GIO: Add gvdb as private API

gio/Makefile.am

@@ -79,6 +79,11 @@ gio-marshal.c: gio-marshal.h gio-marshal.list
 	$(glib_genmarshal) --prefix=_gio_marshal $(srcdir)/gio-marshal.list --body --internal) > $@.tmp && \
 	  mv $@.tmp $@
 
+settings_sources = \
+	gvdb/gvdb-format.h		\
+	gvdb/gvdb-reader.h		\
+	gvdb/gvdb-reader.c
+
 local_sources = \
 	glocaldirectorymonitor.c 	\
 	glocaldirectorymonitor.h 	\
@@ -289,6 +294,7 @@ libgio_2_0_la_SOURCES =		\
 	$(unix_sources) 	\
 	$(win32_sources) 	\
 	$(local_sources) 	\
+	$(settings_sources) 	\
 	$(marshal_sources) 	\
 	$(NULL)
 

gio/gvdb/gvdb-builder.c

@@ -0,0 +1,501 @@
+#include "gvdb-builder.h"
+
+#include <glib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "gvdb.h"
+
+struct _GvdbItem
+{
+  gchar *key;
+  guint32 hash_value;
+  guint32_le assigned_index;
+  GvdbItem *parent;
+  GvdbItem *sibling;
+  GvdbItem *next;
+  GVariant *options;
+
+  /* one of:
+   * this:
+   */
+  GVariant *value;
+
+  /* this: */
+  GHashTable *table;
+
+  /* or this: */
+  GvdbItem *child;
+};
+
+static void
+gvdb_item_free (gpointer data)
+{
+  GvdbItem *item = data;
+
+  g_free (item->key);
+
+  if (item->value)
+    g_variant_unref (item->value);
+
+  if (item->options)
+    g_variant_unref (item->options);
+
+  if (item->table)
+    g_hash_table_unref (item->table);
+
+  g_slice_free (GvdbItem, item);
+}
+
+GHashTable *
+gvdb_hash_table_new (GHashTable  *parent,
+                     const gchar *name_in_parent)
+{
+  GHashTable *table;
+
+  table = g_hash_table_new_full (g_str_hash, g_str_equal,
+                                 g_free, gvdb_item_free);
+
+  if (parent)
+    {
+      GvdbItem *item;
+
+      item = gvdb_hash_table_insert (parent, name_in_parent);
+      gvdb_item_set_hash_table (item, table);
+    }
+
+  return table;
+}
+
+static guint32
+djb_hash (const gchar *key)
+{
+  guint32 hash_value = 5381;
+
+  while (*key)
+    hash_value = hash_value * 33 + *key++;
+
+  return hash_value;
+}
+
+GvdbItem *
+gvdb_hash_table_insert (GHashTable  *table,
+                        const gchar *key)
+{
+  GvdbItem *item;
+
+  item = g_slice_new0 (GvdbItem);
+  item->key = g_strdup (key);
+  item->hash_value = djb_hash (key);
+
+  g_hash_table_insert (table, g_strdup (key), item);
+
+  return item;
+}
+
+void
+gvdb_hash_table_insert_string (GHashTable  *table,
+                               const gchar *key,
+                               const gchar *value)
+{
+  GvdbItem *item;
+
+  item = gvdb_hash_table_insert (table, key);
+  gvdb_item_set_value (item, g_variant_new_string (value));
+}
+
+void
+gvdb_item_set_value (GvdbItem *item,
+                     GVariant *value)
+{
+  g_return_if_fail (!item->value && !item->table && !item->child);
+
+  item->value = g_variant_ref_sink (value);
+}
+
+void
+gvdb_item_set_options (GvdbItem *item,
+                       GVariant *options)
+{
+  g_return_if_fail (!item->options);
+
+  item->options = g_variant_ref_sink (options);
+}
+
+void
+gvdb_item_set_hash_table (GvdbItem   *item,
+                          GHashTable *table)
+{
+  g_return_if_fail (!item->value && !item->table && !item->child);
+
+  item->table = g_hash_table_ref (table);
+}
+
+void
+gvdb_item_set_parent (GvdbItem *item,
+                      GvdbItem *parent)
+{
+  GvdbItem **node;
+
+  g_return_if_fail (g_str_has_prefix (item->key, parent->key));
+  g_return_if_fail (!parent->value && !parent->table);
+  g_return_if_fail (!item->parent && !item->sibling);
+
+  for (node = &parent->child; *node; node = &(*node)->sibling)
+    if (strcmp ((*node)->key, item->key) > 0)
+      break;
+
+  item->parent = parent;
+  item->sibling = *node;
+  *node = item;
+}
+
+
+
+
+typedef struct
+{
+  GvdbItem **buckets;
+  gint n_buckets;
+} HashTable;
+
+HashTable *
+hash_table_new (gint n_buckets)
+{
+  HashTable *table;
+
+  table = g_slice_new (HashTable);
+  table->buckets = g_new0 (GvdbItem *, n_buckets);
+  table->n_buckets = n_buckets;
+
+  return table;
+}
+
+static void
+hash_table_insert (gpointer key,
+                   gpointer value,
+                   gpointer data)
