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  • Higher order function « filter » in C++

    - by Red Hyena
    Hi all. I wanted to write a higher order function filter with C++. The code I have come up with so far is as follows: #include <iostream> #include <string> #include <functional> #include <algorithm> #include <vector> #include <list> #include <iterator> using namespace std; bool isOdd(int const i) { return i % 2 != 0; } template < template <class, class> class Container, class Predicate, class Allocator, class A > Container<A, Allocator> filter(Container<A, Allocator> const & container, Predicate const & pred) { Container<A, Allocator> filtered(container); container.erase(remove_if(filtered.begin(), filtered.end(), pred), filtered.end()); return filtered; } int main() { int const a[] = {23, 12, 78, 21, 97, 64}; vector<int const> const v(a, a + 6); vector<int const> const filtered = filter(v, isOdd); copy(filtered.begin(), filtered.end(), ostream_iterator<int const>(cout, " ")); } However on compiling this code, I get the following error messages that I am unable to understand and hence get rid of: /usr/include/c++/4.3/ext/new_allocator.h: In instantiation of ‘__gnu_cxx::new_allocator<const int>’: /usr/include/c++/4.3/bits/allocator.h:84: instantiated from ‘std::allocator<const int>’ /usr/include/c++/4.3/bits/stl_vector.h:75: instantiated from ‘std::_Vector_base<const int, std::allocator<const int> >’ /usr/include/c++/4.3/bits/stl_vector.h:176: instantiated from ‘std::vector<const int, std::allocator<const int> >’ Filter.cpp:29: instantiated from here /usr/include/c++/4.3/ext/new_allocator.h:82: error: ‘const _Tp* __gnu_cxx::new_allocator<_Tp>::address(const _Tp&) const [with _Tp = const int]’ cannot be overloaded /usr/include/c++/4.3/ext/new_allocator.h:79: error: with ‘_Tp* __gnu_cxx::new_allocator<_Tp>::address(_Tp&) const [with _Tp = const int]’ Filter.cpp: In function ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’: Filter.cpp:30: instantiated from here Filter.cpp:23: error: passing ‘const std::vector<const int, std::allocator<const int> >’ as ‘this’ argument of ‘__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> > std::vector<_Tp, _Alloc>::erase(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, __gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >) [with _Tp = const int, _Alloc = std::allocator<const int>]’ discards qualifiers /usr/include/c++/4.3/bits/stl_algo.h: In function ‘_FIter std::remove_if(_FIter, _FIter, _Predicate) [with _FIter = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _Predicate = bool (*)(int)]’: Filter.cpp:23: instantiated from ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’ Filter.cpp:30: instantiated from here /usr/include/c++/4.3/bits/stl_algo.h:821: error: assignment of read-only location ‘__result.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = const int*, _Container = std::vector<const int, std::allocator<const int> >]()’ /usr/include/c++/4.3/ext/new_allocator.h: In member function ‘void __gnu_cxx::new_allocator<_Tp>::deallocate(_Tp*, size_t) [with _Tp = const int]’: /usr/include/c++/4.3/bits/stl_vector.h:150: instantiated from ‘void std::_Vector_base<_Tp, _Alloc>::_M_deallocate(_Tp*, size_t) [with _Tp = const int, _Alloc = std::allocator<const int>]’ /usr/include/c++/4.3/bits/stl_vector.h:136: instantiated from ‘std::_Vector_base<_Tp, _Alloc>::~_Vector_base() [with _Tp = const int, _Alloc = std::allocator<const int>]’ /usr/include/c++/4.3/bits/stl_vector.h:286: instantiated from ‘std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const _Alloc&) [with _InputIterator = const int*, _Tp = const int, _Alloc = std::allocator<const int>]’ Filter.cpp:29: instantiated from here /usr/include/c++/4.3/ext/new_allocator.h:98: error: invalid conversion from ‘const void*’ to ‘void*’ /usr/include/c++/4.3/ext/new_allocator.h:98: error: initializing argument 1 of ‘void operator delete(void*)’ /usr/include/c++/4.3/bits/stl_algobase.h: In function ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false, _II = const int*, _OI = const int*]’: /usr/include/c++/4.3/bits/stl_algobase.h:435: instantiated from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false, _II = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _OI = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >]’ /usr/include/c++/4.3/bits/stl_algobase.h:466: instantiated from ‘_OI std::copy(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _OI = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >]’ /usr/include/c++/4.3/bits/vector.tcc:136: instantiated from ‘__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> > std::vector<_Tp, _Alloc>::erase(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, __gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >) [with _Tp = const int, _Alloc = std::allocator<const int>]’ Filter.cpp:23: instantiated from ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’ Filter.cpp:30: instantiated from here /usr/include/c++/4.3/bits/stl_algobase.h:396: error: no matching function for call to ‘std::__copy_move<false, true, std::random_access_iterator_tag>::__copy_m(const int*&, const int*&, const int*&)’ Please tell me what I am doing wrong here and what is the correct way to achieve the kind of higher order polymorphism I want. Thanks.

