githubmirror/libxmlb

src/xb-silo.c
1 883 строки48 KB
Chun-wei Fan
Do not inline shared code
26 сен 2023, 17:04
26 сен 2023, 17:040826b18
/*
 * Copyright (C) 2018 Richard Hughes <richard@hughsie.com>
 *
 * SPDX-License-Identifier: LGPL-2.1+
 */

/**
 * SECTION:xb-silo
 * @title: XbSilo
 * @include: xmlb.h
 * @stability: Stable
 * @short_description: A read-only store of parsed XML data
 *
 * #XbSilo provides read-only access and querying of a previously parsed blob
 * of XML data.
 *
 * All signal emissions from #XbSilo (currently only #GObject::notify emissions)
 * will happen in the #GMainContext which is the thread default when the #XbSilo
 * is constructed.
 *
 * This #GMainContext must be iterated for file monitoring using
 * xb_silo_watch_file() to function correctly.
 */

#define G_LOG_DOMAIN "XbSilo"

#include "config.h"

#include <gio/gio.h>
#include <glib-object.h>
#include <string.h>

#ifdef HAVE_LIBSTEMMER
#include <libstemmer.h>
#endif

#include "xb-builder.h"
#include "xb-common-private.h"
#include "xb-machine-private.h"
#include "xb-node-private.h"
#include "xb-opcode-private.h"
#include "xb-silo-node.h"
#include "xb-stack-private.h"
#include "xb-string-private.h"

typedef struct {
	GMappedFile *mmap;
	gchar *guid;
	gboolean valid;
	GBytes *blob;
	const guint8 *data; /* pointers into ->blob */
	guint32 datasz;
	guint32 strtab;
	GHashTable *strtab_tags;
	GHashTable *strindex;
	gboolean enable_node_cache;
	GHashTable *nodes; /* (mutex nodes_mutex) */
	GMutex nodes_mutex;
	GHashTable *file_monitors; /* (element-type GFile XbSiloFileMonitorItem) (mutex
				      file_monitors_mutex) */
	GMutex file_monitors_mutex;
	XbMachine *machine;
	XbSiloProfileFlags profile_flags;
	GString *profile_str;
	GRWLock query_cache_mutex;
	GHashTable *query_cache;
	GMainContext *context; /* (owned) */
#ifdef HAVE_LIBSTEMMER
	struct sb_stemmer *stemmer_ctx; /* lazy loaded */
	GMutex stemmer_mutex;
#endif
} XbSiloPrivate;

typedef struct {
	GFileMonitor *file_monitor;
	gulong file_monitor_id;
} XbSiloFileMonitorItem;

G_DEFINE_TYPE_WITH_PRIVATE(XbSilo, xb_silo, G_TYPE_OBJECT)
#define GET_PRIVATE(o) (xb_silo_get_instance_private(o))

typedef enum {
	PROP_GUID = 1,
	PROP_VALID,
	PROP_ENABLE_NODE_CACHE,
} XbSiloProperty;

static GParamSpec *obj_props[PROP_ENABLE_NODE_CACHE + 1] = {
    NULL,
};

/* private */
GTimer *
xb_silo_start_profile(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);

	/* nothing to do; g_timer_new() does a syscall to clock_gettime() which
	 * is best avoided if not needed */
	if (!priv->profile_flags)
		return NULL;

	return g_timer_new();
}

/* private */
void
xb_silo_add_profile(XbSilo *self, GTimer *timer, const gchar *fmt, ...)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	va_list args;
	g_autoptr(GString) str = NULL;

	/* nothing to do */
	if (!priv->profile_flags)
		return;

	str = g_string_new("");

	/* add duration */
	if (timer != NULL) {
		g_string_append_printf(str, "%.2fms", g_timer_elapsed(timer, NULL) * 1000);
		for (guint i = str->len; i < 12; i++)
			g_string_append(str, " ");
	}

	/* add varargs */
	va_start(args, fmt);
	g_string_append_vprintf(str, fmt, args);
	va_end(args);

	/* do the right thing */
	if (priv->profile_flags & XB_SILO_PROFILE_FLAG_DEBUG)
		g_debug("%s", str->str);
	if (priv->profile_flags & XB_SILO_PROFILE_FLAG_APPEND)
		g_string_append_printf(priv->profile_str, "%s\n", str->str);

	/* reset automatically */
	if (timer != NULL)
		g_timer_reset(timer);
}

/* private */
static gchar *
xb_silo_stem(XbSilo *self, const gchar *value)
{
#ifdef HAVE_LIBSTEMMER
	XbSiloPrivate *priv = GET_PRIVATE(self);
	const gchar *tmp;
	gsize len_dst;
	gsize len_src;
	g_autofree gchar *value_casefold = NULL;
	g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->stemmer_mutex);

	g_return_val_if_fail(locker != NULL, NULL);

	/* not enabled */
	value_casefold = g_utf8_casefold(value, -1);
	if (priv->stemmer_ctx == NULL)
		priv->stemmer_ctx = sb_stemmer_new("en", NULL);

	/* stem */
	len_src = strlen(value_casefold);
	tmp = (const gchar *)sb_stemmer_stem(priv->stemmer_ctx,
					     (guchar *)value_casefold,
					     (gint)len_src);
	len_dst = (gsize)sb_stemmer_length(priv->stemmer_ctx);
	if (len_src == len_dst)
		return g_steal_pointer(&value_casefold);
	return g_strndup(tmp, len_dst);
#else
	return g_utf8_casefold(value, -1);
#endif
}

/* private */
const gchar *
xb_silo_from_strtab(XbSilo *self, guint32 offset)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	if (offset == XB_SILO_UNSET)
		return NULL;
	if (offset >= priv->datasz - priv->strtab) {
		g_critical("strtab+offset is outside the data range for %u", offset);
		return NULL;
	}
	return (const gchar *)(priv->data + priv->strtab + offset);
}

/* private */
void
xb_silo_strtab_index_insert(XbSilo *self, guint32 offset)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	const gchar *tmp;

	/* get the string version */
	tmp = xb_silo_from_strtab(self, offset);
	if (tmp == NULL)
		return;
	if (g_hash_table_lookup(priv->strindex, tmp) != NULL)
		return;
	g_hash_table_insert(priv->strindex, (gpointer)tmp, GUINT_TO_POINTER(offset));
}

/* private */
guint32
xb_silo_strtab_index_lookup(XbSilo *self, const gchar *str)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	gpointer val = NULL;
	if (!g_hash_table_lookup_extended(priv->strindex, str, NULL, &val))
		return XB_SILO_UNSET;
	return GPOINTER_TO_INT(val);
}

/* private */
XbSiloNode *
xb_silo_get_node(XbSilo *self, guint32 off)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	return (XbSiloNode *)(priv->data + off);
}

/* private */
guint32
xb_silo_get_offset_for_node(XbSilo *self, XbSiloNode *n)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	return ((const guint8 *)n) - priv->data;
}

/* private */
guint32
xb_silo_get_strtab(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	return priv->strtab;
}

/* private */
XbSiloNode *
xb_silo_get_root_node(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	if (priv->blob == NULL)
		return NULL;
	if (g_bytes_get_size(priv->blob) <= sizeof(XbSiloHeader))
		return NULL;
	return xb_silo_get_node(self, sizeof(XbSiloHeader));
}

/* private */
XbSiloNode *
xb_silo_get_parent_node(XbSilo *self, XbSiloNode *n)
{
	if (n->parent == 0x0)
		return NULL;
	return xb_silo_get_node(self, n->parent);
}

/* private */
XbSiloNode *
xb_silo_get_next_node(XbSilo *self, XbSiloNode *n)
{
	if (n->next == 0x0)
		return NULL;
	return xb_silo_get_node(self, n->next);
}

