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-rw-r--r--uid_db.c588
1 files changed, 588 insertions, 0 deletions
diff --git a/uid_db.c b/uid_db.c
new file mode 100644
index 00000000..9648e01a
--- /dev/null
+++ b/uid_db.c
@@ -0,0 +1,588 @@
+/*
+ POP3 UID db
+
+ Copyright (c) 2010 MAD Partners, Ltd. (rweikusat@mssgmbh.com)
+
+ This file is being published in accordance with the GPLv2 terms
+ contained in the COPYING file being part of the fetchmail
+ 6.3.17 release, including the OpenSSL exemption.
+*/
+
+/* includes */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "xmalloc.h"
+#include "uid_db.h"
+
+/* constants */
+enum {
+ MIN_RECORDS = 16 /* arbitrary */
+};
+
+/* types */
+struct pat_node {
+ struct pat_node *ptrs_[3];
+
+ /*
+ The bit mask is stored in the nodes (as opposed to the
+ offset, which is (re-)calculated on demand) because
+ calculating the mask is a non-trivial operation (at
+ least on x86).
+ */
+ unsigned bit_ndx, bit_mask;
+
+ struct uid_db_record *rec;
+};
+
+/*
+ The idea behind this is that the 'left' pointer of
+ a node is accessible as ptrs(np)[-1] and the right
+ one a ptrs(np)[1]. This implies that no separate codepaths
+ for 'symmetric left- and right-cases' are needed.
+*/
+#define ptrs(np) ((np)->ptrs_ + 1)
+
+/* routines */
+/** various helpers */
+static inline unsigned bit_ofs(unsigned bit_ndx)
+{
+ return bit_ndx >> 3;
+}
+
+static inline unsigned bit_mask(unsigned bit_ndx)
+{
+ return 1 << (bit_ndx & 7);
+}
+
+/** PATRICIA trie insertion */
+/*** walkers */
+static struct pat_node *walk_down(struct uid_db *db, struct uid_db_record *rec,
+ struct pat_node ***edgep, struct pat_node **parentp)
+{
+ /*
+ Find the pat node whose id is 'most similar' to the id
+ stored in rec->id. Return a pointer to this node.
+ 'parentp' and 'edgep' are output-only parameters which
+ will point to the parent of returned node and to the edge
+ pointer going from the parent to the returned node after
+ the call has returned.
+
+ This routine is intended for inserts only.
+ */
+ struct pat_node *cur, **edge;
+ unsigned bit_ndx, v, ofs;
+
+ cur = db->pat_root;
+ ofs = -1;
+ do {
+ bit_ndx = cur->bit_ndx;
+
+ if (bit_ofs(bit_ndx) != ofs) {
+ ofs = bit_ofs(bit_ndx);
+ v = ofs < rec->id_len ? rec->id[ofs] : 0;
+ }
+
+ edge = ptrs(cur) + (v & cur->bit_mask ? 1 : -1);
+ } while ((cur = *edge) && cur->bit_ndx > bit_ndx);
+
+ *parentp =
+ (struct pat_node *)
+ ((unsigned char *)edge - (v & bit_mask(bit_ndx) ?
+ offsetof(struct pat_node, ptrs_[2])
+ : offsetof(struct pat_node, ptrs_[0])));
+ *edgep = edge;
+ return cur;
+}
+
+static inline struct pat_node *walk_up(unsigned diff_ndx, struct pat_node **parent)
+{
+ /*
+ Walk the chain of parent pointers starting with *parent until a node
+ is found whose parent has a bit_ndx smaller than diff_ndx. Return
+ a pointer to this node and update *parent to point to its parent.
+ */
+ struct pat_node *p, *np;
+
+ np = *parent;
+
+ while ((p = *ptrs(np)) && p->bit_ndx > diff_ndx)
+ np = p;
+
+ *parent = p;
+ return np;
+}
+
+/*** bit fiddling */
+static inline unsigned first_set_bit_in_char(unsigned v)
+{
+ return ffs(v) - 1;
+}
+
+static int find_first_diff_bit(struct uid_db_record const *r0,
+ struct uid_db_record const *r1)
+{
+ /*
+ Return the bit_ndx of the first differing bit in
+ r0->id and r1->id or -1 if the strings are identical.
