[Qemu-devel] [PATCH 01/25] Introduce QEMU dictionary data type

[Luiz Capitulino <lcapitulino@redhat.com>]

A dictionary is a high-level data type used to store a collection of
values, where a unique key is associated with one value. Usually, the
notation 'key:value' is used to denote this relationship.

This commit adds the qemu-dict module, which implements a dictionary
for QEMU and exports the following functions:

- qemu_dict_create()  Create a new dictionary
- qemu_dict_add()     Add a new 'key:value' pair
- qemu_dict_get()     Get the 'value' of a given 'key'
- qemu_dict_exists()  Check if a given 'key' exists
- qemu_dict_del()     Delete a 'key:value' pair
- qemu_dict_destroy() Destroy the dictionary
- qemu_dict_walk()    Walk through the dictionary values
- qemu_dict_size()    Return the size of the dictionary

qemu-dict module uses a chained hash table, whose hash function comes from
module-init-tools program.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 Makefile    |    1 +
 qemu-dict.c |  215 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 qemu-dict.h |   36 ++++++++++
 3 files changed, 252 insertions(+), 0 deletions(-)
 create mode 100644 qemu-dict.c
 create mode 100644 qemu-dict.h

diff --git a/Makefile b/Makefile
index c510ff3..b36786d 100644
--- a/Makefile
+++ b/Makefile
@@ -97,6 +97,7 @@ 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 += qemu-dict.o
 
