Introduce QDict

QDict is a high-level dictionary data type that can be used to store a
collection of QObjects. A unique key is associated with only one
QObject.

The following functions are available:

- qdict_new()    Create a new QDict
- qdict_put()    Add a new 'key:object' pair
- qdict_get()    Get the QObject of a given key
- qdict_del()    Delete a 'key:object' pair
- qdict_size()   Return the size of the dictionary
- qdict_haskey() Check if a given 'key' exists

Some high-level helpers to operate on QStrings and QInts objects
are also provided.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Makefile

@@ -91,7 +91,7 @@ obj-y += buffered_file.o migration.o migration-tcp.o net.o qemu-sockets.o
 obj-y += qemu-char.o aio.o net-checksum.o savevm.o
 obj-y += msmouse.o ps2.o
 obj-y += qdev.o qdev-properties.o ssi.o
-obj-y += qint.o qstring.o
+obj-y += qint.o qstring.o qdict.o
 
 obj-$(CONFIG_BRLAPI) += baum.o
 obj-$(CONFIG_WIN32) += tap-win32.o

qdict.c

@@ -0,0 +1,297 @@
+/*
+ * QDict data type.
+ *
+ * Copyright (C) 2009 Red Hat Inc.
+ *
+ * Authors:
+ *  Luiz Capitulino <lcapitulino@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "qint.h"
+#include "qdict.h"
+#include "qstring.h"
+#include "qobject.h"
+#include "sys-queue.h"
+#include "qemu-common.h"
+
+static const QType qdict_type;
+
+/**
+ * qdict_new(): Create a new QDict
+ *
+ * Return strong reference.
+ */
+QDict *qdict_new(void)
+{
+    QDict *qdict;
+
+    qdict = qemu_mallocz(sizeof(*qdict));
+    QOBJECT_INIT(qdict, &qdict_type);
+
+    return qdict;
+}
+
+/**
+ * qobject_to_qdict(): Convert a QObject into a QDict
+ */
+QDict *qobject_to_qdict(const QObject *obj)
+{
+    if (qobject_type(obj) != QTYPE_QDICT)
+        return NULL;
+
+    return container_of(obj, QDict, base);
+}
+
+/**
+ * tdb_hash(): based on the hash agorithm from gdbm, via tdb
+ * (from module-init-tools)
+ */
+static unsigned int tdb_hash(const char *name)
+{
+    unsigned value;	/* Used to compute the hash value.  */
+    unsigned   i;	/* Used to cycle through random values. */
+
+    /* Set the initial value from the key size. */
+    for (value = 0x238F13AF * strlen(name), i=0; name[i]; i++)
+        value = (value + (((const unsigned char *)name)[i] << (i*5 % 24)));
+
+    return (1103515243 * value + 12345);
+}
+
+/**
+ * alloc_entry(): allocate a new QDictEntry
+ */
+static QDictEntry *alloc_entry(const char *key, QObject *value)
+{
+    QDictEntry *entry;
+
+    entry = qemu_mallocz(sizeof(*entry));
+    entry->key = qemu_strdup(key);
+    entry->value = value;
+
+    return entry;
+}
+
+/**
+ * qdict_find(): List lookup function
+ */
+static QDictEntry *qdict_find(const QDict *qdict,
+                              const char *key, unsigned int hash)
+{
+    QDictEntry *entry;
+
+    LIST_FOREACH(entry, &qdict->table[hash], next)
+        if (!strcmp(entry->key, key))
+            return entry;
+
+    return NULL;
+}
+
+/**
+ * qdict_put_obj(): Put a new QObject into the dictionary
+ *
+ * Insert the pair 'key:value' into 'qdict', if 'key' already exists
+ * its 'value' will be replaced.
+ *
+ * This is done by freeing the reference to the stored QObject and
+ * storing the new one in the same entry.
+ *
+ * NOTE: ownership of 'value' is transferred to the QDict
+ */
+void qdict_put_obj(QDict *qdict, const char *key, QObject *value)
+{
+    unsigned int hash;
+    QDictEntry *entry;
+
+    hash = tdb_hash(key) % QDICT_HASH_SIZE;
+    entry = qdict_find(qdict, key, hash);
+    if (entry) {
+        /* replace key's value */
+        qobject_decref(entry->value);
+        entry->value = value;
+    } else {
+        /* allocate a new entry */
+        entry = alloc_entry(key, value);
+        LIST_INSERT_HEAD(&qdict->table[hash], entry, next);
+    }
+
+    qdict->size++;
+}
+
+/**
+ * qdict_get(): Lookup for a given 'key'
+ *
+ * Return a weak reference to the QObject associated with 'key' if
+ * 'key' is present in the dictionary, NULL otherwise.
+ */
+QObject *qdict_get(const QDict *qdict, const char *key)
+{
+    QDictEntry *entry;
+
