Line data    Source code

       1             : // © 2016 and later: Unicode, Inc. and others.
       2             : // License & terms of use: http://www.unicode.org/copyright.html
       3             : /*
       4             : ******************************************************************************
       5             : * Copyright (C) 2015, International Business Machines Corporation and
       6             : * others. All Rights Reserved.
       7             : ******************************************************************************
       8             : *
       9             : * File unistrappender.h
      10             : ******************************************************************************
      11             : */
      12             : 
      13             : #ifndef __UNISTRAPPENDER_H__
      14             : #define __UNISTRAPPENDER_H__
      15             : 
      16             : #include "unicode/unistr.h"
      17             : #include "unicode/uobject.h"
      18             : #include "unicode/utf16.h"
      19             : #include "unicode/utypes.h"
      20             : #include "cmemory.h"
      21             : 
      22             : U_NAMESPACE_BEGIN
      23             : 
      24             : /**
      25             :  * An optimization for the slowness of calling UnicodeString::append()
      26             :  * one character at a time in a loop. It stores appends in a buffer while
      27             :  * never actually calling append on the unicode string unless the buffer
      28             :  * fills up or is flushed.
      29             :  * 
      30             :  * proper usage:
      31             :  * {
      32             :  *     UnicodeStringAppender appender(astring);
      33             :  *     for (int32_t i = 0; i < 100; ++i) {
      34             :  *        appender.append((UChar) i);
      35             :  *     }
      36             :  *     // appender flushed automatically when it goes out of scope.
      37             :  * }
      38             :  */
      39             : class UnicodeStringAppender : public UMemory {
      40             : public:
      41             :     
      42             :     /**
      43             :      * dest is the UnicodeString being appended to. It must always
      44             :      * exist while this instance exists.
      45             :      */
      46           0 :     UnicodeStringAppender(UnicodeString &dest) : fDest(&dest), fIdx(0) { }
      47             : 
      48           0 :     inline void append(UChar x) {
      49           0 :         if (fIdx == UPRV_LENGTHOF(fBuffer)) {
      50           0 :             fDest->append(fBuffer, 0, fIdx);
      51           0 :             fIdx = 0;
      52             :         }
      53           0 :         fBuffer[fIdx++] = x;
      54           0 :     }
      55             : 
      56           0 :     inline void append(UChar32 x) {
      57           0 :         if (fIdx >= UPRV_LENGTHOF(fBuffer) - 1) {
      58           0 :             fDest->append(fBuffer, 0, fIdx);
      59           0 :             fIdx = 0;
      60             :         }
      61           0 :         U16_APPEND_UNSAFE(fBuffer, fIdx, x);
      62           0 :     }
      63             : 
      64             :     /**
      65             :      * Ensures that all appended characters have been written out to dest.
      66             :      */
      67           0 :     inline void flush() {
      68           0 :         if (fIdx) {
      69           0 :             fDest->append(fBuffer, 0, fIdx);
      70             :         }
      71           0 :         fIdx = 0;
      72           0 :     }
      73             : 
      74             :     /**
      75             :      * flush the buffer when we go out of scope.
      76             :      */
      77           0 :     ~UnicodeStringAppender() {
      78           0 :         flush();
      79           0 :     }
      80             : private:
      81             :     UnicodeString *fDest;
      82             :     int32_t fIdx;
      83             :     UChar fBuffer[32];
      84             :     UnicodeStringAppender(const UnicodeStringAppender &other);
      85             :     UnicodeStringAppender &operator=(const UnicodeStringAppender &other);
      86             : };
      87             : 
      88             : U_NAMESPACE_END
      89             : 
      90             : #endif