cgo using c struct array and assign value in go

[wells...@xteros.com]

I have issue when using cgo with c struct array.

My program as follow:

I have struct in c  and contain a pointer to a c struct array. 

In C, I provide a initialize function (take two parameter: the pointer to the variable, the length of the array inside the variable)  to malloc the memory of the variable. 

Then In go, I assign the value to this variable and assign value to the array in variable.  And in go , I call another C function to using this variable. 

After the C function handle it.  Go pick up the variable again and return to other Go function. 

When I coded like this, I go a array like.  type *C.struct does not support indexing. 

My code like follow.

C:

test.h

typedef struct

{

int profileCnt;

_profile   *profile;                      //pointer to profile array

}_profiles;

// variable using in Go

typedef struct

{

int profileId;

_name userName;

char      *dateOfBirth;

int stateFipsId;

}_profile;

typedef struct

{

char first[32];

char last[32];

} _name;

void initializeProfiles(_profiles *profiles, int profileCount, bool create);

int doSomething _In_C( _profiles *profiles, int log);

test.c

void initializeProfiles(_profiles *profiles, int profileCount, bool create)

{

profiles->profileCnt = profileCount; // initialize profiles struct & profile[] Array

if (profileCount > 0)

{

if (create == true)

profiles->profile = malloc(profileCount * sizeof *profiles->profile + 1); // allocate memory for profiles[numProfiles]

for (int i = 0; i < profiles->profileCnt; i++)

initializeProfile(&profiles->profile[i], create);

if (create == false)

{

free(profiles->profile);

profiles->profileCnt = 0;

}

}

else

profiles->profile = NULL;

}

int doSomething _In_C( _profiles *profiles, int log)

{

/* ===========================================

*/ ====   did something to that variable============================

if (errStatus.code == _SUCCESS)

return(_SUCCESS);

else

return(FAILURE);

}

My GO code 

package main

//#cgo CFLAGS: -std=c99 -ggdb3 -O0 -Wall

//#cgo CFLAGS: -I../../include/common

//#cgo LDFLAGS: -L string.h

//#cgo LDFLAGS: -lstdc++ -lpthread -lm -lc -lssl -lcrypto

//#include <stdio.h>

//#include <stdlib.h>

//#include "test.h"

import "C"

//import "unsafe"

func Test() {

log := 1 // sets logging level

numProfiles := 3

var profiles C._profiles

C.initializeProfiles(&profiles, C.int(numProfiles), C.bool(true))

profiles.profile[0].profileId = C.int(2)

profiles.profile[0].stateFipsId = "MD"

profiles.profile[0].userName.first = "test"

profiles.profile[0].userName.last = "test"

C.dosomething_In_C( &profiles,C.int(3))

C.initializeProfiles(&profiles, C.int(numProfiles), C.bool(false))

fmt.Println(int("get c variable and  return")

}

When I compile  in like this

profiles.profile[0].profileId = C.int(2) 

I got error message : invalid operation: profiles.profile[0] (type *C.struct___6 does not support indexing)  

So, I try another solution.  Transfer the c struct array form c to go. like this 

        profile.profikes = (*[1 << 30]C._profile)(unsafe.Pointer(&profiles.profile))[:numProfiles:numProfiles]

But get error like   cannot use (*[1073741824]C.struct___6)(unsafe.Pointer(&profiles.profile))[:numProfiles:numProfiles] (type []C.struct___6) as type *C.struct___6 in assignment    

and I afraid It create another piece of memory,  when I call in dosomething_In_C function, it can not get the data. 

Is anyone know how to fix this?

Thank you 

[Wei Zhang]

Missing a C function 

void initializeProfile(_profile *profile, bool create)

{

if (create == true)

{

profile->dateOfBirth = NULL;

}

profile->profileId = 0;

memset(profile->userName.first, '\0', sizeof(profile->userName.first)); :

memset(profile->userName.last, '\0', sizeof(profile->userName.last));

profile->stateFipsId = 0;

profile->geolocation.latitude = 0.0;

profile->geolocation.longitude = 0.0;

if (create == false)

{

if (profile->dateOfBirth != NULL)

free(profile->dateOfBirth);

}

}

AND igore the Go code 

profiles.profile[0].userName.first = "test"   // It should be    profiles.profile[0].userName.first = C.CString("test")  I changed that still does not work 

profiles.profile[0].userName.last = "test"