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/* go-rune.c -- rune functions for Go.
Copyright 2009, 2010 The Go Authors. All rights reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file. */
#include <stddef.h>
#include "runtime.h"
#include "go-string.h"
/* Get a character from the UTF-8 string STR, of length LEN. Store
the Unicode character, if any, in *RUNE. Return the number of
characters used from STR. */
int
__go_get_rune (const unsigned char *str, size_t len, int32 *rune)
{
int c, c1, c2, c3, l;
/* Default to the "replacement character". */
*rune = 0xfffd;
if (len <= 0)
return 1;
c = *str;
if (c <= 0x7f)
{
*rune = c;
return 1;
}
if (len <= 1)
return 1;
c1 = str[1];
if ((c & 0xe0) == 0xc0
&& (c1 & 0xc0) == 0x80)
{
l = (((c & 0x1f) << 6) + (c1 & 0x3f));
if (l <= 0x7f)
return 1;
*rune = l;
return 2;
}
if (len <= 2)
return 1;
c2 = str[2];
if ((c & 0xf0) == 0xe0
&& (c1 & 0xc0) == 0x80
&& (c2 & 0xc0) == 0x80)
{
l = (((c & 0xf) << 12)
+ ((c1 & 0x3f) << 6)
+ (c2 & 0x3f));
if (l <= 0x7ff)
return 1;
if (l >= 0xd800 && l < 0xe000)
{
/* Invalid surrogate half; return replace character. */
return 1;
}
*rune = l;
return 3;
}
if (len <= 3)
return 1;
c3 = str[3];
if ((c & 0xf8) == 0xf0
&& (c1 & 0xc0) == 0x80
&& (c2 & 0xc0) == 0x80
&& (c3 & 0xc0) == 0x80)
{
l = (((c & 0x7) << 18)
+ ((c1 & 0x3f) << 12)
+ ((c2 & 0x3f) << 6)
+ (c3 & 0x3f));
if (l <= 0xffff || l > 0x10ffff)
return 1;
*rune = l;
return 4;
}
/* Invalid encoding. Return 1 so that we advance. */
return 1;
}
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