blob: 52acb415c8ab1183e1801fe94031b4e0e9b262d4 [file] [log] [blame]
/*
* Copyright (c) 2021 Nordic Semiconductor ASA
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <stdint.h>
#include <string.h>
#include <zephyr/sys/__assert.h>
#define ASCII_CHAR 0x7F
#define SEQUENCE_FIRST_MASK 0xC0
#define SEQUENCE_LEN_2_BYTE 0xC0
#define SEQUENCE_LEN_3_BYTE 0xE0
#define SEQUENCE_LEN_4_BYTE 0xF0
char *utf8_trunc(char *utf8_str)
{
char *last_byte_p = utf8_str + strlen(utf8_str) - 1;
uint8_t bytes_truncated;
char seq_start_byte;
if ((*last_byte_p & ASCII_CHAR) == *last_byte_p) {
/* Not part of an UTF8 sequence, return */
return utf8_str;
}
/* Find the starting byte and NULL-terminate other bytes */
bytes_truncated = 0;
while ((*last_byte_p & SEQUENCE_FIRST_MASK) != SEQUENCE_FIRST_MASK &&
last_byte_p > utf8_str) {
last_byte_p--;
bytes_truncated++;
}
bytes_truncated++; /* include the starting byte */
/* Verify if the the last character actually need to be truncated
* Handles the case where the number of bytes in the last UTF8-char
* matches the number of bytes we searched for the starting byte
*/
seq_start_byte = *last_byte_p;
if ((seq_start_byte & SEQUENCE_LEN_4_BYTE) == SEQUENCE_LEN_4_BYTE) {
if (bytes_truncated == 4) {
return utf8_str;
}
} else if ((seq_start_byte & SEQUENCE_LEN_3_BYTE) == SEQUENCE_LEN_3_BYTE) {
if (bytes_truncated == 3) {
return utf8_str;
}
} else if ((seq_start_byte & SEQUENCE_LEN_2_BYTE) == SEQUENCE_LEN_2_BYTE) {
if (bytes_truncated == 2) {
return utf8_str;
}
}
/* NULL-terminate the unterminated starting byte */
*last_byte_p = '\0';
return utf8_str;
}
char *utf8_lcpy(char *dst, const char *src, size_t n)
{
__ASSERT(n > 0, "n shall not be 0");
strncpy(dst, src, n - 1);
dst[n - 1] = '\0';
if (n != 1) {
utf8_trunc(dst);
}
return dst;
}