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  • ARM cortex: mutex using bit banding

    - by Jeff V
    Given that, on the ARM Cortex M3, I can: atomically read a single bit atomically set a single bit atomically clear a single bit How can I combine these for a mutex style set of operations: try lock take lock release lock It seems that try_lock or take_lock would require two operations that would not be atomic. Do I need more control to accomplish this? Disable global interrupts would do it but it seems there should be a more surgical approach.

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  • Why is it useful to count the number of bits?

    - by Scorchin
    I've seen the numerous questions about counting the number of set bits in a insert type of input, but why is it useful? For those looking for algorithms about bit counting, look here: http://stackoverflow.com/questions/1517848/counting-common-bits-in-a-sequence-of-unsigned-longs http://stackoverflow.com/questions/472325/fastest-way-to-count-number-of-bit-transitions-in-an-unsigned-int http://stackoverflow.com/questions/109023/best-algorithm-to-count-the-number-of-set-bits-in-a-32-bit-integer

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  • Excel ODBC and 64 bit server

    - by Causas
    using ASP.NET I need to update an excel template. Our server is running Windows 2008 in 64 bit mode. I am using the following code to access the excel file: ... string connection = @"Provider=MSDASQL;Driver={Microsoft Excel Driver (*.xls)};DBQ=" + path + ";"; ... IF the application pool is set to Enable 32 bit applications the code works as expected; however the oracle driver I am using fails as it is only 64 bit. If Enable 32-bit applications is set to false the excel code fails with the error: Data source name not found and no default driver specified Any suggestions?

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  • Getting a specific bit value in a byte string

    - by ignoramus
    There is a byte at a specific index in a byte string which represents eight flags; one flag per bit in the byte. If a flag is set, its corresponding bit is 1, otherwise its 0. For example, if I've got b'\x21' the flags would be 0001 0101 # Three flags are set at indexes 3, 5 and 7 # and the others are not set What would be the best way to get each bit value in that byte, so I know whether a particular flag is set or not? (Preferably using bitwise operations)

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  • What is the difference between a 32-bit and 64-bit processor?

    - by JJG
    I have been trying to read up on 32-bit and 64-bit processors (http://en.wikipedia.org/wiki/32-bit_processing). My understanding is that a 32-bit processor (like x86) has registers 32-bits wide. I'm not sure what that means. So it has special "memory spaces" that can store integer values up to 2^32? I don't want to sound stupid, but I have no idea about processors. I'm assuming 64-bits is, in general, better than 32-bits. Although my computer now (one year old, Win 7, Intel Atom) has a 32-bit processor.

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  • Setting processor to 32-bit mode

    - by dboarman-FissureStudios
    It seems that the following is a common method given in many tutorials on switching a processor from 16-bit to 32-bit: mov eax, cr0 ; set bit 0 in CR0-go to pmode or eax, 1 mov cr0, eax Why wouldn't I simply do the following: or cr0, 1 Is there something I'm missing? Possibly the only thing I can think of is that I cannot perform an operation like this on the cr0 register.

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  • Erlang bit indexing

    - by GTDev
    I am currently trying to learn erlang and what I am trying to do is to perform an operation on specific indices of an array stored in a bit array or int. If there is a 0 in a position, the index into the array at that position is not used. So envision the following: Example the array is: [1, 3, 5, 42, 23] My bit array is: 21 = 10101 in binary so I'm using indicies 1,3,5 so I'm calling a function on [1, 5, 23] my function is of the form my_function(Array, BitArray) -> SubArray = get_subarray_from_bitarray(Array, BitArray), process_subarray(SubArray). And I need help with the get_subarray_from_bitarray(). I know erlang has special syntax around bit strings (something like <<) so is there an efficient way of indexing into the bit array to get the indicies?