+{
+  guint32 hash_value, bucket;
+  HashTable *table = data;
+  GvdbItem *item = value;
+
+g_print ("i see %s\n", (char*) key);
+
+  hash_value = djb_hash (key);
+  bucket = hash_value % table->n_buckets;
+  item->next = table->buckets[bucket];
+  table->buckets[bucket] = item;
+}
+
+static guint32_le
+item_to_index (GvdbItem *item)
+{
+  if (item != NULL)
+    return item->assigned_index;
+
+  return guint32_to_le (-1u);
+}
+
+typedef struct
+{
+  GString *strings;
+  GQueue *chunks;
+  guint64 offset;
+
+} FileBuilder;
+
+typedef struct
+{
+  gsize offset;
+  gsize size;
+  gpointer data;
+} FileChunk;
+
+static gpointer
+file_builder_allocate (FileBuilder         *fb,
+                       guint                alignment,
+                       gsize                size,
+                       struct gvdb_pointer *pointer)
+{
+  FileChunk *chunk;
+
+  fb->offset += (-fb->offset) & (alignment - 1);
+  chunk = g_slice_new (FileChunk);
+  chunk->offset = fb->offset;
+  chunk->size = size;
+  chunk->data = g_malloc (size);
+
+  pointer->start = guint32_to_le (fb->offset);
+  fb->offset += size;
+  pointer->end = guint32_to_le (fb->offset);
+
+  g_queue_push_tail (fb->chunks, chunk);
+
+  return chunk->data;
+}
+
+static void
+file_builder_add_value (FileBuilder         *fb,
+                        GVariant            *value,
+		        struct gvdb_pointer *pointer)
+{
+  GVariant *variant, *normal;
+  gpointer data;
+  gsize size;
+
+  variant = g_variant_new_variant (value);
+  normal = g_variant_get_normal_form (variant);
+  g_variant_unref (variant);
+
+  size = g_variant_get_size (normal);
+  data = file_builder_allocate (fb, 8, size, pointer);
+  g_variant_store (normal, data);
+  g_variant_unref (normal);
+}
+
+static void
+file_builder_add_options (FileBuilder         *fb,
+                          GVariant            *options,
+                          struct gvdb_pointer *pointer)
+{
+  GVariant *normal;
+  gpointer data;
+  gsize size;
+
+  if (options != NULL)
+    {
+      normal = g_variant_get_normal_form (options);
+      size = g_variant_get_size (normal);
+      data = file_builder_allocate (fb, 8, size, pointer);
+      g_variant_store (normal, data);
+      g_variant_unref (normal);
+    }
+  else
+    {
+      pointer->start = guint32_to_le (0);
+      pointer->end = guint32_to_le (0);
+    }
+}
+
+static void
+file_builder_add_string (FileBuilder *fb,
+                         const gchar *string,
+                         guint32_le  *start,
+                         guint16_le  *size)
+{
+  FileChunk *chunk;
+  gsize length;
+
+  length = strlen (string);
+
+  chunk = g_slice_new (FileChunk);
+  chunk->offset = fb->offset;
+  chunk->size = length;
+  chunk->data = g_malloc (length);
+  memcpy (chunk->data, string, length);
+
+  *start = guint32_to_le (fb->offset);
+  *size = guint16_to_le (length);
+  fb->offset += length;
+
+  g_queue_push_tail (fb->chunks, chunk);
+}
+
+static void
+file_builder_allocate_for_hash (FileBuilder            *fb,
+                                gsize                   n_buckets,
+                                gsize                   n_items,
+                                guint                   bloom_shift,
+                                gsize                   n_bloom_words,
+                                guint32_le            **bloom_filter,
+                                guint32_le            **hash_buckets,
+                                struct gvdb_hash_item **hash_items,
+                                struct gvdb_pointer    *pointer)
+{
+  guint32_le bloom_hdr, table_hdr;
+  guchar *data;
+  gsize size;
+
+  g_assert (n_bloom_words < (1u << 27));
+
+  bloom_hdr = guint32_to_le (bloom_shift << 27 | n_bloom_words);
+  table_hdr = guint32_to_le (n_buckets);
+
+  size = sizeof bloom_hdr + sizeof table_hdr +
+         n_bloom_words * sizeof (guint32_le) +
+         n_buckets     * sizeof (guint32_le) +
+         n_items       * sizeof (struct gvdb_hash_item);
+
+  data = file_builder_allocate (fb, 4, size, pointer);
+
