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• How do I write a Java text file viewer for big log files

  - by Hannes de Jager

  I am working on a software product with an integrated log file viewer. Problem is, its slow and unstable for really large files because it reads the whole file into memory when you view a log file. I'm wanting to write a new log file viewer that addresses this problem. What are the best practices for writing viewers for large text files? How does editors like notepad++ and VIM acomplish this? I was thinking of using a buffered Bi-directional text stream reader together with Java's TableModel. Am I thinking along the right lines and are such stream implementations available for Java?

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• Program visible to Linux as normal directory

  - by Xam

  I'm trying to write program to work as programmable directory, in other words: User, or other systems open that directory and read/write files or dirs. I try to create program to cache most used files in memory (less I/O to HDD), but right now I don't know how to achive that. There are probably some docs about this but I can't find them. I know that there is FUSE, NFS and others, but reading their source is quite difficult. If any one has info about implementation in C lang I'll be very grateful. Sorry for my English..

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• C string program

  - by mrblippy

  Hi, i have been given a task to do ar school that must read three strings in, store the third string in dynamically allocated memory and print out the last 4 letters of the first word alphabetically. Here is the program i have so far but the strings are all stored in different variables, making them hard to sort. if anyone could give me a hand and help me finish this program i would be very grateful. thanks #include <stdio.h> #include <stdlib.h> #include <string.h> int main() { char word1[101]; char word2[101]; char* word3; char buffer[101]; scanf("%s", word1); scanf("%s", word2); scanf("%s", buffer); word3 = (char *) malloc(strlen(buffer)+1); strcpy(word3, buffer); return 0; }

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• Address of array vs. address of array[0] - C language

  - by user324994

  My question is why does the address of an array differ from the address of its first position? I'm trying to write my own malloc, but to start out I'm just allocating a chunk of memory and playing around with the addresses. My code looks roughly like this: #define BUFF_SIZE 1024 static char *mallocbuff; int main(){ mallocbuff = malloc(BUFF_SIZE); printf("The address of mallocbuff is %d\n", &mallocbuff); printf("The address of mallocbuff[0] is %d\n", &mallocbuff[0]); } &mallocbuff is the same address every time I run it. &mallocbuff[0] is some random address every time. I was expecting the addresses to match each other. Can anyone explain why this isn't the case?

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• Android app crashes on second run

  - by Nick

  I have been working on my app and it runs on the simulator fine. I loaded it into my phone and now I have a problem. It runs fine when I first start it and also if I pick home and then restart it; however, if I use the back arrow and then restart it it crashes on that time, but will work out the next time I start it. I think it has to do with some kind of memory build up, but I verified onDestroy is being called, I figured that deletes everything my program created, right?

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• How do I read UTF-8 characters via a pointer?

  - by Jen

  Suppose I have UTF-8 content stored in memory, how do I read the characters using a pointer? I presume I need to watch for the 8th bit indicating a multi-byte character, but how exactly do I turn the sequence into a valid Unicode character? Also, is wchar_t the proper type to store a single Unicode character? This is what I have in mind: wchar_t readNextChar (char** p) { char ch = *p++; if (ch & 128) { // This is a multi-byte character, what do I do now? // char chNext = *p++; // ... but how do I assemble the Unicode character? ... } ... }

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• A way of allocating multidimensional arrays dynamically

  - by C77431

  salute.. I am learning dynamic allocations for multidimensional arrays in a book and I found some ways for that, And now haven't problem in it. But the author of the book shows us a way, but it doesn't work correctly. It is this: pbeans = new double [3][4]; // Allocate memory for a 3x4 array And this is the error: error C2440: '=' : cannot convert from 'int (*)[4]' to 'int *' how should i define pbeans ( if this type of coding is legal)? and what is the problem exactly? Regards.

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• what mysql table structure is better

  - by Sergey

  I have very complicated search algorithm on my site, so i decided to make a table with cache or maybe all possible results. I wanna ask what structure would be better, or maybe not the one of them? (mySQL) 1) word VARCHAR, results TEXT or BLOB where i'll store ids of found objects (for example 6 chars for each id) 2) word VARCHAR, result INT, but words are not unique now i think i'll have about 200 000 rows in 1) with 1000-10000 ids each row or 200 000 000+ rows in 2) First way takes more storage memory but i think it would be much faster to find 1 unique row among 200 000, than 1000 rows among 200 mln non unique rows i think about index on word column and no sphinx. So that do YOU think? p.s. as always, sorry for my english if it's not very good.