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  • Finding N contiguous zero bits in an integer to the left of the MSB position of another integer

    - by James Morris
    The problem is: given an integer val1 find the position of the highest bit set (Most Significant Bit) then, given a second integer val2 find a contiguous region of unset bits, with the minimum number of zero bits given by width to the left of the position (ie, in the higher bits). Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions? Edit: Some background not strictly required. The offset result is a count of bits from the high bit, not from the low bit as maybe expected. This will be part of a wider algorithm which scans a 2D array for a 2D area of zero bits. Here, for testing, the algorithm has been simplified. val1 represents the first integer which does not have all bits set found in a row of the 2D array. From this the 2D version would scan down which is what val2 represents. Here's some output showing success and failure: t_bits:32 t_high: 10000000000000000000000000000000 ( 2147483648 ) --------- ----------------------------------- *** fit within left of msb test *** ----------------------------------- val1: 00000000000000000000000010000000 ( 128 ) val2: 01000001000100000000100100001001 ( 1091569929 ) msb: 7 offbit:0 + width: 8 = 8 mask: 11111111000000000000000000000000 ( 4278190080 ) b: 01000001000000000000000000000000 ( 1090519040 ) offbit:8 + width: 8 = 16 mask: 00000000111111110000000000000000 ( 16711680 ) b: 00000000000100000000000000000000 ( 1048576 ) offbit:12 + width: 8 = 20 mask: 00000000000011111111000000000000 ( 1044480 ) b: 00000000000000000000000000000000 ( 0 ) offbit:12 iters:10 ***** found room for width:8 at offset: 12 ***** ----------------------------------- *** fit within left of msb test *** ----------------------------------- val1: 00000000000000000000000001000000 ( 64 ) val2: 00010000000000001000010001000001 ( 268469313 ) msb: 6 offbit:0 + width: 13 = 13 mask: 11111111111110000000000000000000 ( 4294443008 ) b: 00010000000000000000000000000000 ( 268435456 ) offbit:4 + width: 13 = 17 mask: 00001111111111111000000000000000 ( 268402688 ) b: 00000000000000001000000000000000 ( 32768 ) ***** mask: 00001111111111111000000000000000 ( 268402688 ) offbit:17 iters:15 ***** no room found for width:13 ***** (iters is the count of iterations of the inner while loop)

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  • Can I run a 64-bit VMWare image on a 32-bit machine?

    - by John Sibly
    Can I run a 64-bit VMWare image on a 32-bit machine? I've Googled this but there doesn't seem to be a conclusive answer. I know that it would have to be completely emulated and would run like a dog - but slow performance isn't necessarily an issue as I'm just interested in testing some of my background services code on 64-bit platforms.

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  • CreateThread() fails on 64 bit Windows, works on 32 bit Windows. Why?

    - by Stephen Kellett
    Operating System: Windows XP 64 bit, SP2. I have an unusual problem. I am porting some code from 32 bit to 64 bit. The 32 bit code works just fine. But when I call CreateThread() for the 64 bit version the call fails. I have three places where this fails. 2 call CreateThread(). 1 calls beginthreadex() which calls CreateThread(). All three calls fail with error code 0x3E6, "Invalid access to memory location". The problem is all the input parameters are correct. HANDLE h; DWORD threadID; h = CreateThread(0, // default security 0, // default stack size myThreadFunc, // valid function to call myParam, // my param 0, // no flags, start thread immediately &threadID); All three calls to CreateThread() are made from a DLL I've injected into the target program at the start of the program execution (this is before the program has got to the start of main()/WinMain()). If I call CreateThread() from the target program (same params) via say a menu, it works. Same parameters etc. Bizarre. If I pass NULL instead of &threadID, it still fails. If I pass NULL as myParam, it still fails. I'm not calling CreateThread from inside DllMain(), so that isn't the problem. I'm confused and searching on Google etc hasn't shown any relevant answers. If anyone has seen this before or has any ideas, please let me know. Thanks for reading.

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  • Comparing floats in their bit representations

    - by sczizzo
    Say I want a function that takes two floats (x and y), and I want to compare them using not their float representation but rather their bitwise representation as a 32-bit unsigned int. That is, a number like -495.5 has bit representation 0b11000011111001011100000000000000 or 0xC3E5C000 as a float, and I have an unsigned int with the same bit representation (corresponding to a decimal value 3286614016, which I don't care about). Is there any easy way for me to perform an operation like <= on these floats using only the information contained in their respective unsigned int counterparts?