/* private */
XbSiloNode *
xb_silo_get_child_node(XbSilo *self, XbSiloNode *n)
{
	XbSiloNode *c;
	guint32 off = xb_silo_get_offset_for_node(self, n);
	off += xb_silo_node_get_size(n);

	/* check for sentinel */
	c = xb_silo_get_node(self, off);
	if (!xb_silo_node_has_flag(c, XB_SILO_NODE_FLAG_IS_ELEMENT))
		return NULL;
	return c;
}

/**
 * xb_silo_get_root:
 * @self: a #XbSilo
 *
 * Gets the root node for the silo. (MIGHT BE MORE).
 *
 * Returns: (transfer full): A #XbNode, or %NULL for an error
 *
 * Since: 0.1.0
 **/
XbNode *
xb_silo_get_root(XbSilo *self)
{
	g_return_val_if_fail(XB_IS_SILO(self), NULL);
	return xb_silo_create_node(self, xb_silo_get_root_node(self), FALSE);
}

/* private */
guint32
xb_silo_get_strtab_idx(XbSilo *self, const gchar *element)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	gpointer value = NULL;
	if (!g_hash_table_lookup_extended(priv->strtab_tags, element, NULL, &value))
		return XB_SILO_UNSET;
	return GPOINTER_TO_UINT(value);
}

/**
 * xb_silo_to_string:
 * @self: a #XbSilo
 * @error: the #GError, or %NULL
 *
 * Converts the silo to an internal string representation. This is only
 * really useful for debugging #XbSilo itself.
 *
 * Returns: A string, or %NULL for an error
 *
 * Since: 0.1.0
 **/
gchar *
xb_silo_to_string(XbSilo *self, GError **error)
{
	guint32 off = sizeof(XbSiloHeader);
	XbSiloPrivate *priv = GET_PRIVATE(self);
	XbSiloHeader *hdr = (XbSiloHeader *)priv->data;
	g_autoptr(GString) str = g_string_new(NULL);

	g_return_val_if_fail(XB_IS_SILO(self), NULL);
	g_return_val_if_fail(error == NULL || *error == NULL, NULL);

	/* sanity check */
	if (hdr->strtab > priv->datasz) {
		g_set_error_literal(error, G_IO_ERROR, G_IO_ERROR_INVALID_DATA, "strtab invalid");
		return NULL;
	}

	g_string_append_printf(str, "magic:        %08x\n", (guint)hdr->magic);
	g_string_append_printf(str, "guid:         %s\n", priv->guid);
	g_string_append_printf(str, "strtab:       @%" G_GUINT32_FORMAT "\n", hdr->strtab);
	g_string_append_printf(str, "strtab_ntags: %" G_GUINT16_FORMAT "\n", hdr->strtab_ntags);
	while (off < priv->strtab) {
		XbSiloNode *n = xb_silo_get_node(self, off);
		if (xb_silo_node_has_flag(n, XB_SILO_NODE_FLAG_IS_ELEMENT)) {
			guint32 idx;
			g_string_append_printf(str, "NODE @%" G_GUINT32_FORMAT "\n", off);
			g_string_append_printf(str,
					       "size:         %" G_GUINT32_FORMAT "\n",
					       xb_silo_node_get_size(n));
			g_string_append_printf(str,
					       "flags:        %x\n",
					       xb_silo_node_get_flags(n));
			g_string_append_printf(str,
					       "element_name: %s [%03u]\n",
					       xb_silo_from_strtab(self, n->element_name),
					       n->element_name);
			g_string_append_printf(str,
					       "next:         %" G_GUINT32_FORMAT "\n",
					       n->next);
			g_string_append_printf(str,
					       "parent:       %" G_GUINT32_FORMAT "\n",
					       n->parent);
			idx = xb_silo_node_get_text_idx(n);
			if (idx != XB_SILO_UNSET) {
				g_string_append_printf(str,
						       "text:         %s [%03u]\n",
						       xb_silo_from_strtab(self, idx),
						       idx);
			}
			idx = xb_silo_node_get_tail_idx(n);
			if (idx != XB_SILO_UNSET) {
				g_string_append_printf(str,
						       "tail:         %s [%03u]\n",
						       xb_silo_from_strtab(self, idx),
						       idx);
			}
			for (guint8 i = 0; i < xb_silo_node_get_attr_count(n); i++) {
				XbSiloNodeAttr *a = xb_silo_node_get_attr(n, i);
				g_string_append_printf(str,
						       "attr_name:    %s [%03u]\n",
						       xb_silo_from_strtab(self, a->attr_name),
						       a->attr_name);
				g_string_append_printf(str,
						       "attr_value:   %s [%03u]\n",
						       xb_silo_from_strtab(self, a->attr_value),
						       a->attr_value);
			}
			for (guint8 i = 0; i < xb_silo_node_get_token_count(n); i++) {
				guint32 idx_tmp = xb_silo_node_get_token_idx(n, i);
				g_string_append_printf(str,
						       "token:        %s [%03u]\n",
						       xb_silo_from_strtab(self, idx_tmp),
						       idx_tmp);
			}
		} else {
			g_string_append_printf(str, "SENT @%" G_GUINT32_FORMAT "\n", off);
		}
		off += xb_silo_node_get_size(n);
	}

	/* add strtab */
	g_string_append_printf(str, "STRTAB @%" G_GUINT32_FORMAT "\n", hdr->strtab);
	for (off = 0; off < priv->datasz - hdr->strtab;) {
		const gchar *tmp = xb_silo_from_strtab(self, off);
		if (tmp == NULL)
			break;
		g_string_append_printf(str, "[%03u]: %s\n", off, tmp);
		off += strlen(tmp) + 1;
	}

	/* success */
	return g_string_free(g_steal_pointer(&str), FALSE);
}

/* private */
const gchar *
xb_silo_get_node_text(XbSilo *self, XbSiloNode *n)
{
	guint32 idx = xb_silo_node_get_text_idx(n);
	if (idx == XB_SILO_UNSET)
		return NULL;
	return xb_silo_from_strtab(self, idx);
}

/* private */
const gchar *
xb_silo_get_node_tail(XbSilo *self, XbSiloNode *n)
{
	guint idx = xb_silo_node_get_tail_idx(n);
	if (idx == XB_SILO_UNSET)
		return NULL;
	return xb_silo_from_strtab(self, idx);
}

/* private */
const gchar *
xb_silo_get_node_element(XbSilo *self, XbSiloNode *n)
{
	return xb_silo_from_strtab(self, n->element_name);
}

/* private */
XbSiloNodeAttr *
xb_silo_get_node_attr_by_str(XbSilo *self, XbSiloNode *n, const gchar *name)
{
	guint8 attr_count;

	/* calculate offset to first attribute */
	attr_count = xb_silo_node_get_attr_count(n);
	for (guint8 i = 0; i < attr_count; i++) {
		XbSiloNodeAttr *a = xb_silo_node_get_attr(n, i);
		if (g_strcmp0(xb_silo_from_strtab(self, a->attr_name), name) == 0)
			return a;
	}

	/* nothing matched */
	return NULL;
}

static XbSiloNodeAttr *
xb_silo_node_get_attr_by_val(XbSilo *self, XbSiloNode *n, guint32 name)
{
	guint8 attr_count;

	/* calculate offset to first attribute */
	attr_count = xb_silo_node_get_attr_count(n);
	for (guint8 i = 0; i < attr_count; i++) {
		XbSiloNodeAttr *a = xb_silo_node_get_attr(n, i);
		if (a->attr_name == name)
			return a;
	}