+#define chunk(s) (size -= (s), data += (s), data - (s))
+  memcpy (chunk (sizeof bloom_hdr), &bloom_hdr, sizeof bloom_hdr);
+  memcpy (chunk (sizeof table_hdr), &table_hdr, sizeof table_hdr);
+  *bloom_filter = (guint32_le *) chunk (n_bloom_words * sizeof (guint32_le));
+  *hash_buckets = (guint32_le *) chunk (n_buckets * sizeof (guint32_le));
+  *hash_items = (struct gvdb_hash_item *) chunk (n_items *
+                  sizeof (struct gvdb_hash_item));
+  g_assert (size == 0);
+#undef chunk
+
+  memset (*bloom_filter, 0, n_bloom_words * sizeof (guint32_le));
+}
+
+static void
+file_builder_add_hash (FileBuilder         *fb,
+                       GHashTable          *table,
+                       struct gvdb_pointer *pointer)
+{
+  guint32_le *buckets, *bloom_filter;
+  struct gvdb_hash_item *items;
+  HashTable *mytable;
+  GvdbItem *item;
+  guint32 index;
+  gint bucket;
+
+  mytable = hash_table_new (g_hash_table_size (table));
+  g_hash_table_foreach (table, hash_table_insert, mytable);
+  index = 0;
+
+  for (bucket = 0; bucket < mytable->n_buckets; bucket++)
+    for (item = mytable->buckets[bucket]; item; item = item->next)
+      item->assigned_index = guint32_to_le (index++);
+
+  file_builder_allocate_for_hash (fb, mytable->n_buckets, index, 5, 0,
+                                  &bloom_filter, &buckets, &items, pointer);
+
+  for (bucket = 0; bucket < mytable->n_buckets; bucket++)
+    {
+      buckets[bucket] = item_to_index (mytable->buckets[bucket]);
+
+      for (item = mytable->buckets[bucket]; item; item = item->next)
+        {
+          struct gvdb_hash_item *entry = items++;
+          const gchar *basename;
+
+          entry->hash_value = guint32_to_le (item->hash_value);
+          entry->parent = item_to_index (item->parent);
+          entry->unused = 0;
+
+          if (item->parent != NULL)
+            basename = item->key + strlen (item->parent->key);
+          else
+            basename = item->key;
+
+          file_builder_add_string (fb, basename,
+                                   &entry->key_start,
+                                   &entry->key_size);
+
+          if (item->value != NULL)
+            {
+              g_assert (item->child == NULL && item->table == NULL);
+
+              file_builder_add_value (fb, item->value, &entry->value.pointer);
+              file_builder_add_options (fb, item->options, &entry->options);
+              entry->type = 'v';
+            }
+
+          if (item->child != NULL)
+            {
+              guint32 children = 0;
+              guint32_le *offsets;
+              GvdbItem *child;
+
+              g_assert (item->table == NULL);
+
+              for (child = item->child; child; child = child->sibling)
+                children++;
+
+              offsets = file_builder_allocate (fb, 4, 4 * children,
+                                               &entry->value.pointer);
+              entry->type = 'L';
+
+              for (child = item->child; child; child = child->sibling)
+                offsets[--children] = child->assigned_index;
+
+              g_assert (children == 0);
+            }
+
+          if (item->table != NULL)
+            {
+              entry->type = 'H';
+              file_builder_add_hash (fb, item->table, &entry->value.pointer);
+            }
+        }
+    }
+}
+
+static FileBuilder *
+file_builder_new (void)
+{
+  FileBuilder *builder;
+
+  builder = g_slice_new (FileBuilder);
+  builder->strings = g_string_new ("");
+  builder->chunks = g_queue_new ();
+  builder->offset = sizeof (struct gvdb_header);
+
+  return builder;
+}
+
+static gboolean
+file_builder_write (FileBuilder          *fb,
+                    GOutputStream        *output,
+                    struct gvdb_pointer   root,
+                    GError              **error)
+{
+  struct gvdb_header header = { { GVDB_SIGNATURE0, GVDB_SIGNATURE1 } };
+  gchar zero[8] = { 0, };
+  gsize offset;
+
+  header.root = root;
+  if (!g_output_stream_write_all (output, &header, sizeof header,
+                                  NULL, NULL, error))
