C ++字符串和字符串向量的C实现

Question

I've some C++ APIs like below:

API1(std::string str, std::vector<std::string> vecofstr);

I want to call this API from a C code. How can i provide a C wrapper for this ?

std::string str =>

I can probably use char* for std::string

&

std::vector<std::string> vecofstr => array of char* for vector of string like

char* arrOfstrings[SIZE];

Answer 1

This is what the corresponding C header (and its C++ implementation) could look like:

Declaration

#ifdef __cplusplus
extern "C"
#endif
void cAPI1(const char *str, const char * const *vecofstr, size_t vecofstrSize);

Implementation

extern "C" void cAPI1(const char *str, const char * const *vecofstr, size_t vecofstrSize)
{
  API1(str, {vecofstr, vecofstr + vecofstrSize});
}

[Live example]

The above assumes that the C code will use zero-terminated strings for all string arguments. If that is not the case, the parameters of cAPI1 must be modified accordingly (ideally based on what representation of strings is actually used by the C code).

Answer 2

1.api.h

#ifndef API_H_
#define API_H_
#include <vector>
#include <string>

void api1(std::string& str, std::vector<std::string>& vecofstr);

#endif

.2. api.cpp

#include "api.h"
#include <iostream>

void api1(std::string& str, std::vector<std::string>& vecofstr) {
  std::cout << str << std::endl;

  for (size_t i=0; i<vecofstr.size(); i++) {
    std::cout << vecofstr[i] << std::endl;
  }
}

3.wrapper.h

#ifndef WRAPPER_H_
#define WRAPPER_H_

#define SIZE 2

#ifdef __cplusplus
extern "C" {
#endif
  extern void wrapper1(char* p, char* [SIZE]);
#ifdef __cplusplus
};
#endif
#endif

4.wrapper.cpp

#include <string>

#include "wrapper.h"
#include "api.h"

#ifdef __cplusplus
extern "C" {
#endif

void wrapper1(char* p, char* ps[SIZE]) {
  std::string str(p);
  std::vector<std::string> vecofstr;
  for (size_t idx=0; idx<SIZE; idx++) {
    vecofstr.push_back(ps[idx]);
  }
  api1(str, vecofstr);
}

#ifdef __cplusplus
};
#endif

.5. test.c

#include "wrapper.h"

int main(void)
{
  char* p = "hello world";
  char* ps[] = {"world", "hello"};
  wrapper1(p, ps);
  return 0;
}

.6. compile

gcc -c api.cpp wrapper.cpp
gcc test.c -o test wrapper.o api.o -lstdc++

.7. run

./test
hello world
world
hello