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/* sexp.c
*
* Parsing s-expressions.
*/
/* 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.
*/
#include "sexp.h"
#include "macros.h"
#include <stdlib.h>
#include <string.h>
/* Initializes the iterator, but one has to call next to get to the
* first element. */
static void
sexp_iterator_init(struct sexp_iterator *iterator,
unsigned length, const uint8_t *input)
{
iterator->length = length;
iterator->buffer = input;
iterator->pos = 0;
iterator->level = 0;
iterator->type = SEXP_END; /* Value doesn't matter */
iterator->display_length = 0;
iterator->display = NULL;
iterator->atom_length = 0;
iterator->atom = NULL;
/* FIXME: For other than canonical syntax,
* skip white space here. */
}
#define EMPTY(i) ((i)->pos == (i)->length)
#define NEXT(i) ((i)->buffer[(i)->pos++])
static int
sexp_iterator_simple(struct sexp_iterator *iterator,
unsigned *size,
const uint8_t **string)
{
unsigned length = 0;
uint8_t c;
if (EMPTY(iterator)) return 0;
c = NEXT(iterator);
if (EMPTY(iterator)) return 0;
if (c >= '1' && c <= '9')
do
{
length = length * 10 + (c - '0');
if (length > (iterator->length - iterator->pos))
return 0;
if (EMPTY(iterator)) return 0;
c = NEXT(iterator);
}
while (c >= '0' && c <= '9');
else if (c == '0')
/* There can be only one */
c = NEXT(iterator);
else
return 0;
if (c != ':')
return 0;
*size = length;
*string = iterator->buffer + iterator->pos;
iterator->pos += length;
return 1;
}
/* All these functions return 1 on success, 0 on failure */
/* Look at the current position in the data. Sets iterator->type, and
* ignores the old value. */
static int
sexp_iterator_parse(struct sexp_iterator *iterator)
{
iterator->start = iterator->pos;
if (EMPTY(iterator))
{
if (iterator->level)
return 0;
iterator->type = SEXP_END;
return 1;
}
switch (iterator->buffer[iterator->pos])
{
case '(': /* A list */
iterator->type = SEXP_LIST;
return 1;
case ')':
if (!iterator->level)
return 0;
iterator->pos++;
iterator->type = SEXP_END;
return 1;
case '[': /* Atom with display type */
iterator->pos++;
if (!sexp_iterator_simple(iterator,
&iterator->display_length,
&iterator->display))
return 0;
if (EMPTY(iterator) || NEXT(iterator) != ']')
return 0;
break;
default:
/* Must be either a decimal digit or a syntax error.
* Errors are detected by sexp_iterator_simple. */
iterator->display_length = 0;
iterator->display = NULL;
break;
}
iterator->type = SEXP_ATOM;
return sexp_iterator_simple(iterator,
&iterator->atom_length,
&iterator->atom);
}
int
sexp_iterator_first(struct sexp_iterator *iterator,
unsigned length, const uint8_t *input)
{
sexp_iterator_init(iterator, length, input);
return sexp_iterator_parse(iterator);
}
int
sexp_iterator_next(struct sexp_iterator *iterator)
{
switch (iterator->type)
{
case SEXP_END:
return 1;
case SEXP_LIST:
/* Skip this list */
return sexp_iterator_enter_list(iterator)
&& sexp_iterator_exit_list(iterator);
case SEXP_ATOM:
/* iterator->pos should already point at the start of the next
* element. */
return sexp_iterator_parse(iterator);
}
/* If we get here, we have a bug. */
abort();
}
/* Current element must be a list. */
int
sexp_iterator_enter_list(struct sexp_iterator *iterator)
{
if (iterator->type != SEXP_LIST)
return 0;
