ubgpsuite/lonetix/utf/utfrrune.c

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2021-06-07 16:55:13 +02:00
// SPDX-License-Identifier: LGPL-3.0-or-later
/**
* \file utf/utfrrune.c
*
* Implements `utfrrune()`.
*
* \copyright The DoubleFourteen Code Forge (C) All Rights Reserved
* \author Lorenzo Cogotti
*/
/*
* This work is derived from Plan 9 libutf, see utf/utf.h for details.
* Original license terms follow:
*
* The authors of this software are Rob Pike and Ken Thompson.
* Copyright (c) 2002 by Lucent Technologies.
* Permission to use, copy, modify, and distribute this software for any
* purpose without fee is hereby granted, provided that this entire notice
* is included in all copies of any software which is or includes a copy
* or modification of this software and in all copies of the supporting
* documentation for such software.
* THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
* ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
* OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
*
* The original libutf library is available at: https://9fans.github.io/plan9port/unix/libutf.tgz
*/
#include "utf/utf.h"
#include <string.h>
char *utfrrune(const char *s, Rune c)
{
if (c < RUNE_SYNC)
return strrchr(s, c);
char *s1 = NULL;
while (TRUE) {
Rune c1 = *(const Uint8 *) s;
if (c1 < RUNE_SELF) { // one byte rune
if (c1 == '\0')
break;
if (RUNE_SYNC != RUNE_SELF && c1 == c) // exposition only, optimized away, see topmost if ()
s1 = (char *) s;
s++;
continue;
}
Rune r;
size_t n = chartorune(&r, s);
if (r == c)
s1 = (char *) s;
s += n;
}
return s1;
}