89 lines
2.7 KiB
C++
89 lines
2.7 KiB
C++
// Copyright 2004-present Facebook. All Rights Reserved.
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#include "Unicode.h"
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namespace facebook {
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namespace react {
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namespace unicode {
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namespace {
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// TODO(12827176): Don't duplicate this code here and fbjni.
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const uint16_t kUtf8OneByteBoundary = 0x80;
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const uint16_t kUtf8TwoBytesBoundary = 0x800;
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const uint16_t kUtf16HighSubLowBoundary = 0xD800;
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const uint16_t kUtf16HighSubHighBoundary = 0xDC00;
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const uint16_t kUtf16LowSubHighBoundary = 0xE000;
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// Calculate how many bytes are needed to convert an UTF16 string into UTF8
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// UTF16 string
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size_t utf16toUTF8Length(const uint16_t* utf16String, size_t utf16StringLen) {
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if (!utf16String || utf16StringLen == 0) {
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return 0;
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}
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uint32_t utf8StringLen = 0;
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auto utf16StringEnd = utf16String + utf16StringLen;
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auto idx16 = utf16String;
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while (idx16 < utf16StringEnd) {
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auto ch = *idx16++;
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if (ch < kUtf8OneByteBoundary) {
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utf8StringLen++;
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} else if (ch < kUtf8TwoBytesBoundary) {
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utf8StringLen += 2;
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} else if (
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(ch >= kUtf16HighSubLowBoundary) && (ch < kUtf16HighSubHighBoundary) &&
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(idx16 < utf16StringEnd) &&
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(*idx16 >= kUtf16HighSubHighBoundary) && (*idx16 < kUtf16LowSubHighBoundary)) {
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utf8StringLen += 4;
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idx16++;
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} else {
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utf8StringLen += 3;
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}
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}
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return utf8StringLen;
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}
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} // namespace
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std::string utf16toUTF8(const uint16_t* utf16String, size_t utf16StringLen) noexcept {
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if (!utf16String || utf16StringLen <= 0) {
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return "";
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}
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std::string utf8String(utf16toUTF8Length(utf16String, utf16StringLen), '\0');
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auto idx8 = utf8String.begin();
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auto idx16 = utf16String;
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auto utf16StringEnd = utf16String + utf16StringLen;
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while (idx16 < utf16StringEnd) {
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auto ch = *idx16++;
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if (ch < kUtf8OneByteBoundary) {
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*idx8++ = (ch & 0x7F);
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} else if (ch < kUtf8TwoBytesBoundary) {
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*idx8++ = 0b11000000 | (ch >> 6);
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*idx8++ = 0b10000000 | (ch & 0x3F);
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} else if (
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(ch >= kUtf16HighSubLowBoundary) && (ch < kUtf16HighSubHighBoundary) &&
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(idx16 < utf16StringEnd) &&
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(*idx16 >= kUtf16HighSubHighBoundary) && (*idx16 < kUtf16LowSubHighBoundary)) {
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auto ch2 = *idx16++;
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uint8_t trunc_byte = (((ch >> 6) & 0x0F) + 1);
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*idx8++ = 0b11110000 | (trunc_byte >> 2);
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*idx8++ = 0b10000000 | ((trunc_byte & 0x03) << 4) | ((ch >> 2) & 0x0F);
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*idx8++ = 0b10000000 | ((ch & 0x03) << 4) | ((ch2 >> 6) & 0x0F);
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*idx8++ = 0b10000000 | (ch2 & 0x3F);
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} else {
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*idx8++ = 0b11100000 | (ch >> 12);
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*idx8++ = 0b10000000 | ((ch >> 6) & 0x3F);
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*idx8++ = 0b10000000 | (ch & 0x3F);
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}
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}
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return utf8String;
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}
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} // namespace unicode
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} // namespace react
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} // namespace facebook
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