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Funny Drawing with 'C++' 'FLEX' and a Bison

Published Flex Bison C++ Example 0.1.4

Posted on 2009-09-05 10:40 by Timo Bingmann at Permlink with 0 Comments. Tags: flex-bison-cpp-example parsing c++ code-example

Released a minor updated source code version for Flex Bison C++ Example. The example source code is released into the public domain or, at your option, under the Do What The Fuck You Want To Public License (WTFPL).

This minor bugfix release fixes up two simple compilation issues with the newest bison version 2.4.1.

For more information and the download package see the Flex Bison C++ Example web page.


Thumbnail of the CryptoTE screencast

Experiences Producing a Screencast on Linux for CryptoTE

Posted on 2009-08-17 11:25 by Timo Bingmann at Permlink with 0 Comments. Tags: linux vncrec

While publishing screenshots for CryptoTE (nice cross-platform text editor with integrated cryptography) the idea of making a short tutorial screencast came up. A screencast is basically a video made directly from the computer screen with no camera involved. Usually speech comments are added to create a sort of impromptu screen presentation. Thus I could show off the cool features of CryptoTE, and people could see what the program is about without installing it.

So far the cool and very trendy idea, now for sorting out the technical difficulties in making such a video. In theory a screencast video should be well compressible with a lossless codec. Unresized screenshots in full-resolution are also better compressed using the lossless PNG format than with JPEG, the PNG files are much smaller and show no blurry edges. Similarly screencasts, being only a sequence of full-resolution, losslessly recorded screenshots with some little mouse-movement, should be compressed losslessly.

On the digital inspiration blog I found a detailed "Screencasting Software Guide - Review of Desktop Screen Recording Tools" for all platforms. However, because my primary operating system is Linux (and since I also wanted to show that in the screencast), the range of tools that actually work is very limited.

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[150x150] CryptoTE Icon

Published CryptoTE 0.5.390

Posted on 2009-08-08 11:25 by Timo Bingmann at Permlink with 1 Comments. Tags: cryptote c++ cryptography

After almost one year of personally testing the program, I decided to publicly released the first version of CryptoTE v0.5.390. One year in the making, CryptoTE is a very useful little text-editor with integrated cryptography. The name stands for CRYPTOgraphy Text Editor and it transparently encrypts text files storing them into secure containers. The program incorporates the popular editing component Scintilla and makes heavy use of wxWidgets.

Screenshot of CryptoTE on Linux

For more information, the source code and binaries for various platforms see the CryptoTE web page.


Thumbnail of three slides from completion talk

Completion Talk on My Diploma Thesis / Abschlussvortrag zu meiner Diplomarbeit

Posted on 2009-06-26 13:30 by Timo Bingmann at Permlink with 0 Comments. Tags: ns-3 talk university

Today I gave the final completion presentation for my diploma thesis. The talk showcased a selection of results published in the thesis. Results and experiments are only sketched, as all further detailed information can be found in the thesis PDF itself.

The talk contains side-by-side comparison plots of feature enhancements made to ns-3 and verifications thereof using ns-2. Furthermore, the EDCA extensions implemented in ns-3 are tested against analytically calculated reference values. In the end, a speed test comparison is done between ns-2 and ns-3, which uses the implemented classes to run an experiment scenario identically on both simulators.

The slides are available as PDFs in following two variants:

Presentation Slides (including appendix): ns-3-wifiex-completion-slides.pdf 1455 kB
Presentation Slides (two per page, excluding appendix): ns-3-wifiex-completion-slides-1x2.pdf 1040 kB

Here the table of contents:

  1. Thesis Objectives
  2. Enhancements
    1. Propagation Loss Models
    2. Reception Criteria
    3. Frame Capture Effect
    4. EDCA Implementation
  3. Speed Comparison
  4. Conclusion
  5. Appendix
    1. Enlarged Plots and Figures
      1. Propagation Loss Models
      2. Reception Criteria
      3. Frame Capture Effect
      4. EDCA Implementation

Thumbnail of front page of thesis

Finished My Diploma Thesis on 802.11 in ns-3

Posted on 2009-04-29 17:30 by Timo Bingmann at Permlink with 2 Comments. Tags: ns-3 university

After a very exhausting last week with lots of writing and little sleep, my diploma thesis is finally complete. The thesis is on enhancements to the 802.11 model and EDCA (enhanced distributed coordination access) QoS (quality of service) extensions in the new network simulator ns-3.

The thesis is written in English and a copy of the abstract and table of contents is located below. There is also a Zusammenfassung in German.

It is available as PDF in different variants:

Standard PDF version: thesis-bingmann-ns-3-wifi.pdf (3469 kB)
Better printable version (with black links): in RGB color with binding offset (3482 kB)
in CMYK color with binding offset (3381 kB)

Beyond the thesis itself, an extra page contains additional material like the source code, plot results and a snapshot of ns-3 at that time.

Shortened Table of Contents

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Thumbnail of two slides in halftime talk

Halftime Talk on My Diploma Thesis / Zwischenvortrag zu meiner Diplomarbeit

Posted on 2009-02-06 17:30 by Timo Bingmann at Permlink with 2 Comments. Tags: ns-3 talk university

For the last three months I have been working intensely on my diploma thesis. The thesis will be about 802.11 enhancements and EDCA QoS extensions in the new network simulator ns-3.

Today I gave my halftime presentation about the current status of my efforts. The talk is composed of a short introduction into ns-3, followed by a detailed discussion of WLAN packet reception criteria and finishes with a review of DCF and how EDCA extends it.

