developer.txt

1 gps基本算法

Developer's Notes for GPSTk binding for Python through SWIG 1.3.25

Supervisors
Ben Harris, David Munton

Student
Rob Chang

Date: August 1, 2005
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We need the typedef's between %{ }% because SWIG does not write the class prefix (<classname>::) in front of nested objects.

All operator overloads either require renaming or ignoring.  See common.i.

The overload for operator<< is more confusing.  Some classes list operator<< as friend functions and the overloaded functions for them are in the global scope.  Since the function parameters in Python are all the same (PyObjects), some operator<<'s end up with the same signature.  When such ambiguity occurs, I rename the operator<< for both classes to <classname>_streamRead.  Right now the pairs that conflict are:
Exception and DayTimeExceptions
Triple and Xvt

Typecasting operators (operator GPSZcount, for example) also require renaming.

Constant bracket operators require renaming.

Order matters.  If class B inherits from class A, then A.hpp needs to be %included or %imported before B.

Some functions are declared in .hpp but never implemented in .cpp.  %ignore them.

Using pydoc.py doesn't always work.  Sometimes it will return the following:
make: *** [gpstkPython.html] Segmentation fault
Just run ./pydoc.py -w gpstkPython again and it should create gpstkPython.html.

In RinexObsData.hpp, there are two typedefs: RinexPrnMap and RinexObsTypeMap.  I created templates for them so those two data types are available in Python.  To create a map template, you must also declare a pair template of the same types.  In this particular case, I had to use a BOGUS_TEMPLATE so the RinexPrnMap template will compile.  I have no idea why that is.  I reached that by accident.

Examples 1 and 3 have try+catch blocks.  But they only catch an Exception and print "Hey, exception" as opposed to the C++ version where they print specific information about the exception raised.

Many operator<< are not wrapped.  I don't know why.  I added streamRead.i and streamRead.cpp to separately implement DayTime_streamRead for example3.

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gpstkPythonUtils
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This file holds two groups of functions that I wrote.

SWIG has a std_ios.i file built-in.  But it uses integer type for openmode.  SWIG parser picks that up; therefore, calling ios.out in Python returns an integer value.  RinexObsStream constructor insists on having a pointer to "openmode".

SWIG never wrapped RinexObsStream operators << and >> because it was never explicited defined.  RinexObsStream inherits from FFTextStream which inherits from FFStream which inherits from fstream.  SWIG cannot wrap fstream because there's no fstream.hpp.  Therefore I wrote functions to perform the fstream read/write.