CppJni | A convenient c wrapper around JNI | Wrapper library
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kandi X-RAY | CppJni Summary
A convenient C++ wrapper around JNI.
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QUESTION
For pure educational and curiosity purposes, I am trying to create an element-wrapper object that allows me to tack-on my own properties and methods to an element. The behavior I'm trying to simulate is basically this:
...ANSWER
Answered 2022-Mar-31 at 21:53I haven't test this, but maybe something like this:
QUESTION
I'm trying to define a decorator in order to execute a class method, try it first and, if an error is detected, raise it mentioning the method in which failed, so as to the user could see in which method is the error.
Here I show a MRE (Minimal, Reproducible Example) of my code.
...ANSWER
Answered 2022-Feb-22 at 17:59For decorators with parameters, you need one more level of nesting:
QUESTION
I built a C++ shared library, that exports functions for constructing, destructing and interacting with an implemented class. I want to write a wrapper class in Python, which loads the compiled .dll and wraps all the functions as a class using ctypes .
How do I wrap the destructor function of the C++ class safely so it will be called in any case (Normal Garbage Collection, Exceptions etc) ?
...ANSWER
Answered 2022-Feb-11 at 10:50As per Python's data model doc:
Objects are never explicitly destroyed; however, when they become unreachable they may be garbage-collected. An implementation is allowed to postpone garbage collection or omit it altogether...
...
Some objects contain references to “external” resources such as open files or windows. It is understood that these resources are freed when the object is garbage-collected, but since garbage collection is not guaranteed to happen, such objects also provide an explicit way to release the external resource, usually a close() method. Programs are strongly recommended to explicitly close such objects. The
try…finallystatement and thewithstatement provide convenient ways to do this.
So even if in most cases __del__ method of an object is being called by GC, it is not guaranteed. with statement (from PEP 343) on the other hand guarantees that if __enter__ method of the object succeeded, then __exit__ method will be called at the end of the statement, both in case of normal execution and in case of exception. (More detailed in this question)
An example could be as below, with the usage of "object-closing" context manager from PEP 343 examples, and a wrapper class with close method which calls native object's destructor:
QUESTION
I have functions that takes an integer as input and also output an integer. I need to write a decorator to wrap them.
The decorator will save a tuple with two numbers: the average of the inputs and the average of the outputs. For every call to that kind of function, the averages will be printed.
I'm not really sure about the way. I tried this, but it just returns the same input and output of the current function call, how can I calculate the average of all the inputs and outputs till now? or else how do I keep the args amount for the next call to decorator?
...ANSWER
Answered 2022-Jan-01 at 22:34from functools import wraps
def dec(func):
@wraps(func)
def wrap(*args):
wrap.counter += 1
wrap.sum_inputs += int(*args)
wrap.sum_outputs += func(*args)
avg_input = wrap.sum_inputs / wrap.counter
avg_output = wrap.sum_outputs / wrap.counter
print("Average of inputs ", avg_input)
print("Average of outputs ", avg_output)
return func(*args)
wrap.counter = 0
wrap.sum_inputs = 0
wrap.sum_outputs = 0
return wrap
QUESTION
My goal here is to wrap an API function so that the wrapper has the same arguments as the API function and then also has one additional final parameter. The API function is very generic so the wrapper needs to take the types and parameters from this inside function.
My reasoning is that I need to enhance the API function with additional optional arguments. For another developer using this wrapper function, it would be an awful experience to have this optional argument as the first argument.
My current attempt is as follows:
...ANSWER
Answered 2021-Dec-31 at 21:36In argument lists of functions the spread must come after other arguments. However, the same is not true for tuple types.
That means you could declare args like:
QUESTION
I read about wrappers and would like to use it for plotting. I wanted to have a wrapper function that creates and saves figure in my plot functions. However I get the error shown below. Here is my code:
...ANSWER
Answered 2021-Dec-09 at 15:58I would just declare your fig as an attribute to your plotting class and just pass x and y to your wrapper.
See code below:
QUESTION
Why does the below code print error msg instead of ABC\nerror msg?
ANSWER
Answered 2021-Nov-25 at 12:47Forget the Exception class for now. Consider this:
QUESTION
I want to write a wrapper for calling CPU-demanding functions in asyncio.
I want it to be used like this:
...ANSWER
Answered 2021-Nov-17 at 14:54Maybe the original function and the wrapped one not having the same id is the problem?
In a way, yes. Before the function is sent to the target process it's pickled, which fails in your case, because the func object in the decorator's scope is different from the fact object in your main module, after rebinding by the decorator.
Look at this and this question for some background.
Based on these answers I created an example on how what you want can be achieved.
The trick is to create a picklable "runner" function, that the target process can use to look up your orginal function from some sort of registry (e.g. a dict...) and run it. This is of course just an example. You will probably not want to create your ProcessPoolExecutor in the decorator.
QUESTION
I am attempting to port C code from one platform to another and remove dependencies.
There is a debug function called dbg_out which prints out like printf().
The prototype is void dbg_out(int dbgMask, const char *pFormat, ...);
Here is an example call : dbg_out((5, "SerialDriver : (%04x-%08lx) \n", id, sn));
I would like to map this function to a normal printf() call but having some issues.
I have attempted this so far
...ANSWER
Answered 2021-Oct-29 at 14:51You need use vprintf instead, to be able to use unknown arguments
QUESTION
I'm recently reading some source code in cBLAS, and something make me unclear. In many functions, a .c file calls Fortran Wrapper instead of writing the codes directly in the C file, like the following file:
...ANSWER
Answered 2021-Oct-18 at 20:07"What I wanna ask is actually why there is a need for a intermediate wrapper, why not write it in C?"
The whole CBLAS is a wrapper to BLAS. BLAS is defined using a reference Fortran implementation and a Fortran API. BLAS can be implemented in C or assembly, but the API is set to be Fortran.
Therefore the CBLAS does not actually contain the whole functionality. The functionality is in whatever BLAS implementation you install. The very common reference implementation is written in Fortran, but it is not the fastest one.
However, you probably could call the sdsdot function (in whichever language it is actually implemented) directly from C cblas_sdsdot. The author of CBLAS chose to implement a Fortran intermediate subroutine sdsdotsub. I do not have an answer why that is necessary right now. The difference is very small, really just changing a function to a subroutine.
As @jxh correctly comments, there is a larger risk of ABI incompatibility in calling a function vs calling a subroutine (similar to a void function).
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