• Co to je obstacks
• Inicializaci
• Alokace
• Uvolnovani
• Makra/funkce
• Zvetsovani objektu
• Super fast rust!
• Status
• Zaver

Co to je obstacks?

Inicializace

1. princlidudit obstacks.h
2. Nadeklarovat nejakou promenou typu struct obstack. POZOR! Struct obstack neni ukazatel na blok pameti, ktery chcete v budoucnosti rozsirovat! Knihovna obstacks ma svuj vlastni memorymanagement mnohem rychlejsi nez klasicke malloc. Specializovany na to, ze budete casto alokovat a uvolnovat. Klasicke malloc, free, realloc je dost pomale. Tohle je rychlejsi. Proste se snazi volani malloc/free minimalizovat. Dela jakousi cache. Struktura obstack ukazuje na prvni chrunk. To je blok pameti-dynamicky alokovany, do ktereho se data ukladaji. Pokud se dojde nakonec, automaticky se naalokuje dalsi.
3. Nadefinavat dve makra:

        #define obstack_chunk_alloc xmalloc
        #define obstack_chunk_free free
   

   Tyto makra pouzivaji obstacky na alokovani/uvolnovani..Jake funkce k tomu pouzijete je na vas.
4. Inicializovat obstack. K tomu slouzi funkce:

      void obstack_init (struct obstack *OBSTACK_PTR)
   

   takze nejak takto:

        static struct obstack myobstack;
        ...
        obstack_init (&myobstack);
   

Alokace v obstacku

void * obstack_alloc (struct obstack *OBSTACK_PTR, size_t SIZE)

     struct obstack string_obstack;

     char *
     copystring (char *string)
     {
       char *s = (char *) obstack_alloc (&string_obstack,
                                         strlen (string) + 1);
       memcpy (s, string, strlen (string));
       return s;
     }

void * obstack_copy (struct obstack *OBSTACK_PTR, void *ADDRESS, size_t SIZE)

void * obstack_copy0 (struct obstack *OBSTACK_PTR, void *ADDRESS, size_t SIZE)

     char *
     obstack_savestring (char *addr, size_t size)
     {
       return obstack_copy0 (&myobstack, addr, size);
     }

Uvolnovani v obstacku

void obstack_free (struct obstack *OBSTACK_PTR, void *OBJECT)

Makra/funkce

     obstack_alloc (get_obstack (), 4);

     char *x;
     void *(*funcp) ();
     /* Use the macro.  */
     x = (char *) obstack_alloc (obptr, size);
     /* Call the function.  */
     x = (char *) (obstack_alloc) (obptr, size);
     /* Take the address of the function.  */
     funcp = obstack_alloc;

Zvetsovani objektu

void obstack_blank (struct obstack *OBSTACK_PTR, size_t SIZE)

Prida neicializovany data..

void obstack_grow (struct obstack *OBSTACK_PTR, void *DATA, size_t SIZE)

Prida data o velikosti SIZE

void obstack_grow0 (struct obstack *OBSTACK_PTR, void *DATA, size_t SIZE)

Prida data o velikosti SIZE a zakonci 0-hodi se pro rust stringu

void obstack_1grow (struct obstack *OBSTACK_PTR, char C)

Prida jenom jeden string-funguje trochu jako stream..

void * obstack_finish (struct obstack *OBSTACK_PTR)

Zarizne objekt a vrati vam ukazatel na nej..a muzete ho normalne pouzivat..

size_t obstack_object_size (struct obstack *OBSTACK_PTR)

Tahle funkce vrati velikost,kam uz objekt narostl

1. inicializace obstacku
2. smycka:
   1. 1)nacti znak
   2. 2)pridej ho pomoci obstack_1grow
3. konec smycky pokud jsme na konci pipe
4. pomoci obstack_1grow muzeme pridat 0 na konec, kdyz delame ze stringama
5. pomoci obstack_finish ziskame ukazatel na nacteny fajl... a muzeme cist dalsi

size_t obstack_room (struct obstack *OBSTACK_PTR)

void obstack_1grow_fast (struct obstack *OBSTACK_PTR, char C)

void obstack_blank_fast (struct obstack *OBSTACK_PTR, size_t SIZE)

     void
     add_string (struct obstack *obstack, char *ptr, size_t len)
     {
       while (len > 0)
         {
           if (obstack_room (obstack) > len)
             {
               /* We have enough room: add everything fast.  */
               while (len-- > 0)
                 obstack_1grow_fast (obstack, *ptr++);
             }
           else
             {
               /* Not enough room. Add one character slowly,
                  which may copy to a new chunk and make room.  */
               obstack_1grow (obstack, *ptr++);
               len--;
             }
         }
     }