From d9577f100bf44f7d3e38b6800a470c46d96a9f50 Mon Sep 17 00:00:00 2001 From: Ryan Lortie Date: Mon, 9 Jul 2012 14:32:22 -0400 Subject: [PATCH] gvdb-reader.c: add gvdb_table_get_names() This function lists off all names that appear within a particular hash. --- gvdb-reader.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++++++ gvdb-reader.h | 4 +- 2 files changed, 152 insertions(+), 1 deletion(-) diff --git a/gvdb-reader.c b/gvdb-reader.c index b81aa56af..a8531af2d 100644 --- a/gvdb-reader.c +++ b/gvdb-reader.c @@ -378,6 +378,155 @@ gvdb_table_list_from_item (GvdbTable *table, return TRUE; } +/** + * gvdb_table_get_names: + * @table: a #GvdbTable + * @length: the number of items returned, or %NULL + * + * Gets a list of all names contained in @table. + * + * No call to gvdb_table_get_table(), gvdb_table_list() or + * gvdb_table_get_value() will succeed unless it is for one of the + * names returned by this function. + * + * Note that some names that are returned may still fail for all of the + * above calls in the case of the corrupted file. Note also that the + * returned strings may not be utf8. + * + * Returns: a %NULL-terminated list of strings, of length @length + **/ +gchar ** +gvdb_table_get_names (GvdbTable *table, + gint *length) +{ + gchar **names; + gint n_names; + gint filled; + gint total; + gint i; + + /* We generally proceed by iterating over the list of items in the + * hash table (in order of appearance) recording them into an array. + * + * Each item has a parent item (except root items). The parent item + * forms part of the name of the item. We could go fetching the + * parent item chain at the point that we encounter each item but then + * we would need to implement some sort of recursion along with checks + * for self-referential items. + * + * Instead, we do a number of passes. Each pass will build up one + * level of names (starting from the root). We continue to do passes + * until no more items are left. The first pass will only add root + * items and each further pass will only add items whose direct parent + * is an item added in the immediately previous pass. It's also + * possible that items get filled if they follow their parent within a + * particular pass. + * + * At most we will have a number of passes equal to the depth of the + * tree. Self-referential items will never be filled in (since their + * parent will have never been filled in). We continue until we have + * a pass that fills in no additional items. + * + * This takes an O(n) algorithm and turns it into O(n*m) where m is + * the depth of the tree, but in all sane cases the tree won't be very + * deep and the constant factor of this algorithm is lower (and the + * complexity of coding it, as well). + */ + + n_names = table->n_hash_items; + names = g_new0 (gchar *, n_names + 1); + + /* 'names' starts out all-NULL. On each pass we record the number + * of items changed from NULL to non-NULL in 'filled' so we know if we + * should repeat the loop. 'total' counts the total number of items + * filled. If 'total' ends up equal to 'n_names' then we know that + * 'names' has been completely filled. + */ + + total = 0; + do + { + /* Loop until we have filled no more entries */ + filled = 0; + + for (i = 0; i < n_names; i++) + { + const struct gvdb_hash_item *item = &table->hash_items[i]; + const gchar *name; + gsize name_length; + guint32 parent; + + /* already got it on a previous pass */ + if (names[i] != NULL) + continue; + + parent = guint32_from_le (item->parent); + + if (parent == 0xffffffffu) + { + /* it's a root item */ + name = gvdb_table_item_get_key (table, item, &name_length); + + if (name != NULL) + { + names[i] = g_strndup (name, name_length); + filled++; + } + } + + else if (parent < n_names && names[parent] != NULL) + { + /* It's a non-root item whose parent was filled in already. + * + * Calculate the name of this item by combining it with + * its parent name. + */ + name = gvdb_table_item_get_key (table, item, &name_length); + + if (name != NULL) + { + const gchar *parent_name = names[parent]; + gsize parent_length; + gchar *fullname; + + parent_length = strlen (parent_name); + fullname = g_malloc (parent_length + name_length + 1); + memcpy (fullname, parent_name, parent_length); + memcpy (fullname + parent_length, name, name_length); + fullname[parent_length + name_length] = '\0'; + names[i] = fullname; + filled++; + } + } + } + + total += filled; + } + while (filled && total < n_names); + + /* If the table was corrupted then 'names' may have holes in it. + * Collapse those. + */ + if G_UNLIKELY (total != n_names) + { + GPtrArray *fixed_names; + + fixed_names = g_ptr_array_new (); + for (i = 0; i < n_names; i++) + if (names[i] != NULL) + g_ptr_array_add (fixed_names, names[i]); + + g_free (names); + n_names = fixed_names->len; + g_ptr_array_add (fixed_names, NULL); + names = (gchar **) g_ptr_array_free (fixed_names, FALSE); + } + + if (length) + *length = n_names; + + return names; +} /** * gvdb_table_list: diff --git a/gvdb-reader.h b/gvdb-reader.h index 2a50c10fb..5c4631a62 100644 --- a/gvdb-reader.h +++ b/gvdb-reader.h @@ -46,7 +46,9 @@ G_GNUC_INTERNAL GvdbTable * gvdb_table_ref (GvdbTable *table); G_GNUC_INTERNAL void gvdb_table_unref (GvdbTable *table); - +G_GNUC_INTERNAL +gchar ** gvdb_table_get_names (GvdbTable *table, + gint *length); G_GNUC_INTERNAL gchar ** gvdb_table_list (GvdbTable *table, const gchar *key);