+    return FALSE;
+
+  offset = sizeof header;
+  while (!g_queue_is_empty (fb->chunks))
+    {
+      FileChunk *chunk = g_queue_pop_head (fb->chunks);
+
+      if (chunk->offset != offset)
+        {
+          g_assert (chunk->offset > offset);
+          g_assert (chunk->offset - offset < 8);
+
+          if (!g_output_stream_write_all (output, zero,
+                                          chunk->offset - offset,
+                                          NULL, NULL, error))
+            return FALSE;
+
+          offset = chunk->offset;
+        }
+
+      if (!g_output_stream_write_all (output, chunk->data, chunk->size,
+                                      NULL, NULL, error))
+        return FALSE;
+
+      offset += chunk->size;
+      g_free (chunk->data);
+    }
+
+  g_queue_free (fb->chunks);
+  g_slice_free (FileBuilder, fb);
+
+  return TRUE;
+}
+
+gboolean
+gvdb_file_write (GOutputStream  *output,
+                 GHashTable     *table,
+                 GError        **error)
+{
+  struct gvdb_pointer root;
+  FileBuilder *fb;
+
+  fb = file_builder_new ();
+  file_builder_add_hash (fb, table, &root);
+  return file_builder_write (fb, output, root, error);
+}

gio/gvdb/gvdb-builder.h

@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2010 Codethink Limited
+ *
+ * This 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 of the licence, or (at your option) any later version.
+ *
+ * This 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 this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __gvdb_builder_h__
+#define __gvdb_builder_h__
+
+#include <gio/gio.h>
+
+typedef struct _GvdbItem GvdbItem;
+
+G_GNUC_INTERNAL
+GHashTable *            gvdb_hash_table_new                             (GHashTable    *parent,
+                                                                         const gchar   *key);
+
+G_GNUC_INTERNAL
+GvdbItem *              gvdb_hash_table_insert                          (GHashTable    *table,
+                                                                         const gchar   *key);
+G_GNUC_INTERNAL
+void                    gvdb_hash_table_insert_string                   (GHashTable    *table,
+                                                                         const gchar   *key,
+                                                                         const gchar   *value);
+
+G_GNUC_INTERNAL
+void                    gvdb_item_set_value                             (GvdbItem      *item,
+                                                                         GVariant      *value);
+G_GNUC_INTERNAL
+void                    gvdb_item_set_options                           (GvdbItem      *item,
+                                                                         GVariant      *options);
+G_GNUC_INTERNAL
+void                    gvdb_item_set_hash_table                        (GvdbItem      *item,
+                                                                         GHashTable    *table);
+G_GNUC_INTERNAL
+void                    gvdb_item_set_parent                            (GvdbItem      *item,
+                                                                         GvdbItem      *parent);
+
+G_GNUC_INTERNAL
+gboolean                gvdb_file_write                                 (GOutputStream  *output,
+                                                                         GHashTable     *table,
+                                                                         GError        **error);
+
+#endif /* __gvdb_builder_h__ */

gio/gvdb/gvdb-format.h

@@ -0,0 +1,61 @@
+#include <glib.h>
+
+typedef struct { guint16 __value; } guint16_le;
+typedef struct { guint32 __value; } guint32_le;
+
+struct gvdb_pointer {
+  guint32_le start;
+  guint32_le end;
+};
+
+struct gvdb_hash_header {
+  guint32_le n_bloom_words;
+  guint32_le n_buckets;
+};
+
+struct gvdb_hash_item {
+  guint32_le hash_value;
+  guint32_le parent;
+
+  guint32_le key_start;
+  guint16_le key_size;
+  gchar type;
+  gchar unused;
+
+  union
+  {
+    struct gvdb_pointer pointer;