	/* nothing matched */
	return NULL;
}

/**
 * xb_silo_get_size:
 * @self: a #XbSilo
 *
 * Gets the number of nodes in the silo.
 *
 * Returns: a integer, or 0 is an empty blob
 *
 * Since: 0.1.0
 **/
guint
xb_silo_get_size(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	guint32 off = sizeof(XbSiloHeader);
	guint nodes_cnt = 0;

	g_return_val_if_fail(XB_IS_SILO(self), 0);

	while (off < priv->strtab) {
		XbSiloNode *n = xb_silo_get_node(self, off);
		if (xb_silo_node_has_flag(n, XB_SILO_NODE_FLAG_IS_ELEMENT))
			nodes_cnt += 1;
		off += xb_silo_node_get_size(n);
	}

	/* success */
	return nodes_cnt;
}

/**
 * xb_silo_is_valid:
 * @self: a #XbSilo
 *
 * Checks is the silo is valid. The usual reason the silo is invalidated is
 * when the backing mmapped file has changed, or one of the imported files have
 * been modified.
 *
 * Returns: %TRUE if valid
 *
 * Since: 0.1.0
 **/
gboolean
xb_silo_is_valid(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	return priv->valid;
}

/* private */
gboolean
xb_silo_is_empty(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	return priv->strtab == sizeof(XbSiloHeader);
}

typedef struct {
	XbSilo *silo;	   /* (owned) */
	GParamSpec *pspec; /* (owned) */
} SiloNotifyData;

static void
silo_notify_data_free(SiloNotifyData *data)
{
	g_clear_object(&data->silo);
	g_clear_pointer(&data->pspec, g_param_spec_unref);
	g_free(data);
}

G_DEFINE_AUTOPTR_CLEANUP_FUNC(SiloNotifyData, silo_notify_data_free)

static gboolean
silo_notify_cb(gpointer user_data)
{
	g_autoptr(SiloNotifyData) data = g_steal_pointer(&user_data);

	g_object_notify_by_pspec(G_OBJECT(data->silo), data->pspec);

	return G_SOURCE_REMOVE;
}

/* Like g_object_notify(), but ensure that the signal is emitted in XbSilo.context. */
static void
silo_notify(XbSilo *self, GParamSpec *pspec)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_autoptr(SiloNotifyData) data = NULL;

	data = g_new0(SiloNotifyData, 1);
	data->silo = g_object_ref(self);
	data->pspec = g_param_spec_ref(pspec);

	g_main_context_invoke(priv->context, silo_notify_cb, g_steal_pointer(&data));
}

/**
 * xb_silo_invalidate:
 * @self: a #XbSilo
 *
 * Invalidates a silo. Future calls xb_silo_is_valid() will return %FALSE.
 *
 * Since: 0.1.1
 **/
void
xb_silo_invalidate(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	if (!priv->valid)
		return;
	priv->valid = FALSE;
	silo_notify(self, obj_props[PROP_VALID]);
}

/* private */
void
xb_silo_uninvalidate(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	if (priv->valid)
		return;
	priv->valid = TRUE;
	silo_notify(self, obj_props[PROP_VALID]);
}

/* private */
guint
xb_silo_get_node_depth(XbSilo *self, XbSiloNode *n)
{
	guint depth = 0;
	while (n->parent != 0) {
		depth++;
		n = xb_silo_get_node(self, n->parent);
	}
	return depth;
}

/**
 * xb_silo_get_bytes:
 * @self: a #XbSilo
 *
 * Gets the backing object that created the blob.
 *
 * You should never *ever* modify this data.
 *
 * Returns: (transfer full): A #GBytes, or %NULL if never set
 *
 * Since: 0.1.0
 **/
GBytes *
xb_silo_get_bytes(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_val_if_fail(XB_IS_SILO(self), NULL);
	if (priv->blob == NULL)
		return NULL;
	return g_bytes_ref(priv->blob);
}

/**
 * xb_silo_get_guid:
 * @self: a #XbSilo
 *
 * Gets the GUID used to identify this silo.
 *
 * Returns: a string, otherwise %NULL
 *
 * Since: 0.1.0
 **/
const gchar *
xb_silo_get_guid(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_val_if_fail(XB_IS_SILO(self), NULL);
	return priv->guid;
}

/* private */
XbMachine *
xb_silo_get_machine(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_val_if_fail(XB_IS_SILO(self), NULL);
	return priv->machine;
}

/**
 * xb_silo_load_from_bytes:
 * @self: a #XbSilo
 * @blob: a #GBytes
 * @flags: #XbSiloLoadFlags, e.g. %XB_SILO_LOAD_FLAG_NONE
 * @error: the #GError, or %NULL
 *
 * Loads a silo from memory location.
 *
 * Returns: %TRUE for success, otherwise @error is set.
 *
 * Since: 0.1.0
 **/
gboolean
xb_silo_load_from_bytes(XbSilo *self, GBytes *blob, XbSiloLoadFlags flags, GError **error)
{
	XbGuid guid_tmp;
	XbSiloHeader *hdr;
	XbSiloPrivate *priv = GET_PRIVATE(self);
	gsize sz = 0;
	guint32 off = 0;
	g_autoptr(GMutexLocker) locker = NULL;
	g_autoptr(GTimer) timer = xb_silo_start_profile(self);

	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	g_return_val_if_fail(blob != NULL, FALSE);
	g_return_val_if_fail(error == NULL || *error == NULL, FALSE);

	/* no longer valid */
	if (priv->enable_node_cache) {
		locker = g_mutex_locker_new(&priv->nodes_mutex);
		if (priv->nodes != NULL)
			g_hash_table_remove_all(priv->nodes);
	}

	g_hash_table_remove_all(priv->strtab_tags);
	g_clear_pointer(&priv->guid, g_free);

	/* refcount internally */
	if (priv->blob != NULL)
		g_bytes_unref(priv->blob);
	priv->blob = g_bytes_ref(blob);

	/* update pointers into blob */
	priv->data = g_bytes_get_data(priv->blob, &sz);
	priv->datasz = (guint32)sz;

	/* check size */
	if (sz < sizeof(XbSiloHeader)) {
		g_set_error_literal(error, G_IO_ERROR, G_IO_ERROR_INVALID_DATA, "blob too small");
		return FALSE;
	}

	/* check header magic */
	hdr = (XbSiloHeader *)priv->data;
	if ((flags & XB_SILO_LOAD_FLAG_NO_MAGIC) == 0) {
		if (hdr->magic != XB_SILO_MAGIC_BYTES) {
			g_set_error_literal(error,
					    G_IO_ERROR,
					    G_IO_ERROR_INVALID_DATA,
					    "magic incorrect");
			return FALSE;
		}
		if (hdr->version != XB_SILO_VERSION) {
			g_set_error(error,
				    G_IO_ERROR,
				    G_IO_ERROR_INVALID_DATA,
				    "version incorrect, got %u, expected %d",
				    hdr->version,
				    XB_SILO_VERSION);
			return FALSE;
		}
	}

	/* get GUID */
	memcpy(&guid_tmp, &hdr->guid, sizeof(guid_tmp));
	priv->guid = xb_guid_to_string(&guid_tmp);

	/* check strtab */
	priv->strtab = hdr->strtab;
	if (priv->strtab > priv->datasz) {
		g_set_error_literal(error, G_IO_ERROR, G_IO_ERROR_INVALID_DATA, "strtab incorrect");
		return FALSE;
	}

