How to encapsulate a C + + class in the C. language using C

In this paper, a method is given. The basic idea is to write a wrapper file, encapsulate the C + + class, and only provide the C language interface, and C++I related are implemented in the wrapper implementation file.

1. apple.h

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4. #ifndef __apple_h__
6. #define __apple_h__
8. Class Apple
10. {
12. Public
14. enum
16. {
18. Apple_color_red,
20. Apple_color_blue,
22. Apple_color_green,
24. };
28. Apple ();
30. int GetColor (void);
32. void setcolor (int color);
34. Private
36. int m_ncolor;
38. };
40. #endif

Apple.cpp:

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1. #include "apple.h"
2. Apple::apple (): M_ncolor (apple_color_red)
3. {
4. }
6. void Apple::setcolor (int color)
7. {
8. M_ncolor = color;
9. }
11. int Apple::getcolor (void)
12. {
13. return m_ncolor;
14. }

2. AppleWrapper.h

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2. #ifndef _apple_wrapper_h__
4. #define _apple_wrapper_h_
6. struct tagapple;
8. #ifdef __cplusplus
10. extern "C" {
12. #endif
14. struct Tagapple *getinstance (void);
16. void ReleaseInstance (struct tagapple **ppinstance);
18. extern void SetColor (struct tagapple *papple, int color);
20. extern int GetColor (struct tagapple *papple);
22. #ifdef __cplusplus
24. };
26. #endif
28. #endif

AppleWrapper.cpp

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2. #include "AppleWrapper.h"
4. #include "apple.h"
8. #ifdef __cplusplus
10. extern "C" {
12. #endif
14. struct Tagapple
16. {
18. Apple Apple;
20. };
22. struct Tagapple *getinstance (void)
24. {
26. return new struct tagapple;
28. }
30. void ReleaseInstance (struct tagapple **ppinstance)
32. {
34. Delete *ppinstance;
36. *ppinstance = 0;
40. }
42. void SetColor (struct tagapple *papple, int color)
44. {
46. Papple->apple. SetColor (color);
48. }
52. int GetColor (struct tagapple *papple)
54. {
56. return papple->apple.  GetColor ();
58. }
60. #ifdef __cplusplus
62. };
64. #endif

3. test.c

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2. #include "AppleWrapper.h"
4. #include <assert.h>
8. int main (void)
10. {
12. struct tagapple * papple;
14. Papple= getinstance ();
16. SetColor (Papple, 1);
18. int color = GetColor (papple);
20. printf ("color =%d\n", color);
22. ReleaseInstance (&papple);
24. ASSERT (Papple = = 0);
26. return 0;
28. }

Can be compiled with GCC:

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1. g++-C Apple.cpp
2. g++-C Apple.cpp AppleWrapper.cpp
3. GCC test.c-o test APPLEWRAPPER.O apple.o-lstdc++

In fact, wrapper in the struct completely can not, define a handle better:

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1. #ifndef _apple_wrapper_h__
2. #define _apple_wrapper_h_
3. #ifdef __cplusplus
4. extern "C" {
5. #endif
6. int getinstance (int *handle);
7. void releaseinstance (int *handle);
8. extern void SetColor (int handle, int color);
9. extern int GetColor (int handle);
10. #ifdef __cplusplus
11. };
12. #endif
13. #endif

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2. #include "AppleWrapper.h"
4. #include "apple.h"
6. #include <vectors>
10. #ifdef __cplusplus
12. extern "C" {
14. #endif
18. Static Std::vector<Apple *> G_applevector;
22. int getinstance (int * handle)
24. {
26. G_applevector[0] = new Apple;
28. *handle = 0;
30. return 1;
32. }
34. void releaseinstance (int *handle)
36. {
38. Delete G_applevector[*handle];
40. *handle =-1;
44. }
46. void SetColor (int handle, int color)
48. {
50. g_applevector[handle]->setcolor (color);
52. }
56. int GetColor (int handle)
58. {
60. return g_applevector[handle]->getcolor ();
62. }
64. #ifdef __cplusplus
66. };
68. #endif

How to encapsulate a C + + class in the C. language using C