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  • How to optimize this simple function which translates input bits into words?

    - by psihodelia
    I have written a function which reads an input buffer of bytes and produces an output buffer of words where every word can be either 0x0081 for each ON bit of the input buffer or 0x007F for each OFF bit. The length of the input buffer is given. Both arrays have enough physical place. I also have about 2Kbyte free RAM which I can use for lookup tables or so. Now, I found that this function is my bottleneck in a real time application. It will be called very frequently. Can you please suggest a way how to optimize this function? I see one possibility could be to use only one buffer and do in-place substitution. void inline BitsToWords(int8 *pc_BufIn, int16 *pw_BufOut, int32 BufInLen) { int32 i,j,z=0; for(i=0; i<BufInLen; i++) { for(j=0; j<8; j++, z++) { pw_BufOut[z] = ( ((pc_BufIn[i] >> (7-j))&0x01) == 1? 0x0081: 0x007f ); } } } Please do not offer any compiler specific or CPU/Hardware specific optimization, because it is a multi-platform project.

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  • Most reliable split character

    - by JL
    Update If you were forced to use a single char on a split method, which char would be the most reliable? Definition of reliable: a split character that is not part of the individual sub strings being split.

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  • clever way to conditionally split this string?

    - by sprugman
    I've got a string that could be in one of two forms: prefix=key=value (which could have any characters, including '=') or key=value So I need to split it either on the first or second equals sign, based on a boolean that gets set elsewhere. I'm doing this: if ($split_on_second) { $parts = explode('=', $str, 3); $key = $parts[0] . '=' . $parts[1]; $val = $parts[2]; } else { $parts = explode('=', $str, 2); $key = $parts[0]; $val = $parts[1]; } Which should work, but feels inelegant. Got any better ideas in php? (I imagine there's a regex-ninja way to do it, but I'm not a regex-ninja.;-)

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  • Rails- MiniMagick commands not working

    - by digitalWestie
    I'm running windows xp and I've got MiniMagick and ImageMagick installed (latest versions). I'm now using the console to test out that everything works. Using the ms command prompt image magick works no problem. I'm testing this by using the identify command. Now, when I try to use MiniMagick from the console by entering image = MiniMagick::Image.new('image.jpg') It returns MiniMagickError, "ImageMagick command ("identify \"input.jpg\"") failed: {:status_code = #"'identify' is not recognized as an internal or external command,\noperable program or batch file.\n"} Can anybody help?

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  • String update in SQL Server

    - by Thiyaneshwaran S
    Currently I have varchar field. The delimiter is "$P$P$". The delimiter will appear at least once and at most twice in the varchar data. Eg. Sample Heading$P$P$Sample description$P$P$Sample conclusion Sample Heading$P$P$Sample Description If the delimiter appears twice, I need to insert a text before the second occurance of the delimiter. Eg: Sample Heading$P$P$Sample DescriptionINSERT TEXT HERE$P$P$Sample Conclusion If the delimiter occurs only once, then I need to insert a text at the end of the field. Eg: Sample Heading$P$P$Sample DescriptionAPPEND TEXT HERE How this can be done in SQL query?

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  • How to Concatenate 2 C strings, without overwriting any terminating Null characters?

    - by Ben313
    Hello, I am trying to set up a list of file names for a parameter to SHFileOperation. I want to be able to concatenate a file name onto the char array, but i dont want to get rid of the terminating character. for example, I want this: C:\...\0E:\...\0F:\...\0\0 when i use strcat(), it overwrites the null, so it looks like C:\...E:\...F:\...0\ Is there any easy way to do this? or am i going to have to code a new strcat for myself?

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  • Call function based off of a string in Lisp

    - by powerj1984
    I am passing in command line arguments to my Lisp program and they are formatted like this when they hit my main function: ("1 1 1" "dot" "2 2 2") I have a dot function and would like to call it directly from the argument, but this isn't possible because something like (funcall (second args)...) receives "dot" and not dot as the function name. I tried variations of this function: (defun remove-quotes (s) (setf (aref s 0) '"")) to no avail, before realizing that the quotes were not really a part of the string. Is there a simple way to do this, or should I just check each string and then call the appropriate function? Thanks!

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  • Format String become 0001, 0010 etc

    - by trycatch4j
    Hi all.., I have number : 1, 2, 3, 4, 10 But I wanna print that number 0001 0002 0003 0004 0010 I have search in google, the keyword is number format. but I've got nothing, I just get, frmat decimal such ass 1,000,000.00. hope you can suggest me a reference or give me some problem solving. Thanks,

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  • Population count of rightmost n integers

    - by Jason Baker
    I'm implementing Bagwell's Ideal Hash Trie in Haskell. To find an element in a sub-trie, he says to do the following: Finding the arc for a symbol s, requires ?nding its corresponding bit in the bit map and then counting the one bits below it in the map to compute an index into the ordered sub-trie. What is the best way to do this? It sounds like the most straightforward way of doing this is to select the bits below that bit and do a population count on the resulting number. Is there a faster or better way to do this?

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  • Strings - Filling In Leading Zeros Wtih A Zero

    - by headscratch
    I'm reading an array of hard-coded strings of numeric characters - all positions are filled with a character, even for the leading zeros. Thus, can confidently parse it using substring(start, end) to convert to numeric. Example: "0123 0456 0789" However, a string coming from a database does not fill in the leading zero with a 'zero character', it simply fetches the '123 456 789', which is correct for an arithmetic number but not for my needs and makes for parsing trouble. Before writing conditionals to check for leading zeros and adding them to the string if needed, is there a simple way of specifying they be filled with a character ? I'm not finding this in my Java book... I could have done the three conditionals in the time it took to post this but, this is more about 'education'... Thanks

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  • How does the stream manipulators work?

    - by Narek
    It is well known that the user can define stream manipulators like this: ostream& tab(ostream & output) { return output<< '\t'; } And this can be used in main() like this: cout<<'a'<<tab<<'b'<<'c'<<endl; Please explain me how does this all work? If operator<< assumes as a second parameter a pointer to the function that takes and returns ostream &, then please explain my why it is necessary? What would be wrong if the function does not take and return ostream & but it was void instead of ostream &? Also it is interesting why “dec”, “hex” manipulators take effect until I don’t change between them, but user defined manipulators should be always used in order to take effect for each streaming?

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  • C++ stringstream reads all zero's

    - by user69514
    I have a file which contains three integers per line. When I read the line I use a stringstream to separate the values, but it only reads the first value as it is. The other two are read as zero's. ifstream inputstream(filename.c_str()); if( inputstream.is_open() ){ string line; stringstream ss; while( getline(inputstream, line) ){ //check line and extract elements int id; double income; int members; ss.clear(); ss.str(line); ss >> id >> income >> members; In the case above, id is extracted correctly, but income, and members get assigned zero instead of the actual value.

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  • Java split is eating my characters.

    - by Fenris_uy
    Hi, I have a string like this String str = "la$le\$li$lo". I want to split it to get the following output "la","le\$li","lo". The \$ is a $ escaped so it should be left in the output. But when I do str.split("[^\\\\]\\$") y get "l","le\$l","lo". From what I get my regex is matching a$ and i$ and removing then. Any idea of how to get my characters back? Thanks

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