	/* load strtab_tags */
	for (guint16 i = 0; i < hdr->strtab_ntags; i++) {
		const gchar *tmp = xb_silo_from_strtab(self, off);
		if (tmp == NULL) {
			g_set_error_literal(error,
					    G_IO_ERROR,
					    G_IO_ERROR_INVALID_DATA,
					    "strtab_ntags incorrect");
			return FALSE;
		}
		g_hash_table_insert(priv->strtab_tags, (gpointer)tmp, GUINT_TO_POINTER(off));
		off += strlen(tmp) + 1;
	}

	/* profile */
	xb_silo_add_profile(self, timer, "parse blob");

	/* success */
	priv->valid = TRUE;
	return TRUE;
}

/**
 * xb_silo_get_profile_string:
 * @self: a #XbSilo
 *
 * Returns the profiling data. This will only return profiling text if
 * xb_silo_set_profile_flags() was used with %XB_SILO_PROFILE_FLAG_APPEND.
 *
 * Returns: text profiling data
 *
 * Since: 0.1.1
 **/
const gchar *
xb_silo_get_profile_string(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_val_if_fail(XB_IS_SILO(self), NULL);
	return priv->profile_str->str;
}

/**
 * xb_silo_set_profile_flags:
 * @self: a #XbSilo
 * @profile_flags: some #XbSiloProfileFlags, e.g. %XB_SILO_PROFILE_FLAG_DEBUG
 *
 * Enables or disables the collection of profiling data.
 *
 * Since: 0.1.1
 **/
void
xb_silo_set_profile_flags(XbSilo *self, XbSiloProfileFlags profile_flags)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_if_fail(XB_IS_SILO(self));
	priv->profile_flags = profile_flags;

	/* proxy */
	if (profile_flags & XB_SILO_PROFILE_FLAG_OPTIMIZER) {
		xb_machine_set_debug_flags(priv->machine,
					   XB_MACHINE_DEBUG_FLAG_SHOW_OPTIMIZER |
					       XB_MACHINE_DEBUG_FLAG_SHOW_SLOW_PATH);
	}
}

/**
 * xb_silo_get_enable_node_cache:
 * @self: an #XbSilo
 *
 * Get #XbSilo:enable-node-cache.
 *
 * Since: 0.2.0
 */
gboolean
xb_silo_get_enable_node_cache(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	return priv->enable_node_cache;
}

/**
 * xb_silo_set_enable_node_cache:
 * @self: an #XbSilo
 * @enable_node_cache: %TRUE to enable the node cache, %FALSE otherwise
 *
 * Set #XbSilo:enable-node-cache.
 *
 * This is not thread-safe, and can only be called before the #XbSilo is passed
 * between threads.
 *
 * Since: 0.2.0
 */
void
xb_silo_set_enable_node_cache(XbSilo *self, gboolean enable_node_cache)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);

	g_return_if_fail(XB_IS_SILO(self));

	if (priv->enable_node_cache == enable_node_cache)
		return;

	priv->enable_node_cache = enable_node_cache;

	/* if disabling the cache, destroy any existing data structures;
	 * if enabling it, create them lazily when the first entry is cached
	 * (see xb_silo_create_node()) */
	if (!enable_node_cache) {
		g_clear_pointer(&priv->nodes, g_hash_table_unref);
	}

	silo_notify(self, obj_props[PROP_ENABLE_NODE_CACHE]);
}

/* private */
XbSiloProfileFlags
xb_silo_get_profile_flags(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	return priv->profile_flags;
}

/* This will be invoked in silo->context */
static void
xb_silo_watch_file_cb(GFileMonitor *monitor,
		      GFile *file,
		      GFile *other_file,
		      GFileMonitorEvent event_type,
		      gpointer user_data)
{
	XbSilo *silo = XB_SILO(user_data);
	g_autofree gchar *fn = g_file_get_path(file);
	g_autofree gchar *basename = g_file_get_basename(file);
	if (g_str_has_prefix(basename, "."))
		return;
	g_debug("%s changed, invalidating", fn);
	xb_silo_invalidate(silo);
}

typedef struct {
	XbSilo *silo; /* (owned) */
	GFile *file;  /* (owned) */
} WatchFileData;

static void
watch_file_data_free(WatchFileData *data)
{
	g_clear_object(&data->silo);
	g_clear_object(&data->file);
	g_free(data);
}

G_DEFINE_AUTOPTR_CLEANUP_FUNC(WatchFileData, watch_file_data_free)

static gboolean
watch_file_cb(gpointer user_data);

/**
 * xb_silo_watch_file:
 * @self: a #XbSilo
 * @file: a #GFile
 * @cancellable: a #GCancellable, or %NULL
 * @error: the #GError, or %NULL
 *
 * Adds a file monitor to the silo. If the file or directory for @file changes
 * then the silo will be invalidated.
 *
 * The monitor will internally use the #GMainContext which was the thread
 * default when the #XbSilo was created, so that #GMainContext must be iterated
 * for monitoring to work.
 *
 * Returns: %TRUE for success, otherwise @error is set.
 *
 * Since: 0.1.0
 **/
gboolean
xb_silo_watch_file(XbSilo *self, GFile *file, GCancellable *cancellable, GError **error)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_autoptr(WatchFileData) data = NULL;

	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	g_return_val_if_fail(cancellable == NULL || G_IS_CANCELLABLE(cancellable), FALSE);
	g_return_val_if_fail(error == NULL || *error == NULL, FALSE);

	/* return if cancelled; this is basically the only failure mode of
	 * g_file_monitor() for local files, and this function shouldn’t really
	 * be called on non-local files */
	if (g_cancellable_set_error_if_cancelled(cancellable, error))
		return FALSE;

	data = g_new0(WatchFileData, 1);
	data->silo = g_object_ref(self);
	data->file = g_object_ref(file);

	g_main_context_invoke(priv->context, watch_file_cb, g_steal_pointer(&data));

	return TRUE;
}

static gboolean
watch_file_cb(gpointer user_data)
{
	g_autoptr(WatchFileData) data = g_steal_pointer(&user_data);
	XbSilo *self = data->silo;
	GFile *file = data->file;
	XbSiloFileMonitorItem *item;
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_autoptr(GFileMonitor) file_monitor = NULL;
	g_autoptr(GError) error_local = NULL;
	g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->file_monitors_mutex);

	g_return_val_if_fail(locker != NULL, FALSE);

	/* already exists */
	item = g_hash_table_lookup(priv->file_monitors, file);
	if (item != NULL)
		return G_SOURCE_REMOVE;

	/* try to create */
	file_monitor = g_file_monitor(file, G_FILE_MONITOR_NONE, NULL, &error_local);
	if (file_monitor == NULL) {
		g_warning("Error adding file monitor: %s", error_local->message);
		return G_SOURCE_REMOVE;
	}

	g_file_monitor_set_rate_limit(file_monitor, 20);

	/* add */
	item = g_slice_new0(XbSiloFileMonitorItem);
	item->file_monitor = g_object_ref(file_monitor);
	item->file_monitor_id =
	    g_signal_connect(file_monitor, "changed", G_CALLBACK(xb_silo_watch_file_cb), self);
	g_hash_table_insert(priv->file_monitors, g_object_ref(file), item);

	return G_SOURCE_REMOVE;
}

/**
 * xb_silo_load_from_file:
 * @self: a #XbSilo
 * @file: a #GFile
 * @flags: #XbSiloLoadFlags, e.g. %XB_SILO_LOAD_FLAG_NONE
 * @cancellable: a #GCancellable, or %NULL
 * @error: the #GError, or %NULL
 *
 * Loads a silo from file.
 *
 * Returns: %TRUE for success, otherwise @error is set.
 *
 * Since: 0.1.0
 **/
gboolean
xb_silo_load_from_file(XbSilo *self,
		       GFile *file,
		       XbSiloLoadFlags flags,
		       GCancellable *cancellable,
		       GError **error)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_autofree gchar *fn = NULL;
	g_autoptr(GBytes) blob = NULL;
	g_autoptr(GTimer) timer = xb_silo_start_profile(self);
	g_autoptr(GMutexLocker) file_monitors_locker =
	    g_mutex_locker_new(&priv->file_monitors_mutex);

