75 lines
1.7 KiB
C
75 lines
1.7 KiB
C
/*
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* Copyright (c) 2021 Nordic Semiconductor ASA
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <stdint.h>
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#include <string.h>
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#include <sys/__assert.h>
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#define ASCII_CHAR 0x7F
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#define SEQUENCE_FIRST_MASK 0xC0
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#define SEQUENCE_LEN_2_BYTE 0xC0
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#define SEQUENCE_LEN_3_BYTE 0xE0
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#define SEQUENCE_LEN_4_BYTE 0xF0
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char *utf8_trunc(char *utf8_str)
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{
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char *last_byte_p = utf8_str + strlen(utf8_str) - 1;
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uint8_t bytes_truncated;
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char seq_start_byte;
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if ((*last_byte_p & ASCII_CHAR) == *last_byte_p) {
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/* Not part of an UTF8 sequence, return */
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return utf8_str;
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}
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/* Find the starting byte and NULL-terminate other bytes */
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bytes_truncated = 0;
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while ((*last_byte_p & SEQUENCE_FIRST_MASK) != SEQUENCE_FIRST_MASK &&
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last_byte_p > utf8_str) {
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last_byte_p--;
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bytes_truncated++;
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}
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bytes_truncated++; /* include the starting byte */
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/* Verify if the the last character actually need to be truncated
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* Handles the case where the number of bytes in the last UTF8-char
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* matches the number of bytes we searched for the starting byte
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*/
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seq_start_byte = *last_byte_p;
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if ((seq_start_byte & SEQUENCE_LEN_4_BYTE) == SEQUENCE_LEN_4_BYTE) {
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if (bytes_truncated == 4) {
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return utf8_str;
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}
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} else if ((seq_start_byte & SEQUENCE_LEN_3_BYTE) == SEQUENCE_LEN_3_BYTE) {
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if (bytes_truncated == 3) {
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return utf8_str;
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}
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} else if ((seq_start_byte & SEQUENCE_LEN_2_BYTE) == SEQUENCE_LEN_2_BYTE) {
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if (bytes_truncated == 2) {
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return utf8_str;
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}
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}
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/* NULL-terminate the unterminated starting byte */
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*last_byte_p = '\0';
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return utf8_str;
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}
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char *utf8_lcpy(char *dst, const char *src, size_t n)
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{
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__ASSERT(n > 0, "n shall not be 0");
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strncpy(dst, src, n - 1);
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dst[n - 1] = '\0';
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if (n != 1) {
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utf8_trunc(dst);
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}
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return dst;
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}
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