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• Simple integer encryption

  - by tloflin

  Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integer that, when fed into a second function D(i,k) (along with the key) produces the original integer? Obviously there are some simple reversible operations you can perform, but they all seem to produce clearly related outputs (e.g. consecutive inputs lead to consecutive outputs). Also, of course, there are cryptographically strong standard algorithms, but they don't produce small enough outputs (e.g. 32-bit). I know any 32-bit cryptography can be brute-forced, but I'm not looking for something cryptographically strong, just something that looks random. Theoretically speaking it should be possible; after all, I could just create a dictionary by randomly pairing every integer. But I was hoping for something a little less memory-intensive.

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• Cache bandwidth per tick for modern CPUs

  - by osgx

  Hello What is a speed of cache accessing for modern CPUs? How many bytes can be read or written from memory every processor clock tick by Intel P4, Core2, Corei7, AMD? Please, answer with both theoretical (width of ld/sd unit with its throughput in uOPs/tick) and practical numbers (even memcpy speed tests, or STREAM benchmark), if any. PS it is question, related to maximal rate of load/store instructions in assembler. There can be theoretical rate of loading (all Instructions Per Tick are widest loads), but processor can give only part of such, a practical limit of loading.

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• Is there a way to launch an aggressive and complete garbage collection in Java?

  - by Gnoupi

  For memory optimization reasons, I'm launching myself the garbage collector during profiling, to check if objects are correctly cleaned after disposing of them. The call to garbage collector is not enough, though, and it seems that there is no guarantee of what it will clean. Is there a way to call it, to be sure it will recover as much as it can, in profiling conditions (this would have no point in production, of course)? Or is "calling it several times" the only way to be "almost sure"? Or did I simply misunderstand something about the Garbage Collector?

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• How to find root cause for "too many connections" error in MySQL/PHP

  - by Nir

  I'm running a web service which runs algorithms that serve millions of calls daily and run some background processing as well. Every now and than I see "Too many connections" error in attempts to connect to the MySQL box" for a few seconds. However this is not necessarily attributed to high traffic times or anything I can put my finger on. I want to find the bottleneck causing it. Other than in the specific times this happens the server isn't too loaded in terms of CPU and Memory, and has 2-3 connections (threads) open and everything works smoothly. (I use Zabbix for monitoring) Any creative ideas on how to trace it?

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• Improving the performance of an nHibernate Data Access Layer.

  - by Amitabh

  I am working on improving the performance of DataAccess Layer of an existing Asp.Net Web Application. The scenerios are. Its a web based application in Asp.Net. DataAccess layer is built using NHibernate 1.2 and exposed as WCF Service. The Entity class is marked with DataContract. Lazy loading is not used and because of the eager-fetching of the relations there is huge no of database objects are loaded in the memory. No of hits to the database is also high. For example I profiled the application using NHProfiler and there were about 50+ sql calls to load one of the Entity object using the primary key. I also can not change code much as its an existing live application with no NUnit test cases at all. Please can I get some suggestions here?

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• SQL Server Compact Edition 3.5 performance

  - by Wili

  I am using SQL Server CE 3.5 SP1 in one of my client applications. When a user loads the program and starts using it, performance is fine. If the user lets the program sit idle for a while, it takes a considerable amount of time (10 or more seconds) for the program to respond. Every time the user asks for a new screen, a call is made to the SQL CE database to get the data for that screen. It seems like the hard drive may be going to sleep and then when the database is accessed, the hard drive has to wake back up. Is it possible to load the entire database into memory and work from that? Are there any other suggestions on how to increase performance?

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• Casting Class into String and Vice Versa in JAVA

  - by topgun_ivard

  I have a program in which I need to store a Class object into memory by casting it into String. Is it possible to convert the String back into the original Class so that I can use that class variables? I am doing this in JAVA. Example: test.java class hello{ public String h1; public String h2; } public class test { public static void main(String[] args) { hello h = new hello(); h.h1 = "hello"; h.h2 = "world"; String s = h.toString(); System.out.println("Print s : "+s); // Now I need to convert String s into type hello so that // I can do this: // (hello)s.h1; // (hello)s.h2; } } NOTE: this is not a homework, this is a personal project and I would be grateful if anyone can help! Thanks! Ivar

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• reading specific lines from a file

  - by MacUsers

  What's the best way of reading only the specific lines (based on matching text) from a file? This is what I'm doing now: match_txt = "lhcb" for inFile in os.listdir('.'): readFile = open(inFile, 'r') lines = readFile.readlines() readFile.close() for line in lines: if line.find(match_txt)==0: #< do stuff here > i.e. I'm reading the lines, only with "lhcb" in it, from all the files in the present directory one by one. Is it the best way of doing that? Can it be done without loading the whole file in the memory in the first place?

