text: // © 2017 and later: Unicode, Inc. and others.
  // License & terms of use: http://www.unicode.org/copyright.html
  
  #include "unicode/utypes.h"
  
  #if !UCONFIG_NO_FORMATTING
  #ifndef __NUMBER_STRINGBUILDER_H__
  #define __NUMBER_STRINGBUILDER_H__
  
  
  #include <cstdint>
  #include "unicode/numfmt.h"
  #include "unicode/ustring.h"
  #include "cstring.h"
  #include "uassert.h"
  #include "number_types.h"
  #include "fphdlimp.h"
  
  U_NAMESPACE_BEGIN namespace number {
  namespace impl {
  
  class U_I18N_API NumberStringBuilder : public UMemory {
    private:
      static const int32_t DEFAULT_CAPACITY = 40;
  
      template<typename T>
      union ValueOrHeapArray {
          T value[DEFAULT_CAPACITY];
          struct {
              T *ptr;
              int32_t capacity;
          } heap;
      };
  
    public:
      NumberStringBuilder();
  
      ~NumberStringBuilder();
  
      NumberStringBuilder(const NumberStringBuilder &other);
  
      NumberStringBuilder &operator=(const NumberStringBuilder &other);
  
      int32_t length() const;
  
      int32_t codePointCount() const;
  
      inline char16_t charAt(int32_t index) const {
          U_ASSERT(index >= 0);
          U_ASSERT(index < fLength);
          return getCharPtr()[fZero + index];
      }
  
      inline Field fieldAt(int32_t index) const {
          U_ASSERT(index >= 0);
          U_ASSERT(index < fLength);
          return getFieldPtr()[fZero + index];
      }
  
      UChar32 getFirstCodePoint() const;
  
      UChar32 getLastCodePoint() const;
  
      UChar32 codePointAt(int32_t index) const;
  
      UChar32 codePointBefore(int32_t index) const;
  
      NumberStringBuilder &clear();
  
      int32_t appendCodePoint(UChar32 codePoint, Field field, UErrorCode &status);
  
      int32_t insertCodePoint(int32_t index, UChar32 codePoint, Field field, UErrorCode &status);
  
      int32_t append(const UnicodeString &unistr, Field field, UErrorCode &status);
  
      int32_t insert(int32_t index, const UnicodeString &unistr, Field field, UErrorCode &status);
  
      int32_t insert(int32_t index, const UnicodeString &unistr, int32_t start, int32_t end, Field field,
                     UErrorCode &status);
  
      int32_t splice(int32_t startThis, int32_t endThis,  const UnicodeString &unistr,
                     int32_t startOther, int32_t endOther, Field field, UErrorCode& status);
  
      int32_t append(const NumberStringBuilder &other, UErrorCode &status);
  
      int32_t insert(int32_t index, const NumberStringBuilder &other, UErrorCode &status);
  
      /**
       * Gets a "safe" UnicodeString that can be used even after the NumberStringBuilder is destructed.
       * */
      UnicodeString toUnicodeString() const;
  
      /**
       * Gets an "unsafe" UnicodeString that is valid only as long as the NumberStringBuilder is alive and
       * unchanged. Slightly faster than toUnicodeString().
       */
      const UnicodeString toTempUnicodeString() const;
  
      UnicodeString toDebugString() const;
  
      const char16_t *chars() const;
  
      bool contentEquals(const NumberStringBuilder &other) const;
  
      bool nextFieldPosition(FieldPosition& fp, UErrorCode& status) const;
  
      void getAllFieldPositions(FieldPositionIteratorHandler& fpih, UErrorCode& status) const;
  
    private:
      bool fUsingHeap = false;
      ValueOrHeapArray<char16_t> fChars;
      ValueOrHeapArray<Field> fFields;
      int32_t fZero = DEFAULT_CAPACITY / 2;
      int32_t fLength = 0;
  
      inline char16_t *getCharPtr() {
          return fUsingHeap ? fChars.heap.ptr : fChars.value;
      }
  
      inline const char16_t *getCharPtr() const {
          return fUsingHeap ? fChars.heap.ptr : fChars.value;
      }
  
      inline Field *getFieldPtr() {
          return fUsingHeap ? fFields.heap.ptr : fFields.value;
      }
  
      inline const Field *getFieldPtr() const {
          return fUsingHeap ? fFields.heap.ptr : fFields.value;
      }
  
      inline int32_t getCapacity() const {
          return fUsingHeap ? fChars.heap.capacity : DEFAULT_CAPACITY;
      }
  
      int32_t prepareForInsert(int32_t index, int32_t count, UErrorCode &status);
  
      int32_t prepareForInsertHelper(int32_t index, int32_t count, UErrorCode &status);
  
      int32_t remove(int32_t index, int32_t count);
  };
  
  } // namespace impl
  } // namespace number
  U_NAMESPACE_END
  
  
  #endif //__NUMBER_STRINGBUILDER_H__
  
  #endif /* #if !UCONFIG_NO_FORMATTING */
  