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  • why unsigned int 0xFFFFFFFF is equal to int -1?

    - by conejoroy
    perhaps it's a very stupid question but I'm having a hard time figuring this out =) in C or C++ it is said that the maximum number a size_t (an unsigned int data type) can hold is the same as casting -1 to that data type. for example see http://stackoverflow.com/questions/1420982/invalid-value-for-sizet Why?? I'm confused.. I mean, (talking about 32 bit ints) AFAIK the most significant bit holds the sign in a signed data type (that is, bit 0x80000000 to form a negative number). then, 1 is 0x00000001.. 0x7FFFFFFFF is the greatest positive number a int data type can hold. then, AFAIK the binary representation of -1 int should be 0x80000001 (perhaps I'm wrong). why/how this binary value is converted to anything completely different (0xFFFFFFFF) when casting ints to unsigned?? or.. how is it possible to form a binary -1 out of 0xFFFFFFFF? I have no doubt that in C: ((unsigned int)-1) == 0xFFFFFFFF or ((int)0xFFFFFFFF) == -1 is equally true than 1 + 1 == 2, I'm just wondering why. thanks!

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  • Using STL/Boost to initialize a hard-coded set<vector<int> >

    - by Hooked
    Like this question already asked, I'd like to initialize a container using STL where the elements are hard-coded in the cleanest manner possible. In this case, the elements are a doubly nested container: set<vector<int> > A; And I'd like (for example) to put the following values in: A = [[0,0,1],[0,1,0],[1,0,0],[0,0,0]]; C++0x fine, using g++ 4.4.1. STL is preferable as I don't use Boost for any other parts of the code (though I wouldn't mind an example with it!).

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  • Looking for a reporting tool that will allow vector graphics in output file (PDF)

    - by Richard West
    I have been tasked with evaluating our current system that we use for creating and outputing reports. Currently we are using Crystal Reports ver 8, (I know that this is and old version.), which has a custom commandline app that we wrote in C# to execute the report for a given parameter passed through the command line. We like Crystal becuase it's easy to setup and design the report. It's also easy to print and create a PDF file from crystal using our custom commandline program. One of the problems/complaints that we have is that Crystal does does not appear to have a method that will allow us to create a PDF file with a vector images, such as our company logo. Crystal Reports always converts an image into a bitmap. When the PDF is printed, the results are less than flattering, and the PDF file size is increased. Does anyone have any recomendadtions for a reporting product that we should consider?

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  • STL Vectors, pointers and classes

    - by anubis9
    Hey! Let's say i have 2 classes: class Class1 { public: std::vector<CustomClass3*> mVec; public: Class1(); ~Class1() { //iterate over all the members of the vector and delete the objects } }; class InitializerClass2 { private: Class1 * mPtrToClass1; public: InitializerClass2(); void Initialize() { mPtrToClass1->mVec.push_back(new CustomClass3(bla bla parameters)); } }; Will this work? Or the memory allocated in the InitializerClass2::Initialize() method might get corrupted after the method terminates? Thanks!

