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How to pass c_char_p in c struct into CDLL exported function


How to pass c_char_p in c struct into CDLL exported function

By : Kaz
Date : November 19 2020, 01:01 AM
should help you out Absent a few lines to get the code to compile and run, it works:
X.DLL
code :
#ifdef _WIN32
#define EXPORT __declspec(dllexport)
#endif

struct bar {
    char *s1;
    char *s2;
};

EXPORT int foo(struct bar *aBarPtr)
{
    if (aBarPtr) {
        aBarPtr->s1 = "Some static string";
        aBarPtr->s2 = "Some static string2";
    }

    return 0;
}
from ctypes import *
class BAR(Structure):
    _fields_ = [
        ("s1", c_char_p),
        ("s2", c_char_p)
    ]

foo = CDLL('x').foo
foo.argtypes = [POINTER(BAR)]
bar = BAR()
print(foo(byref(bar)))
print(bar.s1)
print(bar.s2)
0
b'Some static string'
b'Some static string2'


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Size of bool in exported C function vs struct vs .Net marshaling

Size of bool in exported C function vs struct vs .Net marshaling


By : Aeq
Date : March 29 2020, 07:55 AM
seems to work fine All function parameters in C that are smaller than "int" are converted to "int" size in the call. This is because each parameter is placed on the stack separately (in most architectures), so they are converted to stack cell size which is usually equal to size of "int".
As for structure - nothing is converted. Though we should not forget about alignment in structures. But this is another story.
How to pass a pointer to a struct declared inside another struct as a function parameter?

How to pass a pointer to a struct declared inside another struct as a function parameter?


By : user3659674
Date : March 29 2020, 07:55 AM
I wish this help you In one of my applications written in C I have a struct declared as a member of another struct: , Just do:
code :
void myFunction(struct _small *poSmall)
{
    poSmall->varB = 0;
}
Why do packages export a non-exported function by returning the non-exported function through an exported function

Why do packages export a non-exported function by returning the non-exported function through an exported function


By : user4508092
Date : March 29 2020, 07:55 AM
This might help you You mentioned a couple examples. The first example (https://github.com/yohcop/openid-go/blob/master/verify.go#L11-L13):
code :
func Verify(uri string, cache DiscoveryCache, nonceStore NonceStore) (id string, err error) {
    return verify(uri, cache, urlGetter, nonceStore)
}
func StaticTokenSource(t *Token) TokenSource {
    return staticTokenSource{t}
}

// staticTokenSource is a TokenSource that always returns the same Token.
type staticTokenSource struct {
    t *Token
}
Pass a Struct to a function and create an instance of that struct inside the function

Pass a Struct to a function and create an instance of that struct inside the function


By : Krishna Aggarwal
Date : March 29 2020, 07:55 AM
To fix the issue you can do You need to use a protocol to explain to the compiler that A) these types have a .name, B) they have a .greet() function, and, finally, C) that they can be initialised with just name. In your greet() global function, you then refer to the protocol. The last wrinkles are that you pass in the type, and that you call the init(name:) explicitly...
code :
protocol HasName {
    var name: String { get set }
    func greet()
    init(name: String)
}

struct Person: HasName {
    var name: String
    func greet() {
        print("Hi person \(self.name)")
    }
}

struct Animal: HasName {
    var name: String
    func greet() {
        print("Hi animal \(self.name)")
    }
}

// ** We demand T follows the protocol, 
// ** & declare A is a type that follows the protocol, not an instance
func greet<T: HasName>(_ A: T.Type, name: String) { 
    let thingToGreet = A.init(name: name) // ** A(name: ) doesn't work
    thingToGreet.greet()
}

// Pass the struct type and a string.
greet(Person.self, name: "Johny") // ** .self returns the type
Pass a value to exported function using require

Pass a value to exported function using require


By : Mohammed Yunus
Date : March 29 2020, 07:55 AM
wish of those help require('./myExports') returns an object, so you can't just invoke it like a function. If you export just an object with two fields, you will always get that 'require(...) is not a function' error.
You have alternatives like:
code :
const bar = require('./myExports.js').bar('argForBar');
const {barF} = require('./myExports.js');
const bar = barF('argForBar');
const foo = "text";
const bar = function() {
    ...
}

const exported = function(param){
    return bar(param)
}

exported.foo = foo;
exported.bar = bar;

module.exports = exported;
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