+    gchar direct[8];
+  } value;
+
+  struct gvdb_pointer options;
+};
+
+struct gvdb_header {
+  guint32 signature[2];
+  guint32_le version;
+  guint32_le options;
+
+  struct gvdb_pointer root;
+};
+
+static inline guint32_le guint32_to_le (guint32 value) {
+  guint32_le result = { GUINT32_TO_LE (value) };
+  return result;
+}
+
+static inline guint32 guint32_from_le (guint32_le value) {
+  return GUINT32_FROM_LE (value.__value);
+}
+
+static inline guint16_le guint16_to_le (guint16 value) {
+  guint16_le result = { GUINT16_TO_LE (value) };
+  return result;
+}
+
+static inline guint16 guint16_from_le (guint16_le value) {
+  return GUINT16_FROM_LE (value.__value);
+}
+
+#define GVDB_SIGNATURE0 1918981703
+#define GVDB_SIGNATURE1 1953390953

gio/gvdb/gvdb-reader.c

@@ -0,0 +1,464 @@
+/*
+ * Copyright © 2010 Codethink Limited
+ *
+ * This 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 of the licence, or (at your option) any later version.
+ *
+ * This 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 this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "gvdb-reader.h"
+#include "gvdb-format.h"
+
+#include <string.h>
+
+struct _GvdbTable {
+  gint ref_count;
+
+  const gchar *data;
+  gsize size;
+
+  GMappedFile *mapped;
+  gboolean trusted;
+
+  const guint32 *bloom_words;
+  guint32 n_bloom_words;
+  guint bloom_shift;
+
+  const guint32 *hash_buckets;
+  guint32 n_buckets;
+
+  struct gvdb_hash_item *hash_items;
+  guint32 n_hash_items;
+};
+
+static const gchar *
+gvdb_table_item_get_key (GvdbTable                   *file,
+                         const struct gvdb_hash_item *item,
+                         gsize                       *size)
+{
+  guint32 start, end;
+
+  start = guint32_from_le (item->key_start);
+  *size = guint16_from_le (item->key_size);
+  end = start + *size;
+
+  if G_UNLIKELY (start > end || end > file->size)
+    return NULL;
+
+  return file->data + start;
+}
+
+static gconstpointer
+gvdb_table_dereference (GvdbTable                 *file,
+                        const struct gvdb_pointer *pointer,
+                        gint                       alignment,
+                        gsize                     *size)
+{
+  guint32 start, end;
+
+  start = guint32_from_le (pointer->start);
+  end = guint32_from_le (pointer->end);
+
+  if G_UNLIKELY (start > end || end > file->size || start & (alignment - 1))
+    return NULL;
+
+  *size = end - start;
+
+  return file->data + start;
+}
+
+static void
+gvdb_table_setup_root (GvdbTable                 *file,
+                       const struct gvdb_pointer *pointer)
+{
+  const struct gvdb_hash_header *header;
+  guint32 n_bloom_words;
+  guint32 bloom_shift;
+  guint32 n_buckets;
+  gsize size;
+
+  header = gvdb_table_dereference (file, pointer, 4, &size);
+
+  if G_UNLIKELY (header == NULL || size < sizeof *header)
+    return;
+
+  size -= sizeof *header;
+
+  n_bloom_words = guint32_from_le (header->n_bloom_words);
+  n_buckets = guint32_from_le (header->n_buckets);
+  bloom_shift = n_bloom_words >> 27;
+  n_bloom_words &= (1u << 27) - 1;
+
+  if G_UNLIKELY (n_bloom_words * sizeof (guint32_le) > size)
+    return;
+
+  file->bloom_words = (gpointer) (header + 1);
+  size -= n_bloom_words * sizeof (guint32_le);
+  file->n_bloom_words = n_bloom_words;
+
+  if G_UNLIKELY (n_buckets > G_MAXUINT / sizeof (guint32_le) ||
+                 n_buckets * sizeof (guint32_le) > size)
+    return;
+
+  file->hash_buckets = file->bloom_words + file->n_bloom_words;
+  size -= n_buckets * sizeof (guint32_le);
+  file->n_buckets = n_buckets;
+
+  if G_UNLIKELY (size % sizeof (struct gvdb_hash_item))
+    return;
+
+  file->hash_items = (gpointer) (file->hash_buckets + n_buckets);
+  file->n_hash_items = size / sizeof (struct gvdb_hash_item);
+}
+
+/**
+ * gvdb_table_new:
+ * @filename: the path to the hash file
+ * @trusted: if the contents of @filename are trusted
+ * @error: %NULL, or a pointer to a %NULL #GError
+ * @returns: a new #GvdbTable
+ *
+ * Creates a new #GvdbTable from the contents of the file found at
+ * @filename.
