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• Address of instruction causing SIGSEGV in external program

  - by karramba

  I want to get address of instruction that causes external program to SIGSEGV. I tried using ptrace for this, but I'm getting EIP from kernel space (probably default signal handler?). How GDB is able to get the correct EIP? Is there a way to make GDB provide this information using some API? edit: I don't have sources of the program, only binary executable. I need automation, so I can't simply use "run", "info registers" in GDB. I want to implement "info registers" in my own mini-debugger :)

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• Which of FILE* or ifstream has better memory usage?

  - by Viet

  I need to read fixed number of bytes from files, whose sizes are around 50MB. To be more precise, read a frame from YUV 4:2:0 CIF/QCIF files (~25KB to ~100KB per frame). Not very huge number but I don't want whole file to be in the memory. I'm using C++, in such a case, which of FILE* or ifstream has better (less/minimal) memory usage? Please kindly advise. Thanks! EDIT: I read fixed number of bytes: 25KB or 100KB (depending on QCIF/CIF format). The reading is in binary mode and forward-only. No seeking needed. No writing needed, only reading. EDIT: If identifying better of them is hard, which one does not require loading the whole file into memory?

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• Pyserial : How to send data to drive SIPO

  - by bino oetomo

  Dear All .. I'm learning to drive a stepper motor with Python. It's hard now to find a PC with paralel port. So My plan is using a USB-Serial .. and a SIPO (serial in parallel out) shift register circuit. As you know with this circuit we need to send a binary data in series and this data will be stored in it's register. Next we need to send another one pulse to make it shift the data out to the out-port. How to do it using pyserial ? Sincerely -bino-

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• Why does the right-shift operator produce a zero instead of a one?

  - by mrt181

  Hi, i am teaching myself java and i work through the exercises in Thinking in Java. On page 116, exercise 11, you should right-shift an integer through all its binary positions and display each position with Integer.toBinaryString. public static void main(String[] args) { int i = 8; System.out.println(Integer.toBinaryString(i)); int maxIterations = Integer.toBinaryString(i).length(); int j; for (j = 1; j < maxIterations; j++) { i >>= 1; System.out.println(Integer.toBinaryString(i)); } In the solution guide the output looks like this: 1000 1100 1110 1111 When i run this code i get this: 1000 100 10 1 What is going on here. Are the digits cut off? I am using jdk1.6.0_20 64bit. The book uses jdk1.5 32bit.

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• C# - High Quality Byte Array Conversion of Images

  - by Lijo

  Hi Team, I am converting images to byte array and storing in a text file using the following code. I am retrieving them successfully as well. My concern is that the quality of the retrieved image is not up to the expectation. Is there a way to have better conversion to byte array and retrieving? I am not worried about the space conception. Please share your thoughts. string plaintextStoringLocation = @"D:\ImageSource\Cha5.txt"; string bmpSourceLocation = @"D:\ImageSource\Cha50.bmp"; ////Read image Image sourceImg = Image.FromFile(bmpSourceLocation); ////Convert to Byte[] byte[] clearByteArray = ImageToByteArray(sourceImg); ////Store it for future use (in plain text form) StoreToLocation(clearByteArray, plaintextStoringLocation); //Read from binary byte[] retirevedImageBytes = ReadByteArrayFromFile(plaintextStoringLocation); //Retrieve from Byte[] Image destinationImg = ByteArrayToImage(retirevedImageBytes); //Display Image pictureBox1.Image = destinationImg; Thanks Lijo

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• Does any Version Control System like SVN, Git, or Mercurial let you "keep latest version" but not th

  - by Jian Lin

  In our project files, if there are binary files, such as .doc, .xls, .jpg, and we choose to not keep their past revisions (just keeping a latest version is ok), is there a way to tell SVN, Git, or Mercurial or some other tool to skip the revisions for these files or for a particular folder? Say, there is a 4MB .doc file that I need to check in hundred of times, but I don't really care so much about its past versions. So if the system keeps 100 revisions of it, that's already 400MB... checking in 300 times means 1.2GB for 1 file and that's not good. Only the latest version is good so that everybody can sync to it.

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• c++ normalizing data sizes across systems

  - by Bocochoco

  I have a struct with three variables: two unsigned ints and an unsigned char. From my understanding, a c++ char is always 1 byte regardless of what operating system it is on. The same can't be said for other datatypes. I am looking for a way to normalize POD's so that when saved into a binary file, the resulting file is readable on any operating system that the code is compiled for. I changed my struct to use a 1-byte alignment by adding #pragma as follows: #pragma pack(push, 1) struct test { int a; } #pragma pack(pop) but that doesn't necessarily mean that int a is exactly 4 bytes on every os, I don't think? Is there a way to ensure that a file saved from my code will always be readable?

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• How to find the number of inversions in an array ?

