diff --git a/sexp.c b/sexp.c
new file mode 100644
index 0000000000000000000000000000000000000000..9869d135582fc4554597e218ef2d23c4d9e1f495
--- /dev/null
+++ b/sexp.c
@@ -0,0 +1,228 @@
+/* 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 <stdlib.h>
+#include <string.h>
+
+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_START;
+ 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 (c >= '1' && c <= '9')
+ do
+ {
+ length = length * 10 + (c - '0');
+
+ if (EMPTY(iterator)) return 0;
+ c = NEXT(iterator);
+ }
+ while (c < '0' || c > '9');
+
+ else if (c != '0')
+ return 0;
+
+ if (EMPTY(iterator) || NEXT(iterator) != ':')
+ return 0;
+
+ if (length > (iterator->length - iterator->pos))
+ return 0;
+
+ *size = length;
+ *string = iterator->buffer + iterator->pos;
+ iterator->pos += length;
+
+ return 1;
+}
+
+/* All these functions return 1 on success, 0 on failure */
+int
+sexp_iterator_next(struct sexp_iterator *iterator)
+{
+ if (iterator->type == SEXP_END)
+ return 1;
+
+ if (EMPTY(iterator))
+ {
+ if (iterator->level)
+ return 0;
+
+ iterator->type = SEXP_END;
+ return 1;
+ }
+ switch (iterator->buffer[iterator->pos])
+ {
+ case '(': /* A list */
+ if (iterator->type == SEXP_START)
+ iterator->type = SEXP_LIST;
+ else
+ return sexp_iterator_enter_list(iterator)
+ && sexp_iterator_exit_list(iterator);
+ 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:
+ iterator->display_length = 0;
+ iterator->display = NULL;
+
+ break;
+ }
+
+ iterator->type = SEXP_ATOM;
+
+ return sexp_iterator_simple(iterator,
+ &iterator->atom_length,
+ &iterator->atom);
+}
+
+/* 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 1;
+}
+
+/* Skips the rest of the current list */
+int
+sexp_iterator_exit_list(struct sexp_iterator *iterator)
+{
+ if (!iterator->level)
+ return 0;
+
+ while (sexp_iterator_next(iterator))
+ if (iterator->type == SEXP_END)
+ {
+ if (NEXT(iterator) != ')')
+ return 0;
+ iterator->level--;
+ return 1;
+ }
+ return 0;
+}
+
+int
+sexp_iterator_assoc(struct sexp_iterator *iterator,
+ unsigned nkeys,
+ const struct sexp_assoc_key *keys,
+ struct sexp_iterator *values)
+{
+ if (!sexp_iterator_enter_list(iterator))
+ return 0;
+
+ for (;;)
+ {
+ if (!sexp_iterator_next(iterator))
+ return 0;
+
+ switch (iterator->type)
+ {
+ case SEXP_LIST:
+
+ if (sexp_iterator_enter_list(iterator)
+ && sexp_iterator_next(iterator))
+ return 0;
+
+ if (iterator->type == SEXP_ATOM
+ && !iterator->display)
+ {
+ /* Compare to the given keys */
+ unsigned i;
+ for (i = 0; i<nkeys; i++)
+ {
+ if (keys[i].length == iterator->atom_length
+ && !memcmp(keys[i].name, iterator->atom,
+ keys[i].length))
+ {
+ /* Match found. NOTE: We allow multiple matches. */
+ if (!sexp_iterator_next(iterator))
+ return 0;
+
+ /* Record this position. */
+ values[i] = *iterator;
+
+ break;
+ }
+ }
+ }
+ if (!sexp_iterator_exit_list(iterator))
+ return 0;
+ break;
+ case SEXP_ATOM:
+ /* Just ignore */
+ break;
+
+ case SEXP_END:
+ return sexp_iterator_exit_list(iterator);
+
+ default:
+ abort();
+ }
+ }
+}
diff --git a/sexp.h b/sexp.h
new file mode 100644
index 0000000000000000000000000000000000000000..b751b0c278c9b48a81f23005beef0ed63d6149e3
--- /dev/null
+++ b/sexp.h
@@ -0,0 +1,87 @@
+/* sexp.h
+ *
+ * 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.
+ */
+
+#ifndef NETTLE_SEXP_H_INCLUDED
+#define NETTLE_SEXP_H_INCLUDED
+
+#include <inttypes.h>
+
+enum sexp_type
+ { SEXP_START, SEXP_ATOM, SEXP_LIST, SEXP_END };
+
+struct sexp_iterator
+{
+ unsigned length;
+ const uint8_t *buffer;
+ unsigned pos;
+ unsigned level;
+
+ enum sexp_type type;
+
+ unsigned display_length;
+ const uint8_t *display;
+
+ unsigned atom_length;
+ const uint8_t *atom;
+};
+
+struct sexp_assoc_key
+{
+ unsigned length;
+ const uint8_t *name;
+};
+
+/* Initializes the iterator. You have to call next to get to the first
+ * element. */
+void
+sexp_iterator_init(struct sexp_iterator *iterator,
+ unsigned length, const uint8_t *input);
+
+/* All these functions return 1 on success, 0 on failure */
+int
+sexp_iterator_next(struct sexp_iterator *iterator);
+
+/* Current element must be a list. */
+int
+sexp_iterator_enter_list(struct sexp_iterator *iterator);
+
+/* Skips the rest of the current list */
+int
+sexp_iterator_exit_list(struct sexp_iterator *iterator);
+
+/* Current element must be a list. Looks up element of type
+ *
+ * (key rest...)
+ *
+ * For a matching key, the corersponding iterator is initialized
+ * pointing at the start of REST.
+ */
+int
+sexp_iterator_assoc(struct sexp_iterator *iterator,
+ unsigned nkeys,
+ const struct sexp_assoc_key *keys,
+ struct sexp_iterator *values);
+
+#endif /* NETTLE_SEXP_H_INCLUDED */