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[core] Avoid some string copies in bidi implementation

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As of C++11, it's safe to preallocate std::[u16]string and write to the buffer via &s[0] (C++17 makes it possible via .data() as well).
This commit is contained in:
John Firebaugh
2017-02-24 12:52:12 -08:00
parent 92e6e48699
commit 73c5d5c00a
1 changed files with 7 additions and 6 deletions
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13
platform/default/bidi.cpp
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@@ -36,8 +36,9 @@ std::u16string applyArabicShaping(const std::u16string& input) {
// Pre-flighting will always set U_BUFFER_OVERFLOW_ERROR
errorCode = U_ZERO_ERROR;
auto outputText = std::make_unique<UChar[]>(outputLength);
u_shapeArabic(input.c_str(), static_cast<int32_t>(input.size()), outputText.get(), outputLength,
std::u16string outputText(outputLength, 0);
u_shapeArabic(input.c_str(), static_cast<int32_t>(input.size()), &outputText[0], outputLength,
(U_SHAPE_LETTERS_SHAPE & U_SHAPE_LETTERS_MASK) |
(U_SHAPE_TEXT_DIRECTION_LOGICAL & U_SHAPE_TEXT_DIRECTION_MASK),
&errorCode);
@@ -46,7 +47,7 @@ std::u16string applyArabicShaping(const std::u16string& input) {
if (U_FAILURE(errorCode))
return input;
return std::u16string(outputText.get(), outputLength);
return outputText;
}
void BiDi::mergeParagraphLineBreaks(std::set<size_t>& lineBreakPoints) {
@@ -108,12 +109,12 @@ std::u16string BiDi::getLine(std::size_t start, std::size_t end) {
// Setting UBIDI_INSERT_LRM_FOR_NUMERIC would require
// ubidi_getLength(pBiDi)+2*ubidi_countRuns(pBiDi)
const int32_t outputLength = ubidi_getProcessedLength(impl->bidiLine);
auto outputText = std::make_unique<UChar[]>(outputLength);
std::u16string outputText(outputLength, 0);
// UBIDI_DO_MIRRORING: Apply unicode mirroring of characters like parentheses
// UBIDI_REMOVE_BIDI_CONTROLS: Now that all the lines are set, remove control characters so that
// they don't show up on screen (some fonts have glyphs representing them)
ubidi_writeReordered(impl->bidiLine, outputText.get(), outputLength,
ubidi_writeReordered(impl->bidiLine, &outputText[0], outputLength,
UBIDI_DO_MIRRORING | UBIDI_REMOVE_BIDI_CONTROLS, &errorCode);
if (U_FAILURE(errorCode)) {
@@ -121,7 +122,7 @@ std::u16string BiDi::getLine(std::size_t start, std::size_t end) {
u_errorName(errorCode));
}
return std::u16string(outputText.get(), outputLength);
return outputText;
}
} // end namespace mbgl