| Andrew Top | c2b4089 | 2017-01-19 14:03:49 -0800 | [diff] [blame] | 1 | /* |
| 2 | ****************************************************************************** |
| 3 | * Copyright (C) 2015, International Business Machines Corporation and |
| 4 | * others. All Rights Reserved. |
| 5 | ****************************************************************************** |
| 6 | * |
| 7 | * File unistrappender.h |
| 8 | ****************************************************************************** |
| 9 | */ |
| 10 | |
| 11 | #ifndef __UNISTRAPPENDER_H__ |
| 12 | #define __UNISTRAPPENDER_H__ |
| 13 | |
| 14 | #include "unicode/unistr.h" |
| 15 | #include "unicode/uobject.h" |
| 16 | #include "unicode/utf16.h" |
| 17 | #include "unicode/utypes.h" |
| 18 | #include "cmemory.h" |
| 19 | |
| 20 | U_NAMESPACE_BEGIN |
| 21 | |
| 22 | /** |
| 23 | * An optimization for the slowness of calling UnicodeString::append() |
| 24 | * one character at a time in a loop. It stores appends in a buffer while |
| 25 | * never actually calling append on the unicode string unless the buffer |
| 26 | * fills up or is flushed. |
| 27 | * |
| 28 | * proper usage: |
| 29 | * { |
| 30 | * UnicodeStringAppender appender(astring); |
| 31 | * for (int32_t i = 0; i < 100; ++i) { |
| 32 | * appender.append((UChar) i); |
| 33 | * } |
| 34 | * // appender flushed automatically when it goes out of scope. |
| 35 | * } |
| 36 | */ |
| 37 | class UnicodeStringAppender : public UMemory { |
| 38 | public: |
| 39 | |
| 40 | /** |
| 41 | * dest is the UnicodeString being appended to. It must always |
| 42 | * exist while this instance exists. |
| 43 | */ |
| 44 | UnicodeStringAppender(UnicodeString &dest) : fDest(&dest), fIdx(0) { } |
| 45 | |
| 46 | inline void append(UChar x) { |
| 47 | if (fIdx == UPRV_LENGTHOF(fBuffer)) { |
| 48 | fDest->append(fBuffer, 0, fIdx); |
| 49 | fIdx = 0; |
| 50 | } |
| 51 | fBuffer[fIdx++] = x; |
| 52 | } |
| 53 | |
| 54 | inline void append(UChar32 x) { |
| 55 | if (fIdx >= UPRV_LENGTHOF(fBuffer) - 1) { |
| 56 | fDest->append(fBuffer, 0, fIdx); |
| 57 | fIdx = 0; |
| 58 | } |
| 59 | U16_APPEND_UNSAFE(fBuffer, fIdx, x); |
| 60 | } |
| 61 | |
| 62 | /** |
| 63 | * Ensures that all appended characters have been written out to dest. |
| 64 | */ |
| 65 | inline void flush() { |
| 66 | if (fIdx) { |
| 67 | fDest->append(fBuffer, 0, fIdx); |
| 68 | } |
| 69 | fIdx = 0; |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * flush the buffer when we go out of scope. |
| 74 | */ |
| 75 | ~UnicodeStringAppender() { |
| 76 | flush(); |
| 77 | } |
| 78 | private: |
| 79 | UnicodeString *fDest; |
| 80 | int32_t fIdx; |
| 81 | UChar fBuffer[32]; |
| 82 | UnicodeStringAppender(const UnicodeStringAppender &other); |
| 83 | UnicodeStringAppender &operator=(const UnicodeStringAppender &other); |
| 84 | }; |
| 85 | |
| 86 | U_NAMESPACE_END |
| 87 | |
| 88 | #endif |
