icuSources/common/capi_helper.h

   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*
  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*
  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*
  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*
  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>
  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__