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Search found 12 results on 1 pages for 'zxcvbnm'.

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• Anyone had any experience with *.pcap manipulation libs?

  - by zxcvbnm

  I'm using the SharpPcap + PacketDotNet libraries to process some .pcap files and came across a bug in the way the timestamps are calculated. Take this Timeval property, which is something along these lines: PosixTimeval Timeval { DateTime Date; ulong Seconds; ulong MicroSeconds; } The problem is as follows: Suppose you have a trace open in Wireshark with one of the packets with a timestamp of "0.002". Once you open it within one of your programs, it retrieves the packet and its Timeval is setup such that Seconds = 0 and MicroSeconds = 002 = 2. This is done under the hood, so there is no way to avoid it as far as I can tell. My question is if that problem is common to other libraries (and maybe all of them?) who manipulate the pcap file format, which I think are built around the same collection of c/c++ functions, or if this is a problem only with the ones I'm using.

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• Calculating Percentiles (Ruby).

  - by zxcvbnm

  My code is based on the methods described here and here. def fraction?(number) number - number.truncate end def percentile(param_array, percentage) another_array = param_array.to_a.sort r = percentage.to_f * (param_array.size.to_f - 1) + 1 if r <= 1 then return another_array[0] elsif r >= another_array.size then return another_array[another_array.size - 1] end ir = r.truncate another_array[ir] + fraction?((another_array[ir].to_f - another_array[ir - 1].to_f).abs) end Example usage: test_array = [95.1772, 95.1567, 95.1937, 95.1959, 95.1442, 95.061, 95.1591, 95.1195, 95.1065, 95.0925, 95.199, 95.1682] test_values = [0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0] test_values.each do |value| puts value.to_s + ": " + percentile(test_array, value).to_s end Output: 0.0: 95.061 0.1: 95.1205 0.2: 95.1325 0.3: 95.1689 0.4: 95.1692 0.5: 95.1615 0.6: 95.1773 0.7: 95.1862 0.8: 95.2102 0.9: 95.1981 1.0: 95.199 The problem here is that the 80th percentile is higher than the 90th and the 100th. However, as far as I can tell my implementation is as described, and it returns the right answer for the example given (0.9). Is there an error in my code I'm not seeing? Or is there a better way to do this?

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• Ruby: Is there a better way to iterate over multiple (big) files?

  - by zxcvbnm

  Here's what I'm doing (sorry for the variable names, I'm not using those in my code): File.open("out_file_1.txt", "w") do |out_1| File.open("out_file_2.txt", "w") do |out_2| File.open_and_process("in_file_1.txt", "r") do |in_1| File.open_and_process("in_file_2.txt", "r") do |in_2| while line_1 = in_1.gets do line_2 = in_2.gets #input files have the same number of lines #process data and output to files end end end end end The open_and_process method is just to open the file and close it once it's done. It's taken from the pickaxe book. Anyway, the main problem is that the code is nested too deeply. I can't load all the files' contents into memory, so I have to iterate line by line. Is there a better way to do this? Or at least prettify it?

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• Given a trace of packets, how would you group them into flows?

  - by zxcvbnm

  I've tried it these ways so far: 1) Make a hash with the source IP/port and destination IP/port as keys. Each position in the hash is a list of packets. The hash is then saved in a file, with each flow separated by some special characters/line. Problem: Not enough memory for large traces. 2) Make a hash with the same key as above, but only keep in memory the file handles. Each packet is then put into the hash[key] that points to the right file. Problems: Too many flows/files (~200k) and it might run out of memory as well. 3) Hash the source IP/port and destination IP/port, then put the info inside a file. The difference between 2 and 3 is that here the files are opened and closed for each operation, so I don't have to worry about running out of memory because I opened too many at the same time. Problems: WAY too slow, same number of files as 2 so also impractical. 4) Make a hash of the source IP/port pairs and then iterate over the whole trace for each flow. Take the packets that are part of that flow and place them into the output file. Problem: Suppose I have a 60 MB trace that has 200k flows. This way, I would process, say, a 60 MB file 200k times. Maybe removing the packets as I iterate would make it not so painful, but so far I'm not sure this would be a good solution. 5) Split them by IP source/destination and then create a single file for each one, separating the flows by special characters. Still too many files (+50k). Right now I'm using Ruby to do it, which might've been a bad idea, I guess. Currently I've filtered the traces with tshark so that they only have relevant info, so I can't really make them any smaller. I thought about loading everything in memory as described in 1) using C#/Java/C++, but I was wondering if there wouldn't be a better approach here, especially since I might also run out of memory later on even with a more efficient language if I have to use larger traces. In summary, the problem I'm facing is that I either have too many files or that I run out of memory. I've also tried searching for some tool to filter the info, but I don't think there is one. The ones I've found only return some statistics and wouldn't scan for every flow as I need.

