/* $NetBSD: c8rtomb.c,v 1.10 2026/07/04 13:21:05 riastradh Exp $ */ /*- * Copyright (c) 2024 The NetBSD Foundation, Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ /* * c8rtomb(s, c8, ps) * * Encode the Unicode UTF-8 code unit c8 into the multibyte buffer * s under the current locale, using multibyte encoding state ps. * * If c8 is not the last byte of a UTF-8 scalar value sequence, no * output will be produced, but c8 will be remembered; this must * be followed by another call passing the following bytes. * * Return the number of bytes stored on success, or (size_t)-1 on * error with errno set to EILSEQ. * * At most MB_CUR_MAX bytes will be stored. * * References: * * The Unicode Standard, Version 15.0 -- Core Specification, The * Unicode Consortium, Sec. 3.9 `Unicode Encoding Forms': UTF-8, * p. 124. * https://www.unicode.org/versions/Unicode15.0.0/UnicodeStandard-15.0.pdf#page=150 * https://web.archive.org/web/20240718101254/https://www.unicode.org/versions/Unicode15.0.0/UnicodeStandard-15.0.pdf#page=150 * * F. Yergeau, `UTF-8, a transformation format of ISO 10646', * RFC 3629, Internet Engineering Task Force, November 2003. * https://datatracker.ietf.org/doc/html/rfc3629 */ #include <sys/cdefs.h> __RCSID("$NetBSD: c8rtomb.c,v 1.10 2026/07/04 13:21:05 riastradh Exp $"); #include "namespace.h" #include <assert.h> #include <errno.h> #include <limits.h> #include <locale.h> #include <stdalign.h> #include <stddef.h> #include <stdint.h> #include <uchar.h> #include "c32rtomb.h" #include "setlocale_local.h" struct c8rtombstate { char32_t state_c32; /* 8-bit state and 24-bit buffer */ mbstate_t mbs; }; __CTASSERT(offsetof(struct c8rtombstate, mbs) <= sizeof(mbstate_t)); __CTASSERT(sizeof(struct c32rtombstate) <= sizeof(mbstate_t) - offsetof(struct c8rtombstate, mbs)); __CTASSERT(alignof(struct c8rtombstate) <= alignof(mbstate_t)); /* * UTF-8 validation, inspired by Bjoern Hoermann's UTF-8 decoder at * <http://bjoern.hoehrmann.de/utf-8/decoder/dfa/>, but reimplemented * from scratch. */ #define UTF8_ACCEPT 0 #define UTF8_REJECT 96 typedef uint8_t utf8_class_t; typedef uint8_t utf8_state_t; static const uint8_t utf8_classtab[] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 10,10,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 11,3,3,3,3,3,3,3,3,3,3,3,3,4,3,3, 7,6,6,6,5,10,10,10,10,10,10,10,10,10,10,10, }; static const uint8_t utf8_statetab[] = { 0,96,12,36,48,84,72,60,96,96,96,24, 96, 0,96,96,96,96,96,96, 0, 0,96,96, 96,12,96,96,96,96,96,96,96,96,96,96, 96,12,96,96,96,96,96,96,12,12,96,96, 96,96,96,96,96,96,96,96,12,12,96,96, 96,36,96,96,96,96,96,96,96,36,96,96, 96,36,96,96,96,96,96,96,36,36,96,96, 96,96,96,96,96,96,96,96,36,96,96,96, 96,96,96,96,96,96,96,96,96,96,96,96, }; static utf8_state_t utf8_decode_step(utf8_state_t state, char8_t c8, char32_t *pc32) { const utf8_class_t class = utf8_classtab[c8]; *pc32 = (state == UTF8_ACCEPT ? (c8 & (0xff >> class)) : ((c8 & 0x3f) | (*pc32 << 6))); return utf8_statetab[state + class]; } #ifdef __weak_alias __weak_alias(c8rtomb_l,_c8rtomb_l) #endif size_t c8rtomb(char *restrict s, char8_t c8, mbstate_t *restrict ps) { return c8rtomb_l(s, c8, ps, _current_locale()); } size_t c8rtomb_l(char *restrict s, char8_t c8, mbstate_t *restrict ps, locale_t loc) { static mbstate_t psbuf; char buf[MB_LEN_MAX]; struct c8rtombstate *S; utf8_state_t state; char32_t c32; /* * `If ps is a null pointer, each function uses its own * internal mbstate_t object instead, which is initialized at * program startup to the initial conversion state; the * functions are not required to avoid data races with other * calls to the same function in this case. The * implementation behaves as if no library function calls * these functions with a null pointer for ps.' */ if (ps == NULL) ps = &psbuf; /* * `If s is a null pointer, the c8rtomb function is equivalent * to the call * * c8rtomb(buf, u8'\0', ps) * * where buf is an internal buffer. */ if (s == NULL) { s = buf; c8 = 0; /* XXX u8'\0' */ } /* * Open the private UTF-8 decoding state. */ S = (struct c8rtombstate *)(void *)ps; /* * `If c8 is a null character, a null byte is stored, preceded * by any shift sequence needed to restore the initial shift * state; the resulting state described is the initial * conversion state.' * * So if c8 is null, discard any buffered input -- there's * nothing we can legitimately do with it -- and convert a null * scalar value, which by definition of c32rtomb writes out any * shift sequence reset followed by a null byte. */ if (c8 == '\0') { c32 = 0; goto accept; } /* * Get the current state and buffer. */ __CTASSERT(UTF8_ACCEPT == 0); /* initial conversion state */ state = __SHIFTOUT(S->state_c32, __BITS(31,24)); c32 = __SHIFTOUT(S->state_c32, __BITS(23,0)); /* * Feed the byte into the state machine to update the state. */ state = utf8_decode_step(state, c8, &c32); switch (state) { case UTF8_REJECT: /* * Invalid UTF-8. Fail with EILSEQ. */ errno = EILSEQ; return (size_t)-1; default: /* * Valid UTF-8 so far but incomplete. Update state and * output nothing. */ S->state_c32 = __SHIFTIN(state, __BITS(31,24)) | __SHIFTIN(c32, __BITS(23,0)); return 0; case UTF8_ACCEPT: accept: /* * We have a scalar value. Clear the state and output * the scalar value. */ S->state_c32 = 0; return c32rtomb_l(s, c32, &S->mbs, loc); } }