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  • How to correctly load 32-bit DLL dependencies when running a program from a batch file

    - by neilwhitaker1
    I have written a tool that references Microsoft.TeamFoundation.VersionControl.Client.dll, which is a 32-bit DLL. When I build my tool on 64-bit Windows, I set Visual Studio to specifically target X86 in order to force it to a 32-bit build. Targetting X86 instead of All-CPU's prevents me from getting a BadImageFormatException, as long as I invoke the tool directly (e.g. by typing "myTool.exe" on the command line). However, if I run a batch file that invokes the tool, I still get the exception. This happens even if the batch file runs in a 32-bit command prompt (%WINDIR%\SysWOW64\cmd.exe). What else can I do to make this work?

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  • Use branching in TFS for 32 bit and 64 bit version of a software?

    - by Malkier
    Hi everyone, we are in the process of porting a 32bit application, which uses the Outlook Redemption DLL to a 64 bit version, since redemption has recently been released as a 64 bit version as well. We'd like to maintain two versions of the application, one for 32 and one for 64 bit. What is the best way to organize these projects under team foundation server source control? Would I create a branch of the existing 32 bit version? Copying the whole project seems sub-optimal since it would duplicate all the business logic code. Any suggestions?

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  • How we run a .NET 32-bit application in a 64-bit Windows server?

    - by Geo
    We are installing a third party application in one of our 64-bit Windows servers. This application apparently was build with the compiler option set to choose the platform at run time. When we run the application it gives us an error: System.BadImageFormatException: is not a valid Win32 application. I have seen in MSDN forums that in order to fix this error I have to build the application set to 32-bit, and that way it will run fine on a 64-bit server. I check on other StackOverflow links Other Posts. How to get around this situation? For everyone that wants to know more information: The application is running fine in a 32-bit test server. IIS version 6 using SQL Server Express 2005 On the Web Service Extension there are both Framework64\v2.0.50727\aspnet_isapi.dll and Framework\v2.0.50727\aspnet_isapi.dll

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  • Horizontally Flip a One Bit Bitmap Line

    - by roygbiv
    I'm looking for an algorithm to flip a 1 Bit Bitmap line horizontally. Remember these lines are DWORD aligned! I'm currently unencoding an RLE stream to an 8 bit-per-pixel buffer, then re-encoding to a 1 bit line, however, I would like to try and keep it all in the 1 bit space in an effort to increase its speed. Profiling indicates this portion of the program to be relatively slow compared to the rest. Example line (Before Flip): FF FF FF FF 77 AE F0 00 Example line (After Flip): F7 5E EF FF FF FF F0 00

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  • 32-bit JVM on 64-bit Windows crashes on launch with -Xmx1300m and plenty of free memory

    - by Konrad Garus
    I'm struggling with Java heap space settings. The default Java on Windows is the 32-bit client regardless of OS version (that's what Oracle recommends to all users). It appears to set max heap size to 256 MB by default, and that is too little for me. I use a custom launcher to start the application. I would like it to use more memory on computers with plenty RAM, and default to -Xmx512m on those with less RAM. As far as I'm aware, the only way is the static -Xmx setting (that has to be set on launch). I have a user who has 8 GB RAM, 64-bit Windows and 32-bit Java 7. Maximum memory visible to the JVM is 4G (as returned by querying OperatingSystemMXBean). I understand why, no issue. For some reason my application is unable to start for this user with -Xmx1300m, even though he has 2.3G free memory. He closed some applications (having 5G free memory), and still it would not launch. The error reported to me was: error occured during init of vm could not reserve enough space for object heap What's going on? Could it be that the 32-bit JVM is only able to address the "first" 4G of memory and has to have a 1300M block available within those first 4 gigabytes? How can I solve this problem, except for asking everyone to install 64-bit Java (what is unlikely to be acceptable)?

