busybox/libbb/process_escape_sequence.c

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/* vi: set sw=4 ts=4: */
/*
* Utility routines.
*
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* Copyright (C) Manuel Novoa III <mjn3@codepoet.org>
* and Vladimir Oleynik <dzo@simtreas.ru>
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*/
#include <stdio.h>
#include <limits.h>
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#include <ctype.h>
#include "libbb.h"
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#define WANT_HEX_ESCAPES 1
/* Usual "this only works for ascii compatible encodings" disclaimer. */
#undef _tolower
#define _tolower(X) ((X)|((char) 0x20))
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char bb_process_escape_sequence(const char **ptr)
{
static const char charmap[] = {
'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', 0,
'\a', '\b', '\f', '\n', '\r', '\t', '\v', '\\', '\\' };
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const char *p;
const char *q;
unsigned int num_digits;
unsigned int r;
unsigned int n;
unsigned int d;
unsigned int base;
num_digits = n = 0;
base = 8;
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q = *ptr;
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#ifdef WANT_HEX_ESCAPES
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if (*q == 'x') {
++q;
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base = 16;
++num_digits;
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}
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#endif
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do {
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d = (unsigned int)(*q - '0');
#ifdef WANT_HEX_ESCAPES
if (d >= 10) {
d = ((unsigned int)(_tolower(*q) - 'a')) + 10;
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}
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#endif
if (d >= base) {
#ifdef WANT_HEX_ESCAPES
if ((base == 16) && (!--num_digits)) {
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/* return '\\'; */
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--q;
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}
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#endif
break;
}
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r = n * base + d;
if (r > UCHAR_MAX) {
break;
}
n = r;
++q;
} while (++num_digits < 3);
if (num_digits == 0) { /* mnemonic escape sequence? */
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p = charmap;
do {
if (*p == *q) {
q++;
break;
}
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} while (*++p);
n = *(p+(sizeof(charmap)/2));
}
*ptr = q;
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return (char) n;
}