  - by Michael

  This is an phone interview question: "Find the number of inversions in an array". I guess they mean O(N*log N) solution since O(N^2) is trivial. I guess it cannot be better than O(N*log N) since sorting is O(N*log N) I have checked a similar question from SO and can summarize the answers as follows: Calculate half the distance the elements should be moved to sort the array : copy the array and sort the copy. For each element of the original array a[i] find it's position j in the sorted copy (binary search) and sum abs(i - j)/2. Modify merge sort : modify merge to count inversions between two sorted arrays (it takes O(N)) and run merge sort with the modified merge. Does it make sense ? Are there other (maybe simpler) solution ? Isn't it too hard for a phone interview ?

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• Matlab - Propagate unit vectors on to the edge of shape boundaries

  - by Graham

  Hi I have a set of unit vectors which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking the unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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• Masking a bit in C returning unexpected result

  - by Eamorr

  0x7F000000 is 0111 1111 0000 0000 0000 0000 0000 0000 in 32 bit binary. 0x01000058 is 0000 0001 0000 0000 0000 0000 0101 1000. When I AND the two numbers together I expect 0000 0001 0000 0000 0000 0000 0000 0000, but for some reason I get 0. Here is my code: #define MASK_binop 0x80000000 #define MASK_operation 0x7F000000 int instruction=atoi(line); if((MASK_binop & instruction)>0) printf("binop\n"); else if((MASK_operation & instruction)>0) printf("operation\n"); Each of the above comparisons keeps returning zero. Is it something to do with 32/64 bits? I'm using 64-bit compiler.

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• In Linux, how can I completely disregard the contents of /etc/ld.so.cache?

  - by BillyBBone

  Hi, For the purposes of prototyping a new set of shared libraries in a development sandbox (to which I don't have root access), I'd like to know how to execute a binary while completely overriding the contents of /etc/ld.so.cache, so that none of the system libraries get loaded. How can this be done? I have looked at mechanisms like setting the LD_LIBRARY_PATH environment variable or launching the program wrapped inside /lib/ld-linux.so, but these methods all seem to supplement the loading of libraries from /etc/ld.so.cache, but not override it completely. Help?

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• write cache and write sequence order

  - by excanoe

  ok, here i have some weird question: let say we have some binary file (.log), and sequence of write operations, for example log1, log2, log3 and each has some block size n (raw data). question: can I be sure that log1,log2 and log3 sequences can be written in the correct order in ONE file, even if i have few cache levels (disk hardware and os level)? update very interested in what will be with records order (not with records) if we have software or hardware failure (reboot or another reason). update there can be some percent of write failures, but main question is: will write order stay correct?

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• What's the best way to build software to not require the newest glibc?

  - by ZorbaTHut

  I'm attempting to build a binary package that can be run on multiple Linux distributions. It's currently built on Ubuntu 10.04, but it fails on Ubuntu 8.04 with the following error: ./test: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by ./test) ./test: /usr/lib/libstdc.so.6: version `GLIBC_2.11' not found (required by ./test) What's the preferred way to solve this problem? Is there a way to install an old glibc on a new box and build against it, or do I have to build on an old distribution? And if I build against an old glibc, will it work on a new glibc? Or, alternatively, are there just some handy compiler flags or packages I could install to solve the problem?

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• How do I effectively write to 146 output files in C++ using cstdlib library

  - by Elpezmuerto

  I have a very large binary file and I need to create separate files based on the id within the input file. There are 146 output files and I am using cstdlib and fopen and fwrite. FOPEN_MAX is 20, so I can't keep all 146 output files open at the same time. I also want to minimize the number of times I open and close an output file. How can I write to the output files effectively? I also must use the cstdlib library due to legacy code.

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• [NSData dataWithContentsOfFile:path] doesn't work

  - by Felics

  Hello, when I have the fallowing code to read a binary file: NSString* file = [NSString stringWithUTF8String:fileName]; NSString* filePath = resource ? [[NSBundle mainBundle] pathForResource:file ofType:nil] : [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent: file]; NSData* fileData = [NSData dataWithContentsOfFile:filePath]; Where "fileName" and resource are load function parameters. "resource" is used to know if the file is located in application bundle or in Documents. Sometimes this code works well and sometimes it doesn't. As far I saw this problem is random. I can run the code 10 times in a row and it works fine and after that it gives me nil data without any modification. Does anybody knows what could be the problem? Could it be related with file extension or file name? Thank you. PS: I use this code on iPhone Simulator and the file exists in application bundle.

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• What's the best way to build software that doesn't require the newest glibc?

  - by ZorbaTHut

  I'm attempting to build a binary package that can be run on multiple Linux distributions. It's currently built on Ubuntu 10.04, but it fails on Ubuntu 8.04 with the following error: ./test: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by ./test) ./test: /usr/lib/libstdc.so.6: version `GLIBC_2.11' not found (required by ./test) What's the preferred way to solve this problem? Is there a way to install an old glibc on a new box and build against it, or do I have to build on an old distribution? And if I build against an old glibc, will it work on a new glibc? Or, alternatively, are there just some handy compiler flags or packages I could install to solve the problem?

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• Execute python code inside browser without Jython

  - by proportional

  Is there a way to execute python code in a browser, other than using Jython and an applet? The execution does not have to deal with anything related to graphics. For example, just sum all the digits of a binary 1Gb file (chosen by the browser user) and then return the result to the server. I am aware that python can be executed remotely outside a browser, but my requirement is to be done inside a browser. For sure, I take for granted the user will keep the right to execute or not, and will be asked to do so, and all this security stuff... but that is not my question.