+ */
+ struct uid_db_record const *long_id;
+ unsigned ofs, max;
+ unsigned char v;
+
+ max = r0->id_len;
+ if (max > r1->id_len) {
+ max = r1->id_len;
+ long_id = r0;
+ } else
+ long_id = r1;
+
+ ofs = 0;
+ do
+ v = r0->id[ofs] ^ r1->id[ofs];
+ while (!v && ++ofs < max);
+
+ if (!v) {
+ if (r0->id_len == r1->id_len) return -1;
+ v = long_id->id[ofs];
+ }
+
+ return first_set_bit_in_char(v) + ofs * 8;
+}
+
+static inline unsigned bit_set(unsigned bit_ndx, struct uid_db_record const *rec)
+{
+ /*
+ Return non-zero if the bit corresponding with bit_ndx is set
+ in rec->id
+ */
+ unsigned ofs;
+
+ ofs = bit_ofs(bit_ndx);
+ if (ofs >= rec->id_len) return 0;
+ return rec->id[ofs] & bit_mask(bit_ndx);
+}
+
+/*** node allocation */
+static struct pat_node *get_pat_node(struct uid_db_record *rec)
+{
+ /*
+ Allocate a pat_node, set its rec pointer to rec and the
+ next pointer of rec to NULL. Return pointer to the pat_node.
+ */
+ struct pat_node *np;
+
+ np = xmalloc(sizeof(*np));
+ np->rec = rec;
+ rec->next = NULL;
+ return np;
+}
+
+static struct pat_node *get_standalone_node(struct uid_db_record *rec)
+{
+ /*
+ Return a pat_node suitable for being inserted on the 'left edge'
+ of the trie, ie either linked to a node whose left pointer was zero
+ or being inserted as root node into an empty trie. The bit_ndx of
+ the pat_node is set to the index corresponding with the highest
+ set bit in rec->id.
+
+ NB: This is a bad choice when UIDs share a common prefix because
+ this implies that the root node will cause a bit to be tested which
+ is non-zero in all other nodes, adding a theoretically redundant
+ level to the trie. This is (to the best of my knowledge) un-
+ fortunately unavoidable if nodes with different key lengths need
+ to be supported.
+ */
+ struct pat_node *np;
+
+ np = get_pat_node(rec);
+ np->bit_ndx = first_set_bit_in_char(*rec->id);
+ np->bit_mask = bit_mask(np->bit_ndx);
+ return np;
+}
+
+/*** various helpers */
+static inline int record_id_equal(struct uid_db_record const *r0,
+ struct uid_db_record const *r1)
+{
+ return
+ r0->id_len == r1->id_len
+ && memcmp(r0->id, r1->id, r0->id_len) == 0;
+}
+
+static struct uid_db_record *append_to_list(struct uid_db_record **recp,
+ struct uid_db_record *rec)
+{
+ /*
+ Append the uid_db_record pointed to by rec to the uid_db_record
+ list accessible as *recp and return rec.
+ */
+ while (*recp) recp = &(*recp)->next;
+ *recp = rec;
+
+ rec->next = NULL;
+ return rec;
+}
+
+/*** insert routine */
+static struct uid_db_record *pat_insert(struct uid_db *db,
+ struct uid_db_record *rec)
+{
+ /*
+ Insert the record pointed to by rec in the (potentially empty)
+ PATRICIA trie pointed to by db->pat_root and return rec.
+ */
+ struct pat_node *np, *closest, *parent, **edge;
+ int me, bit_ndx;
+
+ if (!db->pat_root) {
+ np = get_standalone_node(rec);
+ ptrs(np)[-1] = *ptrs(np) = NULL;
+ ptrs(np)[1] = np;
+
+ db->pat_root = np;
+ return rec;
+ }
+
+ closest = walk_down(db, rec, &edge, &parent);
+
+ if (closest) {
+ bit_ndx = find_first_diff_bit(closest->rec, rec);
+ if (bit_ndx < 0)
+ return append_to_list(&closest->rec->next, rec);
+
+ np = get_pat_node(rec);
+ np->bit_ndx = bit_ndx;
+ np->bit_mask = bit_mask(bit_ndx);
+ } else
+ np = get_standalone_node(rec);
+
+ if (parent->bit_ndx > np->bit_ndx) {
+ closest = walk_up(np->bit_ndx, &parent);
+
+ if (!parent) edge = &db->pat_root;
+ else edge = ptrs(parent)[-1] == closest ?
+ ptrs(parent) - 1 : ptrs(parent) + 1;
+ *ptrs(closest) = np;
+ }
+
+ *edge = np;
+ *ptrs(np) = parent;
+
+ me = bit_set(np->bit_ndx, rec) ? 1 : -1;
+ ptrs(np)[me] = np;
+ ptrs(np)[-me] = closest;
+
+ return rec;
+}
+
+/** general db insertion */
+static struct uid_db_record *get_uid_db_record(char const *id, unsigned status)
+{
+ /*
+ Allocate a uid_db_record structure and set its id pointer to a
+ dynamically allocated copy of id. The status member of the
+ new record is set to status and its message number to zero (invalid).
