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
22U_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 */
39class UnicodeStringAppender : public UMemory {
40public:
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(UChar 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    }
80private:
81    UnicodeString *fDest;
82    int32_t fIdx;
83    UChar fBuffer[32];
84    UnicodeStringAppender(const UnicodeStringAppender &other);
85    UnicodeStringAppender &operator=(const UnicodeStringAppender &other);
86};
87
88U_NAMESPACE_END
89
90#endif
91