	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	g_return_val_if_fail(G_IS_FILE(file), FALSE);
	g_return_val_if_fail(cancellable == NULL || G_IS_CANCELLABLE(cancellable), FALSE);
	g_return_val_if_fail(error == NULL || *error == NULL, FALSE);

	/* no longer valid (@nodes is cleared by xb_silo_load_from_bytes()) */
	g_hash_table_remove_all(priv->file_monitors);
	g_clear_pointer(&file_monitors_locker, g_mutex_locker_free);

	g_hash_table_remove_all(priv->strtab_tags);
	g_clear_pointer(&priv->guid, g_free);
	g_clear_pointer(&priv->mmap, g_mapped_file_unref);

	fn = g_file_get_path(file);
	priv->mmap = g_mapped_file_new(fn, FALSE, error);
	if (priv->mmap == NULL)
		return FALSE;
	blob = g_mapped_file_get_bytes(priv->mmap);
	if (!xb_silo_load_from_bytes(self, blob, flags, error))
		return FALSE;

	/* watch file for changes */
	if (flags & XB_SILO_LOAD_FLAG_WATCH_BLOB) {
		if (!xb_silo_watch_file(self, file, cancellable, error))
			return FALSE;
	}

	/* success */
	xb_silo_add_profile(self, timer, "loaded file");
	return TRUE;
}

/**
 * xb_silo_save_to_file:
 * @self: a #XbSilo
 * @file: a #GFile
 * @cancellable: a #GCancellable, or %NULL
 * @error: the #GError, or %NULL
 *
 * Saves a silo to a file.
 *
 * Returns: %TRUE for success, otherwise @error is set.
 *
 * Since: 0.1.0
 **/
gboolean
xb_silo_save_to_file(XbSilo *self, GFile *file, GCancellable *cancellable, GError **error)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_autoptr(GFile) file_parent = NULL;
	g_autoptr(GTimer) timer = xb_silo_start_profile(self);

	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	g_return_val_if_fail(G_IS_FILE(file), FALSE);
	g_return_val_if_fail(cancellable == NULL || G_IS_CANCELLABLE(cancellable), FALSE);
	g_return_val_if_fail(error == NULL || *error == NULL, FALSE);

	/* invalid */
	if (priv->data == NULL) {
		g_set_error_literal(error,
				    G_IO_ERROR,
				    G_IO_ERROR_NOT_INITIALIZED,
				    "no data to save");
		return FALSE;
	}

	/* ensure parent directories exist */
	file_parent = g_file_get_parent(file);
	if (file_parent != NULL && !g_file_query_exists(file_parent, cancellable)) {
		if (!g_file_make_directory_with_parents(file_parent, cancellable, error))
			return FALSE;
	}

	/* save and then rename */
	if (!xb_file_set_contents(file, priv->data, (gsize)priv->datasz, cancellable, error))
		return FALSE;

	xb_silo_add_profile(self, timer, "save file");
	return TRUE;
}

/**
 * xb_silo_new_from_xml:
 * @xml: XML string
 * @error: the #GError, or %NULL
 *
 * Creates a new silo from an XML string.
 *
 * Returns: a new #XbSilo, or %NULL
 *
 * Since: 0.1.0
 **/
XbSilo *
xb_silo_new_from_xml(const gchar *xml, GError **error)
{
	g_autoptr(XbBuilder) builder = xb_builder_new();
	g_autoptr(XbBuilderSource) source = xb_builder_source_new();
	g_return_val_if_fail(xml != NULL, NULL);
	g_return_val_if_fail(error == NULL || *error == NULL, NULL);
	if (!xb_builder_source_load_xml(source, xml, XB_BUILDER_SOURCE_FLAG_NONE, error))
		return NULL;
	xb_builder_import_source(builder, source);
	return xb_builder_compile(builder, XB_BUILDER_COMPILE_FLAG_NONE, NULL, error);
}

/* private */
XbNode *
xb_silo_create_node(XbSilo *self, XbSiloNode *sn, gboolean force_node_cache)
{
	XbNode *n;
	XbSiloPrivate *priv = GET_PRIVATE(self);
	g_autoptr(GMutexLocker) locker = NULL;

	/* the cache should only be enabled/disabled before threads are
	 * spawned, so `priv->enable_node_cache` can be accessed unlocked */
	if (!priv->enable_node_cache && !force_node_cache)
		return xb_node_new(self, sn);

	locker = g_mutex_locker_new(&priv->nodes_mutex);

	/* ensure the cache exists */
	if (priv->nodes == NULL)
		priv->nodes = g_hash_table_new_full(g_direct_hash,
						    g_direct_equal,
						    NULL,
						    (GDestroyNotify)g_object_unref);

	/* does already exist */
	n = g_hash_table_lookup(priv->nodes, sn);
	if (n != NULL)
		return g_object_ref(n);

	/* create and add */
	n = xb_node_new(self, sn);
	g_hash_table_insert(priv->nodes, sn, g_object_ref(n));
	return n;
}

/* Push two opcodes onto the stack with appropriate rollback on failure. */
static gboolean
_xb_stack_push_two(XbStack *opcodes, XbOpcode **op1, XbOpcode **op2, GError **error)
{
	if (!xb_stack_push(opcodes, op1, error))
		return FALSE;
	if (!xb_stack_push(opcodes, op2, error)) {
		xb_stack_pop(opcodes, NULL, NULL);
		return FALSE;
	}
	return TRUE;
}

/* convert [2] to position()=2 */
static gboolean
xb_silo_machine_fixup_position_cb(XbMachine *self,
				  XbStack *opcodes,
				  gpointer user_data,
				  GError **error)
{
	XbOpcode *op1;
	XbOpcode *op2;
	XbOpcode *tail = xb_stack_peek_tail(opcodes);

	if (!_xb_stack_push_two(opcodes, &op1, &op2, error))
		return FALSE;

	xb_machine_opcode_func_init(self, op1, "position");
	xb_machine_opcode_func_init(self, op2, "eq");

	/* always exists, but maybe a @level would be cleaner */
	if (tail != NULL) {
		xb_opcode_set_level(op1, _xb_opcode_get_level(tail));
		xb_opcode_set_level(op2, _xb_opcode_get_level(tail));
	}

	return TRUE;
}

/* convert "'type' attr()" -> "'type' attr() '(null)' ne()" */
static gboolean
xb_silo_machine_fixup_attr_exists_cb(XbMachine *self,
				     XbStack *opcodes,
				     gpointer user_data,
				     GError **error)
{
	XbOpcode *op1;
	XbOpcode *op2;
	XbOpcode *tail = xb_stack_peek_tail(opcodes);

	if (!_xb_stack_push_two(opcodes, &op1, &op2, error))
		return FALSE;

	xb_opcode_text_init_static(op1, NULL);
	xb_machine_opcode_func_init(self, op2, "ne");

	/* always exists, but maybe a @level would be cleaner */
	if (tail != NULL) {
		xb_opcode_set_level(op1, _xb_opcode_get_level(tail));
		xb_opcode_set_level(op2, _xb_opcode_get_level(tail));
	}

	return TRUE;
}

static gboolean
xb_silo_machine_fixup_attr_search_token_cb(XbMachine *self,
					   XbStack *opcodes,
					   gpointer user_data,
					   GError **error)
{
	XbOpcode op_func;
	XbOpcode op_text;
	XbOpcode op_search;
	XbOpcode *op_tmp;

