NOTE: This documentation provides information about the programming interface provided by the SG software and a general guide to linking to the SG libraries. Information about installation, configuration, and general usage can be found in the User's Guide.
Clean OO C formalism requires that all public data is enclosed in structures which resemble C++ classes. These structures and member functions are then declared in a public header file which provides a concise description of the interface (or API) for the class. Private functions and data are included in private header files (or simply the source code files themselves) which are not visible generally visible (data encapsulation). When using the library, the user only sees the public header file and the compiled library and is therefore (hopefully) oblivious to the private members and functions. Each class is also equipped with a constructor and destructor function which is responsible for allocating and freeing any memory required by the instatiated objects.
Public data members are enclosed in C structures which are visible to the library user. Public member functions are generated by mangling the class and function names and passing a pointer to the object on which the member function is supposed to act. For example, a public member function with the C++ declaration
public double Foo::bar(int i, double d)would be declared as
double Foo_bar(Foo *thee, int i, double d)where
VEXTERNC is a compiler-dependent macro, the underscore _ replaces the C++ double-colon ::, and thee replaces the this variable implicit in all C++ classes. Since they do not appear in public header files, private functions could be declared in any format pleasing to the user, however, the above declaration convention should generally be used for both public and private functions. Within the source code, the public and private function declarations/definitions are prefaced by the macros VPUBLIC and VPRIVATE, respectively. These are macros which reduce global name pollution, similar to encapsulating private data withing C++ classes.The only C++ functions not explicitly covered by the above declaration scheme are the constructors (used to allocate and initialize class data members) and destructors (used to free allocated memory). These are declared in the following fashion: a constructor with the C++ declaration
public void Foo::Foo(int i, double d)
would be declared as
Foo* Foo_ctor(int i, double d)
which returns a pointer to the newly constructed Foo object. Likewise, a destructor declared as
public void Foo::~Foo()
in C++ would be
void Foo_dtor(Foo **thee)
in Clean OO C. Finally, inline functions in C++ are simply treated as macros in Clean OO C and declared/defined using "#define" statements in the public header file. See any of the SG header files for more examples on the Clean OO C formalism.
Below are some additional notes on the coding style I use in SG beyond what Torvalds describes. These additional guidelines are mostly concerned with being compatible with the Clean OO C dialect, giving an object-oriented look and feel to SG.
Use ONLY SPACES, NO TABS, in source code. When indenting a code block, ALWAYS USE EXACT 4 SPACES, no more, no less. While this single anal rule seems excessive, in my experience it is the single most useful code formatting guideline one can impose, in terms of producing code written by many different developers that can be read and understood quickly by other developers using the same convention. If four spaces (rather than two or three) forces you to use more than 80 columns for nesting loops/etc, then your routine is too complex to be read by someone else anyway and it should be split into two or more routines.
"#define" VTRUE 1
"#define" VFALSE 0
"#define" VABS(x) ((x) >= 0 ? (x) : -(x))
C++: class Mesh { ... };
Mesh(void) { ... }
~Mesh(void) { ... }
Clean C: typedef struct Mesh { ... } Mesh;
void Mesh_ctor(Mesh *thee) { ... }
void Mesh_dtor(Mesh *thee) { ... }
NOTE: The "this" pointer is implicitly used in C++. We simulate this coding style with the "thee" pointer in Clean C. By using a name different than "this", we continue to have a legal C++ program.
C++: Class Mesh {
...
void print(void) { ... }
...
}
void Mesh::plot(void) { ... }
Clean C: void Mesh_print(Mesh *thee) { ... }
void Mesh_plot(Mesh *thee) { ... }
I don't always adhere to this, but it helps make it clear when you are doing something unsafe with private data that you should have written an accessor member function to handle. (UPDATE: I no longer allow this practice in SG, because symbols beginning with an underscore often conflict with internal compiler symbols in GCC and other ANSI-C compilers.)
Beyond the stuctures used to define classes, only standard datatypes are used as primitive types in SG, such as char, int, float, and double.
if (cond)
{
}
whereas I find the following usually more readable:
if (cond) {
}
However, for complete routines I do follow Richard's approach:
void func(void)
{
...stuff...
}
If something is very simple then I break all rules:
int myId(void) { return id; }
SG = < Socket Graphics >
Copyright (C) 1994--2008 Michael Holst
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
1.5.6