+ *
+ * The only time this function fails is if the file can not be opened.
+ * In that case, the #GError that is returned will be an error from
+ * g_mapped_file_new().
+ *
+ * An empty or otherwise corrupted file is considered to be a valid
+ * #GvdbTable with no entries.
+ *
+ * You should call gvdb_table_unref() on the return result when you no
+ * longer require it.
+ **/
+GvdbTable *
+gvdb_table_new (const gchar  *filename,
+                gboolean      trusted,
+                GError      **error)
+{
+  GMappedFile *mapped;
+  GvdbTable *file;
+
+  if ((mapped = g_mapped_file_new (filename, FALSE, error)) == NULL)
+    return NULL;
+
+  file = g_slice_new0 (GvdbTable);
+  file->data = g_mapped_file_get_contents (mapped);
+  file->size = g_mapped_file_get_length (mapped);
+  file->trusted = trusted;
+  file->mapped = mapped;
+  file->ref_count = 1;
+
+  if (sizeof (struct gvdb_header) <= file->size)
+    {
+      const struct gvdb_header *header = (gpointer) file->data;
+      gvdb_table_setup_root (file, &header->root);
+    }
+
+  return file;
+}
+
+static gboolean
+gvdb_table_bloom_filter (GvdbTable *file,
+                          guint32    hash_value)
+{
+  guint32 word, mask;
+
+  if (file->n_bloom_words == 0)
+    return TRUE;
+
+  word = (hash_value / 32) % file->n_bloom_words;
+  mask = 1 << (hash_value & 31);
+  mask |= 1 << ((hash_value >> file->bloom_shift) & 31);
+
+  return (file->bloom_words[word] & mask) == mask;
+}
+
+static gboolean
+gvdb_table_check_name (GvdbTable             *file,
+                       struct gvdb_hash_item *item,
+                       const gchar           *key,
+                       guint                  key_length)
+{
+  const gchar *this_key;
+  gsize this_size;
+  guint32 parent;
+
+  this_key = gvdb_table_item_get_key (file, item, &this_size);
+
+  if G_UNLIKELY (this_key == NULL || this_size > key_length)
+    return FALSE;
+
+  key_length -= this_size;
+
+  if G_UNLIKELY (memcmp (this_key, key + key_length, this_size) != 0)
+    return FALSE;
+
+  parent = guint32_from_le (item->parent);
+  if (key_length == 0 && parent == -1)
+    return TRUE;
+
+  if G_LIKELY (parent < file->n_hash_items && this_size > 0)
+    return gvdb_table_check_name (file,
+                                   &file->hash_items[parent],
+                                   key, key_length);
+
+  return FALSE;
+}
+
+const struct gvdb_hash_item *
+gvdb_table_lookup (GvdbTable   *file,
+                    const gchar *key,
+                    gchar        type)
+{
+  guint32 hash_value = 5381;
+  guint key_length;
+  guint32 itemno;
+
+  if G_UNLIKELY (file->n_buckets == 0 || file->n_hash_items == 0)
+    return NULL;
+
+  for (key_length = 0; key[key_length]; key_length++)
+    hash_value = (hash_value * 33) + key[key_length];
+
+  if (!gvdb_table_bloom_filter (file, hash_value))
+    return NULL;
+
+  itemno = file->hash_buckets[hash_value % file->n_buckets];
+  hash_value &= ~(1u << 31);
+
+  while G_LIKELY (itemno < file->n_hash_items)
+    {
+      struct gvdb_hash_item *item = &file->hash_items[itemno];
+
+      if (hash_value == (guint32_from_le (item->hash_value) & ~(1u << 31)))
+        if G_LIKELY (gvdb_table_check_name (file, item, key, key_length))
+          if G_LIKELY (item->type == type)
+            return item;
+
+      if (guint32_from_le (item->hash_value) & (1u << 31))
+        return NULL;
+
+      itemno++;
+    }
+
+  return NULL;
+}
+
+/**
+ * gvdb_table_list:
+ * @file: a #GvdbTable
+ * @key: a string
+ * @returns: a %NULL-terminated string array
+ *
+ * List all of the keys that appear below @key.  The nesting of keys
+ * within the hash file is defined by the program that created the hash
+ * file.  One thing is constant: each item in the returned array can be
+ * concatenated to @key to obtain the full name of that key.
