C programming language – Karl Brodowsky's IT-Blog

Exceptions to implement Program Logic

Sometimes it is conveniant to use exceptions for implementing the regular program logic. Assuming we want to find some data and then process them. When no data is found, this step can be skipped, because there is nothing to do. So we could program something like this: public Data readData(Param param) { Data data = db.read(param); if (data.isEmpty()) { throw new NotFoundException(„nothing found“); } return data; } public ProcessedData doWork(Param param) { …

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Unicode and C

It is a common practice in C to use arrays of char as strings. The 0 is used as end marker. The whole thing was created like that in the 1970s and at that time it was kind of cool to get away with one less language feature and to express it in terms of …

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Meaningless Whitespace in Textfiles

We use different file formats that are more or less tolerant to certain changes. Most well known is white space in text files. In some programming languages white space (space, newline, carriage return, form feed, tabulator, vertical tab) has no meaning, as long as any whitespace is present. Examples for this are Java, Perl, Lisp …

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Loops with unknown nesting depth

We often encounter nested loops, like for (i = 0; i < n; i++) { for (j = 0; j < m; j++) { doSomething(i, j); } } This can be nested to a few more levels without too much pain, as long as we observe that the number of iterations for each level need …

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How to create ISO Date String

It is a more and more common task that we need to have a date or maybe date with time as String. There are two reasonable ways to do this: * We may want the date formatted in the users Locale, whatever that is. * We want to use a generic date format, that is …

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Conversion of ASCII-graphics to PNG or JPG

Images are usually some obscure binary files. Their most common formats, PNG, SVG, JPEG and GIF are well documented and supported by many software tools. Libraries and APIs exist for accessing these formats, but also a phantastic free interactive software like Gimp. The compression rate that can reasonably be achieved when using these format is …

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System Programming on Linux and MS-Windows

Quite honestly I admit that I really love the Posix-APIs for system programming and even some Linux specific extensions to it. I/O, Locking, Semaphores, Shared Memory, Message Queues, Signals, named and anonymous pipes, Unix Domain Sockets, TCP/IP programming, Terminal I/O, pthreads and a lot more are very powerful and fun to program. I do discover …

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Find the next entry in a sequence

In Facebook, Xing, Google+, Vk.com, Linkedin and other of these social media networks we are often encountered with a trivial question like this: 1->2 2->8 3->18 4->32 5->50 6->72 7->? There are some easy patterns. Either it is some polynomial formula or some trick with the digits. But the point is, that any such sequence …

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How to recover the Carry Bit

As frequent readers might have observed, I like the concept of the Carry Bit as it allows for efficient implementations of long integer arithmetic, which I would like to use as default integer type for most application development. And unfortunately such facilities are not available in high level languages like C and Java. But it …

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Shift- and Rotation Functions

Deutsch In a comment to Carry Bit: How does it work the question about shift and rotation functions has been asked. Which exist and how they work exactly depends off course on the CPU architecture, but I will try to give a high level overview anyway. The following aspects have to be considered: 8, 16, …

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