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  • Find the closest vector

    - by Alexey Lebedev
    Hello! Recently I wrote the algorithm to quantize an RGB image. Every pixel is represented by an (R,G,B) vector, and quantization codebook is a couple of 3-dimensional vectors. Every pixel of the image needs to be mapped to (say, "replaced by") the codebook pixel closest in terms of euclidean distance (more exactly, squared euclidean). I did it as follows: class EuclideanMetric(DistanceMetric): def __call__(self, x, y): d = x - y return sqrt(sum(d * d, -1)) class Quantizer(object): def __init__(self, codebook, distanceMetric = EuclideanMetric()): self._codebook = codebook self._distMetric = distanceMetric def quantize(self, imageArray): quantizedRaster = zeros(imageArray.shape) X = quantizedRaster.shape[0] Y = quantizedRaster.shape[1] for i in xrange(0, X): print i for j in xrange(0, Y): dist = self._distMetric(imageArray[i,j], self._codebook) code = argmin(dist) quantizedRaster[i,j] = self._codebook[code] return quantizedRaster ...and it works awfully, almost 800 seconds on my Pentium Core Duo 2.2 GHz, 4 Gigs of memory and an image of 2600*2700 pixels:( Is there a way to somewhat optimize this? Maybe the other algorithm or some Python-specific optimizations.

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  • R: Using sapply on vector of POSIXct

    - by Chris
    I have what may be a very simple question. I want to process a column of POSIXct objects from a dataframe and generate a vector of datetime strings. I tried to use the following sapply call dt <- sapply(df$datetime, function(x) format(x,"%Y-%m-%dT%H:%M:%S")) but to no avail. I keep getting the following error Error in prettyNum(.Internal(format(x, trim, digits, nsmall, width, 3L, : invalid 'trim' argument When I apply this function to a single POSIXct object from the column, I have no problem. So I'm stumped at the moment about what the problem is. Do I need to do something special with POSIXct objects?

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  • extract data from an array without using loop in R

    - by Manolo
    I have a vector v with row positions: v<-c(10,3,100,50,...) with those positions I want to extract elements of a matrix, having a column fixed, for example lets suppose my column number is 2, so I am doing: data<-c() data<-c(matrix[[v]][[2]]) matrix has the data in the following format: [[34]] [1] "200_s_at" "4853" "1910" "3554" "2658" So for example, I want to extract from the row 342 the value 1910 only, column 2, and do the same with the next rows but I got an error when I want to do that, is it possible to do it directly? or should I have a loop that read one by one the positions in v and fill the data vector like: #algorithm for i<-1 to length(v) pos<-v[i] data[[i]]<-c(matriz[[pos]][[2]]) next i Thanks

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  • add several variables to dataframe, based on vector

    - by Andreas
    I am sure this is easy - but I can't figure it out right now. Basically: I have a long vector of variables: names <- c("first","second", "third") I have some data, and I now need to add the variables. I could do: data$first <- NA But since I have a long list, and I would like an automated solution. This doesn't work. for (i in 1:length(names)) (paste("data$", names[i],sep="") <- NA) The reason I want this, is that I need to vertically merge to dataframes, where one doesn't have all the variables it should have. Thanks in advance

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  • How do I force my std::map to deallocate memory used?

    - by monkeyking
    I'm using a std::map, and I can't seem to free the memory back to the OS. It looks like, int main(){ aMap m; while(keepGoing){ while(fillUpMap){ //populate m } doWhatIwantWithMap(m); m.clear(); //flush some buffered values into map for next iteration flushIntoMap(m); } } Each (fillUpmap) allocates around 1gig, so I'm very much interested in getting this back to my system before it eats up all my memory. Ive experienced the same with std::vector, but there I could force it to free by doing a swap with an empty std::vector. This doesn't work with map. When I use valgrind it says that all memory is freed, so its not a problem with a leak, since everything is cleared up nicely after a run.

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  • Stack Overflow Accessing Large Vector

    - by cam
    I'm getting a stack overflow on the first iteration of this for loop for (int q = 0; q < SIZEN; q++) { cout<<nList[q]<<" "; } nList is a vector of type int with 376 items. The size of nList depends on a constant defined in the program. The program works for every value up to 376, then after 376 it stops working. Any thoughts?

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  • Can't modify XNA Vector components

    - by Matt H
    I have a class called Sprite, and ballSprite is an instance of that class. Sprite has a Vector2 property called Position. I'm trying to increment the Vector's X component like so: ballSprite.Position.X++; but it causes this error: Cannot modify the return value of 'WindowsGame1.Sprite.Position' because it is not a variable Is it not possible to set components like this? The tooltip for the X and Y fields says "Get or set ..." so I can't see why this isn't working.

