Glib实例学习（7）关系/元组

1：概述
   关系：类似数据库，不过目前只限两个字段
   元组：也类似数据库，不过只是关系返回的每条记录

2：结构

typedef struct {
  guint len;
} GTuples;

3：原型

GRelation*          g_relation_new                      (gint fields);
void                g_relation_index                    (GRelation *relation,
                                                         gint field,
                                                         GHashFunc hash_func,
                                                         GEqualFunc key_equal_func);
void                g_relation_insert                   (GRelation *relation,
                                                         ...);
gboolean            g_relation_exists                   (GRelation *relation,
                                                         ...);
gint                g_relation_count                    (GRelation *relation,
                                                         gconstpointer key,
                                                         gint field);
GTuples*            g_relation_select                   (GRelation *relation,
                                                         gconstpointer key,
                                                         gint field);
gint                g_relation_delete                   (GRelation *relation,
                                                         gconstpointer key,
                                                         gint field);
void                g_relation_destroy                  (GRelation *relation);

void                g_relation_print                    (GRelation *relation);

                    GTuples;
void                g_tuples_destroy                    (GTuples *tuples);
gpointer            g_tuples_index                      (GTuples *tuples,
                                                         gint index_,
                                                         gint field);

4：实例

#include <stdio.h>
#include <glib.h>
#include <glib/gprintf.h>

struct map {
    int key;
    char *value;
} m[10] = {
    {0,"zero"},
    {1,"one"},
    {2,"two"},
    {3,"three"},
    {4,"four"},
    {5,"five"},
    {6,"six"},
    {7,"seven"},
    {8,"eight"},
    {9,"nine"}
};

typedef struct map map;

#define NUMS    (sizeof(m)/sizeof(m[0]))

static void
test_relation(void)
{
// GRelation* g_relation_new(gint fields);
    GRelation *relation = g_relation_new(2);

// void g_relation_index(GRelation *relation, gint field, GHashFunc hash_func, GEqualFunc key_equal_func);
    g_relation_index(relation, 0, g_int_hash, g_int_equal);
    g_relation_index(relation, 1, g_str_hash, g_str_equal);

// void g_relation_insert(GRelatioin *relation, ...);
    gint i;
    for (i = 0; i < NUMS; i++)
        g_relation_insert(relation, &m[i].key, m[i].value);

// gint g_relation_count(GRelation *relation, gconstpointer key, gint fields);
    g_printf("The '%d' should be exist '%d' times now.\t\tResult: %d.\n",
            m[1].key, 1, g_relation_count(relation, &m[1].key, 0));

// gboolean g_relation_exists(GRelation *relation, ...);
    gboolean b = g_relation_exists(relation, &m[1].key, m[1].value);
    g_printf("The key: '%d' and value: '%s' should be %sfound now.\n",
            m[1].key, m[1].value, b ? "" : "not ");

// gint g_relation_delete(GRelation *relation, gconstpointer key, gint key);
    g_printf("The key: '%d' has been found '%d' times and deleted now.\n",
            m[1].key, g_relation_delete(relation, &m[1].key, 0));

// GTuples* g_relation_select(GRelation *relation, gconstpointer key, gint field);
// gpointer g_tuples_index(GTuples *tuples, gint index_, gint field);
// void g_tuples_destroy(GTuples *tuples);
    g_printf("The all records now:\n");
    for (i = 0; i < NUMS; i++) {
        GTuples *tuples = g_relation_select(relation, m[i].value, 1);
        gint j;
        for (j = 0; j < tuples->len; j++)
            g_printf("Key: %d\t\tValue: %s\n",
                    *(gint *)g_tuples_index(tuples, j, 0),
                    (gchar *)g_tuples_index(tuples, j, 1));
        g_tuples_destroy(tuples);
    }
    g_printf("\n");
// void g_relation_print(GRelation *relation);
//    g_relation_print(relation);

// void g_relation_destroy(GRelation *relation);
    g_relation_destroy(relation);
}

int
main(void)
{
    printf("BEGIN:\n************************************************************\n");
    test_relation();
    printf("\n************************************************************\nDONE\n");

    return 0;
}

5：结果

[xied1@soho use]$ gcc `pkg-config --cflags --libs glib-2.0` -Wall -o relation relation.c
[xied1@soho use]$ ./relation
BEGIN:
************************************************************
The '1' should be exist '1' times now.          Result: 1.
The key: '1' and value: 'one' should be found now.
The key: '1' has been found '1' times and deleted now.
The all records now:
Key: 0       Value: zero
Key: 2       Value: two
Key: 3       Value: three
Key: 4       Value: four
Key: 5       Value: five
Key: 6       Value: six
Key: 7       Value: seven
Key: 8       Value: eight
Key: 9       Value: nine


************************************************************
DONE

6：小结

• 创建： g_relation_new()
• 插入： g_relation_insert()
• 统计： g_relation_count()
• 选择:  g_relation_select()
• 删除： g_relation_delete()
• 销毁： g_relation_destroy()