You may find that adding backward pointers will allow you to do
deletions better.
Cesar Rodas wrote:
project called, PDBM.
The project is DBM like project, with a B+tree, and key -> value data,
similar to BDB, QDBM or GDBM.
For that project I need implement a Pager system.
As I understand a Page is the minimum IO block, and a Data could have more
than a Page but a Page just one Data.. Am I right?
Here I will write you my structures... please correct me if i am wrong...
/*
** This is the Page 0. This is a special Page that have information
** about total of pages, total of allocated but free pages, a pointer to
the
** first and last allocated but free pages.
*/
typedef struct MainPage
{
unsigned char lock;
size_t first_free;
size_t last_free;
size_t total;
size_t free;
} MainPage;
/*
** The pager struct. A page is a chunk of 1024 bytes of data.
** A data cold have more than a page, but a page could have only
** a data. So a Page is the minimun allocated space for a data.
*/
typedef struct Pager
{
/***********************************************/
unsigned char lock; /* 1-Byte, if the Page is locked.
*/
size_t main; /* 4-Byte, a pointer to the begin of the data
*/
size_t next; /* 4-Byte, a pointer to the next Page position
*/
unsigned char file; /* 1-Byte, In what file part if the next Pager
*/
unsigned char data[1024]; /* 1 KB, the content of a Page
*/
/***********************************************/
} Pager;
#define PAGER_LOCKED 0xAF
#define PAGER_UNLOCK 0xFF
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