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• Save NSCache Contents to Disk

  - by Cory Imdieke

  I'm writing an app that needs to keep an in-memory cache of a bunch of objects, but that doesn't get out of hand so I'm planning on using NSCache to store it all. Looks like it will take care of purging and such for me, which is fantastic. I'd also like to persist the cache between launches, so I need to write the cache data to disk. Is there an easy way to save the NSCache contents to a plist or something? Are there perhaps better ways to accomplish this using something other than NSCache? This app will be on the iPhone, so I'll need only classes that are available in iOS 4+ and not just OS X. Thanks!

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• DataSet XML export is empty

  - by Shaine

  I've got in-memory dataset with couple of tables that is populated in code. Data-bound grids on the gui show table contents without a problem. Then I try to export the dataset into XML: ds.WriteXml(fdSave.FileName, XmlWriteMode.WriteSchema); and get empty XML (with couple of lines regarding dataset names but without any tables) If I export table directly I've got all the data but dataset name is obviously wrong: ds.Fields.WriteXml(fdSave.FileName, XmlWriteMode.WriteSchema); What am I missing? Is there any reasonable way to write the whole dataset into file?

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• Can I make a pointer to the code, and pass to the next instruction?

  - by drigoSkalWalker

  Like this link http://gcc.gnu.org/onlinedocs/gcc-3.3.1/gcc/Labels-as-Values.html I can get the memory address of an label, so if I declare a label, get your address, and add your address, i will pass to next instruction? some ilustration int main () { void *ptr; label: instruction 1; instruction 2; ptr = &&label; // So if I do it... ptr = ptr + 1; // I will get the instruction 2 correct?? Thanks for all answers.

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• Microsoft Enterprise Logging Application Block - Reading Log File

  - by Or A

  Hi, I'm using MS log application block for logging my application event into a file called app-trace.log which located on the c:\temp folder. I'm trying to find the best way to read this file at runtime and display it when the user asks for it. now i have 2 issues: it seems that this kind of feature is not supported by the framework, hence i have to write this reader myself. am i missing something here? is there any better way of getting this data (w/o buffering it in the memory or saving it into another file). if i'm taking the only alternative that left for me, and implementing the reader myself, when i'm tring to do: System.IO.FileStream fs = new System.IO.FileStream(@"c:\temp\app-trace.log", FileMode.Open, FileAccess.Read); i'm getting "File being used by another process c#", probably the file is locked by the application block. is there any way to access and read it anyhow? Thank

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• Recognize active objects with a capacitive touch screen display

  - by lucgian84

  I'm trying to develop an app that can recognize an active object (for example: a memory) that touch the smartphone display. Before I start to develop I've to know if there's any objects that my touch screen display can recognize? Which device can be recognizable by a smartphone display? I'm interested to know that for iPhone or for Android phone. I found this app and you can see that with a card I can interact with a mobile device, now I'm asking you if anyone know how to do this kind of app with an iPhone or with an Android phone. Does anyone knows how to do that? There's a library (iOS or Android) to recognize object that I put over the display?

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• Can I force MySQL to output results before query is completed?

  - by Gordon Royle

  I have a large MySQL table (about 750 million rows) and I just want to extract a couple of columns. SELECT id, delid FROM tbl_name; No joins or selection criteria or anything. There is an index on both fields (separately). In principle, it could just start reading the table and spitting out the values immediately, but in practice the whole system just chews up memory and basically grinds to a halt. It seems like the entire query is being executed and the output stored somewhere before ANY output is produced... I've searched on unbuffering, turning off caches etc, but just cannot find the answer. (mysqldump is almost what I want except it dumps the whole table - but at least it just starts producing output immediately)

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• Fastmm4 and leaking handles...

  - by JD

  Hi to all, I have just used FastMM4 to detect leaks. I did not realise our application was using a DLL which was leaking event handles and so I fixed any leaks reported by FastMM4 but not the handles as it was not reported. My questions are, would have FastMM4 have reported the leaking event handles? Would this require me to rebuild the dlls with FastMM4 included? I also heard someone mention ShareMM, do I need to add that? I am using Delphi2007, which I think is using the borland memory manager and if so, should I replace it with the fastMM4 one? What are the steps to do that? Sorry for asking so many questions, I am looking at delphi after a few years of doing .net development. JD.

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• What is the result of "new int[ 0 ]"? [closed]

  - by ArunSaha

  Possible Duplicates: What does zero-sized array allocation do/mean? C++ new int[0] — will it allocate memory? int * p; p = new int[ 0 ]; What is the expected outcome when new is called for zero number of elements? Is the outcome defined or undefined? Further, is it okay to call delete [] p; on that pointer? What is the intuition/analogy to this situation of pointer to an array of zero elements? Thanks in advance. Regards, Arun

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• Are destructors of automatic objects invoked when terminate is called?

  - by nbolton

  I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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