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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_TEXT_UTF16_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_TEXT_UTF16_H_
#include <unicode/utf16.h>
#include "base/containers/span.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_uchar.h"
namespace WTF {
// U16_GET() for base::span.
// - If text[offset] is a leading surrogate and text[offset + 1] is a
// trailing surrogate, a code point computed from text[offset] and
// text[offset + 1] is returned.
// - If text[offset] is a trailing surrogate and text[offset - 1] is a
// leading surrogate, a code point computed from text[offset - 1] and
// text[offset] is returned.
// - Otherwise, text[offset] is returned;
inline UChar32 CodePointAt(base::span<const UChar> text, size_t offset) {
UChar32 code_point;
U16_GET(text, 0, offset, text.size(), code_point);
return code_point;
}
// U16_NEXT() for base::span.
// The return value is same as CodePointAt()'s. `offset` argument is updated
// to point the next of the read character.
template <typename T>
UChar32 CodePointAtAndNext(base::span<const UChar> text, T& offset) {
UChar32 code_point;
U16_NEXT(text, offset, text.size(), code_point);
return code_point;
}
template <typename T>
UChar32 CodePointAtAndNext(base::span<const LChar> text, T& offset) {
return text[offset++];
}
// This is U16_PREV() for base::span.
// Returns a code point ending with text[offset - 1]. That is to say,
// - Returns a code point computed from text[offset - 2] and text[offset - 1]
// if offset-1 is greater than start_offset and text[offset - 2] is a
// leading surrogate and text[offset - 1] is a trailing surrogate.
// - Otherwise, text[offset - 1] is returned.
//
// `offset` argument is updated to point the first code unit of the read
// character. `offset` won't be smaller than `start_offset`.
template <typename T>
UChar32 CodePointAtAndPrevious(base::span<const UChar> text,
T start_offset,
T& offset) {
DCHECK_LT(start_offset, offset);
UChar32 code_point;
U16_PREV(text, start_offset, offset, code_point);
return code_point;
}
} // namespace WTF
using WTF::CodePointAt;
using WTF::CodePointAtAndNext;
using WTF::CodePointAtAndPrevious;
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_TEXT_UTF16_H_
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