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• Ruby: Is there a way to split a string only with the first x occurrencies?

  - by zxcvbnm

  For example, suppose I have this: 001, "john doe", "male", 37, "programmer", "likes dogs, women, and is lazy" The problem is that the line is only supposed to have 6 fields. But if I separate it with split I get more, due to the comma being used improperly to separate the fields. Right now I'm splitting everything, then when I get to the 5-th index onward I concatenate all the strings. But I was wondering if there was a split(",",6) or something along these lines.

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• Ruby: How can I have a Hash take multiple keys?

  - by zxcvbnm

  I'm taking 5 strings (protocol, source IP and port, destination IP and port) and using them to store some values in a hash. The problem is that if the IPs or ports are switched between source and destination, the key is supposed to be the same. If I was doing this in C#/Java/whatever I'd have to create a new class and overwrite the hashcode()/equals() methods, but that seems error prone from the little I've read about it and I was wondering if there would be a better alternative here.

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• Which book should I pick to improve my program designs/design patterns?

  - by zxcvbnm

  I want to learn about design patterns and from what I've seen the most recommended ones are the Gang of Four's Design Patterns and Head First Design Patterns. There are also language specific books, but I never see them recommended. I suppose it ties you to whatever strengths/weaknesses are inherent to each language, so not a good idea to learn design patterns in general. The Gang of Four's book is kinda old, so I'm wondering if there isn't a better alternative out today? I've heard the Heard First one isn't quite as good. But I'm not sure why, so it's really hard to pick either one. I've see some answers on this very site recommending both, but if I can only read one, which should I pick? I've been coding for 3+ years, though I've never had a good class on this subject. Also, would a book like Code Complete help me with this? One more thing: how often are these techniques supposed to be useful? For example, this question has me wondering if this stuff is worth the trouble. And please, tell me more than just "read x". I'd like to know why you're suggesting x.

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• C#: When should I use TryParse?

  - by zxcvbnm

  I understand it doesn't throw an Exception and because of that it might be sightly faster, but also, you're most likely using it to convert input to data you can use, so I don't think it's used so often to make that much of difference in terms of performance. Anyway, the examples I saw are all along the lines of an if/else block with TryParse, the else returning an error message. And to me, that's basically the same thing as using a try/catch block with the catch returning an error message. So, am I missing something? Is there a situation when this is actually useful?

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• C#: Why am I getting "the process cannot access the file * because it is being used by another proce

  - by zxcvbnm

  I'm trying to convert bmp files in a folder to jpg, then delete the old files. The code works fine, except it can't delete the bmp's. DirectoryInfo di = new DirectoryInfo(args[0]); FileInfo[] files = di.GetFiles("*.bmp"); foreach (FileInfo file in files) { string newFile = file.FullName.Replace("bmp", "jpg"); Bitmap bm = (Bitmap)Image.FromFile(file.FullName); bm.Save(newFile, ImageFormat.Jpeg); } for (int i = 0; i < files.Length; i++) files[i].Delete(); The files aren't being used by another program/process like the error indicates, so I'm assuming the problem is here. But to me the code seems fine, since I'm doing everything sequentially. This is all that there is to the program too, so the error can't be caused by code elsewhere.

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• WPF: Is VerticalAlignment inherited by nested containers?

  - by zxcvbnm

  I'd like to have the nested containers inherit that property, but when I set it in the outermost one I'm not sure if it's working. It either is working but I'm not getting the results I want, or maybe I'd have to set up a property somewhere for it to carry. Assuming that a) it is possible to do it and b) I'd have to change a property somewhere, would that have any side effects I should be aware of?

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• Ruby: Is it possible to have a for loop that increases more than one at a time?

  - by zxcvbnm

  For example: for(int i = 0; i < 100; i += 2) I could use a while loop or check if i % 2 == 0, but I was wondering if there wasn't a way to do it with the for loop. I could also use for(int i = 0; i < 50; i++) and multiply i by 2, but that doesn't seem right either. I'm just wondering if there is a simple, straightforward way to do it.

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• Search and get a line in Python

  - by omfgroflmao

  Is there a way to search, from a string, a line containing another string and retrieve the entire line? For example: string = qwertyuiop asdfghjkl zxcvbnm token qwerty asdfghjklñ retrieve_line("token") = "token qwerty"

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