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  • Workaround for basic syntax not being parsed.

    - by Mark Tomlin
    I want to have a class property that allow for an expression to take place on the right side of the equals sign. All versions of PHP choke on the following code, but it is written in this way to allow for easier extendibility in the future. /* Example SDK Class */ class SDK { /* Runtime Option Flags */ // Strings # 0: Makes no change to the strings. var $STRING_NONE = (1 << 0); # 1: Removes color codes from the string. var $STRING_STRIP_COLOR = (1 << 1); # 2: Removes language codes from the string. var $STRING_STRIP_LANG = (1 << 2); # 3: Removes all formatting from the string. var $STRING_STRIP = SELF::STRING_STRIP_COLOR & SELF::STRING_STRIP_LANG; # 4: Converts color codes to HTML & UTF-8. var $STRING_HTML = (1 << 3); # 8: Converts color codes to ECMA-48 escape color codes & UTF-8. var $STRING_CONSOLE = (1 << 4); # 16: Changes player names only. var $STRING_NAMES = (1 << 5); # 32: Changes host names only. var $STRING_HOSTS = (1 << 6); function SDK($fString = SELF::STRING_HTML & SELF::STRING_NAMES & SELF_HOST) { // constructor code. } } $SDK &= new SDK(SDK::STRING_NONE); (1 << 0) seems like very basic syntax to me, and is not fathomable why PHP would not allow for such a thing. Can anyone think of a work around that would maintain readability and future expandability of the following code?

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  • A question in java.lang.Integer internal code

    - by Daziplqa
    Hi folks, While looking in the code of the method: Integer.toHexString I found the following code : public static String toHexString(int i) { return toUnsignedString(i, 4); } private static String toUnsignedString(int i, int shift) { char[] buf = new char[32]; int charPos = 32; int radix = 1 << shift; int mask = radix - 1; do { buf[--charPos] = digits[i & mask]; i >>>= shift; } while (i != 0); return new String(buf, charPos, (32 - charPos)); } The question is, in toUnsignedString, why we create a char arr of 32 chars?

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  • C#: Shift left assignment operator behavior

    - by Austin Salonen
    I'm running code that sometimes yields this: UInt32 current; int left, right; ... //sometimes left == right and no shift occurs current <<= (32 + left - right); //this works current <<= (32 - right); current <<= left; It appears for any value = 32, only the value % 32 is shifted. Is there some "optimization" occurring in the framework?

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  • How is joystick axis information formatted from a USB Joystick?

    - by aquanar
    I actually just have a rather small question, but I have had the HARDEST time finding information about it. For the application I am programming for, there will be a 3-axis joystick being connected via USB to a Windows XP computer, and it is being handled by directx. That information will then be sent elsewhere to an embedded controller. I don't need to know too much of the intricacies of how directx handles it, but I want to know, how is the data for the axes formatted? Nearest I can tell, most joysticks nowadays have 12 bits of resolution, so is the data output as a 12-bit 2's compliment number? And after that, is it represented as a signed 16-bit integer when it is captured from directx? I'd like to know this so I know how I will work with the data at the embedded platform side, such as how to format the packets sending data to the embedded side, as well ashow to use the information once it is on the embedded side.

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  • Get length of bits used in int

    - by sigvardsen
    If you have the binary number 10110 how can I get it to return 11111? e.g a new binary number that sets all bits to 1 after the first 1, there are some likewise examples listed below: 101 should return 111 (3 bit length) 011 should return 11 (2 bit length) 11100 should be return 11111 (5 bit length) 101010101 should return 111111111 (9 bit length) How can this be obtained the easiest way in Java? I could come up with some methods but they are not very "pretty".

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  • Negative logical shift

    - by user320862
    In Java, why does -32 -1 = 1 ? It's not specific to just -32. It works for all negative numbers as long as they're not too big. I've found that x -1 = 1 x -2 = 3 x -3 = 7 x -4 = 15 given 0 x some large negative number Isn't -1 the same as << 1? But -32 << 1 = -64. I've read up on two's complements, but still don't understand the reasoning.

