1 files changed, 97 insertions, 0 deletions
diff --git a/thirdparty/icu4c/common/capi_helper.h b/thirdparty/icu4c/common/capi_helper.h
new file mode 100644
index 0000000000..54b1db9e33
--- /dev/null
+++ b/thirdparty/icu4c/common/capi_helper.h
@@ -0,0 +1,97 @@
+// © 2018 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+
+#ifndef __CAPI_HELPER_H__
+#define __CAPI_HELPER_H__
+
+#include "unicode/utypes.h"
+
+U_NAMESPACE_BEGIN
+
+/**
+ * An internal helper class to help convert between C and C++ APIs.
+ */
+template<typename CType, typename CPPType, int32_t kMagic>
+class IcuCApiHelper {
+  public:
+    /**
+     * Convert from the C type to the C++ type (const version).
+     */
+    static const CPPType* validate(const CType* input, UErrorCode& status);
+
+    /**
+     * Convert from the C type to the C++ type (non-const version).
+     */
+    static CPPType* validate(CType* input, UErrorCode& status);
+
+    /**
+     * Convert from the C++ type to the C type (const version).
+     */
+    const CType* exportConstForC() const;
+
+    /**
+     * Convert from the C++ type to the C type (non-const version).
+     */
+    CType* exportForC();
+
+    /**
+     * Invalidates the object.
+     */
+    ~IcuCApiHelper();
+
+  private:
+    /**
+     * While the object is valid, fMagic equals kMagic.
+     */
+    int32_t fMagic = kMagic;
+};
+
+
+template<typename CType, typename CPPType, int32_t kMagic>
+const CPPType*
+IcuCApiHelper<CType, CPPType, kMagic>::validate(const CType* input, UErrorCode& status) {
+    if (U_FAILURE(status)) {
+        return nullptr;
+    }
+    if (input == nullptr) {
+        status = U_ILLEGAL_ARGUMENT_ERROR;
+        return nullptr;
+    }
+    auto* impl = reinterpret_cast<const CPPType*>(input);
+    if (static_cast<const IcuCApiHelper<CType, CPPType, kMagic>*>(impl)->fMagic != kMagic) {
+        status = U_INVALID_FORMAT_ERROR;
+        return nullptr;
+    }
+    return impl;
+}
+
+template<typename CType, typename CPPType, int32_t kMagic>
+CPPType*
+IcuCApiHelper<CType, CPPType, kMagic>::validate(CType* input, UErrorCode& status) {
+    auto* constInput = static_cast<const CType*>(input);
+    auto* validated = validate(constInput, status);
+    return const_cast<CPPType*>(validated);
+}
+
+template<typename CType, typename CPPType, int32_t kMagic>
+const CType*
+IcuCApiHelper<CType, CPPType, kMagic>::exportConstForC() const {
+    return reinterpret_cast<const CType*>(static_cast<const CPPType*>(this));
+}
+
+template<typename CType, typename CPPType, int32_t kMagic>
+CType*
+IcuCApiHelper<CType, CPPType, kMagic>::exportForC() {
+    return reinterpret_cast<CType*>(static_cast<CPPType*>(this));
+}
+
+template<typename CType, typename CPPType, int32_t kMagic>
+IcuCApiHelper<CType, CPPType, kMagic>::~IcuCApiHelper() {
+    // head off application errors by preventing use of of deleted objects.
+    fMagic = 0;
+}
+
+
+U_NAMESPACE_END
+
+#endif // __CAPI_HELPER_H__