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Search found 69 results on 3 pages for 'williamkf'.

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• Why is ::connect() returning EHOSTUNREACH when ssh works fine?

  - by WilliamKF

  I am calling ::connect() in my application and it works fine in general, however, between two particular machines, from one to the other, it fails with EHOSTUNREACH which means "No route to host." If I can ssh with no problems, what might be going on here that ::connect() always fails for this particular machine pair?

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• Can a std::string contain embedded nulls?

  - by WilliamKF

  For regular C strings, a NULL signifies the end of data. What about std::string, can I have a string with embedded NULLS?

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• Why do I get this strange output behavior?

  - by WilliamKF

  I have the following program test.cc: #include <iostream> unsigned char bogus1[] = { // Changing # of periods (0x2e) changes output after periods. 0x2e, 0x2e, 0x2e, 0x2e }; unsigned int bogus2 = 1816; // Changing this value changes output. int main() { std::clog << bogus1; } I build it with: g++ -g -c -o test.o test.cc; g++ -static-libgcc -o test test.o Using g++ version 3.4.6 I run it through valgrind and nothing is reported wrong. However the output has two extra control characters and looks like this: .... Thats a control-X and a control-G at the end. If you change the value of bogus2 you get different control characters. If you change the number of periods in the array the issue goes away or changes. I suspect it is a memory corruption bug in the compiler or iostream package. What is going on here?

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• How to disable Qt dialog default button changing with tab navigation

  - by WilliamKF

  In Qt 4, by default, tabbing through a dialog changes the default button to be the button tabbed to. This makes tabbing look a bit ugly and distracting as extra redraws take place during tab navigation which distract from point of user focus. Is there a way to disable this Qt functionality and leave the default button unmodified by tab navigation?

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• How to hide keys in application?

  - by WilliamKF

  I have a C++ client/server application where the client and server are my executable. Each time a connection is made between the client and server, I generate a new encryption key for that session and I wish to transmit this session key and encrypt this session key using a static key that is built into both the client and server. However, running strings on my executable reveals the static key. How can I hide the embedded static key in my client and server application so that they are not easily extracted and thus allowing someone to decode my session key.

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• How to do case insensitve comare using std::string?

  - by WilliamKF

  How do I do a case insensitive string compare using std::string (i.e. strcasecmp())?

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• How to automate detection of out of order tab navigation in Qt dialogs?

  - by WilliamKF

  Typically, a dialog wishes to have tab navigation proceed in an orderly fashion through a dialog that roughly corresponds to the order of reading a book. When new fields are added to a dialog by engineers on a team, the new widgets can often not be inserted in tab correct order. Can anyone think of a way to automate the detection of out of tab navigation order widgets within a dialog?

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• Way to get unsigned char into a std::string without reinterpret_cast?

  - by WilliamKF

  I have an unsigned char array that I need in a std::string, but my current way uses reinterpret_cast which I would like to avoid. Is there a cleaner way to do this? unsigned char my_txt[] = { 0x52, 0x5f, 0x73, 0x68, 0x7e, 0x29, 0x33, 0x74, 0x74, 0x73, 0x72, 0x55 } unsigned int my_txt_len = 12; std::string my_std_string(reinterpret_cast<const char *>(my_txt), my_txt_len);

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• How can I get the contents of a file at build time into my C++ string?

  - by WilliamKF

  I have a file I am compiling in C++ in which I wish to have a string whose value is the contents of a file at the time of compilation. In other words, I'd like to #include the file but have that be inside double quotes. How can I do this in C++? Now what if that file contains double quotes as part of its text, how do I get those escaped?

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• How can I capture the current directory as an absolute pathname in a make variable?

  - by WilliamKF

  I'd like to get the current directory during a GNUmake file run put into a make variable. What is the syntax to do this? Something like this? DIR := $(PWD)

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• How to figure out why ssh session does not exit sometimes?

