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250 lines
7.5 KiB
C
250 lines
7.5 KiB
C
/* convert.c - Hex conversion functions.
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* Copyright (C) 2006, 2008 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <ctype.h>
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#include "util.h"
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#define tohex(n) ((n) < 10 ? ((n) + '0') : (((n) - 10) + 'A'))
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/* Convert STRING consisting of hex characters into its binary
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representation and store that at BUFFER. BUFFER needs to be of
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LENGTH bytes. The function checks that the STRING will convert
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exactly to LENGTH bytes. The string is delimited by either end of
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string or a white space character. The function returns -1 on
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error or the length of the parsed string. */
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int
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hex2bin (const char *string, void *buffer, size_t length)
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{
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int i;
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const char *s = string;
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for (i=0; i < length; )
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{
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if (!hexdigitp (s) || !hexdigitp (s+1))
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return -1; /* Invalid hex digits. */
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((unsigned char*)buffer)[i++] = xtoi_2 (s);
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s += 2;
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}
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if (*s && (!isascii (*s) || !isspace (*s)) )
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return -1; /* Not followed by Nul or white space. */
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if (i != length)
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return -1; /* Not of expected length. */
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if (*s)
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s++; /* Skip the delimiter. */
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return s - string;
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}
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/* Convert STRING consisting of hex characters into its binary representation
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and store that at BUFFER. BUFFER needs to be of LENGTH bytes. The
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function check that the STRING will convert exactly to LENGTH
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bytes. Colons inbetween the hex digits are allowed, if one colon
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has been given a colon is expected very 2 characters. The string
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is delimited by either end of string or a white space character.
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The function returns -1 on error or the length of the parsed
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string. */
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int
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hexcolon2bin (const char *string, void *buffer, size_t length)
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{
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int i;
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const char *s = string;
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int need_colon = 0;
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for (i=0; i < length; )
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{
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if (i==1 && *s == ':') /* Skip colons between hex digits. */
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{
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need_colon = 1;
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s++;
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}
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else if (need_colon && *s == ':')
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s++;
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else if (need_colon)
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return -1; /* Colon expected. */
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if (!hexdigitp (s) || !hexdigitp (s+1))
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return -1; /* Invalid hex digits. */
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((unsigned char*)buffer)[i++] = xtoi_2 (s);
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s += 2;
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}
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if (*s == ':')
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return -1; /* Trailing colons are not allowed. */
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if (*s && (!isascii (*s) || !isspace (*s)) )
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return -1; /* Not followed by Nul or white space. */
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if (i != length)
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return -1; /* Not of expected length. */
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if (*s)
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s++; /* Skip the delimiter. */
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return s - string;
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}
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static char *
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do_bin2hex (const void *buffer, size_t length, char *stringbuf, int with_colon)
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{
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const unsigned char *s;
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char *p;
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if (!stringbuf)
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{
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/* Not really correct for with_colon but we don't care about the
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one wasted byte. */
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size_t n = with_colon? 3:2;
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size_t nbytes = n * length + 1;
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if (length && (nbytes-1) / n != length)
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{
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errno = ENOMEM;
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return NULL;
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}
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stringbuf = xtrymalloc (nbytes);
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if (!stringbuf)
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return NULL;
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}
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for (s = buffer, p = stringbuf; length; length--, s++)
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{
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if (with_colon && s != buffer)
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*p++ = ':';
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*p++ = tohex ((*s>>4)&15);
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*p++ = tohex (*s&15);
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}
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*p = 0;
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return stringbuf;
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}
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/* Convert LENGTH bytes of data in BUFFER into hex encoding and store
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that at the provided STRINGBUF. STRINGBUF must be allocated of at
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least (2*LENGTH+1) bytes or be NULL so that the function mallocs an
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appropriate buffer. Returns STRINGBUF or NULL on error (which may
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only occur if STRINGBUF has been NULL and the internal malloc
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failed). */
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char *
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bin2hex (const void *buffer, size_t length, char *stringbuf)
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{
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return do_bin2hex (buffer, length, stringbuf, 0);
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}
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/* Convert LENGTH bytes of data in BUFFER into hex encoding and store
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that at the provided STRINGBUF. STRINGBUF must be allocated of at
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least (3*LENGTH+1) bytes or be NULL so that the function mallocs an
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appropriate buffer. Returns STRINGBUF or NULL on error (which may
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only occur if STRINGBUF has been NULL and the internal malloc
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failed). */
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char *
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bin2hexcolon (const void *buffer, size_t length, char *stringbuf)
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{
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return do_bin2hex (buffer, length, stringbuf, 1);
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}
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/* Convert HEXSTRING consisting of hex characters into string and
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store that at BUFFER. HEXSTRING is either delimited by end of
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string or a white space character. The function makes sure that
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the resulting string in BUFFER is terminated by a Nul character.
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BUFSIZE is the availabe length of BUFFER; if the converted result
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plus a possible required Nul character does not fit into this
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buffer, the function returns NULL and won't change the existing
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conent of buffer. In-place conversion is possible as long as
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BUFFER points to HEXSTRING.
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If BUFFER is NULL and bufsize is 0 the function scans HEXSTRING but
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does not store anything. This may be used to find the end of
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hexstring.
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On sucess the function returns a pointer to the next character
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after HEXSTRING (which is either end-of-string or a the next white
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space). If BUFLEN is not NULL the strlen of buffer is stored
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there; this will even be done if BUFFER has been passed as NULL. */
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const char *
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hex2str (const char *hexstring, char *buffer, size_t bufsize, size_t *buflen)
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{
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const char *s = hexstring;
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int idx, count;
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int need_nul = 0;
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if (buflen)
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*buflen = 0;
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for (s=hexstring, count=0; hexdigitp (s) && hexdigitp (s+1); s += 2, count++)
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;
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if (*s && (!isascii (*s) || !isspace (*s)) )
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return NULL; /* Not followed by Nul or white space. */
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/* We need to append a nul character. However we don't want that if
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the hexstring already ends with "00". */
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need_nul = ((s == hexstring) || !(s[-2] == '0' && s[-1] == '0'));
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if (need_nul)
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count++;
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if (buffer)
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{
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if (count > bufsize)
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return NULL; /* Too long. */
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for (s=hexstring, idx=0; hexdigitp (s) && hexdigitp (s+1); s += 2)
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((unsigned char*)buffer)[idx++] = xtoi_2 (s);
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if (need_nul)
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buffer[idx] = 0;
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}
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if (buflen)
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*buflen = count - 1;
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return s;
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}
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/* Same as hex2str but this function allocated a new string. Returns
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NULL on error. If R_COUNT is not NULL, the number of scanned bytes
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will be stored there. ERRNO is set on error. */
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char *
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hex2str_alloc (const char *hexstring, size_t *r_count)
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{
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const char *tail;
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size_t nbytes;
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char *result;
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tail = hex2str (hexstring, NULL, 0, &nbytes);
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if (!tail)
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{
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if (r_count)
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*r_count = 0;
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errno = EINVAL;
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return NULL;
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}
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if (r_count)
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*r_count = tail - hexstring;
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result = xtrymalloc (nbytes+1);
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if (!result)
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return NULL;
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if (!hex2str (hexstring, result, nbytes+1, NULL))
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BUG ();
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return result;
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}
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