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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <errno.h>
     30 #include <uchar.h>
     31 #include <wchar.h>
     32 
     33 #include "private/bionic_mbstate.h"
     34 
     35 size_t c32rtomb(char* s, char32_t c32, mbstate_t* ps) {
     36   static mbstate_t __private_state;
     37   mbstate_t* state = (ps == NULL) ? &__private_state : ps;
     38 
     39   if (s == NULL) {
     40     // Equivalent to c32rtomb(buf, U'\0', ps).
     41     return reset_and_return(1, state);
     42   }
     43 
     44   // POSIX states that if char32_t is a null wide character, a null byte shall
     45   // be stored, preceded by any shift sequence needed to restore the initial
     46   // shift state. Since shift states are not supported, only the null byte is
     47   // stored.
     48   if (c32 == U'\0') {
     49     *s = '\0';
     50     reset_and_return(1, state);
     51   }
     52 
     53   if (!mbsinit(state)) {
     54     return reset_and_return_illegal(EILSEQ, state);
     55   }
     56 
     57   if ((c32 & ~0x7f) == 0) {
     58     // Fast path for plain ASCII characters.
     59     *s = c32;
     60     return 1;
     61   }
     62 
     63   // Determine the number of octets needed to represent this character.
     64   // We always output the shortest sequence possible. Also specify the
     65   // first few bits of the first octet, which contains the information
     66   // about the sequence length.
     67   uint8_t lead;
     68   size_t length;
     69   if ((c32 & ~0x7f) == 0) {
     70     lead = 0;
     71     length = 1;
     72   } else if ((c32 & ~0x7ff) == 0) {
     73     lead = 0xc0;
     74     length = 2;
     75   } else if ((c32 & ~0xffff) == 0) {
     76     lead = 0xe0;
     77     length = 3;
     78   } else if ((c32 & ~0x1fffff) == 0) {
     79     lead = 0xf0;
     80     length = 4;
     81   } else {
     82     errno = EILSEQ;
     83     return __MB_ERR_ILLEGAL_SEQUENCE;
     84   }
     85 
     86   // Output the octets representing the character in chunks
     87   // of 6 bits, least significant last. The first octet is
     88   // a special case because it contains the sequence length
     89   // information.
     90   for (size_t i = length - 1; i > 0; i--) {
     91     s[i] = (c32 & 0x3f) | 0x80;
     92     c32 >>= 6;
     93   }
     94   *s = (c32 & 0xff) | lead;
     95 
     96   return length;
     97 }
     98