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The Tor Browser
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unistrappender.h (2440B)

      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((char16_t) 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    UnicodeStringAppender(UnicodeString &dest) : fDest(&dest), fIdx(0) { }
     47 
     48    inline void append(char16_t x) {
     49        if (fIdx == UPRV_LENGTHOF(fBuffer)) {
     50            fDest->append(fBuffer, 0, fIdx);
     51            fIdx = 0;
     52        }
     53        fBuffer[fIdx++] = x;
     54    }
     55 
     56    inline void append(UChar32 x) {
     57        if (fIdx >= UPRV_LENGTHOF(fBuffer) - 1) {
     58            fDest->append(fBuffer, 0, fIdx);
     59            fIdx = 0;
     60        }
     61        U16_APPEND_UNSAFE(fBuffer, fIdx, x);
     62    }
     63 
     64    /**
     65     * Ensures that all appended characters have been written out to dest.
     66     */
     67    inline void flush() {
     68        if (fIdx) {
     69            fDest->append(fBuffer, 0, fIdx);
     70        }
     71        fIdx = 0;
     72    }
     73 
     74    /**
     75     * flush the buffer when we go out of scope.
     76     */
     77    ~UnicodeStringAppender() {
     78        flush();
     79    }
     80 private:
     81    UnicodeString *fDest;
     82    int32_t fIdx;
     83    char16_t fBuffer[32];
     84    UnicodeStringAppender(const UnicodeStringAppender &other);
     85    UnicodeStringAppender &operator=(const UnicodeStringAppender &other);
     86 };
     87 
     88 U_NAMESPACE_END
     89 
     90 #endif