1 // © 2018 and later: Unicode, Inc. and others.
2 // License & terms of use: http://www.unicode.org/copyright.html
3
4 #ifndef __CAPI_HELPER_H__
5 #define __CAPI_HELPER_H__
6
7 #include "unicode/utypes.h"
8
9 U_NAMESPACE_BEGIN
10
11 /**
12 * An internal helper class to help convert between C and C++ APIs.
13 */
14 template<typename CType, typename CPPType, int32_t kMagic>
15 class IcuCApiHelper {
16 public:
17 /**
18 * Convert from the C type to the C++ type (const version).
19 */
20 static const CPPType* validate(const CType* input, UErrorCode& status);
21
22 /**
23 * Convert from the C type to the C++ type (non-const version).
24 */
25 static CPPType* validate(CType* input, UErrorCode& status);
26
27 /**
28 * Convert from the C++ type to the C type (const version).
29 */
30 const CType* exportConstForC() const;
31
32 /**
33 * Convert from the C++ type to the C type (non-const version).
34 */
35 CType* exportForC();
36
37 /**
38 * Invalidates the object.
39 */
40 ~IcuCApiHelper();
41
42 private:
43 /**
44 * While the object is valid, fMagic equals kMagic.
45 */
46 int32_t fMagic = kMagic;
47 };
48
49
50 template<typename CType, typename CPPType, int32_t kMagic>
51 const CPPType*
validate(const CType * input,UErrorCode & status)52 IcuCApiHelper<CType, CPPType, kMagic>::validate(const CType* input, UErrorCode& status) {
53 if (U_FAILURE(status)) {
54 return nullptr;
55 }
56 if (input == nullptr) {
57 status = U_ILLEGAL_ARGUMENT_ERROR;
58 return nullptr;
59 }
60 auto* impl = reinterpret_cast<const CPPType*>(input);
61 if (static_cast<const IcuCApiHelper<CType, CPPType, kMagic>*>(impl)->fMagic != kMagic) {
62 status = U_INVALID_FORMAT_ERROR;
63 return nullptr;
64 }
65 return impl;
66 }
67
68 template<typename CType, typename CPPType, int32_t kMagic>
69 CPPType*
validate(CType * input,UErrorCode & status)70 IcuCApiHelper<CType, CPPType, kMagic>::validate(CType* input, UErrorCode& status) {
71 auto* constInput = static_cast<const CType*>(input);
72 auto* validated = validate(constInput, status);
73 return const_cast<CPPType*>(validated);
74 }
75
76 template<typename CType, typename CPPType, int32_t kMagic>
77 const CType*
exportConstForC()78 IcuCApiHelper<CType, CPPType, kMagic>::exportConstForC() const {
79 return reinterpret_cast<const CType*>(static_cast<const CPPType*>(this));
80 }
81
82 template<typename CType, typename CPPType, int32_t kMagic>
83 CType*
exportForC()84 IcuCApiHelper<CType, CPPType, kMagic>::exportForC() {
85 return reinterpret_cast<CType*>(static_cast<CPPType*>(this));
86 }
87
88 template<typename CType, typename CPPType, int32_t kMagic>
~IcuCApiHelper()89 IcuCApiHelper<CType, CPPType, kMagic>::~IcuCApiHelper() {
90 // head off application errors by preventing use of of deleted objects.
91 fMagic = 0;
92 }
93
94
95 U_NAMESPACE_END
96
97 #endif // __CAPI_HELPER_H__
98