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• What is the fastest method to calculate substring

  - by Misha Moroshko

  I have a huge "binary" string, like: 1110 0010 1000 1111 0000 1100 1010 0111.... It's length is 0 modulo 4, and may reach 500,000. I have also a corresponding array: {14, 2, 8, 15, 0, 12, 10, 7, ...} (every number in the array corresponds to 4 bits in the string) Given this string, this array, and a number N, I need to calculate the following substring string.substr(4*N, 4), i.e.: for N=0 the result should be 1110 for N=1 the result should be 0010 I need to perform this task many many times, and my question is what would be the fastest method to calculate this substring ? One method is to calculate the substring straight forward: string.substr(4*N, 4). I'm afraid this one is not efficient for such huge strings. Another method is to use array[N].toString(2) and then wrap the result with zeros if needed. I'm not sure how fast is this. May be you have any other ideas ?

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• How to create diagrams for papers.

  - by Simon

  I want to create some diagrams for some papers. Diagrams will contain some text, e.g. some console output. I need images for using also in html files. There is TikZ so can create images like this: http://www.texample.net/tikz/examples/boxes-with-text-and-math/ http://www.texample.net/tikz/examples/rule-based-diagram/ http://www.texample.net/tikz/examples/scenario-tree/ but as a result I get some ps/pdf files, not images. What's more I want to generate the pictures from text files as I want to track changes in some VCS, any binary files are not suitable for that.

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• Using nsIZipWriter or other to compress a string as a string?

  - by Daniel

  I need to be able to take a javascript string, compress it using any fast and available means and get back a binary string/blob. Background: The extension I'm developing needs to send various large content to my server. It does this conveniently by dynamically creating a form, adding fields to the form and posting it. Some of these fields are just too big bandwidth wise for multiple use. I'd like to be able to compress them before adding them and then maybe base64'ing them if the characters cause a problem in the message. Any ideas? I could use nsiZipWriter with temporary files on disk but that is quite ugly and probably sluggish.

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• question about missing element in array

  - by davit-datuashvili

  i have following problem from book introduction algorithm second edition by MIT university problem is following An array A[1 . . n] contains all the integers from 0 to n except one. It would be easy to determine the missing integer in O(n) time by using an auxiliary array B[0 . . n] to record which numbers appear in A. In this problem, however, we cannot access an entire integer in A with a single operation. The elements of A are represented in binary, and the only operation we can use to access them is “fetch the j th bit of A[i],” which takes constant time. Show that if we use only this operation, we can still determine the missing inte- ger in O(n) time please help

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• Generate MySQL data dump in SQL from PHP

  - by Álvaro G. Vicario

  I'm writing a PHP script to generate SQL dumps from my database for version control purposes. It already dumps the data structure by means of running the appropriate SHOW CREATE .... query. Now I want to dump data itself but I'm unsure about the best method. My requirements are: I need a record per row Rows must be sorted by primary key SQL must be valid and exact no matter the data type (integers, strings, binary data...) Dumps should be identical when data has not changed I can detect and run mysqldump as external command but that adds an extra system requirement and I need to parse the output in order to remove headers and footers with dump information I don't need (such as server version or dump date). I'd love to keep my script as simple as I can so it can be hold in an standalone file. What are my alternatives?

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• Are MongoDB and CouchDB perfect substitutes?

  - by raoulsson

  I haven't got my hands dirty yet with neither CouchDB nor MongoDB but I would like to do so soon... I also have read a bit about both systems and it looks to me like they cover the same cases... Or am I missing a key distinguishing feature? I would like to use a document based storage instead of a traditional RDBMS in my next project. I also need the datastore to handle large binary objects (images and videos) automatically replicate itself to physically separate nodes rendering the need of an additional RDBMS superfluous Are both equally well suited for these requirements? Thanks!

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• Image ransfer using hessian protocol from client's folder to tomcat server

  - by ?? ?

  My goal is to upload a image(.jpg or .png)from client's folder to tomcat6 server through hessian protocol. And do image processing using opencv on server, then return the image back to client. Question1. Is the following transfering steps correct? put a test.jpg image on client's folder -- convert the test.jpg in client.java(main.java) class to BufferedImage -- convert the BufferedImage to mat or Iplimage in server for using openCV.I have set a hello world sample from Simple Messaging Example using Hessian , and searched from Hessian with large binary data and other websites, but still dont know how to use it! Question2. Is there a related JAVA sample code? Thank you very much. Btw, I am using ubuntu12+netbeans7.2

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• iPhone SDK: Downloading large files from a server into the app bundle.

  - by Jessica

  Hi, I am building an app that plays multiple video files, But I would like to know How do you download a video file (100mb - 300mb) from a server into the application's bundle so it can later be locally referred to in code? The reason I want this type of a set up in my app is that I don't want the app binary to be made unnecessarily large due to including videos some users may not want. Also does this violate any of apple's terms? Also would it be simple to implement a progress view with this kind of set up and if so how? Any help is appreciated.

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