+ A pointer to it is then returned.
+ */
+ struct uid_db_record *rec;
+ size_t id_len;
+
+ rec = xmalloc(sizeof(*rec));
+
+ id_len = strlen(id);
+ rec->id = memcpy(xmalloc(id_len + 1), id, id_len + 1);
+ rec->id_len = id_len;
+ rec->status = status;
+ rec->num = 0;
+
+ return rec;
+}
+
+static void insert_into_records(struct uid_db *db,
+ struct uid_db_record *rec)
+{
+ /*
+ Insert rec into the records array of the uid_db pointed
+ to by db. The array is grown as necessary and the
+ corresponding state variables of the db are updated
+ accordingly. The pos member of rec is set to its position
+ in the array.
+ */
+ unsigned next, want;
+
+ next = db->records_next;
+
+ if (next == db->records_max) {
+ want = db->records_max *= 2;
+ db->records = xrealloc(db->records, want * sizeof(rec));
+ }
+
+ rec->pos = next;
+ db->records[next] = rec;
+ db->records_next = next + 1;
+}
+
+struct uid_db_record *uid_db_insert(struct uid_db *db,
+ char const *id, unsigned status)
+{
+ /*
+ Create an uid_db_record whose id is id and whose status is
+ status and insert it into the uid_db pointed to by db.
+ Return a pointer to the newly created record.
+ */
+ struct uid_db_record *rec;
+
+ rec = get_uid_db_record(id, status);
+ insert_into_records(db, rec);
+ return pat_insert(db, rec);
+}
+
+/** message number index */
+void set_uid_db_num(struct uid_db *db, struct uid_db_record *rec,
+ unsigned num)
+{
+ /*
+ Set the message number of the record pointed to by rec to num
+ and insert it into the num_ndx of the uid_db pointed to by db
+ at position corresponding with num. The num_ndx lookup array
+ is grown as needed. Message numbers are expected to 'generally'
+ be recorded in ascending order and hence, no provisions are
+ made to deal with the potentially quadratic complexity of
+ inserting a sequence of numbers into an array such that it
+ needs to be grown continuously.
+ */
+ struct num_ndx *num_ndx;
+ unsigned have, want;
+
+ num_ndx = &db->num_ndx;
+
+ if (num_ndx->end_value > num) {
+ have = num_ndx->pos_0_value - num_ndx->end_value + 1;
+ want = num_ndx->pos_0_value - num + 1;
+ num_ndx->end_value = num;
+
+ num_ndx->records = xrealloc(num_ndx->records, want * sizeof(rec));
+ do num_ndx->records[--want] = NULL; while (want > have);
+ }
+
+ num_ndx->records[uid_db_num_ofs(num_ndx, num)] = rec;
+}
+
+void reset_uid_db_nums(struct uid_db *db)
+{
+ /*
+ Reset the message numbers of all uid_db_records stored
+ in the uid_db pointed to by db. The corresponding num_ndx
+ lookup array is afterwards freed and the num_ndx end_value
+ adjusted in order to indicate an 'empty' message number
+ index.
+ */
+ struct uid_db_record **rec;
+ struct num_ndx *num_ndx;
+ unsigned ndx;
+
+ num_ndx = &db->num_ndx;
+
+ if (num_ndx->end_value < num_ndx->pos_0_value) {
+ ndx = num_ndx->pos_0_value - num_ndx->end_value;
+ while (ndx) {
+ rec = num_ndx->records + --ndx;
+ if (*rec) (*rec)->num = 0;
+ }
+
+ num_ndx->end_value = num_ndx->pos_0_value + 1;
+
+ free(num_ndx->records);
+ num_ndx->records = NULL;
+ }
+}
+
+/** search routines */
+struct uid_db_record *find_uid_by_id(struct uid_db *db, char const *id)
+{
+ /*
+ Search for an uid_db_record whose id is id in the uid_db pointed
+ to by db and return a pointer to it or NULL if no such record was
+ found.
+ */
+ struct pat_node *np;
+ struct uid_db_record *rec;
+ unsigned v, bit_ndx, ofs;
+ size_t len;
+
+ np = db->pat_root;
+ if (np) {
+ len = strlen(id);
+ ofs = -1;
+ do {
+ bit_ndx = np->bit_ndx;
+
+ if (bit_ofs(bit_ndx) != ofs) {
+ ofs = bit_ofs(bit_ndx);
+ v = ofs < len ? id[ofs] : 0;
+ }
+
+ np = ptrs(np)[v & np->bit_mask ? 1 : -1];
+ } while (np && np->bit_ndx > bit_ndx);
+
+ if (!np) return NULL;
+
+ rec = np->rec;
+ return rec->id_len == len && memcmp(id, rec->id, len) == 0 ?
