is not technically difficult...

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• is there are nice unix command for dumping the text representation of a binary file.

  - by monkeyking

  Hi I got some binary files containing integers. Is there some nice unix command, that will allow me to dump it to a terminal without offset info etc? something like double int[4]; while(fread(tmp,sizeof(int),4,stdin)) for(int i=0;i<4;i++) printf("%d\t",tmp[i]); It seems that hexdump and od gives me the information I want, but the output is to verbose. I just want the contents.

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• Minimum and maximum height of binary search trees, 2-3-4 trees and B trees.

  - by jelly

  Hi, note this is not homework. But can anyone tell me how you find the min/max height of B trees, 2-3-4 trees and binary search trees? Thanks

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• How to write a recursive function that returns a linked list of nodes, when given a binary tree of n

  - by Jian Lin

  I was once asked of this in an interview: How to write a recursive function that returns a linked list of nodes, when given a binary tree of nodes? (flattening the data) For some reason, I tend to need more than 3 to 5 minutes to solve any recursive problem. Usually, 15 to 20 minutes will be more like it. How could we attack this problem, such as a very systematic way of reaching a solution, so that they can be solved in 3 to 5 minute time frame?

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