126 lines
3.3 KiB
C++
126 lines
3.3 KiB
C++
/*
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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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#include "utils/strings/utf8.h"
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#include "utils/base/logging.h"
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namespace libtextclassifier3 {
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bool IsValidUTF8(const char *src, int size) {
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for (int i = 0; i < size;) {
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const int char_length = ValidUTF8CharLength(src + i, size - i);
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if (char_length <= 0) {
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return false;
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}
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i += char_length;
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}
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return true;
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}
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int ValidUTF8CharLength(const char *src, int size) {
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// Unexpected trail byte.
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if (IsTrailByte(src[0])) {
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return -1;
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}
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const int num_codepoint_bytes = GetNumBytesForUTF8Char(&src[0]);
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if (num_codepoint_bytes <= 0 || num_codepoint_bytes > size) {
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return -1;
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}
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// Check that remaining bytes in the codepoint are trailing bytes.
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for (int k = 1; k < num_codepoint_bytes; k++) {
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if (!IsTrailByte(src[k])) {
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return -1;
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}
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}
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return num_codepoint_bytes;
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}
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int SafeTruncateLength(const char *str, int truncate_at) {
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// Always want to truncate at the start of a character, so if
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// it's in a middle, back up toward the start
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while (IsTrailByte(str[truncate_at]) && (truncate_at > 0)) {
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truncate_at--;
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}
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return truncate_at;
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}
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char32 ValidCharToRune(const char *str) {
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TC3_DCHECK(!IsTrailByte(str[0]) && GetNumBytesForUTF8Char(str) > 0);
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// Convert from UTF-8
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unsigned char byte1 = static_cast<unsigned char>(str[0]);
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if (byte1 < 0x80) {
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// One character sequence: 00000 - 0007F.
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return byte1;
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}
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unsigned char byte2 = static_cast<unsigned char>(str[1]);
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if (byte1 < 0xE0) {
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// Two character sequence: 00080 - 007FF.
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return ((byte1 & 0x1F) << 6) | (byte2 & 0x3F);
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}
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unsigned char byte3 = static_cast<unsigned char>(str[2]);
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if (byte1 < 0xF0) {
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// Three character sequence: 00800 - 0FFFF.
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return ((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) | (byte3 & 0x3F);
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}
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unsigned char byte4 = static_cast<unsigned char>(str[3]);
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// Four character sequence: 10000 - 1FFFF.
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return ((byte1 & 0x07) << 18) | ((byte2 & 0x3F) << 12) |
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((byte3 & 0x3F) << 6) | (byte4 & 0x3F);
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}
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int ValidRuneToChar(const char32 rune, char *dest) {
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// Convert to unsigned for range check.
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uint32 c;
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// 1 char 00-7F
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c = rune;
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if (c <= 0x7F) {
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dest[0] = static_cast<char>(c);
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return 1;
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}
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// 2 char 0080-07FF
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if (c <= 0x07FF) {
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dest[0] = 0xC0 | static_cast<char>(c >> 1 * 6);
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dest[1] = 0x80 | (c & 0x3F);
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return 2;
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}
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// 3 char 0800-FFFF
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if (c <= 0xFFFF) {
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dest[0] = 0xE0 | static_cast<char>(c >> 2 * 6);
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dest[1] = 0x80 | ((c >> 1 * 6) & 0x3F);
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dest[2] = 0x80 | (c & 0x3F);
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return 3;
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}
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// 4 char 10000-1FFFFF
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dest[0] = 0xF0 | static_cast<char>(c >> 3 * 6);
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dest[1] = 0x80 | ((c >> 2 * 6) & 0x3F);
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dest[2] = 0x80 | ((c >> 1 * 6) & 0x3F);
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dest[3] = 0x80 | (c & 0x3F);
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return 4;
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}
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} // namespace libtextclassifier3
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