lib/encode.c

   1 /*
   2  * Based on code from libblkid,
   3  *
   4  * Copyright (C) 2008 Kay Sievers <kay.sievers@vrfy.org>
   5  * Copyright (C) 2009 Karel Zak <kzak@redhat.com>
   6  * Copyright (C) 2020 Pali Rohár <pali.rohar@gmail.com>
   7  *
   8  * This file may be redistributed under the terms of the
   9  * GNU Lesser General Public License.
  10  */
  11 #include "c.h"
  12 #include "encode.h"
  13
  14 size_t ul_encode_to_utf8(int enc, unsigned char *dest, size_t len,
  15                         const unsigned char *src, size_t count)
  16 {
  17         size_t i, j;
  18         uint32_t c;
  19         uint16_t c2;
  20
  21         for (j = i = 0; i < count; i++) {
  22                 if (enc == UL_ENCODE_UTF16LE) {
  23                         if (i+2 > count)
  24                                 break;
  25                         c = (src[i+1] << 8) | src[i];
  26                         i++;
  27                 } else if (enc == UL_ENCODE_UTF16BE) {
  28                         if (i+2 > count)
  29                                 break;
  30                         c = (src[i] << 8) | src[i+1];
  31                         i++;
  32                 } else if (enc == UL_ENCODE_LATIN1) {
  33                         c = src[i];
  34                 } else {
  35                         return 0;
  36                 }
  37                 if ((enc == UL_ENCODE_UTF16LE || enc == UL_ENCODE_UTF16BE) &&
  38                     c >= 0xD800 && c <= 0xDBFF && i+2 < count) {
  39                         if (enc == UL_ENCODE_UTF16LE)
  40                                 c2 = (src[i+2] << 8) | src[i+1];
  41                         else
  42                                 c2 = (src[i+1] << 8) | src[i+2];
  43                         if (c2 >= 0xDC00 && c2 <= 0xDFFF) {
  44                                 c = 0x10000 + ((c - 0xD800) << 10) + (c2 - 0xDC00);
  45                                 i += 2;
  46                         }
  47                 }
  48                 if (c == 0) {
  49                         dest[j] = '\0';
  50                         break;
  51                 }
  52
  53                 if (c < 0x80) {
  54                         if (j+1 >= len)
  55                                 break;
  56                         dest[j++] = (uint8_t) c;
  57                 } else if (c < 0x800) {
  58                         if (j+2 >= len)
  59                                 break;
  60                         dest[j++] = (uint8_t) (0xc0 | (c >> 6));
  61                         dest[j++] = (uint8_t) (0x80 | (c & 0x3f));
  62                 } else if (c < 0x10000) {
  63                         if (j+3 >= len)
  64                                 break;
  65                         dest[j++] = (uint8_t) (0xe0 | (c >> 12));
  66                         dest[j++] = (uint8_t) (0x80 | ((c >> 6) & 0x3f));
  67                         dest[j++] = (uint8_t) (0x80 | (c & 0x3f));
  68                 } else {
  69                         if (j+4 >= len)
  70                                 break;
  71                         dest[j++] = (uint8_t) (0xf0 | (c >> 18));
  72                         dest[j++] = (uint8_t) (0x80 | ((c >> 12) & 0x3f));
  73                         dest[j++] = (uint8_t) (0x80 | ((c >> 6) & 0x3f));
  74                         dest[j++] = (uint8_t) (0x80 | (c & 0x3f));
  75                 }
  76         }
  77         dest[j] = '\0';
  78         return j;
  79 }