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  • Normal vector of a face loaded from an FBX model during collision?

    - by Corey Ogburn
    I'm loading a simple 6 sided cube from a UV-mapped FBX model and I'm using a BoundingBox to test for collisions. Once I determine there's a collision, I want to use the normal vector of the collided surface to correct the movement of whatever collided with the cube. I suppose this is a two-part question: 1) How can I determine which face of the cube was collided with in a collision? 2) How can I get the normal vector of that surface?

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  • Get svn revision without an appropriate svn binary installed

    - by Sridhar Ratnakumar
    For some reason, we can't update the SVN in some build machines. Installed svn version is 1.3.x. But Hudson slave used 1.6 to create a checkout. This means we can't run "svn info" on those checkouts: $ svnversion subversion/libsvn_wc/questions.c:110: (apr_err=155021) svn: This client is too old to work with working copy '.'; please get a newer Subversion client $ svn info subversion/libsvn_wc/questions.c:110: (apr_err=155021) svn: This client is too old to work with working copy '.'; please get a newer Subversion client $ My question, is there a way to access the revision number without having to invoking the svn binary? You know, like trying to look into the .svn/ directory? Assume that the checkout is using latest svn version (1.6).

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  • Packing a long binary integer in Ruby

    - by user1056142
    I'm trying to send a very long binary integer over UDP (on the order of 200 bits). When I try to use Array's pack method, it complains the string I'm trying to convert is too large. Am I going about this the wrong way? ruby-1.8.7-p352 :003 > [0b1101001010101101111010100101010011010101010110010101010101010010010101001010101010101011101010101010101111010101010101010101].pack('i') RangeError: bignum too big to convert into `unsigned long' from (irb):3:in `pack' from (irb):3 This number is supposed to represent a DNS query packet (this is for a homework assignment; we're not allowed to use any DNS libraries).

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  • Lucene Error While Reading binary block : java.io.EOFException

    - by tushar Khairnar
    Hi, I am getting java.io.EOFException while reading a binary block from lucene index. I am storing java object as byte-array in lucene index field and reading it when hit occurs. Here is stack trace : Caused by: java.io.EOFException at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2281) at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2750) at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:780) at java.io.ObjectInputStream.(ObjectInputStream.java:280) at org.terracotta.modules.searchable.util.SerializationUtil$OIS.(SerializationUtil.java:20) I have some background threads which write into index. But i buffer them and then write them at once like 1000. Occasionally I also issue optimize() on index. When I write, I am re-opening IndexReader. Does this is happening because of IndexReader re-opening call? Thanks. Regards Tushar

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  • Using boost::iostreams to parse a binary file byte by byte

    - by Zsol
    So I would like to parse a binary file and extract some data from it. The problem I am facing with this is that I need to convert a stream of chars to a stream of unsigned chars. Reading the boost documentation, it seems that boost::iostreams::code_converter should be the solution for this, so I tried this: typedef unsigned char uint8_t; typedef boost::iostreams::stream<boost::iostreams::code_converter< boost::iostreams::basic_array_source<uint8_t> >, std::codecvt<uint8_t, char, std::mbstate_t> > array_stream; The idea was to specify a codecvt with InternalType=uint8_t and ExternalType=char. Unfortunately this does not compile. So the question is: how do I convert a stream of chars to a stream of uint8_ts?

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  • Makefiles - Compile all .cpp files in src/ to .o's in obj/, then link to binary in /

    - by Austin Hyde
    So, my project directory looks like this: /project Makefile main /src main.cpp foo.cpp foo.h bar.cpp bar.h /obj main.o foo.o bar.o What I would like my makefile to do would be to compile all .cpp files in the /src folder to .o files in the /obj folder, then link all the .o files in /obj into the output binary in the root folder /project. The problem is, I have next to no experience with Makefiles, and am not really sure what to search for to accomplish this. Also, is this a "good" way to do this, or is there a more standard approach to what I'm trying to do?