+    entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_HASH_SIZE);
+    return (entry == NULL ? NULL : entry->value);
+}
+
+/**
+ * qdict_haskey(): Check if 'key' exists
+ *
+ * Return 1 if 'key' exists in the dict, 0 otherwise
+ */
+int qdict_haskey(const QDict *qdict, const char *key)
+{
+    unsigned int hash = tdb_hash(key) % QDICT_HASH_SIZE;
+    return (qdict_find(qdict, key, hash) == NULL ? 0 : 1);
+}
+
+/**
+ * qdict_size(): Return the size of the dictionary
+ */
+size_t qdict_size(const QDict *qdict)
+{
+    return qdict->size;
+}
+
+/**
+ * qdict_get_obj(): Get a QObject of a specific type
+ */
+static QObject *qdict_get_obj(const QDict *qdict, const char *key,
+                              qtype_code type)
+{
+    QObject *obj;
+
+    obj = qdict_get(qdict, key);
+    assert(obj != NULL);
+    assert(qobject_type(obj) == type);
+
+    return obj;
+}
+
+/**
+ * qdict_get_int(): Get an integer mapped by 'key'
+ *
+ * This function assumes that 'key' exists and it stores a
+ * QInt object.
+ *
+ * Return integer mapped by 'key'.
+ */
+int64_t qdict_get_int(const QDict *qdict, const char *key)
+{
+    QObject *obj = qdict_get_obj(qdict, key, QTYPE_QINT);
+    return qint_get_int(qobject_to_qint(obj));
+}
+
+/**
+ * qdict_get_str(): Get a pointer to the stored string mapped
+ * by 'key'
+ *
+ * This function assumes that 'key' exists and it stores a
+ * QString object.
+ *
+ * Return pointer to the string mapped by 'key'.
+ */
+const char *qdict_get_str(const QDict *qdict, const char *key)
+{
+    QObject *obj = qdict_get_obj(qdict, key, QTYPE_QSTRING);
+    return qstring_get_str(qobject_to_qstring(obj));
+}
+
+/**
+ * qdict_get_try_int(): Try to get integer mapped by 'key'
+ *
+ * Return integer mapped by 'key', if it is not present in
+ * the dictionary or if the stored object is not of QInt type
+ * 'err_value' will be returned.
+ */
+int64_t qdict_get_try_int(const QDict *qdict, const char *key,
+                          int64_t err_value)
+{
+    QObject *obj;
+
+    obj = qdict_get(qdict, key);
+    if (!obj || qobject_type(obj) != QTYPE_QINT)
+        return err_value;
+
+    return qint_get_int(qobject_to_qint(obj));
+}
+
+/**
+ * qdict_get_try_str(): Try to get a pointer to the stored string
+ * mapped by 'key'
+ *
+ * Return a pointer to the string mapped by 'key', if it is not present
+ * in the dictionary or if the stored object is not of QString type
+ * NULL will be returned.
+ */
+const char *qdict_get_try_str(const QDict *qdict, const char *key)
+{
+    QObject *obj;
+
+    obj = qdict_get(qdict, key);
+    if (!obj || qobject_type(obj) != QTYPE_QSTRING)
+        return NULL;
+
+    return qstring_get_str(qobject_to_qstring(obj));
+}
+
+/**
+ * qentry_destroy(): Free all the memory allocated by a QDictEntry
+ */
+static void qentry_destroy(QDictEntry *e)
+{
+    assert(e != NULL);
+    assert(e->key != NULL);
+    assert(e->value != NULL);
+
+    qobject_decref(e->value);
+    qemu_free(e->key);
+    qemu_free(e);
+}
+
+/**
+ * qdict_del(): Delete a 'key:value' pair from the dictionary
+ *
+ * This will destroy all data allocated by this entry.
+ */
+void qdict_del(QDict *qdict, const char *key)
+{
+    QDictEntry *entry;
+
+    entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_HASH_SIZE);
+    if (entry) {
+        LIST_REMOVE(entry, next);
+        qentry_destroy(entry);
+        qdict->size--;
+    }
+}
+
+/**
+ * qdict_destroy_obj(): Free all the memory allocated by a QDict
+ */
+static void qdict_destroy_obj(QObject *obj)
+{
+    int i;
+    QDict *qdict;
+
+    assert(obj != NULL);
+    qdict = qobject_to_qdict(obj);
+
+    for (i = 0; i < QDICT_HASH_SIZE; i++) {
+        QDictEntry *entry = LIST_FIRST(&qdict->table[i]);
+        while (entry) {
+            QDictEntry *tmp = LIST_NEXT(entry, next);
+            LIST_REMOVE(entry, next);
+            qentry_destroy(entry);
+            entry = tmp;
+        }
+    }
+
+    qemu_free(qdict);
+}
+
+static const QType qdict_type = {
+    .code = QTYPE_QDICT,
+    .destroy = qdict_destroy_obj,
+};

