## Coding Style |
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- **Indentation:** --- K&R only. |
- **Naming:** use small\_letters\_and\_underscore. Such names are much more |
readable. Same namging convention for class names, variables and functions. |
NeverUseUglyAndUnreadableCamelCasedCode. _Rationale_ -- readability. |
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Prefer to use STL conventions. For example, for cleanup operations use `clear()`, for finding something "find()" and |
so on. |
- **Polish/Hungarian notations** are not in CppCMS. No prefixes or suffixes like `iNumber` or `m_some_class_member`. |
- **Variable Names:** --- variables like `i`, `j`, `tmp` are perfrectly well to use inside functions, in loops. |
It is ok to use `def`, `tmp` perfixes and suffixes for member variables when they meaning something. |
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_Rationale:_ Linux Kernel Coding Style. |
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- **Class Members:** are ended with underscore `_` with exception of public structure members that do not have suffixes/prefixes. Rationale - Boost. |
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- **Tab Stops** --- Tab is 8, not 4, not 2 and defiantly not 5! Tab width=8 is like Pi=3.1415926535. Do not use something |
else. This is most compatible over different editors, it is standard, it should be used anywhere. It makes code more |
readable at 1:00am. |
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Do not replace tabs with spaces, all indentation should be done with tabs. |
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_Rationale:_ Linux Kernel Coding Style |
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- **Preprocessor Macros** --- should be CAPITAL\_CASED\_WITH\_UNDERSCORES. Always add `CPPCMS_` prefix to them. |
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## Keeping backward compatible ABI |
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TODO. |
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## General Coding Notes |
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### Exceptions |
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All code you write should be exception safe. Only functions that you may assume they never throw exceptions are POSIX API or 3rd party C libraries like libgcrypy or sqlite3. Even STL may throw exception. Assume that std::bad\_alloc may be thrown and handle it correctly. |
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Thus: |
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- Always use smart pointers. Prefer auto\_ptr over reference counting smart pointers: |
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1. It is faster and does not include ref-counting overheads |
2. All of them can be always created from auto\_ptr but not in other direction. |
3. It has move semantics that covers our requirements in most of cases: |
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For example |
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auto_ptr<my_class> my_func() |
{ |
auto_ptr<my_class> instance(new my_class); |
instance->do_something(); |
return instance; |
} |
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- Use std::vector instead of allocating `new some_class[N]`. |
- When using C API, that does not have destructors, put your code inside try-catch block and cleanup everything. |
- If you use C API in more then one place consider wrapping it with simple class or at least provide scoped destructor. See as an example posix\_mutex.h or fcntl\_mutex.h |
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### STL |
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Do not reinvent the wheel, use STL --- it is well document, well known, highly available library that does the job. Use it. |
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_Notes:_ |
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1. Always prefer std::vector to std::list --- it has better performance because it is cache friendly. |
2. Always prefer std:string for text storage. |
3. It is OK to return STL collections from functions, compiler know how to optimize them. |
4. Do not forget `swap()` function --- it can save lot's of unnecessary copies for you. For example: |
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vector<char> foo(); |
... |
void bar() |
{ |
vector<char> s; |
for(;;) { |
s.swap(foo()); |
// Not s=foo(); |
if(s.empty()) |
break; |
} |
} |
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Description: when you call `s=foo()` assignment operator is called that copies the value that `foo()` returned to `s` and then releases it. When you call `s.swap(foo())` the value in `s` is replaced by returned value and the old value in `s` is cleaned --- you saved copy of probably huge buffer, you operation is done in `O(1)`. |
5. If you have non-copyable class, you can store it in STL collection using reference counting pointer. |
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## Libraries |
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### Boost |
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CppCMS should work with at least Boost 1.37. |
CppCMS should work with at least Boost 1.36. |
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Generally prefer boost over other libraries, however use Boost features carefully, or do not use at all. Examples: |
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1. Boost Interprocess too "heavy" and little bit "ugly" because it supports windows and supports placing any objects in memory. The nature of `fork()` gives much better functionality and allows placing any object in shared memory every time it use shared memory allocators. |
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So use it only as replacement of libmm. |
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3. Boost Serialization -- has too many performance overheads -- don't use it. |
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### Licenses |
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1. All libraries should be OpenSource libraries |
2. Prefer non-copyleft licenses like MIT, 3 clause BSD, Boost over copyleft one, like LGPL. |
3. All libraries, CppCMS uses should be compatible with LGPLv2. |
4. You may use strong copyleft libraries for stand alone utilities that are not linked with CppCMS framework. |
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For example: If you want to write GUI for `cppcms_tcp_scale` utility using Qt you are welcome. |
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### Using |
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If you want to add an additional dependency for CppCMS make sure: |
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1. Check if boost has implementation of such feature. |
1. There is a big value for adding such dependency. |
2. This library is highly available. |
3. You checked all alternatives and decided that this one is the best. |
4. You had added an autoconf macro and conditional build for CppCMS that allows building all framework without this library. |
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For example, libgcrypt: |
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- You need high quality library to encrypt cookies, home made solutions are too dangerous. |
- This library is available for almost any UNIX platform. |
- Other alternatives like OpenSSL has problematic license and bad documentation. |
- If you do not have libgcrypt, you still have simple digitally signed cookies that are still safe. |
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