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/* sexp-transport.c
*
* Parsing s-expressions in transport format.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <string.h>
#include "sexp.h"
#include "base64.h"
/* NOTE: Decodes the input string in place */
int
sexp_transport_iterator_first(struct sexp_iterator *iterator,
unsigned length, uint8_t *input)
{
/* We first base64 decode any transport encoded sexp at the start of
* the input. */
unsigned in = 0;
unsigned out = 0;
while (in < length)
switch(input[in])
{
case ' ': /* SPC, TAB, LF, CR */
case '\t':
case '\n':
case '\r':
in++;
break;
case ';': /* Comments */
while (++in < length && input[in] != '\n')
;
break;
case '{':
{
/* Found transport encoding */
struct base64_decode_ctx ctx;
unsigned coded_length;
unsigned end;
for (end = ++in; end < length && input[end] != '}'; end++)
;
if (end == length)
return 0;
base64_decode_init(&ctx);
coded_length = end - in;
if (base64_decode_update(&ctx, &coded_length, input + out,
coded_length, input + in)
&& base64_decode_final(&ctx))
{
out += coded_length;
in = end + 1;
}
else
return 0;
break;
}
default:
/* Expression isn't in transport encoding. Rest of the input
* should be in canonical encoding. */
goto transport_done;
}
transport_done:
/* Here, we have two, possibly empty, input parts in canonical
* encoding:
*
* 0...out-1, in...length -1
*
* If the input was already in canonical encoding, out = 0 and in =
* amount of leading space.
*
* If all input was in transport encoding, in == length.
*/
if (!out)
{
input += in;
length -= in;
}
else if (in == length)
length = out;
else if (out == in)
/* Unusual case, nothing happens */
;
else
{
/* Both parts non-empty */
assert(out < in);
memmove(input + out, input + in, length - in);
length -= (in - out);
}
return sexp_iterator_first(iterator, length, input);
}
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