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  • bit count in array

    - by davit-datuashvili
    hello i have following question i know that to count number of set bit in number of number of 1 bit there is following code int t ;//in which we want count how many bit are set for instance 3 011 there is 2 bit set int count=0; while(t>0){ t&=(t-1); count++; } now let take array example int x[]={3,5,6,8,9,7}; i have following code int sum=0; int count; for (int i=0;i<x.length;i++){ count=0; while (x[i]>0){ x[i]&=(x[i]-1); count++; } sum+=count; } I have question what is wrong? it doesn't work doesn't show me result;

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  • How to convert a BufferedImage to 8 bit?

    - by Zach Sugano
    I was looking at the ImageConverter class, trying to figure out how to convert a BufferedImage to 8-bit color, but I have no idea how I would do this. I was also searching around the internet and I could find no simple answer, they were all talking about 8 bit grayscale images. I simply want to convert the colors of an image to 8 bit... nothing else, no resizing no nothing. Does anyone mind telling me how to do this.

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  • Unmountable boot volume blue screen, what should I do?

    - by Josh
    I was trying to install an update from NVIDIA for my GTX 560, but while it was installing, my computer shut off. After a few minutes, I turned it back on. It got to the Windows boot screen and then had a blue screen error and if left on it would just keep doing that. A few details about my PC: I haven't added any new hardware or software, I'm running Windows XP Professional 32 bit and Windows XP Professional 64 bit on the same hard drive for about 2 years now. I have 2 other hard drives also, but I don't have one large enough to hold everything from my main hard drive, so formatting isn't an option. Now, as for what I've done so far: I've scanned the RAM with "memtest - 86 v3.4" and it said that it was good. I scanned the hard drive in question with chkdsk /r and it gets to 50% and tells me something along the lines of "the drive has one or more unrepairable problems". I also tried to use chkdsk on the drive I installed the new copy of Windows XP on and it got to 75% then jumped back down to 50% and stayed there (I had to reboot the pc). So, after that, I turned off auto reboot and got to read the blue screen error code and I looked it up only to find that nobody seems to have this problem, just problems close to it. The error code is 0x000000ed and I've seen a lot of these online but none that matched the detailed part of the code UNMOUNTABLE_BOOT_VOLUME 0x000000ed (0xfffffadf513c19a0, 0xffffffffc0000006, 0, 0) So, I have installed another copy of Windows XP Professional 32 bit on one of my other hard drives in hopes of accessing the data on the drive in question and when it booted it asked if I wanted chkdsk to scan the drive in question and this is what it found: file record segments 12740, 12741, 12742 and 12743 were reported unreadable. Then it says "recovering lost files" but it sits there for a few seconds and then just boots to Windows. I can't access the drive in question from Windows as far as I can tell, it just says "drive not accessible" and when I go to properties it says that the drive has 100% free space. So, after that failed I didn't give up, I looked for another way to access the drive in question. I used a Ubuntu bootable disk and was able to access the drive in question without any problems. However, I can't access the registry editor because it's a .exe file and that won't load from Ubuntu. I made a copy of the "Windows" folder and put it on one of my other drives and that's where I'm stuck at now. I'm sure my drive works fine, I know chkdsk can't fix the problem with it and I know what caused the problem in the first place for the most part, but I don't know what to do about it. I have a laptop that I can use to download and burn disks if needed and I also have the other copy of Windows XP Professional 32 bit that I can use that's installed on the computer in question (so I know it's not a hardware issue). I'm pretty sure it's a driver issue or the update was editing the registry when it shut off and left me when a broken registry. I've tried accessing C:\Windows\System32\CONFIG only to find that the Windows XP disk repair option can't even access the files on the drive in question. It seems I'll need to be able to do everything from Ubuntu unless there is something I haven't tried with the Windows XP disk. I didn't install the update on Windows XP 64 bit but yet it also has the same blue screen error (that's where the error code above came from but I haven't checked to see if they are the same). They both stopped working at the same time, so I assume it's one problem causing both to not work.

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