Cgo pass a string to C file - go

Question

I am using cgo and saw this post about running c++ from go:
I want to use [this function] in Go. I'll use the C interface
// foo.h
#ifdef __cplusplus
extern "C" {
#endif
typedef void* Foo;
Foo FooInit(void);
void FooFree(Foo);
void FooBar(Foo);
#ifdef __cplusplus
}
#endif
I did this, but how can I pass a string as an argument to the C++ function? I tried to pass a rune[] but it did not work.

Answer 1

This is the Go code:
// GetFileSizeC wrapper method for retrieve byte lenght of a file
func GetFileSizeC(filename string) int64 {
// Cast a string to a 'C string'
fname := C.CString(filename)
defer C.free(unsafe.Pointer(fname))
// get the file size of the file
size := C.get_file_size(fname)
return int64(size)
}
From C
long get_file_size(char *filename) {
long fsize = 0;
FILE *fp;
fp = fopen(filename, "r");
if (fp) {
fseek(fp, 0, SEEK_END);
fsize = ftell(fp);
fclose(fp);
}
return fsize;
}
Remember that you need to add the headers library that you need before the import in the Go file:
package utils
// #cgo CFLAGS: -g -Wall
// #include <stdio.h> |
// #include <stdlib.h> | -> these are the necessary system header
// #include <string.h> |
// #include "cutils.h" <-- this is a custom header file
import "C"
import (
"bufio"
"encoding/json"
"fmt"
"io/ioutil"
....
)
This is an old project that you can use for future working example:
https://github.com/alessiosavi/GoUtils