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65 lines
2.4 KiB
65 lines
2.4 KiB
7 months ago
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/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef LIBTEXTCLASSIFIER_UTILS_STRINGS_UTF8_H_
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#define LIBTEXTCLASSIFIER_UTILS_STRINGS_UTF8_H_
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#include "utils/base/integral_types.h"
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namespace libtextclassifier3 {
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// Returns the length (number of bytes) of the Unicode code point starting at
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// src, based on inspecting just that one byte. Preconditions: src != NULL,
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// *src can be read.
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static inline int GetNumBytesForUTF8Char(const char *src) {
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// On most platforms, char is unsigned by default, but iOS is an exception.
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// The cast below makes sure we always interpret *src as an unsigned char.
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return "\1\1\1\1\1\1\1\1\1\1\1\1\2\2\3\4"
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[(*(reinterpret_cast<const unsigned char *>(src)) & 0xFF) >> 4];
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}
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// Returns true if this byte is a trailing UTF-8 byte (10xx xxxx)
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static inline bool IsTrailByte(char x) {
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// return (x & 0xC0) == 0x80;
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// Since trail bytes are always in [0x80, 0xBF], we can optimize:
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return static_cast<signed char>(x) < -0x40;
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}
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// Returns true iff src points to a well-formed UTF-8 string.
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bool IsValidUTF8(const char *src, int size);
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// Helper to ensure that strings are not truncated in the middle of
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// multi-byte UTF-8 characters.
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// Given a string, and a position at which to truncate, returns the
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// last position not after the provided cut point, that would truncate a
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// full character.
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int SafeTruncateLength(const char *str, int truncate_at);
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// Gets a unicode codepoint from a valid utf8 encoding.
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char32 ValidCharToRune(const char *str);
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// Checks whether a utf8 encoding is a valid codepoint and returns the number of
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// bytes of the codepoint.
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bool IsValidChar(const char *str, int size, int *num_bytes);
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// Converts a valid codepoint to utf8.
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// Returns the length of the encoding.
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int ValidRuneToChar(const char32 rune, char *dest);
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} // namespace libtextclassifier3
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#endif // LIBTEXTCLASSIFIER_UTILS_STRINGS_UTF8_H_
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