	/* text() */
	if (!xb_machine_stack_pop(self, opcodes, &op_func, error))
		return FALSE;

	/* TEXT */
	if (!xb_machine_stack_pop(self, opcodes, &op_text, error))
		return FALSE;
	xb_machine_opcode_tokenize(self, &op_text);

	/* search() */
	if (!xb_machine_stack_pop(self, opcodes, &op_search, error))
		return FALSE;

	/* text() */
	if (!xb_machine_stack_push(self, opcodes, &op_tmp, error))
		return FALSE;
	*op_tmp = op_search;

	/* TEXT */
	if (!xb_machine_stack_push(self, opcodes, &op_tmp, error))
		return FALSE;
	*op_tmp = op_text;

	/* search() */
	if (!xb_machine_stack_push(self, opcodes, &op_tmp, error))
		return FALSE;
	*op_tmp = op_func;
	return TRUE;
}

static gboolean
xb_silo_machine_func_attr_cb(XbMachine *self,
			     XbStack *stack,
			     gboolean *result,
			     gpointer user_data,
			     gpointer exec_data,
			     GError **error)
{
	XbOpcode *op2;
	XbSiloNodeAttr *a;
	XbSilo *silo = XB_SILO(user_data);
	XbSiloQueryData *query_data = (XbSiloQueryData *)exec_data;
	g_auto(XbOpcode) op = XB_OPCODE_INIT();

	/* optimize pass */
	if (query_data == NULL) {
		g_set_error_literal(error,
				    G_IO_ERROR,
				    G_IO_ERROR_FAILED_HANDLED,
				    "cannot optimize: no silo to query");
		return FALSE;
	}

	if (!xb_machine_stack_pop(self, stack, &op, error))
		return FALSE;

	/* indexed string */
	if (xb_opcode_get_kind(&op) == XB_OPCODE_KIND_INDEXED_TEXT) {
		guint32 val = xb_opcode_get_val(&op);
		a = xb_silo_node_get_attr_by_val(silo, query_data->sn, val);
	} else {
		const gchar *str = xb_opcode_get_str(&op);
		a = xb_silo_get_node_attr_by_str(silo, query_data->sn, str);
	}
	if (a == NULL) {
		return xb_machine_stack_push_text_static(self, stack, NULL, error);
	}
	if (!xb_machine_stack_push(self, stack, &op2, error))
		return FALSE;
	xb_opcode_init(op2,
		       XB_OPCODE_KIND_INDEXED_TEXT,
		       xb_silo_from_strtab(silo, a->attr_value),
		       a->attr_value,
		       NULL);
	return TRUE;
}

static gboolean
xb_silo_machine_func_stem_cb(XbMachine *self,
			     XbStack *stack,
			     gboolean *result,
			     gpointer user_data,
			     gpointer exec_data,
			     GError **error)
{
	XbSilo *silo = XB_SILO(user_data);
	XbOpcode *head;
	const gchar *str;
	g_auto(XbOpcode) op = XB_OPCODE_INIT();

	head = xb_stack_peek_head(stack);
	if (head == NULL || !xb_opcode_cmp_str(head)) {
		g_set_error(error,
			    G_IO_ERROR,
			    G_IO_ERROR_NOT_SUPPORTED,
			    "%s type not supported",
			    (head != NULL) ? xb_opcode_kind_to_string(xb_opcode_get_kind(head))
					   : "(null)");
		return FALSE;
	}

	if (!xb_machine_stack_pop(self, stack, &op, error))
		return FALSE;

	/* TEXT */
	str = xb_opcode_get_str(&op);
	return xb_machine_stack_push_text_steal(self, stack, xb_silo_stem(silo, str), error);
}

static gboolean
xb_silo_machine_func_text_cb(XbMachine *self,
			     XbStack *stack,
			     gboolean *result,
			     gpointer user_data,
			     gpointer exec_data,
			     GError **error)
{
	XbSilo *silo = XB_SILO(user_data);
	XbSiloQueryData *query_data = (XbSiloQueryData *)exec_data;
	XbOpcode *op;
	guint8 token_count;

	/* optimize pass */
	if (query_data == NULL) {
		g_set_error_literal(error,
				    G_IO_ERROR,
				    G_IO_ERROR_FAILED_HANDLED,
				    "cannot optimize: no silo to query");
		return FALSE;
	}

	if (!xb_machine_stack_push(self, stack, &op, error))
		return FALSE;
	xb_opcode_init(op,
		       XB_OPCODE_KIND_INDEXED_TEXT,
		       xb_silo_get_node_text(silo, query_data->sn),
		       xb_silo_node_get_text_idx(query_data->sn),
		       NULL);

	/* use the fast token path even if there are no valid tokens */
	if (xb_silo_node_has_flag(query_data->sn, XB_SILO_NODE_FLAG_IS_TOKENIZED))
		xb_opcode_add_flag(op, XB_OPCODE_FLAG_TOKENIZED);

	/* add tokens */
	token_count = xb_silo_node_get_token_count(query_data->sn);
	for (guint i = 0; i < token_count; i++) {
		guint32 stridx = xb_silo_node_get_token_idx(query_data->sn, i);
		xb_opcode_append_token(op, xb_silo_from_strtab(silo, stridx));
	}

	return TRUE;
}

static gboolean
xb_silo_machine_func_tail_cb(XbMachine *self,
			     XbStack *stack,
			     gboolean *result,
			     gpointer user_data,
			     gpointer exec_data,
			     GError **error)
{
	XbSilo *silo = XB_SILO(user_data);
	XbSiloQueryData *query_data = (XbSiloQueryData *)exec_data;
	XbOpcode *op;

	/* optimize pass */
	if (query_data == NULL) {
		g_set_error_literal(error,
				    G_IO_ERROR,
				    G_IO_ERROR_FAILED_HANDLED,
				    "cannot optimize: no silo to query");
		return FALSE;
	}

	if (!xb_machine_stack_push(self, stack, &op, error))
		return FALSE;
	xb_opcode_init(op,
		       XB_OPCODE_KIND_INDEXED_TEXT,
		       xb_silo_get_node_tail(silo, query_data->sn),
		       xb_silo_node_get_tail_idx(query_data->sn),
		       NULL);
	return TRUE;
}

static gboolean
xb_silo_machine_func_first_cb(XbMachine *self,
			      XbStack *stack,
			      gboolean *result,
			      gpointer user_data,
			      gpointer exec_data,
			      GError **error)
{
	XbSiloQueryData *query_data = (XbSiloQueryData *)exec_data;

	/* optimize pass */
	if (query_data == NULL) {
		g_set_error_literal(error,
				    G_IO_ERROR,
				    G_IO_ERROR_FAILED_HANDLED,
				    "cannot optimize: no silo to query");
		return FALSE;
	}
	return xb_stack_push_bool(stack, query_data->position == 1, error);
}

static gboolean
xb_silo_machine_func_last_cb(XbMachine *self,
			     XbStack *stack,
			     gboolean *result,
			     gpointer user_data,
			     gpointer exec_data,
			     GError **error)
{
	XbSiloQueryData *query_data = (XbSiloQueryData *)exec_data;

	/* optimize pass */
	if (query_data == NULL) {
		g_set_error_literal(error,
				    G_IO_ERROR,
				    G_IO_ERROR_FAILED_HANDLED,
				    "cannot optimize: no silo to query");
		return FALSE;
	}
	return xb_stack_push_bool(stack, query_data->sn->next == 0, error);
}

static gboolean
xb_silo_machine_func_position_cb(XbMachine *self,
				 XbStack *stack,
				 gboolean *result,
				 gpointer user_data,
				 gpointer exec_data,
				 GError **error)
{
	XbSiloQueryData *query_data = (XbSiloQueryData *)exec_data;