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  • Xcode is not building the Binary

    - by Stephen Furlani
    Hello, Xcode is doing something bizzare which I at one point in time fixed but now for the life of me I can't figure out what's wrong. Xcode is building my project fine - no errors on a clean-all build. All my product names and info.plists agree, all the settings appear to be correct. I've only got the one build configuration (I always delete all of them except when I got to actually release something - waay to many invisible problems with these things). Except that it is not generating binaries for my code. Eh wot? I have recently checked the code out on a new computer, and I checked all the paths and everything exists where it should. any help is appreciated. It is not throwing any errors and neither the binary for the .app nor the .plugin (project.app/Contents/MacOS/THERE IS NOTHING HERE). Thanks!!! -Stephen

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  • Implementing a linear, binary SVM (support vector machine)

    - by static_rtti
    I want to implement a simple SVM classifier, in the case of high-dimensional binary data (text), for which I think a simple linear SVM is best. The reason for implementing it myself is basically that I want to learn how it works, so using a library is not what I want. The problem is that most tutorials go up to an equation that can be solved as a "quadratic problem", but they never show an actual algorithm! So could you point me either to a very simple implementation I could study, or (better) to a tutorial that goes all the way to the implementation details? Thanks a lot!

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  • Infix to Postfix and unary/binary operators

    - by Jaapjan
    I have a piece of code that converts an infix expression to an expression tree in memory. This works just fine. There's just one small trouble. I just connect work out how to involve the unary operators correctly (the right associative ones). With the following infix expression : +1 + +2 - -3 - -4 I would expect an RPN of: 1+2++3-4-- Yet, none of the online infix-post converters I can find handle this example in the way I would expect. Does anyone have a clear explanation of handling right associative operators, specifically the binary ones that can be mistaken for the unary ones?

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  • binary file to string

    - by andrew
    i'm trying to read a binary file (for example an executable) into a string, then write it back FileStream fs = new FileStream("C:\\tvin.exe", FileMode.Open); BinaryReader br = new BinaryReader(fs); byte[] bin = br.ReadBytes(Convert.ToInt32(fs.Length)); System.Text.Encoding enc = System.Text.Encoding.ASCII; string myString = enc.GetString(bin); fs.Close(); br.Close(); System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding(); byte[] rebin = encoding.GetBytes(myString); FileStream fs2 = new FileStream("C:\\tvout.exe", FileMode.Create); BinaryWriter bw = new BinaryWriter(fs2); bw.Write(rebin); fs2.Close(); bw.Close(); this does not work (the result has exactly the same size in bytes but can't run) if i do bw.Write(bin) the result is ok, but i must save it to a string

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  • Amazon SQS invalid binary character in message body

    - by letronje
    I have a web app that sends messages to an Amazon SQS Queue. Amazon sqs lib throws a 'AmazonSQSException' since the message contained invalid binary character. The message is the referrer obtained from an incoming http request. This is what it looks like: http://ads.vrx.adbrite.com/adserver/display_iab_ads.php?sid=1220459&title_color=0000FF&text_color=000000&background_color=FFFFFF&border_color=CCCCCC&url_color=008000&newwin=0&zs=3330305f323530&width=300&height=250&url=http%3A%2F%2Funblockorkutproxy.com%2Fsearch.php%2FOi8vZG93%2FbmxvYWRz%2FLnppZGR1%2FLmNvbS9k%2Fb3dubG9h%2FZGZpbGUv%2FNTY5MTQ3%2FNi9NeUN1%2FdGVHaXJs%2FZnJpZW5k%2FWmFoaXJh%2FLndtdi5o%2FdG1s%2Fb0%2F^Fô}úÃ<99ë)j Looks like the characters in bold are the invalid characters. Is there an easy way to filter out characters characters that are not accepted by amazon ? Here are the characters allowed by amazon in message body. I am not sure what regex i should use to replace invalid characters by ''

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  • C# Binary File Compare

    - by Simon Farrow
    I'm in a situation where I want to compare two binary files. One of them is already stored on the server with a pre-calculated Crc32 in the database from when I stored it originally. I know that if the Crc is different then the files are definitely different. However, if the Crc is the same I don't know that the files are. So what I'm looking for is a nice efficient way of comparing the two streams on from the posted file and one from the file system. I'm not an expert on streams but I'm well aware that I could easily shoot myself in the foot here as far as memory usage is concerned. Any help is greatly appreciated.

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