 obj-$(CONFIG_BRLAPI) += baum.o
 
diff --git a/qemu-dict.c b/qemu-dict.c
new file mode 100644
index 0000000..ad2d6d9
--- /dev/null
+++ b/qemu-dict.c
@@ -0,0 +1,215 @@
+/*
+ * QEMU dictionary 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 "qemu-dict.h"
+#include "qemu-common.h"
+
+/**
+ * qemu_dict_create(): Create a new dictionary data-type
+ */
+struct qemu_dict *qemu_dict_create(void)
+{
+    return qemu_mallocz(sizeof(struct qemu_dict));
+}
+
+/**
+ * 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);
+}
+
+/**
+ * __qemu_dict_get(): Low-level lookup function
+ */
+static void *__qemu_dict_get(const struct qemu_dict *qdict,
+                             const char *key, unsigned int hash)
+{
+    struct qemu_dict_entry *e;
+
+    for (e = qdict->table[hash]; e; e = e->next)
+        if (!strcmp(e->key, key))
+            return e->value;
+    return NULL;
+}
+
+/**
+ * qemu_dict_get(): Lookup for a given 'key'
+ *
+ * return corresponding 'value' or NULL if 'key' doesn't exist.
+ */
+void *qemu_dict_get(const struct qemu_dict *qdict, const char *key)
+{
+    assert(qdict != NULL);
+    assert(key != NULL);
+    return __qemu_dict_get(qdict, key, tdb_hash(key) % QEMU_DICT_HASH_SIZE);
+}
+
+/**
+ * qemu_dict_exists(): Check if 'key' exists
+ *
+ * return 1 if 'key' exists in the dict, 0 otherwise
+ */
+int qemu_dict_exists(const struct qemu_dict *qdict, const char *key)
+{
+    struct qemu_dict_entry *e;
+
+    assert(qdict != NULL);
+    assert(key != NULL);
+
+    for (e = qdict->table[tdb_hash(key) % QEMU_DICT_HASH_SIZE]; e; e = e->next)
+        if (!strcmp(e->key, key))
+            return 1;
+    return 0;
+}
+
+/**
+ * alloc_entry(): allocate a new qemu_dict_entry
+ */
+static struct qemu_dict_entry *alloc_entry(const char *key, void *value)
+{
+    struct qemu_dict_entry *entry;
+
+    entry = qemu_malloc(sizeof(*entry));
+    entry->key = qemu_strdup(key);
+    entry->value = value;
+    entry->next = NULL;
+
+    return entry;
+}
+
+/**
+ * qemu_dict_add(): Add a new value into the dictionary
+ *
+ * Add the pair 'key:value' into qdict. Does nothing if 'key' already
+ * exist.
+ */
+void qemu_dict_add(struct qemu_dict *qdict, const char *key, void *value)
+{
+    unsigned int hash;
+    struct qemu_dict_entry *entry;
+
+    assert(qdict != NULL);
+    assert(key != NULL);
+
+    hash = tdb_hash(key) % QEMU_DICT_HASH_SIZE;
+    if (__qemu_dict_get(qdict, key, hash)) {
+        /* Don't add again if it's already there */
+        return;
+    }
+
+    entry = alloc_entry(key, value);
+    entry->next = qdict->table[hash];
+    qdict->table[hash] = entry;
+    qdict->size++;
+}
+
+/**
+ * qemu_dict_del(): Delete a given 'key' from the dictionary
+ *
+ * This will destroy all data allocated by 'key', except 'value'
+ * which is returned.
+ */
+void *qemu_dict_del(struct qemu_dict *qdict, const char *key)
+{
+    unsigned int hash;
+    struct qemu_dict_entry *e, *prev;
+
+    assert(qdict != NULL);
+    assert(key != NULL);
+
+    prev = NULL;
+    hash = tdb_hash(key) % QEMU_DICT_HASH_SIZE;
+    for (e = qdict->table[hash]; e; e = e->next) {
+        if (!strcmp(e->key, key)) {
+            void *value = e->value;
+            if (!prev)
+                qdict->table[hash] = e->next;
+            else
+                prev->next = e->next;
+            qemu_free(e->key);
+            qemu_free(e);
+            qdict->size--;
+            return value;
+        }
+
+        prev = e;
+    }
+
+    return NULL;
+}
+
+/**
+ * qemu_dict_destroy(): Destroy given 'qdict'
+ *
+ * This will destroy all data allocated by 'qdict', but added
+ * values must be freed by the caller.
+ */
+void qemu_dict_destroy(struct qemu_dict *qdict)
+{
+    int i;
+
+    assert(qdict != NULL);
+
+    for (i = 0; i < QEMU_DICT_HASH_SIZE; i++) {
+        struct qemu_dict_entry *e = qdict->table[i];
+        while (e) {
+            struct qemu_dict_entry *tmp = e->next;
+            qemu_free(e->key);
+            qemu_free(e);
+            e = tmp;
+        }
+    }
+
+    qemu_free(qdict);
+}
+
+/**
+ * qemu_dict_walk(): Walk through dictionary contents
+ *
+ * This function can be used by users to "walk through"
+ * the data stored in the dictionary.
+ *
+ * In order to use this the caller has pass a pointer
+ * to a function with the following signature:
+ *
+ * void walkf(const char *key, void *value);
+ *
+ * Then, when qemu_dict_walk() is called, it will
+ * "walk through" all the dictionary data, passing
+ * each stored value to walkf().
+ */
+void qemu_dict_walk(const struct qemu_dict *qdict,
+                    void (*walkf)(const char *key, void *value))
+{
+    int i;
+
+    assert(qdict != NULL);
+    assert(walkf != NULL);
+
+    for (i = 0; i < QEMU_DICT_HASH_SIZE; i++) {
+        struct qemu_dict_entry *e = qdict->table[i];
+        while (e) {
+            walkf(e->key, e->value);
+            e = e->next;
+        }
+    }
+}
diff --git a/qemu-dict.h b/qemu-dict.h
new file mode 100644
index 0000000..89324db
--- /dev/null
+++ b/qemu-dict.h
@@ -0,0 +1,36 @@
+#ifndef __QEMU_DICT_H__
+#define __QEMU_DICT_H__
+
+#include <stddef.h>
+
+#define QEMU_DICT_HASH_SIZE 512
+
+struct qemu_dict_entry {
+    struct qemu_dict_entry *next;
+    char *key;
+    void *value;
+};
+
+struct qemu_dict {
+    size_t size;
+    struct qemu_dict_entry *table[QEMU_DICT_HASH_SIZE];
+};
+
+/**
+ * qemu_dict_size(): return the size of the dictionary
+ */
+static inline size_t qemu_dict_size(const struct qemu_dict *qdict)
+{
+    return qdict->size;
+}
+
+struct qemu_dict *qemu_dict_create(void);
+void qemu_dict_add(struct qemu_dict *qdict, const char *key, void *value);
+void *qemu_dict_get(const struct qemu_dict *qdict, const char *key);
+int qemu_dict_exists(const struct qemu_dict *qdict, const char *key);
+void *qemu_dict_del(struct qemu_dict *qdict, const char *key);
+void qemu_dict_destroy(struct qemu_dict *qdict);
+void qemu_dict_walk(const struct qemu_dict *qdict,
+                    void (*walkf)(const char *key, void *value));
+
+#endif /* __QEMU_DICT_H__ */
-- 
1.6.4.rc3.12.gdf73a