+ *
+ * It is not possible to tell from this function if a given key is
+ * itself a path, a value, or another hash table; you are expected to
+ * know this for yourself.
+ *
+ * You should call g_strfreev() on the return result when you no longer
+ * require it.
+ **/
+gchar **
+gvdb_table_list (GvdbTable   *file,
+                 const gchar *key)
+{
+  const struct gvdb_hash_item *item;
+  const guint32_le *list;
+  gchar **strv;
+  gsize size;
+  gint i;
+
+  if ((item = gvdb_table_lookup (file, key, 'L')) == NULL)
+    return NULL;
+
+  list = gvdb_table_dereference (file, &item->value.pointer, 4, &size);
+
+  if G_UNLIKELY (list == NULL || size % 4)
+    return NULL;
+
+  size /= 4;
+
+  strv = g_new (gchar *, size + 1);
+  for (i = 0; i < size; i++)
+    {
+      guint32 itemno = guint32_from_le (list[i]);
+
+      if (itemno < file->n_hash_items)
+        {
+          const struct gvdb_hash_item *item;
+          const gchar *string;
+          gsize strsize;
+
+          item = file->hash_items + itemno;
+
+          string = gvdb_table_item_get_key (file, item, &strsize);
+
+          if (string != NULL)
+            strv[i] = g_strndup (string, strsize);
+          else
+            strv[i] = g_malloc0 (1);
+        }
+      else
+        strv[i] = g_malloc0 (1);
+    }
+
+  strv[i] = NULL;
+
+  return strv;
+}
+
+/**
+ * gvdb_table_get_value:
+ * @file: a #GvdbTable
+ * @key: a string
+ * @options: a pointer to a #GVariant, or %NULL
+ * @returns: a #GVariant, or %NULL
+ *
+ * Looks up a value named @key in @file.
+ *
+ * If the value is not found then %NULL is returned.  Otherwise, a new
+ * #GVariant instance is returned.  The #GVariant does not depend on the
+ * continued existence of @file.
+ *
+ * If @options is non-%NULL then it will be set either to %NULL in the
+ * case of no options or a #GVariant containing a dictionary mapping
+ * strings to variants.
+ *
+ * You should call g_variant_unref() on the return result when you no
+ * longer require it.