	/* optimize pass */
	if (query_data == NULL) {
		g_set_error_literal(error,
				    G_IO_ERROR,
				    G_IO_ERROR_FAILED_HANDLED,
				    "cannot optimize: no silo to query");
		return FALSE;
	}
	return xb_machine_stack_push_integer(self, stack, query_data->position, error);
}

static gboolean
xb_silo_machine_func_search_cb(XbMachine *self,
			       XbStack *stack,
			       gboolean *result,
			       gpointer user_data,
			       gpointer exec_data,
			       GError **error)
{
	XbSilo *silo = XB_SILO(user_data);
	XbSiloPrivate *priv = GET_PRIVATE(silo);
	const gchar *text;
	const gchar *search;
	XbOpcode *head1 = NULL;
	XbOpcode *head2 = NULL;
	g_auto(XbOpcode) op1 = XB_OPCODE_INIT();
	g_auto(XbOpcode) op2 = XB_OPCODE_INIT();

	if (xb_stack_get_size(stack) >= 2) {
		head1 = xb_stack_peek(stack, xb_stack_get_size(stack) - 1);
		head2 = xb_stack_peek(stack, xb_stack_get_size(stack) - 2);
	}
	if (head1 == NULL || !xb_opcode_cmp_str(head1) || head2 == NULL ||
	    !xb_opcode_cmp_str(head2)) {
		g_set_error(error,
			    G_IO_ERROR,
			    G_IO_ERROR_NOT_SUPPORTED,
			    "%s:%s types not supported",
			    (head1 != NULL) ? xb_opcode_kind_to_string(xb_opcode_get_kind(head1))
					    : "(null)",
			    (head2 != NULL) ? xb_opcode_kind_to_string(xb_opcode_get_kind(head2))
					    : "(null)");
		return FALSE;
	}

	if (!xb_machine_stack_pop_two(self, stack, &op1, &op2, error))
		return FALSE;

	/* this cannot be optimized away when constructing the query */
	if (!_xb_opcode_has_flag(&op1, XB_OPCODE_FLAG_TOKENIZED) &&
	    _xb_opcode_get_kind(&op1) == XB_OPCODE_KIND_BOUND_TEXT) {
		xb_machine_opcode_tokenize(self, &op1);
	}
	if (!_xb_opcode_has_flag(&op2, XB_OPCODE_FLAG_TOKENIZED) &&
	    _xb_opcode_get_kind(&op2) == XB_OPCODE_KIND_BOUND_TEXT) {
		xb_machine_opcode_tokenize(self, &op2);
	}

	/* TOKN:TOKN */
	if (xb_opcode_has_flag(&op1, XB_OPCODE_FLAG_TOKENIZED) &&
	    xb_opcode_has_flag(&op2, XB_OPCODE_FLAG_TOKENIZED)) {
		return xb_stack_push_bool(
		    stack,
		    xb_string_searchv(xb_opcode_get_tokens(&op2), xb_opcode_get_tokens(&op1)),
		    error);
	}

	/* this is going to be slow, but correct */
	text = xb_opcode_get_str(&op2);
	search = xb_opcode_get_str(&op1);
	if (text == NULL || search == NULL || text[0] == '\0' || search[0] == '\0')
		return xb_stack_push_bool(stack, FALSE, error);
	if (!g_str_is_ascii(text) || !g_str_is_ascii(search)) {
		if (priv->profile_flags & XB_SILO_PROFILE_FLAG_DEBUG) {
			g_debug("tokenization for [%s:%s] may be slow!", text, search);
		}
		return xb_stack_push_bool(stack, g_str_match_string(search, text, TRUE), error);
	}

	/* TEXT:TEXT */
	return xb_stack_push_bool(stack, xb_string_search(text, search), error);
}

static gboolean
xb_silo_machine_fixup_attr_text_cb(XbMachine *self,
				   XbStack *opcodes,
				   const gchar *text,
				   gboolean *handled,
				   gpointer user_data,
				   GError **error)
{
	/* @foo -> attr(foo) */
	if (g_str_has_prefix(text, "@")) {
		XbOpcode *op1;
		XbOpcode *op2;

		if (!_xb_stack_push_two(opcodes, &op1, &op2, error))
			return FALSE;

		xb_opcode_text_init(op1, text + 1);
		if (!xb_machine_opcode_func_init(self, op2, "attr")) {
			g_set_error_literal(error,
					    G_IO_ERROR,
					    G_IO_ERROR_NOT_SUPPORTED,
					    "no attr opcode");
			xb_stack_pop(opcodes, NULL, NULL);
			xb_stack_pop(opcodes, NULL, NULL);
			return FALSE;
		}

		*handled = TRUE;
		return TRUE;
	}

	/* not us */
	return TRUE;
}

static void
xb_silo_file_monitor_item_free(XbSiloFileMonitorItem *item)
{
	g_file_monitor_cancel(item->file_monitor);
	g_signal_handler_disconnect(item->file_monitor, item->file_monitor_id);
	g_object_unref(item->file_monitor);
	g_slice_free(XbSiloFileMonitorItem, item);
}

static void
xb_silo_get_property(GObject *obj, guint prop_id, GValue *value, GParamSpec *pspec)
{
	XbSilo *self = XB_SILO(obj);
	XbSiloPrivate *priv = GET_PRIVATE(self);
	switch ((XbSiloProperty)prop_id) {
	case PROP_GUID:
		g_value_set_string(value, priv->guid);
		break;
	case PROP_VALID:
		g_value_set_boolean(value, priv->valid);
		break;
	case PROP_ENABLE_NODE_CACHE:
		g_value_set_boolean(value, priv->enable_node_cache);
		break;
	default:
		G_OBJECT_WARN_INVALID_PROPERTY_ID(obj, prop_id, pspec);
		break;
	}
}

static void
xb_silo_set_property(GObject *obj, guint prop_id, const GValue *value, GParamSpec *pspec)
{
	XbSilo *self = XB_SILO(obj);
	XbSiloPrivate *priv = GET_PRIVATE(self);
	switch ((XbSiloProperty)prop_id) {
	case PROP_GUID:
		g_free(priv->guid);
		priv->guid = g_value_dup_string(value);
		silo_notify(self, obj_props[PROP_GUID]);
		break;
	case PROP_VALID:
		/* Read only */
		g_assert_not_reached();
		break;
	case PROP_ENABLE_NODE_CACHE:
		xb_silo_set_enable_node_cache(self, g_value_get_boolean(value));
		break;
	default:
		G_OBJECT_WARN_INVALID_PROPERTY_ID(obj, prop_id, pspec);
		break;
	}
}

static void
xb_silo_init(XbSilo *self)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);

	priv->file_monitors = g_hash_table_new_full(g_file_hash,
						    (GEqualFunc)g_file_equal,
						    g_object_unref,
						    (GDestroyNotify)xb_silo_file_monitor_item_free);
	g_mutex_init(&priv->file_monitors_mutex);

	priv->strtab_tags = g_hash_table_new(g_str_hash, g_str_equal);
	priv->strindex = g_hash_table_new(g_str_hash, g_str_equal);
	priv->profile_str = g_string_new(NULL);
	priv->query_cache = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, g_object_unref);
	g_rw_lock_init(&priv->query_cache_mutex);

	priv->nodes = NULL; /* initialised when first used */
	g_mutex_init(&priv->nodes_mutex);

	priv->context = g_main_context_ref_thread_default();