qdict.h

@@ -0,0 +1,42 @@
+#ifndef QDICT_H
+#define QDICT_H
+
+#include "qobject.h"
+#include "sys-queue.h"
+#include <stdint.h>
+
+#define QDICT_HASH_SIZE 512
+
+typedef struct QDictEntry {
+    char *key;
+    QObject *value;
+    LIST_ENTRY(QDictEntry) next;
+} QDictEntry;
+
+typedef struct QDict {
+    QObject_HEAD;
+    size_t size;
+    LIST_HEAD(,QDictEntry) table[QDICT_HASH_SIZE];
+} QDict;
+
+/* Object API */
+QDict *qdict_new(void);
+size_t qdict_size(const QDict *qdict);
+void qdict_put_obj(QDict *qdict, const char *key, QObject *value);
+void qdict_del(QDict *qdict, const char *key);
+int qdict_haskey(const QDict *qdict, const char *key);
+QObject *qdict_get(const QDict *qdict, const char *key);
+QDict *qobject_to_qdict(const QObject *obj);
+
+/* Helper to qdict_put_obj(), accepts any object */
+#define qdict_put(qdict, key, obj) \
+        qdict_put_obj(qdict, key, QOBJECT(obj))
+
+/* High level helpers */
+int64_t qdict_get_int(const QDict *qdict, const char *key);
+const char *qdict_get_str(const QDict *qdict, const char *key);
+int64_t qdict_get_try_int(const QDict *qdict, const char *key,
+                          int64_t err_value);
+const char *qdict_get_try_str(const QDict *qdict, const char *key);
+
+#endif /* QDICT_H */

qobject.h

@@ -39,6 +39,7 @@ typedef enum {
     QTYPE_NONE,
     QTYPE_QINT,
     QTYPE_QSTRING,
+    QTYPE_QDICT,
 } qtype_code;
 
 struct QObject;