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  • Count bits used in int

    - by sigvardsen
    If you have the binary number 10110 how can I get it to return 5? e.g a number that tells how many bits are used? There are some likewise examples listed below: 101 should return 3 000000011 should return 2 11100 should return 5 101010101 should return 9 How can this be obtained the easiest way in Java? I have come up with the following method but can i be done faster: public static int getBitLength(int value) { int l = 1; if (value >> 16 > 0) { value = value >> 16; l += 16; } if (value >> 8 > 0) { value = value >> 8; l += 8; } if (value >> 4 > 0) { value = value >> 4; l += 4; } if (value >> 2 > 0) { value = value >> 2; l += 2; } if (value >> 1 > 0) { value = value >> 1; l += 1; } return l; }

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  • What is the safest way to subtract two System.Runtime.InteropServices.ComTypes.FILETIME objects

    - by Anindya Chatterjee
    I wonder what is the safest way to subtract two System.Runtime.InteropServices.ComTypes.FILETIME objects? I used the following code but sometimes it gives me ArithmaticOverflow exception due to the negative number in Low 32-bit values. I am not sure enclosing the body with unchecked will serve the purpose or not. Please give me some suggestion on how to do it safely without getting any runtime exception or CS0675 warning message. private static UInt64 SubtractTimes(FILETIME a, FILETIME b) { UInt64 aInt = ((UInt64)(a.dwHighDateTime << 32)) | (UInt32)a.dwLowDateTime; UInt64 bInt = ((UInt64)(b.dwHighDateTime << 32)) | (UInt32)b.dwLowDateTime; return aInt - bInt; }

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  • setBit java method using bit shifting and hexadecimal code - question

    - by somewhat_confused
    I am having trouble understanding what is happening in the two lines with the 0xFF7F and the one below it. There is a link here that explains it to some degree. http://www.herongyang.com/java/Bit-String-Set-Bit-to-Byte-Array.html I don't know if 0xFF7FposBit) & oldByte) & 0x00FF are supposed to be 3 values 'AND'ed together or how this is supposed to be read. If anyone can clarify what is happening here a little better, I would greatly appreciate it. private static void setBit(byte[] data, final int pos, final int val) { int posByte = pos/8; int posBit = pos%8; byte oldByte = data[posByte]; oldByte = (byte) (((0xFF7F>>posBit) & oldByte) & 0x00FF); byte newByte = (byte) ((val<<(8-(posBit+1))) | oldByte); data[posByte] = newByte; } passed into this method as parameters from a selectBits method was setBit(out,i,val); out = is byte[] out = new byte[numOfBytes]; (numOfBytes can be 7 in this situation) i = which is number [57], the original number from the PC1 int array holding the 56-integers. val = which is the bit taken from the byte array from the getBit() method.

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  • How to define and work with an array of bits in C?

    - by Eddy
    I want to create a very large array on which I write '0's and '1's. I'm trying to simulate a physical process called random sequential adsorption, where units of length 2, dimers, are deposited onto an n-dimensional lattice at a random location, without overlapping each other. The process stops when there is no more room left on the lattice for depositing more dimers (lattice is jammed). Initially I start with a lattice of zeroes, and the dimers are represented by a pair of '1's. As each dimer is deposited, the site on the left of the dimer is blocked, due to the fact that the dimers cannot overlap. So I simulate this process by depositing a triple of '1's on the lattice. I need to repeat the entire simulation a large number of times and then work out the average coverage %. I've already done this using an array of chars for 1D and 2D lattices. At the moment I'm trying to make the code as efficient as possible, before working on the 3D problem and more complicated generalisations. This is basically what the code looks like in 1D, simplified: int main() { /* Define lattice */ array = (char*)malloc(N * sizeof(char)); total_c = 0; /* Carry out RSA multiple times */ for (i = 0; i < 1000; i++) rand_seq_ads(); /* Calculate average coverage efficiency at jamming */ printf("coverage efficiency = %lf", total_c/1000); return 0; } void rand_seq_ads() { /* Initialise array, initial conditions */ memset(a, 0, N * sizeof(char)); available_sites = N; count = 0; /* While the lattice still has enough room... */ while(available_sites != 0) { /* Generate random site location */ x = rand(); /* Deposit dimer (if site is available) */ if(array[x] == 0) { array[x] = 1; array[x+1] = 1; count += 1; available_sites += -2; } /* Mark site left of dimer as unavailable (if its empty) */ if(array[x-1] == 0) { array[x-1] = 1; available_sites += -1; } } /* Calculate coverage %, and add to total */ c = count/N total_c += c; } For the actual project I'm doing, it involves not just dimers but trimers, quadrimers, and all sorts of shapes and sizes (for 2D and 3D). I was hoping that I would be able to work with individual bits instead of bytes, but I've been reading around and as far as I can tell you can only change 1 byte at a time, so either I need to do some complicated indexing or there is a simpler way to do it? Thanks for your answers

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  • Macros to set and clear bits

    - by volting
    Im trying to write a few simple macros to simplify the task of setting and clearing bits which should be a simple task however I cant seem to get them to work correctly. #define SET_BIT(p,n) ((p) |= (1 << (n))) #define CLR_BIT(p,n) ((p) &= (~(1) << (n)))

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  • How can I access the sign bit of a number in C++?

