Glib學習（10） 關系和元組 Relations and Tuples

說明文檔網址：http://web.mit.edu/barnowl/share/gtk-doc/html/glib/glib-Relations-and-Tuples.html

關系：類似資料庫，不過目前隻限兩個字段

元組：也類似資料庫，不過隻是關系傳回的每條記錄

結構體：

GTuples

typedef struct {
  guint len;
} GTuples;      

功能函數：

Synopsis

#include <glib.h>


                    GRelation;
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);      

下面是一段例子代碼：

#include <glib.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);      建立新的關系表，fields域的數量，現在這個值必須是2，也就是一個key域，一個value域
    GRelation *relation = g_relation_new(2);

// void g_relation_index(GRelation *relation, gint field, GHashFunc hash_func, GEqualFunc key_equal_func);建立一個域的索引
    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, ...);   插入記錄到關系表中，...的參數必須與域對應
    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);  在域fields中key值對應的元組值
    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, ...);    被給的鍵值如果在關系表中存在則傳回true
    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 field);  在域field中删除所有的key，傳回删除的個數
    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);  傳回所有的key對應的元組，配合g_tuples_index使用取出記錄值
// gpointer g_tuples_index(GTuples *tuples, gint index_, gint field);   從g_relation_select的傳回中取出field中的元組值
// void g_tuples_destroy(GTuples *tuples);  銷毀元組
    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);    銷毀關系表
    g_relation_destroy(relation);
}

int
main(void)
{
    g_printf("BEGIN:\n************************************************************\n");
    test_relation();
    g_printf("\n************************************************************\nDONE\n");
    
    return 0;
}
           

運作結果：

[email protected]:~/16021/glibDemo$ gcc Relations_and_Tuples.c -o Relations_and_Tuples -lglib-2.0
[email protected]:~/16021/glibDemo$ ./Relations_and_Tuples 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
[email protected]:~/16021/glibDemo$ 
           

結語：

關于glib的基本資料類型就講到這裡，其實這裡并不是所有的類型，還有幾個沒有講到，但是那些沒有特殊的要求是不會用到的。

glib其實還有很多的功能，它還帶有核心應用支援，例如線程的實作也可以使用glib完成，那些就是後面有機會再去研究，目前為止可能對我最有用的就是strings和單連結清單。

幾天的更新也算是對我的學習一個記錄和分享，以後有什麼心得體會也會記錄在這裡。

接下來要接觸linux移植，希望能夠将每天的學習分享在這裡，可以和大家一起交流，争取做到中國的stackoverflow。