+ **/
+GVariant *
+gvdb_table_get_value (GvdbTable    *file,
+                      const gchar  *key,
+                      GVariant    **options)
+{
+  const struct gvdb_hash_item *item;
+  GVariant *variant, *value;
+  gconstpointer data;
+  gsize size;
+
+  if ((item = gvdb_table_lookup (file, key, 'v')) == NULL)
+    return NULL;
+
+  data = gvdb_table_dereference (file, &item->value.pointer, 8, &size);
+
+  if G_UNLIKELY (data == NULL)
+    return NULL;
+
+  variant = g_variant_new_from_data (G_VARIANT_TYPE_VARIANT,
+                                     data, size, file->trusted,
+                                     (GDestroyNotify) g_mapped_file_unref,
+                                     g_mapped_file_ref (file->mapped));
+  value = g_variant_get_variant (variant);
+  g_variant_unref (variant);
+
+  if (options != NULL)
+    {
+      data = gvdb_table_dereference (file, &item->options, 8, &size);
+
+      if (data != NULL || size > 0)
+        {
+          *options = g_variant_new_from_data (G_VARIANT_TYPE ("a{sv}"),
+                                              data, size, file->trusted,
+                                              (GDestroyNotify) g_mapped_file_unref,
+                                              g_mapped_file_ref (file->mapped));
+          g_variant_ref_sink (*options);
+        }
+      else
+        *options = NULL;
+    }
+
+  return value;
+}
+
+/**
+ * gvdb_table_get_hash:
+ * @file: a #GvdbTable
+ * @key: a string
+ * @returns: a new #GvdbTable, or %NULL
+ *
+ * Looks up the hash table named @key in @file.
+ *
+ * The toplevel hash table in a #GvdbTable can contain reference to
+ * child hash tables (and those can contain further references...).
+ *
+ * If @key is not found in @file then %NULL is returned.  Otherwise, a
+ * new #GvdbTable is returned, referring to the child hashtable as
+ * contained in the file.  This newly-created #GvdbTable does not depend
+ * on the continued existence of @file.
+ *
+ * You should call gvdb_table_unref() on the return result when you no
+ * longer require it.
+ **/
+GvdbTable *
+gvdb_table_get_hash (GvdbTable   *file,
+                     const gchar *key)
+{
+  const struct gvdb_hash_item *item;
+  GvdbTable *new;
+
+  item = gvdb_table_lookup (file, key, 'H');
+
+  if (item == NULL)
+    return NULL;
+
+  new = g_slice_new0 (GvdbTable);
+  new->mapped = g_mapped_file_ref (file->mapped);
+  new->trusted = file->trusted;
+  new->data = file->data;
+  new->size = file->size;
+  new->ref_count = 1;
+
+  gvdb_table_setup_root (new, &item->value.pointer);
+
+  return new;
+}
+
+/**
+ * gvdb_table_ref:
+ * @file: a #GvdbTable
+ * @returns: a new reference on @file
+ *
+ * Increases the reference count on @file.
+ **/
+GvdbTable *
+gvdb_table_ref (GvdbTable *file)
+{
+  g_atomic_int_inc (&file->ref_count);
+
+  return file;
+}
+
+/**
+ * gvdb_table_unref:
+ * @file: a #GvdbTable
+ *
+ * Decreases the reference count on @file, possibly freeing it.
+ *
+ * Since: 2.26
+ **/
+void
+gvdb_table_unref (GvdbTable *file)
+{
+  if (g_atomic_int_dec_and_test (&file->ref_count))
+    {
+      g_mapped_file_unref (file->mapped);
+      g_slice_free (GvdbTable, file);
+    }
+}

gio/gvdb/gvdb-reader.h

@@ -0,0 +1,47 @@
+/*
+ * Copyright © 2010 Codethink Limited
+ *
+ * This 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 of the licence, or (at your option) any later version.
+ *
+ * This 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 this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __gvdb_reader_h__
+#define __gvdb_reader_h__
+
+#include <glib.h>
+
+typedef struct _GvdbTable GvdbTable;
+
+G_GNUC_INTERNAL
+GvdbTable *             gvdb_table_new                                  (const gchar  *filename,
+                                                                         gboolean      trusted,
+                                                                         GError      **error);
+G_GNUC_INTERNAL
+GvdbTable *             gvdb_table_ref                                  (GvdbTable    *table);
+G_GNUC_INTERNAL
+void                    gvdb_table_unref                                (GvdbTable    *table);
+
+G_GNUC_INTERNAL
+gchar **                gvdb_table_list                                 (GvdbTable    *table,
+                                                                         const gchar  *key);
+G_GNUC_INTERNAL
+GvdbTable *             gvdb_table_get_table                            (GvdbTable    *table,
+                                                                         const gchar  *key);
+G_GNUC_INTERNAL
+GVariant *              gvdb_table_get_value                            (GvdbTable    *table,
+                                                                         const gchar  *key,
+                                                                         GVariant    **options);
+
+#endif /* __gvdb_reader_h__ */