Be warned: many slides are not all self-explanatory and therefore less suitable as a casual introduction into the topics. They are slides meant for presentation.

The slides are available as PDFs in following three variants:

Presentation Slides (including "Animations"): ns-3-wifiex-halftime-slides.pdf 1076 kB
Handout Slides (one per page): ns-3-wifiex-halftime-handout.pdf 1036 kB
Handout Slides (four per page): ns-3-wifiex-halftime-handout-2x2.pdf 1028 kB

Here the table of contents:

  1. ns-3 Basics
    1. Introduction
    2. Showcase: Design Patterns
    3. Current State
  2. Wifi in ns-3
    1. State of 802.11
    2. PHY Layer
    3. Signals, Noise and Interference
    4. Short Recapitulation of DCF
    5. QoS with EDCA
  3. Conclusion

Funny Drawing with 'C++' 'FLEX' and a Bison

Published Flex Bison C++ Example 0.1.3

Posted on 2008-10-23 11:25 by Timo Bingmann at Permlink with 0 Comments. Tags: flex-bison-cpp-example c++ code-example parsing

Released yet another updated source code package for Flex Bison C++ Example. The example source code is released into the public domain or, at your option, under the Do What The Fuck You Want To Public License (WTFPL).

This bugfix release solves a subtle, severe bug, which rendered the template code useless. Even the example exprtext program segfaulted with any expression.

Corrected a very subtle bug with the newly introduced virtual yywrap() function in the FlexLexer class. Depending on how the header was included, the class contained the virtual yywrap() function or not. These differing class declarations lead to very strange NULL pointer exceptions, because the different compiled objects assume different class memory layouts. Ultimately the exprtest program always segfaulted.

For more information and the download package see the Flex Bison C++ Example web page.


Small drawing of a B+ tree

Update Release of STX B+ Tree 0.8.3

Posted on 2008-09-07 18:31 by Timo Bingmann at Permlink with 0 Comments. Tags: c++ stx-btree

Released another updated version 0.8.3 of the STX B+ Tree C++ Template Classes package. The updated release fixes up issues with the root node == NULL when the tree is initially empty.

Fixed crash when running verify() on an empty btree object. Now the root node is freed when the last item is removed. Also fixed crash when attempting to copy an empty btree or when trying to remove a non-existing item from an empty btree.

Also enhancing the speedtest to test the hash table container implementation from __gnu_cxx. Extending tests by another set of runs measuring only the find/lookup functions. See the speed results web page for more information.

The updated source code package is available for download from this webpage.

Some compiled binaries of wxBTreeDemo for Win32 and Linux are available on the demo download page.

As before, the updated main B+ tree implementation can be found in doxygen stx/btree.h or with plain text comments stx/btree.h.


Instacode coloring of stacktrace

C++ Code Snippet - Print Stack Backtrace Programmatically with Demangled Function Names

Posted on 2008-09-01 22:30 by Timo Bingmann at Permlink with 34 Comments. Tags: c++ code-snippet coding tricks frontpage

Yesterday I was tasked to analyzed an inner function of a reasonably complex software package. The inner function was called thousands of times from many different parts of the program, a simple counter print-out showed that. However I was interested in which execution paths reach this inner function and how often the different parts access the function.

My straight-forward idea was to dump a stack backtrace each time the inner function is called, similar to the one printed by a debugger. However I needed some code snippet to dump the stack backtrace programmatically, without using gdb to halt the program each time.

Stack backtraces can be saved with backtrace(3), resolved into symbolic names using backtrace_symbols(3) and printed using backtrace_symbols_fd(3). These functions are well documented and fairly easy to use.

However I was debugging a C++ program, which made heavy use of templates and classes. C++ symbols names (including namespace, class and parameters) are mangled by the compiler into plain text symbols: e.g. the function N::A<int>::B::func(int) becomes the symbol _ZN1N1AIiE1B4funcEi. This makes the standard backtrace output very unreadable for C++ programs.

To demangle these strings the GNU libstdc++ library (integrated into the GNU Compiler Collection) provides a function called __cxa_demangle(). Combined with backtrace(3) a pretty stack backtrace can be outputted. The demangling function only works for programs compiled with g++.

The following header file contains a function print_stacktrace(), which uses backtrace(3), backtrace_symbols(3) and __cxa_demangle() to print a readable C++ stack backtrace.

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Small drawing of a B+ tree

Update Release of STX B+ Tree 0.8.2

Posted on 2008-08-13 16:48 by Timo Bingmann at Permlink with 0 Comments. Tags: c++ stx-btree

Released an updated version 0.8.2 of the STX B+ Tree C++ Template Classes package. The updated release fixes up all issues with iterators and one harmless bad-memory access.

The reverse_iterator classes of the B+ tree were completely reworked. Now they are real implementations and do not use STL magic. Both reverse_iterator and const_reverse_iterator should work as expected now. Added two large test cases for iterators. Enabled public default-constructors on iterators.

Also fixed a memory access bug which happens in erase_one_descend(): leaf->slotkey[leaf->slotuse - 1] if leaf-slotuse == 0. This doesn't have any other bad effect, because the case only occurs when leaf == root and then the resulting btree_update_lastkey message is never really processed. However it still is a bad-memory access.

The updated source code package including the wxBTreeDemo source is available for download from this webpage.

Some compiled binaries of wxBTreeDemo for Win32 and Linux are available on the demo download page.

As before, the updated main B+ tree implementation can be found in doxygen stx/btree.h or with plain text comments stx/btree.h.


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