#ifdef HAVE_LIBSTEMMER
	g_mutex_init(&priv->stemmer_mutex);
#endif

	priv->machine = xb_machine_new();
	xb_machine_add_method(priv->machine, "attr", 1, xb_silo_machine_func_attr_cb, self, NULL);
	xb_machine_add_method(priv->machine, "stem", 1, xb_silo_machine_func_stem_cb, self, NULL);
	xb_machine_add_method(priv->machine, "text", 0, xb_silo_machine_func_text_cb, self, NULL);
	xb_machine_add_method(priv->machine, "tail", 0, xb_silo_machine_func_tail_cb, self, NULL);
	xb_machine_add_method(priv->machine, "first", 0, xb_silo_machine_func_first_cb, self, NULL);
	xb_machine_add_method(priv->machine, "last", 0, xb_silo_machine_func_last_cb, self, NULL);
	xb_machine_add_method(priv->machine,
			      "position",
			      0,
			      xb_silo_machine_func_position_cb,
			      self,
			      NULL);
	xb_machine_add_method(priv->machine,
			      "search",
			      2,
			      xb_silo_machine_func_search_cb,
			      self,
			      NULL);
	xb_machine_add_operator(priv->machine, "~=", "search");
	xb_machine_add_opcode_fixup(priv->machine,
				    "INTE",
				    xb_silo_machine_fixup_position_cb,
				    self,
				    NULL);
	xb_machine_add_opcode_fixup(priv->machine,
				    "TEXT,FUNC:attr",
				    xb_silo_machine_fixup_attr_exists_cb,
				    self,
				    NULL);
	xb_machine_add_opcode_fixup(priv->machine,
				    "FUNC:text,TEXT,FUNC:search",
				    xb_silo_machine_fixup_attr_search_token_cb,
				    self,
				    NULL);
	xb_machine_add_text_handler(priv->machine, xb_silo_machine_fixup_attr_text_cb, self, NULL);
}

static void
xb_silo_finalize(GObject *obj)
{
	XbSilo *self = XB_SILO(obj);
	XbSiloPrivate *priv = GET_PRIVATE(self);

	g_clear_pointer(&priv->nodes, g_hash_table_unref);
	g_mutex_clear(&priv->nodes_mutex);

#ifdef HAVE_LIBSTEMMER
	if (priv->stemmer_ctx != NULL)
		sb_stemmer_delete(priv->stemmer_ctx);
	g_mutex_clear(&priv->stemmer_mutex);
#endif

	g_clear_pointer(&priv->context, g_main_context_unref);

	g_free(priv->guid);
	g_string_free(priv->profile_str, TRUE);
	g_hash_table_unref(priv->query_cache);
	g_rw_lock_clear(&priv->query_cache_mutex);
	g_object_unref(priv->machine);
	g_hash_table_unref(priv->strindex);
	g_hash_table_unref(priv->file_monitors);
	g_mutex_clear(&priv->file_monitors_mutex);
	g_hash_table_unref(priv->strtab_tags);
	if (priv->mmap != NULL)
		g_mapped_file_unref(priv->mmap);
	if (priv->blob != NULL)
		g_bytes_unref(priv->blob);
	G_OBJECT_CLASS(xb_silo_parent_class)->finalize(obj);
}

static void
xb_silo_class_init(XbSiloClass *klass)
{
	GObjectClass *object_class = G_OBJECT_CLASS(klass);
	object_class->finalize = xb_silo_finalize;
	object_class->get_property = xb_silo_get_property;
	object_class->set_property = xb_silo_set_property;

	/**
	 * XbSilo:guid:
	 */
	obj_props[PROP_GUID] =
	    g_param_spec_string("guid",
				NULL,
				NULL,
				NULL,
				G_PARAM_READWRITE | G_PARAM_CONSTRUCT | G_PARAM_STATIC_STRINGS |
				    G_PARAM_EXPLICIT_NOTIFY);

	/**
	 * XbSilo:valid:
	 */
	obj_props[PROP_VALID] = g_param_spec_boolean("valid",
						     NULL,
						     NULL,
						     TRUE,
						     G_PARAM_READABLE | G_PARAM_STATIC_STRINGS |
							 G_PARAM_EXPLICIT_NOTIFY);

	/**
	 * XbSilo:enable-node-cache:
	 *
	 * Whether to cache all #XbNode instances ever constructed in a single
	 * cache in the #XbSilo, so that the same #XbNode instance is always
	 * returned in query results for a given XPath. This is a form of
	 * memoisation, and allows xb_node_get_data() and xb_node_set_data() to
	 * be used.
	 *
	 * This is enabled by default to preserve compatibility with older
	 * versions of libxmlb, but most clients will want to disable it. It
	 * adds a large memory overhead (no #XbNode is ever finalised) but
	 * achieves moderately low hit rates for typical XML parsing workloads
	 * where most nodes are accessed only once or twice as they are
	 * processed and then processing moves on to other nodes.
	 *
	 * This property can only be changed before the #XbSilo is passed
	 * between threads. Changing it is not thread-safe.
	 *
	 * Since: 0.2.0
	 */
	obj_props[PROP_ENABLE_NODE_CACHE] = g_param_spec_boolean(
	    "enable-node-cache",
	    NULL,
	    NULL,
	    TRUE,
	    G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | G_PARAM_EXPLICIT_NOTIFY);

	g_object_class_install_properties(object_class, G_N_ELEMENTS(obj_props), obj_props);
}

/**
 * xb_silo_new:
 *
 * Creates a new silo.
 *
 * Returns: a new #XbSilo
 *
 * Since: 0.1.0
 **/
XbSilo *
xb_silo_new(void)
{
	return g_object_new(XB_TYPE_SILO, NULL);
}

/**
 * xb_silo_lookup_query:
 * @self: an #XbSilo
 * @xpath: an XPath query string
 *
 * Create an #XbQuery from the given @xpath XPath string, or return it from the
 * query cache in the #XbSilo.
 *
 * @xpath must be valid: it is a programmer error if creating the query fails
 * (i.e. if xb_query_new() returns an error).
 *
 * This function is thread-safe.
 *
 * Returns: (transfer full): an #XbQuery representing @xpath
 * Since: 0.3.0
 */
XbQuery *
xb_silo_lookup_query(XbSilo *self, const gchar *xpath)
{
	XbSiloPrivate *priv = GET_PRIVATE(self);
	XbQuery *result;

	g_rw_lock_reader_lock(&priv->query_cache_mutex);
	result = g_hash_table_lookup(priv->query_cache, xpath);
	g_rw_lock_reader_unlock(&priv->query_cache_mutex);

	if (result != NULL) {
		g_object_ref(result);
	} else {
		g_autoptr(XbQuery) query = NULL;

		/* check again with an exclusive lock */
		g_rw_lock_writer_lock(&priv->query_cache_mutex);
		result = g_hash_table_lookup(priv->query_cache, xpath);
		if (result != NULL) {
			g_object_ref(result);
		} else {
			g_autoptr(GError) error_local = NULL;

			query = xb_query_new(self, xpath, &error_local);
			if (query == NULL) {
				/* This should not happen: the caller should
				 * have written a valid query. */
				g_error("Invalid XPath query ‘%s’: %s",
					xpath,
					error_local->message);
				g_rw_lock_writer_unlock(&priv->query_cache_mutex);
				g_assert_not_reached();
				return NULL;
			}

			result = g_object_ref(query);

			g_hash_table_insert(priv->query_cache,
					    g_strdup(xpath),
					    g_steal_pointer(&query));
			g_debug(
			    "Caching query ‘%s’ (%p) in silo %p; query cache now has %u entries",
			    xpath,
			    query,
			    self,
			    g_hash_table_size(priv->query_cache));
		}
		g_rw_lock_writer_unlock(&priv->query_cache_mutex);
	}

	return result;
}