+ rec : NULL;
+ }
+
+ return NULL;
+}
+
+struct uid_db_record *last_uid_in_db(struct uid_db *db, char const *id)
+{
+ /*
+ Return a pointer to the 'last' (insert order) uid_db_record
+ contained in the uid_db pointed to by db whose id is id or
+ NULL if no such record exists.
+ */
+ struct uid_db_record *rec;
+
+ rec = find_uid_by_id(db, id);
+ if (!rec) return NULL;
+
+ while (rec->next) rec = rec->next;
+ return rec;
+}
+
+/** destruction */
+static void free_uid_list(struct uid_db_record *rec)
+{
+ /*
+ Free the list of uid_db_records starting with
+ the record pointed to by rec.
+ */
+ if (rec->next) free_uid_list(rec->next);
+
+ xfree(rec->id);
+ xfree(rec);
+}
+
+static void free_pat_trie(struct pat_node *np)
+{
+ /*
+ Free the PATRCIA-trie pointed to by np and all
+ uid_db_records contained in it.
+
+ The algorithm implemented below is:
+
+ 1. Load the left pointer of the node pointed to by
+ np into next.
+
+ 2. If the result is not NULL,
+ 2a) Set the left pointer to NULL.
+ 2b) Goto 1 if next points to a child of np.
+
+ 3. Load the right pointer of the node pointed to by
+ np into next.
+
+ 4. If the result is not NULL,
+ 4a) Set the right pointer to NULL.
+ 4b) Goto 1 id next points to a child of np.
+
+ 5. Load next with the parent pointer of np.
+
+ 6. Free np->rec and np.
+
+ 7. Set np to next and goto 1 if it is not null.
+ */
+ struct pat_node *next;
+
+ do {
+ next = ptrs(np)[-1];
+ if (next) {
+ ptrs(np)[-1] = NULL;
+ if (next->bit_ndx > np->bit_ndx) continue;
+ }
+
+ next = ptrs(np)[1];
+ if (next) {
+ ptrs(np)[1] = NULL;
+ if (next->bit_ndx > np->bit_ndx) continue;
+ }
+
+ next = *ptrs(np);
+
+ free_uid_list(np->rec);
+ free(np);
+ } while ((np = next));
+}
+
+void free_uid_db(struct uid_db *db)
+{
+ /*
+ Free all dynamically allocated memory of the uid_db
+ pointed to by db. The structure is not reinitialized.
+ */
+ if (db->pat_root) free_pat_trie(db->pat_root);
+
+ xfree(db->records);
+ xfree(db->num_ndx.records);
+}
+
+/** various public interfaces */
+void init_uid_db(struct uid_db *db)
+{
+ /*
+ Initialize the uid_db structure pointed to by db 'properly'
+ such that it represents an empty database. An array of
+ size MIN_RECORDS is allocated and assigned to db->records.
+ */
+ struct num_ndx *num_ndx;
+
+ db->pat_root = NULL;
+
+ db->records = xmalloc(MIN_RECORDS * sizeof(*db->records));
+ db->records_max = MIN_RECORDS;
+ db->records_next = 0;
+
+ num_ndx = &db->num_ndx;
+ num_ndx->pos_0_value = num_ndx->end_value = -1;
+ num_ndx->records = NULL;
+}
+
+void swap_uid_db_data(struct uid_db *db_0, struct uid_db *db_1)
+{
+ struct uid_db tmp;
+
+ tmp = *db_0;
+ *db_0 = *db_1;
+ *db_1 = tmp;
+}
+
+int traverse_uid_db(struct uid_db *db,
+ uid_db_traversal_routine *r, void *arg)
+{
+ /*
+ Traverses the struct uid_db records array in insert order,
+ invoking the subroutine pointed to by r with a pointer to
+ each record and the arg pointer as arguments. If the return
+ value of that is non-zero, traverse_uid_db immediately returns
+ with this value. Otherwise, zero is returned after the last
+ record was visited.
+
+ The uid_db_traversal_routine must not modify the uid_db during
+ traversal.
+ */
+ struct uid_db_record **recs;
+ unsigned ndx, max;
+ int rc;
+
+ rc = 0;
+ ndx = 0;
+ max = db->records_next;
+ recs = db->records;
+ while (ndx < max && (rc = r(recs[ndx], arg)) == 0)
+ ++ndx;
+
+ return rc;
+}
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