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64 lines
1.7 KiB
C

// SPDX-License-Identifier: LGPL-3.0-or-later
/**
* \file utf/utfrune.c
*
* Implements `utfrune()`.
*
* \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 *utfrune(const char *s, Rune c)
{
if (c < RUNE_SYNC) // not part of utf sequence
return strchr(s, c);
while (TRUE) {
Rune uc = *(const Uint8 *) s;
if (uc < RUNE_SELF) { // one byte
if (uc == '\0')
break;
// Following if is for reference only, optimized away, see topmost `if`
if (RUNE_SYNC != RUNE_SELF && uc == c)
return (char *) s;
s++;
continue;
}
Rune r;
size_t n = chartorune(&r, s);
if (r == c)
return (char *) s;
s += n;
}
return NULL;
}