if (EMPTY(iterator) || NEXT(iterator) != '(')
/* Internal error */
abort();
iterator->level++;
return sexp_iterator_parse(iterator);
}
/* Skips the rest of the current list */
int
sexp_iterator_exit_list(struct sexp_iterator *iterator)
{
if (!iterator->level)
return 0;
while(iterator->type != SEXP_END)
if (!sexp_iterator_next(iterator))
return 0;
iterator->level--;
return sexp_iterator_parse(iterator);
}
const uint8_t *
sexp_iterator_subexpr(struct sexp_iterator *iterator,
unsigned *length)
{
unsigned start = iterator->start;
if (!sexp_iterator_next(iterator))
return 0;
*length = iterator->start - start;
return iterator->buffer + start;
}
int
sexp_iterator_get_uint32(struct sexp_iterator *iterator,
uint32_t *x)
{
if (iterator->type == SEXP_ATOM
&& !iterator->display
&& iterator->atom_length
&& iterator->atom[0] < 0x80)
{
unsigned length = iterator->atom_length;
const uint8_t *p = iterator->atom;
/* Skip leading zeros. */
while(length && !*p)
{
length--; p++;
}
switch(length)
{
case 0:
*x = 0;
break;
case 1:
*x = p[0];
break;
case 2:
*x = READ_UINT16(p);
break;
case 3:
*x = READ_UINT24(p);
break;
case 4:
*x = READ_UINT32(p);
break;
default:
return 0;
}
return sexp_iterator_next(iterator);
}
return 0;
}
int
sexp_iterator_check_type(struct sexp_iterator *iterator,
const uint8_t *type)
{
return (sexp_iterator_enter_list(iterator)
&& iterator->type == SEXP_ATOM
&& !iterator->display
&& strlen(type) == iterator->atom_length
&& !memcmp(type, iterator->atom, iterator->atom_length)
&& sexp_iterator_next(iterator));
}
const uint8_t *
sexp_iterator_check_types(struct sexp_iterator *iterator,
unsigned ntypes,
const uint8_t **types)
{
if (sexp_iterator_enter_list(iterator)
&& iterator->type == SEXP_ATOM
&& !iterator->display)
{
unsigned i;
for (i = 0; i<ntypes; i++)
if (strlen(types[i]) == iterator->atom_length
&& !memcmp(types[i], iterator->atom,
iterator->atom_length))
return sexp_iterator_next(iterator) ? types[i] : NULL;
}
return NULL;
}
int
sexp_iterator_assoc(struct sexp_iterator *iterator,
unsigned nkeys,
const uint8_t **keys,
struct sexp_iterator *values)
{
int *found;
unsigned nfound;
unsigned i;
found = alloca(nkeys * sizeof(*found));
for (i = 0; i<nkeys; i++)
found[i] = 0;
nfound = 0;
for (;;)
{
switch (iterator->type)
{
case SEXP_LIST:
/* FIXME: Use sexp_iterator_check_type? Problem is to
* distinguish syntax errors from unkown keys (which we want
* to just ignore). */
if (!sexp_iterator_enter_list(iterator))
return 0;
if (iterator->type == SEXP_ATOM
&& !iterator->display)
{
/* Compare to the given keys */
for (i = 0; i<nkeys; i++)
{
/* NOTE: The strlen could be put outside of the
* loop */
if (strlen(keys[i]) == iterator->atom_length
&& !memcmp(keys[i], iterator->atom,
iterator->atom_length))
{
if (found[i])
/* We don't allow duplicates */
return 0;
/* Advance to point to value */
if (!sexp_iterator_next(iterator))
return 0;
found[i] = 1;
nfound++;
/* Record this position. */
values[i] = *iterator;
break;
}
}
}
if (!sexp_iterator_exit_list(iterator))
return 0;
break;
case SEXP_ATOM:
/* Just ignore */
if (!sexp_iterator_next(iterator))
return 0;
break;
case SEXP_END:
return sexp_iterator_exit_list(iterator)
&& (nfound == nkeys);
default:
abort();
}
}
}
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