  - by WilliamKF

  I have a C++ application that uses ssh to summon a connection to the server. I find that sometimes the ssh session is left lying around long after the command to summon the server has exited. Looking at the Centos4 man page for ssh I see the following: The session terminates when the command or shell on the remote machine exits and all X11 and TCP/IP connections have been closed. The exit status of the remote program is returned as the exit status of ssh. I see that the command has exited, so I imagine not all the X11 and TCP/IP connections have been closed. How can I figure out which of these ssh is waiting for so that I can fix my summon command's C++ application to clean up whatever is being left behind that keeps the ssh open. I wonder why this failure only occurs some of the time and not on every invocation? It seems to occur approximately 50% of the time. What could my C++ application be leaving around to trigger this?

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• When encrypting data that is not an even multiple of the block size do I have to send a complete las

  - by WilliamKF

  If I am using a block cipher such as AES which has a block size of 128 bits, what do I do if my data is not an even multiple of 128 bits? I am working with packets of data and do not want to change the size of my packet when encrypting it, yet my data is not an even multiple of 128? Does the AES block cipher allow handling of a final block that is short without changing the size of my message once encrypted?

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• Can my thread help the OS decide when to context switch it out?

  - by WilliamKF

  I am working on a threaded application on Linux in C++ which attempts to be real time, doing an action on a heartbeat, or as close to it as possible. In practice, I find the OS is swapping out my thread and causing delays of up to a tenth of a second while it is switched out, causing the heartbeat to be irregular. Is there a way my thread can hint to the OS that now is a good time to context switch it out? I could make this call right after doing a heartbeat, and thus minimize the delay due to an ill timed context switch.

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• Are tr1 headers available for gcc v3.4.6?

  - by WilliamKF

  Are tr1 headers available for g++ v3.4.6? If so, how can I locate them at compile time. The following is failing to compile: #include <tr1/memory> With the following error: myModule.h:20:24: tr1/memory: No such file or directory Do I need to move to a later compiler or do I have the headers somewhere?

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• How to push_back without operator=() for const members?

  - by WilliamKF

  How to push_back() to a C++ std::vector without using operator=() for which the default definition violates having const members? struct Item { Item(int value) : _value(value) { } const int _value; } vector<Item> items; items.push_back(Item(3)); I'd like to keep the _value const since it should not change after the object is constructed, so the question is how do I initialize my vector with elements without invoking operator=()?

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• How to search a file for a pattern and get a new file from the match point to end of file?

  - by WilliamKF

  I need to take a file and find the first occurrence of a literal string pattern as a complete line of the file: Acknowledgments: And then I wish to create a new file from the line of match all the way to the end of the file. I expect perl is a good way to do this, but I'm not much of a perl person, alternatively maybe sed is a good way? Please suggest a simple way to reliably accomplish this in Unix.

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• How to multi-thread this?

  - by WilliamKF

  I wish to have two threads. The first thread1 occasionally calls the following pseudo function: void waitForThread2() { if (thread2 is not idle) { return; } notifyThread2IamReady(); while (thread2IsExclusive) { } } The second thread2 is forever in the following pseudo loop: for (;;) { Notify thread1 I am idle. while (!thread1IsReady()) { } Notify thread1 I am exclusive. Do some work while thread1 is blocked. Notify thread1 I am busy. Do some work in parallel with thread1. } What is the best way to write this such that both thread1 and thread2 are kept as busy as possible on a machine with multiple cores. I would like to avoid long delays between notification in one thread and detection by the other. I tried using pthread condition variables but found the delay between thread2 doing 'notify thread1 I am busy' and the loop in waitForThread2() on thear2IsExclusive() can be up to almost one second delay. I then tried using a volatile sig_atomic_t shared variable to control the same, but something is going wrong, so I must not be doing it correctly.

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• Is there a way to introspect an array's size?

  - by WilliamKF

  In C++ given an array like this: unsigned char bogus1[] = { 0x2e, 0x2e, 0x2e, 0x2e }; Is there a way to introspect bogus1 to find out is is four characters long?

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• From an established ssh connection, what is a good way to encrypt messages on the side?

  - by WilliamKF

  If I have a connection between a client and a server using ssh. What is a good way to encrypt data sent outside the ssh connection for sending large amounts of data quickly and securely? I can use the ssh connection to set up the terms of the communication, sharing keys etc, but then will do the communication on the side.

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