    - by Keand64
    I want to be able to access the sign bit of a number in C++. My current code looks something like this: int sign bit = number >> 31; That appears to work, giving me 0 for positive numbers and -1 for negative numbers. However, I don't see how I get -1 for negative numbers: if 12 is 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 1100 then -12 is 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 0011 and shifting it 31 bits would make 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0001 which is 1, not -1, so why do I get -1 when I shift it?

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  • Efficient bitshifting an array of int?

    - by nn
    Hi, To be on the same page, let's assume sizeof(int)=4 and sizeof(long)=8. Given an array of integers, what would be an efficient method to bitshift the array to either the left or right? I am contemplating an auxiliary variable such as a long, that will compute the bitshift for the first pair of elements (index 0 and 1) and set the first element (0). Continuing in this fashion the bitshift for elements (index 1 and 2) will be computer, and then index 1 will be set. I think this is actually a fairly efficient method, but there are drawbacks. I cannot bitshift greater than 32 bits. I think using multiple auxiliary variables would work, but I'm envisioning recursion somewhere along the line.

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  • Setting last N bits in an array

    - by Martin
    I'm sure this is fairly simple, however I have a major mental block on it, so I need a little help here! I have an array of 5 integers, the array is already filled with some data. I want to set the last N bits of the array to be random noise. [int][int][int][int][int] set last 40 bits [unchanged][unchanged][unchanged][24 bits of old data followed 8 bits of randomness][all random] This is largely language agnostic, but I'm working in C# so bonus points for answers in C#

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  • Convert bit vector (array of booleans) to an integer, and integer to bit vector, in Java.

    - by dreeves
    What's the best way to unstub the following functions? // Convert a bit-vector to an integer. int bitvec2int(boolean[] b) { [CODE HERE] } // Convert an integer x to an n-element bit-vector. boolean[] int2bitvec(int x, int n) { [CODE HERE] } Or is there a better way to do that sort of thing than passing boolean arrays around? This comes up in an Android app where we need an array of 20 booleans to persist and the easiest way to do that is to write an integer or string to the key-value store. I'll post the way we (Bee and I) wrote the above as an answer. Thanks!

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  • What is the trick in pAddress & ~(PAGE_SIZE - 1) to get the page's base address

    - by Dbger
    Following function is used to get the page's base address of an address which is inside this page: void* GetPageAddress(void* pAddress) { return (void*)((ULONG_PTR)pAddress & ~(PAGE_SIZE - 1)); } But I couldn't quite get it, what is the trick it plays here? Conclusion: Personally, I think Amardeep's explanation plus Alex B's example are best answers. As Alex B's answer has already been voted up, I would like to accept Amardeep's answer as the official one to highlight it! Thanks you all.

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  • C Population Count of unsigned 64-bit integer with a maximum value of 15

    - by BitTwiddler1011
    I use a population count (hamming weight) function intensively in a windows c application and have to optimize it as much as possible in order to boost performance. More than half the cases where I use the function I only need to know the value to a maximum of 15. The software will run on a wide range of processors, both old and new. I already make use of the POPCNT instruction when Intel's SSE4.2 or AMD's SSE4a is present, but would like to optimize the software implementation (used as a fall back if no SSE4 is present) as much as possible. Currently I have the following software implementation of the function: inline int population_count64(unsigned __int64 w) { w -= (w 1) & 0x5555555555555555ULL; w = (w & 0x3333333333333333ULL) + ((w 2) & 0x3333333333333333ULL); w = (w + (w 4)) & 0x0f0f0f0f0f0f0f0fULL; return int(w * 0x0101010101010101ULL) 56; } So to summarize: (1) I would like to know if it is possible to optimize this for the case when I only want to know the value to a maximum of 15. (2) Is there a faster software implementation (for both Intel and AMD CPU's) than the function above?

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